Metal-Based Nanoparticles as Nanopesticides: Opportunities and Challenges for Sustainable Crop Protection

Abstract

Metal-based nanoparticles (MNPs) are gaining attention as promising components of nanopesticides, offering innovative solutions to enhance agricultural pest management while addressing environmental concerns associated with traditional pesticides. MNPs, such as silver, copper, zinc, nickel, gold, iron, aluminum, and titanium, exhibit unique nanoscale properties. These properties enable the formulation of MNPs for controlled and sustained release, thereby reducing application frequency and minimizing environmental runoff. This controlled release mechanism not only improves pest management efficacy but also reduces risks to non-target organisms and beneficial species, aligning with the principles of sustainable crop protection. This review examines nanopesticides based on their specific targets, such as nanoinsecticide, nanobactericide, nanofungicide, nanonematicide, and nanoviricide. It also explores the mechanisms of action of metal-based nanoparticles, including physical disruption, chemical interactions, and biological processes. Additionally, the review details how MNPs compromise cellular integrity through mechanisms such as membrane damage, DNA disruption, mitochondrial impairment, and protein denaturation. Despite these advantages, significant challenges remain, particularly concerning the environmental impact of MNPs, their long-term effects on soil health and ecosystem dynamics, and potential risks to human safety. Addressing these challenges is crucial for realizing the full potential of MNPs in sustainable agriculture.

1. Introduction

The Food and Agriculture Organization (FAO) reported that, in 2022, global average crop losses due to pests were 40% of total yield or around USD 220 billion [1]. Addressing this issue requires practical strategies. One effective approach involves investing in research and development for pest-resistant crop varieties, which can significantly reduce losses. Additionally, implementing integrated pest management practices can help farmers minimize the impact of pest infestations while promoting sustainable agricultural practices. One of the common strategies is using pesticides. The word “pesticide” is a term for any chemical or biological substance or combination of substances designed to deter, eliminate, or manage pests, or to influence the growth and development of plants [2]. However, traditional pesticides often face limitations, including low selectivity, environmental contamination, and development of resistance among target organisms. In contrast, nanopesticides slowly release active ingredients, making them effective for a longer time and reducing the need for repeated applications [3]. Nanopesticides leverage the unique properties of nanoparticles to provide controlled and targeted pest management. They are designed to protect plants, reduce application wastage, enhance leaf coverage, and decrease the number of formulation components [4]. Additionally, they demonstrate a gradual yet precise release of the desired pesticides to the targeted organisms [5]. These advancements highlight the role of nanopesticides as a critical component in promoting sustainable and ecologically balanced agricultural practices. Even though many studies have looked at how MNPs fight microorganisms, there is limited research specifically on how they can be used as nanopesticides against specific target organisms, as well as regulatory considerations surrounding their use and long-term effects on the environment. This finding highlights a critical research gap that warrants further investigation.

Current research focuses on optimizing nanoparticle formulations, evaluating their ecological safety, and developing customized nanotechnology solutions tailored to particular crops and environmental conditions. These efforts aim to harness the potential of nanopesticides while ensuring their compatibility with sustainable agricultural practices. Additionally, ongoing studies are investigating the interactions between nanopesticides and various environmental conditions, such as soil pH, microbial communities, and water systems, to guarantee their secure and efficient application in diverse agricultural settings. Integrating nanopesticides with sustainable farming practices could significantly decrease dependence on traditional chemical pesticides, thus promoting a more environmentally friendly and resilient agricultural system.

Among the various types of nanopesticide, metal-based nanoparticles (MNPs)—which include silver nanoparticles (AgNPs), copper nanoparticles (CuNPs), zinc nanoparticles (ZnNPs), nickel nanoparticles (NiNPs), aluminum nanoparticles (AlNPs), gold nanoparticles (AuNPs), titanium nanoparticles (TiNPs), and iron nanoparticles (FeNPs)—are some of the most widely used inorganic nanoparticles and offer a promising strategy to combat resistance to regular antibiotics [6]. These MNPs enhance the efficacy of pest control and minimize environmental impact by reducing the quantity of pesticides required. Additionally, these advanced inorganic formulations help active ingredients dissolve better, stay stable longer, release in a controlled way, minimize evaporation, target pests more precisely, reduce harm to other organisms and the environment, and lessen the pesticide’s smell [7,8].

MNPs are increasingly recognized as antimicrobial agents due to their broad inhibitory effects against bacteria, fungi, and viruses [9]. Their integration into nanotechnology-based agricultural chemicals, including nanoherbicides, nanofungicides, and nanoemulsions, has gained significant prominence in disease and pest control by addressing conventional pesticide limitations [10]. They introduce innovative approaches to active ingredient design, optimized formulation, and efficient nanoscale delivery [11].

MNPs exhibit several advantageous properties, such as high surface area-to-volume ratios and strong activity [12]. For instance, AgNPs are known for their strong antimicrobial properties, making them highly effective against a wide range of pathogens [13,14]. Similarly, CuNPs demonstrate promise due to their fungicidal and bactericidal effects, targeting plant pathogens with minimal application volumes and reduced environmental runoff. These properties highlight the potential of MNPs to improve pest management strategies while minimizing environmental impacts.

Several studies have reported the nanoparticle applications of nanopesticides [4], emphasizing their capacity to transform agricultural methods by enhancing crop productivity and supporting sustainable farming. One of the main mechanisms by which MNPs kill pests is through the production of ROS, which damages cellular components such as proteins, lipids, and DNA. MNPs can also penetrate pest cells and disrupt essential biochemical pathways, which enhances their pesticidal efficacy.

MNPs are emerging as powerful agents in the development of nanopesticides, offering an innovative and more sustainable approach to agriculture [15,16]. However, the widespread application of nanoparticle-based technologies in agriculture, including nanopesticides, necessitates a comprehensive understanding of their mechanisms of action, potential environmental impacts, and long-term effects on soil health and ecosystem sustainability. The controlled release and precise targeting of MNPs improve pest control while causing less damage to other organisms, which helps protect helpful species and lessen the environmental effects of farming. However, understanding the long-term effects of metal nanoparticles on soil microbiota, plant health, and ecosystems remains crucial to ensure their safe use. This review explores the potential of MNPs in reshaping pest management, promising a more efficient, eco-friendly approach to sustainable agriculture.

The objectives of this review are to highlight the various advantages of metal-based nanoparticles, classify nanopesticides based on their specific targets, including nanoinsecticides, nanobactericides, nanofungicides, nanonematicides, and nanoviricides, analyze the mechanisms of action of MNPs, and assess the potential challenges associated with MNPs, particularly their environmental impact, long-term effects on soil health and ecosystem dynamics, and potential risks to human safety.

2. Nanopesticide Definition

The European Food Safety Authority (EFSA) defines a pesticide as a substance used to prevent, control, or eliminate harmful organisms or diseases, as well as to protect plants and plant products throughout their production, storage, and transportation processes [17]. Pesticides are chemicals that can be used to manage pests and plant diseases. Conventional pesticide formulations have several limitations, such as elevated organic solvent levels, dust drift, low dispersibility, and persistence in the soil [18]. While agrochemicals are essential for keeping plants safe from various biological threats, their excessive use can lead to the development of resistance in target organisms and can harm non-target species and ecosystems [19].

A nanopesticide refers to the application of nanotechnology in agriculture to protect crops from important insects and pests that cause significant economic losses [20]. Nanopesticides, also referred to as nano plant protection formulations, are an emerging technological innovation that offers several benefits. These include improved effectiveness, extended durability, and a reduced need for active ingredients, which helps minimize environmental pollution [21]. These features ensure improved pest control efficiency over extended periods and protect the encapsulated molecules from degradation under unfavorable environmental conditions, maximizing their effectiveness [20].

Nanoparticles can be functionalized to target specific pests or pathogens, increasing their effectiveness and reducing harm to non-target organisms. As particle size decreases, their surface area increases, which enhances their ability to diffuse into cells [22]. Their small size and high surface area facilitate enhanced interaction with target organisms, including mites, algae, birds, bacteria, fungi, weeds, insects, larvae, snails, nematodes, and viruses. In some cases, they can also prevent the hatching of insect and mite eggs, and are effective against other pests such as fish, rodents, and termites [18]. Further details on specific types of nanopesticide will be discussed in Section 4, Section 5, Section 6, Section 7 and Section 8.

AgNPs also have a role as nanopesticides [23]. Green-synthesized silver nanoparticles are also a potential biopesticide [24]. CuNPs have been investigated for their potential agricultural applications, showing both positive and negative impacts on plants, influenced by the concentration level and exposure time [25]. Additionally, nickel has been evaluated for its antifungal properties against various pathogenic Fusarium in vitro assays [26]. However, reports indicate that NiNPs have toxic effects on Coriandrum sativum L. [27]. This underscores the importance of carefully assessing the effects of metal nanoparticles in agriculture, as potential phytotoxicity can offset their benefits. Further research is necessary to establish optimal conditions for their safe and effective use in crop protection strategies.

3. Efficacy of Metal-Based Nanoparticles as Nanopesticides

Nanoparticles used as pesticides offer several advantages, including enhanced water solubility, greater stability, protection from degradation, release behaviour of active ingredients, precise targeting, reduced dosages, and increased overall effectiveness. However, different MNPs vary in solubility, stability, controlled release, target specificity, and overall efficiency.

3.1. Solubility

A pesticide’s solubility is defined as the maximum amount of pesticide that can dissolve in each solvent under specific conditions of temperature and pressure [28]. Conventional pesticides frequently encounter issues like low solubility, leading to decreased effectiveness [29,30]. Highly soluble pesticides dissolve readily in water and are more likely to leach through the soil or be transported in surface runoff compared to their less soluble counterparts. Nanoparticles with small dimensions can enhance the water solubility of nanopesticides [31]. In particular, MNPs exhibit increased solubility with decreasing particle size, as smaller nanoparticles have a larger surface area available for interaction with solvents.

The solubility of MNPs is a complex process influenced by physicochemical properties and environmental conditions. Understanding these factors is crucial for applications in nanopesticides, where controlled solubility is often required. For example, ZnO is largely insoluble in water and tends to agglomerate upon contact due to water’s high polarity, leading to particle deposition during synthesis [32]. Similarly, dissolution experiments revealed that AgNPs exhibited a higher dissolution rate in acetic acid compared to water [33].

3.2. Stability

The term “nanoparticle stability” broadly refers to the maintenance of specific nanostructural properties, including resistance to aggregation, compositional integrity, crystallinity, morphological stability (shape and size), and surface chemical characteristics [34]. Nanopesticides have been shown to exhibit greater stability and activity in every environmental condition than conventional pesticides [35]. The stability of MNPs, such as AgNPs, has been a key area of research. For instance, AgNPs have revealed that the particle size decreased with increasing pH over a defined time, leading to reduced aggregation in higher pH environments and enhanced particle stability [36]. Additionally, AgNPs have been engineered to exhibit stability against surface oxidation and Ag⁺ ion release. These AgNPs were coated with a hybrid lipid membrane composed of L-phosphatidylcholine (PC), sodium oleate (SOA), and a stoichiometric amount of hexanethiol (HT), resulting in oxidant-resistant AgNPs [37]. Another study on MNPs showed that anthocyanins from berry extracts bind strongly to AuNPs, acting as capping agents that provide electrostatic stabilization and prevent aggregation, even in a 400 mM NaCl solution [38].

3.3. Controlled Release

Nanopesticides typically can release active ingredients in a controlled manner [5]. This controlled release mechanism allows for a consistent concentration of the pesticide over time, improving its efficacy and reducing the risk of overdosing. MNPs release metal ions that are able to enter the cell and disrupt biological processes. Furthermore, controlled release systems can be tailored to respond to specific environmental triggers, such as pH or temperature changes, providing a precision-based approach to pest management. In short, controlled release can be tailored to achieve desired outcomes within specific timeframes [39].

3.4. Target Specificity

In general, nanopesticides can be designed to target specific organisms, which can help protect non-target organisms. Nanoparticles for pesticide nanocarriers can be engineered for targeted delivery to organisms, thereby minimizing collateral damage to beneficial species and reducing the potential for resistance development [29]. In contrast, MNPs kill bacteria in a general way that does not focus on a specific bacterial receptor, which makes it hard for bacteria to develop resistance and allows them to work against a broad range of bacteria [6].

3.5. Efficiency

Because they have a high surface area-to-volume ratio and distinct physicochemical characteristics, nanoinsecticides usually require lower dosages than traditional insecticides [30]. This reduction in dosage not only lowers the application cost but also minimizes the potential for environmental contamination. By delivering more potent formulations at smaller doses, nanoinsecticides represent a shift toward more efficient and sustainable pest management practices. Furthermore, the stronger effect of nanoparticles means that even tiny amounts of chemicals are used in farming. Nanopesticides can be more efficient than conventional pesticides. Nanopesticides can be 31.5% more effective against target organisms than conventional pesticides [40]. Efficiency can be evaluated based on cost and frequency of application.

Specific nanopesticide formulations, including copper oxide (CuO) and graphene oxide–copper (GO–Cu) composites, have demonstrated a reduction in cost per unit of efficacy by as much as 83.4%, indicating significantly enhanced cost-efficiency compared to conventional alternatives [41]. This remarkable decrease in costs not only makes these formulations more accessible to farmers but also promotes the adoption of more sustainable agricultural practices. As a result, the use of nanopesticides could potentially reduce environmental impact while maintaining or even improving crop yields.

Research on copper-based nanopesticides for managing tomato diseases has demonstrated a 4.3-fold enhancement in material efficiency, enabling effective disease control with only approximately 20% of the dosage required for conventional pesticides to achieve comparable efficacy [41]. The way nanopesticides are released in a controlled and steady manner helps them last longer and be more readily available for plants, which means fewer applications are needed and overall pesticide use is greatly reduced [35].

Figure 1 shows the mechanism by which (1) nanopesticides contact plant-associated microbes, including bacteria, viruses, insects, nematodes, and fungi, (2) disrupt their cellular functions by causing chromosomal damage and inducing ROS production, leading to oxidative stress, and (3) result in the microbicidal, virucidal, insecticidal, nematicidal and fungicidal effects that protect plants.

4. MNPs as Nanoinsecticides

An insecticide is a pesticide specifically designed to target and eliminate insect pests. In conventional pesticides, the active ingredients (AIs) are often rapidly degraded due to exposure to sunlight, water, and microbial activity [33]. Nanoparticle insecticides improve pest control by creating stable mixtures that reduce drifting and leaching, allowing for lower chemical use while enhancing effectiveness and longevity [42]. Within this framework, nanoinsecticides represent a specialized category of nanopesticides engineered to improve the delivery, stability, and efficacy of active ingredients, offering a more efficient and environmentally sustainable strategy for insect pest management [30].

Nanoinsecticides can be applied using various methods, including foliar sprays, seed treatments, and soil amendments. The foliar application involves the direct spraying of nanoinsecticides onto plant foliage, effectively targeting pests such as aphids, beetles, and caterpillars. Seed treatments entail coating seeds with nanoinsecticides, protecting germinating seedlings against early-stage pest attacks. Soil amendments incorporate nanoinsecticides into the soil, offering control over root-feeding pests, such as nematodes and grubs, by targeting them in their subterranean habitat.

Several studies have demonstrated the potential of MNPs in enhancing insecticidal efficacy and targeting various pests. For example, ZnONPs were added to thiamethoxam to make it more effective against Spodoptera litura [43]. Similarly, AgNPs synthesized by Suaeda maritima have demonstrated efficacy against Spodoptera litura [44]. Biosynthesized AgNPs from isolated actinomycetes strains have shown their impact on the black cutworm, Agrotis ipsilon [45]. Additionally, AgNPs have been reported to induce oxidative stress in larval guts of Spodoptera litura, with enhanced levels of antioxidant enzymes [46].

In the case of Drosophila melanogaster, AgNPs have been found to cause several physiological effects, including loss of cuticular melanin pigments, impaired vertical flight ability, reduced activity of certain enzymes that need cooper, such as tyrosinase and Cu-Zn superoxide dismutase, and the way nano-Ag interacts with copper transport proteins leading to buildup of copper, which mimics a lack of copper in the body [47].

The AgNPs synthesized from Ficus religiosa and Ficus benghalensis showed a significantly strong impact on the growth and development of Helicoverpa armigera larvae. By inhibiting midgut proteases, which are essential for digestion and survival, they exhibited insecticidal properties [48]. The study of iron nanoparticles also assessed the effectiveness of synthesized α-Fe₂O₃ nanoparticles in causing mortality in the green peach aphid (Myzus persicae) [49].

The toxicity of AgNPs was studied using Drosophila as a model organism. Long-term exposure to low levels of AgNPs (0.1 and 1 µg mL⁻¹) was found to significantly reduce lifespan, whereas silver ions did not show the same effect. Using Drosophila genetics, researchers found a GAL4 enhancer trap line named M95 that showed more GAL4 activity after eating AgNPs at very low concentrations, 0.1 µg mL⁻¹. Notably, M95 flies showed greater tolerance to both AgNP exposure and dry starvation, likely due to the upregulation of the JNK signaling pathway. These results indicate that M95 could be an important indicator or sensitive biomarker for AgNP exposure and support the use of Drosophila as a valuable model for assessing the potential health impacts of AgNPs [50]. Another study demonstrates that AgNPs triggered several physiological and behavioral effects in Drosophila melanogaster. Exposure to AgNPs results in the loss of melanin cuticular pigmentation, a key indicator of disrupted melanin synthesis, reduced vertical flight ability and impaired locomotor activity. Biochemical analysis reveals that this activity accompanies decline in the activity of copper-dependent enzymes, such as tyrosinase and Cu-Zn superoxide dismutase (SOD), indicating a problem with copper balance in the body. The suggested processes involve AgNPs attaching copper transporter proteins on cell membrane, which causes copper to be trapped and creates a situation like that of lack of copper in the organism [47].

In addition to their insecticidal properties, numerous investigations have highlighted the antifungal activity of MNPs against plant diseases caused by insect vectors (

Table 1. Research on metal-based nanoparticles against insects.

NPs Types	Synthesis Method	Insect	Host Plant/Target	Condition of Experiment	References
AgNPs	GS (Peganum harmala L.)	Trogoderma granarium (Khapra beetle)	Stored grains	Petri dish	[51]
AgNPs	GS (Suaeda maritima)	Spodoptera litura (Tobacco cutworm)	Nicotiana tabaccum	Leaf disk assay	[44]
AgNPs	CS	Tribolium castaneum (Red flour beetle)	Wheat	Jar	[52]
AgNPs	GS (Moringa oleifera F.)	Sitophilus oryzae L. (Rice weevil)	Sorghum	Laboratory	[53]
AgNPs	Commercial	Spodoptera litura (Asian armyworm) Achaea janata (Castor semi looper)	Ricinus communis L.	Laboratory	[46]
AgNPs	GS (Urtica dioica)	Drosophila melanogaster (Fruit flies)	Common fruits	Laboratory	[54]
Silica (SiO)	Commercial	Aphis craccivora (Cowpea aphid) Liriomyza trifolii (Serpentine leafminer) Spodoptera littoralis (Cotton leafworm)	Faba bean Soybean	Field	[55]
ZnONPs	Commercial	Spodoptera frugiperda (Fall armyworm)	Rice	Laboratory	[56]
TiO2NPs	Commercial	Spodoptera littoralis (Cotton leaf worm)	Cotton, tomatoes, cabbage, squash, etc	Laboratory	[57]
TiO2NPs	CS	Bombyx mori (Silkworm)	Mulberry		[58]
CuONPs	CS	Spodoptera frugiperda (Fall armyworm)	Maize, rice, crabgrass, sorghum, cotton, and vegetable crops	Container	[59]
CuNPs	GS (Pseudomonas fluorescens)	Tribolium castaneum (Red flour beetle)	Wheat	Laboratory	[60]
Al2O3NPs	CS	Sitophilus oryzae L. (Rice weevil)	Wheat	Laboratory	[61]
Fe3O4NPs	CS	Drosophila melanogaster (Fruit fly)	Common fruits	Laboratory	[62]

GS: green synthesis and CS: chemical synthesis.

). In the table below, it is evident that many researchers have used AgNPs in their studies. This is due to AgNPs’ broad-spectrum insecticidal activity, facile and cost-effective synthesis methods, and relatively low environmental persistence when compared to conventional chemical pesticides.

5. MNPs as Nanobactericides

Nanobactericides represent a cutting-edge advancement in antimicrobial technology, leveraging nanomaterials’ unique properties to effectively combat bacterial pathogens. Nanoparticles, especially MNPs, are the core components of nanobactericides. These particles exhibit remarkable antibacterial properties due to their high surface area-to-volume ratio, enhanced reactivity, and ability to penetrate bacterial cells.

Nanobactericides have emerged as a promising tool for managing bacterial plant diseases, improving crop protection, and ensuring food security. By targeting harmful pathogens with precision, they minimize the need for traditional chemical treatments, reducing environmental impact and addressing the growing issue of antimicrobial resistance. However, the application of nanobactericides also poses challenges, including potential toxicity to non-target organisms, environmental persistence, and production scalability. To fully harness their potential, ongoing research focuses on developing eco-friendly and biodegradable nanomaterials, optimizing formulations, and assessing their long-term impacts on ecosystems.

MgONPs are widely studied for their antimicrobial potential, particularly as alternatives for treating drug-resistant pathogens. MgONPs were tested, both alone and with agents like nisin and ZnONps, against Escherichia coli and Salmonella species. The results showed that MgONPs were highly effective, achieving a significant reduction of 7 logs in bacterial counts [63]. AuNPs with bactericidal properties were synthesized using an aqueous extract derived from watermelon rind. These nanoparticles exhibited notable antimicrobial activity against foodborne pathogens. Additionally, they demonstrated significant antioxidant capabilities, including DPPH radical scavenging, ABTS scavenging, nitric oxide scavenging, and reducing power activities [64].

Nanobactericides mark a significant leap forward in sustainable antimicrobial strategies, offering versatile applications across agriculture, medicine, and environmental management. Their development and deployment could transform pathogen control and contribute to more resilient agricultural systems and healthier ecosystems. A nanobactericide is a nanoscale material or formulation designed to combat bacterial pathogens effectively. These materials, often metallic nanoparticles, are engineered to leverage their unique physicochemical properties to disrupt bacterial cells, inhibit their growth, or eliminate them. Several investigators have reported their antifungal activity on metal nanoparticles against plant disease caused by bacteria (Table 2).

For example, AgNPs inhibit ATP production and DNA replication, damage the bacterial cell membrane directly, increase oxidative stress, and lead to cell death. In contrast, ZnONPs stimulate the production of reactive oxygen species and the release of zinc ions (Zn²⁺). Finally, CuONPs damage the bacterial cell membrane, enter cells, and modify their enzymatic function, all of which lead to their death. AgNPs attach to the cell wall and cytoplasmic membrane of microorganisms, causing structural disruption. They penetrate the cells, interact with intracellular components and biomolecules, and stimulate the production of ROS and free radicals, leading to cellular damage [65].

Subsequently, nanoparticles (NPs) engage with key bacterial cellular components including DNA, lysosomes, ribosomes, and enzymes, resulting in various cellular disruptions. These disruptions can lead to problems like oxidative stress, changes in cell structure, more permeable membranes, disturbances in electrolyte balance, inhibition of enzymatic activity, protein inactivation, and modulation of gene expression. The most identified antibacterial mechanisms in current research are oxidative stress induction, release of metal ions, and nonoxidative pathways [66].

Due to their significant therapeutic potential, it is becoming more important to understand how nanoparticle (NP) complexes affect bacterial survival. While one advantage of NP drug delivery systems is their ability to target specific infection sites, it is also crucial to understand how they affect bacterial processes. It is important to study how they affect important functions, such as how easily substances can enter the cell wall, how well the bacteria can pump out unwanted materials, the creation of harmful substances, and how they stop vital processes for growth and reproduction [66]. Table 2 shows a list of research activities on MNPs for nanobactericides. Compared to other synthesis approaches—such as green (biological), chemical, or physical methods—commercially produced nanoparticles generally exhibit more consistent size and improved stability. This is largely due to the use of standardized procedures, sophisticated equipment, and rigorous purification techniques that reduce variability between production batches.

Table 2. Research on metal-based nanoparticles against bacteria.

Type of NPs	Synthesis Method	Size (nm)	Concentration	Plant Disease	Causal Organism	Host Plant	Application Condition	References
AgNPs	GS (Bacillus cereus)	18–39	100 mg mL−1	Bacterial leaf blight	Xanthomonas oryzae	Oryza sativa L.	In vitro and in vivo	[67]
AgNPs	GS	24.5	10 μg mL−1	Bacterial wilt	Ralstonia solanacearum	-	In vitro	[68]
AgNPs	GS (Zea mays)	25	100 ppm	Bacterial wilt	Ralstonia solanacearum	-	In vitro	[69]
AgNPs	GS	11.12	1.2 μg mL−1	Tobacco wildfire	Pseudomonas syringae	Nicotiana benthamiana	In vitro and in vivo	[70]
AgNPs	GS (F. oxysporum)	16–27	100 ppm	Soft rot	Pectobacterium carotovorum	Beta vulgaris L.	In vivo	[71]
AgNPs	CS	2, 22, 29	6.25 μg mL−1	Black rot	Xanthomonas campestris	Brassica oleracea	In vitro	[72]
CuNPs	CS	5–10	300 ppm	Bacterial leaf spot	Xanthomonas campestris	Solanum lycopersicum	In vitro and in vivo	[73]
CuNPs	CS	18–33	≥2 μg mL−1	Bacterial leaf blight	Xanthomonas oryzae	Oryza sativa	In vitro	[74]
CuNPs	GS (Shewanella sp.)	30–190	42 ppm	Wilt disease	Ralstonia solanacearum	-	In vitro	[75]
ZnONPs	Commercial	≤40	0.1 mg mL–1	Bacterial leaf spot Bacterial blight	Xanthomonas axonopodis Pseudomonas syringae	Lens culinaris Medik.	In vivo	[76]
MgONPs	Commercial	20–200	0.05–0.1%	Bacterial wilt	Ralstonia solanacearum	Solanum lycopersicum	In vitro and in vivo	[77]
MgONPs	Commercial	50–100	250 µg mL−1	Tobacco bacterial wilt	Ralstonia solanacearum	Nicotiana tabacum L.	In vitro and in vivo	[78]
MgONPs	Commercial	20	200 µg mL−1	Bacterial spot	Xanthomonas perforans	Solanum lycopersicum	In vitro and in vivo	[79]
Fe2O3NPs	GS (Skimma laureola)	56–350	6 mg mL−1	Bacterial wilt	Ralstonia solanacearum	Tomato	In vitro and in vivo	[80]

GS: green synthesis, CS: chemical synthesis.

Table 2. Research on metal-based nanoparticles against bacteria.

Type of NPs	Synthesis Method	Size (nm)	Concentration	Plant Disease	Causal Organism	Host Plant	Application Condition	References
AgNPs	GS (Bacillus cereus)	18–39	100 mg mL−1	Bacterial leaf blight	Xanthomonas oryzae	Oryza sativa L.	In vitro and in vivo	[67]
AgNPs	GS	24.5	10 μg mL−1	Bacterial wilt	Ralstonia solanacearum	-	In vitro	[68]
AgNPs	GS (Zea mays)	25	100 ppm	Bacterial wilt	Ralstonia solanacearum	-	In vitro	[69]
AgNPs	GS	11.12	1.2 μg mL−1	Tobacco wildfire	Pseudomonas syringae	Nicotiana benthamiana	In vitro and in vivo	[70]
AgNPs	GS (F. oxysporum)	16–27	100 ppm	Soft rot	Pectobacterium carotovorum	Beta vulgaris L.	In vivo	[71]
AgNPs	CS	2, 22, 29	6.25 μg mL−1	Black rot	Xanthomonas campestris	Brassica oleracea	In vitro	[72]
CuNPs	CS	5–10	300 ppm	Bacterial leaf spot	Xanthomonas campestris	Solanum lycopersicum	In vitro and in vivo	[73]
CuNPs	CS	18–33	≥2 μg mL−1	Bacterial leaf blight	Xanthomonas oryzae	Oryza sativa	In vitro	[74]
CuNPs	GS (Shewanella sp.)	30–190	42 ppm	Wilt disease	Ralstonia solanacearum	-	In vitro	[75]
ZnONPs	Commercial	≤40	0.1 mg mL–1	Bacterial leaf spot Bacterial blight	Xanthomonas axonopodis Pseudomonas syringae	Lens culinaris Medik.	In vivo	[76]
MgONPs	Commercial	20–200	0.05–0.1%	Bacterial wilt	Ralstonia solanacearum	Solanum lycopersicum	In vitro and in vivo	[77]
MgONPs	Commercial	50–100	250 µg mL−1	Tobacco bacterial wilt	Ralstonia solanacearum	Nicotiana tabacum L.	In vitro and in vivo	[78]
MgONPs	Commercial	20	200 µg mL−1	Bacterial spot	Xanthomonas perforans	Solanum lycopersicum	In vitro and in vivo	[79]
Fe2O3NPs	GS (Skimma laureola)	56–350	6 mg mL−1	Bacterial wilt	Ralstonia solanacearum	Tomato	In vitro and in vivo	[80]

GS: green synthesis, CS: chemical synthesis.

6. MNPs as Nanofungicides

Although current antifungal drugs help manage fungal infections, numerous challenges persist. Many antifungal medications are toxic, and fungi are increasingly developing resistance. The growing issue of antifungal resistance is particularly alarming, as it will reduce the effectiveness of future treatments, similar to the current situation with antibacterial drugs. The number of reports on drug-resistant pathogenic fungi has surged in recent decades. Resistance to commonly used antifungal agents has made treating fungal infections much more difficult [81].

Nanofungicide refers to nanomaterials for use in managing plant disease caused by fungi. Nanoparticles enhance the ability of fungicidal compounds by improving their ability to penetrate plant tissues or fungal cells. Functionalized nanoparticles can be designed to target specific fungal pathogens. Surface modifications with ligands or peptides that recognize fungal components of the cell wall enable targeted delivery of fungicidal agents and minimize off-target effects.

The fungicidal properties of specific metal oxides have been quantitatively evaluated, demonstrating substantial inhibition of the growth of various fungal pathogens [82]. Metal and metal-oxide nanoparticles have been recognized for their ability to enhance plant growth and health through various mechanisms, including activation of plant defense systems, and effective control of plant diseases [83]. Metal oxide nanoparticles function as fungicides by generating oxidative stress, compromising cellular membranes and organelles, and suppressing fungal growth, as well as spore germination [84,85].

Research on CuONPs indicates that they induce fungal cell death by disrupting the cell wall, penetrating the fungal cells, and interfering with vital intracellular processes [85]. CuNPs stick tightly to the walls of microbial cells, creating a layer of copper oxide that starts several reactions, which helps stop microorganisms from becoming resistant [86]. AgNPs cause bacterial cell membrane damage, leading to cell death [87]. AgNPs and simvastatin have been tested for antifungal activity against Aspergillus flavus, Aspergillus nomius, Aspergillus parasiticus, Aspergillus ochraceus, and Aspergillus melleus. AgNPs showed greater antifungal effects than simvastatin, particularly in inhibiting spore germination [88]. Additionally, Cobalt (CoFe₂O₄) and nickel ferrite nanoparticles (NiFe₂O₄) have demonstrated fungicidal activity that has been successfully tested against plant pathogenic fungi such as Fusarium oxysporum, Colletotricum gloesporoides, and Dematophora necatrix [89]. In short, MNPs combat microbial resistance by targeting various cellular structures and disrupting multiple vital functions within the microorganisms.

MgONPs were evaluated for the first time against soilborne Phytophthora nicotianae and Thielaviopsis basicola in both laboratory and greenhouse [90]. AgNPs have demonstrated antifungal activity against plant pathogenic fungi Fusarium oxysporum, Fusarium graminearum, Phoma glomerata, and Aspergillus niger [91]. Similarly, AgNPs have been reported against other fungal pathogens, such as Drechslera halodes, Drechslera tetramera, Macrophomina phaseolina, Alternaria alternata, Curvularia australiensis [92].

Several investigators have reported their antifungal activity on MNPs against plant disease caused by fungi, as summarized in (

Table 3. Research on metal-based nanoparticles against plant disease caused by fungi.

NPs Type	Synthesis Method	Size (nm)	Concentration	Plant Disease	Fungal Phytopathogens	Host Plant Species	Application Method	References
AgNPs	PS	5–15	10 and 50 ppm	Foot rot	Phytophthora capsica	Piper ningrum L.	In vitro and in vivo	[93]
AgNPs	GS (Ocimum kilimandscharicum)	-	75 and 100 ppm	Fusarium wilt Anthracnose	Fusarium oxysporum Colletotrichum gloeosporioides	-	In vitro	[94]
AgNPs	GS (P. duclauxii)	3–32	150–200 ppm	Leaf spot	Bipolaris sorghicola	Sorghum bicolor	In vitro	[95]
AgNPs	GS (Zea mays)	25	100 ppm	Blight and rot	Phomopsis vexans	-	In vitro	[69]
AgNPs	GS (Azadirachta indica)	22–30	50 ppm	Early blight	Alternaria solani	Solanum lycopersicum L.	In vitro and in vivo	[96]
AgNPs	GS (Avena fatua)	5–25	40 ppm	Fusarium wilt	Fusarium oxysporum	-	In vitro	[97]
AgNPs	GS (Geranium)	38.5	150 mg L−1	Fusarium wilt	Fusarium oxysporum	-	In vitro	[98]
CuNPs	CS	11–14		Tomato late blight	Phytophthora infestans	Lycopersicon esculentum	In the vivo	[99]
CuNPs	GS (Jasmine)	-		-	Corynespora dendranthema	Dendranthema grandiflora	In vitro	[100]
CH@CuONPs	CS	29.98	100 and 250 mg L−1	Tomato gray mold	Botrytis cinerea	Solanum lycopersicum Mill.	In vitro and in vivo	[101]
ZnONPs	GS (Trachyspermum ammi)	15–20	1200 ppm	Cercospora leaf spot	Cercospora canesens	Vigna radiata L.	In vivo & in vitro	[102]
ZnONPs	GS (Penicillium expansum)	3.50–67.30	500 µg mL−1	Fusarium wilt	Fusarium oxysporum	Solanum melongena	In vivo	[103]
NiNPs	PS (Plasma thermal)	<100	50 and 100 ppm	Fusarium disease	Fusarium solani Fusarium equiseti Fusariumn merismoides Fusarium proliferatum Fusarium fujikuroi	-	In vitro	[26]
ZnONPs	Commercial	≤40	0.1 mg mL–1	Alternaria blight Fusarium wilt	Alternaria alternata Fusarium oxysporum	Lens culinaris Medik.	In vivo	[76]
TiO2NPs	GS (Moringa oleifera)	10–100	40 mg L−1	Yellow stripe rust	Puccinia striiformis	Triticum aestivum L.	In vivo	[104]
TiO2NPs	GS (Trianthema portulacastrum) GS (Chenopodium quinoa)	6–8	75 μg mL−1	Fungus disease	Ustilago tritici	Triticum aestivum L.		[105]
MgONPs	GS (Carica papaya)	100	500 µg mL−1	Soilborne	Phytophthora nicotianae Thielaviopsis basicola	Nicotiana tabacum L.	In vitro and in vivo	[90]
Fe2O3NPs	GS (thyme)	48	200	Gray or blue mold	Botrytis cinerea	Fragaria ananassa	In vitro and in vivo	[106]
Fe2O3NPs	CS	5 ± 1.0	20 µg mL−1	Fusarium wilt	Fusarium oxysporum	Solanum melongena	In vivo	[107]

GS: green synthesis, PS: physical synthesis, CS: chemical synthesis.

) by nanoparticle type, such as AgNPs, CuNPs, and FeNPs. Recently, researchers have increasingly adopted green or biological synthesis methods for nanoparticle production due to their eco-friendly and sustainable nature.

7. MNPs as Nanonematicides

Plant-parasitic nematodes are commonly termed the “unseen enemies” of crops due to their below-ground existence and difficulty in detecting their presence [108]. Various strategies are employed to manage nematode infestations in agriculture, including crop rotation, trap cropping, and the use of chemical treatments. Crop rotation and trap cropping involve planting non-host or decoy crops to reduce nematode populations, with trap crops often destroyed afterward to eliminate the nematodes they attract [109].

Numerous examples are derived from root-knot nematodes (Meloidogyne spp.) and cyst nematodes (Globodera and Heterodera spp.), as these groups represent some of the most extensively studied plant-parasitic nematodes [110]. The sedentary endoparasitic nematodes Meloidogyne spp., Heterodera spp., and Globodera spp. are among the most destructive pathogens of crops, parasitizing a wide range of economically important plants, from grasses to trees [111]. The genus Meloidogyne, for example, Meloidogyne incognita (commonly known as the root-knot nematode), is especially problematic [76,112,113,114].

Chemical control methods remain a common approach to managing nematodes, but their use requires caution and should be integrated with other methods to minimize environmental harm and reduce the risk of resistance development [115]. In recent years, the use of nanonematicides, which are nanoparticles designed to target nematode-induced plant diseases, has emerged as a promising alternative, offering targeted and efficient pest management solutions. A study tested CuNPs, FeNPs, and ZnNPs synthesized from Tridax procumbens L. extract against Meloidogyne incognita infections in cabbage plants. At 100 ppm concentration, these nanoparticles effectively reduced the nematode population, egg count, and gall index in 200 cc of soil. Among all treatments, cabbage plants treated with CuNPs had significantly higher yields compared to those treated with other nanoparticles or left untreated [116].

Nanonematicides have several applications, including nematode suppression, seed treatment, and soil treatment. Research demonstrated that ZnONPs effectively reduce populations of nematodes like Meloidogyne incognita [117]. In seed treatment, MNPs can be applied as seed coatings to protect germinating seeds from nematode infestations. Another application of nanonematicides is in soil treatment, which targets nematodes while preserving beneficial soil microbes, thereby improving soil health. For instance, AgNPs of 1 nm (AgNP1) and 28 nm with PVP coating (AgNP28) showed anthelmintic activity against Caenorhabditis elegans. Both AgNP1 and AgNP28 caused dose-dependent effects and mortality. AgNP28 was more toxic than AgNP1, as indicated by its LC₅₀ value, which was lower [118].

The greenhouse antinematicidal experiment was conducted using the extraction of eggs from nematode-infected tomato roots. Second-stage juveniles were collected daily and used within five days of collection. Eggplants (Solanum melongena) were grown in plastic pots under controlled conditions. The treatment involved the application of green silver nanoparticles. Nematode reproduction parameters assessed included the number of galls, females, egg masses per root system, and juveniles per 250 g of soil. Plant growth parameters measured were shoot length (cm), shoot biomass (g), root length (cm), root biomass (g), and leaves number per plant [119].

Examples of MNPs with nematicidal activity are summarized in

Table 4. Research of metal-based nanoparticles against nematodes.

Nanoparticles	Synthesis Method	Size (nm)	Host Plant	Nematode	Condition of Experiment	References
AgNPs	CS	140 ± 10	-	Caenorhabditis elegans	In vitro	[121]
AgNPs	CS	20–30	-	Caenorhabditis elegans	Well plates	[122]
AgNPs	GS (Conyza dioscoridis)	30–100	Solanum melongena L.	Meloidogyne incognita	Greenhouse	[123]
AgNPs	GS (Nostoc sp.)	6.4–16	Faba bean	Meloidogyne javanica	Greenhouse	[124]
AgNPs	CS	~20 nm	Oryza sativa	Meloidogyne graminicola	Lab, glass house	[125]
AgNPs	GS (P. lilacinus)	50	Brinjal	Meloidogyne incognita	Petri dish	[112]
AgNPs	GS (Algae)	<40	Tomato	Meloidogyne incognita	Petri dish, pots	[113]
AgNPs	GS (Glycyrrhiza glabra)	9.6–34.74	-	Meloidogyne incognita	Tissue culture plate	[126]
AgNPs	GS (Glycine max)	-	Soybean	Pratylenchus brachyurus	In vitro	[127]
CuNPs	CS	100	-	Meloidogyne Incognita	In vitro	[128]
CuNPs	GS (O. aegyptiaca)	<50	-	Meloidogyne incognita	In vitro	[129]
CuNPs	GS (Bacillus subtilis)	15–45	Cucumber	Meloidogyne incognita	Petri dish	[114]
ZnONPs	Commercial	15–140	-	Panagrellus redivivus	In vitro	[130]
ZnONPs	Commercial	≤40	Lens culinaris Medik.	Meloidogyne incognita	Pot	[76]
ZnONPs	GS (Salix alba)	-	Tomato	Meloidogyne incognita	In vitro	[131]
TiO2NPs	GS (Syzygium cumini)	12–30	Carrot	Meloidogyne incognita	In vitro and in pot	[132]
ZnO, Al2O3 and TiO2	Commercial	20, 60, 50	-	Caenorhabditis elegans	In vitro	[133]

GS: green synthesis, CS: chemical synthesis.

. AgNPs have become the most common and excellent nanopesticides against nematodes. In biological systems, Ag stands out among the noble metals due to its high reactivity and ability to disrupt cell membranes. This makes them effective at damaging or killing harmful microorganisms [120].

8. MNPs as Nanoviricides

Nanoparticles, due to their unique physicochemical properties and nanoscale size, have been found to interact with viruses. Researchers have demonstrated that nanoparticles reduce viral infectivity and exhibit virucidal activity against a wide range of viruses [134]. Nanoviricides are a cutting-edge class of nanotechnology-based antiviral agents designed to neutralize viruses with high specificity and efficacy. Phyto viruses induce physiological, molecular, and biochemical changes in host plants, leading to symptoms such as stunted growth, chlorosis, leaf and fruit distortion, and mottling [135]. Once a virus binds to a nanoviricide, it is trapped and inactive, preventing it from infecting host cells. This novel mechanism is innovative in combating viral infections, particularly those resistant to traditional antiviral drugs. Additionally, the use of MNPs in plants to combat viruses has been found to enhance the biosynthesis of growth regulators, such as cytokinin, abscisic acid, and brassinosteroid, thereby activating the plant’s antioxidant defense system [135].

The application of nanoviricides serves as an innovative approach to disease management in crops. Nanoviricides can be directly sprayed onto plants to target viral infections, reducing dependence on conventional chemical treatments. Alternatively, they can be employed as a preventative measure through seed coating, where the coated seeds protect emerging seedlings against early-stage viral infections. Nanoparticles may exhibit virucidal activity by generating reactive oxygen species that induce protein oxidation, disrupting viral binding, fusion, infectivity, and replication, while also interfering with viral surface glycoproteins to prevent host cell recognition [134].

A study evaluated AgNPs synthesized by B. pumilus (NPs-1), B. persicus (NPs-2), and B. licheniformis (NPs-3) against bean yellow mosaic virus (BYMV). The AgNPs were non-toxic to healthy plants, indicating suitability for agricultural use. Post-infection treatment (24 h after inoculation) was the most effective, especially with NPs-3, significantly reducing virus levels and symptoms. Pre-infection treatment showed no effect, while simultaneous application led to moderate symptom reduction. These results highlight the importance of application timing in antiviral efficacy [136]. Numerous studies have demonstrated that MNPs exhibit virucidal properties, effectively inactivating viruses and preventing the progression of plant diseases caused by viral pathogens (

Table 5. Research on metal-based nanoparticles against plant disease caused by viruses.

NPs Type	Synthesis Method	Size (nm)	Concentration	Plant Disease	Causal Organisms	Host Plant Species	Application Method	References
AgNPs	GS (Bacillus spp.)	77	0.1 μg μL−1	Bean Yellow Mosaic Virus	Bean yellow mosaic virus	Fava bean	In vivo	[136]
AgNPs	CS	12.6 ± 5	200 ppm	Tomato spotted wilt	Tomato spotted wilt virus	Solanum tuberosum	In vivo	[137]
AgNPs	Commercial	-	50 ppm	Tomato mosaic virus Potato virus Y	Tomato mosaic virus Potato virus Y	Lycopersicum esculentum	In vivo	[138]
AgNPs	Commercial	15	50 ppm		Banana bunchy top virus	Musa sp.	In vivo	[139]
ZnONPs	CS	18	100 μg mL−1	Tobacco mosaic virus	Tobacco mosaic virus	Nicotiana benthamiana	In vivo	[140]
ZnONPs	GS (Mentha Spicata)	11–88	100 µg mL −1	Tobacco mosaic virus	Tobacco mosaic virus	Solanum lycopersicum L.	In vivo	[141]
NiONPs	CS	15–20	150 μg L−1	Cucumber mosaic virus	Cucumber mosaic virus	Cucumis sativus	In vivo	[142]
Fe3O4NPs	GS (Syzygium cumini)	0.19	100 μg mL−1	Tobacco mosaic virus	Tobacco mosaic virus	Nicotiana benthamiana	In vivo	[143]
AuNPs	CS	3.151–31.67	0.034 mg 100 mL−1	Gold barley yellow dwarf virus	Barley yellow dwarf virus-PAV (BYDV-PAV)	Hordeum vulgare	In vivo	[144]
TiO2NPs	CS	20	150 µg mL−1	Tobacco Mosaic Virus	Tobacco mosaic virus	Capsicum annuum L.	In vivo	[145]

GS: green synthesis, CS: chemical synthesis.

).

9. Action Mechanism of Nanopesticides

Some potential mechanisms by which MNPs can be used against pests are presented below.

9.1. Physical Disruption

MNPs can induce physical damage to pests through direct interactions. Their reduced size and increased surface area enhanced their ability to interact extensively with the exoskeleton of insects, leading to mechanical disruption and structural damage [8,30]. AgNPs smaller than 10 nm can penetrate bacterial cell membranes, disrupting cell permeability and inducing cellular damage [146]. Greater membrane damage in bacterial cells reduces activity and limits silver nanoparticle uptake, explaining the lower silver internalization in E. coli at high concentrations. This suggests that the bactericidal effect at high concentrations is primarily due to membrane disruption [147].

9.2. Chemical Interaction by Reactive Oxygen Species (ROS) Generation

MNPs exhibit antimicrobial effects primarily through the generation of ROS. Upon interaction with microbial cells, MNPs can trigger the production of ROS, including superoxide radicals (O₂•−), hydroxyl radicals (•OH), and hydrogen peroxide (H₂O₂) [148]. These ROS cause oxidative stress, leading to lipid peroxidation, oxidative carbonylation of proteins, and the deactivation of certain enzymes [149]. This oxidative damage disrupts critical cellular functions, ultimately resulting in microbial cell death.

The generation of ROS by MNPs begins upon their entry into the cell, where they stimulate inflammatory mediators, such as intracellular calcium levels, signal transducers and activators of transcription (STATs), and nuclear factor kappa B (NF-κB). These nanoparticles can directly or indirectly activate mitogen-activated protein kinase (MAPK) signaling pathways, leading to the production of reactive free radicals and subsequent oxidative stress within the cell [150].

9.3. Biological Mechanism

MNPs can interact with pests’ immune systems, potentially stimulating immune reactions that can weaken or eliminate them [8]. TEM studies on AgNPs in Achaea janata show that a small amount of absorbed silver accumulates in cell organelles, causing physiological changes in the larval body. This suggests that AgNPs interfere with metabolism, leading to oxidative stress [46]. Similarly, research using an eco-friendly insect pest control demonstrated that AgNPs induced oxidative stress, leading to damage in the gut epithelial cells of Spodoptera litura, affecting their development and physiology [151].

10. Mechanism of Nanopesticide Inside the Pest Cell

Several mechanisms of nanopesticide action within pest cells have been identified, including membrane disruption, DNA damage, mitochondrial dysfunction, and protein denaturation. Figure 2 illustrates the detailed intercellular mechanism of nanopesticide activity. Nanopesticides penetrate the cell, causing a series of cytotoxic effects that disrupt cellular function. They compromise membrane integrity, leading to structural damage and altered permeability, while also interacting with DNA, inducing genotoxic effects that may result in mutations or genomic instability. Mitochondrial dysfunction occurs due to interference with ATP production, impairing cellular energy metabolism. Additionally, nanopesticides cause protein denaturation, leading to structural integrity and biological function loss. Their presence also triggers oxidative stress by promoting the production of ROS, which damages lipids, proteins, and nucleic acids. Collectively, these effects contribute to cellular dysfunction and can ultimately lead to cell death via apoptotic or necrotic pathways.

10.1. Membrane Damage

The antibacterial mechanism of MgO nanoparticles was demonstrated, revealing potent antibacterial activity in the absence of ROS production. Electron microscopy and proteomics analyses indicate that exposure to MgO nanoparticles results in damage to the cell membrane of E. coli. No evidence of oxidative stress nor lipid peroxidation was observed [152]. When MNPs encounter microbial cells, they can disrupt the integrity of the cell membrane. This disruption is often caused by the interaction between the MNPs and the phospholipid bilayer that makes up the cell membrane. In another study assessing AgNPs using TEM, the analysis revealed that AgNPs adhered to the membrane surface, leading to membrane damage [153].

10.2. DNA Damage

Certain nanoparticles can penetrate bacterial cells and bind to DNA, inhibiting replication and transcription. MNPs can enter microbial cells and interact with DNA, leading to DNA strand breaks, cross-linking, and other forms of damage. This disruption to DNA integrity can interfere with vital cellular processes like replication and transcription, ultimately leading to cell death. The study demonstrates genomic DNA damage in bacteria following treatment with CuNPs. Exposure to 5, 10, 50, and 100 μg mL⁻¹ of 20 nm CuNPs resulted in a concentration-dependent increase in DNA smearing and degradation, as evidenced by the progressive disappearance of DNA bands, indicating extensive DNA damage [154].

10.3. Mitochondrial Disruption

Certain MNPs can accumulate in mitochondria, where they interact directly with mitochondrial membranes and proteins. These interactions may lead to damage to mitochondrial structure and disrupt normal function. For instance, positively charged gold nanoparticles (cationic AuNPs) have been shown to impair mitochondrial activity by directly affecting key mitochondrial components [155].

Some metal nanoparticles release ions that can disrupt microbial cell functions. Research on Achaea janata treated with AgNPs reveals microscopic evidence of their localization and accumulation within various organelles, including mitochondria [46]. These ions can interfere with cellular processes, such as enzyme activity and cell signaling, ultimately leading to cell death. Heavy metal ions are known to transport antimicrobial agents indirectly [156].

10.4. Protein Denaturation

Exposure to metal nanoparticles causes a significant transformation in protein structure, shifting from small particles to rodlets, filaments, and thick fibrils, which eventually form large fibrils and a complex network of fibrils and plaques [157]. One of the mechanisms is direct interaction with the protein. MNPs have the capacity to interact directly with cellular proteins, inducing conformational alterations that lead to protein denaturation. For example, CuNPs have been demonstrated to significantly impact the structural integrity, stability, and enzymatic activity of key metabolic proteins, indicating direct nanoparticle–protein interactions that may compromise normal protein function [158].

Another mechanism is the formation of a protein corona. When nanoparticles enter biological systems, they often become coated with proteins, forming a layer called the protein corona. This adsorption can induce structural modifications in the native conformation of the proteins, potentially resulting in denaturation. The formation of the protein corona significantly influences the biological identity and behaviour of nanoparticles, affecting key processes such as cellular uptake, immune response, biodistribution, degradation, and clearance [159].

11. Toxicity of Metal Nanoparticles to Plants

Despite the positive impact of metal-based nanoparticles, there are also certain toxic effects on plants. Many studies review metal-based nanoparticle toxicity specifically, such as silver nanoparticle toxicity [160,161], copper nanoparticle toxicity [162], zinc oxide nanoparticle toxicity [163], nickel nanoparticle toxicity [164], titanium dioxide nanoparticle toxicity [165], magnesium oxide nanoparticle toxicity [166], gold nanoparticle toxicity [167], and iron nanoparticle toxicity [168].

Furthermore, nanoparticles engage with biological systems through five main mechanisms: (i) chemical effects when metal ions dissolve in solution; (ii) mechanical influences arising from their firm and specific interfaces; (iii) catalytic activities taking place on surfaces; (iv) surface effects from protein binding, either non-covalently or covalently, or oxidative effects; and (v) alterations in the chemical environment, such as changes in pH [169].

In addition, different types of nanoparticles exhibit varying environmental impacts, with organic and biologically derived nanoparticles generally showing lower toxicity compared to metallic and chemically synthesized types [170]. It is worth noting that some products marketed as nanofertilizers are composed of micro-sized particles, highlighting the lack of rigorous regulation even at the market level. This raises concerns about the scalability of toxicity issues associated with these particles, emphasizing the need for comprehensive regulatory oversight in the use of nanofertilizers [171].

Moreover, nanoparticles can interact with cell membranes, altering their structure and permeability. This disruption can compromise cellular integrity, ion transport mechanisms, and nutrient uptake, negatively impacting seedling development and overall plant growth. Some nanoparticles have been found to cause genotoxicity by inducing DNA damage in plant cells. This can lead to mutations, chromosomal abnormalities, and impaired genetic integrity, affecting plant growth, development, and reproductive success.

The absorption of AgNPs disrupts water and small molecule balances, hinders chlorophyll production, reduces photosynthetic effectiveness, and triggers excessive ROS production. This ROS overload damages chloroplasts and could result in stunted growth or plant death [172]. NPs engage with plants through diverse chemical and physical mechanisms, triggering signalling pathways that culminate in ROS production [173]. Nanoparticles can induce oxidative stress in plants by generating ROS such as superoxide radicals, hydrogen peroxide, and hydroxyl radicals. Excessive ROS production damages cellular components, like lipids, proteins, and DNA, leading to cell death and impaired growth.

High concentrations (1000 μg mL⁻¹) of 25 nm silver nanoparticles were toxic to Oryza sativa, damaging cell walls, and vacuoles as they entered the roots [174]. High concentrations of nanoparticles can directly affect seed germination by inhibiting water uptake and nutrient absorption. This leads to reduced seedling emergence and poor initial growth. Nanoparticles may also disrupt cellular processes within seeds, affecting metabolism and energy production crucial for germination.

Regarding CuONPs and their interactions with plants, findings have demonstrated adverse effects on plants at physiological levels, including inhibited root length, reduced biomass, and delayed plant development. Additionally, at cellular levels, CuONPs disrupt chlorophyll synthesis, damage cell membranes, and induce chromosomal abnormalities [175].

Plants exposed to toxic levels of nanoparticles often activate stress response pathways, including antioxidant defense systems and detoxification mechanisms [176]. While these responses are aimed at mitigating nanoparticle-induced damage, sustained stress can divert resources away from growth-related processes, affecting overall plant fitness. Nanoparticle toxicity can alter root morphology and function [177], including root elongation, branching patterns, and nutrient uptake capacity. Abnormal root growth hampers nutrient acquisition and water absorption, further impairing plant growth and development. Nanoparticles can translocate within plants and accumulate in various tissues [178]. Accumulation of nanoparticles in vital plant organs can disrupt physiological processes [179], interfere with nutrient transport, and lead to systemic toxicity, ultimately affecting plant growth and productivity.

The environmental release of nanoparticles, either intentionally through agricultural practices or unintentionally via industrial processes, raises concerns about their potential ecological impacts. Accumulation of nanoparticles in soil, water bodies, and ecosystems can disrupt microbial communities, alter nutrient cycling, and pose risks to non-target organisms. Addressing nanoparticle toxicity in agriculture requires careful optimization of nanoparticle dosages, consideration of nanoparticle properties (size, shape, surface charge), evaluation of plant species-specific responses, and implementation of sustainable nanoparticle application practices. Regulatory frameworks and risk assessment protocols are also crucial to guarantee the safe and conscientious utilization of nanoparticles in agriculture, while minimizing environmental risks and maximizing benefits for crop productivity and sustainability.

12. Potential Concerns and Challenges

12.1. Regulatory Challenges

The public perception of nanotechnology in food production is influenced by factors such as safety concerns, regulatory oversight, consumer awareness, and perceived benefits. While nanotechnology offers advantages like improved food safety, longer shelf life, and enhanced nutritional value, consumers often express skepticism due to potential health risks and environmental impacts.

According to research of consumer perceptions of nanotechnology use in food processing, perceived benefits, subjective norms, institutional trust, and subjective knowledge were found to have significant and positive effects on participants’ attitudes toward the use of nanotechnology in food processing. Conversely, perceived risks and food technology neophobia exhibited significant negative influences on these attitudes. These findings highlight the importance of communication strategies that emphasize the consumer-relevant advantages of nanotechnology, address and reduce perceived risks, leverage the impact of social norms, and prioritize safety-related messaging from trusted institutional sources [180].

The study surveyed consumers across four countries: Australia, India, Singapore, and the United States, to assess their willingness to consume foods produced using various novel technologies, including nanotechnology. The results revealed significant cross national and cross technology differences in consumer perceptions. Based on acceptance levels, the novel food technologies were grouped into three categories: (1) high acceptance, including vegetables produced through urban farming and those packaged in a modified atmosphere; (2) moderate acceptance, including fish produced via aquaponics, plant-based meat and dairy alternatives, and gene editing technologies; and (3) low acceptance, including foods containing insect-based ingredients, as well as cell cultured meat and fish. Notably, Indian consumers demonstrated a higher level of acceptance toward these technologies compared to consumers in Australia and the United States. These findings underscore the importance of considering cultural and regional differences when promoting and implementing novel food technologies [181].

Research on public perception and knowledge of nanotechnology (NT) in Austria remains limited, particularly in relation to its functions, benefits, and potential risks. Findings from the “Nan-O-Style” project reveal a generally positive attitude toward NT among the Austrian public, along with a strong demand for increased information, transparency, and clear product labelling. While sociodemographic factors, such as education level and gender, influenced knowledge and information needs, they did not significantly affect overall attitudes toward NT. Notably, individuals with negative perceptions of NT also showed limited interest in acquiring further information, suggesting that simply providing more information may not be sufficient to change attitudes. These findings highlight the need for tailored, trust-building communication strategies to address public concerns and promote informed engagement with emerging technologies, such as NT [182].

12.2. Environmental Impact

A 2022 study investigated the toxicity of various metallic nanoparticles (NPs) on marine species. AgNPs demonstrated the highest toxicity, followed by zinc oxide (ZnO), copper oxide (CuO), and titanium dioxide (TiO₂) nanoparticles. The study emphasized that the toxicity of these nanoparticles is significantly influenced by both their nanoscale size and the release of ions, highlighting the need to consider particle characteristics and environmental conditions when conducting risk assessments [183].

In 2023, researchers assessed the presence and potential risks of micro- and nanoplastics (MNPs) in Laizhou Bay, China. The study identified nanoparticles of silver (Ag), zinc oxide (ZnO), copper oxide (CuO), and titanium dioxide (TiO₂) in both seawater and sediment samples. The highest concentrations were observed near the Yellow River Estuary, which was linked to riverine input. Risk assessments indicated that certain regions exhibited “high risk” levels for AgNPs and TiO₂NPs, underscoring the importance of ongoing monitoring and management efforts [184].

13. Conclusions and Future Prospects

MNPs have significant practical implications for modern agriculture, offering innovative solutions to improve pest control, enhance nutrient delivery, and increase crop productivity. Their unique properties, such as controlled release, enhanced solubility, and improved target specificity, enable more efficient use of agrochemicals, reducing both costs and environmental impact. By integrating MNPs into agricultural practices, farmers can achieve higher yields with lower inputs, making agriculture more sustainable and resource-efficient.

However, before MNPs can be widely commercialized in agriculture, several critical challenges must be addressed, including their potential toxicity, environmental persistence, cost-effectiveness, and regulatory approval. Research has shown that these nanoparticles can interact with soil microbiota, influencing nutrient cycling and plant health. Additionally, concerns about nanoparticle accumulation in soil and water, as well as the possibility of pests developing resistance, highlight the need for long-term environmental monitoring.

Scaling up the use of nanopesticides and nanofertilizers requires optimizing their formulations to balance efficacy with safety. Developing smart delivery systems that release nutrients or active ingredients in response to specific environmental conditions could enhance efficiency while minimizing unnecessary chemical applications. Furthermore, rigorous assessments are necessary to evaluate their impact on ecosystems, including potential bioaccumulation and unintended effects on non-target organisms.

In conclusion, while MNPs present transformative opportunities for agriculture, their practical application must be guided by a multidisciplinary approach. Future research should focus on developing eco-friendly nanoparticle formulations, establishing regulatory frameworks, and ensuring their safety for both human health and the environment. By addressing these challenges, MNPs can play a crucial role in advancing sustainable and efficient agricultural practices, paving the way for a new era of precision farming.

Future studies should focus on the efficacy and safety of MNPs in real-world agricultural settings, assessing their potential benefits and drawbacks. By prioritizing comprehensive research, we can better understand how to integrate these innovative solutions into current pest management strategies while minimizing ecological risks. Additionally, collaboration among researchers, policymakers, and farmers will be essential to develop guidelines that ensure the responsible use of MNPs. This collaborative approach will facilitate the sharing of knowledge and best practices, ultimately leading to more sustainable agricultural practices.