Nanoparticle-Enhanced Fish Feed: Benefits and Challenges

Abstract

Aquaculture production is continuously increasing, consequently increasing the demand for feed. Unfortunately, the reliance on fish meal and fish oil also raises sustainability issues due to overfishing and resource depletion. Nanoparticle-enhanced feed presents a promising solution to these challenges. Nanoparticles, with their large surface area-to-volume ratio and encapsulation capabilities, significantly improve nutrient delivery, absorption, and utilization, enhancing growth and health. Their immune-modulatory and antimicrobial properties reduce antibiotic use and support sustainability. This review explores different nanoparticles in fish feed, including metal-based, non-metal-based, and composite types, each offering benefits for fish growth and health. It highlights the advantages of nanoparticle-enhanced feed, such as improved nutrient delivery, immune enhancement, antimicrobial action, stress reduction, and environmental sustainability. Concerns like potential toxicity, safety, bioaccumulation, and environmental impacts of nanoparticles, together with measures of addressing these concerns, are also highlighted. The review concludes with insights into future research directions.

1. Introduction

Global aquaculture production has steadily increased, reaching 223.2 million tonnes in 2022, with 185.4 million tonnes from aquatic animals and 37.8 million tonnes from algae [1]. The rise in fish production increases the demand for fish feed, which is crucial for providing essential nutrients necessary for the growth, health, and productivity of farmed fish [2]. Traditional fish feeds are formulated with macronutrients (proteins, lipids, carbohydrates), micronutrients (vitamins, minerals), and other essential ingredients primarily sourced from marine products such as fish meal and fish oil [3]. These feeds aim to enhance nutritional quality, improve feed conversion ratios, and promote growth [4,5,6]. However, the reliance on fish meal and fish oil drives up costs and raises sustainability concerns due to overfishing and resource depletion [7,8]. To address these issues and improve sustainability, there has been a shift towards partially replacing marine ingredients with vegetable-based alternatives. However, this shift introduces challenges such as reduced feed utilization due to non-starch polysaccharides, lower phosphorus content affecting fish health, indigestible fibers impairing digestion, a lack of essential amino acids like methionine, and decreased palatability [3]. Additionally, these feed types, whether prepared as bulk or premixed formulations, face issues such as nutrient degradation during storage and processing, and inadequate control over nutrient release kinetics. These problems can lead to nutrient wastage, inconsistent absorption, and reduced effectiveness [9,10,11].

Nanoparticle-enhanced fish feed presents a promising alternative strategy towards promoting sustainable aquaculture [12]. Nanoparticles (NPs), ranging from 1 to 100 nanometers in size, possess unique physical and chemical properties that can be utilized to overcome some limitations found in both marine-derived and plant-based feeds. Additionally, the tunable structural features and characteristics of NPs enable researchers to customize them for diverse aquaculture feeds, leading to significant improvements in feed efficiency, fish growth, and overall health and disease resistance [13,14,15,16]. Size and shape can be precisely controlled using various synthesis methods, including chemical (sol–gel, chemical vapor deposition), template-assisted, electrochemical techniques, and seed-mediated growth, among others [17,18,19]. Smaller nanoparticles, due to their high surface area-to-volume ratio allow for molecular-level interactions with biological systems, enabling precise targeting and nutrient uptake. This enhances nutrient absorption and bioavailability, resulting in improved feed performance and reduced waste [20,21]. For example, due to their high surface area-to-volume ratio, NPs can be more easily broken down and absorbed in the fish’s digestive system. This increased surface area enhances interactions with digestive enzymes, leading to improved nutrient digestibility and overall feed utilization [22,23].

NPs can be engineered into various shapes such as spheres, rods, or disks [24,25]. The shape of NPs influences their behavior in living organisms, impacting how they circulate, accumulate, penetrate tissues, and are taken up by cells [26,27]. Nonspherical NPs, such as those with rod-shaped or disk-shaped designs, often exhibit longer circulation times and enhanced delivery efficacy compared to spherical NPs. Their unique shapes can improve stability, reduce clearance by the immune system, and facilitate better targeting and uptake by specific cells or tissues [28]. This results in the more effective delivery of nutrients or therapeutic agents.

Adjusting NP composition through doping and hybrid formation allows for the fine-tuning of properties to maximize effectiveness in fish feed [29]. Additionally, surface modification through functionalization, the use of stabilizers, or the use of coatings enhances reactivity, stability, and compatibility, reduces aggregation, and improves interactions with feed ingredients and biological systems [30,31]. Guo et al. demonstrated that NPs with small sizes, low negative charges, and moderate hydrophilicity can readily penetrate the small intestinal mucus layer. Once through the mucus, their effectiveness in traversing intestinal epithelial cells depends on factors like the appropriate size, positive charge, and hydrophobic properties [32]. This suggests that incorporating functional groups, stabilizers, or coatings with amphiphilic properties could enhance NP transport by balancing interactions with both the mucus layer and epithelial cells, optimizing their delivery and effectiveness in the gastrointestinal tract.

The large surface area-to-volume ratio of these NPs also enables the efficient loading and encapsulation of essential nutrients and therapeutic agents. This capability helps protect these components from degradation and ensures their controlled release. Encapsulation not only enhances the stability of nutrients and therapeutic agents but also enhances their absorption by fish. As a result, this leads to improved feed conversion ratios, better growth performance, and overall enhanced health outcomes in aquaculture. Additionally, the targeted delivery of these nutrients can help in minimizing waste [13,14,33].

Furthermore, nanoparticles with immune-modulatory and antimicrobial properties can enhance fish immunity, reduce antibiotic use, and control pathogenic bacteria, promoting better health and reducing disease outbreaks [14,16,33,34,35]. Figure 1 summarizes the different characteristics of nanoparticles and their potential benefits in nanoparticle-enhanced fish feed.

As the aquaculture sector evolves, understanding nanotechnology’s role in fish nutrition is increasingly important. This review explores recent studies on nanoparticle-enhanced fish feed, highlighting its potential benefits and possible challenges. It focuses on how various NPs can improve growth, health, and environmental sustainability in aquaculture, demonstrating the potential of this technology to enhance production efficiency, sustainability, and fish health. It covers a range of nanoparticle types, including metal-based, non-metal-based, and composite or hybrid nanoparticles, each offering unique benefits for fish nutrition.

2. Nanoparticles Used in Fish Feed

Various nanoparticles, including metal-based, non-metal-based, and composite or hybrid nanoparticles, are being explored for their potential to improve fish growth, health, and overall productivity [36]. Most of these NPs are synthesized using fish macronutrients and micronutrients [37,38].

2.1. Metal-Based Nanoparticles

Metal-based nanoparticles consist primarily of metals like zinc, copper, magnesium, manganese, and iron, each providing distinct advantages when used in fish feed [39].

Table 1. Effects of metal-based nanoparticle-enhanced fish feed on various species at different dosages and durations.

NP	Fish	Dosage	Effects	Ref.
Zinc oxide NPs (ZnONPs)	Labeo rohita	10 mg/kg for 45 days	Higher improvement of growth and metabolic functions	[12]
	Oreochromis niloticus (Nile tilapia)	1.5 mg/L	Antibacterial activity against Clostridium perfringes	[40]
		60 µg/g for 8 weeks	Boost immune responses and improve disease resistance to Aeromonas hydrophila infection	[41]
		10 mg/kg for 60 days	Improved growth performance, blood health, intestinal histomorphology, and activated the oxidative stress response	[42]
		60 mg/kg for 84 days	Best growth, digestive enzyme activity, intestinal health, and improved antioxidant capacity.	[43]
		15 mg/kg for 60 days	Innate defense increased during Streptococcus agalactiae infection	[44]
		40 mg/kg for 8 weeks	Enhanced health parameters, antioxidant capacity, immune response, and disease resistance	[45]
		40 mg/kg for 8 weeks	Significant improvement in the growth performance, survival, serum lysozyme activity, phagocytic activity, phagocytic index, respiratory burst activity, expression of immune-related genes, digestive enzyme activity, and histopathological findings in Candida albicans-infected fish	[46]
	Clarias gariepinus (African catfish)	30 mg/kg for 60 days	Alleviated the negative impacts of chronic waterborne Cu exposure on growth performance, physiological changes, gene expression, and tissue architecture	[47]
Iron oxide NPs (Fe2O3-NPs)	Cyprinus carpio (common carp)	40 mg/kg for 70 days	Elevated growth, nutrient absorption, body composition and blood indices.	[23]
	Acipenser stellatus (stellate sturgeon)	50 mg/kg for 60 days	Improved the welfare and survival of stellate sturgeon juveniles	[48]
	O. niloticus	0.4 mg/kg for 12 weeks	Improves immunological performance, filet composition, and the healthiness of the intestinal structure	[49]
		1 g/kg for 30 days	Enhanced properties of growth, hemato-biochemical, immune, and antioxidative profiles, and related genes’ expression of O. niloticus	[50]
	Trichogaster trichopterus (blue gourami)	40 mg/kg for 60 days	Enhanced growth performance, improved biochemical constituents, better hematological parameters, and increased antioxidant activity	[51]
	Etroplus suratensis	20 mg/kg for 60 days	Improved growth performance, nutrient utilization, and the health of E. suratensis.	[52]
	L. rohita	10 mg/kg for 45 days	Improved growth performance	[53]
Magnesium oxide NPs (MgO NPs)	O. niloticus	7.5 μg/mL for 60 days	Improved growth, health status, and increased the resistance of O. niloticus against bacterial and parasitic infection	[54]
	Megalobrama amblycephala (blunt snout bream)	120 mg/kg for 12 weeks	Enhanced growth performance and feed utilization	[55]
	C. gariepinus	0.04 mg/kg for 60 days	Significant improvement in body weight and antioxidant capacity	[56]
Manganese dioxide NPs (MnO2NPs)	Pelteobagrus fulvidraco (yellow catfish)	13.6 mg/kg for 8 weeks	Better growth performance and feed utilization	[57]
	C. carpio	6 mg/100 g for 21 days	Enhanced growth and hematological traits	[58]
	O. niloticus	2 mg/kg for 38 days	Improved growth performance in under multiple stresses	[59]
	Cirrhinus cirrhosus (mrigal carp)	75 mg/kg for 21 days	Enhanced Mrigal’s growth and decreased hematological criterion	[60]
	Pangasianodon hypophthalmus	3 mg/kg for 105 days	Controlled gene regulations against multiple stresses	[61]
Copper NPs (CuNPs)	C. carpio	2.19 to 2.91 mg/kg for 8 weeks	Improved growth performance, feed utilization, immune parameters, and oxidation resistance	[62]
	Oncorhynchus mykiss (rainbow trout)	2 mg/kg for 60 days	Elevated the growth performance, antioxidant capacity, and health of rainbow trout.	[63]
	Pangasianodon hypophthalmus	1.5 mg/kg	Promoted fish immunity, growth performance, and controlled gene regulation	[64]
Copper oxide NPs (CuONPs)	C. carpio	200 mg/100 g for 21 days	Improved the growth performance of the Koi carp	[65]

summarizes various studies on the effects of different nanoparticle dosages on various fish species, showing the species, administered dosage, exposure duration, and observed effects.

2.1.1. Zinc-Based Nanoparticles

Zinc is an essential micronutrient for fish, critical for normal growth, metabolic regulation, immune response, gene expression, and reproductive health [66]. Zinc supplements often fall short in ensuring optimal zinc uptake, whereas zinc nanoparticles have shown superior efficacy. Due to their small size, these nanoparticles facilitate efficient zinc absorption, significantly enhancing bioavailability and utilization [13,14,15,16]. High nutrient bioavailability is critical in fish nutrition for maximizing nutrient utilization, leading to improved growth, health, and overall performance. NPs enhance this process by increasing the surface area available for interaction with the digestive system and targeting specific sites within the gastrointestinal tract, thereby improving the delivery and uptake of micronutrients [67]. A study on O. niloticus (Nile tilapia) fingerlings compared the effects of bulk ZnO and ZnONPs at a dosage of 60 mg/kg over 84 days. Results indicated that fish fed with ZnONPs exhibited superior growth, enhanced digestive enzyme activity, improved intestinal health, and the highest oxidative enzyme activity coupled with the lowest oxidative stress levels. These findings highlight the potential of NPs in promoting robust health and growth in aquaculture species [43].

NPs can also enhance fish health and disease resistance by stimulating the immune system. They act as immune triggers, boosting antibody and cytokine production, enhancing immune cell function, and delivering immune agents directly to cells, thus improving treatment efficacy [41,45,68,69]. This leads to reduced disease rates, lower antibiotic use, and better growth and feed efficiency. For instance, the inclusion of ZnONPs in O. niloticus feed was shown to enhance immune responses and disease resistance against A. hydrophila [41].

In addition, nanoparticle-enhanced fish feed offers significant antimicrobial benefits. NPs can disrupt microbial cell membranes and interfere with essential cellular processes, leading to microbial cell death [70]. For example, Metryka et al. examined the effects of ZnONPs and other metal NPs (AgNPs, CuNPs, and TiO₂ NPs) on Escherichia coli, Bacillus cereus, and Staphylococcus epidermidis. The study found that various types and concentrations of NPs uniquely affected bacterial membrane permeability, cytoplasmic leakage, adenosine triphosphate (ATP) levels, ATPase activity, and fatty acid profiles. E. coli was the most sensitive to these nanoparticles, with ZnONPs and CuNPs having particularly significant impacts [71]. This research highlights the complex interactions between metallic NPs and bacterial cells resulting in antimicrobial activities. NPs can also disrupt bacterial biofilms, increasing pathogens’ vulnerability to treatments [72]. The surfaces of NPs can be modified with antimicrobial coatings to target specific pathogens. They can also be engineered to load and release antimicrobial agents directly at infection sites [73]. For instance, ZnONPs functionalized with glutamic acid and conjugated with thiosemicarbazone, combined with thymol, demonstrated enhanced antibacterial activity with a minimum inhibitory concentration of 3.12–25.5 µg/mL and a 95% biofilm inhibition, suggesting a promising approach for P. aeruginosa infections [74].

Table 1 provides an overview of the effects of zinc oxide nanoparticles (ZnONPs) on different fish species at various dosages and exposure durations. The application of ZnONPs in fish feed demonstrates a range of benefits across different fish species, including enhanced growth, improved immune responses, better oxidative stress management, and increased disease resistance. The dosage and duration of ZnONP administration are critical factors that influence the extent of these benefits. Proper dosage ensures that fish receive the optimal amount of nutrients for maximum growth while minimizing excess feed and waste, thereby reducing the environmental impact [12,40,41,42,43,44,45,46,47,75]. ZnONPs emerge as a promising additive in aquaculture, enhancing fish health and performance, and fostering sustainable aquaculture practices.

2.1.2. Iron Nanoparticles

In aquatic animals, iron is crucial for numerous physiological processes, including redox reactions and electron transport involved in cellular respiration, growth rate, and fatty acid metabolism [14,39]. It plays crucial roles in fish biology, such as heme synthesis, iron storage in ferritin, and the formation of Fe-S clusters. Furthermore, iron is present in enzymes like catalase and lipoxygenases [76,77].

Iron nanoparticles (FeNPs) have emerged as a promising addition to fish feed due to their unique properties and potential benefits for aquaculture [75]. Their small size and large surface area-to-volume ratio enhance nutrient absorption in the digestive tract, ensuring fish receive sufficient iron for crucial physiological functions [14]. This increased bioavailability supports cellular respiration, growth rate regulation, and fatty acid metabolism, leading to improved growth rates and overall health.

Table 1 shows the effects of Fe₂O₃NPs on various fish species, demonstrating significant improvements in growth, health, and overall performance across different dosages and exposure durations. It highlights the benefits of Fe₂O₃NPs in fish feed, including elevated growth rates, improved nutrient absorption and utilization, and enhanced biochemical and hematological parameters. Additionally, Fe₂O₃NPs contribute to better immune responses and the overall health and survival rates of fish [48,49,50,51,52,53,76,78]. For instance, Fe₃O₄NPs at a dose of 1.2 mg/L have been reported to have a therapeutic effect in C. gariepinus against Aeromonas sobria [79]. These positive outcomes across different species and conditions accentuate the potential of Fe₂O₃NPs as a valuable additive in aquaculture, promoting the superior health and performance of cultured fish. Incorporating these NPs into fish diets could lead to more sustainable and efficient aquaculture practices.

2.1.3. Magnesium Nanoparticles

Magnesium nanoparticles, due to their small size and large surface area-to-volume ratio, are more easily absorbed in the digestive tract of fish compared to conventional magnesium supplements [39]. This improved bioavailability ensures that fish receive sufficient magnesium, which is crucial for various physiological processes, including protein synthesis, enzyme activation, energy production, and the development and maintenance of healthy bones and muscles [80]. By providing a more bioavailable form of magnesium, Mg-based NPs can enhance these metabolic processes, leading to improved growth rates and better overall health in fish [81,82,83].

The application of magnesium oxide nanoparticles (MgONPs) in fish feed has shown promising results across various fish species, as detailed in Table 1. The benefits include improved growth, enhanced health status, and increased disease resistance [54,55,56]. These advantages highlight the potential of MgONPs as a valuable feed additive in aquaculture, promoting enhanced fish health and performance, and fostering sustainable aquaculture practices.

2.1.4. Manganese Nanoparticles

Manganese is a vital trace mineral for fish, essential for enzyme function, metabolism, bone development, reproductive health, immune function, and growth. It aids in protecting cells from oxidative damage, synthesizing critical molecules, forming bones and cartilage, supporting reproductive hormone synthesis, enhancing immune response, and influencing nervous system development [67,84]. Optimal manganese levels in fish feed are crucial for health and productivity.

Table 1 summarizes the effects of manganese dioxide nanoparticles (MnO₂NPs) on various fish species, indicating notable improvements in growth, feed utilization, hematological traits, and stress response across different dosages and exposure durations. For instance, in P. fulvidraco (yellow catfish), a dosage of 13.6 mg/kg over 8 weeks led to better growth performance and feed utilization [57], highlighting the efficiency of MnO₂NPs in nutrient uptake. Cyprinus carpio (common carp) exhibited enhanced growth and improved hematological traits when administered 6 mg/100 g for 21 days [58], showcasing the dual benefits for physical development and blood health. In P. hypophthalmus (pangasius catfish), a dosage of 3 mg/kg for 105 days helped control gene regulation under multiple stress conditions [61], pointing to MnO₂NPs’ role in genetic adaptation and resilience.

These positive outcomes suggest that MnO₂NPs can be a valuable additive in aquaculture, promoting better health and performance in fish under different environmental conditions. However, the specific effects vary depending on the species, dosage, and duration, indicating the importance of tailored application strategies for optimal results. This emphasizes the need for species-specific research and careful dosage management to maximize the benefits of NPs in aquaculture.

2.1.5. Copper Nanoparticles

Copper is a vital trace element for all living organisms, including fish, playing a crucial role as a component of enzymes necessary for various life processes. It acts as a cofactor for specific proteins and enzymes, facilitating metabolic processes such as antioxidant reactions by scavenging free radicals. Copper is also essential for electron transport, and the formation of hemoglobin and collagen [85,86,87]. A study by Kumar et al. found that copper-supplemented diets at 8 mg/kg effectively reduced stress from arsenic, low pH, and high temperatures in P. hypophthalmus. These diets downregulated oxidative stress genes (catalase, superoxide dismutase, and glutathione peroxidase) and stress proteins (heat shock protein, inducible nitric oxide synthase, metallothionine, caspase 3a, and cytochrome P450). They also improved immunity-related genes (tumor necrosis factor alpha, immunoglobulins, and toll-like receptors) and attributes (albumin, globulin, total protein, blood glucose, nitroblue tetrazolium, myeloperoxidase). Additionally, the diet increased neurotransmitter enzyme and vitamin C levels, reduced DNA damage, and enhanced growth indices. Copper diets also decreased arsenic bioaccumulation, improved immunity, and increased survival rates after A. hydrophila infection, suggesting their effectiveness in helping fish cope with environmental stressors, enhancing health, and boosting survival rates [87].

Fish typically obtain copper from water and their diet, but the copper in water is often insufficient. Therefore, supplementing copper in fish feed is necessary to achieve optimal health levels [88]. Copper nanoparticles (CuNPs) are known for their superior bioavailability compared to inorganic copper forms, as their small size facilitates easier absorption through endocytosis and cell bypass mechanisms. This enhances their biological effects and availability [89]. For instance, Afshari et al. showed that nanoparticulate Cu improved the growth and immune responses of snow trout more effectively than bulk copper [90]. The high bioavailability of CuNPs can reduce the need for additional copper supplements and decrease copper waste excretion, benefiting fish health by reducing water pollution.

Table 1 indicates that both CuNPs and CuONPs significantly enhance fish health and performance. CuNPs are shown to improve growth, immune function, and antioxidative capacities across various fish species [62,63,64], while CuONPs are particularly effective in boosting growth in Koi carp [65]. These nanoparticles show great promise as fish feed additives, enhancing growth rates, immune responses, and oxidative stress management. The benefits vary with dosage and species, highlighting the need for customized application strategies in aquaculture.

2.2. Non-Metal-Based Nanoparticles

Non-metal-based nanoparticles are increasingly being explored as additives in fish feed due to their potential benefits for fish health and growth [91,92].

Table 2. Effects of non-metal-based nanoparticle-enhanced fish feed on various species at different dosages and durations.

NP	Fish	Dosage	Effects	Ref.
Selenium NPs (SeNPs)	O. niloticus	1 mg/kg	Significant improvements in growth, feed efficiency, and survival rates.	[91]
		2 mg/kg for 56 days	Improved growth performance, survival, and chemical composition (protein).	[92]
		1 mg/kg for 4 weeks	SeNPs could mitigate the oxidative stress induced by feeding the aflatoxin diet and could boost the immunity of stressed O. niloticus (Nile tilapia).	[93]
		0.1–1.2 mg/kg	Improved growth performance and antioxidant capacity, stabilized the intestinal structure, and enhanced resistance to hypoxic stress and Streptococcus agalactiae-based infection of juvenile O. niloticus (Nile tilapia).	[31]
	Ctenopharyngodon idella (grass carp)	0.3 mg/kg for 60 days	Promoted the growth and antioxidant capacity of grass carp, with excellent bioavailability of Se.	[94]
	Lates calcarifer (Asian seabass)	4 mg/kg for 60 days	Improved growth and health indices in L. calcarifer juveniles.	[95]
	Acanthopagrus arabicus (Arabian yellowfin seabream)	1 mg/kg for 60 days	Enhanced growth, immunity, and stress resistance.	[96]
	Sparidentex hasta (sobaity seabream)	2 mg /kg for 60 days	Promoted growth performance and enhanced antioxidant and immune parameters in sobaity juveniles.	[97]
Soy protein NPs (SPNPs)	Lates calcarifer (Asian sea bass)	50% of fishmeal protein replaced with single-cell protein (SCP) from soybean processing wastewater for 24 days	The replacement of fishmeal protein with microbial community-based SCP did not affect Asian seabass growth or survival.	[98]
	-	Dispersion gave 155.7 mg/L solubilized curcumin	Protected curcumin from degradation or precipitation during simulated gastric-intestinal digestion, showing a significantly enhanced bioaccessibility.	[99]
Protein NPs	D. rerio (Zebrafish) and O. mykiss (rainbow trout)	20 μg/fish	Nanoparticles are taken up in vitro by zebrafish ZFL cells and in vivo by intubating zebrafish. NPs evoke an antiviral innate immune response in ZFL cells and in rainbow trout head kidney macrophages.	[68]
Lipid-based NPs (LNPs)	Oreochromis spp. (Red tilapia)	30 ppm for 21 days	Alkyl polyglucoside nanostructured lipid carriers achieved high encapsulation efficiency, thermal stability, and cost-effectiveness for the masculinization of tilapia with 17 alpha-methyltestosterone when delivered orally at 30 ppm for 21 days.	[100]
	Gilthead sea bream and European sea bass	20 µg/mL for 24 h	Grape seed extract (GSE) mixture containing several antioxidant compounds loaded on solid lipid nanoparticles (SLNPs) enhanced the viability and antioxidant properties of fish cells.	[101]
	Lates calcarifer (Asian sea bass)	Mucoadhesive nano-encapsulated vaccine: water dilution of 1:100 (v/v) for 8 weeks	Mucoadhesive nano-encapsulated vaccine (cationic lipid-based nanoparticles combined with an antigen obtained from F. oreochromis) improved the efficiency of mucoadhesive vaccination against columnaris disease and strengthened immunity in Asian sea bass by increasing serum antibody levels, upregulating immune-related genes, and increasing survival.	[102]
Chitosan-based NPs (CTNPs)	L. rohita	0.6% L-methionine in in total feed for 60 days	L-methionine-loaded chitosan nanoparticles (M-CTNPs) exhibited the sustained and slow release of methionine over a prolonged period resulting in higher growth rates, improved protein efficiency, and enhanced sero-immunological test scores.	[103]
	O. niloticus (Nile tilapia)	1.0 g/kg of N-acetyl-D-glucosamine (NAG)-loaded CTNPs	NAG-loaded CTNPs significantly enhanced the immune-modulatory properties, growth performance, and disease resistance of O. niloticus (Nile tilapia).	[69]
		5 g/kg for 10 weeks	Improved growth and some health indications.	[104]
		5 g/kg thymol and CTNPs mixture for 10 weeks	The synergistic effect of thymol combined with CTNPs enhanced feed utilization, protein utilization, the hematological profile, antioxidant enzymes, and intestine morphology.
		5 g/kg CTNPs mixed with 250 or 500 mg vitamin C for 72 days	Significant enhancement in all growth performance parameters, body indices, and survival rates.	[105]
		0.5% CTNPs in fish diet	Alleviated doxycycline-induced toxicity in fish by controlling oxidative stress and inflammatory cytokines.	[106]
	Oncorhynchus mykiss (rainbow trout)	5 g/kg for 21 days	Enhanced resistance and inflammatory responses to infections.	[107]

provides a summary of studies examining the impact of different nanoparticle dosages on various fish species. It details the species, dosage levels, exposure durations, and observed effects.

2.2.1. Selenium Nanoparticles

Selenium (Se) is a vital micronutrient in aquafeeds, essential for promoting growth, welfare, and overall health in various fish species. Providing selenium in precise amounts can enhance growth performance, physiological health, and disease resistance in aquaculture [108]. Using selenium nanoparticles (SeNPs) significantly boosts its bioavailability and effectiveness [109].

Nanoparticle-enhanced fish feed plays a crucial role in mitigating stress and enhancing fish health. Incorporating NPs such as Se with antioxidant and anti-inflammatory properties into fish diets helps stabilize the fish’s physiological responses to environmental stressors such as fluctuations in water quality, overcrowding, or handling. This stabilization reduces stress hormone production and minimizes stress-related health issues, including suppressed immune function and increased susceptibility to diseases [31,61,96,106]. For example, sobaity seabream fed diets with 0.5, 1, and 2 mg/kg of SeNPs for 60 days showed increased catalase activity, with the 2 mg/kg group exhibiting the lowest malondialdehyde levels. SeNPs boosted lysozyme and complement activity, particularly at 0.5 mg/kg, and elevated levels of insulin-like growth factor I and immune genes were observed. The SeNPs diet also helped stressed fish recover by reducing plasma glucose concentration. These findings indicate that SeNPs significantly enhance the health and immune function of sobaity seabream, with 2 mg/kg of SeNPs being optimal for boosting immune function and reducing oxidative stress, while 0.5 mg/kg also provides notable immune benefits and supports stress recovery [97].

Research by Eissa et al. on Oreochromis niloticus exposed to Aspergillus flavus infection showed that SeNPs up to 1 mg/kg significantly improved growth, feed efficiency, and survival rates. Additionally, SeNPs enhanced haemato-biochemical parameters, digestive enzyme activity, and antioxidant capacity, supporting overall physiological health and metabolic efficiency. Fish exposed to A. flavus had reduced mortality, indicating a stronger immune response, and significant improvements in intestinal morphology and histopathological scores for key tissues were observed [91]. These examples highlight the potential of SeNP-enhanced feed in improving fish health, stress resilience, and overall performance in aquaculture.

Table 2 highlights the positive impact of SeNPs on various fish species, showing their potential as valuable aquafeed additives. SeNPs enhance growth, feed efficiency, survival, immune response, antioxidant capacity, and stress resistance, with benefits varying by dosage and duration, highlighting the need for tailored application strategies [31,91,92,93,94,95,96,97]. Incorporating SeNPs into fish diets can lead to healthier, more robust fish, improving aquaculture productivity and sustainability.

2.2.2. Protein-Based Nanoparticles

Protein-based nanoparticles (PNPs) are emerging as a promising constituent in fish feed due to their biocompatibility, biodegradability, and ability to improve nutrient delivery. Engineered from various proteins like albumin, casein, and soy protein, PNPs offer a versatile platform for enhancing the nutritional and health benefits of aquafeeds [110,111].

The large surface area-to-volume ratio of these NPs allows for the effective loading, encapsulation, and stabilization of essential nutrients and therapeutic agents, protecting them until they reach their target site. This is crucial for maintaining the stability and bioavailability of sensitive nutrients such as vitamins, minerals, and essential fatty acids that may degrade during feed processing and storage. Encapsulation also shields these nutrients from environmental factors like light, heat, and oxygen, as well as from harsh conditions in the fish’s gastrointestinal tract, including acidic pH and digestive enzymes. This protection enhances nutrient absorption and overall feed effectiveness [112,113,114]. Additionally, these NPs can be engineered for the controlled or sustained release of encapsulated nutrients and therapeutic agents. For example, Tian et al. encapsulated soy isoflavones (SIF) using polymerized goat milk whey protein (PGWP), forming PGWP-SIF nanoparticles with an 89% encapsulation efficiency. These NPs maintained SIF stability under varying pH, salt concentrations, and temperature changes, with only 5.93% of SIF released during gastric digestion and 56.61% released in the intestinal phase. This demonstrated efficient delivery to the small intestine and increased bioavailability [115]. NPs also enhance nutrient solubility due to their large surface area-to-volume ratio, which facilitates the dissolution of water-insoluble nutrients and their distribution in water and the fish’s digestive system. For instance, curcumin, known for its potent antioxidant properties, typically has low aqueous solubility and poor systemic bioavailability. Encapsulation within NPs improves curcumin’s bioavailability by enabling controlled release from the nanoparticle core, thereby enhancing its antioxidant effects. Additionally, the small size of NPs allows for better dispersion in digestive fluids, improving nutrient absorption by the intestinal mucosa [99,116]. For example, Yuan et al. developed soy protein nanoparticles (SPNPs) by self-assembling amphiphilic hydrolysates from partially hydrolyzed soy protein isolate and incorporated curcumin into their hydrophobic core. This method significantly enhanced curcumin’s solubility and stability, improving its gastrointestinal bioaccessibility and demonstrating synergistic antioxidant activity that reduced oxidative damage in hepatoblastoma (HepG2) cells [99].

SPNPs have also been reported to deliver immunostimulants to boost fish immune responses [113]. These examples illustrate how NPs can enhance nutrient delivery, promote better growth rates and feed conversion ratios, and even reduce disease outbreaks, thereby improving overall farm productivity [113,117].

Table 2 summarizes the benefits of SPNP-enhanced fish feed across different fish species, showcasing its potential as an alternative to traditional fish feed. It highlights how this approach improves nutrient bioavailability and enhances immune responses, leading to better fish health and increased aquaculture productivity.

2.2.3. Lipid-Based Nanoparticles

Lipid-based nanoparticles (LNPs) significantly enhance the nutritional value and health benefits of fish feeds. These nanoparticles encapsulate and protect sensitive nutrients like vitamins, minerals, and fatty acids from degradation, ensuring their stability and bioavailability for better nutrient utilization and overall fish health [118]. Yostawonkul et al. conducted a study aimed at producing all-male red tilapia. They achieved this by giving them 60 ppm of the androgen hormone 17 alpha-methyltestosterone (MT) with MT-loaded alkyl polyglucoside nanostructured lipid carriers (APG-NLC) orally for 21 days. Their research found that MT released from MT-APG-NLC was much higher than free MT. Consequently, there were significantly more male fish at the end of the 21-day period compared to the control group. Additionally, APG-NLC showed impressive qualities like a high encapsulation efficiency, thermal stability, and cost-effectiveness when used to masculinize tilapia with MT [100]. These findings highlight the effectiveness of encapsulation technology in enhancing the delivery and efficacy of nutrients, drugs, and sensitive compounds, suggesting a promising avenue for reducing their dosage requirements in aquaculture practices.

LNPs also promote improved growth rates and feed efficiency by gradually releasing encapsulated nutrients at required doses [119], supporting continuous development. They also boost immune response by delivering immunostimulants or vaccines directly to fish, enhancing disease resistance and reducing mortality [120]. Additionally, LNPs deliver antioxidants to fish tissues, reducing oxidative stress, and improving health. For example, Trapani et al. developed a new solid lipid nanoparticle (SLNP) formulation using Gelucire^® 50/13 and Precirol^® ATO5 to deliver grape seed extract (GSE) with antioxidant compounds to fish cells. When cell lines from gilthead seabream and European sea bass were treated with GSE-SLNPs for 24 h, their viability increased. Gene expression analysis showed that antioxidant genes were upregulated, while hsp70 and cytoskeleton-related genes were downregulated [101]. This suggests that GSE-SLNPs could effectively enhance the viability and antioxidant properties of fish.

As shown in Table 2, LNPs can significantly enhance growth, immunity, and disease resistance in various fish species, making them valuable for improving aquaculture productivity and sustainability [100,101,102].

2.2.4. Chitosan-Based Nanoparticles

Incorporating chitosan-based nanoparticles (CTNPs) into fish feed offers numerous benefits. These NPs act as carriers for essential nutrients like vitamins, minerals, and proteins, effectively delivering these vital components to fish and thereby enhancing the overall nutritional value of the feed [21,121,122]. For instance, L-methionine-loaded chitosan nanoparticles (M-CTNPs) demonstrated controlled release in vitro, effectively meeting the dietary methionine requirements of L. rohita fingerlings in a 60-day feeding trial. This supplementation resulted in significantly higher growth rates, improved protein efficiency, and enhanced sero-immunological test scores, including increased levels of serum total protein, serum globulin, the serum albumin ratio, phagocytic respiratory burst/nitroblue tetrazolium reduction, and lysozyme activity. The observed growth enhancement was further supported by elevated levels of liver transaminases and dehydrogenases [103], indicating improved metabolic activity. Similarly, Araujo et al. highlighted the effective controlled release of selenium from Se-loaded chitosan nanoparticles in the diet of O. niloticus. This approach significantly enhanced growth performance, feed efficiency, and antioxidant activity while reducing oxidative stress [121].

Furthermore, O. niloticus fed diets containing 1.0 g/kg of N-acetyl-D-glucosamine (NAG)-loaded CTNPs exhibited significant improvements in growth and immune parameters. These fish showed enhanced specific growth rate, weight gain, survival rate, respiratory burst, and lysozyme activities. Additionally, both biologically active CTNPs and NAG-loaded CTNPs demonstrated potent antimicrobial effects against Streptococcus agalactiae, Aeromonas hydrophila, Pseudomonas aeruginosa, and Pseudomonas fluorescens. The findings suggest that the dietary supplement containing NAG-loaded CTNPs significantly enhances the immune-modulatory properties, growth performance, and disease resistance of O. niloticus (Nile tilapia) [69]. Furthermore, antimicrobial properties help prevent the proliferation of harmful bacteria and pathogens within the fish, reducing the risk of infections and promoting better health [123].

CTNPs can also stimulate the fish’s immune system, enhancing their resilience against diseases and stressors, leading to improved survival rates and performance in aquaculture operations [124]. For instance, administering dietary CTNPs to rainbow trout (Oncorhynchus mykiss) induced varied expression patterns of all targeted inflammatory mediator genes. During enteric redmouth infection, this treatment resulted in mild signs of discomfort and reduced fish morbidity. Increased molecular expressions, mild pathological lesions, and a relatively unaffected splenic reticulin framework were observed, indicating that the therapeutic administration of CTNPs in O. mykiss enhances their resistance and inflammatory responses to infections [107]. These findings suggest that CTNPs have promising biotherapeutic properties, significantly enhancing fish resistance to infections and improving overall fish health and survival rates in aquaculture.

As shown in Table 2, CTNPs significantly enhance various aspects of fish health and performance. CTNPs effectively improve growth rates, protein efficiency, immune response, and disease resistance across different fish species. The addition of specific compounds like methionine, NAG, thymol, and vitamin C with CTNPs further amplifies these benefits, contributing to better feed utilization, oxidative stress management, and overall fish health [69,103,104,105,106,107]. Thus, CTNPs present a promising strategy for enhancing aquaculture productivity and sustainability.

2.3. Composite and Hybrid Nanoparticles

Composite and hybrid nanoparticles, which combine different materials or components, offer enhanced properties and functionalities in fish nutrition [29,42,125,126,127,128].

Table 3. Effects of composite and hybrid nanoparticle-enhanced fish feed on various species at different dosages and durations.

NP	Fish	Dosage	Effects	Ref.
Se/ZnONPs	Oreochromis niloticus (Nile tilapia) O. niloticus	10 mg/kg for 60 days	Synergistic effects that improve growth performance, blood health, and intestinal histomorphology.	[42]
ZnNPs/probiotic Lactobacillus salivarius composite		-	Antifungal and antibiofilm activities against Candida albicans from O. niloticus.	[125]
Graphene oxide (GO) nanosheets/ Se-ZnONPs		1 mg/kg for 8 weeks	Enhanced antioxidant activity and physiological functions; had efficient protein synthesis and increased fish weight.	[29]
GO/ZnONPs nanocomposite
GO/SeNPs nanocomposite			Enhanced antioxidant capacity and physiological functions.
Nano-curcumin/chitosan blend (NCur/CT)		0.00625 + 0.5 g/kg diet for 4 weeks	Promoted growth, digestion, immune status, liver function, antioxidant status, and related gene expression in O. niloticus.	[126]
Exopolysaccharides/ZnONPs	O. mossambicus	10 mg/g for 30 days	Improved growth performance, lowered the death rate and improved the disease resistance of O. mossambicus on exposure to A. hydrophila and V. parahaemolyticus.	[127]
Chitosan nanoparticles (CTNPs)/ SeNPs nanocomposite	In vitro study	50 μL of 1 g L−1	Significantly reduced Aspergillus flavus count and growth.	[128]

provides a summary of studies examining the impact of different composite or hybrid nanoparticle dosages on various fish species. It details the species, dosage levels, exposure durations, and observed effects.

Like other nanoparticles, they act as carriers for essential nutrients and compounds, ensuring their stability and bioavailability. Additionally, these nanoparticles provide a gradual release of nutrients, maintaining a sustained supply for fish over time [15,29,128,129]. For example, ZnONPs, SeNPs, and Se-ZnONPs were loaded on graphene oxide nanosheets (GO) to form hybrid nanocomposites: GO@Se, GO@ZnO, and GO@Se-ZnO. These nanocomposites significantly enhanced antioxidant activity and physiological functions in O. niloticus, making them valuable for aquatic feed. The inclusion of ZnONPs (GO@ZnO and GO@Se-ZnO) in these nanocomposites improved gastrointestinal passage and absorption, leading to more efficient protein synthesis and increased fish weight. Histomorphological examinations revealed severe degeneration in intestinal villi due to Streptococcus iniae infection in O. niloticus, but notable improvements were observed when feed containing GO@Se-ZnO was used. This included increased villi length and branching, boosted immune cell presence, enhanced disease resistance, and weight gain [29]. These results support using nanocomposites in aquaculture nutrition systems, highlighting their potential to improve fish health and growth.

A synbiotic formula was also created by combining pomegranate peel extract, serving as a prebiotic source, with a mixture of probiotic species. This resulted in a product with effective antioxidant and antimicrobial properties. Encapsulated in alginate-CaCl₂ nanocapsules, this alginate nanoencapsulated synbiotic composite exhibited superior physicochemical, biological, and industrial properties compared to its non-encapsulated form [129]. Composite and hybrid nanoparticles can incorporate bioactive compounds with antimicrobial or immunomodulatory properties, enhancing fish health and disease resistance. For instance, O. niloticus fed with Chlorella vulgaris extract coated with magnetic FeONPs exhibited improved immune barrier and antioxidant functions in their skin and gills, leading to better survival rates following infections by Ichthyophthirius multifiliis and A. hydrophila [15].

The recurrent contamination of feed materials with mycotoxigenic fungi poses a risk to both farmed animals and humans [130]. To address this, selenium nanoparticles (SeNPs) were synthesized using Cystoseira myrica algal extract (CE) and conjugated with chitosan nanoparticles (CTNPs), creating a potential antifungal nanocomposite for controlling Aspergillus flavus isolates in fish feed. This nanocomposite significantly reduced A. flavus count and growth after 7 days of storage. The innovatively constructed CTNPs/CE/SeNPs nanocomposite was shown to be an effective, biosafe, and natural fungicidal agent for protecting fish feed from mycotoxigenic fungi [128].

Table 2, shows that composite and hybrid nanoparticles, including Se/ZnONPs, ZnNPs/probiotics, graphene oxide composites, and blends like nano-curcumin/chitosan, significantly enhance various aspects of fish health and performance. These nanoparticles improve growth, digestion, immune status, antioxidant capacity, and disease resistance. Their synergistic effects and enhanced bioactivities suggest their potential as effective additives in aquaculture feeds, promoting better growth rates, health, and disease resistance while possibly reducing the need for medications and supplements [29,42,125,126,127,128]. This makes them valuable for advancing aquaculture productivity and sustainability.

It should be noted, however, that the feed processing methods used for incorporating NPs can impact their stability, dispersion, and overall effectiveness. Factors such as heat treatments, exposure to moisture, and chemical interactions can alter NP properties. Thus, the selection of an appropriate feed processing technique and optimizing processing conditions is essential to fully harness the benefits of nanoparticles in fish feed [131,132]. When effectively optimized, nanoparticle-enhanced fish feed has the potential to be a profitable investment. Although initial production costs for NPs may be high, the long-term benefits, including improved feed efficiency, better fish health leading to reduced veterinary expenses, and increased fish productivity, can make the investment worthwhile.

2.4. Toxicity, Safety, and Environmental Impact of Nanoparticle-Enhanced Fish Feed

While nanoparticle-enhanced fish feed offers numerous benefits and promising advancements in aquaculture, it is crucial to carefully evaluate its toxicity, safety, and the environmental impact of NPs.

2.4.1. Toxicity and Safety Issues

Nanoparticle-enhanced fish feed offers significant benefits but raises health concerns that need careful consideration. Studies show that NPs can impact fish health, potentially causing oxidative stress, inflammation, and altered behavior [133]. Although many NPs in fish feed are derived from essential nutrients and micronutrients derived from safe ingredients, the NP toxicity is influenced by factors such as particle size, shape, and exposure duration [134]. Due to their small size and high surface area-to-volume ratio, NPs can interact uniquely with biological systems [135], which may contribute to their distinct toxicity profile. For example, ZnONPs can cause oxidative stress and inflammation [136,137,138] more readily than bulk zinc-based feed additives. Similarly, SeNPs, although nutritionally superior to their bulk counterparts [139], can have adverse effects at non-optimal doses, including decreased sperm quality, increased oxidative stress, DNA damage in sperm, and disrupted testis development [140]. These potential risks underscore the need for the careful evaluation and management of NP use in fish feed to ensure both efficacy and safety.

The long-term effects of NP accumulation in fish tissues remain unclear, highlighting the need for thorough toxicological research even for NPs derived from safe ingredients. Additionally, the release of NPs into aquatic environments through excretion or feed waste could impact non-target organisms and disrupt ecological balance, affecting water quality and biodiversity [141].

Human health risks are also a concern, as residual NPs in fish may pose risks to consumers, necessitating rigorous safety testing. Variability in NP properties, such as size and surface charge, complicates safety predictions and requires careful consideration in regulatory frameworks [133,142].

On the positive side, the precise engineering of NPs for controlled nutrient and drug delivery can enhance bioavailability and therapeutic effectiveness while minimizing adverse effects. This targeted approach allows for lower dosages, reducing overall exposure and toxicity. Controlled release directs NPs to specific sites, minimizing unintended contact with sensitive tissues and preventing long-term toxic effects [143,144,145,146]. Overall, this method improves therapeutic benefits while managing toxicity effectively.

2.4.2. Bioaccumulation and Environmental Impact

The possible bioaccumulation and environmental impact of nanoparticle-enhanced fish feed raises significant concerns that necessitate detailed study for sustainable aquaculture. NPs can accumulate in fish tissues, potentially causing oxidative stress, inflammation, and other health issues that may affect growth and reproduction. For instance, ZnONPs may accumulate in fish tissues, posing long-term toxicity risks [147,148], unlike other bulky additives. These NPs can also be transferred through the food chain, posing risks to higher trophic levels, including humans [149].

When released into the environment through feed waste or excretion, NPs can affect non-target organisms and disrupt ecosystems. Their behavior in water is influenced by factors such as chemistry, temperature, and organic matter, which affect their toxicity and interactions with other pollutants [150]. The persistence of NPs in the environment poses a risk of chronic exposure with unknown ecological consequences [151,152,153].

To address these challenges, it is important to develop environmentally friendly NPs that degrade into non-toxic byproducts [154] and to implement controlled release mechanisms. The use of nutrients such as proteins, lipids, and carbohydrates to make NPs for fish feed is environmentally advantageous. These biocompatible nutrients can create NPs that degrade naturally in the environment, reducing the risk of persistence and accumulation. Additionally, nanoparticle-enhanced fish feed can reduce feed wastage and pollution by improving digestibility and nutrient absorption [155], which lowers waste excretion and decreases the organic load in aquaculture systems. This approach not only supports sustainable aquaculture practices but also contributes to minimizing nutrient runoff and water pollution [21,156]. The antimicrobial properties of NPs might reduce the need for antibiotics, mitigating resistance and reducing pharmaceutical residues in water bodies.

Implementing best management practices in aquaculture and establishing robust regulatory frameworks are crucial for the safe application of nanoparticles in fish feed. This includes the comprehensive testing of their properties, environmental impact, and effects on aquatic ecosystems and human health.

3. Conclusions and Future Perspectives

Nanoparticle-enhanced fish feed represents an innovative advancement in aquaculture that can potentially provide numerous benefits. However, despite the use of safe ingredients in NP production, the small size and high surface area-to-volume ratio of NPs can pose potentially toxic effects, necessitating comprehensive safety assessments.

Future research should focus on safety and environmental impact, regulation and standardization, targeted and controlled release, and integration with other technologies. Extensive studies are needed to assess the long-term safety of NPs, including their effects on fish health, human consumers, and the aquatic environment. Developing environmentally friendly and biodegradable nanoparticles is crucial. Establishing clear regulatory frameworks and standards will ensure safe and effective applications, including guidelines for nanoparticle synthesis, feed formulation, and usage protocols.

Advances in NP engineering should improve targeted and controlled release mechanisms to maximize nutrient bioavailability and therapeutic effects while minimizing adverse impacts on beneficial gut microbiota. Combining NP technology with probiotics, prebiotics, and plant-based ingredients can enhance fish health and growth, contributing to a sustainable and resilient aquaculture industry. Addressing these challenges and leveraging nanoparticles’ potential can significantly improve productivity, sustainability, and fish welfare, supporting global food security and environmental health.