Search Results (171)

Today, several conventional wastes (fly ash, ground granulated blast furnace slags, etc.) are used as valid precursors for geopolymer synthesis. However, there are several new wastes that can be studied to replace geopolymer precursors. This study investigates the behavior of four industrial wastes—suction dust (SW1), red mud (SW2), electro-filter dust (SW3), and extraction sludge (SW4)—as 20 wt.% substitutes for metakaolin in geopolymer synthesis. The objective is to assess how their incorporation before alkali activation affects the structural, thermal, mechanical, chemical, and antimicrobial properties of the resulting geopolymers, namely GPSW1–4. FT-IR analysis confirmed successful geopolymerization in all samples (the main Si-O-T band underwent redshift, confirming Al incorporation in geopolymer structures after alkaline activation), and stability tests revealed that none of the GPSW1–4 samples disintegrated under thermal or water stress. However, GPSW3 showed an increase in efflorescence phenomena after these tests. Moreover, compressive strength was reduced across all waste-containing geopolymers (from 22.0 MPa for GP to 12.6 MPa for GPSW4 and values lower than 8.1 MPa for GPSW1–3), while leaching tests showed that GPSW1 and GPSW4 released antimony (127.5 and 0.128 ppm, respectively) above the legal limits for landfill disposal (0.07 ppm). Thermal analysis indicated that waste composition influenced dehydration and decomposition behavior. The antimicrobial activity of waste-based geopolymers was observed against E. coli, while E. faecalis showed stronger resistance. Overall, considering leaching properties, SW2 and SW3 were properly entrapped in the GP structure, but showed lower mechanical properties. However, their antimicrobial activity could be useful for surface coating applications. Regarding GPSW1 and GPSW4, the former needs some treatment before incorporation, since Sb is not stable, while the latter, showing a good compressive strength, higher thermal stability, and leaching Sb value not far from the legal limit, could be used for the inner reinforcement of building materials. Full article

Multifunctional water-treatment materials urgently need to be developed to avoid normal organic matter, inorganic anions, resistant bacteria, and hazardous disinfection by-products in conventional drinking water treatment strategies. While quaternary ammonium pyridine resins (QAPRs) possess porous adsorption structures and incorporate antibacterial groups, enabling simultaneous water disinfection and purification, their limited bactericidal efficacy hinders broader utilization. Therefore, a deeper understanding of the structure-dependent antimicrobial mechanism in QAPRs is crucial for improving their antibacterial performance. Hexyl (C₆) was proved to be the optimal antibacterial alkyl in the QAPRs. A new antibacterial quaternary ammonium pyridine resin Py-61 was prepared by more surficial bactericidal N⁺ groups and higher efficient antibacterial hexyl, performing with the excellent antibacterial efficiency of 99.995%, far higher than the traditional resin Py-6C (89.53%). The antibacterial resin Py-61 completed the disinfection of sand-filtered water independently to produce safe drinking water, removing the viable bacteria from 3600 to 17 CFU/mL, which meets the drinking water standard of China in GB5749-2022 (<100 CFU/mL). Meanwhile, the contaminants in sand-filtered water were obviously removed by the resin Py-61, including anions and dissolved organic matter (DOM). The resin Py-61 can be regenerated by 15% NaCl solution, and keeps the reused antibacterial efficiency of >99.97%. As an integrated disinfection–purification solution, the novel antibacterial resin presents a promising alternative for enhancing safety in drinking water treatment. Full article

Background: Antimicrobial resistance (AMR) is a growing global health concern, driven in part by the environmental release of antimicrobial-resistant bacteria (ARB) and antimicrobial resistance genes (ARGs). Aquatic systems, particularly those exposed to urban, agricultural, and industrial activity, are recognized as hotspots for AMR evolution and transmission. In Chile, the Aconcagua River—subject to multiple anthropogenic pressures—offers a representative model for studying the environmental dimensions of AMR. Methods: Thirteen surface water samples were collected along the Aconcagua River basin in a single-day campaign to avoid temporal bias. Samples were filtered through 0.22 μm membranes and cultured on MacConkey agar, either unsupplemented or supplemented with ceftazidime (CAZ) or ciprofloxacin (CIP). Isolates were purified and identified using MALDI-TOF mass spectrometry. Antibiotic susceptibility was evaluated using the Kirby–Bauer disk diffusion method in accordance with CLSI guidelines. Carbapenemase activity was assessed using the Blue-Carba test, and PCR was employed for the detection of the bla_VIM, bla_KPC, bla_NDM, and bla_IMP genes. Results: A total of 104 bacterial morphotypes were isolated; 80 were identified at the species level, 5 were identified at the genus level, and 19 could not be taxonomically assigned using MALDI-TOF. Pseudomonas (40 isolates) and Aeromonas (25) were the predominant genera. No growth was observed on CIP plates, while 24 isolates were recovered from CAZ-supplemented media, 87.5% of which were resistant to aztreonam. Five isolates exhibited resistance to carbapenems; two tested positive for carbapenemase activity and carried the bla_VIM gene. Conclusions: Our results confirm the presence of clinically significant resistance mechanisms, including bla_VIM, in environmental Pseudomonas spp. from the Aconcagua River. These findings highlight the need for environmental AMR surveillance and reinforce the importance of adopting a One Health approach to antimicrobial stewardship and wastewater regulation. Full article

We have used a rapid, portable assay (Bacterisk) to determine the bacterial water quality along several inland waters in SW England. Water samples were compared by a conventional membrane filter and culture methods for faecal indicator bacteria (FIB; E. coli and enterococci) and endotoxin measurement by Bacterisk. The Bacterisk data, measured in near-real-time, correlate well with both E. coli and enterococci, but also allow the presence of potential pathogens of a non-faecal origin to be detected. The sensitivity was calculated to be 92.96% with a specificity of 46.3% for E. coli with an expanded uncertainty of 22.07% and an Endotoxin Risk detection limit of 25 units. The presence of Bacterisk detectable non-faecal pathogenic bacteria in the water samples was successfully confirmed by Illumina MiSeq sequencing followed by target species-specific qPCR. Sequencing showed the presence of pathogens including Pseudomonas aeruginosa, Salmonella typhi, Acinetobacter baumannii, Shigella spp., and Legionella spp. as well as antimicrobial resistance genes. Furthermore, the portable Bacterisk assay was able to acquire data on the water quality from different locations and at different time points, providing a comprehensive surveillance tool that challenges the time to results by conventional methods (minutes instead of days), yielding compatible results. Full article

Background: Nowadays, the microbial degradation of cellulose represents a new perspective for reducing cellulose waste from industry and households and at the same time obtaining energy sources. Methods: We isolated and enriched two aerobic (at 37 °C and 50 °C) and one anaerobic microbial consortium from an anaerobic bioreactor for biogas production by continuous subculturing on peptone cellulose solution (PCS) medium supplemented with 0.3% treated or untreated Whatman filter paper under static conditions. Samples were taken every 7 days until day 21 to determine the percentage of cellulose biodegradation. We determined the antimicrobial resistance of aerobic and anaerobic consortia and some single colonies by disc diffusion method, against 42 clinically applied antibiotics. PCR analyses were performed to search for the presence of eight genes for cellulolytic activity and nine genes for antibiotic resistance. By metagenomics analysis, the bacterial and fungal genus distributions in the studied populations were determined. Results: Aerobes cultured at 50 °C degraded cellulose to the greatest extent (47%), followed by anaerobes (24–38%) and aerobes (8%) cultured at 37 °C. The bacterial sequence analysis showed that the dominant phyla are Bacillota and Bacteroidetes and genera—Paraclostridium, Defluvitalea, Anaerobacillus, Acetivibrio, Lysinibacillus, Paenibacillus, Romboutsia, Terrisporobacter, Clostridium, Sporanaerobacter, Lentimicrobium, etc. in a different ratio depending on the cultivation conditions and the stage of the process. Some of these representatives are cellulolytic and hemicellulolytic microorganisms. We performed lyophilization and proved that it is suitable for long-term storage of the most active consortium, which degrades even after the 10th re-inoculation for a period of one year. We proved the presence of ssrA, ssrA BS and blaTEM genes. Conclusions: Our findings demonstrated the potential utility of the microbial consortium of anaerobes in the degradation of waste lignocellulose biomass. Full article

Antibacterial filter materials have been effectively utilized for controlling biological contaminants and purifying indoor air, with the market for such materials experiencing continuous expansion. Currently, textile antibacterial testing standards are widely adopted to evaluate the antimicrobial efficacy of filter materials, yet no dedicated assessment protocols specifically tailored for filtration media have been established. This study aims to investigate the applicability of textile antibacterial testing methods to high-efficiency glass fiber filter materials (filtration efficiency > 99.9%), as well as to explore the factors that affect the rate of bacterial elution from high-efficiency glass fiber filter materials. By referencing the textile antibacterial testing standard (absorption method), significant discrepancies in bacterial recovery counts were observed between the high-efficiency glass fiber materials and the various textile control samples, with the former exhibiting a markedly lower recovery rate (approximately 10%). Pore structure and wettability analyses revealed the underlying causes of these differences. To ensure the accuracy of the antibacterial evaluation results, the effects of oscillation elution parameters (time and intensity) and material incubation conditions (duration, sealing and humidity) on bacterial recovery rates in glass fiber filter materials were systematically investigated to optimize the elution methodology. The results indicate that specimen type, size, elution method, incubation duration (4 h or 24 h), sealing conditions, and environmental humidity (10% or 30%, 60% and 95% RH) collectively influence bacterial recovery efficiency. The highest recovery efficiency (55%) was achieved when the filter materials were incubated in a sealed environment with humidity maintained at ≥60% RH. These findings emphasize the critical need to establish clear and specialized antibacterial performance testing standards for filter materials. The study provides essential guidance for developing material-specific evaluation protocols to ensure a reliable and standardized assessment of antimicrobial efficacy in high-efficiency filtration systems. Full article

Integrating soft components into denture design may significantly enhance the comfort of edentulous patients. Microorganisms, particularly Candida albicans, often colonize soft denture lining materials, which can release metabolic and toxic byproducts linked to the development of Denture-Induced Stomatitis. This study aimed to evaluate the effectiveness of antimicrobial agents incorporated into soft denture liners in inhibiting the adhesion and colonization of C. albicans. A systematic review was conducted through MEDLINE-Pubmed, EMBASE, and the Cochrane Central Register of Controlled Trials. A range of keywords was employed without applying a time filter to identify relevant literature. The review revealed many studies investigating various antimicrobial compounds added to different soft denture liner materials, all demonstrating the ability to inhibit the proliferation of C. albicans. All the antimicrobial agents examined exhibited a significant antifungal effect, with minimal to negligible impact on the physical properties of the denture liners. However, it was noted that the mechanical properties of the liners were modified in direct correlation to the concentration of the antimicrobial agents utilized. The successful incorporation of these agents into various soft denture liners has been documented, with nystatin being the primary pharmacological agent identified across multiple studies. While incorporating antibacterial agents was deemed successful, it is essential to note that the methodologies employed yielded varying effects on the overall performance of the soft-liner materials. Full article

Cosmetic products contain numerous metals used as pigments, UV filters, preservatives, antiperspirants and antimicrobial agents, which are responsible for allergic skin reactions, with the most common being nickel. To reduce skin penetration of Ni, innovative pharmaceutical formulations such as lipogels with chelating action against the metal ions themselves can be used. Chelation therapy allows a chelating agent to combine with metal ions to form a stable ring structure called a chelate. The chelate structure is more soluble in water than the toxic metal, which facilitates removal of the toxic metal from the tissue and its excretion by the kidneys. The aim of the following work was to evaluate the chelating properties against nickel ions of different types of lipogels containing flavonoids such as resveratrol and epigallocatechin gallate with chelating activities largely dependent on the number and position of their hydroxyl groups. The results obtained showed that lipogels based on epigallocatechin gallate show high chelating action against nickel, especially at low concentrations. In addition, rheological studies showed an ideal profile to ensure viscoelasticity and swelling of the lipogel within 48 h, confirming reports of 75% epigallocatechin release from the lipogel after 48 h. Tests have shown that lipogels based on epigallocatechin gallate have high chelating action against nickel, especially at low concentrations. Full article

The healthy gut masks a dynamic balance between pro- and anti-inflammatory activities, largely due to microbial factors in the lumen. IL-10 is vital among the anti-inflammatory mediators, yet confirming constitutive versus stimulated secretion in any cell type is difficult due to the cellular complexity in the gut. Seeking to determine whether intestinal epithelial cells are programmed to constitutively make IL-10, we confirmed that IL-10 mRNA was present in enteroids from C57BL/6 mice and IL-10 protein was co-localized with a Paneth cell marker but not with markers for goblet or tuft cells. Paneth cells positive for IL-10 also possessed apical and basal IL-10RA, while cells negative for IL-10 had only basal IL-10RA, suggesting a possible autocrine role for IL-10. Indeed, Paneth cells in IL-10 gene knockout (IL-10KO) enteroids possessed lower levels of anti-microbial protein mRNAs, which could not be restored by adding IL-10. Enteroids passaged onto Transwell^® filters to form monolayers were treated with IL-10 and STAT3 phosphorylation was measured. Apically applied IL-10 resulted in a stronger STAT3 signal than basally applied cytokine. Our results indicate that a subpopulation of Paneth cells constitutively secrete IL-10 apically, which binds apical IL-10RA, impacting the expression of anti-microbial proteins unique to Paneth cells. Full article

The Thymus vulgaris and Origanum vulgare essential oils (contained thymol and carvacrol in a range of 35–80%) are used in various products in the fields of medicine, cosmetics, and foods. Molecular hybridization between benzothiazole (BT) and phenolic monoterpenoids is a promising method for the development of biologically active compounds. New benzothiazole–monoterpenoid hybrids were synthesized through a regioselective α-amidoalkylation reaction of thymol and carvacrol with high yields (70–96%). This approach is both simple and cost-effective, employing easily accessible and inexpensive reagents to produce target molecules. The structure of the synthesized compounds was characterized spectrally using ¹H-, ¹³C-NMR, FT-IR, and HRMS data. The newly obtained compounds are structural analogues of the UVB filter PBSA, which is used in cosmetics. The spectral properties of the aromatic products thymol hybrid (2-(4-hydroxy-5-isopropyl-2-methylphenyl)benzo[d]thiazole) and carvacrol hybrid (2-(4-hydroxy-2-isopropyl-5-methylphenyl)benzo[d]thiazole) were successfully examined, using a validated spectrophotometric method. SPF values varied from 31 to 36, compared to the PBSA (30), and were observed at concentrations of 1–0.25 mM. 2-Hydroxyphenylbenzothiazoles are known antimicrobial and antioxidant agents that have potential applications in the food industry and cosmetics as preservatives and antioxidants. In this context, antimicrobial activity of the hybrid compounds was evaluated using the agar diffusion method against E. coli, S. aureus, P. aeruginosa, and C. albicans. Compounds of methyl-2-(4-hydroxy-2-isopropyl-5-methylphenyl)benzo[d]thiazole-3(2H)-carboxylate containing carvacrol fragments showed high activity against Staphylococcus aureus ATCC 25923 (with 0.044 μmol content). The radical scavenging activity was determined using ABTS and DPPH assays, the highest activity was exhibited by the thymol hybrids ethyl-2-(4-hydroxy-5-isopropyl-2-methylphenyl)benzo[d]thiazole-3(2H)-carboxylate (IC₅₀—133.70 ± 10 µM) and methyl-2-(4-hydroxy-5-isopropyl-2-methylphenyl)benzo[d]thiazole-3(2H)-carboxylate (IC₅₀—157.50 ± 10 µM), defined by ABTS. The aromatic benzothiazole–monoterpenoid hybrids are classified using in silico analyses as non-mutagenic, with low toxicity, and they are non-irritating to the skin. These compounds were identified as new hit scaffolds for multifunctional molecules in cosmetics. Full article

The idea supporting the investigation of the current manuscript was to develop customized filters for air conditioners with different pore percentages and geometry with the additional advantage of presenting antibacterial performance. This property was expected due to the reinforcement of Cu nanoparticles in the polymeric matrix of poly(lactic acid) (PLA) and polyurethane (TPU). The filaments were characterized by their chemical composition, thermal and mechanical properties, and antibacterial behavior before and after processing by fused filament fabrication. An X-ray photoelectron spectroscopy showed that the nanocomposite filaments presented Cu particles at their surface in different valence states, including Cu⁰, Cu⁺, and Cu²⁺. After processing, the metallic particles are almost absent from the surface, a result confirmed by micro-computer tomography (μ-CT) characterization. Antibacterial tests were made using solid-state diffusion tests to mimic the dry environment in air conditioner filters. The tests with the nanocomposite filaments showed that bacteria proliferation was hindered. However, no antibacterial performance could be observed after processing due to the absence of the metallic element on the surface. Nevertheless, antimicrobial performance was observed when evaluated in liquid tests. Therefore, the obtained results provide valuable indications for developing new nanocomposites that must maintain their antimicrobial activity after being processed and tested in the dry conditions of solid-state diffusion. Full article

Face masks are essential pieces of personal protective equipment for preventing inhalation of airborne pathogens and aerosols. Various face masks are used to prevent the spread of virus contamination, including blue surgical and N95 filtering masks intended for single use. Traditional face masks with self-sanitisation features have an average filtration efficiency of 50% against airborne viruses. Incorporating nanomaterials in face masks can enhance their filtration efficiency; however, using nanomaterials combined with thermal heaters can offer up to 99% efficiency. Bacterial contamination is reduced through a self-sterilisation method that employs nanomaterials with antimicrobial properties and thermoregulation as a sanitisation process. By combining functional nanomaterials with conductive and functional polymeric materials, smart textiles can sense and act on airborne viruses. This research evaluates the evidence behind the effectiveness of nanomaterials and thermoregulation-based smart textiles used in self-sanitising face masks, as well as their potential, as they overcome the shortcomings of conventional face masks. It also highlights the challenges associated with embedding textiles within nanomaterials. Finally, it makes recommendations regarding safety, reusability, and enhancing the protection of the wearer from the environment and underscores the benefits of reusable masks, which would otherwise pollute the environment. These self-sanitising face masks are environmentally sustainable and ideal for healthcare, the food industry, packaging, and manufacturing. Full article

Klebsiella pneumoniae is a Gram-negative bacillus responsible for a wide variety of potentially fatal infections and, in turn, constitutes a critical agent of healthcare-associated infections. Moreover, K. pneumoniae is characterized by multi-drug-resistant (MDR) bacteria, such as extended-spectrum beta-lactamases (ESBL) and carbapenemase (KPC) producer strains, representing a significant health problem. Because resistances make it difficult to eradicate using antibiotics, antimicrobial photodynamic therapy (aPDT) promises to be a favorable approach to complementing conventional therapy against MDR bacteria. This study aims to provide relevant bibliographic information on the state of the art of application of aPDT against K. pneumoniae and MDR K. pneumoniae. Our methodology follows a protocol using the PRISMA extension for scoping reviews (PRISMA-ScR) guidelines, and the search consults the PubMed (MESH), Google Scholar, and Scopus databases from January 2012 to September 2024. The eligibility criteria were (1) original articles after 2012 referring to antimicrobial photodynamic activity in K. pneumoniae in vitro and in vivo: clinical applications and synergism with antibiotics, other antimicrobial drugs, or PS coupled to other particles, (2) articles in English, and (3) articles peer-reviewed. Results. Following two independent searches in databases, 298 records were found. After applying eligibility criteria and various filters, such as removing duplicates, 25 studies were included in this review. The evidence demonstrates the effectiveness of aPDT in vitro in eradicating sensitive or MDR-K. pneumoniae strains, including strains producing biofilms, ESBL, and KPC. Finally, it is concluded that aPDT is a recommended antimicrobial therapy, but more research in vivo is needed to support studies in humans. Full article

Microbial attack, particularly fungal degradation of cellulose, is a leading cause of paper damage. To address fungal spores and the rising concern of microbial drug resistance, a nano-Germanium dioxide (GeO₂)/cetyltrimethylammonium bromide (CTAB) complex (nano-GeO₂/CTAB complex) with potent antibacterial properties was synthesized. Its inhibitory effects were evaluated against bacteria, including Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, as well as fungi isolated from paper (Fusarium spp., Aspergillus spp., and Penicillium citrinum). The nano-GeO₂/CTAB complex exhibited significant (p < 0.05) inhibitory effects against S. aureus and E. coli. Moreover, a 60 min treatment with 1 mg/mL of the complex significantly inhibited the growth of all tested fungi and reduced their biomass after five days of culture, while 4 mg/mL completely deactivated spores. Filter paper pre-treated with the nano-GeO₂/CTAB complex showed complete resistance to microbial attack, exhibiting no fungal growth and a clear inhibition zone devoid of bacterial growth. In contrast, untreated controls displayed fungal coverage exceeding 95% within five days. These findings highlight the nano-GeO₂/CTAB complex as a promising antimicrobial agent for protecting paper materials from microbial degradation. Full article

The simple oxides like titania, zirconia, and ZnO are famous with their antibacterial (or even antimicrobial) properties as well as their biocompatibility. They are broadly used for air and water filtering, in food packaging, in medicine (for implants, prostheses, and scaffolds), etc. However, these application fields can be broadened by switching to the composite multicomponent compounds (for example, titanates) containing in their unit cell, together with oxygen, several different metallic ions. This review begins with a description of the synthesis methods, starting from wet chemical conversion through the manufacturing of oxide (nano)powders toward mechanosynthesis methods. The morphology of these multicomponent oxides can also be very different (like thin films, complicated multilayers, or porous scaffolds). Further, we discuss in vitro tests. The antimicrobial properties are investigated with Gram-positive or Gram-negative bacteria (like Escherichia coli or Staphylococcus aureus) or fungi. The cytotoxicity can be studied, for example, using mouse mesenchymal stem cells, MSCs (C3H10T1/2), or human osteoblast-like cells (MG63). Other human osteoblast-like cells (SaOS-2) can be used to characterize the cell adhesion, proliferation, and differentiation in vitro. The in vitro tests with individual microbial or cell cultures are rather far away from the real conditions in the human or animal body. Therefore, they have to be followed by in vivo tests, which permit the estimation of the real applicability of novel materials. Further, we discuss the physical, chemical, and biological mechanisms determining the antimicrobial properties and biocompatibility. The possible directions of future developments and novel application areas are described in the concluding section of the review. Full article