Immobilized silver nanoparticles enhance contact killing and show highest efficacy: elucidation of the mechanism of bactericidal action of silver

From adhesion to biofilms formation and resilience: Exploring the impact of silver nanoparticles-based biomaterials on Pseudomonas aeruginosa

Colonization of medical devices by microorganisms, often progressing to the formation of resilient biofilms, presents a common clinical issue. To address this challenge, there is growing interest in developing novel biomaterials with antimicrobial/antibiofilm properties as a promising preventive measure. This study explores nanocomposite biomaterials based on silver nanoparticles (AgNPs) deposited on thin silica (SiO2) layers for their potential effect on the adhesion, detachment, viability and biofilm formation of the opportunistic Pseudomonas aeruginosa. The AgNPs-based biointerface effect on biofilm development is investigated on the PAO1-Tn7-gfp strain by combining experiments under static and dynamic conditions. For the latter, a shear-stress flow chamber is used to mimic conditions encountered around certain medical devices. The findings reveal a rapid bactericidal effect of the AgNPs, noticeable within 30 min of exposure. Moreover, a delay in surface colonization is observed with a thin and unstructured biofilm, even after 72h of dynamic culture. A considerable fragility and sensitivity to hydrodynamic stresses is noticed for this loosely attached bacterial monolayer when compared with the thick and resilient biofilm formed on SiO2 surface. This study underlines the potential of AgNPs-based biomaterials in the conception of novel antimicrobial/antibiofilm surfaces with controlled release of the biocidal agent.

Femtosecond Laser-Engineered β-TCP Scaffolds: A Comparative Study of Green-Synthesized AgNPs vs. Ion Doping Against S. aureus for Bone Regeneration

Implant-associated infections, particularly those linked to Staphylococcus aureus (S. aureus), continue to compromise the clinical success of β-tricalcium phosphate (β-TCP) implants despite their excellent biocompatibility and osteoconductivity. This investigation aims to tackle these challenges by integrating femtosecond (fs)-laser surface processing with two complementary strategies: ion doping and functionalization with green-synthesized silver nanoparticles (AgNPs). AgNPs were produced via fs-laser photoreduction using green tea leaf extract (GTLE), noted for its anti-inflammatory and antioxidant properties. Fs-laser processing was applied to modify β-TCP scaffolds by systematically varying scanning velocities, fluences, and patterns. Lower scanning velocities generated organized nanostructures with enhanced roughness and wettability, as confirmed by scanning electron microscopy (SEM), optical profilometry, and contact angle measurements, whereas higher laser energies induced significant phase transitions between hydroxyapatite (HA) and α-tricalcium phosphate (α-TCP), as revealed by X-ray diffraction (XRD). AgNP-functionalized scaffolds demonstrated markedly superior antibacterial activity against S. aureus compared to the ion-doped variants, attributed to the synergistic interplay of nanostructure-mediated surface disruption and AgNP-induced bactericidal mechanisms. Although ion-doped scaffolds exhibited limited direct antibacterial effects, they showed concentration-dependent activity in indirect assays, likely due to controlled ion release. Both strategies promoted osteogenic differentiation of human bone marrow mesenchymal stem cells (hBM-MSCs) under defined conditions, albeit with transient cytotoxicity at higher fluences and excessive ion doping. Overall, this approach holds promise for markedly improving antibacterial efficacy and osteogenic compatibility, potentially transforming bone regeneration therapies.

One-Pot Colorimetric Nucleic Acid Test Mediated by Silver Nanoparticles for DNA Extraction and Detection

This study introduces a one-pot colorimetric nucleic acid test (NAT) platform that integrates silver nanoparticle (AgNP)-based DNA isolation and colorimetric detection of bacterial genes. The NAT platform is comprised with purification and reaction units that enable cell lysis, DNA purification, loop-mediated isothermal amplification (LAMP), and colorimetric detection. In the purification unit, polyethyleneimine (PEI)-capped AgNPs were used as cell lysis agents because of their cell-disrupting and antimicrobial properties and were immobilized on a glass fiber membrane for DNA capture and isolation. The reaction unit enabled colorimetric detection of DNA amplicons, achieved by the synthesis of AgNPs on chromatography paper formed via the reduction of silver ions present on the paper, mediated by the use of sodium ascorbate, a reducing agent, present in the LAMP reagent, after the reaction. AgNPs were formed only in the presence of the target amplicons in the positive samples after reaction at 65 °C for 5 min. Bacterial DNA was efficiently extracted using this method, and Enterococcus faecium was detected with a detection limit of 102 CFU/mL. This platform is a promising alternative for rapid and cost-effective nucleic acid testing in resource-limited settings.

Comparative efficacy of sodium hypochlorite, silver nanoparticles, and chitosan nanoparticles on gutta-percha cone disinfection and topographical changes analyzed by atomic force microscopy: An in vitro study

Context

Evaluation of newer nanoparticle-based disinfectants for the disinfection of contaminated gutta-percha cones and surface topographical changes induced by them.

Aim

To evaluate the effectiveness of sodium hypochlorite (NaOCl), silver nanoparticles (AgNPs) solution, and chitosan nanoaparticles (ChNPs) solution for the disinfection of gutta-percha cones contaminated with Bacillus subtilis (MTCC 441) and Candida albicans (MTCC 227) and the topographical changes induced by them.

Methods

Minimum inhibitory concentration and minimum bactericidal concentration of NaOCl, AgNPs, and ChNPs against B. subtilis and C. albicans were determined by the broth microdilution method and colony-forming unit assay, respectively. Gutta-percha cones were artificially contaminated with B. subtilis and C. albicans. Contaminated cones were immersed for 1, 3, and 5 min in 2.62% NaOCl, 5.25% NaOCl, 250 µg/ml AgNP's, and 625 µg/ml ChNPs solution, and the mean colony-forming units (CFUs) were evaluated after disinfection. Topographical changes induced by these agents at different time intervals were assessed by atomic force microscopy (AFM).

Statistical Analysis

The data were analyzed by a two-way analysis of variance and Bonferroni post hoc test performed using licensed GraphPad Prism (v5.0).

Results

NaOCl was the most effective disinfectant, eliminating both microorganisms within 1 min of immersion time. AgNPs and ChNPs showed no CFU units at 5 min of immersion time against B. subtilis but were able to eliminate C. albicans within 1 min of immersion. AFM analysis showed that, with all disinfectants on increasing time of immersion, the topographical changes become significant in comparison to the control.

Conclusion

NaOCl at both concentrations was the most effective disinfectant, causing minimal topographical alterations at 1 min of immersion time.

One-Step Nanoimprinting of Fe2O3/AgBr Thin Films for Dark-Light Active Antibiofilm and Bacterial-Free Cell Culture Surfaces

The resuscitation of bacteria through biofilms presents a critical challenge in controlling microbial pathogenesis and addressing antimicrobial resistance. Continuous antibiofilm activity, particularly on frequently contacted surfaces, is therefore critical. In this study, a scalable is introduced, one-step fabrication of Fe2O3/AgBr nanoimprints using a polymerizable sol-gel (PSG) approach to create functional nanostructured thin films with strong antimicrobial properties. Fe2O3, a visible-light photocatalyst, is coupled with AgBr, a photosensitizer and dark-active antimicrobial, forming a heterojunction that demonstrated potent antibacterial activity against Escherichia coli and Pseudomonas putida under both dark and light conditions. The heterojunctions exhibit significant biofilm inhibition in the dark, particularly against the robust biofilm-forming P. putida, while visible light irradiation ensures complete biofilm clearance. These surfaces also achieve optimal reactive oxygen species (ROS) production, selectively targeting bacteria without compromising the integrity of mammalian cells. The biocompatibility is confirmed through MTT, TBARS, and apoptosis assays, demonstrating the non-cytotoxic nature of the substrates. Moreover, the surfaces enable cell patterning and recovery of mammalian cells from microbial contamination, highlighting their potential in creating bacterial-free environments for cell culture. This innovative method offers a promising route to next-generation, self-cleaning antimicrobial coatings, combining continuous biofilm inhibition with excellent biocompatibility and scalability.

Synergistic effect of nanosilver fluoride with L-arginine on remineralization of early carious lesions

The synergistic effect of nanosilver fluoride (NSF) with L-arginine on early carious lesions was evaluated. NSF was synthesized from chitosan, acetic acid, silver nitrate, sodium borohydride, and sodium fluoride. NSF + Arg was synthesized by adding L-arginine. After demineralization the enamel slabs from extracted molar, remineralization agents were applied by randomly dividing them into five groups (n = 15): sodium fluoride varnish (NaF), silver diamine fluoride (SDF), NSF, NSF + Arg, and control. The surface microhardness (SMH), remineralization effects using microcomputed tomography and color changes using a spectrophotometer were measured before and after pH cycling. SMH was analyzed by Kruskal-Wallis test with Dunn's test. Remineralization effects, and color changes were analyzed using the one-way analysis of variance with Duncan's test; p-value < 0.05 was considered significant. SMH recovered to similar levels in all groups (p > 0.05), except in the control group after pH cycling. The NSF + Arg and SDF groups showed a higher remineralization than the NaF and NSF groups (p < 0.05). SDF caused the largest discoloration (p < 0.05). The other groups showed no difference in discoloration. NSF + Arg could be an alternative to SDF given its ability to remineralize early caries lesions without discoloration.

Thermo-responsive/anti-biofouling chitosan hydrogel beads in situ decorated with silver nanoparticles for water disinfection

The development of a sustainable and eco-friendly silver-based hybrid nanocomposite for safe and efficient point-of-use (POU) water disinfection remains a challenge. Herein, a simple and facile approach was proposed for the in situ immobilization of silver nanoparticles (AgNPs) on chitosan-g-poly (sulfobetaine methacrylate) (CS-g-PSBMA) hydrogel beads, which have been achieved via graft copolymerization of sulfobetaine methacrylate along the chitosan chains followed by a drop method. The AgNPs-decorated CS-g-PSBMA hydrogel beads were characterized and their bactericidal efficacy towards Escherichia coli was evaluated concurrently with their anti-biofouling behaviors. The results indicated that the grafted PSBMA hydrogels on CS would not only enhance the immobilization of more AgNPs (122.63 mg/g material), but also restricted the silver release (only 0.015 % after the 14th day of incubation), which surpassed numerous other AgNPs-based nanocomposites for water disinfection. Moreover, the release of silver can be modulated by altering the temperature due to the thermosensitivity of PSBMA, and the maximum concentration of silver leaching in the effluent was 33.1-52.3 μg/L at 25-60 °C. Importantly, the synthesized AgNPs-based CS-g-PSBMA can exert both exceptional bactericidal and superior anti-biofouling capabilities as well as reusability features, indicating sustained antibacterial effectiveness and significant potential for practical applications in water disinfection.

Mode of action of silver-based perovskite against Gram-negative bacteria

Although silver is known for its antibacterial activity, its exact mode of action remains unclear. In our previous work, we described AgNbO3 nanoparticles (AgNbO3 NPs) prepared using a ceramic method, followed by high-energy and low-energy ball-milling processes, which exhibited antimicrobial activity with negligible release of Ag+ in deionized water. Here, we investigated thoroughly the mode of action of these AgNbO3 NPs against Escherichia coli. Drastic morphological changes in E. coli were observed after their exposure to AgNbO3 NPs. In addition to cellular damage, AgNbO3 NPs induced the production of reactive oxygen species and lipid peroxidation, likely following the release of small amounts of Ag+. This was concluded from the characterization of mutants resistant to AgNbO3 NPs that showed cross-resistance to AgNO3, impaired reactive oxygen species production and lipid peroxidation, and harbored a key mutation in a two-component regulatory system regulating an Ag+ efflux pump. We calculated, however, that the quantity of Ag+ released from AgNbO3 NPs is not sufficient by itself to lead to bacterial death. We propose that bacterial contact with the AgNbO3 NPs in combination with Ag+ release is necessary for the mode of action of AgNbO3 NPs.IMPORTANCESilver is known for its antibacterial activity, but its exact mode of action remains unclear. Here, we investigated thoroughly the mode of action of AgNbO3 nanoparticles against Escherichia coli. Our data suggest that AgNbO3 nanoparticles have dual effects on the cell and that both are required for its lethal action.

Tuning antibacterial efficacy against Pseudomonas aeruginosa by using green AgNPs in chitosan thin films as a plastic alternative

Nanotechnology advancements have facilitated the development of eco-friendly strategies to combat bacterial infections caused by antibiotic-resistant pathogens. This study promotes a green method for the synthesis of silver nanoparticles (AgNPs) utilizing Eucalyptus globulus leaf extracts as an alternative to traditional colloidal AgNPs obtained through chemical synthesis, investigating their antibacterial efficacy against Pseudomonas aeruginosa and their impact on the expression of bacterial virulence factors (pyocyanin, pyoverdine, rhamnolipids). This work demonstrates that: i. while colloidal AgNPs showed ineffective up to 120 μM, green AgNPs had a bactericidal effect already at 20 μM, without impacting bacterial virulence factors at sub-inhibitory concentrations; ii. the polyphenolic shell surrounding green AgNPs could play a crucial role in the antibacterial mechanisms, with a pro-oxidant action confirmed by a greater sensitivity to hydrogen peroxide (H2O2); iii. AgNPs improved the antibacterial properties of chitosan when incorporated into thin films. Consequently, an environmentally friendly nanocomposite film with antibacterial and antibiofilm properties was produced, which holds promise for application in food packaging to mitigate the emergence of microbial contamination in food products.

Eco-friendly synthesis of silver nanoparticles by Trigonella foenum-graecum: formulations, characterizations, and application in wound healing

BACKGROUND

Due to the toxicity and serious side effects of chemical incorporated in topical dosage form used for treatment of wound healing, there is a need to use natural preparation as wound healing preparation.

AIMS

Seeds of Trigonella foenum-graecum (TFG) are used to synthesize eco-friendly silver nanoparticles (SNPs) in an appropriate way to heal wounds.

METHODS

To synthesize SNPs, TFG was incubated with AgNO3 to produce SNP-TFG. The obtained SNP-TFG was characterized for their wavelength, size and ζ-potential, surface morphology, and yield production. Then, SNP-TFG was formulated as a topical cream (O/W), characterized, and applied to the rats' groups to examine its wound-healing activity. Finally, a skin biopsy was performed to assess all rats' immunostaining and histopathological (HP) alterations in skin lesions on days 3, 7, 10, and 14.

RESULTS

The prepared SNP-TFG showed non-aggregated nano-formulation, with a λmax of 396 nm. SNP-TFG recorded a size of 43.65 ± 2.1 nm, a charge of -15.03 ± 3.2 mV, and showed yield of 52.61 ± 1.41% while the release was continued for more than 12 h. During the biosynthesis process, the compounds present in TFG are capable of reducing silver ions (Ag+) to form SNPs. SNP-TFG cream showed a pH nearly equal to the skin's pH, with suitable viscosity and homogeneity and an apparent permeability of 0.009 ± 0.001. Further, the HP of the SNP-TFG showed a substantial reduction in wound mass, wound granulation tissue growth enhancement, and epidermal re-epithelialization (proliferation) compared to the control group.

CONCLUSION

The obtained SNP-TFG is considered a novel skin wound-healing natural and eco-friendly nano-formulation.

Antimicrobial Activity of Amino-Modified Cellulose Nanofibrils Decorated with Silver Nanoparticles

Silver nanoparticles (Ag NPs) conjugated with amino-functionalized cellulose nanofibrils (NH2-CNFs) were in situ-prepared by reducing silver ions with free amino groups from NH2-CNFs. The spectroscopy and transmission electron microscopy measurements confirmed the presence of non-agglomerated nanometer-in-size Ag NPs within micrometer-large NH2-CNFs of high (20 wt.-%) content. Although the consumption of amino groups during the formation of Ag NPs lowers the ζ-potential and surface charge of prepared inorganic-organic hybrids (from +31.3 to +19.9 mV and from 2.4 to 1.0 mmol/g at pH 7, respectively), their values are sufficiently positive to ensure electrostatic interaction with negatively charged cell walls of pathogens in acidic and slightly (up to pH ~8.5) alkaline solutions. The antimicrobial activity of hybrid microparticles against various pathogens (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans) is comparable with pristine NH2-CNFs. However, a long-timescale use of hybrids ensures the slow and controlled release of Ag+ ions to surrounding media (less than 1.0 wt.-% for one month).

Biogenic Synthesis of Silver Nanoparticles Mediated by Aronia melanocarpa and Their Biological Evaluation

In the present study, two A. melanocarpa berry extracts were used for the synthesis of silver nanoparticles (AgNPs). After the optimization of synthesis, the AgNPs were characterized using UV-Vis, FTIR, EDX, DLS, and STEM analyses. The stability in different media, phytotoxicity, as well as antimicrobial and antioxidant activities were also evaluated. The ideal synthesis conditions were represented by a 3 mM AgNO3 concentration, 1:9 extract:AgNO3 volume ratio, alkaline medium, and stirring at 40 °C for 120 min. The synthesis was confirmed by the surface plasmon resonance (SPR) peak at 403 nm, and the strong signal at 3 keV from the EDX spectra. FTIR analysis indicated that polyphenols, polysaccharides, and amino acids could be the compounds responsible for synthesis. Stability tests and the negative zeta potential values showed that phytocompounds also play a role in the stabilization and capping of AgNPs. The preliminary phytotoxicity studies on T. aestivum showed that both the extracts and their corresponding AgNPs had an impact on the growth of roots and shoots as well as on the microscopic structure of leaves. The synthesized AgNPs presented antimicrobial activity against S. aureus, E. coli, and C. albicans. Moreover, considering the results obtained in the lipoxygenase inhibition, the DPPH and hydroxyl scavenging activities, and the ferrous ion chelating assay, AgNPs exhibit promising antioxidant activity.

A Highly Sensitive Chitosan-Based SERS Sensor for the Trace Detection of a Model Cationic Dye

The rapid detection of contaminants in water resources is vital for safeguarding the environment, where the use of eco-friendly materials for water monitoring technologies has become increasingly prioritized. In this context, the role of biocomposites in the development of a SERS sensor is reported in this study. Grafted chitosan was employed as a matrix support for Ag nanoparticles (NPs) for the surface-enhanced Raman spectroscopy (SERS). Chitosan (CS) was decorated with thiol and carboxylic acid groups by incorporating S-acetyl mercaptosuccinic anhydride (SAMSA) to yield CS-SAMSA. Then, Ag NPs were immobilized onto the CS-SAMSA (Ag@CS-SAMSA) and characterized by spectral methods (IR, Raman, NIR, solid state 13C NMR with CP-MAS, XPS, and TEM). Ag@CS-SAMSA was evaluated as a substrate for SERS, where methylene blue (MB) was used as a model dye adsorbate. The Ag@CS-SAMSA sensor demonstrated a high sensitivity (with an enhancement factor ca. 108) and reusability over three cycles, with acceptable reproducibility and storage stability. The Raman imaging revealed a large SERS effect, whereas the MB detection varied from 1-100 μM. The limits of detection (LOD) and quantitation (LOQ) of the biocomposite sensor were characterized, revealing properties that rival current state-of-the-art systems. The dye adsorption profiles were studied via SERS by fitting the isotherm results with the Hill model to yield the ΔG°ads for the adsorption process. This research demonstrates a sustainable dual-function biocomposite with tailored adsorption and sensing properties suitable for potential utility in advanced water treatment technology and environmental monitoring applications.

Surface-mediated fluorescent sensor array for identification of gut microbiota and monitoring of colorectal cancer

The development of efficient, accurate, and high-throughput technology for gut microbiota sensing holds great promise in the maintenance of health and the treatment of diseases. Herein, we developed a rapid fluorescent sensor array based on surface-engineered silver nanoparticles (AgNPs) and vancomycin-modified gold nanoclusters (AuNCs@Van) for gut microbiota sensing. By controlling the surface of AgNPs, the recognition ability of the sensor can be effectively improved. The sensor array was used to successfully discriminate six gut-derived bacteria, including probiotics, neutral, and pathogenic bacteria and even their mixtures. Significantly, the sensing system has also been successfully applied to classify healthy individuals and colorectal cancer (CRC) patients rapidly and accurately within 30 min, demonstrating its clinically relevant specificity.

Ultrasound-Driven Deposition of Au and Ag Nanoparticles on Citrus Pectin: Preparation and Characterisation of Antimicrobial Composites

Pectin is a renewable, non-toxic and biodegradable polymer made of galacturonic acid units. Its polar groups make it suitable for complexing and supporting metallic nanoparticles (NPs). This work aimed to produce antibacterial nanocomposites using pectin and acoustic cavitation. The metal NPs (Au or Ag) were deposited using ultrasound (US, 21 kHz, 50 W) and compared with those achieved with mechanical stirring. The impact of the reducing agents (NaBH4, ascorbic acid) on the dispersion and morphology of the resulting NPs was also assessed. Characterization by diffuse reflectance (DR) UV-Vis-NIR spectroscopy and field emission scanning electron microscopy (FESEM) showed that the use of US improves the dispersion and decreases the size of both Au and Ag NPs. Moreover, with Au NPs, avoiding external reductants led to smaller NPs and more uniform in size. The prepared NPs were functionalized with oxytetracycline in water and tested against Escherichia coli (gram negative) and Staphylococcus epidermidis (gram positive) via the Kirby-Bauer test. The results show a better antibacterial activity of the functionalized nanoparticles compared to antibiotic-free NPs and pure oxytetracycline, advising the potential of the nanoparticles as drug carriers. These findings underscore the significance of US-assisted synthesis, paving the way to new environmentally friendly antimicrobial materials.

Essential oil mediated synthesis and application of highly stable copper nanoparticles as coatings on textiles and surfaces for rapid and sustained disinfection of microorganisms

Rampant pathogenesis induced by communicable microbes has necessitated development of technologies for rapid and sustained disinfection of surfaces. Copper nanoparticles (CuNPs) have been widely reported for their antimicrobial properties. However, nanostructured copper is prone to oxidative dissolution in the oil phase limiting its sustained use on surfaces and coatings. The current study reports a systematic investigation of a simple synthesis protocol using fatty acid stabilizers (particularly essential oils) for synthesis of copper nanoparticles in the oil phase. Of the various formulations synthesized, rosemary oil stabilized copper nanoparticles (RMO CuNPs) were noted to have the best inactivation kinetics and were also most stable. Upon morphological characterization by TEM and EELS, these were found to be monodispersed (φ5-8 nm) with copper coexisting in all three oxidation states on the surface of the nanoparticles. The nanoparticles were drop cast on woven fabric of around 500 threads per inch and exposed to gram positive bacteria (Staphylococcus aureus), gram negative bacteria (Escherichia coliandPseudomonas aeruginosa), enveloped RNA virus (phi6), non-enveloped RNA virus (MS2) and non-enveloped DNA virus (T4) to encompass the commonly encountered groups of pathogens. It was possible to completely disinfect 107copies of all microorganisms within 40 min of exposure. Further, this formulation was incorporated with polyurethane as thinners and used to coat non-woven fabrics. These also exhibited antimicrobial properties. Sustained disinfection with less than 9% cumulative copper loss for upto 14 washes with soap water was observed while the antioxidant activity was also preserved. Based on the studies conducted, RMO CuNP in oil phase was found to have excellent potential of integration on surface coatings, paints and polymers for rapid and sustained disinfection of microbes on surfaces.

Antifungal Activities of Biogenic Silver Nanoparticles Mediated by Marine Algae: In Vitro and In Vivo Insights of Coating Tomato Fruit to Protect against Penicillium italicum Blue Mold

In an attempt to reduce such decay induced by pathogenic causes, several studies investigated the effectiveness of nanoparticles (NPs) that play a vital role in saving food products, especially fruits. Current research delves into biogenic silver nanoparticles (using marine alga Turbinaria turbinata (Tt/Ag-NPs) and their characterization using FT-IR, TEM, EDS, and zeta potential. Some pathogenic fungi, which cause fruit spoilage, were isolated. We studied the impact of using Tt/Ag-NPs to protect against isolated fungi in vitro, and the influence of Tt/Ag-NPs as a coating of tomato fruit to protect against blue mold caused by Penicillium italicum (OR770486) over 17 days of storage time. Five treatments were examined: T1, healthy fruits were used as the positive control; T2, healthy fruits sprayed with Tt/Ag-NPs; T3, fruits infected with P. italicum followed by coating with Tt/Ag-NPs (pre-coating); T4, fruits coated with Tt/Ag-NPs followed by infection by P. italicum (post-coating); and T5, the negative control, fruits infected by P. italicum. The results displayed that Tt/Ag-NPs are crystalline, spherical in shape, with size ranges between 14.5 and 39.85 nm, and negative charges. Different concentrations of Tt/Ag-NPs possessed antifungal activities against Botrytis cinerea, Rhodotorula mucilaginosa, Penicillium expansum, Alternaria alternate, and Stemphylium vesicarium. After two days of tomatoes being infected with P. italicum, 55% of the fruits were spoilage. The tomato fruit coated with Tt/Ag-NPs delayed weight loss, increased titratable acidity (TA%), antioxidant%, and polyphenol contents, and decreased pH and total soluble solids (TSSs). There were no significant results between pre-coating and post-coating except in phenol contents increased in pre-coating. A particular focus is placed on the novel and promising approach of utilizing nanoparticles to combat foodborne pathogens and preserve commodities, with a spotlight on the application of nanoparticles in safeguarding tomatoes from decay.

Antimicrobial Properties of Newly Developed Silver-Enriched Red Onion-Polymer Composites

Simple low-cost, nontoxic, environmentally friendly plant-extract-based polymer films play an important role in their application in medicine, the food industry, and agriculture. The addition of silver nanoparticles to the composition of these films enhances their antimicrobial capabilities and makes them suitable for the treatment and prevention of infections. In this study, polymer-based gels and films (AgRonPVA) containing silver nanoparticles (AgNPs) were produced at room temperature from fresh red onion peel extract ("Ron"), silver nitrate, and polyvinyl alcohol (PVA). Silver nanoparticles were synthesized directly in a polymer matrix, which was irradiated by UV light. The presence of nanoparticles was approved by analyzing characteristic local surface plasmon resonance peaks occurring in UV-Vis absorbance spectra of irradiated experimental samples. The proof of evidence was supported by the results of XRD and EDX measurements. The diffusion-based method was applied to investigate the antimicrobial activity of several types of microbes located in the environment of the produced samples. Bacteria Staphylococcus aureus ATCC 29213, Acinetobacter baumannii ATCC BAA 747, and Pseudomonas aeruginosa ATCC 15442; yeasts Candida parapsilosis CBS 8836 and Candida albicans ATCC 90028; and microscopic fungi assays Aspergillus flavus BTL G-33 and Aspergillus fumigatus BTL G-38 were used in this investigation. The greatest effect was observed on Staphylococcus aureus, Acinetobacter baumannii, and Pseudomonas aeruginosa bacteria, defining these films as potential candidates for antimicrobial applications. The antimicrobial features of the films were less effective against fungi and the weakest against yeasts.

Lukianov D, Gayanova TE, Voronova EV, Shishilov ON, Stepakhin VD. The Synthesis and Analysis of the Cytotoxicity of Al2O3-Supported Silver Nanoparticles Prepared by the Plasma Chemical Process Initiated by Pulsed MW Radiation in the Al2O3-Ag Powder Mixtures

An original plasma chemical process initiated by microwave discharge in a mixture of metal and dielectric powders was applied to prepare specific materials, which consisted of microsized spherical particles of aluminum oxide covered with silver nanoparticles. The prepared materials are highly uniform in shape, size distribution, and composition. Their cytotoxicity was investigated using the human cell lines MCF7, HEK293T, A549, and VA-13 and the bacterial strains E. coli JW5503 (ΔtolC) and E. coli K12. Their cytotoxicity was found not to exceed the cytotoxicity of the starting materials. Thus, the prepared materials can be considered highly promising for catalysis and biotechnology applications.

Synthesis, Characterization, and Evaluation of the Antimicrobial Effects and Cytotoxicity of a Novel Nanocomposite Based on Polyamide 6 and Trimetaphosphate Nanoparticles Decorated with Silver Nanoparticles

This study aimed to develop a polymeric matrix of polyamide-6 (P6) impregnated with trimetaphosphate (TMP) nanoparticles and silver nanoparticles (AgNPs), and to evaluate its antimicrobial activity, surface free energy, TMP and Ag+ release, and cytotoxicity for use as a support in dental tissue. The data were subjected to statistical analysis (p < 0.05). P6 can be incorporated into TMP without altering its properties. In the first three hours, Ag+ was released for all groups decorated with AgNPs, and for TMP, the release only occurred for the P6-TMP-5% and P6-TMP-10% groups. In the inhibition zones, the AgNPs showed activity against both microorganisms. The P6-TMP-2.5%-Ag and P6-TMP-5%-Ag groups with AgNPs showed a greater reduction in CFU for S. mutans. For C. albicans, all groups showed a reduction in CFU. The P6-TMP groups showed higher cell viability, regardless of time (p < 0.05). The developed P6 polymeric matrix impregnated with TMP and AgNPs demonstrated promising antimicrobial properties against the tested microorganisms, making it a potential material for applications in scaffolds in dental tissues.

Comparing silver and gold nanoislands' surface plasmon resonance for bisacodyl and its metabolite quantification in human plasma

Gold and silver nanoparticles have witnessed increased scientific interest due to their colourful colloidal solutions and exceptional applications. Comparing the localized surface plasmon resonance (LSPR) of gold and silver nanoparticles is crucial for understanding and optimizing their optical properties. This comparison informs the design of highly sensitive plasmonic sensors, aids in selecting the most suitable nanoparticles for applications like surface-enhanced infrared spectroscopy (SEIRA) and biomedical imaging, and guides the choice between gold and silver nanoparticles based on their catalytic and photothermal properties. Ultimately, the study of LSPR facilitates the tailored use of these nanoparticles in diverse scientific and technological applications. Two SEIRA methods combined with partial least squares regression (PLSR) chemometric tools were developed. This development is based on the synthesis of homogeneous, high-dense deposited metal nanoparticle islands over the surface of glass substrates to be used as lab-on-chip SEIRA sensors for the determination of bisacodyl (BIS) and its active metabolite in plasma. SEM micrographs revealed the formation of metallic islands of colloidal citrate-capped gold and silver nanoparticles of average sizes of 29.7 and 15 nm, respectively. BIS and its active metabolite were placed on the nanoparticles' coated substrates to be directly measured, then PLSR chemometric modelling was used for the quantitative determinations. Plasmonic citrate-capped gold nanoparticle substrates showed better performance than those prepared using citrate-capped silver nanoparticles in terms of preparation time, enhancement factor, PLSR model prediction, and quantitative results. This study offers a way to determine BIS and its active metabolite in the concentration range 15-240 ng/mL in human plasma using inexpensive disposable glass-coated substrates that can be prepared in 1 h to get results in seconds with good recovery between 98.77 and 100.64%. The sensors provided fast, simple, selective, molecular-specific and inexpensive procedures to determine molecules in their pure form and biological fluid.

Utilization of ovalbumin and visible light irradiation for efficient and eco‐friendly production of AgNPs composite

Silver nanoparticles (AgNPs) are one of the most widely used antimicrobial agents. However, due to the potential problems of environmental pollution and high energy consumption, a green and efficient synthesis strategy of AgNPs is urgently required. Ovalbumin (OVA) is the most abundant protein in egg whites, and its extraction process is simple and productive. This paper reported a new green synthesis method of AgNPs by using OVA as an assistant accompanying with a visible light irradiation. Together with the reduction of silver ions, the uniformly dispersed OVA‐AgNPs nanocomposite could be formed within 30 min under xenon light irradiation by simple mixing AgNO3 and OVA in aqueous solution. The detailed mechanism study showed that tyrosine residue and peptide bonds in OVA played a major role in the reduction and stability of silver ions. In addition, in vitro antibacterial experiments indicated that 10 mg/L of OVA‐AgNPs, the minimum inhibitory concentration, has a good antimicrobial effect on both Gram‐positive and Gram‐negative bacteria, fungi, and some drug‐resistant bacteria species within 4 h of treatment, mainly due to the disruption of the structure of bacterial cell and the balance of reactive oxygen species. This work provides a new way for the green and efficient synthesis of AgNPs and shows good prospects for the applications in the field of biomedical materials and functional nanomaterials.

Insights into the physico-chemical and biological characterization of sodium lignosulfonate - silver nanosystems designed for wound management

Chronic wounds represent one of the complications that might occur from the disruption of wound healing process. Recently, there has been a rise in interest in employing nanotechnology to develop novel strategies for accelerating wound healing. The aim of the present study was to use a green synthesis method to obtain AgNPs/NaLS systems useful for wounds management and perform an in-depth investigation of their behavior during and post-synthesis as well as of their biological properties. The colloids obtained from silver nanoparticles (AgNPs) and commercial sodium lignosulfonate (NaLS) in a single-pot aqueous procedure have been fully characterized by UV-Vis, FT-IR, DLS, TEM, XRD, and XPS to evaluate the synthesis efficiency and to provide new insights in the process of AgNPs formation and NaLS behavior in aqueous solutions. The effects of various concentrations of NaLS (0-16 mg/mL) and AgNO3 (0-20 mM) and of two different temperatures on AgNPs formation have been analyzed. Although the room temperature is feasible for AgNPs synthesis, the short mixing at 70 °C significantly increases the speed of nanoparticle formation and storage stability. In all experimental conditions AgNPs of 20-40 nm in size have been obtained. The antimicrobial activity assessed quantitatively on clinical and reference bacterial strains, both in suspension and biofilm growth state, revealed a broad antimicrobial spectrum, the most intensive inhibitory effect being noticed against Pseudomonas aeruginosa and Escherichia coli strains. The AgNP/NaLS enhanced the NO extracellular release, potentially contributing to the microbicidal and anti-adherence activity by protein oxidation. Both AgNP/NaLS and NaLS were non-hemolytic (hemolytic index<5%, 2.26 ± 0.13% hemolysis) and biocompatible (102.17 ± 3.43 % HaCaT cells viability). The presence of AgNPs increased the antioxidative activity and induced a significant cytotoxicity on non-melanoma skin cancer cells (62.86 ± 8.27% Cal-27 cells viability). Taken together, all these features suggest the multivalent potential of these colloids for the development of novel strategies for wound management, acting by preventing infection-associated complications and supporting the tissue regeneration.

Metal Nanoparticles: Advanced and Promising Technology in Diabetic Wound Therapy

Diabetic wounds pose a significant challenge to public health, primarily due to insufficient blood vessel supply, bacterial infection, excessive oxidative stress, and impaired antioxidant defenses. The aforementioned condition not only places a significant physical burden on patients' prognosis, but also amplifies the economic strain on the medical system in treating diabetic wounds. Currently, the effectiveness of available treatments for diabetic wounds is limited. However, there is hope in the potential of metal nanoparticles (MNPs) to address these issues. MNPs exhibit excellent anti-inflammatory, antioxidant, antibacterial and pro-angiogenic properties, making them a promising solution for diabetic wounds. In addition, MNPs stimulate the expression of proteins that promote wound healing and serve as drug delivery systems for small-molecule drugs. By combining MNPs with other biomaterials such as hydrogels and chitosan, novel dressings can be developed and revolutionize the treatment of diabetic wounds. The present article provides a comprehensive overview of the research progress on the utilization of MNPs for treating diabetic wounds. Building upon this foundation, we summarize the underlying mechanisms involved in diabetic wound healing and discuss the potential application of MNPs as biomaterials for drug delivery. Furthermore, we provide an extensive analysis and discussion on the clinical implementation of dressings, while also highlighting future prospects for utilizing MNPs in diabetic wound management. In conclusion, MNPs represent a promising strategy for the treatment of diabetic wound healing. Future directions include combining other biological nanomaterials to synthesize new biological dressings or utilizing the other physicochemical properties of MNPs to promote wound healing. Synthetic biomaterials that contain MNPs not only play a role in all stages of diabetic wound healing, but also provide a stable physiological environment for the wound-healing process.

Nanoscale Vertical Resolution in Optical Printing of Inorganic Nanoparticles

Direct optical printing of functional inorganics shows tremendous potential as it enables the creation of intricate two-dimensional (2D) patterns and affordable design and production of various devices. Although there have been recent advancements in printing processes using short-wavelength light or pulsed lasers, the precise control of the vertical thickness in printed 3D structures has received little attention. This control is vital to the diverse functionalities of inorganic thin films and their devices, as they rely heavily on their thicknesses. This lack of research is attributed to the technical intricacy and complexity involved in the lithographic processes. Herein, we present a generalized optical 3D printing process for inorganic nanoparticles using maskless digital light processing. We develop a range of photocurable inorganic nanoparticle inks encompassing metals, semiconductors, and oxides, combined with photolinkable ligands and photoacid generators, enabling the direct solidification of nanoparticles in the ink medium. Our process creates complex and large-area patterns with a vertical resolution of ∼50 nm, producing 50-nm-thick 2D films and several micrometer-thick 3D architectures with no layer height difference via layer-by-layer deposition. Through fabrication and operation of multilayered switching devices with Au electrodes and Ag-organic resistive layers, the feasibility of our process for cost-effective manufacturing of multilayered devices is demonstrated.

Sunlight active cellulose/g-C3N4/TiO2nano-photocatalyst for simultaneous degradation of methylene blue dye and atenolol drug in real wastewater

The paper critically addresses two contemporary environmental challenges, the water crisis and the unrestricted discharge of organic pollutants in waterways together. An eco-friendly method was used to fabricate a cellulose/g-C3N4/TiO2photocatalytic composite that displayed a remarkable degradation of methylene blue dye and atenolol drug under natural sunlight. Introducing graphitic carbon nitride (g-C3N4) onto pristine TiO2improved hybrid material's photonic efficacy and enhanced interfacial charge separation. Furthermore, immobilizing TiO2/g-C3N4on a semi-interpenetrating cellulose matrix promoted photocatalyst recovery and its reuse, ensuring practical affordability. Under optimized conditions, the nano-photocatalyst exhibited ∼95% degradation of both contaminants within two hours while retaining ∼55% activity after ten cycles demonstrating a promising photostability. The nano-photocatalyst caused 66% and 57% reduction in COD and TOC values in industrial wastewater containing these pollutants. The photocatalysis was fitted to various models to elucidate the degradation kinetics, while LC-MS results suggested the mineralization pathway of dye majorly via ring opening demethylation. >98% disinfection was achieved againstE. coli(104-105CFU·ml-1) contaminated water. This study thus paves multifaceted strategies to treat wastewater contaminants at environmental levels employing nano-photocatalysis.

Metallic Nanoparticles: A Promising Arsenal against Antimicrobial Resistance-Unraveling Mechanisms and Enhancing Medication Efficacy

The misuse of antibiotics and antimycotics accelerates the emergence of antimicrobial resistance, prompting the need for novel strategies to combat this global issue. Metallic nanoparticles have emerged as effective tools for combating various resistant microbes. Numerous studies have highlighted their potential in addressing antibiotic-resistant fungi and bacterial strains. Understanding the mechanisms of action of these nanoparticles, including iron-oxide, gold, zinc oxide, and silver is a central focus of research within the life science community. Various hypotheses have been proposed regarding how nanoparticles exert their effects. Some suggest direct targeting of microbial cell membranes, while others emphasize the release of ions from nanoparticles. The most compelling proposed antimicrobial mechanism of nanoparticles involves oxidative damage caused by nanoparticles-generated reactive oxygen species. This review aims to consolidate knowledge, discuss the properties and mechanisms of action of metallic nanoparticles, and underscore their potential as alternatives to enhance the efficacy of existing medications against infections caused by antimicrobial-resistant pathogens.

The Enhanced Durability of AgCu Nanoparticle Coatings for Antibacterial Nonwoven Air Conditioner Filters

Antibacterial nonwoven fabrics, incorporated with Ag, have been applied as masks and air conditioner filters to prevent the spread of disease from airborne respiratory pathogens. In this work, we present a comparison study of Ag ions: Ag and AgCu nanoparticles (NPs) coated onto nonwoven fabrics intended for use as air conditioner antibacterial filters. We illustrate their color changes and durability running in air conditioners using antibacterial activity testing and X-ray Photoelectron Spectroscopic (XPS) analysis. We found that AgCu NPs showed the best antibacterial efficacy and durability. XPS analysis indicated that the Ag concentration, on both the AgCu and Ag- NP-coated fibers, changed little. On the contrary, the Ag concentration on Ag ion-coated fibers decreased by ~30%, and the coated NPs aggregated over time. The color change in AgCu NP-coated fabric, from yellow to white, is caused by oxide shell formation over the NPs, with nearly 46% oxidized silver. Our results, both from antibacterial evaluation and wind blowing tests, indicate that AgCu NP-coated fibers have higher durability, while Ag ion-coated fibers have little durability in such applications. The enhanced durability of the AgCu NP-coated antibacterial fabrics can be attributed to stronger NP-fiber interactions and greater ion release.

Collagen Biocomposites Derived from Fish Waste: Doped and Cross-Linked with Functionalized Fe3O4 Nanoparticles and Their Comparative Studies with a Green Approach

Collagen-based nanobiocomposites can reabsorb and are biodegradable. These properties are effectively controlled by the number of cross-links. This study demonstrates an effortless and proficient approach for the functionalization of Fe₃O₄ NPs for cross-linking collagen obtained from biowaste, viz., fish scales of Lates Calcarifer, a marine origin. The size of Fe₃O₄ NPs (10-40 nm) was confirmed using particle size analysis. The physico-chemical properties of the aminosilane-coated Fe₃O₄ NPs cross-linked via succinylated collagen (FFCSC) were characterized using different analytical techniques and compared with succinylated collagen doped with Fe₃O₄ NPs (FDSC). Thermogravimetric analysis indicates cross-linked product FFCSC to be more stable than the FDSC. Also, the antibacterial effect was more pronounced for FFCSC than for FDSC nanobiocomposites. FFCSC exhibited improved mechanical properties which are essential for materials used for wound dressing purposes. Moreover, the cell viability of fibroblasts (3T3-L1) and their morphology studied by SEM and fluorescence microscopy showed biocompatibility of both FDSC and FFCSC. Thus, the current investigation, involves a waste to wealth approach where the collagen-based nanobiocomposites present an easy way to recycle the biowaste to value-added products using simple and clean methods, which are suitable for use in biomedical and environmental applications.

Silver nanoparticles loaded on lactose/alginate: in situ synthesis, catalytic degradation, and pH-dependent antibacterial activity

We present the in situ synthesis of silver nanoparticles (AgNPs) through ionotropic gelation utilizing the biodegradable saccharides lactose (Lac) and alginate (Alg). The lactose reduced silver ions to form AgNPs. The crystallite structure of the nanocomposite AgNPs@Lac/Alg, with a mean size of 4-6 nm, was confirmed by analytical techniques. The nanocomposite exhibited high catalytic performance in degrading the pollutants methyl orange and rhodamine B. The antibacterial activity of the nanocomposite is pH-dependent, related to the alterations in surface properties of the nanocomposite at different pH values. At pH 6, the nanocomposite demonstrated the highest antibacterial activity. These findings suggest that this nanocomposite has the potential to be tailored for specific applications in environmental and medicinal treatments, making it a highly promising material.

Universal Single-Step Approach to the Immobilization of Cyclodextrins in a Supercritical Medium for Capturing Drug, Dye, and Metal Nanoclusters

By utilizing nanoreactor-like structures, the immobilization of macromolecules such as calixarenes and cyclodextrins (CD) with bucket-like structures provides new possibilities for engineered surface-molecule systems. The practical use of any molecular system depends on the availability of a universal procedure for immobilizing molecules with torus-like structures on various surfaces while maintaining identical operating parameters. There are currently several steps, including toxic solvent-based approaches using modified β-CD to covalently attach to surfaces with multistep reactions. However, the existing multistep process results in molecular orientation, restricts the accessibility of the hydrophobic barrel of β-CD's for practical use, and is effectively unable to use the surfaces immobilized with β-CD for a variety of applications. In this study, it was demonstrated that β-CD attached to the oxide-based semiconductor and metal surfaces through a condensation reaction between the hydroxyl-terminated oxide-based semiconductor/metal oxide and β-CD in supercritical carbon dioxide (SCCO₂) as a medium. The primary benefit of SCCO₂-assisted grafting of unmodified β-CD on various oxide-based metal and semiconductor surfaces is that it is a simple, efficient, one-step process and that it is ligand-free, scalable, substrate-independent, and uses minimal energy. Various physical microscopy and chemical spectroscopic methods were used to analyze the grafted β-CD oligomers. The application of the grafted β-CD films was demonstrated by the immobilization of rhodamine B (RhB), a dye, and dopamine, a drug. The in situ nucleation and growth of silver nanoclusters (AgNCs) in the molecular systems were studied for antibacterial and tribological properties by utilizing the guest-host interaction ability of β-CD.

Graphene oxide reinforced chitosan/polyvinyl alcohol antibacterial coatings on stainless steel surfaces exhibit superior bioactivity without human cell cytotoxicity

The study proposes an alternative therapeutics to diminish bacterial attachment in biomedical implants by modifying their surface with passive coatings. A uniform, thin-film of chitosan/polyvinyl alcohol/graphene oxide (CS/PVA/GO) was coated on 316 L stainless steel (SS) surface through spread casting followed by solvent evaporation. The abundant anchoring sites available at macromolecular interfaces of chitosan/PVA matrix facilitated a smooth, dense loading of GO. The effect of GO content on physicochemical features, antibacterial potential, and biocompatibility of coatings was thoroughly studied. The hybrid films displayed good adhesion behavior, and UV-protection ability with desired mechanical and thermal stability when coated on SS surface. Coatings manifested a 1.5-1.7 fold rise in antibacterial efficacy against Staphylococcus epidermidis and Staphylococcus aureus and exhibited a permanent biocidal response after 6 h of contact-active behaviour. We investigated a 3-fold generation of reactive oxygen species as the predominant antibacterial mechanism, which diminishes bacterial integrity by inducing protein leakage (8.5-9 fold higher) and suppressing respiratory chain activity as two secondary mechanisms. All coatings with varying GO content appeared non-haemolytic (<2%) with ultra-low cytotoxicity (<29.08%) against human hepatocellular carcinoma (HepG2) and peripheral blood mononuclear cells. The degradation rate of coatings in simulated body fluid exhibited a higher stability, indicated by a lower weight loss (69-78%) and a decrease in pH values as the GO content in coatings increased from 0.05 to 0.15 wt%. Such anti-infective coating is a step forward in inhibiting bacterial colonization on SS surfaces to extend its lifespan.

Multifunctional Layer-by-Layer Coating Based on a New Amphiphilic Block Copolymer via RAFT-Mediated Polymerization-Induced Self-Assembly Process

In this hi-tech world, the "smart coatings" have sparked significant attention among materials scientists because of their versatile applications. Various strategies have been developed to generate smart coatings in the past 2 decades. The layer-by-layer (LbL) technique is the most commonly employed strategy to produce a smart coating for suitable applications. Here, we present a smart coating with healing, antifogging, and fluorescence properties fabricated by the LbL assembly of an anionic amphiphilic block copolymer latex and cationic inorganic POSS (polyhedral-oligomeric-silsesquioxane) nanoparticles. In this case, a new anionic block copolymer (BCP), {poly(sodium styrene sulfonate)-block-poly[2-(acetoacetoxy)ethyl methacrylate]}, (PSS-b-PAAEMA) was synthesized via surfactant-free RAFT-mediated emulsion polymerization using the PISA technique. The PSS-b-PAAEMA was characterized by ¹H NMR, dynamic light scattering, scanning electron microscopy, and transmission electron microscopy analyses as well as by UV-vis and photoluminescence spectroscopy. For LbL coating fabrication, an amine-modified glass was successively dipped in the anionic latex and cationic POSS solution. The transparent coating exhibited good fluorescence properties under UV light (blue color). The antifogging performance of the coating was also investigated using both cold-warm and hot-vapor techniques. Additionally, the coating surface showed a significant healing activity with a healing efficiency of >75% through ionic interaction. Thus, this finding provides a simple low volatile organic compound (VOC) water-based LbL coating with multifunctional properties that can be a potential material for versatile applications.

Review of Antimicrobial Nanocoatings in Medicine and Dentistry: Mechanisms of Action, Biocompatibility Performance, Safety, and Benefits Compared to Antibiotics

This review discusses topics relevant to the development of antimicrobial nanocoatings and nanoscale surface modifications for medical and dental applications. Nanomaterials have unique properties compared to their micro- and macro-scale counterparts and can be used to reduce or inhibit bacterial growth, surface colonization and biofilm development. Generally, nanocoatings exert their antimicrobial effects through biochemical reactions, production of reactive oxygen species or ionic release, while modified nanotopographies create a physically hostile surface for bacteria, killing cells via biomechanical damage. Nanocoatings may consist of metal nanoparticles including silver, copper, gold, zinc, titanium, and aluminum, while nonmetallic compounds used in nanocoatings may be carbon-based in the form of graphene or carbon nanotubes, or composed of silica or chitosan. Surface nanotopography can be modified by the inclusion of nanoprotrusions or black silicon. Two or more nanomaterials can be combined to form nanocomposites with distinct chemical or physical characteristics, allowing combination of different properties such as antimicrobial activity, biocompatibility, strength, and durability. Despite their wide range of applications in medical engineering, questions have been raised regarding potential toxicity and hazards. Current legal frameworks do not effectively regulate antimicrobial nanocoatings in matters of safety, with open questions remaining about risk analysis and occupational exposure limits not considering coating-based approaches. Bacterial resistance to nanomaterials is also a concern, especially where it may affect wider antimicrobial resistance. Nanocoatings have excellent potential for future use, but safe development of antimicrobials requires careful consideration of the "One Health" agenda, appropriate legislation, and risk assessment.

Strategies for Surface Design in Surface Plasmon Resonance (SPR) Sensing

Surface plasmon resonance (SPR) comprises several surface-sensitive techniques that enable the trace and ultra-trace detection of various analytes through affinity pairing. Although enabling label-free, sensitive detection and real-time monitoring, several issues remain to be addressed, such as poor stability, non-specific adsorption and the loss of operational activity of biomolecules. In this review, the progress over sensor modification, immobilization techniques and novel 2D nanomaterials, gold nanostructures and magnetic nanoparticles for signal amplification is discussed. The advantages and disadvantages of each design strategy will be provided together with some of the recent achievements.

Customized biofilm device for antibiofilm and antibacterial screening of newly developed nanostructured silver and zinc coatings

BACKGROUND

Bacterial colonisation on implantable device surfaces is estimated to cause more than half of healthcare-associated infections. The application of inorganic coatings onto implantable devices limits/prevents microbial contaminations. However, reliable and high-throughput deposition technologies and experimental trials of metal coatings for biomedical applications are missing. Here, we propose the combination of the Ionized Jet Deposition (IJD) technology for metal-coating application, with the Calgary Biofilm Device (CBD) for high-throughput antibacterial and antibiofilm screening, to develop and screen novel metal-based coatings.

RESULTS

The films are composed of nanosized spherical aggregates of metallic silver or zinc oxide with a homogeneous and highly rough surface topography. The antibacterial and antibiofilm activity of the coatings is related with the Gram staining, being Ag and Zn coatings more effective against gram-negative and gram-positive bacteria, respectively. The antibacterial/antibiofilm effect is proportional to the amount of metal deposited that influences the amount of metal ions released. The roughness also impacts the activity, mostly for Zn coatings. Antibiofilm properties are stronger on biofilms developing on the coating than on biofilms formed on uncoated substrates. This suggests a higher antibiofilm effect arising from the direct contact bacteria-coating than that associated with the metal ions release. Proof-of-concept of application to titanium alloys, representative of orthopaedic prostheses, confirmed the antibiofilm results, validating the approach. In addition, MTT tests show that the coatings are non-cytotoxic and ICP demonstrates that they have suitable release duration (> 7 days), suggesting the applicability of these new generation metal-based coatings for the functionalization of biomedical devices.

CONCLUSIONS

The combination of the Calgary Biofilm Device with the Ionized Jet Deposition technology proved to be an innovative and powerful tool that allows to monitor both the metal ions release and the surface topography of the films, which makes it suitable for the study of the antibacterial and antibiofilm activity of nanostructured materials. The results obtained with the CBD were validated with coatings on titanium alloys and extended by also considering the anti-adhesion properties and biocompatibility. In view of upcoming application in orthopaedics, these evaluations would be useful for the development of materials with pleiotropic antimicrobial mechanisms.

Boosting the Antibacterial Performance of Natural Rubber Latex Foam by Introducing Silver-Doped Zinc Oxide

Natural rubber (NR) latex foam is one of the rubber products that are increasingly in demand in the market. This is simply because of its lightweight, good thermal insulation, and resilience. The applications of NR latex foam are mostly for pillows and mattresses. This has resulted in these products requiring antibacterial performance which is very important for the safety of the end-users. In this study, the antibacterial NR latex foam was prepared by incorporating the silver-doped zinc oxide (Ag-doped ZnO) into the NR latex foam. Ag-doped ZnO was prepared by microwave-assisted method and then characterized through morphological characteristics and X-ray diffraction (XRD). The content of Ag doped onto ZnO was designed by varying the AgNO₃ content at 15 wt%, 50 wt%, and 100 wt% of ZnO. The results confirmed that the Ag was successfully doped onto ZnO. The silver particles were found to be in the 40-50 nm range, where the size of ZnO ranges between 300 and 400 nm, and the Ag attached to the ZnO particles. The XRD patterns of Ag-doped ZnO correspond to planes of hexagonal wurtzite ZnO structure and cubic metallic Ag. This Ag-doped ZnO was further added to NR latex foam. It was observed that Ag-doped ZnO did not affect the physical properties of the NR latex foam. However, it is clear that both the inhibition zone and percent reduction of bacteria (e.g., E. coli and S. aureus) were enhanced by the addition of Ag-doped ZnO. It showed a decrease in the amount of cell growth over contact time. The content of 100 wt% AgNO₃ could reduce E. coli and S. aureus up to 64.72% and 58.90%, respectively, when samples were maintained for 24 h. This study provides a scientific understanding of how Ag-doped ZnO could facilitate the development of eventual rubber foam products based on the respective results.

Diagnosis and treatment of chronic osteomyelitis based on nanomaterials

Chronic osteomyelitis is a painful and serious disease caused by infected surgical prostheses or infected fractures. Traditional treatment includes surgical debridement followed by prolonged systemic antibiotics. However, excessive antibiotic use has been inducing rapid emergence of antibiotic-resistant bacteria worldwide. Additionally, it is difficult for antibiotics to penetrate internal sites of infection such as bone, thus limiting their efficacy. New approaches to treat chronic osteomyelitis remain a major challenge for orthopedic surgeons. Luckily, the development of nanotechnology has brought new antimicrobial options with high specificity to infection sites, offering a possible way to address these challenges. Substantial progress has been made in constructing antibacterial nanomaterials for treatment of chronic osteomyelitis. Here, we review some current strategies for treatment of chronic osteomyelitis and their underlying mechanisms.

Biosynthesis of Metal and Metal Oxide Nanoparticles Using Microbial Cultures: Mechanisms, Antimicrobial Activity and Applications to Cultural Heritage

Nanoparticles (1 to 100 nm) have unique physical and chemical properties, which makes them suitable for application in a vast range of scientific and technological fields. In particular, metal nanoparticle (MNPs) research has been showing promising antimicrobial activities, paving the way for new applications. However, despite some research into their antimicrobial potential, the antimicrobial mechanisms are still not well determined. Nanoparticles' biosynthesis, using plant extracts or microorganisms, has shown promising results as green alternatives to chemical synthesis; however, the knowledge regarding the mechanisms behind it is neither abundant nor consensual. In this review, findings from studies on the antimicrobial and biosynthesis mechanisms of MNPs were compiled and evidence-based mechanisms proposed. The first revealed the importance of enzymatic disturbance by internalized metal ions, while the second illustrated the role of reducing and negatively charged molecules. Additionally, the main results from recent studies (2018-2022) on the biosynthesis of MNPs using microorganisms were summarized and analyzed, evidencing a prevalence of research on silver nanoparticles synthesized using bacteria aiming toward testing their antimicrobial potential. Finally, a synopsis of studies on MNPs applied to cultural heritage materials showed potential for their future use in preservation.

Electrospun Polyacrylonitrile Silver(I,III) Oxide Nanoparticle Nanocomposites as Alternative Antimicrobial Materials

Infectious microbial diseases can easily be transferred from person to person in the air or via high contact surfaces. As a result, researchers must aspire to create materials that can be implemented in surface contact applications to disrupt pathogen growth and transmission. This study examines the antimicrobial properties of polyacrylonitrile (PAN) nanofibers coated with silver nanoparticles (AgNPs) and silver(I,III) oxide. PAN was homogenized with varied weight concentrations of silver nitrate (AgNO3) in N,N-dimethylformamide solution, a common organic solvent that serves as both an electrospinning solvent and as a reducing agent that forms AgNPs. The subsequent colloids were electrospun into nanofibers, which were then characterized via various analysis techniques, including scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis, dynamic light scattering, and X-ray photoelectron spectroscopy. A total of 10 microbes, including 7 strains of Gram-positive bacteria, 2 strains of Gram-negative bacteria, and Candida albicans, were incubated with cutouts of various PAN-AgNP nanocomposites using disk diffusion methods to test for the nanocomposites' antimicrobial efficiency. We report that our electrospun PAN-AgNP nanocomposites contain 100% AgO, a rare, mixed oxidation state of silver(I,III) oxide that is a better sterilizing agent than conventional nanosilver. PAN-AgNP nanocomposites also retain a certain degree of antimicrobial longevity; samples stored for approximately 90 days demonstrate a similar antimicrobial activity against Escherichia coli (E. coli) and Lactobacillus crispatus (L. crispatus) when compared to their newly electrospun counterparts. Moreover, our results indicate that PAN-AgNP nanocomposites successfully display antimicrobial activity against various bacteria and fungi strains regardless of their resistance to conventional antibiotics. Our study demonstrates that PAN-AgNP nanocomposites, a novel polymer material with long-term universal antimicrobial stability, can potentially be applied as a universal antimicrobial on surfaces at risk of contracting microbial infections and alleviate issues related to antibiotic overuse and microbial mutability.

Electric Spark Deposition of Antibacterial Silver Coating on Microstructured Titanium Surfaces with a Novel Flexible Brush Electrode

Infection caused by orthopedic titanium implants, which results in tissue damage, is a key factor in endosseous implant failure. Given the seriousness of implant infections and the limitations of antibiotic therapy, surface microstructures and antimicrobial silver coatings have emerged as prominent research areas and have displayed certain antimicrobial effects. Researchers are now working to combine the two to produce more effective antimicrobial surfaces. However, building robust and homogeneous coatings on complex microstructured surfaces is a tough task due to the limits of surface modification techniques. In this study, a novel flexible electrode brush (silver brush) instead of a traditional hard electrode was designed with electrical discharge machining, which has the ability to adapt to complex groove interiors. The results showed that the use of flexible electrode brush allowed silver to be deposited uniformly in titanium alloy microgrooves. On the surface of Ag-TC4, a uniformly covered deposit was visible, and it slowly released silver ions into a liquid environment. In vitro bacterial assays showed that a Ag-TC4 microstructured surface reduced bacterial adhesion and bacterial biofilm formation, and the antibacterial activity of Ag-TC4 against Staphylococcus aureus and Escherichia coli was 99.68% ± 0.002 and 99.50% ± 0.007, respectively. This research could lay the groundwork for the study of antimicrobial metal bound to microstructured surfaces and pave the way for future implant surface design.

Nanomaterial-Based Antimicrobial Coating for Biomedical Implants: New Age Solution for Biofilm-Associated Infections

Recently, the upsurge in hospital-acquired diseases has put global health at risk. Biomedical implants being the primary source of contamination, the development of biomedical implants with antimicrobial coatings has attracted the attention of a large group of researchers from around the globe. Bacteria develops biofilms on the surface of implants, making it challenging to eradicate them with the standard approach of administering antibiotics. A further issue of current concern is the fast resurgence of resistance to conventional antibiotics. As nanotechnology continues to advance, various types of nanomaterials have been created, including 2D nanoparticles and metal and metal oxide nanoparticles with antimicrobial properties. Researchers from all over the world are using these materials as a coating agent for biomedical implants to create an antimicrobial environment. This comprehensive and contemporary review summarizes various metals, metal oxide nanoparticles, 2D nanomaterials, and their composites that have been used or may be used in the future as an antimicrobial coating agent for biomedical implants, as well as their succinct mode of action to combat biofilm-associated infection and diseases.

Growth suppression of bacteria by biofilm deterioration using silver nanoparticles with magnetic doping

Decades of antibiotic use and misuse have generated selective pressure toward the rise of antibiotic-resistant bacteria, which now contaminate our environment and pose a major threat to humanity. According to the evolutionary "Red queen theory", developing new antimicrobial technologies is both urgent and mandatory. While new antibiotics and antibacterial technologies have been developed, most fail to penetrate the biofilm that protects bacteria against external antimicrobial attacks. Hence, new antimicrobial formulations should combine toxicity for bacteria, biofilm permeation ability, biofilm deterioration capability, and tolerability by the organism without renouncing compatibility with a sustainable, low-cost, and scalable production route as well as an acceptable ecological impact after the ineluctable release of the antibacterial compound in the environment. Here, we report on the use of silver nanoparticles (NPs) doped with magnetic elements (Co and Fe) that allow standard silver antibacterial agents to perforate bacterial biofilms through magnetophoretic migration upon the application of an external magnetic field. The method has been proved to be effective in opening micrometric channels and reducing the thicknesses of models of biofilms containing bacteria such as Enterococcus faecalis, Enterobacter cloacae, and Bacillus subtilis. Besides, the NPs increase the membrane lipid peroxidation biomarkers through the formation of reactive oxygen species in E. faecalis, E. cloacae, B. subtilis, and Pseudomonas putida colonies. The NPs are produced using a one-step, scalable, and environmentally low-cost procedure based on laser ablation in a liquid, allowing easy transfer to real-world applications. The antibacterial effectiveness of these magnetic silver NPs may be further optimized by engineering the external magnetic fields and surface conjugation with specific functionalities for biofilm disruption or bactericidal effectiveness.

A Novel Ag@AgCl Nanoparticle Synthesized by Arctic Marine Bacterium: Characterization, Activity and Mechanism

An additive- and pollution-free method for the preparation of biogenic silver and silver chloride nanoparticles (Ag@AgCl NPs) was developed from the bacteria Shewanella sp. Arc9-LZ, which was isolated from the deep sea of the Arctic Ocean. The optimal synthesizing conditions were explored, including light, pH, Ag⁺ concentration and time. The nanoparticles were studied by means of ultraviolet-visible (UV-Vis) spectrophotometry, energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and inductively coupled plasma optical emission spectrometers (ICP-OES). The transmission electron microscope (TEM) showed that the nanoparticles were spherical and well dispersed, with particle sizes less than 20.00 nm. With Ag@AgCl nanoparticles, the kinetic rate constants for congo red (CR) and rhodamine B (RhB) dye degradation were 2.74 × 10^-1 min^-1 and 7.78 × 10^-1 min^-1, respectively. The maximum decolourization efficiencies of CR and RhB were 93.36% and 99.52%, respectively. Ag@AgCl nanoparticles also showed high antibacterial activities against the Gram-positive and Gram-negative bacteria. The Fourier transform infrared spectroscopy (FTIR) spectrum indicated that the O-H, N-H and -COO- groups in the supernatant of Arc9-LZ might participate in the reduction, stabilization and capping of nanoparticles. We mapped the schematic diagram on possible mechanisms for synthesizing Ag@AgCl NPs.

Surfaces with instant and persistent antimicrobial efficacy against bacteria and SARS-CoV-2

Surfaces contaminated with bacteria and viruses contribute to the transmission of infectious diseases and pose a significant threat to global public health. Modern day disinfection either relies on fast-acting (>3-log reduction within a few minutes), yet impermanent, liquid-, vapor-, or radiation-based disinfection techniques, or long-lasting, but slower-acting, passive antimicrobial surfaces based on heavy metal surfaces, or metallic nanoparticles. There is currently no surface that provides instant and persistent antimicrobial efficacy against a broad spectrum of bacteria and viruses. In this work, we describe a class of extremely durable antimicrobial surfaces incorporating different plant secondary metabolites that are capable of rapid disinfection (>4-log reduction) of current and emerging pathogens within minutes, while maintaining persistent efficacy over several months and under significant environmental duress. We also show that these surfaces can be readily applied onto a variety of desired substrates or devices via simple application techniques such as spray, flow, or brush coating.

AgCu NP Formation by the Ag NP Catalysis of Cu Ions at Room Temperature and Their Antibacterial Efficacy: A Kinetic Study

Although a facile route to prepare AgCu nanoalloys (NAs) with enhanced antibacterial efficacy using Ag NP catalysis of Cu ions at elevated temperatures was previously developed, its detailed reaction process is still unclear due to the fast reaction process at higher temperatures. This work found that AgCu NAs can also be synthesized by the same process but at room temperature. AgCu NAs formation kinetics have been studied using UV-Visible spectra and Transmission Electron Microscopy (TEM), where formation includes Cu²⁺ deposition onto the Ag NP surface and Ag⁺ release, reduction, and agglomeration to form new Ag NPs; this is followed by a redistribution of the NA components and coalescence to form larger AgCu NPs. It is found that SPR absorption is linear with time early in the reaction, as expected for both pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetics; neither model is followed subsequently due to contributions from newly formed Ag NPs and AgCu NAs. The antibacterial efficacy of the AgCu NAs thus formed was estimated, with a continuous increase over the whole alloying process, demonstrating the correlation of antibacterial efficacy with the extent of AgCu NA formation and Ag⁺ release.

Green Synthesis and Antimicrobial Activities of Silver Nanoparticles Using Calotropis gigantea from Ie Seu-Um Geothermal Area, Aceh Province, Indonesia

Herein, we report our success synthesizing silver nanoparticles (AgNPs) using aqueous extracts from the leaves and flowers of Calotropis gigantea growing in the geothermal manifestation Ie Seu-Um, Aceh Besar, Indonesia. C. gigantea aqueous extract can be used as a bio-reductant for Ag+→Ag0 conversion, obtained by 48h incubation of Ag+, and the extract mixture in a dark condition. UV-Vis characterization showed that the surface plasmon resonance (SPR) peaks of AgNPs-leaf C. gigantea (AgNPs-LCg) and AgNPs-flower C. gigantea (AgNPs-FCg) appeared in the wavelength range of 410-460 nm. Scanning electron microscopy energy-dispersive X-ray spectrometry (SEM-EDS) revealed the agglomeration and spherical shapes of AgNPs-LCg and AgNPs-FCg with diameters ranging from 87.85 to 256.7 nm. Zeta potentials were observed in the range of -41.8 to -25.1 mV. The Kirby-Bauer disc diffusion assay revealed AgNPs-FCg as the most potent antimicrobial agent with inhibition zones of 12.05 ± 0.58, 11.29 ± 0.45, and 9.02 ± 0.10 mm for Escherichia coli, Staphylococcus aureus, and Candida albicans, respectively. In conclusion, aqueous extract from the leaves or flowers of Calotropis gigantea may be used in the green synthesis of AgNPs with broad-spectrum antimicrobial activities.