A novel green synthesized ZnO-based antimicrobial nanocomposite: synergistic action, in vitro cytotoxicity, and molecular docking studies of ceftazidime, metformin, and chitosan against multidrug-resistant Salmonella enterica.

Multidrug-resistant Pseudomonas aeruginosa poses a significant global health threat, highlighting the need for innovative antimicrobial strategies. This study presents the successful synthesis, optimization, and characterization of a novel zinc oxide/chitosan/amoxicillin (ZnO/CS/AMX) nanocomposite aimed at combating P. aeruginosa infections, including the ability to form biofilms. Response surface methodology (RSM) based on the Box-Behnken design (BBD) was used to optimize the production of ZnO NPs using cell-free metabolites of P. aeruginosa. The optimal parameters for biosynthesis of ZnO NPs require a mixing ratio of 1:4 v/v% between the cell-free bacterial metabolites and 30 mM Zn precursor (Zn(NO3)2.6H2O) at pH 7.0 and 30 °C. The nanocomposite was synthesized by encapsulating amoxicillin (AMX) within chitosan-coated zinc oxide nanoparticles (ZnO NPs). Its properties were confirmed through various characterization techniques including UV-Vis spectroscopy (340 to 380 nm), XRD (101 plane, an average crystallite size = 59 nm), FTIR (Zn-O and proteins stretching vibrations), TEM (spherical to quasi-spherical in shape with size range = 36-98 nm), and zeta potential analyses (+ 35 ± 2.3 mV). The maximum drug loading of AMX in the ZnO/CS/AMX nanocomposite was found to be 55.7%. The antimicrobial effectiveness was thoroughly assessed against various clinical isolates of P. aeruginosa, all of which showed natural resistance to chitosan (CS) and AMX individually, as well as the reference strain ATCC 27853. Quantitative assays further confirmed the superior bactericidal potential of the nanocomposite compared to ZnO NPs and imipenem. The nanocomposite achieved exceptionally low minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) levels, as low as 10 µg/ml against resistant clinical isolates. TEM micrographs of P. aeruginosa cells treated with the nanocomposite revealed severe cellular damage. This damage included extensive separation between the cell wall and cytoplasmic membrane, complete cell lysis, and severe malformations. In addition, the nanocomposite exhibited outstanding antibiofilm activity at concentrations as low as 50 µg/ml. This activity dramatically increased in a dose-dependent manner, achieving ≤ 100% biofilm inhibition at 150 µg/ml. The cytotoxicity assessment on Vero cells demonstrated a promising safety profile, with a CC50 of 292 ± 1.3 µg/ml for the nanocomposite, nearly three times higher than that of ZnO NPs (106 ± 0.9 µg/ml). This wide therapeutic window indicates that ZnO/CS/AMX can effectively combat P. aeruginosa at concentrations far below that toxic to mammalian cells. These findings demonstrate that the ZnO/CS/AMX nanocomposite acts through a synergistic, multimodal mechanism, effectively overcoming bacterial resistance and biofilm recalcitrance, while also exhibiting favorable biocompatibility. KEY POINTS: RSM-Box-Behnken optimized green biosynthesis of ZnO NPs using cell-free metabolites of P. aeruginosa Green synthesis of zinc oxide/chitosan/amoxicillin nanocomposite to combat MDR P. aeruginosa The nanocomposite markedly enhances bactericidal and antibiofilm efficacy at low doses with high mammalian cell safety and synergistic action.

The rapid emergence of multidrug‐resistant (MDR) pathogens, particularly in hospital wastewater, poses a serious threat to public health and emphasizes the need for alternative antimicrobial strategies. In this study, Enterococcus hirae, an environmentally derived strain, was used for the first time in the extracellular green synthesis of zinc oxide nanoparticles (ZnO NPs) and copper oxide/zinc oxide nanoparticles (CuO/ZnO NPs). The nanoparticles were characterized using standard techniques. Ultraviolet–visible (UV‐Vis) spectra, X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), and energy‐dispersive X‐ray spectroscopy (EDS) confirmed both nanoparticle formation, size, and morphology. Antimicrobial activity against Staphylococcus aureus (ATCC 6538), Morganella morganii, Kerstersia gyiorum, and Klebsiella pneumoniae was evaluated using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays, showing a 62.5% greater efficacy of bimetallic NPs than ZnO alone. The 2,2‐diphenyl‐1‐picrylhydrazyl hydrate (DPPH) assay revealed that E‐CuO/ZnO NPs exhibited superior antioxidant activity with the lowest IC50 of 5.528 μg/mL, outperforming E‐ZnO NPs, which is attributed to the synergistic effect between ZnO and CuO NPs. The combination of E‐ZnO and E‐CuO/ZnO nanoparticles with ciprofloxacin (CIP) and ceftazidime (CAZ) was evaluated against MDR isolates. Synergistic interactions were observed particularly against K. pneumoniae. This study confirms effective E. hirae‐mediated synthesis and the enhanced antibacterial and antioxidant potential of CuO/ZnO NPs, supporting eco‐friendly strategies against MDR infections, with synergistic interactions observed with conventional antibiotics, particularly against K. pneumoniae, indicating that the nanoparticles can enhance antibiotic efficacy.

Simple SummaryThe overuse of antibiotics in the poultry industry has led to the emergence of multidrug-resistant microorganisms. Thus, there is a need to find an alternative to conventional antibiotics. Recently, zinc oxide nanoparticles (ZnO NPs) have gained much attention due to their excellent antibacterial activity. In addition, ZnO NPs is an essential trace mineral in poultry diets. In this sense, incorporating ZnO NPs into poultry can promote growth and performance while serving as an alternative antibacterial agent to control diseases. Therefore, this study aimed to assess the in vitro antibacterial activity and antibacterial mechanisms of ZnO NPs against poultry-associated foodborne pathogens (Salmonella spp., Escherichia coli, and Staphylococcus aureus). The obtained findings demonstrated effective antibacterial actions against the tested microorganisms. The nanotechnology approach could represent a new tool for combating pathogens in the poultry industry.Since the emergence of multidrug-resistant bacteria in the poultry industry is currently a serious threat, there is an urgent need to develop a more efficient and alternative antibacterial substance. Zinc oxide nanoparticles (ZnO NPs) have exhibited antibacterial efficacy against a wide range of microorganisms. Although the in vitro antibacterial activity of ZnO NPs has been studied, little is known about the antibacterial mechanisms of ZnO NPs against poultry-associated foodborne pathogens. In the present study, ZnO NPs were successfully synthesized using Lactobacillus plantarum TA4, characterized, and their antibacterial potential against common avian pathogens (Salmonella spp., Escherichia coli, and Staphylococcus aureus) was investigated. Confirmation of ZnO NPs by UV-Visual spectroscopy showed an absorption band center at 360 nm. Morphologically, the synthesized ZnO NPs were oval with an average particle size of 29.7 nm. Based on the dissolution study of Zn2+, ZnO NPs released more ions than their bulk counterparts. Results from the agar well diffusion assay indicated that ZnO NPs effectively inhibited the growth of the three poultry-associated foodborne pathogens. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were assessed using various concentrations of ZnO NPs, which resulted in excellent antibacterial activity as compared to their bulkier counterparts. S. aureus was more susceptible to ZnO NPs compared to the other tested bacteria. Furthermore, the ZnO NPs demonstrated substantial biofilm inhibition and eradication. The formation of reactive oxygen species (ROS) and cellular material leakage was quantified to determine the underlying antibacterial mechanisms, whereas a scanning electron microscope (SEM) was used to examine the morphological changes of tested bacteria treated with ZnO NPs. The findings suggested that ROS-induced oxidative stress caused membrane damage and bacterial cell death. Overall, the results demonstrated that ZnO NPs could be developed as an alternative antibiotic in poultry production and revealed new possibilities in combating pathogenic microorganisms.

Biopolymer (chitosan) was isolated from crab shell waste through the processes of demineralization, deproteinization, decolourization and deacetylation. The resulting chitosan (CHS) was further treated with silver nitrate (AgNO3) solution at various concentrations (0.5, 1.0 and 1.5 M) in order to enhance the antimicrobial activity of chitosan. The crab shell powder (CSP) and (CHS) were characterized using X-ray Diffractometer (XRD), Fourier Transform Infrared (FT-IR), and Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS). The antimicrobial mode of action of AgNO3 treated chitosan was performed using serial dilution (1:2) technique for minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) and tested against four microorganisms (Escherichia coli, Klebsiella pneumonia, Staphlococcusaureus and Pseudopodium). The result of proximate analysis of CHS and chitin (CHN) showed % crude protein to be 12.24±001 and 20.54±0.03 respectively, % ash was found to be 4.1±0.01 for CHS and 3.80±0.01 for CHN. The FTIR spectra of CHS and CHN showed their characteristic absorption peaks and the diffractograms of CSP and CHS showed CaCO3 to be the major mineral present in the samples. The antimicrobial evaluation revealed that untreated chitosan extract (UCHSE) showed no antimicrobial activity against the four tested microorganisms. The results of MIC and MBC showed that the organisms responded to the antimicrobial agent at different dilution concentration. It was observed that CHS treated with 0.5 M AgNO3 (0.5 SNCHSE) inhibited the growth of E. coli at 1000 µg/mL, S. aureus at 500 µg/mL while it exhibited bactericidal (MBC) activity against all the organisms at 1000 µg/mL.

Zinc oxide nanoparticles (ZnO NPs) have anticancer, antidiabetic, antibacterial, and anti-inflammatory properties in the biotechnology field. Cafestol, which is the one of the diterpene in coffee, has antimicrobial and anticancer activities. This study aimed to synthesize the cafestol–chitosan–ZnO NP system to evaluate its antibacterial activity. ZnO NPs were produced by the chemical precipitation method. Optimization studies were performed to obtain the desired size of the ZnO NPs. The type of zinc salt [ZnCl2, Zn(SO4)], salt concentration (0.1; 0.2; 0.5 M), base type (NH3, NaOH), reaction time (6, 12, 18, 24 h), mixing speed (300, 400, 500 rpm), and calcination time (1, 2, 3 h) parameters in the method were investigated to yield the targeted size. The optimum experimental conditions required to synthesize in the 45–60 nm size range were determined as a 0.2 M Zn(SO4) salt type and concentration, NaOH base type, 18 h reaction time, at 400 rpm mixing speed and 2 h calcination time. After synthesizing the ZnO NPs coated with chitosan (CS), the cafestol was ligated to the CS–ZnO NP. It was proved by Fourier-transform infrared, differential scanning calorimeter/thermogravimetry analysis/diamond thermogravimetry analysis and scanning electron microscope analyses that cafestol–CS–ZnO NPs were successfully synthesized. The antibacterial effects of cafestol, CS, ZnO NPs, CS–ZnO NPs and cafestol–CS–ZnO NPs were evaluated on human pathogenic Gram-positive strains Staphylococcus aureus ATCC 25923 and Bacillus cereus ATCC 11778 and Gram-negative strains Pseudomonas aeruginosa PA01and Escherichia coli ATCC 25922. The ZnO NPs, CS–ZnO NP, and cafestol–CS–ZnO NP (varying between 20 and 1000 μg/mL) completely inhibited bacterial growth for S. aureus, B. cereus, and E. coli. The incorporation of CS and CS–cafestol improved the antibacterial activity of the ZnO NPs samples against P. aeruginosa PA01 with a 75–87.5% inhibition. The obtained data shows that CS–ZnO and cafestol–CS–ZnO NPs have great potential for biological and pharmaceutical applications.

The unregulated administration of currently available antimicrobial agents resulted in overspreading of resistant microbial phenotypes. In this study, Mucor racemosus was used for biosynthesis of zinc oxide nanoparticles (ZnO NPs) through fungi-based ecofriendly approach. The biosynthesized of ZnO NPs was initially considered based on analytical practices including UV–vis spectroscopy and transmission electron microscopy (TEM). Additionally, their cytotoxicity and anticancer activity were analyzed using suitable cell lines and their antioxidant effect was also assessed. Microbiologically, their inhibitory activity was comparatively evaluated against various methicillinresistant Staphylococcus aureus (MRSA) and methicillinsensitive Staphylococcus aureus (MSSA). Characterization of ZnO NPs displayed a distinct maximum absorption peak at 320 nm appeared in the UV–vis. Also, TEM revealed predominantly spherical ZnO NPs with particle size distribution ranging from 15 to 55 nm (mean size ≃ 40 nm). The normal cell line (Wi-38) illustrated the biosafety of ZnO NPs, where results showed IC50 of 197.2 µg/mL. Furthermore, ZnO NPs exhibited promising suppressive activity on Hep-G2 cancerous cell with IC50 of 51.4 µg/mL. Besides, ZnO NPs displayed antioxidant activity where IC50 was 69.2 µg/mL. As well, the minimum inhibitory concentrations of ecofriendly ZnO NPs against the tested MRSA and MSSA isolates were ranged from 32 to 512 µg/mL. Also, their minimum bactericidal concentrations against the tested MSSA was in lower range, 32–1024 µg/mL, than the recorded range, 128–1024 µg/mL, against the MSSA. Also, the crystal violet (CV) assay showed an eradication potential of the biosynthesized ZnO NPs on MRSA and MSSA biofilm in a range of 23.24–73.96% and 6.63–74.1%, respectively. In conclusion, the ecofriendly synthesized ZnO NPs with antioxidant and anticancer activities demonstrated promising inhibitory effect on planktonic growth form of MRSA and MSSA clinical isolates with capability to eradicate their preformed biofilm. To achieve their full potential, future research needs to enhance the synthesis process to make ZnO NPs more uniform and scalable, as well as investigate their action mechanisms at the molecular level.

In recent years, there has been a significant focus on the green synthetization of metal oxide nanoparticles due to their environmentally friendly features and cost-effectiveness. The aim of this study is to biosynthesize zinc oxide nanoparticles (ZnO NPs) through a green method, utilizing crude banana peel extract as reducing and capping agents, to characterize the synthesized ZnO NPs and test their antibacterial activity. ZnO NPs were biosynthesized using the peel extract of banana with various concentrations of zinc acetate dihydrate salt, followed by annealing at 400 °C for 2 h. The synthesized ZnO NPs were characterized using UV–visible spectroscopy (UV-Vis), scanning electron microscopy (SEM), dynamic light scattering (DLS), attenuated total reflectance–Fourier-transform infrared (ATR-FTIR), and X-ray diffraction (XRD). Also, its antibacterial efficiency against different bacterial strains was tested. ZnO NPs were biosynthesized successfully using the extract of Musa Acumniata (cavendish) fruit peel with a UV-Vis wavelength range of 344 to 369 nm and an electrical band gap ranging from 3.36 to 3.61 eV. The size varied from 27 ± 4 nm to 89 ± 22, and the negative zeta potential (ζ) ranged from −14.72 ± 0.77 to −7.43 ± 0.35 mV. ATR-FTIR analysis showed that the extract phytochemical functional groups were present on ZnO NPs. XRD results confirm the formation of a highly pure wurtzite hexagonal structure of ZnO NPs. Moreover, the best obtained size of ZnO NPs was selected for the antibacterial tests, giving the highest inhibition growth rate against Staphylococcus epidermidis (98.6 ± 0.9%), while the lowest rate was against Pseudomonas aeruginosa (88.4 ± 4.4%). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were reported and compared to previous studies. The unique properties of greenly synthesized ZnO NPs and their antibacterial activity have potential for reducing environmental pollution and the use of antibiotics, which may contribute to solving the problem of bacterial resistance. Therefore, studies that aim to design an applicable dosage form loaded with biosynthesized ZnO NPs might be conducted in the future.

Background: This study focused on synthesizing and characterizing mesoporous zinc oxide nanoparticles (ZnO NPs) while evaluating their antibacterial effectiveness against Streptococcus mutans. Their antimicrobial properties were compared to conventional ZnO NPs using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests. Methods: Mesoporous ZnO NPs were produced and analyzed for structural properties. Their antibacterial potential was assessed through MIC and MBC determinations, along with inhibition zone measurements. The test groups included calcined and noncalcined mesoporous ZnO NP solutions (10 mg/mL), standard ZnO NP solution (10 mg/mL), normal saline, and chlorhexidine (CHX) solution (2 mg/mL). Results: All ZnO NP solutions exhibited an MIC of 5 mg/mL, with lower concentrations (2.5 mg/mL and below) showing no inhibition against S. mutans. The MIC for CHX (2 mg/mL) was found to be 0.156 mg/mL. MBC values matched MIC results for all NP solutions (5 mg/mL), whereas CHX had an MBC of 0.312 mg/mL. Among the tested solutions, the calcined mesoporous ZnO NP solution produced the largest inhibition zone (19 ± 0.02 mm), followed by the noncalcined version (17.2 ± 0.03 mm). CHX (14.9 ± 0.02 mm) and ZnO NP solution (15.2 ± 0.13 mm) showed similar inhibitory effects. Conclusion: The study suggests that mesoporous ZnO NP solution possesses strong antibacterial properties against S. mutans, offering a promising alternative to CHX, which is widely used in dental disinfection. These findings highlight the potential application of mesoporous ZnO NPs in various dental procedures, including endodontics, restorative treatments, and periodontal therapy.

The antibacterial activity of zinc oxide nanoparticles (ZnO NPs) has received significant attention worldwide due to the emergence of multidrug-resistant microorganisms. Shiga toxin-producing Escherichia coli is a major foodborne pathogen that causes gastroenteritis that may be complicated by hemorrhagic colitis or hemolytic uremic syndrome. Therefore, this study aimed to evaluate the antimicrobial effect of ZnO NPs against E. coli O26 and its Shiga toxin type 2 ( Stx2 ). Multidrug resistance phenotype was observed in E. coli O26, with co-resistance to several unrelated families of antimicrobial agents. Different concentrations of ZnO NPs nanoparticles (20 nm) were tested against different cell densities of E. coli O26 (10 8 , 10 6 and 10 5 CFU/ml). The minimum inhibitory concentration (MIC) value was 1 mg/ml. Minimum bactericidal concentration (MBC) was 1.5 mg/ml, 2.5 mg/ml and 3 mg/ml, respectively, depending on ZnO NPs concentrations and bacterial cell density. Results showed a significant (P≤0.05) decrease in Stx2 level in a response to ZnO NPs treatment. As detected by quantitative real-time PCR, ZnO NPs down-regulated the expression of the Stx2 gene (P≤0.05). Moreover, various concentrations of ZnO NPs considerably reduced the total protein content in E. coli O26. There was a significant reduction in protein expression with increased ZnO NPs concentration compared to the non-treated control. Scanning electron micrographs (SEM) of the treated bacteria showed severe disruptive effects on E. coli O26 with increasing ZnO NPs concentration. The results revealed a strong correlation between the antibacterial effect and ZnO NPs concentrations. ZnO NPs exert their antibacterial activities through various mechanisms and could be used as a potent antibacterial agent against E. coli O26.

This research paper explores the field of nanobiotechnology, focusing on the design, characterisation, and potential dermal applications of metal oxide nanoparticles (MONPs). ZnO and FeO NPs exhibit distinctive properties that are valuable in dermato‐cosmetic applications and transdermal drug delivery. This study investigates Cannabidiol (CBD) as a capping agent for MONPs synthesis. Employing microwave‐assisted techniques, MONPs were synthesised using either CBD or polyvinylpyrrolidone (PVP) as capping agents. The TEM, SEM, FTIR, and XRD characterisation results confirmed the successful formation of CBD‐capped ZnO and FeO NPs exhibiting an average particle size of 90 and 76 nm, respectively. The cytotoxicity of CBD‐capped MONPs was evaluated on HaCaT cells over a concentration range of 100 to 6.25 μg/mL, which revealed that CBD‐capped ZnO NPs exerted a cytotoxic effect on HaCaT cells (IC 50 85.34±1.17 μg/mL). In contrast, CBD‐capped FeO NPs and PVP‐capped MONPs exhibited negligible cytotoxicity (IC 50 >100 μg/mL). TEM analysis revealed a noticeable structural alteration of ZnO NPs in the supplemented cell culture medium, which could contribute to enhanced NP uptake, thereby explaining the more pronounced cytotoxic effect of ZnO NPs. Therefore, the disparity in cytotoxic responses can be attributed to the protein coating adhering to the NPs surface in a biological medium.

There is a limitation in the range of effectual antibiotics due to the Pseudomonas aeruginosa (PA) infection due to its innate antimicrobial resistance. Researchers have therefore been concentrating their efforts to discover advanced and cost effective antibacterial agents among the ever-increasing PA bacterial resistance strains. It has been discovered that various nanoparticles can be employed as antimicrobial agents. Here, we evaluated the antibacterial properties of the Zinc Oxide nanoparticles (ZnO NPs), which was biosynthesized, being examined on six hospital strains of PA alongside a reference strain (ATCC 27853). A chemical approach was applied to biosynthesize the ZnO NPs from Olea europaea was performed, and confirmed by using X-ray diffraction and Scanning Electron Microscopes. The nanoparticles then applied their antibacterial properties to examine them against six clinically isolated PA strains alongside the reference strain. This process tested for the results of the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). The Growth, biofilm formation and eradication were analyzed. The influence of the differentiating degrees ZnO NPs in regard to Quorom sensing gene expression were further examined. The ZnO NPs exhibited a crystalline size and diameter (Dc) of 40–60 nm and both the MIC and MBC tests revealed positive outcomes of concentrations of 3 and 6 mg/ml for each PA strain, respectively. At sub inhibitory concentration, The ZnO NPs were found to significantly inhibit the growth and biofilm formation of all PA strains and decreases in the biomass and metabolic behavior of PA established biofilms; these decreases varied depending on the dosage. At ZnO NPs concentrations of 900 µg/ml, the expression of majority of quorum sensing genes of all strains were significantly reduced, at ZnO NPs concentrations of 300 µg/ml, few genes were significantly impacted. In conclusion, the treatment of PA and could be other antibiotic resistant bacteria can therefore be approached by using ZnO NPs as it has been uncovered that they withhold advanced antibacterial properties.

Evaluation of ZnO nanoparticles from ‘Monsooned Malabar Robusta Coffee’ husk as a potential antioxidant and biocidal candidate: A sustainable valorization approach

In this work, extracts from okra fruit are used to create zinc oxide nanoparticles (ZnO NPs) in an economical and environmentally friendly manner. During the synthesis process, okra ( Abelmoschus esculentus ) extracts served as stabilizing and reducing agents. Various analytical methods were used to describe the final nanoparticles. The outcomes showed that the produced ZnO NPs primarily exhibited hexagonal shapes, with sizes ranging from 20 to 27 nm in diameter. The cytotoxicity study, conducted on human fibroblast normal HFB4 cell lines, indicated that the IC 50 dose was 227.8 μg·mL −1 . The IC 50 dose of 119.7 μg·mL −1 was found in antitumor effect studies using breast adenocarcinoma Mcf-7 cell lines, revealing a good level of safety for ZnO NPs. Compared to Gram-negative infections, the ZnO NPs were found to have a significantly higher anti-bacterial impact against Gram-positive pathogens. Molecular docking against DNA gyrase A subunit of Bacillus subtilis (PDB ID: 4DDQ) illustrated that the ZnO NPs were interlocked with the active site of 4DDQ by a fitting energy value of −50.91 kcal·mol −1 through three classical hydrogen bonds with Asp96, Thr220, and Ala221. The last one is also generated by the marketing tromethamine drug (TRS), adding some TRS-like character to the ZnO NP inhibitor.

Objective(s): Bacterial biofilm formation causes many persistent and chronic infections. The matrix protects biofilm bacteria from exposure to innate immune defenses and antibiotic treatments. The purpose of this study was to evaluate the biofilm formation of clinical isolates of Pseudomonas aeruginosa and the activity of zinc oxide nanoparticles (ZnO NPs) on biofilm. Materials and Methods: After collecting bacteria from clinical samples of hospitalized patients, the ability of organisms were evaluated to create biofilm by tissue culture plate (TCP) assay. ZnO NPs were synthesized by sol gel method and the efficacy of different concentrations (50- 350 µg/ml) of ZnO NPs was assessed on biofilm formation and also elimination of pre-formed biofilm by using TCP method.Results:The average diameter of synthesized ZnO NPs was 20 nm. The minimum inhibitory concentration of nanoparticles was 150- 158 μg/ml and the minimum bactericidal concentration was higher (325 µg/ml). All 15 clinical isolates of P. aeruginosa were able to produce biofilm. Treating the organisms with nanoparticles at concentrations of 350 μg/ml resulted in more than 94% inhibition in OD reduction%. Molecular analysis showed that the presence of mRNA of pslA gene after treating bacteria with ZnO NPs for 30 minutes.Conclusion: The results showed that ZnO NPs can inhibit the establishment of P. aeruginosa biofilms and have less effective in removing pre-formed biofilm. However the tested nanoparticles exhibited anti-biofilm effect, but mRNA of pslA gene could be still detected in the medium by RT-PCR technique after 30 minutes treatment with ZnO.

This study investigates the green synthesis of zinc oxide nanoparticles (ZnO NPs) using the aqueous extract of the aquatic plant Spirodela polyrhiza (greater duckweed) and evaluates their multifunctional properties. The ZnO NPs were synthesized via a sustainable method and characterized using UV-visible spectroscopy, TEM, FESEM, EDX, FTIR, and XRD analyses. UV-visible spectroscopy confirmed the formation of ZnO NPs with a characteristic absorption peak at ∼349 nm. TEM and FESEM analyses revealed spherical and nonspherical particles ranging from 20 to 70 nm. The antimicrobial activity of ZnO NPs was assessed against three bacterial strains (Escherichia coli, Staphylococcus aureus, and Bacillus subtilis) and three fungal strains (Aspergillus niger, Penicillium chrysogenum, and Candida albicans). Notably, B. subtilis showed a maximum inhibition zone of 18 mm at 100 mg/mL, while A. niger exhibited the highest antifungal response with a zone of 22 mm and an activity index (AI) of 1.15, indicating comparable or superior activity to ketoconazole at higher concentrations. Molecular docking simulations using the crystal structure of B. subtilis YmaH (Hfq) protein (PDB ID: 3HSB) revealed strong noncovalent interactions with Zn atoms of the NPs, particularly involving HIS57 and LEU26 residues. Additionally, ZnO NPs demonstrated a noteworthy photocatalytic degradation (90.4%) of methylene blue dye under sunlight exposure. These results highlight the potential of S. polyrhiza-mediated ZnO NPs for use in antimicrobial therapies and environmental remediation applications.