Mais Emad Ahmed

Green synthesis of nanoparticles has emerged as a promising approach to develop cost-effective, biocompatible, and environmentally friendly antimicrobial agents. In this study, we investigated the biosynthesis of selenium nanoparticles (SeNPs) using bacitracin-like inhibitory substances (BLIS) derived from Acinetobacter baumannii. We evaluated their antimicrobial, antibiofilm, and anticancer potential against multidrug-resistant (MDR) pathogens. The synthesized SeNPs were characterized using spectroscopic and imaging techniques, confirming their nanoscale size, hexagonal morphology, surface roughness, and a characteristic absorption peak at 270 nm. Antimicrobial activity was assessed against clinically isolated MDR bacteria and fungi, in which SeNPs demonstrated significant growth inhibition, with a minimum inhibitory concentration (MIC) of 250 mg/mL. Biofilm formation among Acinetobacter baumannii isolates showed variable biofilm-producing capacities, and treatment with SeNPs effectively reduced biofilm formation. Furthermore, gene expression analysis revealed significant downregulation of the mexB efflux pump gene in Pseudomonas aeruginosa following SeNP treatment, indicating a potential mechanism for overcoming antimicrobial resistance. Cytotoxicity evaluation using human lymphocytes demonstrated that SeNPs exhibited minimal toxicity, supporting their biocompatibility. In addition, the nanoconjugate system showed notable anticancer activity against the tested cancer cell lines. In conclusion, BLIS-mediated SeNPs represent a promising multifunctional nanoplatform with potent antimicrobial activities, alongside low cytotoxicity toward normal human cells. These findings highlight their potential application in combating MDR infections and advancing nanomedicine-based therapeutic strategies.

Proteus mirabilis is an opportunistic urinary tract pathogen distinguished by its swarming motility and dimorphic behavior. This study examined the antibacterial potential of native Bulgarian dairy Lactobacillus strains against clinically significant P. mirabilis isolates. By developing and characterizing copper oxide (CuONPs) and zinc oxide (ZnONPs) nanoparticles as antimicrobial agents targeting P. mirabilis, this work contributes to addressing the global challenge of antimicrobial resistance, aligning with the United Nations Sustainable Development Goals (UNSDGs) that aim to reduce infectious disease mortality through innovative therapeutic approaches. Two multidrug-resistant P. mirabilis isolates (M1 and M2) displaying swarming motility were selected for analysis. The antimicrobial activity of Lactobacillus helveticus, a heterofermentative lactic acid bacterium commonly found in dairy products, was evaluated. This strain produces helveticin, a bacteriocin-like inhibitory substance (BLIS) with notable bactericidal activity. CuONPs and ZnONPs were biosynthesized using L. helveticus isolated from yogurt, with strain identity confirmed via 16 S rRNA gene sequencing. Nanoparticles were subsequently extracted and partially purified through 70% ammonium sulfate precipitation. Characterization revealed surface plasmon resonance peaks at 250 nm (CuONPs) and 300 nm (ZnONPs). AFM analysis indicated particle sizes ranging from 15 to 26 nm, while TEM imaging showed predominantly spherical to irregular morphologies between 9 and 20 nm. Cytotoxicity evaluation using the MTT assay demonstrated dose-dependent reductions in the viability of WRL68 human hepatic cells, with up to 60% inhibition at higher concentrations. Notably, both nanoparticle types effectively inhibited P. mirabilis swarming motility, and qPCR analysis confirmed significant downregulation of the rsbA gene, a crucial regulator of this behavior. Overall, green-synthesized CuONPs and ZnONPs derived from L. helveticus displayed potent anti-swarming and antivirulence effects against P. mirabilis. Their ability to suppress virulence-associated gene expression underscores their promise as eco-friendly antimicrobial agents for managing opportunistic pathogens and mitigating multidrug resistance.

The increasing demand for durable and multifunctional separation materials necessitates polymer‐based coatings that combine mechanical robustness with high selectivity. This study aims to develop antibacterial oil/water separation systems that effectively address challenges posed by microorganisms, which can decrease filter effectiveness and impact overall separation efficiency. Metal meshes were coated with titanium dioxide (TiO ₂ ), octadecanethiol (ODT), and polyvinylidene fluoride (PVDF) via spray coating using four formulations: TiO ₂ , PVDF, TiO ₂ /ODT, and TiO ₂ /ODT/PVDF. PVDF‐containing coatings exhibited superior superhydrophobicity, with a water contact angle of 161° and a sliding angle of 3°, attributed to the dense nano‐roughened texture formed upon drying. The ODT contributed to uniform surface coverage, while PVDF imparted excellent adhesion and mechanical durability, maintaining self‐cleaning performance after 50 abrasion cycles. The TiO ₂ /ODT/PVDF formulation demonstrated the highest oil/water separation efficiency and improved oil flux, highlighting the critical contribution of the polymer–nanoparticle interface. Moreover, the nanocomposite coating exhibited pronounced antibacterial activity against S taphylococcus aureus (98.7%) and Escherichia coli (99.2%). These findings underline the potential of polymer‐based nanocomposite coatings as scalable and multifunctional materials for advanced oil/water separation technologies.

Green biosynthesized selenium nanoparticles from Ralstonia insidiosa show potent activity against multidrug-resistant Acinetobacter baumannii , pathogenic Candida spp. and human prostate cancer cells.

Biological synthesis of nanoparticles provides an eco-friendly method for producing bioactive materials characterized by low toxicity and enhanced bioavailability. In this study, selenium nanoparticles (SeNPs) were synthesized using the viable cell filtrate of Staphylococcus haemolyticus. Biosynthesis with bacterial cell filtrate uses extracellular enzymes, proteins, and metabolites as reducing and capping agents to convert a selenium precursor (commonly sodium selenite, Na₂SeO₃) into elemental selenium nanoparticles (Se⁰). Advantages include mild conditions, eco-friendliness, and often improved biocompatibility. Characterized by UV–Vis spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), and zeta potential analysis. The antimicrobial potential of SeNPs was assessed against biofilm-forming Staphylococcus aureus using a microdilution MIC assay. The SeNPs exhibited broad-spectrum activity, effectively inhibiting Gram-positive and Gram-negative bacteria, as well as Candida species. They also demonstrated strong antioxidant activity and low cytotoxicity, highlighting their safety profile. Furthermore, synergistic assays revealed that combining SeNPs with conventional antimicrobials enhanced their inhibitory effects, including against multidrug-resistant strains. At the molecular level, the clfB gene was detected by PCR, and real-time PCR revealed significant modulation of its expression following SeNP treatment, suggesting interference with biofilm formation. Cytotoxicity assays further indicated that SeNPs exhibited low toxicity toward normal fibroblast (HdFn) cells while showing improved anticancer activity against PC3 cells compared to free drug or neat selenium nanoparticles.