Shwetha B Nagarajan, Anuradha Jayaraman, Sanjeevi Ramakrishnan
Nosocomial respiratory infections caused by multidrug-resistant (MDR) pathogens pose a major clinical threat, necessitating alternative antimicrobial strategies beyond conventional antibiotics. Green-synthesized nanomaterials offer a sustainable route for developing novel antimicrobial agents. This study aimed to perform the first direct, side-by-side comparison of plant-mediated selenium (SeNPs) and titanium dioxide nanoparticles (TiO₂NPs), in both free and alginate-encapsulated forms, against MDR nosocomial respiratory pathogens under identical experimental conditions. Selenium and titanium dioxide nanoparticles were synthesized using aqueous plant extracts and subsequently encapsulated within an alginate biopolymer matrix to enhance stability. Nanomaterials were characterized for morphology, crystallinity, and surface functional groups. Antibacterial and antifungal activities were assessed using agar diffusion assays, while minimum inhibitory concentrations (MICs) were determined to evaluate dose-dependent effects. Selenium nanoparticles exhibited superior antibacterial activity (20-21 mm inhibition zones) compared to titanium dioxide nanoparticles (9-18 mm). Alginate encapsulation reduced initial inhibition but supported sustained antimicrobial action. Against Aspergillus fumigatus, selenium-based systems showed strong activity (15-19 mm), with titanium-based variants displaying moderate inhibition (12-18 mm). MIC assays revealed > 0% bacterial suppression at 100 µg ml⁻¹. Plant-derived selenium and titanium dioxide nanomaterials, particularly selenium-based systems, demonstrate promising antimicrobial potential for further development against MDR nosocomial respiratory pathogens.