GREEN-SYNTHESIS OF SILVER NANOPARTICLES EMBEDDED INTO PVA/CNC ELECTROSPUN NANOFIBERS CO-LOADED WITH EUCALYPTUS OIL FOR BIOMEDICAL APPLICATIONS AGAINST K. pneumoniae AND S. aureus

Abstract

Pneumonia is the leading cause of morbidity and mortality worldwide, particularly in low- and middle-income countries. According to the World Health Organization, it accounts for 15% of deaths among children under five, exceeding 700,000 fatalities annually. In the elderly over 65 years, it causes over one million deaths each year, with rising fatality rates. Multidrug-resistant pathogens, such as Klebsiella pneumoniae and Staphylococcus aureus, intensify the crisis, outpacing the development of antibiotics. This study prepared and characterized electrospun PVA/CNC nanofibers embedded with green-synthesized silver nanoparticles and eucalyptus oil, combining natural antimicrobials, biopolymer nanofibers, and eco-friendly nanotechnology for safe, nonantibiotic therapy against pneumonia-causing pathogens. The study objectives included green-synthesis of AgNPs using ELE and characterized using FTIR, SEM, TGA, TEM and XRD; extracting essential oil (EO) from eucalyptus leaves via steam-distillation and identify the phytochemical constituents and functional groups; extracting cellulose from the ELF, synthesizing CNCs via acid hydrolysis and characterize using FTIR, SEM, TGA, TEM and XRD; fabricating and optimizing electrospun PVA/CNC nanofibers and develop composite electrospun nanofibers comprising PVA, CNCs, AgNPs, and EO (PVA/CNC/AgNPs@EO), and characterize using FTIR, SEM, TGA, and XRD; evaluating the antibacterial activity of the prepared samples against K.pneumoniae, and S. aureus, and investigate their synergistic effects in enhancing antimicrobial performance. The study's findings showed that the green-synthesized AgNPs exhibited characteristic surface plasmon resonance peaks at 420 and 422 nm, as confirmed by UV-Vis spectroscopy. FTIR analysis confirmed the involvement of O– H, C=O, and C–O functional groups in the reduction and stabilization of AgNPs. TEM micrographs revealed predominantly polydispersed spherical AgNPs with diameters ranging from 5 to 20 nm. XRD confirmed a face-centered cubic crystalline structure. Phytochemical screening of steam-distilled EO confirmed the presence of terpenoids, mainly 1,8-cineole, α-pinene, and limonene, while the FTIR established characteristic absorption peaks of monoterpenes. The isolated cellulose from ELF exhibited a crystallinity index increase from 33.88% (ELF) to 77.45% (CNCs) after alkali, bleaching, and acid hydrolysis treatments. Electrospun PVA/CNC nanofibers exhibited a bead-free morphology under SEM and demonstrated enhanced crystallinity, as confirmed by XRD. Incorporation of CNCs increased hydrogen bonding, evidenced by FTIR peak shifts, and raised the crystallinity index from 24.93% (PVA) to 54.08% (PVA/CNC). Electrospun PVA/CNC/AgNPs@EO composite nanofibers exhibited a uniform, bead-free morphology with an improved crystallinity index of 69.40%, confirming structural reinforcement. FTIR confirmed the successful incorporation of EO and AgNPs, while SEM micrographs revealed that the nanoparticles were evenly distributed within the polymer matrix without aggregation. TGA analysis demonstratedimproved stability which prevent premature degradation, ensuring sustained functional performance, with char residue increasing to 21.7% at 800 °C. Antibacterial evaluation showed inhibition zones of 10–20 mm (S. aureus) and 9–19 mm (K. pneumoniae) for 6% AgNPs, whereas EO alone recorded inhibition zones of up to 19 mm. Electrospun PVA/CNC/AgNPs@EO composite nanofibers achieved inhibition zones up to 23 mm, demonstrating synergistic enhancement compared to individual samples. The results of this research establish a synergistic interplay among the samples, highlighting the potential of the developed nanofibers in biomedical applications such as pneumonia causing pathogens, implant coatings, and respiratory healthcare masks.