Thermosensitive hydrogel loaded with biosynthesized silver nanoparticles using Eucalyptus camaldulensis leaf extract as an alternative treatment for microbial biofilms and persistent cells in tissue infections

Abstract

Biofilms play a key role in the development of chronic tissue infections and antimicrobial resistance. In situ-forming thermosensitive hydrogel containing biosynthesized silver nanoparticles using aqueous Eucalyptus camaldulensis leaf extract (bio-AgNPs) was developed as an efficient anti-biofilm agent with a sustained release for tissue infection treatment. The formulation with 24% poloxamer 407, 5% poloxamer 188, and 1% hydroxypropyl methylcellulose demonstrated gelation temperature at 33 °C and homogeneous dispersion of bio-AgNPs throughout three-dimensional networks. Pharmaceutical properties of bio-AgNPs-loaded hydrogel presented shear-thinning behavior and zero-order release profile. The formulation showed broad-spectrum antimicrobial activity and comparable effects with existing antibiotics against important pathogens, including Gram-positive, Gram-negative bacteria, and fungi. The formulation at 1/8–1/2 minimum inhibitory concentrations (MIC) significantly inhibited biofilm production in all tested pathogens (p < 0.05). Confocal laser scanning microscopy images clearly illustrated dead cells within mature biofilm upon the treatment with the formulation at 2MIC for 4 h. The formulation effectively scavenged free radicals and decreased nitric oxide production up to 98%. Decrease in mRNA levels of inflammation-related enzymes and pro-inflammatory cytokines in lipopolysaccharide-stimulated RAW 264.7 cells confirmed the formulation as a potential anti-inflammatory agent. The findings suggested that bio-AgNPs-loaded hydrogel represents a promising therapeutic approach for tissue infections.