One-step synthesis of cellulose/silver nanobiocomposites using a solution plasma process and characterization of their broad spectrum antimicrobial efficacy
Solution plasma process (SPP) is a one-step synthesis technique which expeditiously produces ultra-pure, stable, and uniform nanoparticles in polymer solutions with plasma discharge. Silver nanoparticles (AgNPs) were synthesized in a cellulose matrix as biocomposites by discharging plasma for 180 s at 800 V with a frequency of 30 kHz using a pulsed unipolar power supply into solutions containing cellulose (1–3%) and AgNO3 (1–5 mM). 3D scaffolds of the resulting cellulose/AgNP biocomposites were prepared by lyophilization and cross-linked with UV irradiation. UV-Vis spectroscopy showed a characteristic absorbance maximum in the range of 350–440 nm for the AgNP biocomposites with increase in the intensity of the peaks as the concentration of AgNO3 increased. The peaks exhibited a red shift transition due to the AgNP formation. The nanobiocomposites were pure when examined by FTIR spectroscopy. The 3D scaffolds had a micro-porous structure with pores of (68–74) ± 2 μm in diameter when observed using a FE-SEM instrument equipped with an EDS function. TEM analysis showed that spherical AgNPs in the size range of 5–30 nm were well distributed in the biocomposites of C3Ag3 and C3Ag5. The nanobiocomposites had a broad spectrum of antimicrobial activity against various pathogens with a minimal inhibition concentration of 5.1–20.4 μg ml−1 for bacteria and 81.6–255.0 μg ml−1 for fungi. They killed gram negative bacteria most effectively, but did not affect fungal growth very well, implying their potential as topical antimicrobial agents for the topical treatment of wounds. SPP seems to be the most effective and safest method to synthesize various biocompatible polymer–metal nanoparticle biocomposites.