A green chemistry approach for synthesizing thermostable antimicrobial peptide-coated gold nanoparticles immobilized in an alginate biohydrogel

Abstract

Developing rapid, green, and cost effective approaches for synthesizing metal nanoparticles with biochemical and biomedical applications is currently a top priority. Here, we report a rapid synthesis of gold nanoparticles (AuNPs) in an alginate polymer using thermostable antimicrobial peptides. At a high temperature, these antimicrobial peptides acted as reducing agents and converted Au³⁺ to Au⁰ in 15 min while retaining their antimicrobial activity. The alginate polymer acted as a stabilizing agent for this reaction. The resulting Au–peptide–alginate biohydrogel was characterized by UV-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). TEM analysis showed AuNPs of less than 25 nm in diameter, with peptides present on their surfaces. The Au–peptide–alginate biohydrogel showed effective catalytic activity in reducing 4-nitrophenol and hexacyanoferrate(III) in the presence of sodium borohydride with durable reusability. The Au–peptide–alginate biohydrogel was also demonstrated to have antimicrobial activity against pathogenic bacteria. The method presented here for the synthesis of a metal–polymer conjugate is eco-friendly and robust. Large-scale production of the Au–alginate polymer would be possible in a very short time using this method, which makes it potentially useful for biomedical and industrial applications.