Lignin directed synthesis of noble metallic bimetallic nanocomplexes for developing antimicrobial nanocoatings

Abstract

Lignin has intrinsic antimicrobial and antioxidant properties, which makes it a material of potential interest. It is mainly derived as a waste from paper and pulp industries and is an underutilized biopolymer. In this work, lignin was utilized as a matrix and reducing agent to synthesize gold/silver based monometallic and bimetallic nanocomplexes. Lignin was used as a sole agent for capping and stabilizing the lignin-metallic/ bimetallic nanocomplexes, using a one-pot method. The synergistic antimicrobial and antioxidant properties of the lignin stabilized nanoagents were then explored. Various analytical techniques were utilized to characterize the synthesized lignin based nanocomplexes. The mechanism behind the antimicrobial activity of the nanocomplexes was also explicated. Therapeutic photosensitizers were then conjugated on to the surface of the developed nanocomplexes for achieving the desired results in a controlled and effective manner. The developed nanoconjugates were tested for their photophysical properties. The developed nanoconjugates were doped inside biocompatible hydrogels to develop a nanocomposite hydrogel. The nanocomposite hydrogel was subjected to pH responsive study, rheological studies and scanning electron microscopy. After the characterizing the nanocomposite hydrogel, it was subjected to antimicrobial photodynamic therapy (APDT) studies. This was followed by the development of lignin-based gel emulsion which acted as a bioinspired carried for the nanoconjugates. The developed nanocoatings were tested for their antimicrobial properties in dark as well as in light conditions for APDT studies. This study is a contribution to the development of various antimicrobial products in order to combat the increasing risk of microbial infections. newline