Effects of Silver and Zinc Oxide Nanoparticles on Tyrosine’s Enzymatic conversion to Melanin

Abstract

In this research study metallic silver nanoparticles (tyrosine and citrate reduced AgNPs) and ZnO–NFs were synthesized and incorporated in melanogenesis pathway (with and without reduced glutathione) to study their effects on synthetic melanin pigment. The melanin pigment shields from intense UV rays and acts as a protection shield against it. Synthetic melanin was produced by enzymatic conversion of amino acid L–Tyrosine using Agricus Bisporous mushroom tyrosinase at pH 5 and 7 following the traditional Raper Mason melanogenesis pathway. The physiochemical and optical properties of as prepared and modified synthetic melanin pigments were assessed using spectroscopic techniques such as RAMAN, UV-visible, and FTIR. EDAX and SEM analysis was used to assess the elemental composition and surface morphology. Zeta potential analysis was used to ascertain the surface charge of modified controlled melanin pigments and a free-radical scavenging assay with DPPH was performed to estimate the antioxidant activity of synthetic melanin pigments. Color changes and UV absorption spectrums confirmed the successful formation of AgNPs, ZnO–nanoflakes, and melanin pigments. Direct band gap of ZnO–NFs and AgNPs was determined by Tauc’s plot. FTIR spectrum revealed the characteristics bands for each sample. SEM Images depict the spherical and nanoflakes morphology of silver and Zinc oxide nanoparticles respectively. The tetrahedral surface morphology of as prepared melanin pigment gets modified on incorporation with AgNPs and ZnO–NFs and was confirmed by SEM analysis. ZnO nanoflakes incorporation to melanin results in formation of darkest black pigment and gives cuboid morphology of melanin pigment with particle size distribution ranges between 110-900 nm. Keywords: Skin color, UV–protection shield, Melanin pigment, Tyrosinase Activity, Synthetic melanin. Antioxidant activity of melanin.