Copper (II)-silk fibroin hybrid flowers with Antibacterial activity and selective cytotoxicity

Antibacterial activity with selective cytotoxicity is of immense research interest. Taking the advantage of Cu ions, a facile one-pot reaction for the synthesis of organic-inorganic hybrid flower-mimetic silk microsphere is proposed. Silk fibroin molecules act as nucleation site for copper phosphate crystals induce the growth of flower petal like micrometer-sized Cu-silk microspheres. Typical bacterium such as Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) are used to investigate the antibacterial potentiality of the synthesized material. The sensitivity of metallic flower is dependent on interface exhibited by bacterial membrane; Gram positive bacteria reveals less sensitivity due to the presence of thicker peptidoglycan layer compared to Gram negative. In presence of ABTS [2,2’Azino-bis(3- ethylbenzthiazoline-6-sulfonic acid)], metallic flower exerts peroxidase-like activity based on Fenton-like reaction mechanisms that can also cause antibacterial propensity. Contact of high Cu concentration causes bacterial membrane pitting results in enhanced permeability. In contrast, the metallic flower reveals less toxicity to mammalian cells imparting selective toxicity of the synthesized material; indicating promising quality to serve as therapeutic delivery carrier or biocompatible disinfect material coating in medical device.