Α {Silk@Gallic-Acid} hybrid material with controllable antioxidant hydrogen-atom-transfer activity

Abstract

Silk fiber, often acclaimed as the pinnacle of textile materials, finds contemporary applications in the textile industry, health, and cosmetics. Gallic acid (GA) is a well-established natural antioxidant. In the present study, a novel hybrid material SFd@GA was conceptualized and produced via surface grafting of GA onto degummed silk-fibers (SFd). Successful covalent-grafting of gallic acid onto the silk fabric surface was confirmed through Fourier-transform infrared, Raman, thermogravimetric analysis (TG-DTA), and scanning electron microscopy (SEM). electron paramagnetic resonance spectroscopy demonstrates that gallic moieties grafted on SFd@GA retain their radical/redox activity. The antioxidant capacity of the hybrid material SFd@GA was validated by quantitative analysis of antioxidant hydrogen-atom-transfer (HAT) to DPPH radicals. Our data reveal a 550% increase in antioxidant-HAT activity of SFd@GA versus natural intact silk fiber, and a 1400% increase in antioxidant-HAT activity compared to the degummed silk fiber. The paramount discovery of the present work lies in the capacity for repeated utilization of the hybrid material SFd@GA, without any discernible compromise in its antioxidant-HAT activity. Specifically, we show that SFd@GA can be employed for at least 15 consecutive cycles, retaining >98% of its HAT efficiency, for up to many days of storage under ambient conditions. We discuss this expositional performance via the controllable Hat-activity process that we propose.