Thermo- and pH-responsive cotton gauzes as drug delivery system obtained by gamma radiation and chemical initiator

Abstract

The grafting of stimuli-responsive polymers into medical devices to create functional materials has attracted the attention of scientific community. The capacity of these polymers to change its conformation reversibly as function of variables of the environment in which it is applied, is well taken into account to create drug delivery systems. Because cotton gauzes are materials of priority use in biomedical area, and they are susceptible to develop biofilm on its surface contaminating skin wounds. In this work it is proposed the modification of cotton gauze with a dual stimuli-responsive copolymer, composed by two monomers such as methacrylic acid and N-isopropylacrylamide, through a grafting copolymerization induced by chemical initiator and gamma radiation. Experimental conditions were evaluated for each method. Grafting was verified by infrared spectroscopy (FTIR-ATR) and scanning electron microscopy (SEM) as well as its thermal behavior was determined through thermogravimetric analysis (TGA). Critical pH was confirmed by potentiometric titrations finding a value of 4.7 for grafted cotton gauzes and their critical temperature ranging between 31–34°C, which was determined by water uptake as function of temperature. The loading and release of norfloxacin were tested, finding that grafted gauzes exhibited affinity for this drug and it is released under simulated physiological conditions of temperature and pH. Norfloxacin-loaded gauzes show their efficiency inhibiting E. coli and S. aureus growth in a contaminated environment, at different pH values. This improvement of cotton gauzes can serve as barrier to avoid the formation of biofilm in surgical conditions and for wound healing.