Influence of cross-linkers on the properties of cotton grafted poly (acrylamide-co-acrylic acid) hydrogel composite: swelling and drug release kinetics

Abstract

Cross-linker plays a crucial role in monitoring water holding and drug release properties of a hydrogel system, an essential requirement for smart wound dressings. Present study is focused on the influence of cross-linkers poly ethylene glycol (PEG) and N,Nʹ-methylene bisacrylamide (MBAAm) on the properties of poly (acrylamide-co-acrylic acid) hydrogel grafted over the cotton fabric to form composite for medicated dressings. Fourier transform infrared spectroscopy (FTIR) confirms the grafting of hydrogel on the cotton fabric. Uniform hydrogel layer on the cotton surface is obtained under scanning electron microscopy (SEM). Swelling of the composite prepared using PEG follow first-order kinetics at acidic and neutral pH whereas second-order kinetic model at pH 8.5 while that prepared using MBAAm follow second-order kinetic equation at all the pHs studied. The swelling kinetics is also governed by Peppas model at all pHs. Release of gentamicin sulphate from both the composites are studied in phosphate buffers having pH 4.5, 7 and 8.5 at 37 ± 0.1 °C and observed that it is fastest in phosphate buffer having pH 7. On fitting drug release data into Peppas model, first and second-order kinetic equations, it is found that drug release is diffusion controlled and follows Fickian diffusion mechanism in case of the composite prepared by using PEG as cross-linker, whereas it is controlled by diffusion as well as chain relaxation in case of the composite prepared by using MBAAm. Mechanical testing using universal testing machine supports a higher mechanical strength of the hydrogel composite as compared to its film.