Ultrasonic-assisted synthesis of sodium lignosulfonate-grafted poly(acrylic acid-co-poly(vinyl pyrrolidone)) hydrogel for drug delivery

A novel method (ultrasound synthesis) has been applied to prepare a sodium lignosulphonate-grafted poly(acrylic acid-co-poly(vinyl pyrrolidone)) hydrogel (SLS-g-P(AA-co-PVP)), and the products were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetry analysis (TGA). The swelling behavior and pH sensitivity of SLS-g-P(AA-co-PVP) hydrogel were investigated. Amoxicillin was used as model drug to study the release properties in enzyme-free simulated gastrointestinal fluids and it exhibited favorable pH-sensitivity and controllable release behavior in vitro. By adjusting the pH value of medium, the release behavior could be controlled. In simulated gastric fluids (SGF) (pH = 1.2 +/- 0.2), the cumulative release rate was up to 51.5% in 24 h and about 32% for 2 h. But for the simulated intestinal fluids (SIF) (pH = 7.4 +/- 0.1), the cumulative release rate reached 84.5% in 24 h and 63.3% after digestion and absorption for 5 h. The amoxicillin encapsulated with SLS-g-P(AA-co-PVP) hydrogel show a better release effect in the simulated intestinal fluids than that in simulated gastric fluids. In a word, the utilization of lignin based synthetic drug-loaded hydrogel is one of the prospective ways to recycle the pulping waste lignosulphonate.