Enteric Delivery of Diclofenac Sodium through Functionally Modified Poly(acrylamide-grafted-Ghatti gum)-based pH-sensitive Hydrogel Beads: Development, Formulation and Evaluation

Background: To prepare and characterize modified Poly(acrylamide-grafted- Ghatti gum). To formulate and evaluate using this grafted polymer pH-sensitive hydrogel beads of diclofenac sodium for enteric delivery. Methods: Polyacrylamide was grafted onto ghatti gum with microwave assistance using ceric ammonium nitrate as redox initiator. Optimization of formulation was done by varying the irradiation time, amount of initiator and acrylamide keeping amount of ghatti gum (GG) as constant. The copolymer was characterized using Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Differential scanning calorimetry (DSC), elemental analysis, viscosity, molecular weight, neutralization equivalent, swelling, biodegradability and acute oral toxicity studies. Results: The copolymer was found to be biodegradable and non-toxic. Further the optimized copolymer was used to generate novel pH sensitive hydrogel. Diclofenac sodium (DS) was loaded into pH sensitive beads by ionotropic gelation technique using AlCl3 as crosslinking agent. Pulsatile swelling study indicated that the copolymer exhibits considerable pH-sensitive behaviour unlike pure gum. In vitro release studies were performed and it was found to be much less from copolymeric beads than from pure ghatti beads. Furthermore, a maximum of 20 % drug was released from copolymeric beads in pH 1.2-5.5 in first 3 h period, while 80 % was released in pH 6.8-7.4 in 8 hr.