BSA And Protamine Release From Nocc/alginate Hydrogels: Comparative Study Between Two Biomolecules With Different Isoelectric Points.

A pH sensitive hydrogel of calcium cross-linked alginate-NOCC (N, O-carboxymethyl chitosan) was synthesized containing water-soluble polymers PEG (polyethylene glycol) and/or PVP (polyvinylpyrrolidone). The gels prepared were separately loaded with two biomolecular proteins, Bovine serum albumin (BSA) and Protamine via physical entrapment method. The swelling studies of the gels and the release profiles for these two drugs possessing different isoelectric points pI?s (4.5 and 10 respectively) were investigated with respect to variation in the pH of the bathing medium as well as the drying procedure and the PEG and PVP content of the hydrogel. For a typical gel composition alginate-to-NOCC weight ratio 3:3, as the pH of the release media increased from 1.2 to 7.4, the release rate of both biomolecules increased. The increase of pH has a more dramatic influence on Protamine as a result of its higher pI (10.0) compare to that of BSA (4.5). The rate of swelling and drug release were decreased for air-dried beads in comparison with the freeze-dried one. PVP was found to be more effective in reducing the burst release of proteins in acidic conditions (pH 1.2). In addition, the absorption of the drugs into the hydrogels slightly increased when 1% (w/v) PVP was added. As the PVP content was increased, the absorption of Protamine and was BSA decreased. The addition of PEG did not significantly affect the properties of the hydrogel. The interaction between alginate/NOCC gel and the high pI proteins could potentially be exploited to generate new protein delivery systems.