Protein based tablets as reversible gelling systems for delayed release applications

Succinylated beta-lactoglobulin (S-beta-lg) was previously shown to be efficient as new excipient for the formation of enteric tablets, suitable for several applications including probiotics delivery. This work investigates the mechanisms leading to S-beta-lg tablets delayed release. Release kinetics were evaluated in vitro. Fourier transformed infra red spectroscopy (FTIR) was used to visualize the effect of dissolution medium on matrix tablet surface. Results demonstrated that tablets release in simulated gastric fluids (SGF) might be due to water/drug diffusion through an in situ formed gel layer, as revealed by FTIR data. As SGF penetrated the tablet, regardless of protein succinylation rate (50% or 100%), molecular rearrangements occurred, allowing the development of an important band located in the 1621-1623 cm(-1) region. This band was characteristic of the formation of protein intermolecular beta-sheets. The gel was showed to be reversible in intestinal conditions, allowing delayed release. While the molecular structure of the gel layer was not depending on protein succinylation rate, it appeared that 100% S-beta-lg tablets showed slower release. This low release was probably related to 100% S-beta-lg lower solubility, lower charge density, and their ability to form stronger intermolecular hydrogen bonds. This work highlights proteins potential for the conception of controlled drug delivery systems. (C) 2012 Elsevier B.V. All rights reserved.