pH-sensitive hydrogels based on bovine serum albumin for oral drug delivery

pH-Sensitive bovine serum albumin (BSA) hydrophilic microspheres were prepared by free radical polymerization of methacrylate derivatizedBSA and methacrylic acid sodium salt. Incorporation of both monomers in hydrogels was confirmed by Fourier transform infrared spectroscopy.Morphological analysis by scanning electron microscopy showed spherical shape and porous surface of all prepared samples. The microspheresshowed high water affinity at neutral pH values and a narrow dimensional distribution. Network density of hydrogels depends on derivatizationdegree (DD%) of BSA and/or concentration of modified BSA in the polymerization feed. In order to employ the prepared samples such as pHsensitivehydrogels, in vitro release studies, in media simulating biological fluids, were performed using diflunisal (DF) and -propranolol (PR)as model drugs. Experimental data showed that the release profiles depend on drug–matrix interactions and diffusional limitation awardable tocrosslinking degree of microparticles. -Propranolol is quickly released at pH 1.0 and a complete release after 1 h at pH 6.8 was observed. In thecase of diflunisal pH-sensitive release was observed. At pH 1.0 low amounts of drug were released (w/w < 10% after 2 h). When the pH is 6.8, thediflunisal release increased in the amount (w/w > 75% after 24 h).