Nanoscopic Characterization of Stearic Acid Release from Bovine Serum Albumin Hydrogels

The release behavior of 16-doxyl stearic acid (16-DSA) from hydrogels made from bovine serum albumin (BSA) is characterized. 16-DSA serves as a model tracer molecule for amphiphilic drugs. Various hydrogel preparation procedures are tested and the fatty acid release from the different gels is compared in detail. These comparisons reach from the macroscopic level, the viscoelastic behavior via rheological characterization to changes on the nanoscopic level concerning the secondary structure of the protein during gelation through infrared (ATR-IR) spectroscopy. 16-DSA-BSA interaction via continuous wave electron paramagnetic resonance (CW EPR) spectroscopy in addition gives a nanoscopic view of small molecule-hydrogel interaction. The combined effects of fatty acid concentration, hydrogel incubation time, and gelation procedures on release behavior are studied via CW EPR spectroscopy and dynamic light scattering (DLS) measurements, which provide deep insight on the interaction of 16-DSA with BSA hydrogels and the nature and size of the released components, respectively. It is found that the release rate of the fatty acid from BSA hydrogels depends on and can thus be tuned through its loading percentage, duration of hydrogel formation and the type of gelation methods. All of the results confirm the potential of these gels as delivery hosts in pharmaceutical applications allowing the sustained release of drug.