β-Amino acid containing proteolitically stable dipeptide based hydrogels: encapsulation and sustained release of some important biomolecules at physiological pH and temperature

Two N-terminally protected dipeptides with a beta-amino acid residue form hydrogels at physiological pH and temperature. These two hydrogels have been characterized by various techniques including field emission scanning electron microscopic (FE-SEM), atomic force microscopic (AFM), Fourier transformed infrared (FTIR) spectroscopic and rheological studies. Morphological studies using FE-SEM and AFM suggest the formation of three dimensional nanofibrillar network structures, which might be responsible for the entrapment of water molecules to form gels. The FT-IR study in the gel state is in favour of a beta-sheet-like conformation in the gel state. A rheological study of these two gels indicates the formation of stiff viscoelastic materials. Interestingly, these two gels are proteolitically stable due to the presence of the non-proteinous, but naturally occurring, beta-alanine residue. These gels have been utilized for encapsulation and sustained release of two vitamins (vitamin B-2 and vitamin B-12) over 3 days at physiological pH (7.46) and temperature (37 degrees C). This holds future promise for using these gel-based biomaterials for sustained release of drugs and other biomolecules.