Biodegradable polymers have become increasingly important because they can be synthesized biologically and are not petrochemically based.  Poly (3-hydroxybutyrate) (PHB), a biopolyester produced by a wide variety of microorganisms as an intracellular carbon and energy storage material, can be differentiated from all other available biodegradable plastics by their water insolubility and resistance to hydrolytic degradation. In general they exhibit good oxygen permeability and are both biocompatible and nontoxic, making them suitable for medical applications such as drug delivery and tissue engineering. Poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-HHx) is a new copolymer of PHB that not only possesses all the excellent properties of PHB but also overcomes its stiffness and brittleness caused by the near perfect stereoregularity and high crystallinity.  Hence the PHB-HHx copolymers are much more easily processed.In our present research, we studied the formation of thermally reversible gels from PHB-HHx in various solvent systems and under different thermal conditions. These gels, which are stable at room temperature, were investigated by Ultraviolet-visible (UV-vis), Raman and Fourier Transform Infrared (FTIR) spectroscopy to identify changes in conformational structure due to the gelation process. The resulting spectra indicate the existence of conformational disorder in the gels, although this appeared to be lost gradually upon drying at room temperature. In addition, we found that the freeze-dried gels, which have 3-D interconnected nanofibrous networks with fiber diameters of 40-300 nm and resemble the structure of the natural extracellular matrix, retained some of the conformational disorder that was induced during gelation.  We also demonstrated that the HHx content in the copolymers have a large effect on the gel formation and the conformational structure in the gels. This is extremely important because there is an overarching need for non-toxic, biodegradable, synthetic polymers that exhibit thermoreversible gelation and hence can be used as micro-carriers for cells insuring long term survivability and immunoprotection. Although biological polymers have been used extensively in the past, there are associated risks of transmission of bacterial and fungal infections and hence there is a need for synthetic, biodegradable polymers that undergo

Thermoreversible gelation of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) in different solvent systems: Toward an understanding of conformational changes in the gelation process

247th National Meeting (2014)

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