Poly(vinyl alcohol): Physical Approaches to Designing Biomaterials for Biomedical Applications

Poly(vinyl alcohol) is a non-toxic, biosynthetic polymer and biocompatible polymer that has the ability to form hydrogels either via chemical or physical crosslinking. Whilst chemical crosslinking provides greater control on the properties of the resultant hydrogel, physically crosslinked hydrogels or blends with other biocompatible polymers are more suited for biomedical applications. In this paper we report a systematic study on the effect of varying concentrations of PVA, physical methods of crosslinking, and PVA-gelatin and PVA-PVP blends on the physical and mechanical properties of the hydrogels. 1. Introduction In the last few decades there has been a growing interest in biocompatible and biodegradable polymers that are being used to create scaffolds for tissue engineering. To design scaffolds for tissue engineering, the main requirements are high porosity, interconnected porous structure, large surface area, and a microenvironment that allows the cells to adhere, proliferate, differentiate, and retain its phenotype. It is well established that interconnected pores play an important role in cell engineering; however, with increasing porosity there is an inevitable loss in the mechanical properties. A large number of different polymers including hydrogels have been explored for different tissue engineering applications [1]. Poly(vinyl alcohol) is a water soluble, nontoxic, biocompatible polymer that is able to exhibit hydrogen bonding by virtue of the hydroxyl groups present in the repeating units. PVA can form hydrogels either via chemical or physical crosslinking, which exhibit high water content. It can be chemically crosslinked with radiation or aldehydes to form hydrogels using chemicals such as glutaraldehyde, methanol, ethanol, propranolol, and acetone. However, many of these chemicals are not cytocompatible making it an unsuitable method despite being usually cheap and efficient [2–7]. Physical crosslinking methods such as air-drying and cryogelation by repeated freeze-thawing cycles of the aqueous polymer solutions are more biologically compatible but do not allow for the level of control available with other crosslinking methods [8]. PVA three-dimensional networks are of considerable interest in biomaterial applications as the materials can be engineered to closely match human tissues. There has been a significant interest in the cryogenic gelation of PVA as a method of producing hydrogels for biomedical applications. Cryogenic gelation of PVA can lead to a porous structure and the ability for these polymers to absorb surrounding fluid,