Controlling protein-silicone interactions by the modification of silicone elastomers with poly(ethylene oxide)

Despite their special and unique properties, the inherent hydrophobicity of silicone elastomers compromises their use in certain biological applications because interactions with local biology, such as proteins, can be detrimental. It is possible, however, to modify these interactions by tuning the elastomer hydrophobicity through controlling its composition using additives such as poly(ethylene oxide)(PEO), a hydrophilic, protein compatible polymer.; Enzyme entrapment in silicone elastomers serves as a convenient model to study protein silicone interactions because enzyme viability, which is affected by the entrapping matrix composition, serves as an indicator of the rubber biocompatibility. Two enzymes of different nature, lipase C. rugosa and alpha-chymotrypsin were entrapped in silicone rubber, and their activities in the presence and the absence of PEO were examined.; The interaction between the enzymes and the elastomer were found to be dependent on both the nature of the enzyme and the rubber composition. It was found that the interaction between lipase C. rugosa, a lipophilic enzyme, and the entrapping matrix benefits from the hydrophobic nature of the silicone rubber, and leads to active bio-catalytic materials. By contrast, alpha-chymotrypsin was affected negatively by the hydrophobicity of the silicone, and only become stable within the elastomer when PEO was also incorporated within the rubber formulation.; The effects of various factors, including the concentration and chain length of PEO, the enzyme concentration, and the cross-linker concentration on alpha-chymotrypsin activity were studied, following a chemometric approach. Results indicated that the specific activity can be maximized by incorporating a relatively high content of short chain, functional PEO. The enzyme concentration was found to adversely affect the specific activity, while the effect of the crosslinker TEOS was found to be insignificant when PEO was present in the elastomer; however, it did affect the activity positively in the case of simple elastomers.; These results show that it is extremely important to design an elastomer matrix to fit the requirements of a specific protein. With an appropriate balance of hydrophobic and hydrophilic constituents, bioactive silicone elastomers containing either lipophilic (lipase) or hydrophilic (chymotrypsin) enzymes can be prepared.