| Our work has focussed on developing silicones that contain hydrophilic residues which mitigate the denaturing effect of silicones at interfaces. In order to study the interaction of proteins with silicones, we chose to use silicones modified with hydrophilic moieties. We have developed hydrophilically-functionalized silicones that can stabilize water-oil interfaces (emulsion stability) and, at the same time, protein structure for extensive periods of time. In addition to commercially available PEO-modified, and aminopropyl-terminated silicones, novel silicones possessing carboxylic acid, biotin, and maleimide groups were synthesized and used in these experiments.; Neutral surfactants of two types were examined in emulsions. PEO-modified silicone stabilized both emulsions and proteins for very extensive periods of time irrespective of the magnitude or type of protein charge. By contrast, although various proteins were examined, the simple alkoxysilane-terminated silicone TES-PDMS stabilized the interface only in combination with albumins of a variety of types. A variety of techniques have been used to clarify the specific interactions responsible for protein stability in this emulsion including interfacial tension measurements, fluorescence microscopy, and enzymatic activity assays.; The interaction of TES-PDMS with albumin proteins proved to be a rather unique, and extremely interesting case; stable water-in-silicone oil emulsions could not be formulated unless TES-PDMS and albumin were used in tandem. All of the techniques employed demonstrated that little (<5%) hydrolysis of the alkoxysilyl groups was taking place when the protein was in contact with the silicone. It is unlikely that covalent interactions between the proteins and silicone polymer were occurring since these interactions would be no more stable than the original Si-O-C bond that existed. In addition it has been demonstrated that the origins of this behaviour is not due to crosslinking of the silicone at the interface, or to hydrolysis of the alkoxysilane. These results suggest that a novel type of interaction may occur between albumin and TES-PDMS---the presence of a binding pocket on the albumin's surface into which the alkoxysilyl groups of TES-PDMS can insert themselves. (Abstract shortened by UMI.)... |
