Abstract

Porous silica materials made by mild sol-gel reactions are promising host matrixes for encapsulation of biomolecules. The diverse combination of matrix and functional monomers provides great potential to design molecular imprints with a variety of properties. By sol-gel process, we fabricated a global protein conformation sensing system by using 3,3,3-trifluoropropoxy-methoxysilane (TFPM,3F) and (3-heptafluoroisopropo- xy)propal-ethoxysilane (HFIPE,7F) as functional monomers to polymerize with tetroethoxysilane (TEOS). Bovine serum albumin (BSA) was imprinted as a model protein, and the conditions such as pH and silane sol to buffer ratio were optimized for obtaining fluoroalkyl modified silica gels with high optical transparency and uniform distribution of protein by tracing entrapped BSA conjugated with fluorescein isothiocyanate (FITC). The interaction of the protein with both hydrolyzed fluorosilane free monomers and fluoro-modified silica gel was demonstrated by protein binding with 1-anilinonaphthalene-8-sulfonic acid (1,8-ANS), a fluorescence dye with high affinity for hydrophobic pockets. Our results show that hydrolyzed 3F free monomers lead to a remarkable decrease of the fluorescence of 1,8-ANS in the presence of BSA in pH2.5 hepes buffer, suggesting competitive binding of 3F with ANS for protein hydrophobic pockets. Hydrolyzed 7F free monomers exhibit a complex interaction with protein, which may involve potential influence on BSA conformation as well as competitive binding with 1, 8-ANS for BSA. TEOS gels functionalized with 3F/7F are hydrophobic and presumably interact with BSA hydrophobic pockets through the fluorosilanes as evidenced by decreased fluorescence of 1,8-ANS binding with entrapped BSA. 3F is preferred functional monomer over 7F based on gel homogeneity, higher affinity for BSA as free monomer and in gels.