The lyophilized 6mer and chimera proteins
were dissolved in double distilled water and then filtered with
5.0 lm syringe filters (Millipore, MA) to remove insoluble precipitates.
The protein concentration was measured by bicinchoninic
acid assay (Thermo Scientific, MA). 174 ll of 0.5 mg ml–1 protein
solutions was buffered to pH 7.0 by adding 13 ll of 1 M bis-tris
propane and 7 ll of 1 M citric acid buffers. 6 ll of prehydrolyzed
tetraethoxysilane (TEOS) solution (prepared by mixing 2.23 ml of
TEOS (Sigma-Aldrich, MO) with 7.76 ml of 50% ethanol/water solution,
100 ll of 1 M HCl and standing at room temperature for
15 min) was added and mixed thoroughly.