Abstract
Sol–gel methods is a commonly used methods for encapsulation of enzyme and drug, but this method has two disadvantages of using acid or base as a catalyst and being difficult to control pore size of silica material. Even though synthesis under mild condition or silica with controlled pore size in the mesopore region have been reported, it is still difficult to achieve these two characteristics simultaneously. In this work, we chose 10-mer peptides of lysine (K), histidine (H), and block and alternate K and aspartic acid (D) as catalysts for silica mineralization, and silica gels were prepared using the synthetic peptides and a “leave to stand” synthesis method. The resulting silica hydrogels were lyophilized, and their surface areas and morphologies were characterized using the Brunauer–Emmett–Teller (BET) method and field-emission scanning electron microscopy (FE-SEM), respectively. Silica gels prepared by the “leave to stand” method with K10 and H10 exhibited a mesoporous structure with high surface area (576 and 451 m2 g−1, respectively) and pore volume (0.35 and 0.30 cm3 g−1, respectively). SEM images confirmed the mesoporous structure of these gels. We encapsulated fluorescein sodium salt as a model drug within silica hydrogels using K10 and H10 as a catalyst. The silica hydrogel prepared using H10 exhibited faster release of the drug (approximately 2.5-fold) than gels prepared using K10. These results demonstrate that by changing isoelectric point binding between the peptide and pore structure, the synthesized silica hydrogel-peptide composites can be designed to control the release rate of an encapsulated drug.
