1.D.73 The Mesoporous Silica Nanopore (SilNP) Family
An MCM-41-type mesoporous silica nanoparticle (MSN) material with a large average pore diameter (5.4 nm) has been synthesized and characterized (Slowing et al. 2007). The in vitro uptake and release profiles of cytochrome c by the MSN were investigated. The enzymatic activity of the released protein was quantitatively analyzed and compared with that of the native cytochrome c in physiological buffer solutions. It was found that the enzymes released from the MSNs are still functional and highly active in catalyzing the oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) by hydrogen peroxide. In contrast to the fact that cytochrome c is a cell-membrane-impermeable protein, it was discovered that the cytochrome c-encapsulated MSNs could be internalized by live human cervical cancer cells (HeLa), and the protein could be released into the cytoplasm. Slowing et al. 2007 envision that these MSNs with large pores could serve as a transmembrane delivery vehicle for controlled release of membrane-impermeable proteins in live cells, which could lead to biotechnological applications including therapeutics and metabolic manipulation of cells.