May 11, 2010
Chiral mesoporous silica behaves as a carrier of chiral drugs
Mesoporous silicas with well defined nanostructures have been widely employed as controlled drug-release and drug-delivery systems. Chiral mesoporous silicas can be synthesized using achiral templates and a chiral metal complex as a co-template. Loaded enantiomers of chiral drugs show different release profiles due to the existence of local chirality on the pore wall surface of chiral mesoporous silica materials.
Inspired by the synthesis of chiral molecular solid material using an optically pure metal complex as the template, researchers from Nanyang Technological University, Singapore, and Jilin University, China, have proposed that the chirality of the metal complex could also be transferred to mesoporous silica matrix.
Testing the idea
A chiral cobalt complex (Λ-[Co(+)(chxn)3]I3) was introduced to the synthesis of mesoporous silica materials with various structures and pore diameters including MCM-41, SBA-15 and SBA-16. The team was delighted to find that enantiomers of the chiral drug (metoprolol) exhibited different release rates when these materials were used as carriers, which implied the formation of a chiral environment in the mesoporous silica matrix.
Subsequent characterization using vibrational circular dichroism (VCD) spectroscopy revealed that the chiral entities of these chiral mesoporous silica materials can be assigned to the building blocks of silica, namely chirally distorted SiO4 tetrahedrons or Si(OSi)4.
The study offers a new protocol for the synthesis of chiral mesoporous materials. The chirality and porosity of these pure silica materials could be exploited in many fields such as asymmetric discrimination, chiral drug delivery and enantio-catalysis.
The researchers presented their work in Nanotechnology.
About the author
Zhen Guo is currently a third-year PhD student in Prof. Yanhui Yang's group at the School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore. The group's research interests include the development of functional nanoporous materials and heterogeneous catalysis over metals and metal oxides. Guo is exploring chiral hydrogenation using the chiral mesoporous silica materials described in the study.