Study On The Interactions Between Functionalized Multi-Walled Carbon Nanotubes And Carbonic Anhydrase

Nanomaterials refer to materials with structure units at the nanoscale(1-100nm) in at least one dimension. Their specific and useful properties, such as specific optical, electrical, magnetic, thermal, mechanical, make their wide applications to many fields, especially in nanoelectronics, medicine health and so on. When the carbon nanotubes enter biological systems, the nanomaterials will adsorb the proteins and enzymes immediately, which determines the cell response and the response of the whole system. Carbonic anhydrase is a very important metal enzyme, which is widely present in human kidney, brain retina and other tissues and organs. It can catalyze the reversible hydration of carbon dioxide to produce physiological ion and proton which play an important role in physical activities. The deficiency, abnormal expression or activity lost will lead to pathological changes, such as glaucoma, osteoporosis, epilepsy, cancer and other diseases. So it is important to investigate the interactions between carbon nanotubes and carbonic anhydrase for their applications in drug carrier and new therapeutic techniques, etc.Various surface chemical modified multi-walled carbon nanotubes have been synthesized by combinatorial chemistry. The interactions between f-MWNTs and carbonic anhydrase have been studied by using the method of UV spectrophotometry, steady-state fluorescence, CD, etc. The effects of 80 kinds of f-MWNTs on carbonic anhydrase'activity and fluorescence are studied. From the screening results, we found the changes of carbonic anhydrase'second structure after interacting with f-MWNTs using CD, the adsorption of carbonic anhydrase on f-MWNTs and the inhibition mechanism.Following results are obtained from the inhibition assay results after being interacted with f-MWNTs, the activities of carbonic anhydrase are inhibited. The activities of carbonic anhydrase are decreased to different degrees by various f-MWNTs. The 80 f-MWNTs'fluorescence quenching are in the same level because of the characteristics of CA structure. The CD results of the carbonic anhydrase after interacting with the 8 f-MWNTs which were selected by the inhibition assay showed that the f-MWNTs have no effect on carbonic anhydrase second structure. From the kinetic assay, we know that 8#,15#,16# f-MWNTs can specifically bind to the catalytic site of carbonic anhydrase and inhibit its enzymatic activity competitively. Structure-activity relationship analysis showed that the composites of the functional group and carbon nanotubes were probably crucial for targeting the catalytic site of carbonic anhydrase. This is a strong support for the concept that surface chemical modification by combinatorial chemistry on NPs can generate molecular recognition in the context of biomolecular interactions.