Preliminary Study On Interactions Between Functionalized Nanoparticles And Protein

Nanomaterials are materials with structure units at the nanoscale (1-100nm) in at least one dimension. They manifest extremely fascinating and useful properties, which make them have potential applications on many fields, especially in biomedicine, including in diagnostics and therapeutics.Magnetic nanoparticles (MNPs) and carbon nanotube (CNT) are two kinds of important nanomaterial in investigation and application. The solubility and biocompatibility of Nanoparticles (NPs) will be improved by modification. As the basic of life matter in vivo, protein plays a significant role in living body. Researches show that, when NPs injected into organisms, it may alter enzyme function or generate unexpected cryptic epitopes in signaling proteins that may trigger some undesirable physiological consequences. Therefore, a clear understanding of how nanomaterials interact with proteins is a prerequisite for nanomedicine and nanotoxicity research.This research consists of the following two parts:In the first part, eight kinds of MNPs coated with COOH, PEG-COOH, NH₂, PEG-NH₂ (50nm, 200nm) were used to investigate interaction with serum proteins. Quantification total protein adsorption to MNPs by Micro BCA protein assay; separation and identification of proteins bound to MNPs by SDS-PAGE and MALDI-TOF-MS; analysis a major MNP-bound protein, bovine serum albumin (BSA), by steady-fluorescence, investigate it's interaction with MNPs.Through the results we make the following conclusions: MNPs of smaller size .bound much more proteins compared to larger particles; MNP-COOH bound significantly more proteins compared to other surface-modified MNPs, and MNPs coated with PEG bound less protein than MNPs without PEG; surface-modified MNPs showed selectivity in protein binding; BSA bound to MNPs with little change in structure.For the second part, interaction between f-MWNTs andα-chymotrypsin (ChT) are studied. Then the mechanism and structure-activity relationships were also analysis. The effect of 80 kinds of f-MWNT onα-chymotrypsin' fluorescence quench are studied. Then, screen the f-MWNT library on the inhibition of a-chymotrypsin activity. Two group f-MWNTs were selected based on preliminary results to investigate the inhibition mechanism.We obtain the following results: The most f-MWNTs bound to ChT are random; analysis of the selected f-MWNTs, we identified five f-MWNTs (29#, 30#, 34#, 35#, 36#) specifically bind to the catalytic site of ChT and inhibit its enzymatic activity competitively.. Analysis structure-activity relationships, they have the same side chain-dibutylamine group. This functional group, in combination with nanotube and adjacent ligand, was likely crucial for targeting the catalytic site of ChT. This is a strong support for the concept that surface chemical modifications on NPs can generate molecular recognition in the context of biomolecular interactions.As a whole, this paper studies the biological effect of NPs on a molecular level, and proves that protein/NPs binding is selectively. Protein is important in vital movement and its conformational structure determines it vital function. Therefore, by modulating the size, shape, surface chemistry of NPs, the protein-binding capability and their in-vivo toxicity can be regulated, biocompatibility be improved, and potential application in nanomedicine be optimized.