Surface Modified With Smart Polymer And Its Controllability Of Protein Adsorption

The adsorption of proteins on surfaces is one of the key problems in biomedicalmaterials, and has attracted considerable attentions. Mostly the functions are realized bymodifying the surfaces of biomaterial with polymers, in which smart polymers arewidely employed due to their special properties that response to external environmentalchanges (temperature, pH, ion strength, electric field and so on). Through introducingsuch kind of materials onto the bio-surfaces, some functions such as protein separationand purification, cells culture and separation, drug delivery, tissue engineering can berealized. This thesis adopted two methods to modify silicon and Fe3O4nanoparticles,and studied adsorption of protein on the modified materials.1. We have used surface-initiated atom transfer radical polymerization (SI-ATRP)to modify surfaces with poly(2-(dimethylamino ethyl) methacrylate)-block-poly(methacrylic acid)(PDMAEMA-b-PMAA) diblock copolymer. The pH-responsiveproperties and the adsorption of lysozyme on the modified surfaces were systematicallystudied. In a wide range of pH, the surfaces modified with PDMAEMA and PMAAshowed anti-fouling and fouling properties of lysozyme, respectively. WhilePDMAEMA-b-PMAA diblock copolymer marriaged the two opposite properties, anddemonstrated a pH-controllable adsorption of lysozyme. The controllable adsorptionproperty could be explained by the electrostatic state and swelling of the polymerbrushes. Very interestingly, the adsorption of lysozyme on PDMAEMA-b-PMAAdiblock copolymer also depended on the thickness of the outer PMAA block (lPMAA).When lPMAA≤10nm, the adsorption amount of lyzoyme on modified surfaces could becontrolled stepwisely by changing pH. When lPMAA>10nm, the trend of the adsorptionof lysozyme on the dibock copolymer brushes with pH was similar to that on PMAA homopolymer brushes.2. Passerini three component reaction was first used to modifiy Fe3O4nanoparticles with halide and alkynyl groups, in which halide can initiate ATRP reactionand alkynyl groups could take part in Click reaction. Thus ATRP and Click reactioncould be proceeded in one pot, and Fe3O4nanoparticles could be modified withtemperature responsive polymer poly(N-isopropylacrylamide)(PNIPAAm) and theaffinity ligand of concanavalin A (Con A)—β-glucose in one step. The changes ofabsorbance by fouriertransform infrared spectroscopy (FTIR) and particle size bydynamic light scattering (DLS) proved the successful modification of the nanoparticles.The results showed that the size of nanoparticles modified with PNIPAAm and glucosewas larger at25℃than that at40℃with temperature responsive behavior. In proteinadsorption tests, after adsorbing Con A, the nanoparticles became larger, whichindicates that the modified nanoparticles can bind Con A.In conclusion, when the material surfaces are modified with smart polymers, wecan control the protein adsorption on modified surfaces by changing the compositionsof the surfaces and the environmental stimulus. Our work provides some theoreticalbasis and new methods for surface modification and controlling protein adsorption onbiomaterials, which has potential application in the separation and purification ofprotein and biosensor.