Study On Self-assembly Behavior Of Protein-polymer Conjugate On Gold Surface

Recently,protein-polymer conjugates,which combine certain protein molecules with specific polymer chains at certain position,have attracted a great deal of attention due to their unique properties of both the protein and the polymer.Protein with the polymer chain combination can improve the solubility of protein,and prolong the half-life,enhance the stability and lower immunogenicity,and widened the scope of the two materials and the application efficiency.This topic will be divided into three parts.We first prepare an initiator,2-bromo-2-methylpropionic acid-2-aminooxy ethyl ester(ABM),which can be linked to the N-terminal of BSA modified by pyridoxal-5-phosphate(PLP),giving rise to amacroinitiator(i.e.,BSA-Br).Second part,BSA-POEGMA conjugateis obtained by atom transfer radical polymerization(ATRP)technique using oligo(ethylene glycol)methacrylate(OEGMA)as monomer?N,N,N',N",N"-Pentamethyldiethylenetriamine(PMDETA)as the complexing agent?CuCl as a catalyst and BSA-Br as macroinitiator,respectively.All products are characterized by Fourier-transform infrared spectroscopy(FTIR),ultraviolet-visible spectroscopy(UV-Vis)and matrix-assisted laser desorption/ionization time of flight mass spectrometry(MALDI-TOF-MS).FTIR and MALDI-TOF-MS results indicate that one POEGMA chain is coupled to the N-terminal of BSA.In the last part,SPR(surface plasmon resonance spectroscopy)was used to study the self-assembly behavior of the prepared BSA-POEGMA conjugate on the surface of the gold plate.The effects of adsorption of BSA-POEGMA conjugate or pure BSA on the adsorption behavior of other proteins(lysozyme(Lys)and Fibrinogen(Fib)were also studied.The results of this experiment indicated that BSA was activated by PLP and successfully modified by ABM to be a macromolecular initiator BSA-Br,and a POEGMA polymer chain was successfully grafted on the nitrogen end of BSA.The prepared BSA-POEGMA conjugate has a good adsorption effect on the surface of the gold plate,that is,the self-assembling process can be completed on the surface of the gold plate.SPR data indicate that there is a decrease in Lys adsorption on BSA-POEGMA compared to pure BSA layer.In contrast,Fib adsorption on the BSA-POEGMA conjugate increase slightly than that on pure BSA.The results clearly show the influence of POEGMA chains on the surface property of BSA molecules,namely connection POEGMA chain can reduce the charge of BSA.