Application Of Hydrophobic Adjustable Binary Mixed Polymer Brush In Controlling Protein Adsorption

Controlling the hydrophobic interaction between surfaces and proteins in an aqueous environment is important for it could control the protein adsorption which is the first step of surface fouling.In this work,binary mixed polymer brushes based on poly[(2-methyl-2-oxazoline)-random-glycidyl methacrylate](PMOXA-r-GMA)and poly(glycidyl methacrylate)-block-poly(N-isopropylacrylamide)-block-polystyrene(PGMA-b-PNIPAM-b-PSt)were used as thermoresponsive coating to control the protein adsorption.Firstly,PMOXA-r-GMA was synthesized via cationic ring opening polymerization of 2-methyl-2-oxazoline followed by its copolymerization with glycidyl methacrylate(GMA);PGMA-b-PNIPAM-b-PSt was synthesized by reversible addition-fragmentation chain transfer polymerization of GMA,N-isopropyl acrylamide(NIPAM),and styrene(St)sequentialy.Then the mixed brushes were fabricated successfully by spin coating the mixture of PMOXA-r-GMA and PGMA-b-PNIPAM-b-PSt solutions onto silicon or glass substrates followed by annealing protocol.Afterwards,the investigation for adjusting the hydrophobic property of mixed brushes was performed.The results showed that the behavior of mixed polymer brushes coating with optimum molecular mass of PSt block could be changed from hydrophilic to hydrophobic with switching the environmental temperature higher or lower than the lower critical solution temperature(LCST)of PNIPAM.Finally,the protein adsorption on mixed polymer brushes was investigated by fluorescein isothiocyanate-labelled proteins assay and ellipsometrys.The results showed that under optimum molecular mass of PSt block,mixed brushes could adsorb proteins in large quantities below the LCST of PNIPAM,and display the resistance to protein adsorption above the LCST of PNIPAM.PMOXA-r-GMA/PGMA-b-PNIPAM-b-PSt with different grafting density was fabricated on silicon wafers via annealing protocol by adjusting the concentration of PMOXA-r-GMA/PGMA-b-PNIPAM-b-PSt mixed solution.Afterwards,the relationship of composition/morphology and grafting density of coatings were investigated by X-ray photoelectron spectroscopy and atomic force microscopy,respectively.The results showed that the roughness of coating would increase with increasing the grafting density.The WCA measurement was used to represent the hydrophilic/hydrophobic property,the results indicated that the ability of reversible transition between hydrophilic and hydrophobic behavior could be adjusted by the varition of the grafting dendity of polymers,and the degree of this transition could keep constant when the grafting density reached to 0.17 chain/nm2.Finally,the bovine serum albumin,fibrinogen,and lysozyme adsorption on these coatings was investigated by fluorescein isothiocyanate-labelled proteins assay and ellipsometrys.The results indicated that the hydropilic and hydrophobic behavior of mixed brushes determined the protein adsorption behavior,the more hydrophobic the surface is,the more amount of protein it adsorbs.