Binary Polymer Brushes Of Poly(2-Methyl-2-oxazoline)/poly(4-vinyl Pyridine)for Controlled Protein Adsorption

Controlling the protein adsorption and desorption on material surfaces in the fields of biomaterials and medical science is very important.During the various scenarios,there are different requirements of adsorption and desorption of protein.For example,in the colonization of tissues and cells,and also during the separation and enrichment of protein,the adsorption of protein is necessary,whereas protein repellent interfaces are required in some other biotechnological and biomedical materials such as biosensor devices,blood containing materials like as artificial vessels,and artificial hearts.Therefore,it is highly desired some interfaces which could control the adsorption and desorption of protein as per required conditions,which might be realized by the surfaces with stimuli-responsive ability and protein repellent property.In this thesis,we have developed a system for preciously control the adsorption of protein by using poly(2-methyl-2-oxazoline)(PMOXA)and poly(4-vinyl pyridine)(P4VP)as protein-repellent polymer brush and as stimuli-responsive polymer brush respectively.We have divided the whole work into two parts.(1)poly(4-vinyl pyridine)-block-poly(glycidyl methacrylate)(P4VP-b-PGMA)and poly[(2-methyl-2-oxazoline)-random-glycidyl methacrylate](PMOXA-r-GMA)were synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization of 4-vinyl pyridine(4VP)and cationic ring opening polymerization(CROP)of 2-methyl-2-oxazoline(MOXA)followed by their block and random copolymerization with glycidyl methacrylate(GMA),respectively.Subsequently,poly(2-methyl-2-oxazoline)/poly(4-vinyl pyridine)(PMOXA/P4VP)based binary polymer brushes on silicon/glass substrate were fabricated using spin coating of the mixture of PMOXA-r-GMA and P4VP-b-PGMA copolymer solution followed by annealing process at 110?.Afterwards,these polymer brushes were characterized by variable angle spectroscopic ellipsometry(VASE),water contact angle(WCA),atomic force microscopy(AFM),and X-ray photoelectron spectroscopy(XPS)techniques.The results showed that the surface composition on the substrate surface could be adjusted by tuning the composition of the mixture of polymer solution used for the preparation of mixed brushes.Moreover,it also showed the swelling and de-swelling of mixed polymer brushes in a systematic way between two specific points during varying the pH of the surrounding medium from 2 to 10.Finally,the tunable behavior of PMOXA/P4VP based mixed brushes against bovine serum albumin(BSA)adsorption/desorption was examined by using ellipsometry measurements and fluorescein isothiocyanate-labelled BSA(FITC-BSA)assay.The results indicated that by changing the pH value from 2 to 10,the PMOXA/P4VP based mixed brushes could adsorb and desorb protein from very low to high amount depending upon the composition of PMOXA-r-GMA and P4VP-b-PGMA in preparing solution used for the PMOXA/P4VP based coatings,and?89%of the adsorbed protein could be desorbed under the selected conditions.(2)PMOXA/P4VP based coating were prepared by using a comb polymer of PMOXA with fixed chain length and block copolymer of P4VP with varying the chain lengths through annealing mechanism.The effect of variation of chain length of P4VP on the switchable properties of mixed polymer brushes of PMOXA/P4VP was investigated through WCA and ellipsometry measurements upon pH and ionic strength(?)trigger.The results indicated that change in the water contact angle(?WCA)and thickness were found to be maximum when the chain length of P4VP was three times that of PMOXA while turning the environmental condition from pH 3,with low ionic strength(I=10-3 M)to pH 9 with high ionic strength(I=10-1 M).Finally,we bring more insight into the rational design of such smart thin film by unraveling the effect of ionic strength(?)and variation of chain length of P4VP on the adsorption/desorption of protein using the quartz crystal microbalance with dissipation monitoring(QCM-D),ellipsometry measurements and fluorescein isothiocyanate-labelled BSA(FITC-BSA)assay.The results showed that low ionic strength(I=10-3 M)at pH 3,cause to increase the adsorption of BSA,and was also enhanced by increasing the chain length of P4VP in PMOX/P4VP based coatings.Subsequently,the adsorbed protein was then efficiently desorbed by changing the conditions to pH 9,I=10-1 M,as well as the maximum desorption percentage(>92%)could be obtained at these optimized conditions in PMOXA/P4VP based polymer coatings.