PMOXA/PAA Brushes With Switchable Properties For Controlled Protein Adsorption

Controlled surface adsorption of proteins,cells,and bacteria is of major importance for various biotechnological or biomedical materials,that may need to suppress protein adsorption on their surfaces and to improve their biocompatibility.On the other hand,protein-adsorbed interfaces are crucial for cell and tissue colonization of materials surfaces and protein enrichment and separation processes.Binary polymer brushes constituted from two incompatible polymers grafted to the same substrate represent an example to address the challenges of controlled protein adsorption.In this thesis,we developed an approach to address the challenge of controlled protein adsorption using poly(2-methyl-2-oxazoline)(PMOXA)as protein-repellent brush and poly(acrylic acid)PAA as stimuli-responsive polymer brush.The work was divided into two parts:(1)Poly(2-methyl-2-oxazoline-random-glycidyl methacrylate)(PMOXA-r-GMA)and poly(acrylic acid)-block-poly(glycidyl methacrylate)(PAA-b-PGMA)copolymers were synthesized via cationic ring-opening polymerization(CROP)of 2-methyl-2-oxazoline(MOXA)and reversible addition-fragmentation chain transfer(RAFT)polymerization of acrylic acid(AA)followed by their random and block copolymerization with glycidyl methacrylate(GMA),respectively,and then characterized carefully.PMOXA/PAA based coatings were then prepared by simply spin coating the mixture of PMOXA-r-GMA and PAA-b-PGMA copolymer solutions onto silicon/glass substrates followed by annealing at 110 ?.The results demonstrated that the coating based mixed PMOXA/PAA brushes with desired surface composition could be attained by simply maintaining their percentage in the mixture of PMOXA-r-GMA and PAA-b-PGMA copolymer solutions.Finally,the switchable behavior of PMOXA/PAA based coatings toward bovine serum albumin(BSA)adsorption was investigated by fluorescein isothiocyanate-labelled BSA(FITC-BSA)assay and quartz crystal microbalance with dissipation monitoring(QCM-D),which indicated that the coating based mixed PMOXA/PAA brushes could control BSA adsorption/desorption from very low to high amount(>90%desorption)through adjusting the composition of PMOXA-r-GMA and PAA-b-PGMA solution used in preparing PMOXA/PAA based coatings upon pH and ionic strength change.Furthermore,PMOXA/PAA based coatings displayed efficient repeatability of reversible BSA adsorption/desorption cycles.(2)PMOXA-r-GMA comb polymer with determined PMOXA chain length and PAA-b-PGMA block copolymers with different PAA chain length were firstly used to prepare PMOXA/PAA based coatings by means of annealing protocol.The relationship of the switchable behavior of PMOXA/PAA based coatings with PAA content and chain length was then investigated through the change of thickness and WCA upon pH and ionic strength(I)trigger by using WCA test and ellipsometry.The results indicated that change in thickness and WCA was improved when PAA contents were increased as well as by increasing chain length of PAA in PMOXA/PAA based coatings.Finally,real-time adsorption/desorption of lysozyme(Lyso)on PMOXA/PAA based coatings was monitored using quartz crystal microbalance with dissipation monitoring(QCM-D).The results showed that the Lyso adsorption amount was increased upon increasing chain length and contents of PAA in PMOXA/PAA based coatings.The adsorbed Lyso was then efficiently desorbed by changing pH and I of medium with maximum desorption(>90%desorption percentage)observed for the suitable ratio of PMOXA and PAA while chain length of PAA was kept longer than that of PMOXA.Furthermore,the prepared coatings were found to repeatedly adsorb and desorb Lyso for four successive cycles of adsorption/desorption which confirmed the stability of prepared coatings.