Functional coatings based on denaturation-adsorption of proteins (original) (raw)
GOLI, KIRAN KUMAR. Functional Coatings Based on Denaturation and Adsorption of Proteins. (Under the direction of Jan Genzer and Orlando Rojas.) We have developed a novel method for the modification and functionalization of hydrophobic polymeric surfaces. This method offers a simple and versatile platform that is alternative to the commonly used flame, corona, plasma and other types of treatments. Specifically, denatured protein molecules were physisorbed on hydrophobic surfaces including flat solid surfaces modified with self-assembled n-octadecyltrichlorosilane (ODTS) hydrophobic layers and polypropylene (PP) materials through nonspecific interactions followed by cross-linking the adsorbed proteins forming a stable coating. Protein denaturation and properties of adsorbed protein layers were characterized by using analytical techniques including circular dichroism, ellipsometry, contact angle, and Fourier transform infrared spectroscopy in the attenuated total reflection mode. The amount of protein adsorbed on the surface was adjusted by the means of protein denaturation (chemical or thermal), varying pH and protein concentration in the deposition solution, and adsorption time. The inherent hydrophilic amino acid functionalities of the protein layer including hydroxyl and amino groups endowed surfaces with improved wettabilities. The protein primers also provided opportunity to create/generate new functional coatings for selected applications, which involve growing polymeric grafts and attaching silver nanoparticles. The hydroxyl-and amino-functional groups present on protein-modified surfaces served as reactive/anchoring sites for the attachment of polymerization initiators from which poly (2-hydroxyethyl methacrylate) (PHEMA) polymer grafts are grown directly through "grafting from" via atom-transfer radical polymerization (ATRP). Grafted polymer layers enriched surfaces with functional hydroxyl groups in HEMA units, which served as attachment points for small molecule fluorinated modifiers of different sizes. Anti-fouling properties of the resultant amphiphilic coatings on PP surfaces were tested against the adsorption of fluorescein isothiocyanate-labeled bovine serum albumin as a model fouling protein. Our work established that these amphiphilic coatings suppressed significantly the adsorption of proteins as compared to PP surfaces or PP surfaces coated with parent PHEMA brushes. Modulation of the surface composition of the topmost layer of the amphiphilic coating and its anti-fouling capability is evident by varying the type of the fluorinated unit grafted to PHEMA. We have also generated coatings with antibacterial characteristics by attaching with silver nanoparticles to PP fiber surfaces via electrostatic interactions. Specifically, lysozyme protein layer assembled on PP surfaces created numerous cationic charged functional groups depending upon the solution pH conditions. Citrate capped silver nanoparticles were subsequently deposited through ionic interactions on to the protein-modified surfaces. Characterization of the resulting functional surfaces with UV-vis spectroscopy and scanning Rojas for giving me the opportunity to be their student. I have worked with Dr. Genzer for four years; he has been an excellent mentor and it has been a great learning experience. His valuable guidance, support and encouragement throughout my research helped to improve myself professionally and contribute to the scientific community. This dissertation work would have never been accomplished without the valuable guidance and support of Professor Rojas. I thank Professors Anatoli Melechko, Behnam Pourdeyhimi and Tzy-Jiun Luo for serving on my dissertation committee and also for their support and guidance that made my work a success (in addition to being extremely helpful and supportive). Also, I would like to thank
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