Thermally Responsive Surfaces for Tissue Engineering and Apparel Applications

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Title: Thermally Responsive Surfaces for Tissue Engineering and Apparel Applications
Author: Barcio, Sarah
Advisors: Dr. Nancy Monteiro-Riviere, Committee Member
Dr. Marian McCord, Committee Chair
Dr. Mohamed Bourham, Committee Member
Abstract: Thermally responsive surfaces were created by grafting poly (N-isopropylacrylamide) (pNIPAM) onto polyester (PET) film and fabric using atmospheric pressure plasma treatment, which provided a quick, simple means of grafting that sufficiently sterilized the samples for cell culture. Grafting was achieved by a two-step process of surface activation with atmospheric pressure plasma followed by exposure of the substrate to a monomer solution in the presence of atmospheric pressure plasma. The plasma exposure time and monomer solution volume were optimized using cell culture studies. The graft was characterized by surface analysis techniques and cell culture studies. Contact angle measurements at different temperatures verified the thermally responsive nature of the graft on the PET film and fabric. Atomic force microscopy (AFM) was used to examine the surface topography and the effects of an aqueous environment on the surface. Scanning electron microscopy (SEM) was also used to examine the surface of the films and fabrics and to confirm the presence of the pNIPAM. AFM images showed the surface become significantly rougher and more variable when placed in water as the polymer chains became hydrated and a gel structure formed. The decrease in surface roughness seen with the grafted film and the SEM images confirm the graft coating the untreated film. The graft thickness on the PET film was found to be between 30 and 100 nm with AFM measurements. An acid dye test verified the presence of the graft on the filtration fabric. Cell culture studies were completed using human epidermal keratinocytes (HEKs), human lung fibroblasts (HFLs), and human hepatocellular carcinoma (Hep G2) cells to demonstrate thermally modulated cellular adhesion, growth and detachment on the films and fabrics. Viable cell sheets were successfully released from atmospheric plasma grafted pNIPAM on polyester film. Although no detachment was achieved with the grafted PET fabric, the treated fabrics could potentially be useful for tissue engineering scaffolds in bioreactors or for large-scale cell sheet engineering. Thermally responsive textiles were created using coat- and spray-grafting of pNIPAM onto woven cotton, nylon, and polyester with atmospheric pressure plasma treatment. Fourier transform infrared spectroscopy (FTIR) was used to examine the surface chemistry and confirm the presence and washfastness of the grafts produced from the two methods. Vertical wicking tests showed an increase in wettability with increasing temperature. Coat-grafted fabrics had the greatest resistance to wicking, and spray-grafted fabrics had the greatest wicking. An acid dye test also confirmed the presence of the graft showing the greatest uniformity and washfastness from the coat-grafting method. Once fully characterized, these fabrics could be used as responsive textiles for apparel applications.
Date: 2006-11-05
Degree: MS
Discipline: Biomedical Engineering

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