Title

Surface modification for biomedical applications using multi-component polymers

Date of Completion

January 2001

Keywords

Chemistry, Polymer

Degree

Ph.D.

Abstract

The surface properties of biomedical implants and biomaterials have direct influence on how proteins, cells, and the organism respond to the material. Surface modification techniques are employed to either minimize bio-interaction or control bio-interaction or both. Surfaces that minimize bio-interaction, or stealth surfaces, generally consist of low-energy materials or highly hydrophilic hydrogels. In the studies discussed in this dissertation, both type surfaces have been created; perfluorinated surfaces have been delivered with surface-active polycaprolactones of two different architectures, and hydrogel coatings for an implantable sensor have been developed. Surfaces that induce desired bio-interaction are created by immobilization of biologically recognized molecules. In these studies, a cell-adhesive RGD-containing molecule was immobilized on a hydrogel surface. ^ Various molecular weights of polycaprolactone (PCL) with surface-active end groups were synthesized by initiating the ring-opening polymerization of ϵ-caprolactone with a perfluorinated alcohol and a perfluorinated acid. These polymers were characterized by elemental analysis, FTIR, NMR, DSC, TGA, and GPC. The surfaces of the neat end-functionalized PCLs (PCL-F) were characterized with contact angle and X-ray Photoelectron Spectroscopy (XPS). Blends of PCL-F with commercially available PCL were also characterized with contact angle and XPS. Microbial and hydrolytic degradation of these modified surfaces were studied. Also, a self-consistent mean field lattice fluid model was used to model these systems. ^ Comb-shaped copolymers of a fluorinated acrylate and a PCL-macromonomer were also synthesized. The addition of a small amount of this copolymer created a highly fluorinated surface on PCL, as seen by contact angle and XPS, and on other polymers that are miscible with PCL. The topography of these surfaces was examined using AFM. ^ Implantable biosensors lose function after a relatively short time in vivo due, in part, to fibrosis which stems from inflammation and protein adsorption. The approach of this study was to coat an existing sensor with hydrogel that is permeable to glucose and resistant to plasma protein adsorption. Hydrogels of different comonomer compositions were synthesized and characterized. Glucose permeability was verified, and plasma protein adsorption was studied. Also, a cell-adhesive ligand, YRGDS, was tethered to a hydrogel surface in order to encourage cell growth around the sensor. ^