Location of Thesis Examination

Room 434 Thompson Engineering Building

Degree

Master of Engineering Science

Program

Chemical and Biochemical Engineering

Supervisor

Jin Zhang

Abstract

Hydrogels can be used in contact lens, wound dressing, drug delivery and tissue scaffolds due to their good biocompatibility. However, the poor mechanical properties and non-specific protein adsorption of hydrogels limit their applications. The adverse effects of protein adsorption in hydrogels include biofouling, inflammation, or even body rejection. In this project, two different hydrogel materials, co-polymer 2-hydroxyethyl methacrylate with a low amount of 2-aminoethyl methacrylate, p(HEMA-co-AEMA) and silicone hydrogel were fabricated by photo-polymerization; the former has hydrophilic surface and the latter is hydrophobic. The silica (SiO2) nanoparticle-loaded hydrogels have been developed by using in situ polymerization. The dispersion of silica nanoparticles in silicone hydrogels is quite homogenous. The Young’s modulus of silicone hydrogel-based nanocomposites is improved slightly with the comparison of that of silicone hydrogel. The bovine serum albumin (BSA) adsorption of hydrogels and their nanocomposites was examined by protein assay. It is found that silicone hydrogel and its nanocomposites prefer to adsorb more BSA than p(HEMA-co-AEMA) and its nanocomposites do. Moreover, silica nanoparticles can reduce the protein adsorption of silicone hydrogel. The cytotoxicity of the hydrogels and hydrogel-based nanocomposites has been studied as well.

As the protein adsorption is strongly related to the surface feature of hydrogels, such as electric state, hydrophobicity and steric structure, one of efficient strategies to minimize the protein adsorption is the surface coating with a thin film of protein non-sticking materials. Currently, several surface coating technologies, such as dip coating and spin coating can be used for this purpose. However, the specific surface property requirement in these coating processes limits their applications in biomedical device. The Matrix assisted pulsed laser evaporation (MAPLE) is a new process for organic molecule deposition. This physical vapor deposition is independent on the surface property of target and substrates. It has potential applications in depositing almost every kind of organic molecule. In this project, a solid-state pulsed laser with wavelength at 532nm was used in MAPLE system. The deposited polyethylene glycol (PEG) films as a function of irradiation time have been investigated by Fourier transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM). The results indicate PEG can be successfully deposited through MAPLE system. The thickness of PEG film increases with increasing irradiation time. Finally, the protein adsorptions before and after PEG deposition using MAPLE have been investigated. It is found that such deposition improved the protein resistance of silicone gels dramatically.