Date of Graduation

8-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Chemical Engineering

Advisor/Mentor

Shannon Servoss

Committee Member

Robert Beitle

Second Committee Member

Lauren Greenlee

Third Committee Member

Christa Hestekin

Fourth Committee Member

Jamie Hestekin

Fifth Committee Member

Wen Zhang

Abstract

In recent decades, membrane technology has been used commonly in biomedical area. However, membrane fouling is a widespread problem in different applications. One method to minimize fouling is through surface modification of membranes. My research explores a novel polymer to minimize nonspecific protein adsorption in biomedical applications.

It firstly focuses on grafting the electrically neutral NMEG peptoid, containing 2-methoxyethyl side chains, to polysulfone (PSU) membrane via polydopamine. Contact angle measurements indicated that the hydrophilicity of the peptoid-grafted membranes was significantly improved while the pore size and strength of the membranes remained unchanged. The modified membranes showed an improved fouling resistance when tested with bovine serum albumin, lysozyme and fibrinogen proteins. To further investigate the low fouling surfaces, peptoid length was varied length of peptoids (NMEG5, NMEG10, NMEG15 and NMEG20). The effect of peptoid length and grafting density on fouling resistance of the membranes was studied. Static adsorption experiments with bovine serum albumin revealed that there is an optimal grafting density to improve fouling resistance of peptoid modified membranes, which was dependent on the length and amount of the grafted peptoids.

To evaluate the application of modified hollow fibers in the biomedical field, a gas exchange system was designed and built. The peptoid-grafted hollow fiber membranes could preserve an excellent oxygen gas transmission compared with PSU membranes after exposure to bovine serum solution (35 mg/ml in PBS). To expand the understanding about dynamic fouling resistance of peptoid grafted surfaces, cross-flow filtration tests using bovine serum solution as the feed, was designed and built. According to the cross-flow filtration results, NMEG modified membranes showed a significant improvement in antifouling ability. Furthermore, flux recovery ratios obtained from NMEG modified membranes were much higher than unmodified membranes. The outcome of this study suggests that peptoids are a promising material for fouling-resistant membrane surface modification

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