Date of Completion

11-22-2019

Embargo Period

11-19-2029

Keywords

biosensors, CGM, liquid-crystal, polyurethane, perm-selective membranes, self-assembly, glycerol biosensors, SCPNs, anti-biofouling

Major Advisor

Fotios Papadimitrakopoulos

Associate Advisor

Mu-Ping Nieh

Associate Advisor

Montgomery T. Shaw

Field of Study

Polymer Science

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

This thesis focuses on the development of long term stable implantable enzymatic electrochemical sensors with good sensitivity and stability. Perm-selective polyurethane (PU) membranes are used to balance the substrate to oxygen ratio and afford linearity in enzymatic sensor fabrication. However, the as cast PU membranes are prone to an initial swelling and subsequent densification that result in a large drift in sensor sensitivity in long-term performance. Exposing the perm-selective PU membranes to methanol (MeOH) vapors eliminates the aforementioned morphological changes by accessing a liquid-crystal ordered smectic meso-phase. This new state eliminates the sensitivity drifts and provides exceptional long-term stability of enzymatic biosensors for up to 2 months. The close zigzag packing of H12MDI hard segment alongside the formation of ordered H-bonding that stabilizes the PU morphology and provides stable diffusion characteristics for such perm-selective membranes. Furthermore, a synthesized oligomer urethane with H12MDI hard segment and short polytetramethylene oxide (PTMO) soft segment was blended with PU, creating a perm-selective membrane with higher permeability for enzymatic substrate such as glucose. The sensor sensitivity was increased by 4 times due to the spacing and voids created between PU chains in the ordered phase of perm-selective membranes formed after blending and liquid-crystal chain organization.

This thesis also focuses onto novel electrochemical-based enzymatic sensors and nanomaterials to construct such devices. A novel glycerol electrochemical sensor was designed, fabricated and characterized in both in vitro and in vivo testes. The spring shape platinum (Pt) electrode and the adenosine triphosphate (ATP), phosphocreatine, Mg2+ and creatine phosphate kinase (CPK) loaded poly(diallyldimethylammonium) chloride (PDDA) gel inside Pt electrode realized the long term glycerol detection based on enzymatic cascades. The glycerol sensor showed good sensitivity and stability in phosphate buffered saline (PBS), bovine serum albumin (BSA) and rat’s body under a specific designed pulsing detection mode. In addition, the one-to-one self-assembly of single-chain polymeric nanoparticles with proteins that can be applied to store oxygen in sensing filed is studied. The anti-biofouling properties of such copolymer hydrogel coating shows the potential of creating a zwitter-ionic surface in reducing biofouling.

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Available for download on Monday, November 19, 2029

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