Title

Sensitivity, linearity and reliability enhancement of implantable glucose sensors

Date of Completion

January 2009

Keywords

Chemistry, Polymer|Engineering, Biomedical

Degree

Ph.D.

Abstract

The development of glucose and other metabolic implantable biosensors is an area of intense research with application in diabetes, obesity and metabolic monitoring in general. Major obstacles to the development of implantable biosensors are their oxygen dependence, low dynamic range and sensitivity and a noted gradual loss of function over extended periods of operation. The first part of this dissertation describes the fabrication and development of miniaturized electrochemical glucose sensors, develops means of enhancing their performance in terms of oxygen independence, dynamic range (linearity) and studies their response behavior in vitro. The sensors are based on the electrochemical oxidation of enzymatically generated H 2O2 and employ layer-by-layer (LBL) assembled films/poly (vinyl alcohol) (PVA) hydrogel dual outer membranes to improve linearity and oxygen independence. The incorporation of LBL films improved the linearities by 5 fold and decreased the oxygen dependence by 3 fold. The additional PVA layer further enhanced the linearities by a further 60% and decreased oxygen dependence by 2 fold. By varying the microstructure (and hence the permeability) of the LBL assembled films, the role of outward diffusion of H2O 2 on sensor performance has been elucidated. Keeping in mind the interrelationship of glucose with lactate and oxygen, a miniaturized trianalyte sensor for simultaneous monitoring of glucose, lactate and O2 has also been developed which could potentially improve the reliability of the glucose sensors. ^ The second part of the dissertation describes the fabrication and development of organic photovoltaic devices, which potentially can be used to power the wireless chip of the implantable biosensor described above. These photovoltaics are based on ternary mixtures of C60, a polycarbonate linked TPD (N,N,N',N'-tetrakis(phenyl) benzidine)) polymer (PTPD), and a small molecular weight radical salt of a TPD derivative, in an ITO/blend/AI configuration. We demonstrated that the incorporation of the radical salt into the PTPD/C 60 mixture provided 7 times improvement, from 0.06% to 0.47% in the power conversion efficiency (ηE), a substantial value considering that it originates from a 2,500 Å thick amorphous photoactive layer. ^