Enhanced glucose sensor linearity using poly(vinyl alcohol) hydrogels.
BACKGROUND
High linearities, sensitivities, and low oxygen dependence constitute prime requisites for electrochemical glucose sensors. However, for implantable sensors the need to control tissue inflammation requires the use outer membranes that permit inward analyte diffusion while continuously releasing anti-inflammatory drugs and other tissue response-modifying (TRM) agents. We have shown previously that while outer membranes based on layer-by-layer (LBL) assembly enhance linearity, poly(vinyl alcohol)(PVA) hydrogels loaded with TRM-containing microspheres enable a significant reduction in tissue inflammation. This article discusses amperometric performance of glucose sensors coated with stacked LBL/PVA hydrogel outer membranes.


METHODS
Sensors were fabricated by immobilizing glucose oxidase enzyme on a 50-microm platinum wire followed by deposition of stacked LBL/PVA hydrogel outer membranes. The sensor response to various glucose concentrations was determined by applying 0.7 V vs an Ag/AgCl reference electrode in phosphate-buffered saline (37 degrees C). Michaelis-Menten analysis was performed to quantify sensor performance in terms of linearity (K(m,glu)(app)) and oxygen dependence (K(m,O(2))(app)/[Glucose]).


RESULTS
When overlaid onto LBL-assembled outer membranes, PVA hydrogels improved sensor linearity by 60% from 10 to 16 mM of glucose and resulted in a twofold decrease in oxygen dependence.


CONCLUSIONS
Enhancement in the performance of a PVA-coated sensor is attributed to the oxygen-storing capability of PVA hydrogel due to the formation of hydrophobic domains during its freezing and thawing employed to physical cross-link the PVA. Such membranes with the capability to release TRMs continuously while storing oxygen constitute a major improvement over current outer membrane technologies.
Nanomaterials Optoelectronics Laboratory, Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, USA.
Santhisagar
S
Vaddiraju
Hardeep
H
Singh
Diane J
DJ
Burgess
Faquir C
FC
Jain
Fotios
F
Papadimitrakopoulos
D001672:Biocompatible Materials; D015374:Biosensing Techniques; D005947:Glucose / Q000032:analysis*; D020100:Hydrogels; D015918:Infusion Pumps, Implantable; D007332:Insulin Infusion Systems; D008863:Microspheres; D011142:Polyvinyl Alcohol / Q000737:chemistry
D001672:Biocompatible Materials; D020100:Hydrogels; D011142:Polyvinyl Alcohol; D005947:Glucose