The role of H2O2 outer diffusion on the performance of implantable glucose sensors

Abstract

The performance of an implantable glucose sensor is strongly dependent on the ability of their outer membrane to govern the diffusion of the various participating species. In this contribution, using a series of layer by layer (LBL) assembled outer membranes, the role of outwards of H 2 O 2 diffusion through the outer membrane of glucose sensors has been correlated to sensor sensitivity. Glucose sensors with highly permeable Humic Acids/Ferric cations (HAs/Fe 3+ ) outer membranes displayed a combination of lower sensitivities and better linearities when compared with sensors coated with lesser permeable outer membranes (namely HAs/poly (diallyldimethylammonium chloride) (PDDA) and poly (styrene sulfonate) (PSS)/PDDA). On the basis of a comprehensive evaluation of the oxygen dependence of through these membranes, it these sensors in conjunction with the permeability of H 2 O 2 was concluded that the outer diffusion of H 2 O 2 is crucial to attain optimized sensor performance. This finding has important implications to the design of various bio-sensing elements employing perm-selective membranes.

Enhanced Glucose Sensor Linearity Using Poly(Vinyl Alcohol) Hydrogels

“…The fabrication of working electrodes was achieved as described previously. 21 The LBL assembly of semipermeable membranes was performed as described elsewhere. 21 In brief, this was achieved by dipping the GO x -covered working electrodes alternately in solutions of HA or PSS and For the preparation of PVA solutions, 10% (w/v) aqueous solutions of 99% hydrolyzed PVA were preheated to ca.…”

“…For determination of apparent Michaelis-Menten constants for glucose (K app m,glu ) and oxygen (K app m,O2 ), along with the linear range sensitivity (LRS) of the sensor, analysis was performed as described elsewhere, 21 using Equation (4):…”

“…Figure 2. The addition of five bilayers of LBL membranes (device A 21 The incorporation of three FT-cycled PVA layers on top of the LBL membranes (devices A 5 P 3 , B 5 P 3 , and C 5 P 3 ) resulted in a 40 to 75% increase in K app m,glu and a 50% decrease in sensitivity. The trends in LRS and K app m,glu for devices A 5 P 3 , B 5 P 3 , and C 5 P 3 are similar to devices A 5 , B 5 , and C 5 , wherein device A 5 P 3 displayed a threefold higher K app m,glu and an order of magnitude lower LRS than devices B 5 P 3 and C 5 P 3 .…”

“…19 In order to reduce membrane thickness and fine-tune permeability, we have employed layer-by-layer (LBL) assemblies based on charged polymers and/or multivalent cations (i.e., Fe 3+ ). 7,11,12,21 In particular, the combination of five humic acid (HA)/Fe 3+ bilayers has been shown to enhance linearity while at the same time reducing sensor response time through the facile outer diffusion of H 2 O 2 . 21 In a separate development, our group has shown that poly(vinyl alcohol) (PVA) hydrogels containing dexamethasone-loaded poly(lactic-co-glycolic acid) microspheres are capable of suppressing inflammation in excess of 1 month.…”

“…7,11,12,21 In particular, the combination of five humic acid (HA)/Fe 3+ bilayers has been shown to enhance linearity while at the same time reducing sensor response time through the facile outer diffusion of H 2 O 2 . 21 In a separate development, our group has shown that poly(vinyl alcohol) (PVA) hydrogels containing dexamethasone-loaded poly(lactic-co-glycolic acid) microspheres are capable of suppressing inflammation in excess of 1 month. 11,[22][23][24][25][26] Unlike other systems that use reactive cross-linking agents, 19,20,27 both LBL and PVA hydrogels rely on physical cross-linking based on ionic interactions 7,11,12,21,28 and freeze-thaw (FT)-induced phase separation, 22,29,30 respectively, which eliminates the possibility of side reactions with the underlying enzyme layer.…”