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

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 H2O2 diffusion through the outer membrane of glucose sensors has been correlated to sensor sensitivity. Glucose sensors with highly permeable humic acids/ferric cations (HAs/Fe3+) 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 these sensors in conjunction with the permeability of H2O2 through these membranes, it was concluded that the outer diffusion of H2O2 is crucial to attain optimized sensor performance. This finding has important implications to the design of various bio-sensing elements employing perm-selective membranes.