In Situ Assembled Mass-Transport Controlling Micromembranes and Their Application in Implanted Amperometric Glucose Sensors

Abstract

Micromembranes were assembled by sequentially chemisorbing polyanions and polycations on miniature (5 x 10(-4) cm2) enzyme electrodes. The sequential chemisorption process allowed the simultaneous tailoring of their sensitivity, dynamic range, drift, and selectivity. When assembled on tips of 250-microm-diameter gold wires coated with redox polymer-"wired" glucose oxidase, they allowed tailoring of the glucose electrodes for > 2 nA/mM sensitivity; 0-30 mM dynamic range; drift of < or =5% per 24 h at 37 degrees C at 15 mM glucose concentration; and < or =5% current increment by the combination of 0.1 mM ascorbate, 0.2 mM acetaminophen, and 0.5 mM urate. The membranes also retained transition metal ions that bound to and damaged the redox polymer "wiring" the enzyme. The electrodes were tested in the jugular veins and in the intrascapular subcutaneous region of anaesthetized and heparinized nondiabetic Sprague-Dawley rats, in which rapid changes of glycemia were forced by intravenous injections of glucose and insulin. After one-point in vivo calibration of the electrodes, all of the 152 data points were clinically accurate when it was assumed that after insulin injection the glycemia in the subcutaneous fluid lags by 9 min behind that of blood withdrawn from the insulin-injected vein.

Microdialysis Sampling Extraction Efficiency of 2-Deoxyglucose: Role of Macrophages in Vitro and in Vivo

“…In each experimental animal, one probe was implanted for a set period of time (3,5, and 7 days) on one side of the dorsal subcutis while another probe was acutely implanted as a control on the opposite side on the day of sample collection. The 3-day implantation experiment has been performed using three animals; the 5-day and 7-day implantation experiments were each performed using two animals.…”

Solid-contact potentiometric polymer membrane microelectrodes for the detection of silver ions at the femtomole level

“…The calibration and selectivity measurements were performed in a 100 ml polypropylene beaker pretreated overnight in 0.1 M HNO 3 . Only the very tips of the electrodes were immersed into the sample solution.…”

“…Miniaturized sensors have been successfully explored in chemical analysis, including in vivo applications as well as online monitoring bioactive substances [1][2][3][4]. Also due to their compact size, high sensitivity and comparably low cost, microsensors are an attractive system for small volume applications to detect ultra-small amounts of compounds.…”

Mass Transfer in Amperometric Biosensors Based on Nanocomposite Thin Films of Redox Polymers and Oxidoreductases

“…Heller and colleagues constructed micrometer scale polyelectrolyte thin films that limited glucose mass transfer in implanted sensors. [31] Others have observed that polyelectrolyte nanocomposite thin films are highly compact, have a nanoporous structure and can limit the diffusion of small molecules such as ferricyanide. [15,16,22] Given that the nanocomposite films described here do undergo significant structural changes upon oxidation and reduction, these films are likely very compact and may posses nanoporosity as seen in other polyelectrolyte thin films.…”