A self referencing platinum nanoparticle decorated enzyme-based microbiosensor for real time measurement of physiological glucose transport

Abstract

Glucose is the central molecule in many biochemical pathways, and numerous approaches have been developed for fabricating micro biosensors designed to measure glucose concentration in/near cells and/or tissues. An inherent problem for microsensors used in physiological studies is a low signal-to-noise ratio, which is further complicated by concentration drift due to the metabolic activity of cells. A microsensor technique designed to filter extraneous electrical noise and provide direct quantification of active membrane transport is known as self-referencing. Self-referencing involves oscillation of a single microsensor via computer-controlled stepper motors within a stable gradient formed near cells/tissues (i.e., within the concentration boundary layer). The non-invasive technique provides direct measurement of trans-membrane (or trans-tissue) analyte flux. A glucose micro biosensor was fabricated using deposition of nanomaterials (platinum black, multiwalled carbon nanotubes, Nafion) and glucose oxidase on a platinum/iridium microelectrode. The highly sensitive/selective biosensor was used in the self-referencing modality for cell/tissue physiological transport studies. Detailed analysis of signal drift/noise filtering via phase sensitive detection (including a post-measurement analytical technique) are provided. Using this highly sensitive technique, physiological glucose uptake is demonstrated in a wide range of metabolic and pharmacological studies. Use of this technique is demonstrated for cancer cell physiology, bioenergetics, diabetes, and microbial biofilm physiology. This robust and versatile biosensor technique will provide much insight into biological transport in biomedical, environmental, and agricultural research applications.

Mouse and human islets survive and function after coating by biosilicification

“…This result could be due to reduced diffusivity of oxygen through the layer; however, the alternative conclusion is that the magnitude of the flux is simply decreased by the experimental artifact of an increased distance between the optrode and the islet. Flux is calculated from the concentration gradient, which theoretically and experimentally decreases with distance from the source or sink (30,32), in this case the islet surface. The coating imposes at least one to a few micrometers distance between the islet and the surface of the coating and therefore the islet surface and the optrode.…”

Surface Modification Approaches for Electrochemical Biosensors

“…Two most commonly used nanomaterials are carbon nanotubes and metal nanomaterials (McLamore et al, 2010a;McLamore et al, 2010b;McLamore et al, 2011;Shi et al, 2010). Ever since Iijima reported the synthesis method for CNT in 1991 (Iijima 1991) , this allotrope of carbon has demonstrated versatile applications in biomedical imaging (Choi et al, 2007b), chemical batteries , and biosensing (McLamore et al, 2010a;McLamore et al, 2010b;McLamore et al, 2011;Shi et al, 2010 ). CNTs have two types: single-walled CNT (SWNT) and multi-walled CNT (MWNT).…”

“…The value of the potential is determined by the type of electrode used, and the type of the electroactive intermediate produced in step 1. In this particular example, for measuring H 2 O 2 with a Pt electrode, the potential used is usually +500 mV-+800 mV (McLamore et al, 2010b;McLamore et al, 2011;Shi et al, 2010). The main purpose of this step is to measure the concentration of H 2 O 2 by measuring current.…”

“…Both SWNTs and MWNTs (McLamore et al, 2010a;McLamore et al, 2010b;McLamore et al, 2011;Shi et al, 2010 ) have been widely used in biosensing . CNTs have been demonstrated to possess the ability to facilitate the electron transfer process during electroreduction and electrooxidation of electroactive species, such as NADH and hydrogen peroxide (Hrapovic et al, 2004;, and the electron transfer process during enzyme-substrate interaction, even when the enzyme redox center is deeply embedded (Gooding et al, 2003).…”

“…Enzymes are usually immobilized on the electrode by polymer encapsulation or covalent linking (McLamore et al, 2010b;McLamore et al, 2011;Rickus et al, 2002;Shi et al, 2010). During biosensor operation, when analyte solution diffuses into the enzyme layer, a series of biochemical and electrochemical reactions will take place.…”