Glucose Sensors Based on Microcapsules Containing an Orange/Red Competitive Binding Resonance Energy Transfer Assay

Abstract

Fluorescent sensing systems offer the potential for noninvasive monitoring with implantable devices, but they require carrier technologies that provide suitable immobilization, accessibility, and biocompatibility while maintaining adequate response characteristics. A recent development towards this goal is a highly specific and sensitive competitive binding assay for glucose using apo-glucose oxidase (apo-GOx) as the recognition element and dextran as the competing ligand; this has been demonstrated as a glucose sensor system by encapsulating the competitive binding assay in semipermeable microcapsule carriers. This paper describes the extension of this sensor design to longer wavelengths in an attempt to increase the applicability to in vivo monitoring. The glucose sensitivity of the tetramethylrhodamine isothiocyanate-dextran (TD) and cyanine Cy5-apo-GOx (CAG) complexes showed five to 10 times greater specificity for beta-D-glucose over other sugars. Microcapsules loaded with TD/CAG complexes exhibited a linear, totally reversible response in the range of 0-720 mg/dL, with a sensitivity (percent change in intensity ratio) of 0.06%/(mg/dL). The decrease in sensitivity observed with the use of longer-wavelength dyes is most likely to be compensated with the deeper penetration of light and reduced tissue scattering. These findings imply that the encapsulation of sensing assay elements in microcapsules is a simple and translatable method for the fabrication of stable biosensors, and optimization of resonance energy transfer pairs and assay component preparation will further improve the response to approach clinically relevant performance.

Dissolved core alginate microspheres as “smart-tattoo” glucose sensors

“…Therefore, recently alternative receptors like apo-glucose oxidase (apo-GOx) [24]–[26] have been used in “smart tattoo” formats; for example, several generations of microcapsule-based glucose biosensors employing fluorescence resonance energy transfer have been reported [3], [8], [10], [12], [13], [24], [27]–[29]. …”

Physical immobilization of laccase on an electrode by means of poly(ethyleneimine) microcapsules

“…[9]. Microencapsulation can be used to immobilize enzymes on solid supports with the objective of developing bioreactors and biosensors [10][11][12]. Few reports can be found on the use of microencapsulation to immobilize enzymes on the surface of electrodes [13][14][15][16].…”

Multilayer nanoencapsulation: A nanomedicine technology for diabetes research and management

“…Microvesicles created by LBL encapsulation and containing fluorescence-based glucose sensors have been described by our own group [2,10], as well as McShane et al [11][12][13][14][15]. In general, hollow-vesicle sensors can be formed by LBL deposition around a removable template such as calcium carbonate which can then dissolved (e.g.…”

“…In competitive systems, there is a change in fluorescence resonance energy transfer (FRET) when glucose binds to a fluorescent-labelled receptor such as tetramethyl rhodamine isothiocyanate labelled concanavalin A (FRET acceptor), in competition with a fluorescent glucose analogue such as fluorescein isothiocyanate-labelled dextran (FRET donor) [12]. Other competitive systems use apo glucose oxidase (glucose oxidase with the prosthetic group removed) as the glucose receptor, labelled with a variety of acceptors, together with dextran labelled with one of several donors [13,14]. Entrapped glucose oxidase may also be used as a sensor with detection of oxygen consumption via a co-entrapped oxygen-sensitive dye Ru(dpp) [18].…”