Abstract
Fluorescence‐based sensing systems offer potential for noninvasive monitoring with implantable devices, but require carrier technologies that provide suitable immobilization, accessibility, and biocompatibility. Recent developments towards this goal include a competitive binding assay for glucose that has been encapsulated in semipermeable microcapsule carriers. This paper describes an extension of this work to increase the applicability to in vivo monitoring, wherein two significant developments are described: (1) a near‐infrared resonance energy transfer system for transducing glucose concentration, and (2) novel hybrid organic‐inorganic crosslinked microcapsules as carriers. The quenching‐based assay is a competitive binding (CB) system based on apo‐glucose oxidase (AG) as the receptor and dextran as the competitive ligand. The encapsulated quencher‐labeled dextran and near infrared donor‐labeled glucose receptor showed a stable and reversible response with tunable sensitivity of 1–5%/mM over the physiological range, making these transducers attractive for continuous monitoring for biomedical applications.
Highlights
It is well known that frequent monitoring of glucose concentrations and appropriate countermeasures can help in achieving euglycemia and minimizing secondary complications of diabetes [1,2,3,4,5]
By fitting the data collected from three experiments performed at different concentrations of AFAG, the kd for QSY 21 (QSY21)-dextran was estimated to be between 50 and 100 nM
These findings prove the efficiency of the resonance energy transfer (RET)-based quenching process due to apo-GOx:dextran association and provide insight into the binding affinity, which is useful in assay design
Summary
It is well known that frequent monitoring of glucose concentrations and appropriate countermeasures can help in achieving euglycemia and minimizing secondary complications of diabetes [1,2,3,4,5]. While several approaches for fluorescence-based glucose sensing have been developed using Concanavalin A [12, 19,20,21,22,23,24,25] and boronic acid receptors [26,27,28,29,30,31,32], their use remains complicated by concerns over toxicity, nonspecific and irreversible binding, and response ranges that do not match physiological levels. Apo-GOx is highly selective to β-D-glucose (5–10X, relative to α-Dglucose, D-mannose, and sucrose), suspensions of capsules respond in less than 1 minute to glucose titrations, and the CB assay is responsive in the clinically relevant 0–30 millimolar (∼0–600 mg/dL) range [15, 33,34,35]. GOx has been designated as “GRAS,” generally regarded as safe [36]
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