A label-free fiber-optic Turbidity Affinity Sensor (TAS) for continuous glucose monitoring.

In this paper, we describe the concept of a novel implantable fiber-optic Turbidity Affinity Sensor (TAS) and report on the findings of its in-vitro performance for continuous glucose monitoring. The sensing mechanism of the TAS is based on glucose-specific changes in light scattering (turbidity) of a hydrogel suspension consisting of small particles made of crosslinked dextran (Sephadex G100), and a glucose- and mannose-specific binding protein - Concanavalin A (ConA). The binding of ConA to Sephadex particles results in a significant turbidity increase that is much greater than the turbidity contribution by the individual components.

Acute in vivo performance evaluation of the fluorescence affinity sensor in the intravascular and interstitial space in Swine.

Objective: We assessed and compared the performance levels of a fiber-coupled fluorescence affinity sensor (FAS) for glucose detection in the intradermal tissue and intravascular bed during glucose clamping and insulin administration in a large animal model.

Research Design And Methods: The FAS (BioTex Inc., Houston, TX) was implanted in interstitial tissue and in the intravenous space in nondiabetic, anesthetized pigs over 6-7 h.

A human pilot study of the fluorescence affinity sensor for continuous glucose monitoring in diabetes.

Objective: We report results of a pilot clinical study of a subcutaneous fluorescence affinity sensor (FAS) for continuous glucose monitoring conducted in people with type 1 and type 2 diabetes. The device was assessed based on performance, safety, and comfort level under acute conditions (4 h).

Research Design And Methods: A second-generation FAS (BioTex Inc.

Preclinical in vivo study of a fluorescence affinity sensor for short-term continuous glucose monitoring in a small and large animal model.

Background: The performance of a fiber-coupled fluorescence affinity sensor (FAS) was studied in vivo in small and large animal models, in order to assess its feasibility and safety for short-term glucose monitoring in humans.

Methods: Determination of interstitial glucose concentrations in skin tissue of hairless rats and small pigs was facilitated by measuring the fluorescence response of the implanted FAS over several hours and multiple days. Blood sugar changes in animals were induced by injections of insulin and dextrose.

Affinity-based turbidity sensor for glucose monitoring by optical coherence tomography: toward the development of an implantable sensor.

We investigated the feasibility of constructing an implantable optical-based sensor for seminoninvasive continuous monitoring of analytes. In this novel sensor, analyte concentration-dependent changes induced in the degree of optical turbidity of the sensing element can be accurately monitored by optical coherence tomography (OCT), an interferometric technique. To demonstrate proof-of-concept, we engineered a sensor for monitoring glucose concentration that enabled us to quantitatively monitor the glucose-specific changes induced in bulk scattering (turbidity) of the sensor.

Fiber-coupled fluorescence affinity sensor for 3-day in vivo glucose sensing.

Background: To evaluate the feasibility of an implantable fiber-coupled fluorescence affinity sensor (FAS) for glucose monitoring in humans, we studied the acute and chronic in vivo performance in hairless rats and pigs.

Methods: The implantable fiber-coupled FAS was constructed by filling a dialysis chamber made of a regenerated cellulose membrane mounted to the distal tip of an optical fiber with fluorescent chemistry based on concanavalin A. Blood sugar changes in animals were induced by injections of insulin and dextrose.

In vivo performance evaluation of a transdermal near- infrared fluorescence resonance energy transfer affinity sensor for continuous glucose monitoring.

The in vivo performance of a transdermal near-infrared fluorescence resonance energy transfer (FRET) affinity sensor was investigated in hairless rats, in order to validate its feasibility for glucose monitoring in humans. The sensor itself consists of a small hollow fiber implanted in dermal skin tissue, containing glucose-sensitive assay chemistry composed of agarose-immobilized Concanavalin A (ConA) and free dextran. The glucose-dependent fluorescence change is based on FRET between near-infrared-compatible donor and quencher dyes that are chemically linked to dextran and ConA, respectively.

Concanavalin A for in vivo glucose sensing: a biotoxicity review.

Over the last two decades there as has been surging scientific interest in employing the glucose- and mannose-specific lectin Concanavalin A (ConA) in affinity biosensors for in vivo glucose monitoring in diabetics. Numerous research groups have successfully shown in in vitro and in vivo studies that ConA-based affinity sensors can monitor glucose very accurately and reproducibly over many months, making ConA-based sensors an extremely interesting prospect for long-term implantation in humans. Despite this progress, there remains concern over the safety of ConA, which has widely been reported as a toxin in the literature.