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

• Published in: Biosensors & bioelectronics 2014-11, Vol.61, p.280-284
• Main Authors: Dutt-Ballerstadt, Ralph, Evans, Colton, Pillai, Arun P., Gowda, Ashok
• Format: Article
• Language: English
• Subjects: Affinity; Affinity sensor; Binding; Biological and medical sciences; Biosensing Techniques - instrumentation; Biotechnology; Blood Glucose - analysis; Concanavalin A; Concanavalin A - chemistry; Continuous fibers; Continuous glucose monitoring; Dextran; Dextrans - chemistry; Equipment Design; Fiber Optic Technology - instrumentation; Fiber optics; Fundamental and applied biological sciences. Psychology; Glucose; Glucose - analysis; Humans; Hydrogel, Polyethylene Glycol Dimethacrylate - chemistry; Light; Limit of Detection; Monitoring; Optical fibers; Prostheses and Implants; Scattering, Radiation; Turbidity
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2014.05.034

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. The turbidity of the TAS was measured by determining the intensity of light passing through the suspension enclosed within a small semi-permeable hollow fiber (OD: 220μm, membrane thickness: 20μm, molecular weight cut-off: 10kDa) using fiber optics. The intensity of measured light of the TAS was proportional to the glucose concentration over the concentration range from 50mg/dL to 400mg/dL in PBS and whole blood at 37°C (R>0.96). The response time was approximately 4min. The stability of the glucose response of the TAS decreased only slightly (by 20%) over an 8-day study period at 37°C. In conclusion, this study demonstrated proof-of-concept of the TAS for interstitial glucose monitoring. Due to the large signal amplitude of the turbidity change, and the lack of need for wavelength-specific emission and excitation filters, a very small, robust and compact TAS device with an extremely short optical pathlength could be feasibly designed and implemented for in-vivo glucose monitoring in people with diabetes. •A novel label-free fiber-optic Turbidity Affinity Sensor (TAS) for continuous glucose monitoring is proposed.•The label-free TAS would minimize the complexity of hardware for optical sensing.•The results of the in-vitro performance study demonstrated proof-of-concept of TAS.•An extremely compact, miniaturized and implantable CGMS system for people with diabetes is feasible.