Measurement of Tear Glucose Levels with Amperometric Glucose Biosensor/Capillary Tube Configuration

Abstract

An amperometric needle-type electrochemical glucose sensor intended for tear glucose measurements is described and employed in conjunction with a 0.84 mm i.d. capillary tube to collect microliter volumes of tear fluid. The sensor is based on immobilizing glucose oxidase on a 0.25 mm o.d. platinum/iridium (Pt/Ir) wire and anodically detecting the liberated hydrogen peroxide from the enzymatic reaction. Inner layers of Nafion and an electropolymerized film of 1,3-diaminobenzene/resorcinol greatly enhance the selectivity for glucose over potential interferences in tear fluid, including ascorbic acid and uric acid. Further, the new sensor is optimized to achieve very low detection limits of 1.5 ± 0.4 μM of glucose (S/N = 3) that is required to monitor glucose levels in tear fluid with a glucose sensitivity of 0.032 ± 0.02 nA/μM (n = 6). Only 4-5 μL of tear fluid in the capillary tube is required when the needle sensor is inserted into the capillary. The glucose sensor was employed to measure tear glucose levels in anesthetized rabbits over an 8 h period while also measuring the blood glucose values. A strong correlation between tear and blood glucose levels was found, suggesting that measurement of tear glucose is a potential noninvasive substitute for blood glucose measurements, and the new sensor configuration could aid in conducting further research in this direction.

Blood, sweat, and tears: developing clinically relevant protein biosensors for integrated body fluid analysis

“…One of the challenges when sampling tear fluid for a quantitative readout, is that any irritation can cause an increase in tear production leading to a reduction in biomarker concentration. 119 There are several potential solutions which have been explored such as minimally invasive capillary collection at the corner of the eye 120 to calibration with a continuous monitoring device such as an electrode embedded contact lens. 121 Many groups have turned to contact lenses ( Fig.…”

Improved thromboresistance and analytical performance of intravascular amperometric glucose sensors using optimized nitric oxide release coatings

“…Incorporating NO releasing donor molecules into a sensor's outer polymeric coatings allows it to mimic the functions of endothelial cells lining the inner walls of all blood vessels, which endogenously release NO at localized fluxes of (0.5-4.0) Â 10 À10 mol cm À2 min À1 [4]. This approach has previously been shown to reduce clot formation on the surface of intravenous glucose sensors and preserve their in vivo performance [5,6]. Herein, we extend this earlier work by further optimizing the NO release formulation and the outer glucose restriction layer used to prepare such devices to achieve more optimal linearity and in vivo performance.…”

Future of Healthcare—Sensor Data-Driven Prognosis

“…There have been reports of early success in measuring blood glucose from tear drops [9]. Google has announced their intent to build a smart diabetic sensing contact lens using the above technology.…”