title: 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.
authors.affiliation: Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States.
authors.forename: Qinyi
authors.initials: Q
authors.lastname: Yan
authors.forename: Bo
authors.initials: B
authors.lastname: Peng
authors.forename: Gang
authors.initials: G
authors.lastname: Su
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Cohan
authors.forename: Terry C
authors.initials: TC
authors.lastname: Major
authors.forename: Mark E
authors.initials: ME
authors.lastname: Meyerhoff
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D001786:Blood Glucose / Q000032:analysis*; D055664:Electrochemical Techniques; D004800:Enzymes, Immobilized / Q000378:metabolism; D005947:Glucose / Q000032:analysis*; D005949:Glucose Oxidase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D007495:Iridium / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D011817:Rabbits; D012118:Resorcinols / Q000737:chemistry; D013666:Tears / Q000737:chemistry*; D014527:Uric Acid / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D004800:Enzymes, Immobilized; D012118:Resorcinols; D014527:Uric Acid; D007495:Iridium; D010984:Platinum; D006861:Hydrogen Peroxide; D005949:Glucose Oxidase; D005947:Glucose; D001205:Ascorbic Acid; C031389:resorcinol