Abstract
Limited training, high cost, and low equipment mobility leads to inaccuracies in decision making and is concerning with serious ocular injuries such as suspected ruptured globe or post-operative infections. Here, we present a novel point-of-service (POS) quantitative ascorbic acid (AA) assay with use of the OcuCheck Biosensor. The present work describes the development and clinical testing of the paper-based biosensor that measures the changes in electrical resistance of the enzyme-plated interdigitated electrodes to quantify the level of AA present in ocular fluid. We have demonstrated the proof-of-concept of the biosensor testing 16 clinical samples collected from aqueous humor of patients undergoing therapeutic anterior chamber paracentesis. Comparing with gold standard colorimetric assay for AA concentration, OcuCheck showed accuracy of >80%, sensitivity of >88% and specificity of >71%. At present, there are no FDA-approved POS tests that can directly measures AA concentration levels in ocular fluid. We envisage that the device can be realized as a handheld, battery powered instrument that will have high impact on glaucoma care and point-of-care diagnostics of penetrating ocular globe injuries.
Highlights
Aqueous humor has an average ascorbic acid (AA) concentration of 1049 ± 433 micromol/L2–4 whereas the ocular tear film only has an average AA concentration of 23 + 9.6 micromol/L5. With this fundamental difference in concentration and the knowledge that aqueous humor is continuously produced within the anterior chamber, we hypothesize that when the integrity of the anterior globe is disturbed from a full-thickness laceration, the higher concentrations of AA from within the continuously flowing aqueous humor will be released into the tear film causing a rise in the amount of AA in the tear film that can be quantified
The unique design of the OcuCheck multilayered test strip utilizes the selective properties of the enzyme ascorbate oxidase (AO) which is placed on graphene platelets and an amphiphilic diblock-copolymer, Poly(styrene)-block-poly(acrylic acid) (PS-b-PAA)
One of the health care areas that can be improved by technology is in the diagnosis of eye disease by primary care physicians
Summary
The tear film AA concentration can be measured by our TM novel, point-of-service device called the OcuCheck Biosensor. The resistance-based measurement provided by the OcuCheck can be performed in the clinical setting with an immediate result without having to send the samples to a laboratory for further sampling or analysis, as competing assays require. This feature of the OcuCheck device has proven to be a vital feature to enable clinical use for the device due to the fact that AA rapidly degrades after collection[21]. The OcuCheck provided accurate AA concentration within 5 minutes using 2 μ L of sample, suggesting laboratory quality data can be realized with this technique of using a battery-powered, handheld unit with disposable biosensor strips
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