Abstract
Glucose concentration is an important parameter in biomedicine since glucose is involved in many metabolic pathways in organisms. Many methods for glucose detection have been developed for use in various applications, particularly in the field of healthcare in diabetics. In this study, ratiometric fluorescent glucose-sensing membranes were fabricated based on the oxygen levels consumed in the glucose oxidation reaction under the catalysis of glucose oxidase (GOD). The oxygen concentration was measured through the fluorescence quenching effect of an oxygen-sensitive fluorescent dye like platinum meso-tetra (pentafluorophenyl) porphyrin (PtP) by oxygen molecules. Coumarin 6 (C6) was used as a reference dye in the ratiometric fluorescence measurements. The glucose-sensing membrane consisted of two layers: The first layer was the oxygen-sensing membrane containing polystyrene particles (PS) doped with PtP and C6 (e.g., PS@C6^PtP) in a sol–gel matrix of aminopropyltrimethoxysilane and glycidoxypropyltrimethoxysilane (GA). The second layer was made by immobilizing GOD onto one of three supporting polymers over the first layer. These glucose-sensing membranes were characterized in terms of their response, reversibility, interferences, and stability. They showed a wide detection range to glucose concentration in the range of 0.1 to 10 mM, but high sensitivity with a linear detection range of 0.1 to 2 mM glucose. This stable and sensitive ratiometric fluorescent glucose biosensor provides a reliable way to determine low glucose concentrations in blood serum by measuring tear glucose.
Highlights
The determination of glucose concentration is of great interest in healthcare for diabetics, who account for about 5% of the world’s population [1]
Glucose oxidase (GOD, 26,820 unit(U)/g-solid, from Aspergillus niger), coumarin 6 (C6), 6 (C6), 3-aminopropyltrimethoxysilane (APTMS), 3-Glycidoxypropyltrimethoxysilane (GPTMS), 3-aminopropyltrimethoxysilane (APTMS), 3-Glycidoxypropyltrimethoxysilane (GPTMS), bovine bovine serum albumin (BSA), iron chloride, poly(vinyl pyrrolidone) (PVP, M.W. ≈ 55,000), serum albumin (BSA), iron chloride, poly(vinyl pyrrolidone) (PVP, M.W. ≈ 55,000), styrene, 2,2’styrene, 2,2’-azobisisobutyronitrile (AIBN), sodium dodecyl sulfate (SDS), L-ascorbic acid, uric acid, azobisisobutyronitrile (AIBN), sodium dodecyl sulfate (SDS), L-ascorbic acid, uric acid, and acetaminophen were purchased from Sigma-Aldrich Chemical Co. (Seoul, Korea)
In the presence of oxygen, when a fluorescence molecule is in the excited state and oxygen is in the ground state, a collision occurs between two molecules, which leads to an energy transfer between them, resulting in decreases in the fluorescence intensity and the lifetime of the fluorescence molecule as well as a transformation of oxygen from its ground state to its excited state
Summary
The determination of glucose concentration is of great interest in healthcare for diabetics, who account for about 5% of the world’s population [1]. The disease stems from insulin deficiency and metabolic disorders caused by hyperglycemia, which is characterized by blood sugar levels above or below the normal range of 80–120 mg/dL (4.4–6.6 mM) [2]. Many glucose sensors have been developed using several approaches, many of which have involved electrochemical and optical methods. Glucose biosensors using electrochemical and optical analysis technology occupy about 85%. Of the total biosensor market [2]. Each technology has pros and cons and needs to be adjusted to achieve more accurate results, reliable monitoring, and safety. Measurements by glucose biosensors can be separated to noninvasive and invasive methods; non-invasive methods are preferred due to Biosensors 2020, 10, 86; doi:10.3390/bios10080086 www.mdpi.com/journal/biosensors
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