Glucose detection based on the photothermal effect of OxTMB using a thermometer

Although 3,3’,5,5’-tetramethyl benzidine dihydrochloride (TMB) has been widely used as a chromogenic agent in colorimetric analysis, other characteristics of its one-electron oxidation product (oxTMB) have seldom been explored. OxTMB, which exhibits strong photothermal effect under near-infrared light, can transform the analysis signal into heat with a pen-style digital thermometer as the signal reader. Therefore, oxTMB has the potential for simple and instrument-free analyses. Based on the photothermal effect of oxTMB, a simple but sensitive photothermal assay is developed for glucose detection with a linear range of 5–300 μM. The calculated limit of detection (LOD) for glucose was 0.13 μM. Considering that thermometers are widely used in instrument-free analyses, the proposed photothermal method may provide a more affordable way to detect biomarkers associated with biological diseases.