Glucose oxidase coupling with pistol-like DNAzyme based colorimetric assay for sensitive glucose detection in tears and saliva

Abstract Measuring glucose levels in tears and saliva is important for diagnosing and predicting several diseases without the need for intrusive procedures. Detecting low concentrations of glucose with high sensitivity is still a significant difficulty. A simple visual method was created to assess glucose levels in tears and saliva by utilizing glucose oxidase (GOx) to catalyze glucose and pistol-like DNAzyme (PLDz) for signal amplification. Specifically, the β-D-glucose in samples acts as the initial molecule that is identified and catalyzed by GOx to produce gluconic acid and H2O2. H2O2 triggered the self-cleavage of PLDz, resulting in the activation of the “part b” sequence to initiate catalytic hairpin assembly (CHA) and release the DNAzyme section in H1 probe. The DNAzyme functions as a peroxidase mimic, catalyzing the TMB–H2O2 system and leading to an increase in observable signals. The proposed approach demonstrated a low limit of detection of 0.32 µM and a broad detection range. Moreover, the proposed approach was effectively used to detect glucose in tears and saliva samples, indicating potential for diagnosing hyperglycemia-related disorders in clinical settings.