Platinum nanozyme-hydrogel composite (PtNZHG)-impregnated cascade sensing system for one-step glucose detection in serum, urine, and saliva

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Bovine serum albumin was used as a nucleation template and stabilizer to prepare platinum nanozymes with high and specific peroxidase-like activity. Together with glucose oxidase, the best-performing nanozyme was entrapped in the 3D porous matrix of a polyethylene glycol hydrogel to fabricate the platinum nanozyme-hydrogel composite (PtNZHG). PtNZHG affords an independent glucose sensing unit, where the catalytic cascade reaction occurs with minimized diffusion resistance of unstable intermediates. This sensing unit was embedded within the confined detection zone of a plastic chip with a 3D hydrophilic fluid path to produce an efficient platform for the stand-alone detection of glucose. The glucose-containing sample was introduced into the device by capillary force, and the colored product generated by the catalytic cascade reaction was concentrated at the detection zone to markedly amplify the colorimetric response and thus increase detection sensitivity (detection range = 0.01–10 mM, detection limit = 3.9 µM). One-step glucose detection could be completed within 15 min, and analysis could be performed using a smartphone camera. The feasibility and practicality of our sensing system were demonstrated by the high recoveries of 83–105% observed for serum, urine, and saliva samples, the high specificity toward glucose without significant interference (<1%) from other sugars, and excellent long-term stability and reproducibility after two-month storage. Thus, our results are expected to advance the monitoring of glucose in human fluids and promote the biosensing of other substrates.