A Paper-Based Fluorescent Sensor for Rapid Early Screening of Oral Squamous Cell Carcinoma

Various types of sensors play an irreplaceable role in the detection of biomarkers, but their high cost and complicated operation make it difficult to benefit ordinary people. Herein, we develop a low-cost, double-layered, paper-based fluorescent sensor (CP/HQ) structurally consisting of the upper reaction layer loaded with two oxidases (lactate oxidase and choline oxidase) and the bottom fluorescent layer that physically associates with the porphine-grafted composite fluorescent polymer colloids (PF-PDMTP/HQ). Based on the dramatic and rapid fluorescence decrease of porphine induced by the oxidation between saliva and oxidases and subsequent fluorescence resonance energy transfer from oxidized hydroquinone, the resultant fluorescent paper sensor enables us to achieve visual detection of OSCC, which was further recognized by smartphone scanning as the grayscale variation. It was found that the linear sensing range of grayscale value are 10–200 μM for lactic acid and 10–100 μM for choline, with LODs of 5.7 and 8.9 μM, respectively. More importantly, the sensor can achieve a powerful detection capability comparable to that of high-performance liquid chromatography (HPLC) in clinical settings with simple operation, demonstrating its great application potential. Our proposed sensor not only improves the accuracy of OSCC diagnosis but also provides a valuable attempt for the device modification of polymer-sensing systems and the development of non-invasive and easy-to-operate disease screening methods.