An all-in-a-syringe immunoassay using autoinjected visual distance readout for simple quantitative testing of cancer biomarkers

Quantitative testing of cancer biomarkers is of significance in early diagnostics of the disease. Herein, we developed an all-in-a-syringe immunoassay using autoinjected visual distance readout for simple quantitative testing of prostate specific antigen (PSA) as a model target. The whole immunoassay protocol was conducted in a single disposable syringe, while employing it as the host of the immuno-recognition system, the tool for reagent handling and autoinjected distance readout of the assay signals. The sandwich-type immuno-recognition system was constructed on the inner polypropylene wall of the syringe cylinder. In the presence of H 2 O 2 , the peroxidase-mimic activity of immuno-captured platinum nanoparticles (Pt NPs) in the cylinder drove the automatic injection of liquids into the catheter of the syringe, quantitatively displaying the assay signals as autoinjected visual distance parameters. The assay was integrated into a three-dimensional (3D)-printed device for easier manipulation. Without the aid of any laboratory pipettes, specialized detectors and complex sealing treatments of the device, PSA was detected at a limit of detection (LOD) of 0.43 ng/mL with acceptable accuracy in testing clinical serum samples. This is the first exploration of all-in-a-syringe for quantitative immunoassay, which possesses great potential for simple testing of cancer biomarkers, given the versatility of syringes.