A portable, affordable and simple detector is requested in a “Point-of-Care-Testing” (POCT) system. In this study, we exploited the potentialities of Differential Pressure Gauge (DPG) to the orientation of POCT technology. Alpha fetoprotein (AFP) was chosen as a model analyte that could specifically recognized by its antigen, and a tiny outfits equipped with a DPG was employed as the signal readout. Pt/SiO2 nanospheres were synthesized and modified with the detection antibody. In the presence of target, a sandwich of immunocomplex specifically formed and the Pt/SiO2 had been modified on the capture antibody. Which then can be dissolved to release plenty of Pt and the suspensions were transferred into a closed vial filled with appropriated amount of hydrogen peroxide. Subsequently, hydrogen peroxide was decomposed to produce oxygen, resulting in the enhancement of pressure in the closed vial and which can be detected by DPG easily. Under the optimized conditions, the read out signal from DPG had a direct relationship with AFP concentrations in the range of 10~200 ng/mL, and the detection limit was as low as 3.4 ng/mL. The proposed portable sensor had been successfully applied to detect AFP in serum samples with satisfactory results. This strategy holds a great promising in biological analysis as its convenient operations, reliable results and flexible apparatus.

A simple sensor utilizing a simple aminoquinoline derivative (5-(quinolin-8-yliminol) pentanal, QYP) has been successfully developed for the naked-eye colorimetric assay of pH. The QYP compound presents strong solvatochromism due to the solute-solvent interaction, and it is sensitive to a pH change in the solution. The color of the solution changes from orange to colorless upon increasing the pH value, which is well consistent with the corresponding UV/vis absorbance variation. UV absorbance has a direct linear relationship with the pH values in the range of 4.0 to 8.0 in phosphate-buffered saline, and the corresponding color variation could be distinguished readily by the naked eye.

A commercially available micro-pressure sensor was employed to fabricate an analytic platform for detecting biomedical targets based on the fact that hydrogen peroxide can be decomposed by catalase to produce oxygen, which reinforces the pressure in a closed container.