An Ultrasensitive Electrochemical Pepsin Immunosensor Based on Heterogeneous Ag@Co(OH) ₂ NWs for Rapid Diagnostic Testing of Aspiration Pneumonia

Aspiration pneumonia (AP), caused by the microinhalation of gastric contents, is easy to miss because of its nonspecific symptoms and is associated with a high mortality rate (46.1%) over a short disease course. Current diagnostic methods for aspiration pneumonia, including medical imaging and bronchoscopy, are difficult to use for onsite and rapid diagnosis because they require bulky and time-consuming equipment. In this work, we propose an ultrasensitive electrochemical immunosensor to achieve fast determination of the AP biomarker (pepsin) in the bronchoalveolar lavage fluid (BALF) of AP patients. This immunosensor works through the construction of heterogeneous Ag@Co(OH)₂ NWs to simultaneously provide both high electrocatalysis and high conductivity. In terms of architecture, Ag NWs can contribute abundant active sites for antibody immobilization to achieve target capture ability while accelerating electron transfer. In addition, the uniformly distributed Co(OH)₂ nanoparticles intensify the response signal because of their high redox capacity. Through the above synergetic effects, our immunosensor enables the recognition and reporting of trace amounts of pepsin in patients' BALF within only 20 min, which is at least two times faster than that of clinical techniques. Moreover, the high diagnostic accuracy of the immunosensor is comparable to that of CT images from clinical AP patients. This facile immunosensor is promising for providing new insights into the early diagnosis of AP to guide clinical treatment onsite.