Smartphone-based mobile digital pressure sensor for quantitative point-of-care testing of respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is a major cause of acute respiratory tract infections in infants and elderly individuals, leading to hospitalisation and potentially fatal outcomes, posing a serious threat to global health and economy. This study proposes a smartphone-based mobile digital pressure sensor (smartphone-MDPS) for the quantitative detection of the RSV fusion protein (RSV-F) in clinical nasopharyngeal samples. The smartphone-MDPS utilized two monoclonal antibodies (mAbs) specific to the F protein, of which mAb1 was conjugated with Au@PtNPs (Au@PtNPs-mAb1) as the detection antibody and mAb2 was coupled with magnetic beads (MB-mAb2) as a coating antibody to establish a novel sandwich immunoassay. During the immune reaction, the substrate H₂O₂ was catalyzed to release O₂ gas by the Au@PtNPs nanozyme within the Au@PtNPs-mAb1-RSV-F-mAb2-MB immunocomplexes. The pressure intensity of O₂ was measured using a mobile digital pressure sensor and transmitted wirelessly to a smartphone application for analysis. The programming codes for the sensor module and Android app were developed considering the performance requirements of the smartphone-MDPS. With a quantitation range of 0.09-1.953 ng/mL, the system had a limit of quantitation (LOQ) of 0.09 ng/mL and a limit of detection (LOD) of 0.03 ng/mL. When nasopharyngeal samples from 27 patients with RSV infection and 46 healthy individuals were tested, the smartphone-MDPS and enzyme-linked immunosorbent assays (ELISA) exhibited 100 % positivity and specificity as well as a strong correlation coefficient (R² = 0.991) for quantitative measurements between these two assays. In conclusion, the smartphone-MDPS has high portability, affordability, efficiency, sensitivity, and specificity, making it a promising immunoassay for quantitative point-of-care testing of RSV infection.