A smartphone-based immunochromatographic strip platform for on-site quantitative detection of antigenic targets

To report the testing signal of an immunochromatographic assay for on-site quantitative detection, a portable and user-friendly smartphone-based biosensing platform is developed in this study. This innovative system is composed of an ambient light sensor inherent smartphone reader and a 3D-printed handhold device, a quantitative tool capable of directly interpreting carbon nanoparticle (CNP)-conjugated immunochromatographic strips. To showcase the platform capability, the smartphone-based immunochromatography system (SPICS) reader and device were successfully used in CNP strips for rapid detection of the early pregnancy marker human chorionic gonadotropin in female urine (HCG; limit of detection [LOD]: 0.30 mIU mL-1), prostate-specific antigen in patient blood (PSA; LOD: 0.28 ng mL-1) and ampicillin residue in animal milk (AMP; LOD: 0.23 ng mL-1). The results were fully correlated with conventional commercial instruments (R2 = 0.99). The SPICS platform exhibits significant advantages, including portability, cost-effectiveness, easy operation, and rapid and quantitative detection, making it a valuable on-site diagnosis tool for use in home and community healthcare facilities. In this paper, a new type of self-prepared carbon sphere is proposed for immunochromatographic strip labeling and quantification using a smartphone.