Lab-on-a-syringe: On-site and sensitive detection of cucumber green mottle mosaic virus based on multi-functional piston valve and immunomagnetic separation

Cucumber green mottle mosaic virus (CGMMV) has long infected cucurbit crops, particularly melons and watermelons, resulting in substantial economic losses. Early and accurate quantification of CGMMV are essential for managing viral outbreaks and ensuring fruit quality and safety. Conventional ELISA and RT-PCR methods are limited by several drawbacks, including low detection sensitivity, limited automation, high equipment dependency, and susceptibility to contamination, which collectively restrict their field applicability. To address these limitations, a lab-on-a-syringe platform was proposed for the on-site and sensitive detection of CGMMV based on a multi-functional piston valve combined with immunomagnetic separation. The core innovation lay in the piston valve’s ability to execute complex fluidic sequences using only a single programmable screw motor, minimizing system complexity. Specifically, a double-antibody sandwich complex was formed using immunomagnetic beads (MNBs) and HRP-conjugated antibodies, generating a fluorescent signal via HRP-catalyzed ADHP-to-resorufin conversion. The piston valve-syringe coordination enables integration of immunomagnetic capture, separation, washing, and fluorescence detection of CGMMV. Under optimized conditions, the lab-on-a-syringe platform enabled sensitive detection of CGMMV in watermelon leaf samples down to 2.77 pg/mL within 45 min, demonstrating a correlation coefficient ( R² ) of 0.985 compared with the national standard method, along with an average recovery rate of 102.94%. The proposed system constituted a promising approach for highly sensitive immunological pathogen point-of-care testing (POCT) in resource-limited settings.