Probe-free and wash-free strategy for on-site testing of chloramphenicol in food based on differential encodable microspheres separation system

Real-time detection of chloramphenicol (CAP) in food can effectively safeguard food safety. However, traditional chloramphenicol detection methods require large testing equipment, specialized operators and long testing times, therefore portable and rapid CAP detection remain a challenge. Here, we present a differential encodable microspheres separation system based (DEMSs) rapid, portable and accurate detection of CAP. DEMSs utilize specific binding of CAP-Antibody in DEMSs to antigen (CAP) in sample and filtration separation using a customized microfluidic chip for probe-free and wash-free CAP immunoassays. Integrated microscopic optical system and smart counting algorithms based on Hough Circle Transform deployed on a smartphone app enable portable and on-site CAP detection. The experimental results showed that the limit of detection (LoD) of CAP is 24.3 pg/mL and the detection range is 30-50,000 pg/mL. The single testing time is only 16 min. The device offers a novel CAP immunoassay strategy. By replacing antibodies coupled to encoded microspheres in DEMSs, this system is expected to enable the detection of multiple substances in foods.