Fig. 3
The EPOCH system has three modules for on-site THC assay: (i) a sample processing kit for extracting oral fluid and labeling with AuNP-THC antibody, AuNPab; (ii) an injection-molded cartridge housing membrane sensors; and (iii) a detection cradle for optical signal detection. The processing kit, paired with the sensor cartridge, delivers AuNPAb-oral fluid mixture to test and control sites. The sample-spotted cartridge is inserted into the cradle and imaged by a smartphone camera. 5-min THC detection. (Left) An oral-fluid sample is collected using a swab. (Middle) oral fluid is extracted and mixed with AuNPab. The mixture is then spotted on a radial membrane sensor that has immobilized THC competitors (THC haptens conjugated to bovine serum albumin carriers; THCBSA). (Right) AuNPab differentially binds to THCBSA according to oral THC concentration. Transmission through the sensing spot is digitized for THC quantification