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. Author manuscript; available in PMC: 2022 May 23.
Published in final edited form as: Sci Transl Med. 2021 Oct 20;13(616):eabe2352. doi: 10.1126/scitranslmed.abe2352

Fig. 1. EPOCH assay overview.

Fig. 1.

(A) The EPOCH system has three modules for on-site THC assay: i) a sample processing kit for extracting oral fluid and labeling with 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. (B) A photo of a compact prototype system. (C) 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 BSA carriers; THCBSA). (Right) AuNPAb differentially binds to THCBSA according to oral THC concentration. Transmission through the sensing spot is digitized for THC quantification.