Mobile Phone Sensing of Cocaine in a Lateral Flow Assay Combined with a Biomimetic Material

Lateral flow assays (LFAs) are an ideal choice for drug abuse testing favored by their practicability, portability, and rapidity. LFA based on-site rapid screening devices provide positive/negative judgment in a short response time. The conventionally applied competitive assay format used for small molecule analysis such as abused drugs restricts the quantitation ability of LFA strips. We report herein, for the first time, a new strategy using the noncompetitive assay format via a biomimetic material, namely, poly(p-phenylene) β-cyclodextrin poly(ethylene glycol) (PPP-CD-g-PEG) combined with gold nanoparticle (AuNP) conjugates as the labeling agent to recognize the target cocaine molecule in the test zone. The intensities of the visualized red color in the test line indicate that the cocaine concentrations were analyzed via a smartphone application. Significantly, a combination of this platform with a smartphone application provides quantitative data on the cocaine amount, making it a very inventive and attractive approach especially for on-site applications at critical points such as traffic stops and the workplace.