A portable fluorescent lateral flow immunoassay system for ultrasensitive point-of-care detection of multiple illicit drugs

Abstract

Drug abuse poses a significant threat to global public health and social stability, underscoring the urgent need for on-site rapid detection platforms to curb drug circulation, facilitate early intervention, and support law enforcement efforts. In this study, we report the development of a fluorescent lateral flow immunoassay (LFIA) platform based on a silica core double quantum dot shell (SDQD) nanocomposite for highly sensitive, point-of-care (POC) detection of the cocaine (COC) metabolite benzoylecgonine (BE), ketamine (KET), methamphetamine (MET), and morphine (MOP). The double-shell architecture of the SDQD, compared to traditional single-layer quantum dot beads (QBs), provides a significantly higher QD loading capacity. This unique structure not only dramatically amplifies the fluorescence signal but also presents a high density of functional groups for more efficient antibody conjugation, enhancing assay sensitivity. Concurrently, the inert silica core provides exceptional colloidal and photostability, overcoming common limitations of conventional fluorescent labels. Furthermore, a miniaturized four-channel fluorescent immunochromatographic analyzer, integrating optical and electrical components, was designed. This device offers a low-cost, user-friendly solution and incorporates advanced fluorescence signal extraction algorithms to facilitate rapid, automated data processing and noise reduction. Leveraging the superior signal amplification and stability of the SDQD labels, the LFIA test strips demonstrated outstanding detection limits (LODs) of 0.13 ng mL⁻¹ for BE, 0.08 ng mL⁻¹ for KET, 0.1 ng mL⁻¹ for MET, and 0.03 ng mL⁻¹ for MOP. Crucially, the system also exhibited high accuracy in detecting these target substances in complex biological matrices, validating its practical applicability and reliability. The high sensitivity, portability, and cost-effectiveness of this platform highlight its significant potential for real-time, on-site drug screening applications, particularly in border security, roadside drug testing, and forensic investigations. Its integration into law enforcement and public safety operations could drive technological advancements and enhance the efficiency of illicit drug detection methodologies.