On-Site Microfluidic Assay for the Detection of Multiple Drugs in Urine

Immunoassays are widely used for preliminary drug screening.
While
lateral flow assays (LFAs) offer rapid and portable testing, they
often suffer from limited sensitivity and subjective interpretation.
In contrast, laboratory-based immunoassay systems provide high precision
but are unsuitable for field use due to their size and cost. To address
these limitations, we developed a portable fluorescence-based microfluidic
assay capable of detecting methamphetamine (MET), benzoylecgonine
(BE), 11-nor-9-carboxy-tetrahydrocannabinol (THC-COOH), and benzodiazepines
(BZOs) in urine specimens within 5 min. They were selected based on
both global and domestic prevalence, as well as the detection capability
of the developed microfluidic chip, which was designed to simultaneously
target all four. The assay comprises a portable reader and a chip
with two channels, each aligned with drug-specific antibodies, enabling
simultaneous detection. The assay was tested against standard concentrations
of the target drugs, delivering accurate test/reference ratios and
signal displacements at threshold levels. We evaluated urine specimens
(N = 141) provided by the National Forensic Service
in Korea, including drug-free controls (N = 30) and
cases confirmed for MET (N = 30), THC-COOH (N = 30), and BZOs (N = 13), along with
samples from Paraguay for BE (N = 38), using validated
diagnostic techniques. Analysis of 141 authentic urine specimens,
encompassing verified instances of both single and poly drug use,
showed high sensitivity and specificity with minimal cross reactivity.
This study confirms that the microfluidic assay is effective in detecting
multiple drugs simultaneously, offering high accuracy, cost-effectiveness,
and portability, with excellent sensitivity for each drug tested.