An ultrasensitive microfluidic chip-based immunoassay for multiplex determination of 11 PDE-5 inhibitors in adulterated health foods

Multiclass chemical contamination of food has aroused growing attention due to the increasingly co-occurrence of multiple contaminations, such as illegal additives (sildenafil and tadalafil adulterants) in health food. In the present study, an ultrasensitive multiplex microfluidic chip-based assay towards sildenafil and tadalafil adulterants was developed. Dramatically enhanced sensitivity and assay convenience were obtained based on our prepared brightly fluorescent signal reporters, effective microfluidic chip-based analyte enrichment strategy and a mobile detection platform. Under optimal conditions, this method could detect 11 sildenafil and tadalafil adulterants with low limits of detection (0.027–0.066 ng/mL) and low cut-off values (2.0–9.0 ng/mL). High accuracy and precision were validated due to the reasonable recoveries (94.3%~99.8% for tadalafil, 87.8~112% for sildenafil) and acceptable coefficient of variation (2.81–11.2%). Comparison experiments between this work and LC-MS/MS analysis found good agreement in the simultaneous screening of total sildenafil and tadalafil adulterants in capsule, tea leaves, instant coffee and health wine samples. This new assay format can be extensively employed in ultrasensitive field detection of multiple PDE-5 inhibitors within minutes, while also providing an easy-to-operate and low-cost multiplex detection protocol.