A facile one-step gold nanoparticles enhancement based on sequential patterned lateral flow immunoassay device for C-reactive protein detection

Abstract A gold nanoparticle (AuNPs) enhancement strategy for lateral flow immunoassays (LFIAs) was previously reported to improve assay sensitivity. The multi-steps of detection resulted in a tedious procedure. In this report, to reduce this limitation, a sequential flow LFIA was introduced to perform the AuNPs enhancement in only single step operation using C-reactive protein (CRP) as a model analyte. The delay and non-delay channels created on nitrocellulose membrane (NCM) using wax-printing method were used to deliver immunoassay and AuNPs enhancement reagents to the detection zone sequentially. For the enhancing step, AuNPs were enlarged by the catalytic reaction of KAuCl4 and NH2OH•HCl. Under optimal conditions, a calibration curve was found in a range of 0.1-5 µg·mL-1 with a good linear correlation (R2 = 0.9953). The limits of detection (LOD) were found to be 0.1 and 0.001 µg·mL-1 for naked eye observation and calculation (3SD/slope), respectively. Furthermore, the device shows no cross-reactivity with common interferences for CRP. The platform was successfully applied to detect CRP in certified human serum samples within 15 min, demonstrating the simplicity and speed of the AuNPs enhancement strategy platform. These promising results suggest that the new device may be used as an alternative tool for CRP detection and other biomarkers for POCT analysis.