Grating-coupled fluorescent plasmonic (GC-FP) biosensor for point-of-care serological detection of Lyme Disease

Timely and accurate diagnosis of Lyme disease (LD) remains limited by complicated serological testing, which requires specialized laboratory equipment and has a multi-day turnaround, thereby limiting its utility in point-of-care (POC) settings. We have previously demonstrated a grating-coupled fluorescent plasmonic (GC-FP) biosensor in a microfluidics-based format (MF) for serological detection of LD. In this work, we demonstrate translation of an MF to a simplified dipstick (DS) assay. The assay utilizes miniaturized 4 × 4 mm gold-coated chips with a nanoscale grating that enhances fluorescence through surface plasmon-coupled emission (SPCE). The unique dipstick-based workflow eliminates the need for microfluidic pumps and complex instrumentation, with a total assay time of 24 min. The DS format integrates both tiers of the standard two-tiered diagnostic algorithm on a single chip, enabling simultaneous detection of first-tier screening antigen C6 and second-tier confirmatory antigens VlsE, DbpA, and DbpB. Validation was performed using thirty human serum samples tested in DS GC-FP chips, MF GC-FP chips, and a commercially available FDA-approved LD diagnostic assay (ZEUS Borrelia MTTT®). Using a strict two-tiered scoring approach, the DS format achieves 93.33% accuracy, 86.67% sensitivity, & 100% specificity with the limited sample set that was tested. With a single-tiered scoring approach, the DS format yielded equivalent diagnostic results to the MTTT and MF formats. The DS format substantially reduces equipment requirements, material costs, and operational complexity while preserving diagnostic accuracy, making it well-suited for deployment in urgent care centers, physician offices, and resource-limited settings.