Magneto-Plasmonics-Enhanced Colorimetric Lateral Flow Immunoassay Using Magnetic-Gold Nanostars

Colorimetric lateral flow immunoassays (LFIA) have revolutionized point-of-care testing (POCT) methods by providing simple, rapid, accessible, and instrumentation-free detection of infectious diseases. However, conventional LFIAs relying on gold nanospheres (GNPs) can suffer from limited sensitivity due to weak colorimetric signal intensity at the test line, restricting their diagnostic potential. To overcome this limitation, we developed a magneto-plasmonics enhanced colorimetric LFIA (mpLFIA)- a breakthrough platform that integrates a novel hybrid nanoparticle system-magnetic gold nanostars (mpGNS). By leveraging dual enhancement mechanisms - magnetic preconcentration and plasmonic amplification through the gold nanostar shell coating of the magnetic core- the mpLFIA achieves unprecedented signal intensity and detection performance. Among the tested mpGNS variants, mpGNS-3- distinguished by its longest spikes and highest branch density- emerged as the most effective colorimetric signal amplifier when evaluated using Rift Valley fever virus (RVFV) nucleoprotein as a model analyte. Our mpLFIA platform achieves an outstanding limit of detection (LOD) of 2.24 pg/mL for RVFV nucleoprotein in 1X PBS buffer, demonstrating a 1000-fold enhancement over conventional GNP-based assays. Our prototype mpLFIA platform, utilizing highly spiked mpGNS-3, exhibits great potential as a powerful bioanalytical tool, combining high sensitivity with practical portability for point-of-care applications.