Multifunctional Nano-Sunflowers with Color-Magnetic-Raman Properties for Multimodal Lateral Flow Immunoassay

Multimodal lateral flow immunoassay (LFIA) has shown promise for improving both the flexibility and practicability of point-of-care test. We report here a facile, in situ growth method for preparing multifunctional core-shell-shell nano-sunflowers with a unique combination of color-magnetic-Raman properties. The use of Fe₃O₄ nanobeads with high saturation magnetization as the magnetic core allowed for robust magnetic signal strength-even after successive coatings of polydopamine and gold nanoparticles (Au NPs). Carefully selected 4-mercaptobenzonitrile molecules not only contributed to the growth of the Au NP shell but also generated a strong, surface-enhanced Raman scattering signal. The resulting nanomaterials were successfully used in the construction of multimodal LFIA with one qualitative and two alternative quantitative detection modes of different sensitivity levels. The limit of detection for the paradigm target-human chorionic gonadotropin-was 10 mIU/mL in color mode, 1.2 mIU/mL in magnetic mode, and 0.2 mIU/mL in Raman mode.