“Three-in-One” Multifunctional Nanohybrids with Colorimetric Magnetic Catalytic Activities to Enhance Immunochromatographic Diagnosis

Colorimetric lateral flow immunoassay (LFIA) with gold nanoparticles (AuNPs) as signal reporters has been widely used in point-of-care testing. Nonetheless, the potential of traditional AuNP-based LFIA for the early diagnosis of disease is often compromised by limited sensitivity due to the insufficient colorimetric signal brightness of AuNPs. Herein, we develop a "three-in-one" multifunctional catalytic colorimetric nanohybrid (Fe₃O₄@MOF@Pt) composed of Fe₃O₄ nanoparticles, MIL-100(Fe), and platinum (Pt) nanoparticles. Fe₃O₄@MOF@Pt displays enhanced colorimetric signal brightness, fast magnetic response, and ultrahigh peroxidase-mimicking activity, which are beneficial to the enhancement of the sensitivity of LFIA by coupling with magnetic separation and catalytic amplification. When integrated with the dual-antibody sandwich LFIA platform, the developed Fe₃O₄@MOF@Pt can achieve an ultrasensitive immunochromatographic assay of procalcitonin with a sensitivity of 0.5 pg mL^-1, which is approximately 2280-fold higher than that of conventional AuNP-based LFIA and superior to previously published immunoassays. Therefore, this work suggests that the proposed catalytic colorimetric nanohybrid can act as promising signal reporters to enable ultrasensitive immunochromatographic disease diagnostics.