Multifunctional Fe3O4@Au supraparticle as a promising thermal contrast for an ultrasensitive lateral flow immunoassay

An ultrasensitive lateral flow immunoassay (LFIA) strip has been developed based on a multifunctional photothermal contrast Fe 3 O 4 @Au supraparticle (Fe 3 O 4 @Au SP) for quantitative Ochratoxin A (OTA) detection. The Fe 3 O 4 @Au SP composite not only shows a better photothermal effect over Fe 3 O 4 and gold nanoparticles , but possesses magnetic property and excellent ability to directly adsorb protein (antibody). Under 808 nm irradiation, photothermal images of the test strips are recorded by a portable Infrared thermal camera. A quantitative analysis is easily achieved based on the thermal changes, which are proportional to the concentrations of analytes. Under an optimal condition, a wide linear detection range from 1 pg mL⁻ 1 to 1μgmL⁻ 1 and a limit of detection (LOD) at 0.12 pg mL⁻ 1 have been achieved with OTA as a model analytes. The practical application potential has also been validated by detection of OTA in spiked corn , peanut, and soybean extractives with overall recoveries ranging from 98.6% to 115% and coefficient of variations (CVs) between 6.06% and 12.73%. The photothermal LFIA renders a rapid, sensitive, and quantitative bio-/chemo-sensing platform with only a portable laser source and a thermal camera.