Nanomagnetic lateral flow assay for high-precision quantification of diagnostically relevant concentrations of serum TSH.

Thyroid stimulating hormone (TSH) is the first-line marker for initial evaluation of the thyroid gland function. We present a lateral flow immunoassay based on superparamagnetic nanolabels for rapid (<25 min) quantitative determination of TSH at a point of care. The demonstrated limit of detection (LOD) of 0.017 μIU/mL in human serum is on the level of third-generation TSH laboratory tests. The wide linear dynamic range of more than 3 orders covers the whole range of clinically relevant TSH concentrations for confident quantitative diagnostics of the gland function from hyper- to hypothyroidism, and different states in-between. The attractive values of LOD and linear dynamic range are due to counting of the superparamagnetic nanolabels over the whole reaction volume by their non-linear magnetization at two frequencies of an alternating magnetic field and detecting the response at combinatorial frequencies. The developed cost-efficient and user-friendly immunoassay can be used for express in vitro diagnostics and long-term quantitative monitoring of thyroid dysfunctions, especially in distant regions, developing countries, and sparsely populated areas.