Functionalized gold nanorods (GNRs) as a label for the detection of thyroid-stimulating hormone (TSH) through lateral flow assay (LFA)

Thyroid-stimulating hormone (TSH) is an important biomarker of thyroid dysfunctions. Different types of nano biosensors have been developed to detect TSH. However, there is a lacuna in the development of sensitive paper-based nano biosensors due to less sensitivity and instability of the labels. Interestingly, the intense color and localized surface plasmon resonance (LSPR) property make gold nanorods (GNRs) an efficient lateral flow assay (LFA) label instead of spherical gold nanoparticles. The rapidity, simplicity and user-friendly functioning of LFAs make them a predominant technique compared to electrochemical techniques for point-of-care diagnosis. This proof-of-concept study underlines the role of stable GNRs as a novel label for LFAs. The TSH antibody functionalized GNRs can semi-quantitatively diagnose hyperthyroidism and hypothyroidism. The limit of detection (LOD) of the LFA is 0.3 mu IU/mL, determined by visually analyzing the color development at the test line without employing any quantification method. Moreover, the study provides a comprehensive understanding of seed-mediated synthesis and functionalization of GNRs, which would benefit the researchers in suitably designing the GNRs-based labels for LFAs. Considering their exceptional characteristics, GNR-based LFAs are expected to surpass other labelling nanomaterials in detecting various biological markers. This enhanced sensitivity could significantly improve the clinical utility of diagnostic kits.