Immunosensors are used to provide simple, quick and effective ways to detect analytes for the diagnosis of a number of diseases. This work reports on a novel optical immunosensor based on thyroxine antibody labeled gold nanoparticles (anti-T4/C-AuNPs) for the sensitive detection of the thyroxine (T4) hormone. T4 hormone is a reliable diagnostic biomarker present in the human blood serum that is necessary for normal neural development and cellular metabolism. The free T4 hormone, a major key player of the total biologically active T4 hormone, in serum regulates the patient's thyroid function. The immunosensor was synthesized by using amine functionalized cysteamine capped gold nanoparticles (C-AuNPs) of size 36 nm approximately. The T4 specific antibody (anti-T4) was covalently attached to C-AuNP by EDC-NHS (1-ethyl-3-(-3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide) cross-linking chemistry. This anti-T4/C-AuNP bioconjugate was used for the analysis of the free thyroxine hormone in samples. The proposed method exhibited high performance immunosensors having a linear range of 0.52 to 65.1 pg/mL and the detection limit of 9.11 pg/mL.

A new dimension for the fluorescence “turn-on” detection of SO32− by Au NCs with potential applications towards the development of a hydrogel based platform and intracellular detection.

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