In recent years, gold nanoparticles were used in a variety of fields, including catalysis, electronics, photonics, as well as nanomedicine, and chemical and biological sensing. Their wide range of applications comes from their unique optical, electromagnetic, and conductive properties, in addition to their good biocompatibility and ease of functionalization and modification with biomolecules. The use of magnetic gold-coated nanoparticles (M-AuNPs) is advantageous because of the combined above-mentioned gold nanoparticle properties, along with the ability to use magnets to control the particles' position in space. This property is especially useful for the collection of particles after each step of modification [1-3].
Human growth hormone (hGH), also known as somatotropin, is a peptide hormone which is secreted by the anterior pituitary gland. hGH is essential for normal human growth and development, and is involved in such biological processes as lactation, somatogenesis, and activation of microphages. An imbalance of hGH causes various diseases, thus sensitive determination of the hormone is essential [4].
The main aim of this study was to develop an immunoassay for the determination of hGH using M-AuNPs. Synthetized M-AuNPs were characterized spectroscopically and using transmission electron microscopy. In this work, monoclonal antibodies against human growth hormone (m-anti-hGH) were covalently immobilized onto the surface of M-AuNPs using a self-assembled monolayer. After m-anti-hGH interaction with hGH, polyclonal antibodies against human growth hormone labelled with biotin (p-anti-hGH-B) and streptavidin-labelled horseradish peroxidase (S-HRP) were added. Then a mixture of 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide as a substrate for the enzymatic reaction was added, and the absorbance of solution after the addition of sulfuric acid was registered.