Development of Voltammetric Immunosensors for the Detection of Ultralow Concentration of Tumor Markers

Abstract

Cancer is one of the most profound global health issues that every country faces in today s world of modern medicine and technology. In India, breast and ovarian cancers are the most common cancers among middle-aged women. Early detection of cancer is one of the most significant challenges faced by medical practitioners when determining and administering proper treatment and required patient care. Immunoassay is the most frequently used type of diagnostic tool that quantitatively measures the over expressed specific proteins associated with certain tumors. However, majority of the immunoassay methods in practice have insufficient sensitivity to detect cancer at an early stage. In this thesis, nanomaterials were used as a platform for bioconjugation and biorecognition to increase the sensitivity of voltammetric immunosensors for the detection of ultralow concentration of tumor markers. Gold nanoparticles (AuNPs) were employed due to their biocompatibility, oxidation resistant and non-toxic nature. Additionally, graphene-metal nanocomposites with enzyme mimicking property and high electrochemical activity were investigated to overcome the limitations with enzyme-based immunosensors. Firstly, the thesis work discusses about the synthesis and characterization of enzymatic and non-enzymatic nanolabels. An enzymatic nanolabel, horseradish peroxidase labeled anti-IgG conjugated gold nanoparticle (AuNP-HRP-anti-IgG), was synthesized using citrate capped gold nanoparticle. The non-enzymatic nanolabels, anti-IgG conjugated gold nanoparticle decorated reduced graphene oxide (rGOAu-anti-IgG) and anti-IgG conjugated silver nanoparticle decorated reduced graphene oxide (rGOAg-anti-IgG), were synthesized using a one pot reduction of graphene oxide and their corresponding metal ions, which was then followed by conjugation with the antibodies. For the purpose of signal amplification in immunosensing, the nanolabels were characterized by spectroscopic and microscopic techniques. Secondly, the fabrication, haracterization ..