Abstract
This research investigates the use of selected nanomaterials for the electrochemical detection of cancer biomarkers, especially those related to women, since the incidence of cancer in women has increased over the years. The Alpha-fetoprotein (AFP), a liver, ovarian cancer, squamous cell carcinoma of the cervix biomarker, and the human epidermal growth factor receptor 2 (HER 2), a breast cancer biomarker used for clinical test, served as immunosensor for this work. AFP is also significant in detecting genetic problems and birth defects in early pregnancy. The reasons stated above necessitated their choice as relevant cancer biomarkers. The nanomaterials employed in this work include carbon black nanoparticles (CBNPs), palladium nanoparticles (PdNPs), carbon nanofibers (CNFs), gold nanoparticles (AuNPs) and nanoDiamond (nanoD). These nanomaterials were selected due to their unique, individual and cooperate properties which result in high electron transfer, electrocatalytic activity and good biocompatibility. The large surface area and electronic properties of these nanomaterials were observed to bring about good and significant signal amplification at the electrode interface and low detection limits. Also, improving electrochemical response of the immunosensor.
These nanomaterials were drop coated and/or electrodeposited on the glassy carbon electrode (GCE) as substrate before they were electrochemically characterised in 5 mM ferri/ferrocyanide solution and 0.1 M KCl redox probe using the cyclic voltammetry (CV) and electrochemical impedance techniques. The electrochemical immunosensor was also run in 5 mM ferri/ferrocyanide solution and 0.1 M KCl to detect various concentrations of the cancer biomarkers, especially the AFP and HER 2. Square wave voltammetry (SWV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) were utilised for the electrochemical detection of the cancer biomarkers under optimal conditions of incubation temperature, time, and pH. The GCEs were modified with the nanomaterials
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(CBNPs, CNFs) after dispersion in either dimethyl formamide (DMF) or de-ionised water after sonicating for 1 h. The electrodeposition method was further employed for the immobilisation of PdNPs and AuNPs. The antibody - AFP was immobilised overnight, and later, the bovine serum albumin (BSA), the blocking agent for reducing non-specific binding, was immobilised for 4 h at 4 ℃. The biorecognition of the antibody-antigen interaction is further confirmed by immobilising 20 μL of antigen - AFP at 30 ℃ for 30 min and 35 ℃ for 40 min optimal conditions of incubation time and incubation temperature respectively for CBNPS / PdNPs platform and the CNF/AuNPs platform. Low detection limits of 0.0039 ngmL-1 and 0.0131 ngmL-1 from the SWV and EIS data were obtained for CBNPs / PdNPs platform at a wide linear range of 0.005 - 1000 ngmL-1; also, low detection limits of 0.50 pgmL-1 from SWV and 0.48 pgmL-1 from EIS measurements were obtained at a linear range of 0.005 - 500 ngmL-1 on the CNF/AuNPs platform. The prepared immunosensor exhibited excellent selectivity, good repeatability, excellent stability, and good percentage recovery in human serum matrixes.
NanoDiamond/ gold nanoparticles (nanoD/AuNPs) were utilised for the detection of the HER 2. This is to develop a facile, easy to prepare and effective electrochemical sensor for the early detection of breast cancer and other women-related cancer tumours. The HER 2 immunosensor platform of nanoD/AuNPs had a low detection limit of 0.29 pgmL-1 obtained from the DPV measurements. A good linear range of 1 pgmL-1 – 50 ngmL-1 was applied at an optimal incubation temperature of 35℃ and incubation time of 50 min at a pH of 7.2. The immunosensor displayed good reproducibility, excellent stability, good selectivity, good repeatability, and good percentage recovery in human serum matrixes. However, these developed electrochemical immunosensors show point-of-care and clinical advantages because it is sensitive, selective, fast, require small sample volumes, are non-invasive and are easy to miniaturize for early detection of cancer biomarkers.