Development of low-cost impedimetric biosensors for the quantitative detection of cortisol and the human growth hormone

Cortisol and human growth hormone can be used as reliable biomarkers for the response of the hypothalamus-pituitary-adrenal axis. The hypothalamus-pituitary-adrenal axis is complex and dependent on many factors. However, generally, increased cortisol production is the hypothalamus-pituitary-adrenal axis's physiological response to an external stressor. Growth hormone is also regulated through the hypothalamus-pituitary-adrenal axis and secreted from the anterior pituitary gland. Hence point-of-care sensing devices for the quantification of cortisol and growth hormone would be versatile for the diagnosis of hypothalamus-pituitary-adrenal axis activity. The practical uses for a stress indicator would be diverse, inclusive of the medical and pharmaceutical sectors as well as sports and performance. Therefore, this work discusses the development of two electrochemical biosensors, designed to accurately detect and quantify cortisol and growth hormone concentration levels with potential practical applications. The device relies on impedance values which are produced when cortisol and growth hormone are immobilized onto electrode surfaces through antibody-antigen bonding. Calibration data was achieved for both Gold (Au, 111) slide electrodes and inexpensive screen-printed gold electrode-based sensor biochips with a strong correlation between impedance and concentration of cortisol, with detection range 30-300 ng/mL for Au (111) platform and 60 – 360 ng/mL for screen-printed gold electrode platform, while recombinant human growth hormone detection range was observed 5-30 ng/mL using both Au (111) platform, and screen-printed gold electrode platform.