Electrochemical Impedance Spectroscopy Characterization of Label-free Biosensors for the Detection of HER2 in Saliva

Breast cancer is the leading cancer site for women with 2 million new yearly infections and more than half a million dead worldwide. Human Epidermal Receptor 2 (HER2) is a prominent breast cancer biomarker that indicates aggressive cancer and is often associated with a bad prognosis and low survival rates. However, current detection methods for HER2 are often time-consuming, expensive, and require a high level of expertise.

Biosensors are devices that turn biological interaction into a readable electronic signal; they are known for their high specificity and selectivity for low concentration, as well as their low cost and ease of use, thus making them a better alternative to traditional methods. Also, Saliva is becoming a better alternative for blood for the detection of biomarkers due to its non-invasive collection in large quantities with simple collection methods with a richness in disease biomarkers including HER2. Thus this project aims to develop a label-free, low cost, electrochemical biosensor for the detection of HER2 in saliva.

This was done by first depositing diazonium salt onto a screen-printed electrode (SPE) through cyclic voltammetry, then immobilizing anti-HER2 antibodies on the activated SPE using the EDC/NHS protocol [1]. HER2 biomarker concentrations were detected using electrochemical impedance spectroscopy inside a microfluidic system. The biosensor showed a higher linear detection of HER2 (Y= 0.0062 X + 0.1066/ R² = 0.9909) in its physiological concentration range of 5 and 40 pg/mL when compared to other interference proteins: Epidermal Growth Factor Receptor (Y= 0.0016 X + 0.0188/ R² = 0.8072) and Human Epidermal Receptor 3 (Y= (0.0035 X + 0.0225/ R² = 0.1302). The biosensor was then used to detect 10 pg/mL of HER2 concentration in real saliva using the standard addition methods (Y = 0.0118 X + 0.1282/ R² = 0.9876).

Reference

1. Abrao Nemeir, I. et al. Impedimetric label-free detection of salivary EGFR on screen printed electrode. Integr. Cancer Sci. Ther. 2019, 6, 1–3.