Specific Picomolar Detection of a Breast Cancer Biomarker HER‐2/neu Protein in Serum: Electrocatalytically Amplified Electroanalysis by the Aptamer/PEG‐Modified Electrode

Abstract

Specific and sensitive electroanalysis of blood‐circulating protein cancer biomarkers is often complicated by interference from serum proteins nonspecifically adsorbing at the biosensing interface and masking specific reactions of interest. Here, we have developed an electrocatalytically amplified assay for specific and sensitive analysis of human epidermal growth factor receptor‐2 (HER‐2/neu, a protein cancer biomarker over‐expressed in breast cancers) that allows us to avoid both the interference from bovine serum albumin (BSA) and electrocatalytic amplification of the signal stemming from the specific aptamer−HER‐2/neu binding. A HER‐2/neu‐specific thiolated aptamer sequence was co‐adsorbed on gold together with a C11 alkanethiol bearing two ethylene glycol (EG)2 head groups that prevented non‐specific adsorption of BSA. On such layers, electrochemical reduction of a ferricyanide redox indicator is inhibited and is shown to be electrocatalyzed by methylene blue electrostatically interacting with negatively charged HER‐2/neu. The electrocatalytic signal increased upon HER‐2/neu binding to the aptamer, which allowed 10−12–10−8 M HER‐2/neu detection in 1 % serum, being practically applicable for clinical testing. The developed strategy can be considered as general and applicable for the electroanalysis of other blood‐circulating proteins once the electrostatic compatibility between the protein and redox probe is established.

Studies on the Affinity‐based Biosensors for Electrochemical Detection of HER2 Cancer Biomarker

“…The specificity of receptor layer is necessary to discriminate a defined analyte in complex samples such as serum or blood. As the possibility of utilization of DNA aptamer as receptor layer for HER2 was previously shown , we decided to apply it as a primary receptor that was immobilized on the surface of the transducer‐gold electrode. Therefore, the preliminary experiments were dedicated to the optimization of the content of aptamer‐based monolayer.…”

“…A possibility of HER2 biomarker detection using aptamers was also shown . Aptamers are short, single‐stranded DNA or RNA molecules, which can change their conformation upon interaction with various kinds of analytes including metal ions, small organic dyes, proteins and cells .…”

The Translational Potential of Electrochemical DNA-Based Liquid Biopsy

“…Frontiers in Chemistry | www.frontiersin.org smart schemes to protect the sensing layer (Campuzano et al, 2019;Yang et al, 2019). This also holds for aptasensors that use thiol-PEG (Salimian et al, 2017) or zwitterionic peptides (Cui et al, 2017) as blocking agents, as well as mixed-self assembled monolayers for subsequent covalent immobilization of the receptor (Díaz-Fernández et al, 2019). In any case, sample collection needs harmonization.…”

Electrochemical Immuno- and Aptamer-Based Assays for Bacteria: Pros and Cons over Traditional Detection Schemes

“…100 CFU mL −1 of E. coli O157:H7 with no interference from E. coli K12, Salmonella typhimurium , or S. aureus were detected at the aptamer-modified three-dimensional interdigitated microelectrodes (3 µm in width and 4 µm in height) separated by insulating layers [ 153 ]. Antifouling properties of polyethylene glycol (PEG) in combination with its ability to inhibit the electrode reactions of ferri/ferrocyanide [ 154 ] were used to detect down to 10 CFU mL −1 of uropathogenic E. coli UTI89 in serum and urine at the Ab/reduced graphene oxide/polyethylenimine (PEI)-modified electrodes (Ab immobilization via formation of amide bonds with PEI and further electrode modification with pyrene-PEG) [ 155 ]. The biosensor discriminated wild type E. coli UTI89 from UTI89 Δfim strain.…”