Blood contains a range of protein biomarkers that could be used in the early detection of disease. One important biomarker is human epidermal growth factor receptor 2 (HER2) which is overexpressed in the most common breast cancer. Various HER2 detection techniques have been reported, including FISH or IHC based assays, however, these techniques require sophisticated instrumentation, special training, are labor intensive and time consuming. Therefore, alternative bio-recognition elements are desirable to develop stable biosensors for sensitive detection.
Aptamers are known to be stable, cheap, easily chemically modified and can be produced in bulk with limited batch to batch variability. Furthermore, the unique binding properties of aptamers have shown great potential for biosensors using optical, electrochemical, and mass-sensitive approaches. Taking advantage of aptamers and enhanced sensitivity of electrochemical biosensors, Arya et al. 2018 developed easy point-of-care platform for sensitive detection of HER2 in undiluted human serum (Figure 1).
Figure 1. Schematic representation of aptamer electrode preparation
A thiol terminated DNA aptamer with affinity for HER2 was used to prepare the bio-recognition layer via self-assembly on interdigitated gold surfaces. Non-specific binding was prevented by blocking free spaces on surface via phosphate buffer saline-tween 20 blocker. Functionality of the chip was proven by measuring the capacitance for different HER2 concentrations binding to the sensing surface in the presence of PBS and serum. The HER2 present in buffer/serum sample was captured by the DNA aptamer, which resulted in the displacement of water molecules and ions away from the electrode surface. This insulating effect of the protein bound to the sensing surface resulted in a change in the capacity, that was measured by the electrochemical impedance spectroscopy (IES), allowing quantification of HER2 in both buffer and undiluted human serum. Plotted calibration curves show concentration-dependant decrease of capacitance values, proving the successful capture of HER2 protein by aptamers (Figure 2).
Figure 2. Capacitive measurement via electrochemical impedance for HER2 in PBS and Serum.
The aptasensor exhibited logarithmically detection of HER2 from 1 pM to 100 nM in both buffer and undiluted serum with limits of detection lower than 1 pM.
This design of aptamer based electrochemical biosensor exhibited better response as compared with previously reported HER2 sensors and also worked on lower frequencies. Overall, the aptamer based biosensor platform is better for quick, simple and low cost point-of care detection of HER2 in real samples. At Aptamer Group, similar biosensors have been developed for protein biomarkers and even small molecule detection using our high affinity aptamers. If you would like more information on such platforms, please contact us using the form below.
Reference: Arya SK, Zhurauski P, Jolly P, Batistuti MR, Mulato M, Estrela P (2018) Capacitive aptasensor based on interdigitated electrode for breast cancer detection in undiluted human serum. Biosens Bioelectron 102:106–112.