Electrochemical Biosensor for Small Molecules Detection

Small molecules such as ATP, ions, and hydrogen peroxide (H₂O₂), cortisol play important roles in the regulation of various physiological and pathological processes such as glucose levels, blood pressure, and carbohydrate metabolism. Their aberrant levels have been found to be significantly indicative in various clinical diagnoses. Thus, the measurement of small molecule (or other similar metabolites) levels in the body is an important diagnostic tool, both in clinical settings and during certain stress-intensive activities. Recent years, the electrochemical biosensor technology that are easy to use and enable the quick detection of small molecules of interest have been the focus of research.

Electrochemical Aptasensors for K⁺ Detection

Scientists developed a K⁺ aptasensor utilizing the digestion reaction of RecJ_f exonuclease. A single DNA probe with stem-loop structure was designed and located on the gold electrode through covalent thiol-gold bonds. The probe contained an anti-K⁺ aptamer sequence, which formed a G-quadruplex structure in the presence of K⁺. The working principle of this K⁺ aptasensor is shown in Figure 1.

Fig.1 Scheme of the K⁺ aptasensor based on RecJ_f exonuclease cleavage. (Han, 2016)

Electrochemical Biosensor for Monitoring Cortisol Using MIP

The sensor was fabricated using molecularly imprinted polymers (MIP) and cortisol was chosen as a model analyte. Cortisol imprinted polymer films were prepared by electropolymerizing pyrrole on an electrode surface in the presence of cortisol. Electrochemical over-oxidation of polypyrrole (PPy) was performed for the controlled release of cortisol templates and to create cortisol specific imprinting sites. The sensor exhibited a detection limit of 1 pM L−1 for cortisol.

Fig.2 Schematic representation of the stepwise fabrication of cortisol MIP biosensors. (Manickam, 2016)

A DNA Nanostructure-based Universal Biosensing Platform

The occurrence and prognosis of many complex diseases is associated with the variation of various molecules, including DNA at the genetic level, RNA at the regulatory level, proteins at the functional level and small molecules at the metabolic level. Thus, a single platform is highly desirable to be developed for detecting multilevel biomarkers for early-stage diagnosis. Scientist reported a protocol on DNA-nanostructure-based programmable engineering of the biomolecular recognition interface, providing a universal electrochemical biosensing platform for the ultrasensitive detection of DNA/RNA, proteins, small molecules and whole cells. A comprehensive overview of this protocol is shown in Figure 1.

Fig.3 A tetrahedral DNA-nanostructure-based electrochemical biosensor for multiple molecules detection. (Lin, 2016)

References

1. Han, K.; et al. Electrochemical aptasensors for detection of small molecules, macromolecules, and cells. Reviews in Analytical Chemistry. 2016, 35(4): 201-211.
2. Manickam, P.; et al. A reusable electrochemical biosensor for monitoring of small molecules (cortisol) using molecularly imprinted polymers. Journal of the Electrochemical Society. 2016, 164(2): B54.
3. Lin, M.; et al. Electrochemical detection of nucleic acids, proteins, small molecules and cells using a DNA-nanostructure-based universal biosensing platform. nature protocols. 2016, 11(7): 1244-1263.

For Research Use Only.