DNA-based label-free electrochemical biosensors: From principles to applications

As a kind of excellent biomaterials, deoxyribonucleic acids (DNAs) have been employed to build a variety of biosensors via the interactions between DNAs and biomolecules or chemical compounds. The DNA-based electrochemical biosensors with the advantages of easy operation, rapid response and low cost have been widely used in biochemical analysis with high sensitivity and selectivity. However, most of the DNA-based electrochemical biosensors require the labeling of electroactive molecules or nanomaterials on DNAs as signal read-out elements, which thus inevitably suffer from complicated operation and expensive cost. Label-free strategies are alternatives for DNA-based electrochemical biosensors without additional assay reagents and tedious procedures. Because of the merits of simplicity and low cost, DNA-based label-free electrochemical biosensors have attracted tremendous attention from researchers as a promising analytical technology. In this review, the principles and applications of DNA-based label-free electrochemical biosensing systems including heterogeneous and homogeneous modes with various amplification strategies have been introduced and summarized systematically. Furthermore, the present challenges and further perspectives of the DNA-based label-free electrochemical biosensors are highlighted.