An electrochemical strategy with molecular beacon and hemin/G-quadruplex for the detection of Clostridium perfringens DNA on screen-printed electrodes

C. perfringens is a prevalent pathogen that causes infectious diseases. It becomes viable easily but often cannot be cultured and thus escapes detection. Here, we describe an electrochemical strategy based on molecular beacon (MB), streptavidin (SA), and hemin/G-quadruplex/Fe3O4 nanocomposites. Initially, the MB forms a stable hairpin, which blocks the binding capability of the SA aptamer. After incubating with target DNA, the hairpin opens and the SA aptamer is reactivated to capture the SA/alcohol dehydrogenase (ADH)/Fe3O4 nanocomposites. Through a "sandwich" reaction, the hemin/G-quadruplex is captured on the electrode surface, and the electrochemical signal of DPV is thus obtained. Our results suggest that the use of AuNPs/graphene dramatically enlarges the surface area and enhances the immobilisation of the capture probe (MB). The combination of the Fe3O4 nanocomposite with hemin/G-quadruplex enabled the progressive amplification of the electrochemical signal. It also showed satisfying stability, reproducibility and good specificity. Compared with PCR, there were no significant differences in the recovery and regression of concentration. Thus, this SPE strategy is a promising alternative for detecting C. perfringens without bacterial culture and DNA amplification in point of care testing (POCT).