Ultrasensitive electrochemical detection of circulating tumor DNA by hollow polymeric nanospheres and dual enzyme assisted target amplification strategy

Detection of tumor biomarker plays a crucial role in the early diagnosis and treatment of cancer. Herein, hollow polymeric nanospheres with a high loading efficiency of ferrocene molecules (Fc-HPNs) were prepared by self-assembly route between polyethylenimine-Fc (PEI-Fc) and poly acrylic acid (PAA) on SiO2 nanoparticles. Using Fc-HPNs as an efficient electrochemical tag and combining dual-enzyme assisted target amplification strategy, an ultrasensitive electrochemical biosensor for the detection of circulating tumor DNA (ctDNA) was developed. The electrochemical signals were greatly enhanced due to the high loading of Fc tags on the hollow polymeric nanospheres and the catalytic effect of ascorbic acid on the reduction reaction of Fc. Furthermore, the use of the magnetic electrode avoided the tedious and complex modification process of the traditional electrode, which made the fabrication of the electrochemical biosensor facile and time-saving. The developed biosensor exhibited a fine linear response to ctDNA concentrations from 10 fM to 10 nM with a low detection limit of 1.6 fM, which shows great potential in early-stage diagnosis and treatment of cancer.