Magnetic Nanobeads and De Novo Growth of Electroactive Polymers for Ultrasensitive microRNA Detection at the Cellular Level

Detection of biomarkers at the cellular level can provide more accurate and comprehensive information that is important for early diagnosis of diseases and evaluation of new drugs. However, the interference of a large number of components in cells and the requirement of high sensitivity bring great challenges for their detection. Herein, a robust and enzyme-free electrochemical platform was proposed for microRNA-21 (miRNA-21) detection by integrating the efficient separation of magnetic nanobeads (MBs) with the multisignal amplification of strand displacement amplification (SDA) and electrochemically mediated atom transfer radical polymerization (eATRP). The eATRP is capable of de novo growth of a number of electroactive polymers on the electrode surface for signal amplification. Compared to simple hybridization, SDA and eATRP can enhance the signals by similar to 35-fold, achieving high signal-to-noise ratio for low-abundant target detection. Owing to their superparamagnetism and strong magnetic response ability, MBs endow the method with excellent specificity and anti-interference ability to detect miRNA-21 in cells. Using MBs as capture carriers, SDA and eATRP for signal amplification, and gold nanoflower (AuNF)-modified electrodes as working electrodes, as low as 0.32 aM miRNA-21 was detected. Furthermore, the successful detection of miRNA-21 in cells indicated the great prospect of this method in the early diagnosis of cancers, life science research, and single-entity electrochemical detection.

Automated summary

This study introduces a novel electrochemical platform for miRNA-21 detection, integrating the separation capability of magnetic nanobeads with strand displacement amplification and electrochemically mediated atom transfer radical polymerization for multisignal amplification, enabling high sensitivity detection of low-abundant targets.