Dual atom transfer radical polymerization for ultrasensitive electrochemical DNA detection

Atom transfer radical polymerization as a form of controlled/living radical polymerization is particularly attractive. In this work, dual atom transfer radical polymerization (ATRP) is reported for ultrasensitive DNA detection. Firstly, a peptide nucleic acid (PNA) modified with a thiol group was self-assembled on an electrode surface to capture target DNA (TDNA). The initiator of the first ATRP (ATRP-1), α-bromoisobutyric acid (BIBA), was linked to forming PNA/DNA heteroduplexes via coordination of Zr⁴⁺. The polymer chain formed by the monomer of ATRP-1 (2-(2-bromoisobutyryloxy) ethyl methacrylate, BIEM) was also one of initiators of the second ATRP (eATRP-2). The other initiator of eATRP-2 was additional BIBA. ATRP-1 involves activator regeneration by electron transfer (ARGET) ATRP, regulated via excess reducing agent. eATRP-2 is electrochemically mediated ATRP which can control the polymerization via an appropriate applied potential. Compared with one ATRP, more monomers of eATRP-2 modified with ferrocene are attached to electrode surface. Under optimal conditions, this dual ATRP strategy provides a low limit of detection (25 aM, ~150 molecules) with satisfactory selectivity and stability. Importantly, this strategy presents a useful prospect for the field of biomolecule detection.