Magnetic bead-based electrochemical and colorimetric methods for the detection of poly(ADP-ribose) polymerase-1 with boronic acid derivatives as the signal probes

Poly(ADP-ribose) polymerase-1 (PARP-1), as a highly conserved nuclear enzyme, can catalyze the transfer of multiple ADP-ribose units from β-nicotinamide adenine dinucleotide (NAD+) to substrate proteins, including PARP-1 itself. In this work, two boronic acid derivatives, ferroceneboronic acid (FcBA) and 4-mercaptophenylboronic acid (MPBA) were used as the signal probes for electrochemical and colorimetric detection of PARP-1, respectively. The detection platform was constructed by modification of double-stranded DNA (dsDNA) on the surface of magnetic beads (MBs). Once PARP-1 was captured by the MB-dsDNA, auto-PARylation was initiated and the PAR products consisting of abundant ribose units were covalently bound to FcBA or MPBA through the formation of boronate ester covalent bonds. Sequestration of FcBA or MPBA by the PAR-covered MBs led to the decrease in the electrochemical signal of FcBA or preventing the MPBA-triggered aggregation of gold nanoparticle indicators. The change of oxidation current or adsorption intensity (color) was dependent upon the concentration and activity of PARP-1. A wide linear range of 0.1 ∼ 50 U was obtained for the electrochemical or colorimetric assays. The methods have been used to evaluate the inhibition efficiency and monitor the PARP-1 activity in living and apoptotic cancer cells.