Counterions-mediated gold nanorods-based sensor for label-free detection of poly(ADP-ribose) polymerase-1 activity and its inhibitor

Stable and sensitive detection of poly(ADP-ribose) polymerase-1 (PARP-1) is of great significance in many fields. Herein, a highly simple and sensitive colorimetric biosensor for label-free detection of PARP-1 based on counterions-induced gold nanorods (AuNRs) aggregation is put forward in this work. The specific DNA activated PARP-1 and resulted in the formation of electronegative poly(ADP-ribose) polymer (PAR) on the auto-modified domain of PARP-1 when nicotinamide adenine dinucleotide (NAD+) was used as substrate. Negative charged PAR induced the aggregation of CTAB-coated AuNRs which are employed as the colorimetric probe here, resulted in the obvious decrease of absorbance and the vivid color change. The aggregation process was visually observed by transmission electron microscope (TEM), and dark-field measurements (DFM). By utilizing the change of longitudinal absorption and vivid color variation of AuNRs, PARP-1 can be detected in a linear range of 0.05-1.0 U with a detection limit of 0.006 U (0.261 ng), which is two orders of magnitude improved compared with previously reported colorimetric methods based on AuNPs. This detection method is label-free, visualized and reliable. The used AuNRs probe is stable and their synthesis procedures are simple. The method has been used to detect PARP-1 in ovarian cancer cells A2780, human breast cancer cells SK-BR-3 and MCF-7, obtained with satisfactory results. Besides, it has also been applied to evaluate the PARP-1 inhibitors, detect the change of PARP-1 activity in the presence of various DNA damages.