Rational design of an acridine-derived click chemistry-based artificial metallo-nuclease

Artificial metallo-nucleases (AMNs) are metal complexes capable of cleaving nucleic acids and represent a promising therapeutic class. We recently established that copper(i)-catalysed azide-alkyne cycloaddition (CuAAC) click chemistry offers a versatile approach for building new minor groove targeting AMNs, epitomised by the tri-click (TC) series; here, three bidentate chelation sites comprising the N-triazole donor from the CuAAC reaction, together with the 'clicked' donor group, provide new ligand architectures that coordinate up to three bioactive copper(ii) metal ions. Although the TC series are promising scaffolds, no route has yet been established to direct, or enhance their DNA recognition properties. Herein, we report a new method for hybridising click chemistry-based AMNs with acridine, a potent DNA intercalating agent. Motivation for generating this conjugate stems from the opportunity to combine multimodal DNA binding properties, namely, DNA intercalation via the acridine unit, and minor groove recognition and cleavage by the nuclease component. Two sites of the original TC scaffold were retained for copper chelation and DNA cleavage, thereby producing a di-click-pyridine (DC-Py) unit, while the third site was repurposed for conjugation to the acridine (A) group. The resultant hybrid (DC-PyA) was then coordinated with copper(ii) ions (Cu₂-DC-PyA) and the downstream direct and indirect DNA recognition properties and cleavage properties were examined, and activity resembling threading DNA intercalation was observed.