A quadruplex-DNA binder functionalised with a SPECT probe for in vivo imaging

Guanine-rich sequences of DNA can fold into intramolecular tetra-helical assemblies known as G-quadruplexes (G4). Their formation in vivo has been associated to a range of biological functions and therefore they have been identified as potential drug targets. Consequently, a broad range of small molecules have been developed to target quadruplexes. However, to date, there is very limited information of the biodistribution of quadruplex binders in whole organisms. Here, we report the functionalisation of a well-established G4 DNA binder (based on a square planar platinum(II)-salphen complex) with two different radiolabelled complexes. An 111In-conjugate was successfully used to assess its in vivo distribution in a mouse tumour model using single-photon emission computed tomography (SPECT) imaging. These studies have shown the overall biodistribution of the G4 DNA binder highlighting its accumulation in the tumour.