Impedance technology reveals correlations between cytotoxicity and lipophilicity of mono and bimetallic phosphine complexes

Label free impedance technology enables the monitoring of cell response patterns post treatment with drugs or other chemicals. Using this technology, a correlation between the lipophilicity of metal complexes and the degree of cytotoxicity was observed. Au(L1)Cl (1), AuPd(L1)(SC₄H₈)Cl₃ (1a) and Au(L2)Cl (2) [L1 = diphenylphosphino-2-pyridine; L2 = 2-(2-(diphenylphosphino)ethyl)-pyridine] were synthesised, in silico drug-likeness and structure-activity relationship monitored using impedance technology. Dose dependent changes in cytotoxicity were observed for the metal complexes resulting in IC_50s of 12.5 ± 2.5, 18.3 ± 8.3 and 16.9 ± 0.5 μM for 1, 1a and 2 respectively in an endpoint assay. When a real time impedance assay was used, dose-dependent responses depicting patterns that suggested slower uptake (at a toxic 20 μM) and faster recovery of the cells (at the less toxic 10 μM) of the bimetallic complex (1a) compared to the monometallic complexes (1 and 2) was observed. These data agreed with the ADMET findings of lower aqueous solubility of 1a and non-ideal lipophilicity (AlogP98 of 6.55) over more water soluble 1 and 2 with ideal lipophilicity (4.91 and 5.03 respectively) values. The additional coordination of a Pd atom to the nitrogen atom of a pyridine ring, the sulfur atom of a tetrahydrothiophene moiety and two chlorine atoms in 1a could be contributing to the observed differences when compared to the monometallic complexes. This report presents impedance technology as a means of correlating drug-likeness of lipophilic phosphine complexes containing similar backbone structures and could prove valuable in filtering drug-like compounds in a drug discovery project.