Interactions of Cationic Diruthenium Trithiolato Complexes With Phospholipid Membranes Studied by NMR Spectroscopy
2020
To apprehend the possible mechanisms involved in the cellular uptake and
the membrane interactions of cytotoxic dinuclear p-cymene trithiolato ruthenium(II)
complexes, the interactions of the complexes [(ɳ6-p-MeC6H4Pri)2Ru2(R1)2(R2)]+ (R1 = R2
= SC6H4-m-Pri :1; R1 = SC6H4-p-OMe, R2 = SC6H4-p-OH :2; R1 = SCH2C6H4-p-OMe, R2
= SC6H4-p-OH :3) with 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) vesicles and
1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) micelles were studied using
nuclear magnetic resonance (NMR) spectroscopy. 1H, NOE, DOSY, and T1 and T2
relaxation data provided information on interactions between the complexes and the
model membranes and on the submolecular localization of the complexes at the
membrane interface. The results suggest that (a) interaction takes place without new
covalent adduct formation, (b) the cationic diruthenium complexes interact with DOPC
head groups most likely involving electrostatic interactions while remaining structurally
unchanged, (c) the changes indicating interactions are more pronounced for the most
lipophilic complex 1, (d) the diruthenium complexes remain at the exterior vesicle surface
and unlikely insert between the phospholipid chains. The complexes also interact with
micellar/free DHPC and seem to induce micellization or aggregation in sub-CMC
solutions. Our study suggests a high affinity of the Ru complexes for the membrane
surface that likely plays a key role in cellular uptake and possibly also in redistribution to
mitochondria.
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