Structure Impact on Photodynamic Therapy and Cellular Contrasting Functions of Colloids Constructed from Dimeric Au(I) Complex and Hexamolybdenum Clusters

Electrostatically driven self-assembly of [AuL] (L is cyclic PNNP ligand) with [{MoI}(L')] (L' = I, CHCOO) in aqueous solutions is introduced as facile route for combination of therapeutic and cellular contrasting functions within heterometallic colloids (Mo-Au). The nature of L' affects the size and aggregation behavior of crystalline Mo-Au aggregates, which in turn affect the luminescence of the cluster units incorporated into Mo-Au colloids. The spin trap facilitated electron spin resonance spectroscopy technique indicates that the level of ROS generated by Mo-Au colloids is also affected by their size. Both (L' = I, CHCOO) Mo-Au colloids undergo cell internalization, which is enhanced by their assembly with poly-DL-lysine (PL) for L' = CHCOO, but remains unchanged for L' = I. The colloids PL-Mo-Au (L' = CHCOO) are visualized as huge crystalline aggregates both outside and inside the cell cytoplasm by confocal microscopy imaging of the incubated cells, while the smaller sized (30-50 nm) PL-Mo-Au (L' = I) efficiently stain the cell nuclei. Quantitative colocalization analysis of PL-Mo-Au (L' = CHCOO) in lysosomal compartments points to the fast endo-lysosomal escape of the colloids followed by their intracellular aggregation. The cytotoxicity of PL-Mo-Au differs from that of Mo and Au blocks, predominantly acting through apoptotic pathway. The photodynamic therapeutic effect of the PL-Mo-Au colloids on the cancer cells correlates with their intracellular trafficking and aggregation.