Sterically stabilized liposomes as a platform for salinomycin metal coordination compounds: physicochemical characterization and in vitro evaluation

Sterically stabilized DPPC:CHOL:DSPE-PEG-2000 liposomal formulations of the lipophilic complexes of salinomycin with Na(I), K(I), Mn(II), Co(II), and Ni(II) ions were prepared by film-hydration method at different drug-to-DPPC molar ratios. For the K(I) and Na(I) complexes, optimal loading was established at a drug-to-DPPC molar ratio of 0.5:1, whereas for the Me(II) complexes, it was encountered at 0.1:1. DLS revealed uniform LUV populations (130–160 nm) with monomodal size distribution, further corroborated by AFM. Free and entrapped salinomycinates exhibited cytotoxicity in three human tumor cell lines, whereby the liposomal agents were superior vs. free complexes. DNA-fragmentation and flow cytometric assays showed that the cytotoxicity of free and liposomal salinomycinates is mediated by the induction of apoptosis and G1 arrest. The ability of the carriers to retain the bio-activity of the entrapped cargo gives us reason to conclude that the presented DPPC:CHOL:DSPE- PEG-2000 liposomes are suitable platforms for the salinomycin complexes, needing further evaluation and optimization.