Tunable Cytotoxicity and Selectivity of Phosphonium Ionic Liquid with Aniline Blue Dye

Ionic liquids are an interesting class of materials that have recently been utilized as chemotherapeutic agents in cancer therapy. Aniline blue, a commonly used biological staining agent, was used as a counter ion to trihexyltetradecylphosphonium, a known cytotoxic cation. A facile, single step ion exchange reaction was performed to synthesize a fluorescent ionic liquid, trihexyltetradecylphosphonium aniline blue. Aqueous nanoparticles of this hydrophobic ionic liquid were prepared using reprecipitationmethod. The newly synthesized ionic liquid and subsequent nanoparticles were characterized using various spectroscopic techniques. Transmission electron microscopy and zeta potential measurements were performed to characterize the nanoparticles' morphology and surface charge. The photophysical properties of the nanoparticles and the parent aniline blue compound were studied using absorption and fluorescence spectroscopy. Cell viability studies were conducted to investigate the cytotoxicity of the newly developed trihexyltetradecylphosphonium aniline blue nanoparticles in human breast epithelial cancer cell line (MCF-7) and its corresponding normal epithelial cell line (MCF-10A) in vitro. The results revealed that the synthesized ionic nanomedicines were more cytotoxic (lower IC₅₀) than the parent chemotherapeutic compound in MCF-7 cells. Nanoparticles of the synthesized ionic liquid were also shown to be more stable in both aqueous and cellular media and more selective than parent compounds towards cancer cells.