Cisplatin Encapsulation Generates Morphologically Different Multicompartments in the Internal Nanostructures of Nonlamellar Liquid-Crystalline Self-Assemblies

Cisplatin (cis-diamminedichloroplatinum(II)) is among the most potent cytotoxic agents used in cancer chemotherapy. The encapsulation of cisplatin in lipid-based drug carriers has been challenging owing to its low solubility in both aqueous and lipid phases. Here, we investigated cisplatin encapsulation in nonlamellar liquid-crystalline (LC) nanodispersions formed from a ternary mixture of phytantriol (PHYT), vitamin E (Vit E), and an anionic phospholipid [either phosphatidylglycerol (DSPG) or phosphatidylserine (DPPS)]. We show an increase in cisplatin encapsulation efficiency (EE) in nanodispersions containing 1.5-4 wt % phospholipid. The EE was highest in DPPS-containing nanodispersions (53-98%) compared to DSPG-containing counterparts (25-40%) under similar experimental conditions. Through structural and morphological characterizations involving synchrotron small-angle X-ray scattering and cryogenic transmission electron microscopy, we further snow that varying the phospholipid content of cisplatin-tree nanodispersions triggers an internal phase transition from a neat hexagonal (H-2) phase to a biphasic phase (internal H-2 phase coexisting with the lamellar (L-alpha) phase). However, cisplatin encapsulation in both DPPS- and DSPG-containing nanodispersions generates the coexistence of morphologically different multicompartments in the internal nanostructures comprising vesicles as a core, enveloped by an inverted-type surface bicontinuous cubic Im3m (primitive, Q(II)(p)) phase or H-2 phase. We discuss the biophysical basis of these drug-induced morphological alterations and provide insights into the potential development of inverted-type LC nanodispersions for cisplatin delivery.