In vitro imaging of Raji B cells with fluorescent and biocompatible lipidic cubosomes

• A fluorescent dye was encapsulated in monoolein-based cubosomes stabilized by Pluronic F127 or a polyphosphoester (PPE). • The encapsulation did not affect the size, structure and morphology of the samples. • PPE-cubosomes were more colloidally stable than the F127 ones in cell medium . • The different stabilizers did not affect the internalization and localization of the cubosomes inside Raji B cells. • PPE-cubosomes are less cytotoxic against Raji B cells. The ability to image specific areas of the body is crucial for developing novel, non-invasive medical approaches. Nanocarriers designed for this purpose should have minimal cytotoxicity to accurately reveal internalization mechanism while also allowing for tunable localization within the cells through compositional adjustments. Cubosomes have been widely studied as carriers for imaging agents. However, the block copolymers traditionally used as steric stabilizers, namely Pluronics, raise biocompatibility concerns. Our group already demonstrated that polyphosphoester (PPE)-based stabilizers enhance the biocompatibility of monoolein compared to conventional block copolymers. Here, we further explored the colloidal and biological properties of PPE-stabilized cubosomes relative to conventional cubosomes formulated with Pluronic F127. For this purpose, we encapsulated a fluorescent dye suitable for in vitro imaging. Physicochemical characterization confirmed that both formulations retain their structure and morphology after the dye encapsulation, but the colloidal stability of the PPE-stabilized cubosomes was higher in a biological medium. Moreover, cytotoxicity assessment on Raji B cells, a model of white blood cells, demonstrated that the new formulation offers improved biocompatibility. Importantly, this study also revealed that the internalization process remains unaffected by the choice of stabilizer, with both types of cubosomes distributing homogenously within the Raji B cells.