Encapsulation of methylene blue in nucleoside-lipid-based liposomes: physicochemical characterization and evaluation for photodynamic therapy

Abstract

Methylene blue liposomes (MB-LPs) intended for photodynamic therapy (PDT) of ovarian cancer were formulated with a negatively charged nucleolipid and phosphatidylcholine using the lipidic film technique followed by an extrusion step. MB-LPs were characterized using dynamic light scattering (DLS), zeta potential (ZP), transmission electron microscopy (TEM), colloidal stability, Fourier-transform infra-red spectroscopy (FT-IR), UV-Visible spectroscopy and cellular studies. MB-LPs were spherical nano-objects with sizes obtained by DLS and TEM between 120 and 130 nm. MB-LPs showed a PDI near 0.10, a negative zeta potential near -42 mV and an encapsulation efficiency around 57 %. Characteristic peaks from ionic interactions of nucleolipids encapsulation of methylene blue were confirmed by FT-IR. Colloidal stability of MB-LPs was slightly affected in complex ionic media, sizes, PDI and ZP remained stable for 4 weeks at all storage temperature tested, allowing a potential use for in vitro and in vivo assays. The use of MB-LPs allowed slightly higher PDT activity based on the production of ROS against SKOV-3 ovarian cancer as compared to MB alone, a reduction of MB dark toxicity and a better protection against oxidation-reduction reactions.