New approach to hydrophobic cyanine-type photosensitizer delivery using polymeric oil-cored nanocarriers: hemolytic activity, in vitro cytotoxicity and localization in cancer cells.

We report on encapsulation of cyanine IR-768 in oil-in-water (o/w) microemulsion, i.e. fabrication of templated polymeric nanocapsules as effective nanocarriers for a new generation of photodynamic agents suitable for photodynamic therapy (PDT). Discussed here are nanocapsule imaging, their in vitro biological evaluation, cyanine encapsulation potential, and the cellular localization of cyanine IR-768 delivered in the nanocapsules to MCF-7 cancer cells. Oil-cored poly(n-butyl cyanoacrylate) (PBCA) nanocapsules were prepared by interfacial polymerization in o/w microemulsions formed by the nonionics Tween 80 (polysorbate 80, polyoxyethylene 20 sorbitan monooleate), and Brij 96 (polyoxyethylene 10 oleyl ether). Iso-propyl myristate (IPM), ethyl oleate (EOl), iso-octane (IO), and oleic acid (OA) were used as the oil phases and iso-propanol (IP) and propylene glycol (PG) as the cosurfactants. Such o/w droplets, also containing hydrophobic IR-768 in the oil phase, were applied in the interfacial polymerization of n-butyl cyanoacrylate at 10 degrees C at pH 5.0. The isolated cyanine-loaded nanoparticles were visualized by atomic force microscopy (AFM) and scanning electron microscopy (SEM), which proved their unimodal size distribution and spherical shape, with diameters dependent upon the monomer content and the template type. The entrapment efficiency of cyanine increased with increasing n-butyl cyanoacrylate concentration and varied from 65.7% to 91.7%. The results of in vitro erythrocyte hemolysis and the cell viability of breast cancer MCF-7 cells showed that the PBCA nanocapsules are quite safe carriers of IR-768 in the circulation, having a very low hemolytic potential and being non-toxic to the studied cells. Fluorescence microscopy visualized the cyanine intracellular distribution and, furthermore, demonstrated that PBCA-nanocarriers effectively delivered the IR-768 molecules to the MCF-7 doxorubicin-sensitive and -resistant cell lines. Photoirradiation of the cancer cells with entrapped photosensitizer decreased cell viability, demonstrating that this effect may be utilized in PDT.