Preparation, characterization, and cellular studies of photosensitizer-loaded lipid nanoparticles for photodynamic therapy

PhotoDynamic Therapy (PDT) has been established as a potent and less invasive treatment for different kinds of cancer. Among various attempts to enhance the therapeutics efficacy of PDT, the specific delivery of the PhotoSensitizer (PS) in the tumor is expected to increase its clinical applications, since unwanted accumulation, especially in the skin, impairs the patients' quality of life (prolonged cutaneous photosensitivity). The aim of this study was to engineer Lipid Nanoparticles (LNP) with different sizes and various PS contents, using simple, solvent-free and easily scale up manufacturing processes. Meso-tetra (hydroxyphenyl) chlorin (mTHPC) is one of the most potent photoactive compounds for clinical use and it has been successfully applied in the treatment of various indications, such as the head and neck, prostate and pancreatic cancers. Here, a derivative of mTHPC was efficiently incorporated into the lipid core of LNP, leading to a large range of stable and reproducible mTHPC-loaded LNP with narrow size distribution. The photophysical and photochemical properties of mTHPC-loaded LNP were studied by measuring absorbance and fluorescence spectra, colloidal stability, particle size and zeta potential, as well as singlet oxygen luminescence. The photocytotoxicity of three selected mTHPC-loaded LNP (25 nm, 45 nm and 95 nm of diameter, respectively) was evaluated on MCF-7 cells, in comparison to free mTHPC, under irradiation at 652 nm with a range of light fluence from 1 to 5 J/cm2. All the physico-chemical, photophysical and biological measurements allow us to conclude that LNP is a promising nano-drug delivery system for PDT.