Preparation and characterization of mTHPC-loaded solid lipid nanoparticles for photodynamic therapy

•mTHPC molecules were efficiently encapsulated into the lipid core of LNP.•No alteration of the colloidal properties of the carrier and photophysical properties.•1O2 can be generated under light irradiation.•1O2 can diffuse through the nanoparticle shell.•Lipid concentration dependent cytotoxic properties were observed.

Among various attempts to enhance the therapeutic efficacy of photodynamic therapy (PDT), the specific delivery of photosensitizer (PS) in the tumor tissue is expected to improve its clinical applications. 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-(tetrahydroxyphenyl) chlorin (mTHPC) is one of the most potent photoactive compounds for clinical use. We demonstrated that 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. Photophysical and physico-chemical properties of mTHPC-loaded LNP were assessed as well as absorption spectra and singlet oxygen emission, colloidal stability, particle size and zeta potential. The photocytotoxicity of selected mTHPC-loaded solid LNP was demonstrated on MCF-7 cells under irradiation at 652 nm with a range of light fluence from 1.0 to 10 J/cm2. All physico-chemical, photophysical and biological results allow us to conclude that solid LNP appear as a very promising nano-mTHPC delivery system for PDT.