ABSTRACT
Retinoblastoma is a malignant tumor of the retina in infants. Conventional therapies are associated to severe side effects and some of them induce secondary tumors. Photodynamic therapy (PDT) thus appears as a promising alternative as it is nonmutagenic and generates minimal side effects. The effectiveness of PDT requires the accumulation of a photosensitizer (PS) in the tumor. However, most porphyrins are hydrophobic and aggregate in aqueous medium. Their incorporation into a nanocarrier may improve their delivery to the cell cytoplasm. In this work, we designed biodegradable liponanoparticles (LNPs) consisting of a poly(d,l)-lactide (PDLLA) nanoparticle coated with a phospholipid (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1,2-dioleoyl-3-trimethylammonium-propane) bilayer. An anticancer drug, beta-lapachone (ß-Lap) and a PS, m-THPC, were co-encapsulated for combined chemo- and PDT because it has been suggested that they may have a synergistic effect based on the activation of ß-Lap by PDT-induced over-expression of the enzyme NQO1. Using dynamic light scattering measurements, cryogenic transmission electron microscopy, and fluorescence confocal microscopy, we selected the appropriate conditions for the encapsulation of the compounds. LNPs were internalized in retinoblastoma cells within few hours. No obvious synergistic effect related to the activation of ß-Lap by PDT was observed. Conversely, the LNPs were cytotoxic at lower doses of the two encapsulated compounds as compared to the single therapies. Analysis of the combinatorial treatment showed that PDT and chemotherapy had an additive effect on the viability of retinoblastoma cells.
Subject(s)
Fatty Acids, Monounsaturated/chemistry , Mesoporphyrins/chemistry , Nanoparticles/chemistry , Naphthoquinones/chemistry , Phosphatidylcholines/chemistry , Photochemotherapy/methods , Polyesters/chemistry , Quaternary Ammonium Compounds/chemistry , Retinoblastoma/drug therapy , Cell Line, Tumor , Cell Survival/drug effects , Cryoelectron Microscopy , Drug Compounding/methods , Drug Delivery Systems/methods , Drug Stability , Dynamic Light Scattering , Humans , Microscopy, Confocal , Photosensitizing Agents/chemistry , Retinoblastoma/pathologyABSTRACT
In specific conditions, co-incubation of polymer nanoparticles and phospholipid vesicles leads to the formation of lipid bilayer coated nanoparticles usable as biocompatible drug delivery systems for co-encapsulation of two drugs. In this work, we focused on the preparation and characterization of liponanoparticles obtained by co-incubation of poly(d,l, lactic acid) (PDLLA) and neutral (POPC) or cationic (POPC/DOTAP) liposomes. The comparison of the behavior of the various studied vesicles co-incubated with nanoparticles highlighted the role of electrostatic interactions. Although the bilayer adsorbed at the surface of polymer nanoparticles was not visible by cryoTEM, zeta-potential measurements and fluorescence confocal microscopy showed evidence of the formation of hybrid nanoparticles in the presence of cationic vesicles. Using silicon dioxide and Langmuir-Schaefer transferred polymer layer-coated surfaces, a thorough analysis of the process of formation of a phospholipid bilayer at the surface of a PDLLA film was performed by combining QCM-D and AFM experiments, taking into account the nature and properties of the support, and the concentration and charge of the lipids. Contrarily to POPC vesicles, cationic ones formed a bilayer on the PDLLA layer in water, but their fast rupture on the soft material did not allow complete nanoparticle surface coverage. This work demonstrates the role of charges and polymer mechanical stiffness in the mechanism and kinetics of formation of PDLLA liponanoparticles in pure water.
