ABSTRACT
The therapeutic effect of tumor photodynamic therapy is severely limited by the hypoxic tumor microenvironment. Inhibiting tumor celloxygen consumption is a more effective way than increasing its oxygen supply to overcome the tumor hypoxia and enhance photodynamic therapy. To carry out this strategy, the supramolecular nanoparticles VER-ATO-SMN loaded with photosensitizer verteporfin (VER), oxygen-consuming inhibitor atovaquone (ATO), and stabilizer polyvinylpyrrolidone (PVP)-K30 were prepared by the nanoprecipitation method, and the optimal prescription was screened and optimized by single factor experiments. The results showed that the optimal prescription for VER-ATO-SMN was ATO∶VER (w/w) = 1∶1, PVP-K30 = 100 mg, N,N-dimethylformamide∶water (v/v) = 1∶10. The morphology, particle size, particle dispersion index and encapsulation efficiency of supramolecular nanoparticles were characterized. The VER-ATO-SMN showed a spherical morphology and was well dispersed. The hydrodynamic size of VER-ATO-SMN was 101.21 ± 4.30 nm as determined by dynamic light scattering (DLS). The encapsulation efficiencies of VER and ATO in VER-ATO-SMN prepared with the optimal prescription were 70.86% and 77.52%, respectively. The VER-ATO-SMN exhibited good laser stability and also showed high stability in conditions which simulated the physiological solution. Compared with free VER and VER liposome, VER-ATO-SMN performed enhanced therapeutic effect at the cell level. The mechanism was that VER-ATO-SMN could effectively incorporate into cells and improving the intracellular oxygen concentration by reducing the oxygen consumption of tumor cells could increase the amount of reactive oxygen species generated by VER mediated photodynamic therapy. The in vivo anticancer efficacy results of tumor-bearing mice suggested that VER-ATO-SMN could effectively inhibit the tumor growth or even completely eliminate the tumor. All animal experiments were performed in line with national regulations and approved by the Animal Experiments Ethical Committee of 900 Hospital of the Joint Logistics Team.
ABSTRACT
To improve the efficacy of 5-aminolevulinic acid (5-ALA)-mediated photodynamic therapy (PDT), a fluorocarbon microemulsion-based gel (FMBG) loaded with both 5-ALA and carbon dioxide (CO2) was prepared in this study. Its physical and chemical properties such as particle size, zeta potential, morphology, pH value and viscosity were characterized. Acid-base titration experiment was used to determine the CO2 loading, a fluorescence derivatization method was established to determine the content of 5-ALA, and the confocal laser scanning microscope and Franz diffusion cell method were carried out to investigate its transdermal ability. Through the laser speckle contrast imaging, the CO2-affected blood flow perfusion of skin was measured. Finally, the skin irritation test was tested by hematoxylin-eosin staining (H&E) method. These results showed that the prepared FMBG was a milky white gel, with an average particle size of 202.4 nm, a zeta potential of -25.3 mV, a pH of 6.0, and a viscosity of 1 062.0 mPa·s. It can be stored stably for seven days at room temperature. The 5-ALA content of FMBG was measured to be approximately equal to 20% (w/w). At room temperature and normal pressure, the CO2 loading content of FMBG was 5.016 mg·L-1, which was 1.5 times as much as that of water. The transdermal absorption experiment and blood perfusion results showed that the FMBG can effectively enable the transdermal delivery of 5-ALA and CO2, and significantly increased the blood perfusion of skin. H&E staining results indicated that FMBG had negligible skin irritation (all animal tests were approved by the Ethics Committee of 900 Hospital of the Joint Logistics Team). In this study, a safe and stable FMBG loaded with both 5-ALA and CO2 was successfully prepared. It was suitable for transdermal application, having the potential of enhancing the efficacy of 5-ALA-mediated PDT.