2022, Vol. 26 ›› Issue (10): 1566-1573

Abstract:BACKGROUND: The strong hydrophobicity and lack of targeting of commonly used photosensitizers seriously limit the therapeutic effect of photodynamic therapy. Although nanodrug carriers are capable of delivering photosensitizers to tumor sites, the tumor hypoxia microenvironment seriously weakens the efficiency of photodynamic therapy. Furthermore, the photodynamic therapy-induced immune response would also be limited due to the tumor immunosuppressive microenvironment.  

OBJECTIVE: To synthesize the targeted nanoparticles and evaluate their physicochemical properties, the efficiency of enhancing photodynamic therapy and the feasibility of combined immunotherapy.
METHODS: Amphiphilic functionalized polylysine and NLG8189 dimer was synthesized by amino acid closed-loop reaction, ring-opening polymerization and condensation reaction. The core of nanoparticles (Pe6D) was prepared by the dialysis method, followed by the perfluoro hexane loading and hyaluronic acid wrapping to obtain the composite HPe6DF nanoparticles. Thereafter, the particle size, zeta potential, surface morphology, enzyme responsiveness, oxygen loading efficiency, and reactive oxygen species production of HPe6DF were studied. Mouse breast cancer cells 4T1 was served as in vitro cell model for the biological evaluation of HPe6DF nanoparticles, including cellular uptake, reactive oxygen species production, cytotoxicity, apoptosis, cell immunogenic death and inhibition of indoleamine-2,3-dioxygenase enzymes.
RESULTS AND CONCLUSION: (1) Successfully prepared HPe6DF nanoparticles present uniform spherical morphology with a hydration diameter of 150 nm and the zeta potential is around -20 mV. Moreover, the composite nanoparticles have a certain hyaluronidase responsiveness, good oxygen loading ability, and active oxygen production ability. (2) The results of the cell compound culture experiment showed that HPe6DF nanoparticles accumulated in the cell in a time-dependent manner. Under the same other conditions, the fluorescence intensity of the hyaluronic acid pre-incubation group was significantly weaker than that of the non-hyaluronic acid pre-incubation group, proving that HPe6DF nanoparticles could enter the cell effectively through CD44 mediation. Under light conditions, HPe6DF nanoparticles had good reactive oxygen species production ability in cells, could promote cell apoptosis efficiently, and further induce immunogenic death, and can effectively inhibit the activity of indoleamine-2,3-dioxygenase in tumor cells. (3) The results show that HPe6DF nanoparticles can not only improve the photodynamic efficiency, enhance the immunogenicity of tumor cells, but also relieve the immunosuppressive microenvironment of the tumor site.

Key words:nanoparticles, photodynamic therapy, relief hypoxia, immunotherapy, indoleamine-2,3-dioxygenase, chlorin e6, reactive oxygen species, apoptosis, immunogenic death