Synthesis Of PH-responsive Bisphosphonate Nanoparticles And Its Treatment For Osteosarcoma

Objective:Bisphosphonates(BPs)are clinically used in the treatment of tumor-induced osteolysis,hypercalcemia and osteoporosis.Because of the P-C-P group,BPs bind closely to hydroxyapatite,decreasing the activity of osteoclasts and thus inhibiting bone resorption.In recent years,multiple studies show BPs represent potent anti-tumor effects in multiple mechanisms and prevent distant metastasis.However,due to renal excretion and rapid absorption in bone,BPs are rapidly eliminated from plasma upon intravenous administration.The characteristic of BPs results in poor aggregation efficiency in tumor,which limits therapeutic effectiveness.When BPs combine with metal ions such as Ca2+,Meanwhile,phosphoric acid-metal group has abundant porous structure on the surface,which has the potential to load a variety of small-molecule drugs.The BP-metal complexes could be pH-sensitive which enable them to dissolve in TME(tumor microenvironment)and release drugs loaded on the surface.The purpose of this study is to synthesise a new nanoparticle containing BP-metal complexes via a simple and mild method.Nanoparticles protect BPs from being absorbed and excreted in vivo,and accumulate in tumor through EPR effect.The loaded drugs eventually target to osteosarcoma together with BPs in the acid environment of tumor.Methods:Due to the hydrophobicity of BP complex,organic reagents were used in most researches to obtain nanosize particles.However,it not only decreased the synthesis efficiency,but also produced a large amount of synthetic waste liquid.Considering the importance of environmental protection,this article presents a simple method:zoledronic acid,bovine serum albmin(BSA)and Ca2+ were mixed in water.BSA-CaZol were obtained successfully after reacting via different conditions,loaded with methotrexate(MTX)and CpG DNA(CpG).The nanoparticles were characterized using DLS,TEM and U.V.spectrum.The pH responsiveness,targeting efficiency,toxicity and therapeutic effects of the nanoparticles in vitro/vivo were evaluated in the following experiments.Results:We developed the BSA-CaZol nanoparticles with stable and controllable size(≈80nm).The nanoparticles showed high pH-sensitive drug release properties.The cumulative release of MTX in pH=6.0 was 2.93 times that in pH=7.4,which performed enhanced treatment efficiency for K7M2 cell and orthotopic models.The result of IVIS shows effective targeting property of nanoparticles.Furthermore,the nanoparticles demonstrated enhanced immunostimulation both in vitro and in vivo.Conclusion:BPs have great potential in clinical application.However the short half-life and strong bone-binding properties limit BPs as anti-tumor drugs.In this study,BPs were nanalized and loaded with MTX and CpG,targeting the tumor through EPR effect.Finally,drugs released so as to achieve the purpose of collaborative therapy of osteosarcoma.