Biodegradable PLGA Microspheres For Controlled Delivery And Cell Biology Research Of PTHrP1-34

Background and Objective:PTH1-34-related peptide (PTHrP1-34) is a with PTH (1-34) have manyof the same or similar to the material in the gene encoding the polypeptide,molecular structure, receptor structure and signal transduction, found bythe malignancy in the study hypercalcemia process mechanism. Recentstudies show that PTHrP could significantly increase the bone mass andbiomechanical strength osteoporosis rat,having the same immatureosteoblasts or promote the osteoblast-like cell proliferationwith PTH.Dental implant primary stability of key decision factor is the quality andvolume of alveolar residual ridge, and clinical studies have shown thatsystemic osteoporosis on alveolar bone mineral content and residualalveolar volume has significant effect, therefore, PTHrP has increased dueto the peri-implant bone density, improve initial implant stability, accelerateearly osseointegration of the implant into the bone, such as outstandingrole in the field of oral implantology has broad application prospects.However, PTHrP different mode of administration will have differenteffects on bone tissues, intermittent administration of low doses canpromote bone anabolic effect, increasing bone volume, bone structure to improve, but large doses cause osteoclast PTHrP extensive cellactivation, so that the function of osteoblasts is inhibited. Further, PTHrPthere short half easily denatured expensive defects, so control thedevelopment of sustained release carrier is very necessary to improve itsbioavailability, effective carrier is introduced into the polymer solution.Biodegradable polymer materials because of its good biocompatibility,biodegradability, absorbability, can be processed into various forms ofimplantable biomedical materials and other characteristics can be used asdrug carriers has been widely studied.Polyglycolide-lactide (PLGA) is abiocompatible biodegradable material, the most widely used, most studied,in order to polyglycolide-reported lactide microspheres wrapped manyprotein drugs double emulsion method is one of the most commonly usedmethod. Therefore, the development of PLGA as a carrier so as to controlthe release rate of the sustained release time and increase thebioavailability of the purpose of great significance.Method:In this study, PLGA microspheres were prepared by awater-in-oil-in-water (W1/O/W2) double emulsion solvent evaporation andPTHrP1-34was encapsulated to the microspheres by a technique withgood sphericity and high efficiency. The micrographs of polyestermicrospheres were evaluated by scanning electron microscope (SEM). BySEM observation of PTHrP1-34loaded microspheres surface morphology; determination of PTHrP1-34loaded microspheres by NaOH-SDS methodof encapsulation rate and drug content; PTHrP1-34loaded microspheresexhibited a slow release behavior, which was accord with ourexpection.The Effect of PTHrP1-34loaded microspheres onpre-osteoblastic proliferation was studied via cell proliferation evaluationexperiments. Alkaline phosphatase (ALP) quantification experiment wasalso performed to investigate the influence of differentiation.Results:1、By NMR and FTIR, we can determine the repeating unit of lactic acidand glycolic acid units is about85:15of PLGA. The molecular weight ofPLGA was measured by GPC, Mn=85000, PDI=1.26. The micrographsof polyester microspheres were evaluated by scanning electron microscope(SEM). The polyester microspheres had a good spherical shape. PLGAmicrospheres have an average particle size of about8μm. Theencapsulation rate and drug content of PTHrP1-34loaded PLGAmicrospheres was0.84%and72.3%, by NaOH-SDS method.. As part ofPTHrP1-34package that PLGA microspheres surface, on the first daythere is a clear burst, the next day began the slow release. PTHrP1-34loaded PLGA microspheres exhibited a slow release behavior for about25day under physiological temperature, which was accord with our expection.2、cytologic evaluation of PTHrP1-34microspheres：By MTT assay and alkaline phosphatase quantitative detection, the concentration of the intermittent administered PTHrP1-34to MC3T3whichpromoting the most obviously cell proliferation was1×10-9mol/L.By MTT assay and alkaline phosphatase quantitative detection, when thetotal concentration of PTHrP1-34loaded by PLGA microspheres is1×10-9mol/L, MC3T3-E1exhibited significantly effects promoting proliferationand differentiation of cells（P<0.05）Conclusion:1、PTHrP1-34loaded PLGA microspheres exhibited a slow releasebehavior for about25day under physiological temperature, which wasaccord with our expection.2、 The intermittent application of PTHrP1-34can promote theproliferation and differentiation of osteoblasts, and the most appropriateconcentration of PTHrP1-34is10-9mol/L.3、 Loading PTHrP1-34, the PLGA microsphereslocal sustainedreleasing effect can significantly promote the proliferation and differentiationof MC3T3-E1. It was prompted that the PTHrP1-34loaded PLGAmicrospheres as a drug delivery system has a good potential application inthe field of Oral Implantology, providing possible solutions to solve clinicalproblems of insufficient amount of peri-implant bone.