| Poly(lactic acid)(PLA)is a kind of polymer material with high mechanical strength,easy processing,good biodegradation and biocompatibility.For these reasons,PLA is widely used in tissue engineering,drug delivery,surgical suture and orthopedic repair.It is a biomedical material approved by FDA.Due to the existence of asymmetric carbon atoms and optical activity,PLA can be divided into Poly(D-lactic acid)(PDLA),Poly(L-lactic acid)(PLLA),racemic PLA(PDLLA),and Meso-PLA.It is generally believed that the biocompatibility of L-lactic acid is better than D-lactic acid because of the lactic acid in human body is L-lactic acid.Therefore,most of the previous studies on PLA are based on PLLA,and there are few studies on the application of PDLA and PDLLA in biomedical materials.Based on this,we prepared PLA nanoparticles and microspheres with different chiralities.By chemically characterizing them and cell polarization of macrophages in vitro,secretion of inflammatory factors,maturation of dendritic cells,and factor secretion,research on animal skin tissue inflammatory factor expression,collagen fiber regeneration and other aspects to verify the different biological functions caused by chiral materials.Details as follows:(1)Three kinds of PLA with different chiralities,PDLA PLLA,and PDLLA were synthesized by ring opening polymerization of lactide.The structure and molecular weight of the polymers were analyzed by NMR hydrogen spectrum(~1H NMR),Fourier infrared spectrum(FT-IR),circular dichroism spectrum(CD)and gel permeation chromatography(GPC).Three kinds of PLA nanoparticles were prepared by nano-precipitation method.The particle size and morphology of the nanoparticles were characterized by dynamic light scattering(DLS)and transmission electron microscopy(TEM).The nanoparticles were co-cultured with commercial macrophages(RAW264.7),primary peritoneal macrophages(macrophage?)and mouse bone marrow-derived dendritic cells(BMDC).The secretory factors were quantitatively analyzed by enzyme-linked immunosorbent assay(ELISA),the maturation of BMDC was determined by flow cytometry,and the related mechanism of the immune effect of PLA nanoparticles was explored.The results showed that PDLA nanoparticles could induce more inflammatory reaction,stimulate cells to produce more inflammatory factors,promote macrophages to differentiate into M1 type,and induce BMDC to mature in more proportion,which was through the mechanism of action of Toll receptor 4.Therefore,PDLA can be used as an adjuvant of immune activation to obtain an ideal immune response.(2)Three kinds of PLA materials were prepared into microsphere by emulsion solvent evaporation method.Preparation of microsphere with different particle sizes by controlling relevant conditions.The diameter and morphology of the microsphere were characterized by scanning electron microscopy(SEM).Then,by injecting three kinds of PLA microspheres into the skin of guinea pig's back,and hematoxylin eosin staining(H&E)and immunofluorescence were used to analyze the inflammatory reaction.As well as Masson staining and picrosirius red staining were analyzed for collagen regeneration.The results showed that PLLA microspheres had better biocompatibility,low-degree inflammatory reaction and stronger ability to stimulate collagen regeneration.It is suitable for use in dermal filler.Through the design of different chiralities PLA materials as potential immunoadjuvant and dermal filler,different chiralities materials are selected under different needs to get different degree of stimulation response.This strategy has a good application prospect in immunotherapy adjuvants and dermal filler. |
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