Sulfated Yam Polysaccharide And Its Surface Modification Of Medical Polylactic Acid

Medical polylactic acid is widely used in the field of biomedical materials,but the biocompatibility of its surface is poor.It is mainly reflected in the formation of induced thrombosis,lack of effective sites recognized by cells and poor hydrophilicity,which is not conducive to cell adhesion and proliferation.Therefore,its surface should be modified to improve its biocompatibility.It is an effective means for the improvement of biocompatibility to fix the bioactive macromolecular polysaccharides and proteins with good biocompatibility in the medical material surface.This study is to through the layers of sulfated Chinese Yam polysaccharide and chitosan self-assembly modification of medical polylactic acid membrane surface preparation of a kind of biological compatibility and biological function of biomedical materials.The main researches are as follows:The Chinese Yam polysaccharides were extracted using ultrasonic assisted hot water extraction method.Single factor experiments,the Box-Behnken central composite design and response surface analysis of yam polysaccharide extraction conditions were optimized,the optimal extraction process parameters of yam polysaccharide:extraction temperature 40°C,solid-liquid ratio 1:8,extraction time 40min,ultrasonic power 270 W.The response surface analysis showed that the optimal extraction rate was 16.32%,while the verified extraction rate was 16.42%,which verified the feasibility of the model.Then the neutral yam polysaccharide（CYP）was obtained by purification.I₂-KI test of CYP showed that CYP did not contain starch.Sulfuric acid method was used to modify CYP,and SCYPs with different reaction time were prepared.The degree of substitution of SCYP1 was 0.27;The substitution degree of SCYP2 was 0.87;The degree of substitution of SCYP3 was 1.4.The characterization of CYP and SCYPs,such as characteristic absorption peaks,monosaccharide composition,molecular weight and helical structure,were analyzed.The weak absorption at 260²80nm indicated the presence of glycoproteins.From the infrared spectrum,SCYPs has not only the typical polysaccharide absorption peaks of-OH and C-H,but also the characteristic absorption peaks of S=O and C-O-S.And it is indicating that the sulfuric acid modification is successful.Monosaccharide composition analysis CYP contains amino glucose,mannose,ribose,rhamnose,glucuronic acid,galacturonic acid,amino galactose,glucose,galactose,xylose and arabinose.Fucose has degradation in the SCYPs.The molecular weights of CYP and SCYPs were 68.322 kDa、17.182 kDa、14.255KDa and 9.495KDa,respectively.Compared with CYP,the molecular weights of each derivative after sulfation were significantly decreased.The Congo red experiment showed that CYP had a triple helix structure in aqueous solution,which would disassemble in strong alkali solution,but SCYPs had a stable triple helix structure.The antioxidant,antibacterial,anticoagulant and antitumor activities of CYP and SCYPs were evaluated,respectively.The results showed that the free radical scavenging rate of polysaccharides could be improved by the sulfation of polysaccharides.Bacteriostatic experiments showed that CYP had no growth inhibition effect on E.coli and S.aureus,while SCYPs had no growth inhibition effect on E.coli and had a strong growth inhibition effect on S.aureus.The anticoagulant activity showed that CYP had no anticoagulant activity,while the APTT and TT of SCYPs were significantly prolonged with the increase of concentration and DS.Antitumor activity indicates that SCYP3 is most prominent against Caco-2 cells.SCYP3 with better biological activity was selected for the next phase of the experiment.The medical polyactide（PLA）film was modified by alternative depositon of SCYP and chitosan（CS）using Layer-by-layer self-assembly.XPS,UV-Vis and SEM were used to characterize the structure of the multilayer films.The characteristic elements of sulfuric acid group and chitosan can be found on the SCYP/CS multilayer film by XPS,and the element energy increases with the increase of the number of layers.The increase and growth pattern of multilayer films in UV spectrum showed uniform continuity.SEM observation showed that SCYP/CS multilayer film could be alternately assembled to fill up the cracks after the amination treatment,but the film surface was not as smooth as the natural PLA film.The water contact Angle test shows that with the increase of the number of assembly layers,the contact angle decreases alternately in a zigzag pattern,and the hydrophilicity of the film surface increases.The blood compatibility,cell adhesion and antibacterial effect of SCYP/CS multilayer membrane were evaluated,respectively.The results of the blood compatibility test showed that the adsorption amount of bovine serum albumin increased,the adhesion rate of platelets decreased,APTT and TT prolonged.Moreover,the coagulation system（TAT、C3a,C5a）were not activated,and the hemolysis rate was less than 5%after contact with the SCYP/CS multilayer membrane.SCYP/CS multilayer membrane significantly improved the adhesion of L929 cells compared with the control group.The multilayer membrane showed good inhibitory effect on E.coli and S.aureus.SCYP/CS multilayer film was used to preliminarily study the drug delivery of model drug tannic acid（TA）.The TA drug loading was tracked by UV-Vis,and the drug loading per unit area was 29.88±0.005μg/cm².The relationship was obtained by studying the release rate of multi-layer films under different conditions:the release rate of TA increased with the increase of pH value,temperature and ionic strength.The eight drug release curves were fitted by the pharmacokinetic model,and the most suitable drug release model was obtained.The anti-oxidation experiment of ABTS free radical on the drug-loaded multilayer film showed that TA released by the multilayer film could still react with ABTS free radical,indicating that TA could maintain its inherent antioxidant activity in the multilayer film.