The Preliminary Study Of Colon Anastomosis With Biodegradable Stent,and The Motified Plga's Performance

Objective: Using the artificial intestinal juice in vitro environment,we are to observe the static degradation of the improved material of PLGA (PLA: PGA′s molar ratio is 50: 50,mass ratio of PTMC is2.5%,and the mass ratio of barium sulfate is10%), and to evaluate the bio-compatible of this materials;We want to prove that the material of the anastomosis stent is better than the single-layer interrupted suture method,through the preliminary animal experiment.Methods: Part I: Materials static degradation in vitro experiments. Dissolved in chloroform,the modified PLGA was cut into 2.2cm×2.2cm pieces with dip-coating method.The total is 30 pieces. Each piece was placed in artificial intestinal juice, the degradation temperature was kept at 37℃constantly,and the artificial intestinal juice was replaced at week 1,2,3,4,6,8.We dried the specimens to constant weight,and calculated the lost weigh to observe its degradation.Part II: Evaluation of biocompatibility of improved PLGA. To evaluate biocompatibility,we put heat source experiments,hemolysis test,MTT method and micronucleus test on the material extracts. To determinate the hemolysis'extent and toxic classification of the materials and evaluate the biocompatibility of modified PLGA material,we used absorbance determination,calculation of body temperature changes of the SD rats and micronucleus rate.Part III: The animal experiment of biodegradable anastomosis stents. The traditional single-layer interrupted suture and stent intestinal anastomosis were used in animal experiments. On day 7 and day 14,comparing avulsion force,blasting pressure,hydroxyproline content,and the HE staining,Masson Stain,we got a preliminary assessment of the stent method's application in the intestinal anastomosis.Results: 1. During week 2 and week 4 the improved PLGA material has the fastest rate of degradation,and the degradation rate is about 68%; 2. Evaluation of materials'biocompatibility. The rate of hemolysis and micronucleus rate were≤5%,and the increasesing temperature of heat Testing was less than 0.5℃. Material toxicity grading were below two grades with MTT method;3.The animal experiments showd that:①The inosculating time of stent group was significantly shorter than that of conventional anastomosis group: SAG: X±S=7.125+0.427;CAG: X±S= 18.75 +1.109. P<0.0001;②Between the two groups,the tentative determination of anastomotic avulsion force were greater than 6.5N,and there was no anastomotic rupture and avulsion;③SAG's burst pressure were much higher than CAG's. On day 7 and 14 the stent group's anastomotic blasting sites were far away from the normal intestinal wall, whereas on day 7 and 14 the control group's anastomotic sites were blasting. Day 7:SAG: X±S=32.95+0.4500 ; CAG: X±S=20.9+0.400.P=0.0025. Day14:SAG: X±S=67.15+1.35;CAG: X±S=44.3+1.100.P=0.0058;④Masson staining of anastomosi throwed that collagen fibers were blue,muscle fibers and cellulose were red. 7 days latter,we saw the accumulation of inflammatory cells,fibroblast proliferation,and a small amount of collagen deposition,but the collagen was thin and sparse. Anastomotic sites began to heal after 7 days. 14 days latter,we saw a large amount of collagen deposition,the collagen was thick and dense,and the anastomotic sites were almost healed.⑤Two groups on day 7 and day 14,hydroxyproline contents were not significantly different. Day 7:SAG: X±S=0.52+0.010ug/mg;CAG: X±S=0.515+0.035 ug/mg. P=0.903.Day14:SAG: X±S=0.81+0.01 ug/mg;CAG: X±S=0.835+0.045 ug/mg. P=0.6419.Conclusion:1.By improving the composition of the PLGA copolymer,we can make copolymers get different degradation speeds to meet different application requirements. The improved PLGA materials was in a slower degradation rate in the initial period ,during the period from week 2 to week 4 the materials had the fastest degradation rate, slower degradation rate was followed;2.The improved PLGA are non-heat,non-hemolytic,non-teratogenic,and safe non-toxic biodegradable materials of excellent biocompatibility;3.We preliminary indicated that comparing with the traditional single-layer hand-sutured anastomosis, the biodegradable stent for anastomosis is a new, simple,feasible and safe inosculation technique,which can shorten the operating time and raise the anastomotic sites'recent tension.