| BackgroundThe breast is the sign of women's sexual organ, with the dual function of lactation and aesthetics. The lack of breast caused by various reasons, not only damages seriously the perfect body of women, but affects severely their mental condition. Therefore, breast reconstruction becomes the obligatory responsibility of breast surgeon. But the ideal breast filling material requires further research and development. Biodegradable plastics - medical carbon-dioxide polymer is a new type of biodegradable material, which is expected to be an ideal material for the breast reconstruction. However, the evaluation on the biological safety and biocompatibility should be taken before the application in clinic.ObjectiveEvaluate the biological safety and biocompatibility of medical carbon-dioxide polymer in vivo and vitro, so as to lay the foundation for the clinical application.MethodIn this study, according to the relevant standards of the ?Biological Evaluation of Medical Devices? of ISO 10993 and GB/T 16886, we perform the acute systemic toxicity test, the pyrogen test, the allergy test, the skin irritation test, the hemolysis test, the cytotoxicity test and the subcutaneous implantation test for the evaluation on the biological safety and biocompatibility of carbon-dioxide polymer, with chitin as a control.(1) The acute systemic toxicity testThirty rats were divided randomly into carbon-dioxide polymer group, chitin group and 0.9% physiological saline group, ten each group. Each group was injected corresponding material extract liquid and physiological saline via the tail vein with a dose 50ml/kg. Observed the general condition, toxicity performance,mortality and the change of body weight as evaluation standard at 24h, 48h, 72h after the injection.(2) The pyrogen test Six selected rabbits were randomly divided into carbon-dioxide polymer group and chitin group, three each group. The different material extract liquids were injected slowly into ear vein of rabbits with a dose of 10ml/kg. After the injection, measure the temperature every 0.5 hour, totally 6 times. The elevated temperature degree was the highest body temperature of 6 times minus the normal body temperature degree.(3) The allergy testTwenty albino guinea pigs were divided randomly into negative control group with 0.9% physiological saline, positive control group with 5% formaldehyde solution, carbon-dioxide polymer group and chitin group, five each group. Through the intradermal induction, local induction and excitation, observed the sensitized areas of each animal whether have erythema or edema after 24h, 48h, 72h, and scored.(4) The skin irritation testTen rabbits were divided randomly into carbon-dioxide polymer group and chitin group, five each group. Dropped the different material extract liquids and 0.9% physiological saline in the different gauze, and put the gauze in the experimental areas and control areas on the back of the rabbits. Evaluate the degree of the erythema and edema in 1h, 24h, 48h and 72h after removing the accessories.(5)The hemolysis test10ml 0.9% physiological saline as negative control group, distilled water as positive control group, material extracts liquids of carbon-dioxide polymer and chitin were put into five test tubes respectively, and immerged 37℃water to bath for 30min, then added diluted fresh anticoagulant rabbit blood 0.2ml, bathed for 60min in 37℃water and centrifuged 5min (2500r/min), detected the optical density (OD) values of supernatant liquids by using spectrophotometer, and then calculated hemolysis rate according to OD values(6)The cytotoxicity testWith Hela cells, complete medium as negative control group, 0.7% acrylamide as positive control group, evaluate the cytotoxicity of material extracts liquid in vitro using MTT method, then get the optical density by using enzyme-linked immunosorbent assay detector, and obtain the relative growth rate and toxicity grade of each group.(7)The subcutaneous implantation testThe carbon-dioxide polymer and chitin were implanted respectively into the subcutaneous tissue on different sides of the rabbit's spine. After taking the ultrasound when the materials were implanted 1,2,4,8 weeks, 6 rabbits were sacrificed every time. The tissue around wrapping material 0.5-1cm was cut off., HE stained, observed the tissue reaction around material implanted site under light microscope, such as the degree of the formation of fibrous capsule and the existence of inflammatory cells and other cellsResults(1)The rats of each group injected with the liquid were in good condition, the appetite and activity was normal, no deaths, and the body weight tended to increase. The two materials had non-toxicity effect.(2)The temperature of the rabbits was measured in normal range at each time, which indicated that the two materials had non-pyrogen effect.(3) The experimental animals had no edema and erythema in sensitized areas, which signified that the two materials had no allergic effect.(4) Primary irritation scores and primary irritation index of every experimental area is 0, which showed that the two materials had no irritation effect on the skin.(5)Hemolysis rate of the two materials were 0.88% and 1.12%, which signified that the two materials had no hemolysis effect and met the criterion.(6)The two materials had no significant effect on the cell morphology and growth, which certified that the two materials had no cytotoxicity effect.(7)Ultrasound examination after implanted 1,2,4,8 weeks showed that the edema around the two materials reduced and the fibrous capsule formatted gradually. The two materials and the surrounding subcutaneous tissue have a good compatibility. The two materials were completely package in 4 weeks, and the fibrous cyst wall is smooth. Histopathology confirmed that the response of inflammatory cells reduced with the implanted time, and fibrous cyst wall around the material became gradually dense and stable.ConclusionCarbon-dioxide polymer has good biological safety and biocompatibility, is expected to clinical applications. |
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