Study On The Safety And Degradation Of A New Sort Of Biodegradable Material

The study on the safety and degradation of a new sort of biodegradable material Purpose:In this paper, we studied bio-security and degradation of modificatory polycarbonate (M-PPC) through the cell toxicity test, acute systemic toxicity test, pyrogen test, skin irritation test, skin allergy test, hemolysis test, embedded test and degradation test in vitro, based on ISO 10993 and GB / T 16886 standards. This offered basis for application of material in many fields.Research Methods:(1) acute systemic toxicity testThe extracted material was injected by the tail vein of mice with a dose of 50ml/kg, at 37 oC, diet, mental state, body weight change and death condition of mice was researched as a criterion at 24h, 48h, 72h after the injection respectively.(2) Skin irritation testThe gauzes in the extracted M-PPC and the saline were attached to the experimental observation points of rabbits back respectively, scoring of erythema and edema were detected at 1,24,48 and 72h after dressing.(3) cytotoxicity testEvaluate cytotoxicity in vitro of materials and yin and yang groups by using of MTT method, detected optical density of materials and yin and yang groups by using of enzyme-linked immunosorbent assay detector, and found the degree of cell proliferation in each group.(4) allergy testingAfter intradermal induction, local induction, local excitation, the skin erythema and edema degree of animals were observed at 24, 48 and 72h after excitation, the evaluation was carried out based on skin reaction score evaluation.(5) hemolysis test10ml material extracts and the Yin and Yang groups was put into test tube, and was immerged water for 30min at 37 oC, after adding fresh anticoagulant rabbit blood 0.2ml, was immerged water for 60min and then centrifuged 5min (2500r/min), optical density (OD) value of extracted supernatant was read by of using spectrophotometric meter, hemolysis rate was calculated according to OD values.(6) pyrogen testThe material extracts was injected into ear vein of rabbits at a dose of 10ml/kg at 38 oC. Detected temperature every hour after injection, temperature value was calculated by the highest body temperature of the three times minus the normal body temperature value.(7) implantation experimentThe M-PPC was implanted into the both sides of rabbit spinal, 2-3 of the rabbits were sacrificed at 1,4,12,26 weeks after implantation, the muscle tissue around wrapping material 0.5-1cm was cut off , and HE and Masson's staining were applied, response of the tissue around the implant site as well as fiber cavity thickness, inflammatory cells and the presence condition of other cells were observed under light microscope,.(8) in vitro degradation testAccelerated degradation testThe materials was put into the PBS buffer solution with pH = 7.4, placed into water at 70 oC, two kinds of materials were collected at 2 and 7 days, PBS was drained, the materials was dried, and weighed. Weight loss rates and molecular weight were measured. Real time degradation experimentThe materials was put into the PBS buffer solution with pH = 7.4, placed into water at 70 oC, two kinds of materials were collected at end of 1, 2, 3, 4, 5, 6 months, PBS was drained, the materials was dried, and weighed. Weight loss rates and m,olecular weight were measured. ResultsThe present results showed that: the mice was not adverse effects, activities and eating was well, and weight was enhancive, no death was observed during 3 days. Body temperature of the rabbits was normal after injection of M-PPC in pyrogen test, this indicating materials have no pyrogenic reaction. Allergic reaction was 0, no allergic effect, no skin stimulation. Material hemolysis was 0.93%, with the great blood compatibility. After the implantation, the rabbits hve no adverse reaction, the general states was good, the compatibility between material and the surrounding muscle tissue was good after material was removed, the material is completely wrapped at 26 week. The intima was smooth. The histopathology showed that the inflammatory cells surrounding the material decreased with prolongation of the implantation time, and the inflammatory cells were disappeared after 26 weeks the. Thickness of the fibrous capsule surrounding the material increased with time going. Degradation experiments showed that: quality and molecular weight of M-PPC were both decreased, decreasing of weight was faster than quality in various stages in vitro. ConclusionsM-PPC has no acute systemic toxicity, no pyrogen produced, no allergic effects, no skin stimulation; no hemolysis and cytotoxicity in vivo, biocompatibility was good after implantation of materials, and without any adverse reactions on animals. Degradation tests in vitro showed that M-PPC has a good degradation, decreasing of molecular weight was much faster than the quality, and with a certain regularity of the degradation rate, consistent with the requirements of biodegradable material.