| Backgroud and objective:The history of female sterilization study has one hundred years, it has born two hundreds method. It is spot to find a ideal fallopian tubes sterillization device. Physics methods of fallopian tubes sterillization such as plug or link can not solve contraception effectiveness, the application prospect was limited. Many materials were corrodent,adhesions agent or sclerosing agent, they was toxicity and damage. So, study and design a sterillization device of high performance,duration and nontoxic has import society and economic benefit.Biodegradable shape memory polymers are the novel and intelligent materials which have excellent biodegradable and shape memory properties. They play an important role in the surgical micro-invasive operation , medical implants, and have momentous biomedical application. Biodegradable shape memory polymers were processed into a certain shapes in vitro, then implanted into fallopian tubes through the hysteroscope.The implant button stimulated by body temperature can restore the shape and blocke the tube in order to contraception. In the previous study, our group has synthesized biodegradable poly(urethane urea) shape memory polymers (PDLLA-PUU SMPs) based on PDLLA Diols, and confirmed its biological safety and biocompatibility.In this study, we designed the ITD based on relevant data of rabbit and human fallopian tube, observed the shape memory characteristics, then they were implanted into rabbits fallopian tube in a temporary form, and the implant button stimulated by body temperature can restore the shape and blocked the tube. Therefore, biodegradation of the ITD and fallopian tube mucosal proliferative response were investigated,and methylene blue test and Hysterosalpingography showed that fallopian tube blocked. Finally the anti-fertility effect of ITD was observed . These preparation for next clinical trials.Expirical method:1. Design and study the shape memory characteristics of the ITD. According to human and rabbit oviduct relevant indicators, the ITD was designed, and a fine Injection molding machine was developed to process and product the ITD. Shape deformation and temperature on the shape memory fixation and recovery ratio were investigated by mechanical tensile tests to study the shape memory characteristics of the ITD.2. Female New-Zealand rabbits were used in this study, they were divided into experimental and control group. The ITDs were implanted into rabbit fallopian tubes of experimental group, the control group received only laparotomy and cesarean section surgery.2.1. Obeserved histocompatibility between materials and uterine tubal epithelium and measured the rabbit fallopian tube diameter, mucosal thickness, muscle thickness at different times after implantation of ITD.2.2. The biodegradation of ITD were investigated by real-time degradation test in vivo and the evaluating indicators were the weight loss rate ratio.2.3. The fallopian tube blockage was investigated by methylene blue test and Hysterosalpingography.2.4. The anti-fertility effect of ITD was observedResults:1. We produced screw-shaped IUD.When the deformation range was 100%, the shape memory properties of ITD was 93.2%, but when the deformation increased to 200%, the shape recovery ratio decreased to 85%; ITD showed good shape memory behavior when the deformation temperature was Tg+5℃, while the shape recovery ratio had apparent decrease when the deformation temperature was above Tg+25℃; the initiation recovery temperature of ITD was 30℃, and the recovery time shortened with the increasing of the recovery temperature.2. After implanted into the rabbit oviduct, the ITD rapidly recovered from the temporary shapes to the initial shapes and deformated and distorted with the shape changes of the rabbit oviduct. With the growth of implantation time, PDLLA-PUU SMPs were gradually degraded in the oviduct. The ITD caused acute inflammatory reaction in the oviduct epitheliums, with the PDLLA-PUU SMPs degradation, the acute inflammatory reaction changed into chronic fibrosis2.1 After 4 weeks, 12 weeks, 24 weeks and 48 weeks the experimental group and the control group, and the diameter and the mucosa measurements of fallopian tubes were 1.41±0.13mm, 0.92±0.27mm, 0.51±0.18mm, 0.03±0.01mm, 0.59±0.30mm and 0.08±0.06mm, 0.38±0.15mm, 0.53±0.20mm, 0.90±0.24mm, 0.31±0.15mm, and after 48 weeks Experiment showed that there were significant differences between the experimental group and the control group (P <0.01).2.2. Degradation in vivo: the weight loss was slowly rising during the IUD implanted 4 weeks, the weight loss in vivo and vitro were 14.2% and 7.2% in 4 weeks, and 72.5% and 38.0% in 12 weeks. Experiment showed that there were significant differences between in vivo and vitro (P <0.01) according to the results of the weight loss.2.3. Methylene blue test showed that the tubal blockage of experimental group was 98.3% and control group was 0 in 4 weeks after implantation; The tubal blockage of experimental group was 96.6% and control group was 5.0% in 24 weeks after implantation; 24 weeks after implantation, the developed bilateral uterus and undeveloped bilateral fallopian tube in the experimental group were observed by Hysterosalpingography, and the developed bilateral uterus and bilateral fallopian tube in the control group, and the contrast agent dispersion was visible in abdominal cavity;2.4. Anti-fertility experiment: 2 months and 4 months after implantation, the contraception rates were respectively 98.75% and 97.47%, and the contraception rates were 100% from 6 months to 12 months after implantation.Conclusions:1. Succeed in developing easy-to-implant ITD ,which had good shape memory properties ,with suitable size of rabbit fallopian tubes.2. The ITD worked well and achieved safe, efficient and long-lasting contraceptive effects When it was implanted in rabbit fallopian tubes . Both Proliferation of fibrous tissue and the ITD had the effects of tubal blockage. The degradation rate of the ITD in vivo matched the proliferation rate of tubal fibrous tissue was the key point to succeed tubal blockage, meanwhilethe it is also the foundation of successful contraception.
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