Biocompatibility And Binding Effect Of Shape Memory Polymer Polycaprolactone

1.BackgroundBioabsorbable materials as early as 1960s was used to study internal fixation for fracture.With the passage of time,more and more absorbable materials have been studied and used in various fields of life,especially in biomedicine.The reports shows that bioabsorbable materials have been used for biomedical in many aspects,including surgical suture,fracture repair,teeth deformity,intelligent drug delivery carrier,fusion joint treatment and so on.There are many successful cases,biodegradable materials attracted more and more attention in recent years.The main driving force for research on biodegradable implants is that in physiological environment they can gradually degraded.Compared with permanent implants,biodegradable materials implanted in the body,gradually lost,until completely degraded slowly disappeared,so this kind of material can reduce or even eliminate many problems caused by permanent implants,such as long-term endothelial injury,mechanical stimulation,local chronic inflammation and so on.The biodegradable materials used as bone implants can be divided into ceramics,degradable metals and degradable polymeric materials.The representative of the absorbable bioceramics is tricalcium phosphate,which has good biocompatibility.It is less inflammation and rejection,no biological toxicity,and it can withstand greater stress and mechanical loss.But the disadvantage is that the disadvantage is that this kind of material is brittle,and it’s tensile,shear,torsional performance is poor.The representative of degradable metal is magnesium alloy,zinc alloy and iron alloy.This kind of material not only has good strength support,but also has good ductility.The disadvantage is that the degradation speed of this kind of alloy is faster,so it often causes the loss of mechanical integrity.One week after the operation,the rapid formation of hydrogen bubbles is another factor restricting its development.Compared with the rest of the implants,the absorbable polymer materials have good biocompatibility and slow degradation.It can guarantee the effectiveness of implant fixation,and it also can avoid the adverse consequences of rapid degradation,and his degradation products can be safely discharged from the human body.The main representatives of this kind of materials are polycaprolactone,poly lactic acid,polyurethane and so on.Shape memory concept was first put forward in 1840s,but its real importance is in the 1960s,as a heat shrinkable polyethylene pipe attracted widespread attention.The follow-up study began in 1980s and was developed rapidly in 90s and has made significant progress in the last 10 years.As a new type of biomedical intelligent material,shape memory materials can be used to design different properties to meet the requirements of the biomedical field.In 1950s,the shape memory phenomenon was first described,mainly the shape memory of irradiated hinge polyethylene.In 1970s,because of the development and application of shape memory polymers in the aerospace field,NASA has aroused widespread interest.1988,Japan successfully developed thermoplastic shape memory polymer,2001,Andreas Lendlein made a systematic study on shape memory polymer,and can be used to study many aspects of biomedical degradable shape memory polymer,is widely used in dental and orthopedic department of orthopedics and drug carrier and so on.After more than 20 years of development,people continue to improve the performance of shape memory polymers,so that there are more and more applications of shape memory polymers in biomedical field.So far,shape memory polymers have been widely used in biomedical field.2.ObjectiveIn this study,we aimed to study the biocompatibility of biodegradable shape memory materials in vitro and the safety and effectiveness of the binding tape in vivo3.Materials&MethodsThe first partThe mouse embryonic fibroblast 3T3-L1 cells were cultured in vitro.The cells were seeded into 6-well cell culture plates,each with 4 holes,material group and control group.Let the cells cover glass,Immunohistochemical method was used to detect the expression of vimentin.It was found that there was no difference between the control group and the material group.The mouse embryonic fibroblast cells cultured 3T3-L1 cells were inoculated into6-well plate cells,each with 3 holes.The cell growth curve was recorded by the cell count and Trypan blue staining.Flow cytometry was used to detect cell growth,the observation group and control group had no significant changes in cell cycle.In the second part,Medical research on the effectiveness and safety of degradable shape memory polymer in vivo animal:The New Zealand white rabbits which were incomplete tibial fracture were used as animal models of fracture,We used biodegradable shape memory bundled with a fixed piece of bone fracture.It simulated the fixation of the bone in clinical department of orthopedics.After 2 weeks,X was used to examine the position of the bone slices.After 8 weeks,we gave them the lawn induced movement.Regular examinations were given every 6 weeks after surgery,these tests include the general observation,the observation of the bundle with the bone,the binding strength of the bundle,X radial observation,histological observation.Through these tests,we can analyze the effectiveness and safety of biodegradable shape memory tape binding in animals.4.ResultsImmunohistochemistry:the cells inoculated into the material group did not change significantly in cell morphology,the cells in the material group and the control group grew well,and the cell morphology was normal.The cells of the two groups had no obvious necrosis,atrophy and rupture.There was no significant difference between the two groups.Cell proliferation experiment:2 x 10~5digestive cells were inoculated into two groups of 6 holes,observe and count every two days,two groups of cells were able to proliferate in an orderly manner.On the first day after inoculation,we could count to 2.49 x 10~5cells,third days after inoculation,the average number of days in the material group was4.38 x 10~5 cells,fifth days average of 8.68 x 10~5 cells,with an average of seventh days of15.2 x 10~5 cells.In the control group,on the first day after inoculation,we could count to2.50 x 10~5 cells,third days after inoculation,the average number of days in the material group was 4.29 x 10~5 cells,fifth days average of 8.84 x 10~5 cells,with an average of seventh days of 14.6 x 10~5 cells.CCK was detected at different time points.In the control group and the experimental group,the cells showed the tendency of proliferation,the growth rate of absorbance value was similar,and there was no significant difference between the two groups.Statistical t test was used to compare the data of experimental group and control group P>0.05.It was found that there was no significant difference between the two groups and the control group.The results showed that the shape memory polymer had no significant effect on cell proliferation.Cell cycle test:Flow cytometry was used to detect the proportion of G1 phase,S phase and G2 phase of the experimental group and the control group.The results showed that the proportion of cells in the two groups was similar,and the difference of the cell cycle between the two groups was analyzed by T test.The results showed that P>0.05.It was no statistically significant difference between the two groups.Animal experiment:we developed a New Zealand white rabbit model of incomplete fracture,then we fixed the fracture with absorbable shape memory tape.After that we give the rabbit splint external fixation.There was no infection or death.Postoperative X showed that the fracture healed well.Postoperative rehabilitation exercise,no obvious deformity or dysfunction.When we went to the specimen,the soft tissue wrapped the fracture end,.There was a new bone formation,and occasionally malunion.The paraffin embedded,sliced,stained and observed by the various organs of animals can be seen:there is no obvious change in the morphology of organs.5.Conclusion(1)the biodegradable shape memory polymer has good biocompatibility(2)he biodegradable shape memory polymer had no significant effect on cell proliferation(3)The biodegradable shape memory polymer had no significant effect on cell cycle(4)the biodegradable shape memory polymer has good compatibility in animals,and has no obvious side effects.It is safe and effective to bind the fracture fragments(5)The biodegradable shape memory polymer degrades slowly in vivo,and binds to bone pieces in experimental animals for a long time,(6)Irradiation disinfection has no obvious structural damage to the biodegradable shape memory polymer and does not cause the disappearance of its shape memory effect.