Study On Fabrication And Properties Of Drug-loaded Core-shell Nanofibers

Nowadays,modern people are more likely to be engaged in outdoor sports and activities gradually.The incidence of sports injuries was increased year by year,and the annual incidence of Achilles tendon rupture has reached 1.8 cases/million people.At present,the surgery of Achilles tendon rupture is the main treatment for injured people.Achilles tendon itself is lack of blood supply and likely to cause incision infection,skin necrosis,Achilles tendon rupture and other complications(~10.1%)after the surgery.In order to improve the therapeutic effect of Achilles tendon rupture,avoid the occurrence of postoperative complications and promote the recovery of damaged tissue,the study proposed a new type of suture with drug-loaded function for treatment.In this paper,PLLA/PA-Heparin nanofiber suture was prepared by near-field coaxial electrospinning.Then its physical and chemical properties were characterized carefully.The effect of Achilles tendon injury was studied as well.In the experiment,the effects of various factors in the near-field spinning process and the preparation of the coaxial fibers were discussed and optimized.The composite fiber sutures with PA as the core and the PLLA as the shell with heparin were prepared.The mechanical properties and the biocompatibility of the fibers were characterized and improved.The performance of the suture was determined in the SD rat of Achilles tendon rupture model.The impoetant conclusions of this paper are as follows.First,in the suture preparation and performance characterization:(1)Built a high-precision mobile X-Y Stage,and used in near-field spinning technology.The results show that the viscosity range of the near-field spinning should be 600 ~ 1000 MPa·s.The suitable fiber spacing ought to be >5 ?m,or the fiber will be miscible.With the increase of the moving rate of the X-Y Stage,the diameter of fibers will be decreased,and the surface morphology would be best as the receiving speed is at 80 mm/s.(2)PA-6 was used as the core layer,PLLA as the shell.The injection rate of the core was 4 m L/h,and the shell 2 mL/h.The spinning distance was 0.5 ~ 3.0 mm and the spinning voltage was 1.0 ~ 3.0 kV.The the water absorption of fibers was higher than 36%,the mechanical strength PP6 group could be 143.9 MPa.(3)The PLLA/PA coaxial fiber suture with heparin was prepared.The tensile strength was improved ~12.2% after the heat setting process(116.5vs103.8 MPa).During the drug release,the release curve was smooth within 28 days,and finallythe release rate of 1.50 wt% group was the highest,reaching 88.5% in vitro.The change of pH and fiber degradation mass loss rate is consistent with the drug release curve.On the other hand,the biocompatibility of the fiber suture was characterized:(4)Mouse C2C12 myoblasts were cultured and showed that relative proliferation rate was > 75%;And the platelet adhesion density decreased significantly as the concentration of loading heparinincreased,the hemolytic rate was <5%.It proved that the drug-loaded sutures has a good blood compatibility.(5)After implantation of the abdominal cavity,HE staining showed that the number of inflammatory cells in the suture was much less than the clinical suture.The immunoinflammatory reaction was weaker and the wound healing was better.(6)SD rat Achilles tendon rupture model molecular biology experiments found that: Compared to the clinical usual suture,the TGF-?1 was more widely distributed and the VEGF of the PLLA/PA-Heparin suture was in a higher concentration,which can significantly promote the Achilles tendon tissue endogenous healing.Meantime it had no skin necrosis,Achilles tendon adhesion and other complications.The tensile strength of Achilles tendon was the highest at 28 days after operation,which was close to normal Achilles tendon tissue.Thus it proved that the PLLA/PA-Heparin suture suture had good mechanical compatibility.To sum up,the influence of the coaxial spinning in the near field is clarified and the important properties such as physical and biocompatibility of the suture are well characterized.The study is not only significant for the Achilles tendon rupture treatment,but also gives us suggestion that near-field spinning has good application and great potential in the biomedical field.