Preparation And Properties Study Of Nano-Hydroxyapatite-Chitosan Neural Conduits

Background and objective: The artificial nerve conduit is currently the research hotspots in clinical treatment of peripheral nerve injury.After nerve transection,the artificial nerve conduit is able to bridge the defective nerve,reconnect the neurons,guide the orientated growth of regenerated nerves and restore the nerve function.It overcomes the problems such as mismatch,secondary surgery and immune rejection,is of great importance in clinical application.In this study,nano-hydroxyapatite and chitosan were innovatively used to prepare a new type of nerve conduit,the mechanical properties,biological properties and the in vitro compatibility of which were futher conducted to evaluate its potential application as a scaffold for peripheral nerve repair.Methods: Nano-hydroxyapatite-chitosan nerve conduits were prepared by hydrogel method combined with layer-by-layer self-assembly technology.Radial tensile test,axial compression test,in vitro degradation test,and in vitro p H measurement test were used to evaluate the biological and mechanical properties of the nerve conduits;Schwann cells were seeded on the surface of nerve conduits,cells cultured in multi-well plates as control,Calcein-AM/PI double staining and CCK8 were then performed to detect the effect of nerve conduits on cell survival and viability.Results: 1.The nano-hydroxyapatite-chitosan nerve conduit was obtained by combining the layer-by-layer self-assembly technique with the hydrogel method.2.The elongation,elongation rate and the maximum tensile force of the nano-hydroxyapatite-chitosan nerve conduit were 11.25 ± 1.06 mm,112.5 ± 10.6% and 41.88 ± 2.57 N,respectively.When the radial compression length was ranging from 10%to 40% of the diameter,the pressure on the catheter was increased with the increasing compression.When the compression amount was within20%,the pressure was relatively small.The nano-hydroxyapatite-chitosan nerve conduits degradated slowly in PBS solution,and tended to be stable after 4 weeks,and the mass loss rate after 8 weeks was between 4% and5%.The p H value of the nano-hydroxyapatite-chitosan nerve conduit gradually stabilized with time,and was stable at about 7.3.3.Calcein-AM/PI double staining of Schwann cells revealed undifferentiated cell survival rate(more than 90%)between catheter and control groupafter both 24 h and 48 h cell culture.24 h CCK8 results showed indistinctive cell viability between conduits group and control group.While after 3 days and 5 days culture,cell viability of the conduits group was significantly higher than control.Conclusion:1.Nano-hydroxyapatite-chitosan nerve conduits can be successfully prepared by injecting hydrogel method combined with layer-by-layer self-assembly technology.2.The nano-hydroxyapatite-chitosan nerve conduit shows axial compression and radial compression resistance,exhibiting good mechanical properties that meet the requirements of further experiments.The degradability of the conduit basically conforms the rate of nerve growth,which can provide support and protection for nerve growth.The p H value of the catheter is stable at a neutral value,which can provide a suitable physicochemical environment for cell growth and tissue regeneration.3.Nano-hydroxyapatite-chitosan nerve conduit shows no cytotoxicity and proliferation supportive on Schwann cells,exhibiting good neural biocompatibility.In conclusion,the nano-hydroxyapatite-chitosan nerve conduit presents proper mechanical properties and good biocompatibility,is a promising peripheral nerve repair scaffold material for clinical application.