Biomimetic Electrospun Polycaprolactone Nanofibrous Scaffold For Anterior Crucial Ligament Tissue Engineering

Rupture of the anterior crucial ligament(ACL)is one of the most common orthopaedic injuries of the knee.Unlike other tendon tissue,the injury is a serious problem due to its inability of self-healing.Moreover,injured ACLs will result in instability of knees and subsequently lead to meniscal tears and cartilage damage.The ACL disrupted patients requiring reconstructive surgery,although bone-patellar tendon-bone(B-PT-B)autograft which is the gold standard for ACL reconstruction,it has discernible disadvantages including donor site morbidity and limited quantity.Allografts are alternative but they may increase the risk of disease infection and inflammatory response.The synthetic nondegradable grafts have been studied widely but they were hampered by certain problems including osteolysis and synovitis.Thus,tissue engineering strategy with biomimetic scaffolds has been investigated as a promising option for ACL reconstruction.In this study,we developed a novel dual-motor electrospinning collecting device,and fabricated integrated poly(?-caprolactone)(PCL)fibrous scaffold with ?random-aligned-random? structure so as to mimic the fiber alignment of the native ligament.The random region was further mineralized for chemical imitation to bone-ligament connection.Scanning electron microscopy(SEM)and tensile testing were performed to confirm the structural and mechanical properties of the scaffold,while cell experiment was performed to determine the effect of chemical and structural properties on human bone marrow mesenchymal stem cell(hBMSC)orientation,morphology and lineage-specific differentiation.PCL-MWCNTs(core)/Gelatin(shell)nanofibrous scaffold was fabricated by co-axial electrospinning.Characterization of the scaffold and cell experiment was performed to study the properties of the scaffold.We designed an electrospinning collecting device that allowed us to fabricate integrated nanofibrous scaffold with ?random aligned random? structure.By further mineralizing the random region,a scaffold with chemical and structural mimic to bone ligament connection can be obtained.The aligned PCL nanofibrous scaffold in this study had an ultimate tensile stress of 38 ± 6.2MPa which was comparable to native ACL.The tensile stress of the current scaffold was much higher than the previously reported scaffold which was collected by rotating drum(9.58 ± 0.71 MPa),and reached to that of a single PCL fiber(40 ± 10MPa).On the aligned regions,cells were aligned and parallel to the direction of fibers alignment and most of them were elongated spindle shaped which is close to tenocytes phenotype.By comparison,the cells exhibited polygonal or round shape on the random region of the scaffold without apparent alignment.Up regulation of tendon and bone specific gene expression of hBMSCs was revealed as early as day 7 and showed region specific characteristics on the scaffold.Aligned nanofibers structure promoted tenogenic differentiation of hBMSCs while mineralized random oriented nanofibers significantly enhanced osteogenesis.The region specific tenogenic and osteogenic differentiation were further confirmed by immunofluorescence.PCL-MWCNTs(core)/Gelatin(shell)nanofibrous scaffold was fabricated by co-axial electrospinning.The incorporation of MWCNTs improved the mechanical strength of the scaffold and has little influence on cell proliferation.The gelatin as shell material improved the hydrophilicity and biocompatibility of the scaffold.Also,the amount of Tnmd was increased.This improved scaffold has better imitation of natural ligament and is promising in ligament tissue enginerring.