Peripheral nerve injuries (PNIs) less than 5 mm in length self-repair compared with those with wider gaps1,2. Traditionally, PNIs of 20 mm or less have been repaired either by suturing nerves end-to-end, or by grafting. However, these techniques present surgical and patient recovery drawbacks, prompting the search for better technologies. Nerve guidance conduits (NGCs) have shown promise to mitigate these limitations but are still deficient in supporting satisfactory recovery of PNIs due to poor fit between the NGCs and the local environment. This project aims to address this by developing a biomimetic nerve guidance prototype with improved physical and biochemical support for optimal PNI recovery using highly biocompatible and bioresorbable Polyhydroxyalkanoates (PHAs).</div>
The PHAs, mcl-PHA and P(3HB) were produced via bacterial fermentation in a 30L Solaris bioreactor and characterised using techniques such as FTIR, NMR, DSC, Tensile testing etc. Two-dimensional films were produced by solvent casting method and assessed for their biocompatibility using NG108-15 cells. Nerve guidance conduits were produced by two methods including fused deposition modelling based 3D printing using the Cellink BioX printer and dip moulding using an automatic controlled dip moulding machine.
Production of the mcl-PHA resulted in a high titre and productivity. This productivity was about 15-fold higher in comparison with the reported values in literature. Mechanical analysis showed that the mcl-PHA had a Young’s modulus of 10 MPa and a maximum elongation at break of 630% compared to 588.8 MPa and 33.2% of P(3HB). The polymers have been 3D printed into NGCs with high fidelity. Similarly, a blend of the mcl-PHA and P(3HB) was successfully dip moulded into uniform tubes that were initially tested in vivo and found to be very suturable. The biological characterization of the flat films of PHAs demonstrated that the polymers have excellent biocompatibility with NG108-15 cells. Neat films of the mcl-PHA resulted in higher cell viability than tissue culture plastic by day 6. Additionally, confocal imaging of immunolabelled samples revealed that the PHAs highly supported neural extension.
Higher productivity and yields were achieved for the production of PHAs compared to values reported in literature. The polymers produced were highly biocompatible with NG108-15 neuronal cells and supported longer neurite extension in comparison with the tissue culture plastic. Also, the polymers were successfully 3D printed and dip moulded into uniform NGCs with desired dimensions. Initial in vivo studies showed that the polymer was very suturable and suitable for further studies into their potential use in the production of a next generation nerve guidance conduit.