Fabrication and characterization of hierarchically organized nanoparticle-reinforced nanofibrous composite scaffolds.

Two different techniques were used to fabricate nanoparticle-reinforced nanofibrous scaffolds with different organizations of the minerals. First, a three-dimensional (3D) cylindrical nanofibrous scaffold made of poly-L-lactide and poly(L-lactide)/collagen (1:1) was fabricated using a modified electrospinning method. An alternating dipping method and a flow version of it were used to mineralize the 3D scaffolds. Flow mineralization was found to significantly improve the distribution of the mineral nanoparticles throughout the 3D nanofibrous scaffold, while mineral nanoparticles were found only on the periphery of the static mineralized scaffold. As a result of the mineral nanoparticle distribution, the compressive strength and modulus of the flow mineralized scaffold was found to be significantly greater than that of the static mineralized scaffold, despite having a lower mineral content. Energy-dispersive X-ray analysis and X-ray diffraction studies suggest that the mineral was composed of heterogeneous phases of calcium phosphates. This study demonstrates the importance of hierarchical and deliberate organization of the nanocomponents to optimize the mechanical properties, as is often found in nature.

In vivo study of novel nanofibrous intra-luminal guidance channels to promote nerve regeneration.

A novel nanofibrous construct for promoting peripheral nerve repair was fabricated and tested in a rat sciatic nerve defect model. The conduit is made out of bilayered nanofibrous membranes with the nanofibers longitudinally aligned in the lumen and randomly oriented on the outer surface. The intra-luminal guidance channel is made out of aligned nanofibrous yarns. In addition, biomolecules such as laminin and nerve growth factor were incorporated in the nanofibrous nerve construct to determine their efficacy in in vivo nerve regeneration. Muscle reinnervation, withdrawal reflex latency, histological, axon density and electrophysiology tests were carried out to compare the efficacy of nanofibrous constructs with an autograft. Our study showed mixed results when comparing the artificial constructs with an autograft. In some cases, the nanofibrous conduit with aligned nanofibrous yarn as an intra-luminal guidance channel performs better than the autograft in muscle reinnervation and withdrawal reflex latency tests. However, the axon density count is highest in the autograft at mid-graft. Functional recovery was improved with the use of the nerve construct which suggested that this nerve implant has the potential for clinical usage in reconstructing peripheral nerve defects.

A review on electrospinning design and nanofibre assemblies.

Although there are many methods of fabricating nanofibres, electrospinning is perhaps the most versatile process. Materials such as polymer, composites, ceramic and metal nanofibres have been fabricated using electrospinning directly or through post-spinning processes. However, what makes electrospinning different from other nanofibre fabrication processes is its ability to form various fibre assemblies. This will certainly enhance the performance of products made from nanofibres and allow application specific modifications. It is therefore vital for us to understand the various parameters and processes that allow us to fabricate the desired fibre assemblies. Fibre assemblies that can be fabricated include nonwoven fibre mesh, aligned fibre mesh, patterned fibre mesh, random three-dimensional structures and sub-micron spring and convoluted fibres. Nevertheless, more studies are required to understand and precisely control the actual mechanics in the formation of various electrospun fibrous assemblies.