The peripheral nervous system has a limited innate capacity for self-repair following injury, and surgical intervention is often required. For injuries greater than a few millimeters autografting is standard practice although it is associated with donor site morbidity and is limited in its availability. Because of this, nerve guidance conduits (NGCs) can be viewed as an advantageous alternative, but currently have limited efficacy for short and large injury gaps in comparison to autograft. Current commercially available NGC designs rely on existing regulatory approved materials and traditional production methods, limiting improvement of their design. The aim of this study was to establish a novel method for NGC manufacture using a custom built laser-based microstereolithography (μSL) setup that incorporated a 405 nm laser source to produce 3D constructs with ∼ 50 μm resolution from a photocurable poly(ethylene glycol) resin. These were evaluated by SEM, in vitro neuronal, Schwann and dorsal root ganglion culture and in vivo using a thy-1-YFP-H mouse common fibular nerve injury model. NGCs with dimensions of 1 mm internal diameter × 5 mm length with a wall thickness of 250 μm were fabricated and capable of supporting re-innervation across a 3 mm injury gap after 21 days, with results close to that of an autograft control. The study provides a technology platform for the rapid microfabrication of biocompatible materials, a novel method for in vivo evaluation, and a benchmark for future development in more advanced NGC designs, biodegradable and larger device sizes, and longer-term implantation studies.

Micro-stereolithography (μSL) is used to produce 3D porous polymer structures by templating high internal phase emulsions. A variety of structures are produced, including lines, squares, grids, and tubes. The porosity matches that of materials produced by conventional photopolymerization.

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For the first time a series of functional hydrogels based on semi-interpenetrating networks with both branched and crosslinked polymer components have been prepared and we show the successful use of these materials as substrates for cell culture. The materials consist of highly branched poly(N-isopropyl acrylamide)s with peptide functionalised end groups in a continuous phase of crosslinked poly(vinyl pyrrolidone). Functionalisation of the end groups of the branched polymer component with the GRGDS peptide produces a hydrogel that supports cell adhesion and proliferation. The materials provide a new synthetic functional biomaterial that has many of the features of extracellular matrix, and as such can be used to support tissue regeneration and cell culture. This class of high water content hydrogel material has important advantages over other functional hydrogels in its synthesis and does not require post-processing modifications nor are functional-monomers, which change the polymerisation process, required. Thus, the systems are amenable to large scale and bespoke manufacturing using conventional moulding or additive manufacturing techniques. Processing using additive manufacturing is exemplified by producing tubes using microstereolithography.

Bone is the second most common transplantation tissue after blood. While the use of bone grafts remains the optimum choice, the problems associated with them has made the use of synthetic implants ever more popular. Over the last decade, there has been a lot research into the development of engineered new bone, to replace damaged tissue. An important part of this research effort has gone into the development of three-dimensional porous scaffolds, to support and guide the new cells.Here, we describe our research into the fabrication and evaluation as bone scaffolds of 3D biodegradable structures made using Direct fs Laser Writing (DLW). The material we use is a photostructurable polylactidebased material (PLA) synthesized for this purpose [1]. We test its degradation in vitro in PBS and we show that the material looses one third of its weight after six weeks, therefore allowing the slow release of an implanted scaffold. We demonstrate the fabrication of artificial scaffolds with precisely controlled geometries and different pore sizes and we test them for up to eight weeks using the mouse pre-osteoblastic cell line MC3T3-E1 [2]. Our results show good cell adhesion and a preference to scaffolds with 86% porosity, compare to other porosities studied (Fig. 1). Our study shows that DLW is a suitable technique for the fabrication of 3D biodegradable scaffolds for bone repair and other tissue engineering applications. Fig. 1Porous wood-pile shaped scaffold with 86% porosity (a) and 82% porosity (b). After three weeks in culture, pre-osteoblastic cells proliferated remarkably more into the 86% porous scaffolds.