Next generation 3D-printed auricular implants involving degradable materials and cells for ultimate implant integration and tissue regeneration

Auricular reconstruction which is required to correct congenital birth defects remains a major challenge in plastic surgery1. Currently, casted non-degradable polymeric scaffolds, such as porous polyethylene (PE) are still widely used. Implant integration remains a problem with non-degradable scaffolds, with inflammation and infection still frequently occurring, and implant fracture and exposure (from skin) commonly observed. Inadequate biocompatibility and un-matching mechanics are likely reasons leading to those clinical complexities. This calls for re-consideration of materials and novel approaches for scaffold design and fabrication.

A 2-fold approach is planned in this project: Firstly, we will improve 3D-printed HDPE scaffold developed at our collaborator's (Southern Medical School, China), and focus on two aspects of development: 1) modify the implant surface to add biocompatibility. With novel fibre spinning, a layer of biodegradable nanofibers (e.g. polycaprolactone (PCL)) will be deposited on the HDPE scaffold; 2) explore the feasibility to set up a drug delivery system in the scaffold, with the aim of delivering anti-bacterials or promoting angiogenesis and tissue ingrowth. Silver ions and VEGF (vascular endothelial growth factor) will be incorporated by pre-spinning blending or impregnation after fibre spinning. To assess the performance of the modified implant and its efficacy releasing the drugs, fibroblasts, endothelial cells, and chondrocytes will be cultured with the scaffolds and cell adhesion, proliferation, and differentiation assessed. Drug release profiles will be collected, and tissue deposition and ingrowth monitored particularly concerning vascularization and fibrous tissue growth and integration with the scaffold.

Secondly, a tissue engineering approach will be adopted to assess whether native cartilage can be regenerated at the defect site. The bio-inert and non-degradable HDPE as the base scaffold material will be replaced by a natural polysaccharide printable material. Chondrocytes or mesenchymal stem cells will be mixed into the polysaccharide solution prior to printing, and printing parameters adjusted to fabricate following the auricular shape, maintain ultimate anatomical structure while retaining cell viability and phenotype. Formation of natural fibrous cartilage within the cell-containing scaffold will be assessed with the degradation of the initial scaffolding material measured.

It is hoped that the newly developed auricular scaffolds can offer next generation auricular implants with improved clinical performances, with ultimate implant integration or native tissue regeneration.

1. Ebrahimi A. et al, Reconstructive surgery of auricular defects: an overview, Trauma Mon. 20 (4), e28202 (2015).