GENERATION OF PREVASCULARIZED PLLA BIODEGRADABLE SCAFFOLDS BY DIP DRAWING AND DIFFUSION INDUCED PHASE SEPARATION (DIPS).

A critical obstacle in tissue engineering is to develop a massive structure of living cells upon transfer from the in vitro culture conditions into the host in vivo. A vascular network is required to supply essential nutrients, including oxygen, remove metabolic waste products and provide a biochemical communication “highway”. For these reasons to build an implantable structure in which vessel formation (angiogenesis) take place is mandatory. PLLA scaffolds usable in vascular tissue engineering were generated by dip-coating via Diffusion Induced Phase Separation (DIPS) technique. The scaffolds, with a vessel-like shape, were obtained by performing a DIPS process around a nylon fibre whose diameter was 700 μm. The fibre was first immersed into a 4% PLLA dioxane solution and subsequently immersed into a second bath containing distilled water. The covered fibre was then washed in order to eliminate the excess of dioxane and dried; finally the internal nylon fibre was pulled out so as to obtain a hollow biodegradable PLLA fibber. By Scanning Electron Microscopy observation the scaffolds have a lumen of ca. 700 μm and the internal surface show to be homogeneous with micro-pores of about 1-2 μm diameter. Moreover, a cross section analysis showed an open structure across the thickness of the scaffold walls. Inside the generated scaffolds we have cultured human endothelial cells; these have shown to be able to grow within the scaffolds and after 3 weeks they begin to form a “primordial” vessel-like structure, showing a well differentiate epithelial tissue.