Macroporosity enhances vascularization of electrospun scaffolds

Background: One of the greatest challenges in scaffold-based tissue engineering remains poor and inefficient penetration of cells into scaffolds to generate thick vascularized and cellular tissues. Electrospinning has emerged as a preferred method for producing scaffolds with high surface area-to-volume ratios and resemblance to extracellular matrix. However, cellular infiltration and vascular ingrowth are insufficient because of lack of macropore interconnectivity in electrospun scaffolds with high-fiber density. In this study, we report a novel two-step electrospinning and laser cutting fabrication method to enhance the macroporosity of electrospun scaffolds. Materials and methods: Polycaprolactone dissolved in hexafluoroisopropanol was electrospun at 25 kV to create uniform 100-120 mu m sheets of polycaprolactone fiber mats (1- to 5-mu m fiber diameter) with an array of pores created using VERSA LASER CUTTER 2.3. Three groups of fiber mats with three distinct pore diameters (300, 160, and 80 mm, all with 15% pore area) were fabricated and compared with a control group without laser cut pores. After laser cutting, all mats were collagen coated and manually wrapped around a catheter six times to form six concentric layers before implantation into the omentum of Lewis rats. Cellular infiltration and vascular ingrowth were examined after 2 wk. Results: Histologic analysis of 14-d samples showed that scaffolds with laser cut pores had close to 40% more cellular infiltration and increased vascular ingrowth in the innermost layers of the construct compared with the control group. Despite keeping pore area percentage constant between the three groups, the sheets with the largest pore size performed better than those with the smallest pore sizes. Conclusions: Porosity is the primary factor limiting the extensive use of electrospun scaffolds in tissue engineering. Our method of LASER cutting pores in electrospun fibrous scaffolds ensures uniform pore sizes, easily controllable and customizable pores, and enhances cellular infiltration and vascular ingrowth, demonstrating significant advancement toward utility of electrospun scaffolds in tissue engineering. (C) 2013 Elsevier Inc. All rights reserved.