Optimization of Electrospun Bilayer Vascular Grafts through Assessment of the Mechanical Properties of Monolayers.

Small-diameter vascular grafts must be obtained with the most appropriate materials and design selection to harmoniously display a variety of features, including adequate tensile strength, compliance, burst strength, biocompatibility, and biodegradability against challenging physiological and hemodynamic conditions. In this study, monolayer vascular grafts with randomly distributed or radially oriented fibers are produced using neat, blended, and copolymer forms of polycaprolactone (PCL) and poly(lactic acid) (PLA) via the electrospinning technique. The blending ratio is varied by increasing 10 in the range of 50-100%. Bilayer graft designs are realized by determining the layers with a random fiber distribution for the inner layer and radial fiber orientation for the outer layer. SEM analysis, wall thickness and fiber diameter measurements, tensile strength, elongation, burst strength, and compliance tests are done for both mono- and bilayer scaffolds. The findings revealed that the scaffolds made of neat PCL show more flexibility than the neat PLA samples, which possess higher tensile strength values than neat PCL scaffolds. Also, in blended samples, the tensile strength values do not show a significant improvement, whereas the elongation values are enhanced in tubular samples, depending on the blending ratio. Also, neat poly(l-lactide-co-caprolactone) (PLCL) samples have both higher elongation and strength values than neat and blended scaffolds, with some exceptions. The blended specimens comprising a combination of PCL and PLA, with blending ratios of 80/20 and 70/30, exhibited the most elevated burst pressures. Conversely, the PLCL scaffolds demonstrated superior compliance levels. These findings suggest that the blending approach and fiber orientation offer enhanced burst strength, while copolymer utilization in PLCL scaffolds without fiber alignment enhances their compliance properties. Thus, it is evident that using a copolymer instead of blending PCL and PLA and combining the PLCL layer with PCL and PLA monolayers in bilayer vascular graft design is promising in terms of mechanical and biological properties.

Investigation of biodegradability and cellular activity of PCL/PLA and PCL/PLLA electrospun webs for tissue engineering applications.

Biodegradability and cellular activity are key performance indicators that should be prioritized for tissue engineering applications. Biopolymer selection, determination of necessary structural properties, and their synergistic interactions play an active role in obtaining the expected biodegradability and biological activity from scaffolds. In this study, it is aimed to produce electrospun webs with improved biocompatibility by blending polycaprolactone (PCL) with polylactic acid (PLA) and poly-l-lactide (PLLA), and examine the effect of biopolymer selection and blend ratio on the biodegradability and cellular activity of surfaces. In this context, fibrous webs are produced from PCL/PLA and PCL/PLLA blends with a weight ratio of 80/20 and 50/50 and pure polymers of PCL, PLA, and PLLA by electrospinning method and subjected to morphological and biological analyses. The biodegradation tests are carried out hydrolytically while the cell viability and cell proliferation analyses are performed with adult human primary dermal fibroblasts and human umbilical endothelial cells (HUVECs). The results show that the fiber diameters of the fabricated webs ranged from 0.747 to 1.685 µm. At the end of the 5th month, it is observed that the biodegradation rates of the webs blended 50% with PLA and PLLA, in comparison to PCL ones, increase from 3.7% to 13.33% and 7.69%, respectively. On the other hand, cell culture results highlight that the addition of 20% PLA and PLLA improves the cellular activity of both cell types, but increased PLA or PLLA ratio in PCL webs has a negative effect as it makes the structure stiff and brittle.