Tailoring the void space and mechanical properties in electrospun scaffolds towards physiological ranges

Electrospinning has proven to be a promising method to produce scaffolds for tissue engineering despite the frequently encountered limitations in 3-dimensional tissue formation due to a lack of cell infiltration. To fully unlock the potential of electrospun scaffolds for tissue engineering, the void space within the fibrous network needs to be increased substantially and in a controlled manner. Low-temperature electrospinning (LTE) increases the fiber to fiber distance by embedding ice particles as void spacers during fiber deposition. Scaffold porosities up to 99.5% can be reached and in line with the increase in void space, the mechanical properties of the scaffolds shift towards the range for native biological tissue. While both the physiological mechanical properties and high porosity were promising for tissue engineering applications, control of the porosity in three dimensions was still limited when using LTE methods. Based on a range of LTE spun scaffolds made of poly(lactic acid) and poly(epsilon-caprolactone), we found that changing the ratio between the rate of ice crystal formation and polymer fiber deposition only had a small effect on the 3D-porosity of the final scaffold architecture. Varying the fiber stiffness, however, offers considerable control over the scaffold void space.