Regulation of electrospun scaffold stiffness via coaxial core diameter

Scaffold mechanics influence cellular behavior, including migration, phenotype and viability. Scaffold stiffness is commonly modulated through cross-linking, polymer density, or bioactive coatings on stiff substrates. These approaches provide useful information about cellular response to substrate stiffness; however, they are not ideal as the processing can change substrate morphology, density or chemistry. Coaxial electrospinning was investigated as a fabrication method to produce scaffolds with tunable stiffness and strength without changing architecture or surface chemistry. Core solution concentration, solvent and feed rate were utilized to control core diameter with higher solution concentration and feed rate positively correlating with increased fiber diameter and stiffness. Coaxial scaffolds electrospun with an 8 wt./vol.% polycaprolactone (PCL)-HFP solution at 1 ml h-1 formed scaffolds with an average core diameter of 1.1 ± 0.2 μm and stiffness of 0.027 ± 3.3 × 10-3 N mm-1. In contrast, fibers which were 2.6 ± 0.1 μm in core diameter yielded scaffolds with a stiffness of 0.065 ± 4.7 × 10-3 N mm-1. Strength and stiffness positively correlated with core diameter with no significant difference in total fiber diameter and interfiber distance observed in as-spun scaffolds. These data indicate that coaxial core diameter can be utilized to tailor mechanical properties of three-dimensional scaffolds and would provide an ideal scaffold for assessing the effect of scaffold mechanics on cell behavior.