3.5. Hierarchical polymer chain alignment of SANFs
We asked if RJS induced alignment of polymer chains at the molecular scale, in addition to macroscale fiber alignment. ATR-FTIR spectra of the PCL-SANF constructs were examined by a polarized IR spectrometer when fibers positioned parallel and perpendicular to the electric vector direction of the polarizer (Supplementary Fig. 2G). Results show the typical FTIR spectra of PCL SANF in the range of 800–1800 cm−1 with the incident IR polarized parallel (zero degree) and perpendicular (ninety degree) to the nanofiber axis, revealing the chain orientation developed in the PCL super-aligned nanofibers produced by RJS. The intensity difference of the 1724 cm−1 carbonyl peak at the different polarized angles was 0.2937. The difference in ratio of amorphous (1161 cm−1) to crystalline (1724 cm−1) peaks at the different polarized angle was 0.3076. Taken together, these values being close to 0 suggest that most of PCL polymer chains were parallel to the nanofiber longitudinal axis.
3.6. Bioelimination and mechanical characterization
Uncrosslinked gelatin typically solubilizes in an aqueous medium, and is easily bioeliminated in vivo [27] and [28]. In order to assess if these properties were altered when blended with PCL, we quantified the rate of bioelimination of hybrid SANF scaffolds. The SANF fibers were cultured with cardiac fibroblasts in Transwell® plates (Supplementary Fig. 3A) for 2–56 days. Transwell® culture was utilized here as it allowed us to conveniently remove the scaffold for measuring scaffold dry weight while maintaining an environment that simulated biodegrading and bioeliminating conditions. Results show that after two weeks, there was no significant change in the remaining mass of the hybrid constructs for PCL/Gelatin-75/25, but dramatic and significant degradation for PCL/Gelatin-50/50 and near total dissolution of PCL/Gelatin-25/75 (Supplementary Fig. 3B). The data suggests that bioelimination of gelatin without crosslinking is protected in the PCL/Gelatin-75/25 configuration, but not in PCL/Gelatin-50/50 or PCL/Gelatin-25/75.