Interfacial-Crystallization-Constructed Fractal Nanofiber-Based Bio-Platforms Enable Highly Effective Culture of Three-Dimensional Stem Cell Spheroids.

Artificial cell spheroids are gaining importance in tissue engineering and regenerative medicine fields. Biomimetic construction of stem cell spheroids is nevertheless challenging, and bioplatforms permitting controllable and high-efficient fabrication of functional stem cell spheroids are needed. Here, a fractal nanofiber-based bioplatform is developed based on a tunable interfacial-induced crystallization approach, allowing a programmed culture of artificial stem cell spheroids under an ultralow cell seeding density. Specifically, starting with the nanofibers of poly(L-lactide) (PLLA) and gelatin (P m G n ), an interfacial growth of PLLA nanocrystals is subsequently performed to construct the fractal nanofiber-based biotemplates (C-P m G n ). Cell experiments with human dental pulp stem cells (hDPSCs) demonstrate that the fractal C-P m G n could effectively decrease cell-matrix interactions, thus facilitating spontaneous cell spheroid formation even under a low cell seeding density (1 × 10 4 cells/cm 2 ). Nanotopological properties of the C-P m G n bioplatform can be tuned by adjusting the fractal degree, thus enabling its suitability for the 3D culture of diverse hDPSC spheroids. Such a strategy provides a relatively simple and low-cost option for formation, expansion, and utility of stem cell spheroids. It offers another promising pathway to advance the development of stem cell therapies.