2022 Annual Meeting

Temperature-Sensitive Patternable Hydrogels for Long-Term Tissue Repair

Low back pain is commonly associated with intervertebral disc (IVD) degeneration and is oftentimes debilitating1. Current treatments aim to alleviate symptoms rather than repairing defects in the annulus fibrosus (AF), the exterior of the IVD. Approaches such as injectable hydrogels offer a solution to aid in increasing biomechanical properties and cell regeneration, but they fail to assume the anisotropic cell distribution of the AF2. Within the AF, there are lamellar sheets that alternate in the angle-ply orientation, allowing the IVD to withstand high forces3. An alternative to restore the structure of the AF involves freeform 3D bioprinting of cells within support baths. However, most of the current support baths are not designed for long-term cell culture and are often sacrificial4.

A novel patternable hydrogel support bath that undergoes a gelation at physiological temperatures (37℃) and has fluid-like behavior at room temperature (25℃) was developed. This support bath has shear-thinning and self-healing properties that allows for omnidirectional microextrusion of cell-laden bioinks to mimic the angle-ply architecture of the AF while at room temperature. At physiological temperature, the support bath upholds a higher storage modulus, allowing the cells to attach, continue to proliferate, and form tissues in the printed pattern.

The aim of this study was to investigate the printability of the hydrogel and the reproducibility of the system with extrusion. It was hypothesized that the support bath would be an amenable environment in which the cell-laden pattern would remain intact after printing. Cell viability assays such as CellTiter-Blue® and staining techniques were utilized to demonstrate the consistency in printing in terms of quantity and distribution of seeded cells within each printing study. This composite hydrogel is proposed to make way for innovative control over the geometry of the repair for cellular systems that pertain to tissue engineering application. In particular, those tissues with isotropic structures, such as the AF.

  1. Hartvigsen J. et al. What low back pain is and why we need to pay attention. Lancet, 2356 (2018).
  2. DiStefano T. J., et al. Development of a two-part biomaterial adhesive strategy for annulus fibrosus repair and ex vivo evaluation of implant herniation risk. Biomaterials 258 (2020).
  3. Chuah Y. J. et al. Scaffold-Free tissue engineering with aligned bone marrow stromal cell sheets to recapitulate the microstructural and biochemical composition of annulus fibrosus. Acta Biomater, 107 (2020).
  4. Patrício S. G. et al. Freeform 3D printing using a continuous viscoelastic supporting matrix. Biofabrication, 12 (2020).