(654e) Unconventional Biomaterials for Regenerative Engineering

Introduction: Across various areas of regenerative engineering, there have been limitations with controlling cell adhesion, stem cell differentiation, viability, growth, and blood-material compatibility. Conversion of simple and abundant items to advanced cell culture substrates addresses some of the current challenges in regenerative engineering. The departure from complex fabrication processes to the applications of unusual and ubiquitous materials provides another dimension to the engineering of viable multiscale tissue constructs and regenerative technologies. In addition, the use of sustainable constructs and novel fabrication strategies has the potential to increase access to regenerative engineering technologies on a global scale. In this work, we used unconventional biomaterials such as eggshells and paper for tissue repair.

Materials and Methods: We fabricated eggshell micro/nanoparticle (ESP) reinforced gelatin-based hydrogels to obtain mechanically stable and biologically active three-dimensional (3D) constructs that can differentiate stem cells into osteoblasts. The ESP-reinforced gels were then subcutaneously implanted in a rat model to determine their biocompatibility and degradation behaviors. In addition, these composite scaffolds were used to regenerate critical sized cranial defects in a rat model. We also used mineralized paper scaffolds through an origami-inspired approach to test their osteoinductivity and potential for tissue repair in in vitro and in vivo studies.

Results and Discussion: The ESP-reinforced scaffolds enabled the differentiation of stem cells without the use of specialized osteogenic growth medium. The ESP-reinforced gels exhibited significant enhancement in mineralization by the cells. Our findings indicated that the ESP composites exhibited superior mechanical properties and showed a favorable in vivo response by subcutaneous implantation in a rat model. These scaffolds were highly responsive to cells, and did not elicit inflammatory responses in vivo. The implants were easily accepted by the host, allowed for cellular infiltration in 3D, and highly vascularized. Implantation of ESP-reinforced scaffolds into critical sized cranial defects in a rat model resulted in significant bone regeneration in 12 weeks. The resulting bone volume and bone density were as high as the native bone using these composite scaffolds as determined by micro-computed tomography analyses.

We also fabricated origami-inspired paper-based scaffolds for biomineralization. Material properties of the paper-based mineralized scaffolds were determined to be highly tunable. The tensile modulus of the scaffolds increased significantly after the mineralization process. Gene expression results for the osteogenic differentiation markers revealed the osteoinductivity of the mineralized paper scaffolds. Subcutaneous implantation of the samples in rats demonstrated biocompatibility, vascularization, and integration in vivo.

Conclusions: Unconventional scaffolds that are readily available and adapted from nature exhibited biomimetic characteristics including porosity, structure, and bioactivity resulting in physiologically relevant constructs. The use of existing naturally derived materials for regenerative engineering provides an inexpensive and sustainable approach that benefits the economy and environment while providing unique solutions to unmet clinical needs. Many of the unconventional biomaterials are overlooked and under-studied for biomedical applications, partially for their simplicity as mundane items.

References: ¹Nguyen, M.A., Camci-Unal, G., Trends in Biotechnology, 38(2): 178-190, 2020. ²Suvarnapathaki, S., Wu, X., Lantigua, D., Nguyen, M.A., Camci-Unal, G., Nature Asia Materials, 11(1): 1-18, 2019. ³Wu, X., Stroll, S.I., Lantigua, D., Suvarnapathaki, S., Camci-Unal, G., Biomaterials Science, 7, 2675-2685, 2019.