Developing biomimetic cartilaginous tissues that support locomotion while maintaining chondrogenic behavior is a major challenge in the tissue engineering field. Specifically, while locomotive forces demand tissues with strong mechanical properties, chondrogenesis requires a soft microenvironment. To address this challenge, 3D cartilage‐like tissue is fabricated using two biomaterials with different mechanical properties: a hard biomaterial to reflect the macromechanical properties of native cartilage, and a soft biomaterial to create a chondrogenic microenvironment. To this end, a bath composed of an interpenetrating polymer network (IPN) of polyethylene glycol (PEG) and alginate hydrogel (MPa order compressive modulus) is developed as an extracellular matrix (ECM) with self‐healing properties. Within this bath supplemented with thrombin, human mesenchymal stem cell (hMSC) spheroids embedded in fibrinogen are 3D bioprinted, creating a soft microenvironment composed of fibrin (kPa order compressive modulus) that simulate cartilage's pericellular matrix and allow a fast diffusion of nutrients. The bioprinted hMSC spheroids present high viability and chondrogenic‐like behavior without adversely affecting the macromechanical properties of the tissue. Therefore, the ability to locally bioprint a soft and cell stimulating biomaterial inside of a mechanically robust hydrogel is demonstrated, thereby uncoupling the micro‐ and macromechanical properties of the 3D printed tissues such as cartilage.
The design of hydrogels where multiple interpenetrating networks enable enhanced mechanical properties can broaden their field of application in biomedical materials, 3D printing, and soft robotics. We report a class of self-reinforced homocomposite hydrogels (HHGs) comprised of interpenetrating networks of multiscale hierarchy. A molecular alginate gel is reinforced by a colloidal network of hierarchically branched alginate soft dendritic colloids (SDCs). The reinforcement of the molecular gel with the nanofibrillar SDC network of the same biopolymer results in a remarkable increase of the HHG’s mechanical properties. The viscoelastic HHGs show >3× larger storage modulus and >4× larger Young’s modulus than either constitutive network at the same concentration. Such synergistically enforced colloidal-molecular HHGs open up numerous opportunities for formulation of biocompatible gels with robust structure-property relationships. Balance of the ratio of their precursors facilitates precise control of the yield stress and rate of self-reinforcement, enabling efficient extrusion 3D printing of HHGs.more » « less
- Award ID(s):
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- Nature Publishing Group
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- Nature Communications
- Medium: X
- Sponsoring Org:
- National Science Foundation
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