Ionically annealed zwitterionic microgels for bioprinting of cartilaginous constructs

Abstract

Foreign body response (FBR) is a pervasive problem for biomaterials used in tissue engineering. Zwitterionic hydrogels have emerged as an effective solution to this problem, due to their ultra-low fouling properties, which enable them to effectively inhibit FBR in vivo. However, no versatile zwitterionic bioink that allows for high resolution extrusion bioprinting of tissue implants has thus far been reported. In this work, we introduce a simple, novel method for producing zwitterionic microgel bioink, using alginate methacrylate (AlgMA) as crosslinker and mechanical fragmentation as a microgel fabrication method. Photocrosslinked hydrogels made of zwitterionic carboxybetaine acrylamide (CBAA) and sulfobetaine methacrylate (SBMA) are mechanically fragmented through meshes with aperture diameters of 50 and 90 µm to produce microgel bioink. The bioinks made with both microgel sizes showed excellent rheological properties and were used for high-resolution printing of objects with overhanging features without requiring a support structure or support bath. The AlgMA crosslinker has a dual role, allowing also for both primary photocrosslinking of the bulk hydrogel as well as secondary ionic crosslinking of produced microgels, to quickly stabilize the printed construct in a calcium bath and to produce a microporous scaffold. Scaffolds showed ~20% porosity, and they supported viability and chondrogenesis of encapsulated human primary chondrocytes. Finally, a meniscus model was bioprinted, to demonstrate the bioink’s versatility at printing large, cell-laden constructs which are stable for further in vitro culture to support tissue maturation. This easy and scalable strategy of producing zwitterionic microgel bioink for high resolution extrusion bioprinting allows for direct cell encapsulation in a microporous scaffold and has potential for in vivo biocompatibility due to the zwitterionic nature of the bioink.

Anisotropic Articular Cartilage Biofabrication based on Decellularized Extracellular Matrix

“…Most of the current tissue engineering approaches rely on bulk hydrogels consisting of dense polymeric networks with a nanoscale mesh size, thus constraining encapsulated cells and failing to replicate tissue inner architecture. Recently, the field has been shifting towards hydrogels with higher void, which can increase nutrient diffusion [38] , cell proliferation, migration [39,40] and ECM production [41,42] , improving overall tissue maturation [38,[43][44][45][46][47] . Filamented light (FLight) biofabrication has emerged as a promising technique in this context.…”