Multimaterial, heterogeneous, and multicellular three-dimensional bioprinting

Bioprinting promises to create three-dimensional in vitro models to study pathological states and possible new therapies, and in the future, to produce complex tissue and organ replacements. This article will describe the recent advances in bioprinting technologies to engineer artificial tissues and organs by controlling spatial heterogeneity of chemical and physical properties of scaffolds and, at the same time, the cellular composition and spatial arrangement. Despite significant technological improvements in recent years, the positioning at the micrometric level and the switching of different cell types and biomaterials remain a challenge, which limits the development of resilient vascular, neural, and lymphatic networks for metabolites, signaling, and waste transport, and thus limits the development of thick and clinically relevant engineered vascularized tissues.