A Synthetic Dynamic Polyvinyl Alcohol Photoresin for Fast Volumetric Bioprinting of Functional Ultrasoft Hydrogel Constructs

Abstract Tomographic volumetric bioprinting (VBP) enables fast photofabrication of cell‐laden hydrogel constructs in one step, addressing the limitations of conventional layer‐by‐layer additive manufacturing. However, existing biomaterials that fulfill the physicochemical requirements of VBP are limited to gelatin‐based photoresins of high polymer concentrations. The printed microenvironments are predominantly static and stiff, lacking sufficient capacity to support 3D cell growth. Here a dynamic resin based on thiol–ene photo‐clickable polyvinyl alcohol (PVA) and thermo‐sensitive sacrificial gelatin for fast VBP of functional ultrasoft cell‐laden hydrogel constructs within 7–15 s is reported. Using gelatin allows VBP of permissive hydrogels with low PVA contents of 1.5%, providing a stress‐relaxing environment for fast cell spreading, 3D osteogenic differentiation of embedded human mesenchymal stem cells and matrix mineralization. Additionally, site‐specific immobilization of molecules‐of‐interest inside a PVA hydrogel is achieved by 3D tomographic thiol–ene photopatterning. This technique may enable spatiotemporal control of cell‐material interactions and guides in vitro tissue formation using programmed cell‐friendly light. Altogether, this study introduces a synthetic dynamic photoresin enabling fast VBP of functional ultrasoft hydrogel constructs with well‐defined physicochemical properties and high efficiency.