Volumetric printing (VP) is a light‐mediated technique enabling printing of complex, low‐defect 3D objects within seconds, overcoming major drawbacks of layer‐by‐layer additive manufacturing. An optimized photoresin is presented for VP in the presence of cells (volumetric bioprinting) based on fast thiol–ene step‐growth photoclick crosslinking. Gelatin‐norbornene (Gel‐NB) photoresin shows superior performance, both in physicochemical and biocompatibility aspects, compared to (meth‐)acryloyl resins. The extremely efficient thiol–norbornene reaction produces the fastest VP reported to date (≈10 s), with significantly lower polymer content, degree of substitution (DS), and radical species, making it more suitable for cell encapsulation. This approach enables the generation of cellular free‐form constructs with excellent cell viability (≈100%) and tissue maturation potential, demonstrated by development of contractile myotubes. Varying the DS, polymer content, thiol–ene ratio, and thiolated crosslinker allows fine‐tuning of mechanical properties over a broad stiffness range (≈40 Pa to ≈15 kPa). These properties are achieved through fast and scalable methods for producing Gel‐NB with inexpensive, off‐the‐shelf reagents that can help establish it as the gold standard for light‐mediated biofabrication techniques. With potential applications from high‐throughput bioprinting of tissue models to soft robotics and regenerative medicine, this work paves the way for exploitation of VPs unprecedented capabilities.

Volumetric Bioprinting Volumetric bioprinting: the next move. In article number 2102900, Marcy Zenobi‐Wong and co‐workers further develop a revolutionary type of light‐based 3D printing called “volumetric” or “tomographic” printing by introducing the use of an optimized, high‐performance photo click‐based photoresin that results in extremely fast and biocompatible printing of complex 3D models. Illustration by Riccardo and Massimiliano Rizzo.

Cell‐laden hydrogels used in tissue engineering generally lack sufficient 3D topographical guidance for cells to mature into aligned tissues. A new strategy called filamented light (FLight) biofabrication rapidly creates hydrogels composed of unidirectional microfilament networks, with diameters on the length scale of single cells. Due to optical modulation instability, a light beam is divided optically into FLight beams. Local polymerization of a photoactive resin is triggered, leading to local increase in refractive index, which itself creates self‐focusing waveguides and further polymerization of photoresin into long hydrogel microfilaments. Diameter and spacing of the microfilaments can be tuned from 2 to 30 µm by changing the coherence length of the light beam. Microfilaments show outstanding cell instructive properties with fibroblasts, tenocytes, endothelial cells, and myoblasts, influencing cell alignment, nuclear deformation, and extracellular matrix deposition. FLight is compatible with multiple types of photoresins and allows for biofabrication of centimeter‐scale hydrogel constructs with excellent cell viability within seconds (<10 s per construct). Multidirectional microfilaments are achievable within a single hydrogel construct by changing the direction of FLight projection, and complex multimaterial/multicellular tissue‐engineered constructs are possible by sequentially exchanging the cell‐laden photoresin. FLight offers a transformational approach to developing anisotropic tissues using photo‐crosslinkable biomaterials.

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Sulfated polysaccharides are ubiquitous in living systems and have central roles in biological functions such as organism development, cell proliferation and differentiation, cellular communication, tissue homeostasis, and host defense. Engineered sulfated polysaccharides (ESPs) are structural derivatives not found in nature but generated through chemical and enzymatic modification of natural polysaccharides, as well as chemically synthesized oligo‐ and polysaccharides. ESPs exhibit novel and augmented biological properties compared with their unmodified counterparts, mainly through facilitating interactions with other macromolecules. These interactions are closely linked to their sulfation patterns and backbone structures, providing a means to fine‐tune biological properties and characterize structural–functional relationships by employing well‐characterized polysaccharides and strategies for regioselective modification. The following review provides a comprehensive overview of the synthesis and characterization of ESPs and of their biological properties. Through the pioneering research presented here, key emerging application areas for ESPs, which can lead to novel breakthroughs in biomedical research and clinical treatments, are highlighted.

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Extensive availability of engineered autologous dermo-epidermal skin substitutes (DESS) with functional and structural properties of normal human skin represents a goal for the treatment of large skin defects such as severe burns. Recently, a clinical phase I trial with this type of DESS was successfully completed, which included patients own keratinocytes and fibroblasts. Yet, two important features of natural skin were missing: pigmentation and vascularization. The first has important physiological and psychological implications for the patient, the second impacts survival and quality of the graft. Additionally, accurate reproduction of large amounts of patient’s skin in an automated way is essential for upscaling DESS production. Therefore, in the present study, we implemented a new robotic unit (called SkinFactory) for 3D bioprinting of pigmented and pre-vascularized DESS using normal human skin derived fibroblasts, blood- and lymphatic endothelial cells, keratinocytes, and melanocytes. We show the feasibility of our approach by demonstrating the viability of all the cells after printing in vitro, the integrity of the reconstituted capillary network in vivo after transplantation to immunodeficient rats and the anastomosis to the vascular plexus of the host. Our work has to be considered as a proof of concept in view of the implementation of an extended platform, which fully automatize the process of skin substitution: this would be a considerable improvement of the treatment of burn victims and patients with severe skin lesions based on patients own skin derived cells.

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