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Biofabrication holds the potential to generate constructs that more closely recapitulate the complexity and heterogeneity of tissues and organs than do currently available regenerative medicine therapies. Such constructs can be applied for tissue regeneration or as in vitro 3D models. Biofabrication is maturing and growing, and scientists with different backgrounds are joining this field, underscoring the need for unity regarding the use of terminology. We therefore believe that there is a compelling need to clarify the relationship between the different concepts, technologies, and descriptions of biofabrication that are often used interchangeably or inconsistently in the current literature. Our objective is to provide a guide to the terminology for different technologies in the field which may serve as a reference for the biofabrication community. Biofabrication holds great potential in the fields of regenerative medicine and physiological 3D in vitro models by allowing the manufacture of complex tissue constructs with a higher degree of biomimicry to native tissues than do current biomedical solutions. As the number of biofabrication technologies being developed continues to expand, it is of paramount importance to adopt a concerted terminology framework and avoid generalizations. The ratio between the spatial resolution and the timescale of manufacture could be considered as a reliable measure to aid in the selection of an appropriate biofabrication technology for a desired application.

[...]adding the cells to the biomaterials with the interactions necessary to have the right environment for tissue formation in bioreactors and incubators adds yet another level of complexity to the process. By the time the general public became aware of bioprinting, 3D printing with inanimate materials had already produced a myriad of useful products expeditiously. [...]many could expect that bioprinting, being a specific application of the more general technology, would deliver equally versatile and easy‐to‐manufacture living biological products; the field of 3D bioprinting quickly captured the public's imagination. Bioprinted tissues can be interconnected (e.g., liver, heart, kidney, etc.) to test drugs on a body‐on‐a‐chip model before the start of human clinical trials. Tissues printed with gene‐edited cells from the diseased patient to achieve a normal endpoint or combination of extended bioprinted tissue units functionally interconnected similarly to that in the human body are examples that could lead to unforeseen progress in regenerative medicine.

Tissue engineering technology promises to solve the organ transplantation crisis. However, assembly of vascularized 3D soft organs remains a big challenge. Organ printing, which we define as computer-aided, jet-based 3D tissue-engineering of living human organs, offers a possible solution. Organ printing involves three sequential steps: pre-processing or development of ‘blueprints’ for organs; processing or actual organ printing; and postprocessing or organ conditioning and accelerated organ maturation. A cell printer that can print gels, single cells and cell aggregates has been developed. Layer-by-layer sequentially placed and solidified thin layers of a thermo-reversible gel could serve as ‘printing paper’. Combination of an engineering approach with the developmental biology concept of embryonic tissue fluidity enables the creation of a new rapid prototyping 3D organ printing technology, which will dramatically accelerate and optimize tissue and organ assembly.

Self-assembly is a fundamental process that drives structural organization in both inanimate and living systems. It is in the course of self-assembly of cells and tissues in early development that the organism and its parts eventually acquire their final shape. Even though developmental patterning through self-assembly is under strict genetic control it is clear that ultimately it is physical mechanisms that bring about the complex structures. Here we show, both experimentally and by using computer simulations, how tissue liquidity can be used to build tissue constructs of prescribed geometry in vitro. Spherical aggregates containing many thousands of cells, which form because of tissue liquidity, were implanted contiguously into biocompatible hydrogels in circular geometry. Depending on the properties of the gel, upon incubation, the aggregates either fused into a toroidal 3D structure or their constituent cells dispersed into the surrounding matrix. The model simulations, which reproduced the experimentally observed shapes, indicate that the control parameter of structure evolution is the aggregategel interfacial tension. The model-based analysis also revealed that the observed toroidal structure represents a metastable state of the cellular system, whose lifetime depends on the magnitude of cell-cell and cell-matrix interactions. Thus, these constructs can be made long-lived. We suggest that spherical aggregates composed of organ-specific cells may be used as \"bio-ink\" in the evolving technology of organ printing.

Using the atomic force microscope to locally probe the cell membrane, we observed the formation of multiple tethers (thin nanotubes, each requiring a similar pulling force) as reproducible features within force profiles recorded on individual cells. Forces obtained with Chinese hamster ovary cells, a malignant human brain tumor cell line, and human endothelial cells (EA hy926) were found to be 28 ± 10 pN, 29 ± 9 pN, and 29 ± 10 pN, respectively, independent of the nature of attachment to the cantilever. The rather large variation of the tether pulling forces measured at several locations on individual cells points to the existence of heterogeneity in the membrane properties of a morphologically homogeneous cell. Measurement of the summary lengths of the simultaneously extracted tethers provides a measure of the size of the available membrane reservoir through which co-existing tethers are associated. As expected, partial disruption of the actin cytoskeleton and removal of the hyaluronan backbone of the glycocalyx were observed to result in a marked decrease (30–50%) in the magnitude and a significant sharpening of the force distribution indicating reduced heterogeneity of membrane properties. Taken together, our results demonstrate the ability of the plasma membrane to locally produce multiple interdependent tethers—a process that could play an important role in the mechanical association of cells with their environment.

We have studied the structural and viscoelastic properties of assembling networks of the extracellular matrix protein type-I collagen by means of phase contrast microscopy and rotating disk rheometry. The initial stage of the assembly is a nucleation process of collagen monomers associating to randomly distributed branched clusters with extensions of several microns. Eventually a sol-gel transition takes place, which is due to the interconnection of these clusters. We analyzed this transition in terms of percolation theory. The viscoelastic parameters (storage modulus G′ and loss modulus G″) were measured as a function of time for five different frequencies ranging from ω = 0.2 rad/s to 6.9 rad/s. We found that at the gel point both G′ and G″ obey a scaling law G ′ ( ω ) ∝ G ″ ( ω ) ∝ ω Δ , with the critical exponent Δ = 0.7 and a critical loss angle δ ( tan ⁡ δ = G ' ' / G ' ) being independent of frequency as predicted by percolation theory. Gelation of collagen thus represents a second order phase transition.

A rapid vascular casting approach that uses carbohydrate glass as a sacricial template allows tissues to be built that can be kept alive for longer in the laboratory until needed for transplantation. Miller and colleagues report an approach for building fully vascularized tissues that is elegant, simple, fast and cheap.

A rapid vascular casting approach that uses carbohydrate glass as a sacrificial template allows tissues to be built that can be kept alive for longer in the laboratory until needed for transplantation.

Effective cryopreservation of oocytes is critically needed in many areas of human reproductive medicine and basic science, such as stem cell research. Currently, oocyte cryopreservation has a low success rate. The goal of this study was to understand the mechanisms associated with oocyte cryopreservation through biophysical means using a mouse model. Specifically, we experimentally investigated the biomechanical properties of the ooplasm prior and after cryopreservation as well as the consequences of reversible dismantling of the F-actin network in mouse oocytes prior to freezing. The study was complemented with the evaluation of post-thaw developmental competence of oocytes after in vitro fertilization. Our results show that the freezing-thawing process markedly alters the physiological viscoelastic properties of the actin cytoskeleton. The reversible depolymerization of the F-actin network prior to freezing preserves normal ooplasm viscoelastic properties, results in high post-thaw survival and significantly improves developmental competence. These findings provide new information on the biophysical characteristics of mammalian oocytes, identify a pathophysiological mechanism underlying cryodamage and suggest a novel cryopreservation method.

This paper discusses the reasons behind the success of Airbnb and provides a brief analysis of their business model. The possible revenue effect on the hotel industry is discussed as well as some suggested strategic measures that hotels may consider for successfully competing in the rapidly changing market for holding their fair share of accommodation demand.