Technological watch

As the demand for organ transplants continues to grow faster than the supply of available donor organs, a new source of functional organs is needed. High resolution high throughput 3D bioprinting is one approach towards generating functional organs for transplantation. For high throughput printing, the need for increased print resolutions (by decreasing printing nozzle diameter) has a consequence: it increases the forces that cause cell damage during the printing process. Here, a novel cell encapsulation method provides mechanical protection from complete lysis of individual living cells during extrusion-based bioprinting. Cells coated in polymers possessing the mechanical properties finely-tuned to maintain size and shape following extrusion, and these encapsulated cells are protected from mechanical lysis. However, the shear forces imposed on the cells during extrusion still cause sufficient damage to compromise the cell membrane integrity and adversely impact normal cellular function. Cellular damage occurred during the extrusion process independent of the rapid depressurization.

https://www.sciencedirect.com/science/article/pii/S2405886619300132?dgcid=rss_sd_allhttps://www.sciencedirect.com/science/article/pii/S2405886619300132Introduction to the state-of-the-art 3D bioprinting methods, design, and applications in orthopedicsPublication date: June 2020

Source: Bioprinting, Volume 18

Author(s): Julia Anna Semba, Adam Aron Mieloch, Jakub Dalibor Rybka

Cartilage injuries and bone loss become increasingly prevalent in modern societies. Articular cartilage and menisci have low or no capacity for self-repair and none of the available treatments provide satisfactory, long-term outcomes. Additionally, despite self-regenerating capabilities of bone tissue, the mechanism may fail or become insufficient, creating the need for surgical bone replacement, which is restrained by natural graft accessibility. 3D bioprinting is a rapidly developing technology emerging as a promising remedial therapy in orthopedics. The extensive and ongoing studies in this field are focused on such topics as cartilage and bone biology, standardization of cell culture protocols, bioink formulation, and 3D bioprinting technology. Recent results of these examinations, focused on applications in orthopedics, are presented in this review.

https://www.sciencedirect.com/science/article/pii/S2405886619300399?dgcid=rss_sd_allhttps://www.sciencedirect.com/science/article/pii/S2405886619300399Novel 3D printing technology for CT phantom coronary arteries with high geometrical accuracy for biomedical imaging applicationsPublication date: June 2020

Source: Bioprinting, Volume 18

Author(s): Karolina Stepniak, Ali Ursani, Narinder Paul, Hani Naguib

There is a growing interest in using Computed Tomography (CT) and Hounsfield Unit (HU) measurements in identifying and assessing non-calcified plaque; however, the complex geometry of the coronary arteries poses a challenge in achieving good image quality, which is crucial in providing patients with an accurate diagnosis. Minimizing artifacts associated with cardiac motion is also an important step in improving CT diagnostic accuracy of Coronary Artery Disease. Existing arterial phantoms are commonly straight, short tubular sections that are often rigid, and do not represent the geometry of the entire arterial network, with which image quality and Hounsfield Unit measurements vary and are dependent on. In this study, the process of manufacturing a plaque phantom with physiologically accurate geometry of the coronary arteries is demonstrated. A computer model is obtained by segmenting CTCA images, and several flexible commercially available materials are used to 3D print the model. The static and dynamic mechanical properties of the 3D printing materials are investigated under physiologically relevant loading and the CT numbers of contrast-enhanced tubular samples with 50%, 75%, and 90% concentric stenosis are characterized and compared with ranges for lipid-rich and fibrous plaque. The proposed plaque phantom design offers the possibility of investigating the effect of non-calcified plaque geometry and arterial motion on various parameters in CT optimization studies.

https://www.sciencedirect.com/science/article/pii/S2405886620300014?dgcid=rss_sd_allhttps://www.sciencedirect.com/science/article/pii/S2405886620300014Multilayered microcasting of agarose–collagen composites for neurovascular modelingPublication date: March 2020

Source: Bioprinting, Volume 17

Author(s): Hossein Heidari, Hayden Taylor

The in vitro fabrication of vascular networks is one of the most complex challenges currently faced in tissue engineering. We describe a method to create multi-layered, cell-laden hydrogel microstructures with coaxial geometries and heterogeneous elastic moduli. The technique can be used to build in vitro vascular structures that are fully embedded in physiologically realistic hydrogels. Our technique eliminates rigid polymeric surfaces from the vicinity of the cells—overcoming a limitation of many microfluidic models—and allows layers of multiple cell types to be defined with tailored ECM composition and stiffness, and in direct contact with each other. We demonstrate channels with internal diameters as small as 175 ??m, and agarose–collagen (AC) gels whose Young’s moduli range from 1.4–8.3 ?kPa. We also show co-axial geometries with layer thicknesses as small as 125 ??m. One potential application of such structures is to simulate brain microvasculature. Towards this goal, the composition and mechanical properties of the composite AC hydrogels are optimized for cell viability and biological performance in both 2D and 3D culture. Seven-day viability of human microvascular endothelial cells (HMECs) and SY5Y glial cells is found to be maximized with a collagen content of 0.05% (w/v) when agarose content ranges between 0.25% and 1% (w/v). Additionally, we quantify the roles of type I bovine and rat-tail collagen, Matrigel, and poly-d-lysine–collagen–Matrigel coatings in promoting HMEC spreading, proliferation and confluence. 3D triple-layer vascular constructs have been fabricated, composed of a cannular monolayer of HMECs surrounded by two regions of SY5Ys with differing spatial densities. The endothelia are confluent and maintain trans-endothelial electrical resistance (TEER) values around 300 ?? ?cm2 over 11.5 days. This prototype opens the way for intricate multi-luminal blood vessels to be fabricated in vitro.

https://www.sciencedirect.com/science/article/pii/S2405886619300387?dgcid=rss_sd_allhttps://www.sciencedirect.com/science/article/pii/S2405886619300387Chondroprotective and osteogenic effects of silk-based bioinks in developing 3D bioprinted osteochondral interfacePublication date: March 2020

Source: Bioprinting, Volume 17

Author(s): Joseph Christakiran Moses, Triya Saha, Biman B. Mandal

Attributing cell instructive features and multifunctionality to biological inks (bioinks) employed for three-dimensional (3D) printing strategies is very much essential to bring about a paradigm shift in developing next generation smart intuitive 3D bioprinted constructs. Giving perspective to this notion, we explore here the feasibilities in developing multifunctional silk-based cartilage and bone bioinks for recreating heterogeneous complicated tissue constructs such as the osteochondral interface. In this regard, the developed silk based bioinks exhibit shear thinning behaviour with quick thixotropic recovery (~90% recovery) aiding in printing self-standing structures with decent print fidelity. The hydrogel network within the 3D bioprinted constructs present good permeability enabling in forming an undulating demarcation region at the bioprinted osteochondral interface. Furthermore, the cartilage and bone inks used for the microextrusion based bioprinting of osteochondral constructs facilitate the spatial maturation and differentiation of encapsulated stem cells towards osteogenic and chondrogenic lineages. The incorporation of strontium doped nano-apatites activates hypoxia inducible factor (HIF-1?) related genes, conferring proangiogenic and chondroprotective traits to the bioinks. Involvement of strontium in down regulating cyclooxygenase-2 via inhibiting prostaglandins (PGE2) pathway enabled anti-osteoclastic activity while favouring M2 macrophage biasness. Altogether, these findings corroborate the potential of the developed nanocomposite bioinks for fabricating clinically viable grafts for osteochondral defect repair associated with osteoporosis.

Graphical abstract