Extracellular vesicles (EVs) represent an emerging class of therapeutics with significant potential and broad applicability. However, a general limitation is their rapid clearance after administration. Thus, methods to enable sustained EV release are of great potential value. Here, we demonstrate that EVs from mesenchymal stem/stromal cells (MSCs) can be incorporated into 3D-printed gelatin methacrylate (GelMA) hydrogel bioink, and that the initial burst release of EVs can be reduced by increasing the concentration of crosslinker during gelation. Further, the data show that MSC EV bioactivity in an endothelial gap closure assay is retained after the 3D printing and photocrosslinking processes. Our group previously showed that MSC EV bioactivity in this assay correlates with pro-angiogenic bioactivity in vivo, thus these results indicate the therapeutic potential of MSC EV-laden GelMA bioinks.

Femtosecond laser induced densification within cell-laden hydrogels results in cellular alignment To cite this article: Zheng Xiong et al 2019 Biofabrication 11 035005 View the article online for updates and enhancements.

Abstract

In the past 5 years, oxygen-permeable films have been widely used for continuous additive manufacturing. These films create a polymerization inhibition zone that facilitates continuous printing in the additive mode of fabrication. Typically, oxygen-permeable films made out of Teflon are currently used. These films are expensive and are not commonly available. Hence, this research work investigates the feasibility of using commonly available low-cost oxygen-permeable films made from polydimethylsiloxane (PDMS) and polyurethane for continuous additive manufacturing. We also characterize the ablation depth range that can be achieved using these films and the potential use for subtractive ablation-based manufacturing as well as hybrid additive/ subtractive manufacturing. Results demonstrate that the PDMS films (600 lm thick) can be used for both additive and subtractive modes, whereas spin-coated PDMS thin film (40 lm thick) on glass coverslip and breathe-easy polyurethane film (20 lm thick) laminated on glass coverslip are suitable only for additive mode of fabrication. The latter two films are oxygen impermeable, however, they retain oxygen, which is capable of creating dead zone and thereby facilitates continuous printing. We anticipate that this work will help researchers to choose the appropriate oxygen-permeable film for continuous additive, subtractive, and hybrid additive/ subtractive manufacturing of complex three-dimensional structures for a range of applications.

Extracellular vesicles (EVs) are implicated as promising therapeutics and drug delivery vehicles in various diseases. However, successful clinical translation will depend on the development of scalable biomanufacturing approaches, especially due to the documented low levels of intrinsic EV‐associated cargo that may necessitate repeated doses to achieve clinical benefit in certain applications. Thus, here the effects of a 3D‐printed scaffold‐perfusion bioreactor system are assessed on the production and bioactivity of EVs secreted from bone marrow‐derived mesenchymal stem cells (MSCs), a cell type widely implicated in generating EVs with therapeutic potential. The results indicate that perfusion bioreactor culture induces an ≈40‐80‐fold increase (depending on measurement method) in MSC EV production compared to conventional cell culture. Additionally, MSC EVs generated using the perfusion bioreactor system significantly improve wound healing in a diabetic mouse model, with increased CD31+ staining in wound bed tissue compared to animals treated with flask cell culture‐generated MSC EVs. Overall, this study establishes a promising solution to a major EV translational bottleneck, with the capacity for tunability for specific applications and general improvement alongside advancements in 3D‐printing technologies.