Bioinks for Space Missions: The Influence of Long-Term Storage of Alginate-Methylcellulose-Based Bioinks on Printability as well as Cell Viability and Function.

Bioprinting is considered a key technology for future space missions and is currently being established on the International Space Station (ISS). With the aim to perform bioink production as a critical and resource-consuming preparatory step already on Earth and transport a bioink cartridge "ready to use" to the ISS, the storability of bioinks is investigated. Hydrogel blends based on alginate and methylcellulose are laden with either green microalgae of the species Chlorella vulgaris or with different human cell lines including immortilized human mesenchymal stem cells, SaOS-2 and HepG2, as well as with primary human dental pulp stem cells. The bioinks are filled into printing cartridges and stored at 4°C for up to four weeks. Printability of the bioinks is maintained after storage. Viability and function of the cells embedded in constructs bioprinted from the stored bioinks are investigated during subsequent cultivation: The microalgae survive the storage period very well and show no loss of growth and functionality, however a significant decrease is visible for human cells, varying between the different cell types. The study demonstrates that storage of bioinks is in principle possible and is a promising starting point for future research, making complex printing processes more effective and reproducible.

3D bioprinting of mineralizing cyanobacteria as novel approach for the fabrication of living building materials.

Living building materials (LBM) are gaining interest in the field of sustainable alternative construction materials to reduce the significant impact of the construction industry on global CO2 emissions. This study investigated the process of three-dimensional bioprinting to create LBM incorporating the cyanobacterium Synechococcus sp. strain PCC 7002, which is capable of producing calcium carbonate (CaCO3) as a biocement. Rheology and printability of biomaterial inks based on alginate-methylcellulose hydrogels containing up to 50 wt% sea sand were examined. PCC 7002 was incorporated into the bioinks and cell viability and growth was characterized by fluorescence microscopy and chlorophyll extraction after the printing process. Biomineralization was induced in liquid culture and in the bioprinted LBM and observed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and through mechanical characterization. Cell viability in the bioprinted scaffolds was confirmed over 14 days of cultivation, demonstrating that the cells were able to withstand shear stress and pressure during the extrusion process and remain viable in the immobilized state. CaCO3 mineralization of PCC 7002 was observed in both liquid culture and bioprinted LBM. In comparison to cell-free scaffolds, LBM containing live cyanobacteria had a higher compressive strength. Therefore, bioprinted LBM containing photosynthetically active, mineralizing microorganisms could be proved to be beneficial for designing environmentally friendly construction materials.

Production of natural colorants by liquid fermentation with Chlorociboria aeruginascens and Laetiporus sulphureus and prospective applications.

The replacement of potentially hazardous synthetic dyes with natural dyes and pigments are of great interest for a sustainable economy. In order to obtain cost-efficient, environmentally friendly and competitive products, improvements in the cultivation and extraction of pigment-producing organisms and in dyeing processes are necessary. In our study, we were able to scale up the production of xylindein by Chlorociboria aeruginascens from 3 to 70 L bioreactor cultivations. We have identified important bioprocess parameters like low shear stress (150 rpm, tip speed <0.5 m/s) for optimal pigment yield (4.8 mg/L/d). Additionally, we have demonstrated the potential of laetiporic acid production by Laetiporus sulphureus in various cultivation systems and media, achieving dried biomass concentrations of almost 10 g/L with a 7 L bioreactor cultivation after 17 days. Extractions performed at 70°C and 15 min incubation time showed optimal results. To the best of our knowledge, we have described for the first time the use of this pigment in silk dyeing, which results in a brilliant hue that cannot easily be produced by other natural pigments.

Development of a Gold Nanoparticle-Based Colorimetric Sensor for Water for Injection At-Line Impurity Testing.

The best-known rapid test using gold nanoparticles (AuNPs) is the human chorionic gonadotropin pregnancy test. AuNPs are a powerful tool in point-of-care testing because of their flexibility, modifiability, and visibility. Here, we report a method to detect impurities for at-line process control in water-for-injection (WFI) manufacturing through the example of endotoxins. If a distinct concentration of these amphipathic molecules, originated from gram-negative bacteria, enters the human body, it will result in septic shock, followed by organ failure and possibly death. Every fluid given parenterally is subject to strict regulatory requirements and therefore endotoxin testing. Through use of traditional methods like the limulus amebocyte lysate (LAL) test, it takes more than 2 h to complete. With the presented method, one-fifth of the sample volume is sufficient compared with the LAL test. Once the assay components have been mixed, the result can be interpreted visually within 2 min without the use of further instruments.