Publications

Chaney H, Zhou Y, Lu K. Understanding SiOC atomic structures via synchrotron X-ray and reactive force field potential studies. Materials Today Chemistry. 2023;29:101429.

Silicon oxycarbide (SiOC) is a unique system that can generate various compositions and microstructures via different polymeric precursors and pyrolysis conditions. However, understanding of the atomic structure evolution, such as cluster formation, phase evolution, and atomic coordination, is lacking. In this study, cluster evolution and atomic coordination for different SiOC ceramics pyrolyzed at 1200 °C and 1500 °C were investigated by high energy X-ray diffraction (HE-XRD) and radial distribution function (RDF) analysis. A new Reactive Force Field (ReaxFF) molecular dynamics modeling approach was developed to understand nanocluster separation and early-stage atomic radial coordination. For the first time, we demonstrate that orthorhombic SiO2 forms and converts to growth resistant amorphous SiO2. Cubic β-SiC also forms at lower temperatures than reported, along with a minor amount of hexagonal SiC that has never been reported. The RDF data support such phase evolution understanding. ReaxFF simulation provides direct data on atomic mixing, elemental separation, and effects of precursor molecular structures and compositions, especially in the early stage of the pyrolysis. The simulated RDF data complement the experimental data, revealing the significant presence of C–H bonds along with Si–O and C–C bonds.

Shishkina V, Kostin A, Volodkin A, et al. The Remodeling of Dermal Collagen Fibrous Structures in Mice under Zero Gravity: The Role of Mast Cells. Int J Mol Sci. 2023;24(3):1939. doi: 10.3390/ijms24031939.

Mechanisms of adaptive rearrangements of the fibrous extracellular matrix of connective tissues under microgravity practically remain unexplored, despite the most essential functions of the stroma existing to ensure the physiological activity of internal organs. Here we analyzed the biomaterial (the skin dermis) of C57BL/6J mice from the Rodent Research-4 experiment after a long stay in space flight. The biomaterial was fixed onboard the International Space Station. It was found that weightlessness resulted in a relative increase in type III collagen-rich fibers compared to other fibrous collagens in the skin. The number of mast cells in the skin did not change, but their secretory activity increased. At the same time, co-localization of mast cells with fibroblasts, as well as impregnated fibers, was reduced. Potential molecular–cellular causes of changes in the activity of fibrillogenesis under zero-gravity conditions and the slowdown of the polymerization of tropocollagen molecules into supramolecular fibrous structures, as well as a relative decrease in the number of fibrous structures with a predominant content of type-I collagen, are discussed. The data obtained evidence of the different sensitivity levels of the fibrous and cellular components of a specific tissue microenvironment of the skin to zero-gravity conditions. The obtained data should be taken into account in the systematic planning of long-term space missions in order to improve the prevention of undesirable effects of weightlessness.

Plis EA, Bengston MT, Engelhart DP, Badura GP, Cowardin HM, Reyes JA, Hoffman RC, Sokolovskiy A, Ferguson DC, Shah JR, Collman S, Scott TR. Ground Testing of the 16th Materials International Space Station Experiment Materials. Journal of Spacecraft and Rockets. 2023;60:.

External spacecraft materials play an important role in satellite protection from the harsh space environment. Research has shown that the physical, chemical, and optical properties of matter change continuously as a result of exposure to solar radiation and aggressive chemical species produced in Earth’s upper atmosphere. Thorough knowledge of the material properties’ evolution throughout a planned mission lifetime helps to improve the reliability of spacecraft. Moreover, the establishment of correlation factors between true space exposure and accelerated space weather experiments at ground facilities enables accurate prediction of on-orbit material performance based on laboratory-based testing. The presented work aims to evaluate the radiation effects of a low-Earth-orbit environment, namely, exposure to the high-energy electrons and atomic oxygen (AO) of heritage and novel spacecraft material selection. The studied materials represent the “flight duplicates” of samples that are launched as a part of the 16th Materials International Space Station Experiment Flight Facility (MISSE-FF) mission in 2022.

Rubin J, van Wijnen AJ, Uzer G. Architectural control of mesenchymal stem cell phenotype through nuclear actin. Nucleus. 2022;13(1):35-48.

There is growing appreciation that architectural components of the nucleus regulate gene accessibility by altering chromatin organization. While nuclear membrane connector proteins link the mechanosensitive actin cytoskeleton to the nucleoskeleton, actin’s contribution to the inner architecture of the nucleus remains enigmatic. Control of actin transport into the nucleus, plus the presence of proteins that control actin structure (the actin tool-box) within the nucleus, suggests that nuclear actin may support biomechanical regulation of gene expression. Cellular actin structure is mechanoresponsive: actin cables generated through forces experienced at the plasma membrane transmit force into the nucleus. We posit that dynamic actin remodeling in response to such biomechanical cues provides a novel level of structural control over the epigenetic landscape. We here propose to bring awareness to the fact that mechanical forces can promote actin transfer into the nucleus and control structural arrangements as illustrated in mesenchymal stem cells, thereby modulating lineage commitment.

Chaney H, Lu K. New findings related to carbothermal reduction of polysiloxane-derived ceramics. Ceramics International. 2023;49:10193-10197.

Carbothermal reduction is the primary mechanism for SiC formation in polymer derived ceramics. However, the specific process involved in the SiOC conversion to SiC and the role of oxygen and carbon are unknown. Using ReaxFF with LAMMPS in a large simulation system containing more than 93 K atoms, this study for the first time shows that O must be removed from SiO2 clusters for SiC formation, providing insights into the carbothermal reduction mechanism. SiO2 regions need to be of a large enough size to induce O reduction. C cluster growth is inversely related to removal of O. This work shows not only the importance of the simulation system size in understanding atomic interactions but also absence of phase separation of SiOC to SiO2. Instead, SiO2 converts to SiC through C diffusion and O removal.

Collman S, Plis EA, Shah JR, Bengston MT, Hoffman RC, Ferguson DC. Operational Procedure for Handling of Spacecraft Materials Sensitive to Atmospheric Exposure. Journal of Spacecraft and Rockets. 2023;60:.

Weng, Yun and Han, Simon and Sekyi, Maria T and Su, Tao and Mattis, Aras N and Chang, Tammy T "Self-Assembled Matrigel-Free iPSC-Derived Liver Organoids Demonstrate Wide-Ranging Highly Differentiated Liver Functions" Stem Cells , v.41 , 2022

Human induced pluripotent stem cell (iPSC)-derived liver organoids serve as models of organogenesis, disease, drug screening, and regenerative medicine. Prevailing methods for generating organoids rely on Matrigel, whose batch-to-batch variability and xenogeneic source pose challenges to mechanistic research and translation to human clinical therapy. In this report, we demonstrate that self-assembled Matrigel-free iPSC-derived organoids developed in rotating wall vessels (RWVs) exhibit greater hepatocyte-specific functions than organoids formed on Matrigel. We show that RWVs produce highly functional liver organoids in part by eliminating the need for Matrigel, which has adverse effects on hepatic lineage differentiation. RWV liver organoids sustain durable function over long-term culture and express a range of mature functional genes at levels comparable to adult human liver, while retaining some fetal features. Our results indicate that RWVs provide a simple and highthroughput way to generate Matrigel-free liver organoids suitable for research and clinical applications.

Chaney H, Lu K. New insight into SiOC atomic structure evolution during early stage of pyrolysis. Journal of the American Ceramic Society. 2023;106:2737-2743.

This study focuses on the early stage of polymer-derived SiOC ceramic conver-sion. We demonstrate that the perceived SiOC phase separation is nonexistent.Instead,SiO2andfreecarbonclustersformfirstandthencarbothermalreductionsets in to induce SiOC formation. Such fundamental understanding is supportedby both synchrotron X-ray diffraction study and reactive force field simulation.Thisworkforthefirsttimeunifiestheunderstandingofatomicevolutionprocessof polysiloxane-based polymer to ceramic conversion.

Enrriques, Ashton E., Sean Howard, Raju Timsina, Nawal K. Khadka, Amber N. Hoover, Allison E. Ray, Ling Ding et al. "Atomic Force Microscopy Cantilever-Based Nanoindentation: Mechanical Property Measurements at the Nanoscale in Air and Fluid." JoVE (Journal of Visualized Experiments) 190 (2022): e64497.

An atomic force microscope (AFM) fundamentally measures the interaction between a nanoscale AFM probe tip and the sample surface. If the force applied by the probe tip and its contact area with the sample can be quantified, it is possible to determine the nanoscale mechanical properties (e.g., elastic or Young's modulus) of the surface being probed. A detailed procedure for performing quantitative AFM cantilever-based nanoindentation experiments is provided here, with representative examples of how the technique can be applied to determine the elastic moduli of a wide variety of sample types, ranging from kPa to GPa. These include live mesenchymal stem cells (MSCs) and nuclei in physiological buffer, resin-embedded dehydrated loblolly pine cross-sections, and Bakken shales of varying composition. Additionally, AFM cantilever-based nanoindentation is used to probe the rupture strength (i.e., breakthrough force) of phospholipid bilayers. Important practical considerations such as method choice and development, probe selection and calibration, region of interest identification, sample heterogeneity, feature size and aspect ratio, tip wear, surface roughness, and data analysis and measurement statistics are discussed to aid proper implementation of the technique. Finally, co-localization of AFM-derived nanomechanical maps with electron microscopy techniques that provide additional information regarding elemental composition is demonstrated.

Walsh JSP, Gorman AC, Salmond W. Visual Displays in Space Station Culture: An Archaeological Analysis. Curr Anthropol. 2021:62(6):804–818. DOI: 10.1086/717778

We offer an archaeological analysis of the visual display of “space heroes” and Orthodox icons in the Russian Zvezda module of the International Space Station (ISS). This study is the first systematic investigation of material culture at a site in space. The ISS has now been continuously inhabited for 20 years. Here, focusing on the period 2000–2014, we use historic imagery from NASA archives to track the changing presence of 78 different items in a single zone. We also explore how ideas about which items are appropriate for display and where to display them originated in earlier Soviet and Russian space stations starting as early as the 1970s. In this way, we identify the emergence and evolution of a particular kind of space station culture with implications for future habitat design.

Vigil C., Daubenspeck A., Coia H., Smith J., Mauzy C. Matrix-Assisted Laser Desorption/Ionization Analysis of the Brain Proteome of Microgravity-Exposed Mice from the International Space Station. Front Space Technol. 2022;3:971229. https://doi.org/10.3389/frspt.2022.971229

Manned spaceflight exposes humans to extreme environmental conditions, including microgravity exposures. The effects of microgravity during spaceflight could lead to changes in brain structure, gene expression, and vascular physiology. Given the known physiological effects, it is highly likely that there are microgravity-initiated proteomic differentials in the brain, possibly domain specific. MALDI-TOF (matrix-assisted laser desorption/ionization time of flight) Imaging Mass Spectrometry allows the visualization of the spatial distribution of highly abundant intact proteins in tissue specimens. This study utilized this technique to visualize global proteomic changes induced by microgravity exposure in brain tissue received from the Rodent Research-1 Center for the Advancement of Science in Space (CASIS)/National Aeronautics and Space Administration (NASA). Proteome profiles were obtained from isolated whole brain tissue from microgravity exposed, Habitat control, and baseline. While a total of 135 mass peaks equating to individual proteins were identified, statistical analysis determined that there were no significant differences in the spectra profiles from the three test groups utilizing this methodology, possibly due to sample collection logistics rather than lack of cellular response.

Yau, Anne and Wang, Zizheng and Ponthempilly, Nadya and Zhang, Yi and Wang, Xueju and Chen, Yupeng "Biosensor integrated tissue chips and their applications on Earth and in space" Biosensors and Bioelectronics , v.222 , 2023

The development of space exploration technologies has positively impacted everyday life on Earth in terms of communication, environmental, social, and economic perspectives. The human body constantly fluctuates during spaceflight, even for a short-term mission. Unfortunately, technology is evolving faster than humans’ ability to adapt, and many therapeutics entering clinical trials fail even after being subjected to vigorous in vivo testing due to toxicity and lack of efficacy. Therefore, tissue chips (also mentioned as organ-on-a-chip) with biosensors are being developed to compensate for the lack of relevant models to help improve the drug development process. There has been a push to monitor cell and tissue functions, based on their biological signals and utilize the integration of biosensors into tissue chips in space to monitor and assess cell microenvironment in real-time. With the collaboration between the Center for the Advancement of Science in Space (CASIS), the National Aeronautics and Space Administration (NASA) and other partners, they are providing the opportunities to study the effects of microgravity environment has on the human body. Institutions such as the National Institute of Health (NIH) and National Science Foundation (NSF) are partnering with CASIS and NASA to utilize tissue chips onboard the International Space Station (ISS). This article reviews the endless benefits of space technology, the development of integrated biosensors in tissue chips and their applications to better understand human biology, physiology, and diseases in space and on Earth, followed by future perspectives of tissue chip applications on Earth and in space.

Rampoldi, Antonio and Forghani, Parvin and Li, Dong and Hwang, Hyun and Armand, Lawrence Christian and Fite, Jordan and Boland, Gene and Maxwell, Joshua and Maher, Kevin and Xu, Chunhui "Space microgravity improves proliferation of human iPSC-derived cardiomyocytes" Stem Cell Reports , v.17 , 2022

In microgravity, cells undergo profound changes in their properties. However, how human cardiac progenitors respond to space microgravity is unknown. In this study, we evaluated the effect of space microgravity on differentiation of human induced pluripotent stem cell (hiPSC)-derived cardiac progenitors compared with 1G cultures on the International Space Station (ISS). Cryopreserved 3D cardiac progenitors were cultured for 3 weeks on the ISS. Compared with 1G cultures, the microgravity cultures had 3-fold larger sphere sizes, 20-fold higher counts of nuclei, and increased expression of proliferation markers. Highly enriched cardiomyocytes generated in space microgravity showed improved Ca2+ handling and increased expression of contraction-associated genes. Short-term exposure (3 days) of cardiac progenitors to space microgravity upregulated genes involved in cell proliferation, survival, cardiac differentiation, and contraction, consistent with improved microgravity cultures at the late stage. These results indicate that space microgravity increased proliferation of hiPSC-cardiomyocytes, which had appropriate structure and function.

Cai, Grace and Nguyen, Anh and Bashirzadeh, Yashar and Lin, Shan-Shan and Bi, Dapeng and Liu, Allen P. "Compressive stress drives adhesion-dependent unjamming transitions in breast cancer cell migration" Frontiers in Cell and Developmental Biology , v.10 , 2022

Cellular unjamming is the collective fluidization of cell motion and has been linked to many biological processes, including development, wound repair, and tumor growth. In tumor growth, the uncontrolled proliferation of cancer cells in a confined space generates mechanical compressive stress. However, because multiple cellular and molecular mechanisms may be operating simultaneously, the role of compressive stress in unjamming transitions during cancer progression remains unknown. Here, we investigate which mechanism dominates in a dense, mechanically stressed monolayer. We find that longterm mechanical compression triggers cell arrest in benign epithelial cells and enhances cancer cell migration in transitions correlated with cell shape, leading us to examine the contributions of cell–cell adhesion and substrate traction in unjamming transitions. We show that cadherin-mediated cell–cell adhesion regulates differential cellular responses to compressive stress and is an important driver of unjamming in stressed monolayers. Importantly, compressive stress does not induce the epithelial–mesenchymal transition in unjammed cells. Furthermore, traction force microscopy reveals the attenuation of traction stresses in compressed cells within the bulk monolayer regardless of cell type and motility. As traction within the bulk monolayer decreases with compressive pressure, cancer cells at the leading edge of the cell layer exhibit sustained traction under compression. Together strengthened intercellular adhesion and attenuation of traction forces within the bulk cell sheet under compression lead to fluidization of the cell layer and may impact collective cell motion in tumor development and breast cancer progression.

Chapron A, Chapron BD, Hailey DW, Chang SY, Imaoka T, Thummel KE, Kelly E, Himmelfarb J, Shen D, Yeung CK. An Improved Vascularized, Dual-Channel Microphysiological System Facilitates Modeling of Proximal Tubular Solute Secretion. ACS Pharmacol Transl Sci. 2020 Jan 28;3(3):496-508.

A vascularized human proximal tubule model in a dual-channel microphysiological system (VPT-MPS) was developed, representing an advance over previous, single-cell-type kidney microphysiological systems. Human proximal tubule epithelial cells (PTECs) and human umbilical vein endothelial cells (HUVECs) were cocultured in side-by-side channels. Over 24 h of coculturing, PTECs maintained polarized expression of Na+/K+ ATPase, tight junctions (ZO-1), and OAT1. HUVECs showed the absence of ZO-1 but expressed endothelial cell marker (CD-31). In time-lapse imaging studies, fluorescein isothiocyanate (FITC)-dextran passed freely from the HUVEC vessel into the supporting extracellular matrix, confirming the leakiness of the endothelium (at 80 min, matrix/intravessel fluorescence ratio = 0.2). Dextran-associated fluorescence accumulated in the matrix adjacent to the basolateral aspect of the PTEC tubule with minimal passage of the compound into the tubule lumen observed (at 80 min, tubule lumen/matrix fluorescence ratio = 0.01). This demonstrates that the proximal tubule compartment is the rate-limiting step in the secretion of compounds in VPT-MPS. In kinetic studies with radiolabeled markers, p-aminohippuric acid (PAH) exhibited greater output into the tubule lumen than did paracellular markers mannitol and FITC-dextran (tubule outflow/vessel outflow concentration ratio of 7.7% vs 0.5 and 0.4%, respectively). A trend toward reduced PAH secretion by 45% was observed upon coadministration of probenecid. This signifies functional expression of renal transporters in PTECs that normally mediate the renal secretion of PAH. The VPT-MPS holds the promise of providing an in vitro platform for evaluating the renal secretion of new drug candidates and investigating the dysregulation of tubular drug secretion in chronic kidney disease.

Williams FA, Nayagam V. Cool-flame dodecane-droplet extinction diameters. Combust Flame. 2020;212:242-244.

Previously published simplified n-alkane cool-flame chemistry is re-evaluated for n-dodecane. Comparison with experimental results produces improved rate-parameter estimates for n-dodecane and indicates deterioration of the simplified chemistry with increasing pressure in predictions of droplet diameters at cool-flame extinction

D. Batcheldor et al 2020 PASP 132 055001

Charge Injection Devices (CIDs) have demonstrated direct contrast ratios in excess of 1:20 million from sub-optimal ground-based astronomical observations. CIDs are therefore interesting prospects for obtaining direct images from a host of high contrast ratio celestial scenes. However, while CIDs are capable of much deeper contrast ratios, potentially exceeding 1:1 billion, they do not address the Inner Working Angle (IWA) problem. If the Point-Spread Function (PSF) of a bright target is not well understood and accounted for, then the IWA will be large and nearby faint objects, like exoplanets, will be challenging to observe regardless of the detector used. As Earth's atmosphere is a major contributor to the variability of a PSF, high contrast ratio imaging with small IWAs will be best achieved in space. Therefore, if CIDs are to be used on future space-telescopes, they must be flight qualified in the space environment and shown to be at the appropriate Technology Readiness Level (TRL). Here we report the results of an 8 months CID technology demonstration mission that used the Nano-Racks External Platform mounted to the Kibo Exposed Facility on-board the International Space Station. Over the course of the 236 days mission we find no significant on-orbit changes of CID performance in terms of dark current, linearity, read noise, and photon transfer efficiency. As a result, CIDs are now space-qualified to TRL-8 and can be considered for future space telescopes.

Manatakis DV, VanDevender A, Manolakos ES. An information-theoretic approach for measuring the distance of organ tissue samples using their transcriptomic signatures [published online ahead of print July 19, 2020]. Bioinformatics. doi: 10.1093/bioinformatics/btaa654

Manatakis DV, VanDevender A, Manolakos ES. An information-theoretic approach for measuring the distance of organ tissue samples using their transcriptomic signatures [published online ahead of print July 19, 2020]. Bioinformatics. doi: 10.1093/bioinformatics/btaa654

Lee S-L, Lehar A, Meir JU, Koch C, Morgan A, Warren LE, Rydzik R, Youngstrom D, Chandok H, George J, Gogain J, Michaud M, Stoklasek T, Liu Y, Germain-Lee EL. Targeting myostatin/activin A protects against skeletal muscle and bone loss during spaceflight. PNAS. 2020;117(38):23942-23951.

Among the physiological consequences of extended spaceflight are loss of skeletal muscle and bone mass. One signaling pathway that plays an important role in maintaining muscle and bone homeostasis is that regulated by the secreted signaling proteins, myostatin (MSTN) and activin A. Here, we used both genetic and pharmacological approaches to investigate the effect of targeting MSTN/activin A signaling in mice that were sent to the International Space Station. Wild type mice lost significant muscle and bone mass during the 33 d spent in microgravity. Muscle weights of Mstn -/- mice, which are about twice those of wild type mice, were largely maintained during spaceflight. Systemic inhibition of MSTN/activin A signaling using a soluble form of the activin type IIB receptor (ACVR2B), which can bind each of these ligands, led to dramatic increases in both muscle and bone mass, with effects being comparable in ground and flight mice. Exposure to microgravity and treatment with the soluble receptor each led to alterations in numerous signaling pathways, which were reflected in changes in levels of key signaling components in the blood as well as their RNA expression levels in muscle and bone. These findings have implications for therapeutic strategies to combat the concomitant muscle and bone loss occurring in people afflicted with disuse atrophy on Earth as well as in astronauts in space, especially during prolonged missions.

Kaplan F, Shapiro-Ilan D, Schiller KC. Dynamics of entomopathogenic nematode foraging and infectivity in microgravity. NPJ Microgravity. 2020;6(20).

Microgravity is a unique environment to elucidate host–parasite biology. Entomopathogenic nematodes (EPNs), model parasites, kill host insects with mutualistic bacteria and provide environmentally friendly pest control. It is unknown how microgravity affects a multistep insect invasion by parasites with mutualistic bacteria. EPNs respond directionally to electromagnetic cues and their sinusoidal locomotion is affected by various physical factors. Therefore, we expected microgravity to impact EPN functionality. Microgravity experiments during space flight on the International Space Station (ISS) indicated that EPNs successfully emerged from consumed insect host cadavers, moved through soil, found and infected bait insects in a manner equivalent to Earth controls. However, nematodes that developed entirely in space, from the egg stage, died upon return to Earth, unlike controls in microgravity and on Earth. This agricultural biocontrol experiment in space gives insight to long-term space flight for symbiotic organisms, parasite biology, and the potential for sustainable crop protection in space.

Jha R, Li D, Wu Q, Ferguson K, Forghani P, Gibson G, Xu C. A long non‐coding RNA GATA6‐AS1 adjacent to GATA6 is required for cardiomyocyte differentiation from human pluripotent stem cells. FASEB J. 2020;34(11):14336-14352.

Long noncoding RNAs (lncRNAs) are crucial in many cellular processes, yet relatively few have been shown to regulate human cardiomyocyte differentiation. Here, we demonstrate an essential role of GATA6 antisense RNA 1 (GATA6‐AS1) in cardiomyocyte differentiation from human pluripotent stem cells (hPSCs). GATA6‐AS1 is adjacent to cardiac transcription factor GATA6. We found that GATA6‐AS1 was nuclear‐localized and transiently upregulated along with GATA6 during the early stage of cardiomyocyte differentiation. The knockdown of GATA6‐AS1 did not affect undifferentiated cell pluripotency but inhibited cardiomyocyte differentiation, as indicated by no or few beating cardiomyocytes and reduced expression of cardiomyocyte‐specific proteins. Upon cardiac induction, the knockdown of GATA6‐AS1 decreased GATA6 expression, altered Wnt‐signaling gene expression, and reduced mesoderm development. Further characterization of the intergenic region between genomic regions of GATA6‐AS1 and GATA6 indicated that the expression of GATA6‐AS1 and GATA6 were regulated by a bidirectional promoter within the intergenic region. Consistently, GATA6‐AS1 and GATA6 were co‐expressed in several human tissues including the heart, similar to the mirror expression pattern of GATA6‐AS1 and GATA6 during cardiomyocyte differentiation. Overall, these findings reveal a previously unrecognized and functional role of lncRNA GATA6‐AS1 in controlling human cardiomyocyte differentiation.

Zhang J, Muller BSF, Tyre KN, Hersh HL, Bai F, Hu Y, Resende MFR, Rathinasabapathi B, Settles AM. Competitive Growth Assay of Mutagenized Chlamydomonas reinhardtii Compatible with the International Space Station Veggie Plant Growth Chamber. Front Plant Sci. 2020, May 25;11:631.

A biological life support system for spaceflight would capture carbon dioxide waste produced by living and working in space to generate useful organic compounds. Photosynthesis is the primary mechanism to fix carbon into organic molecules. Microalgae are highly efficient at converting light, water, and carbon dioxide into biomass, particularly under limiting, artificial light conditions that are a necessity in space photosynthetic production. Although there is great promise in developing algae for chemical or food production in space, most spaceflight algae growth studies have been conducted on solid agar-media to avoid handling liquids in microgravity. Here we report that breathable plastic tissue culture bags can support robust growth of Chlamydomonas reinhardtii in the Veggie plant growth chamber, which is used on the International Space Station (ISS) to grow terrestrial plants. Live cultures can be stored for at least 1 month in the bags at room temperature. The gene set required for growth in these photobioreactors was tested using a competitive growth assay with mutations induced by short-wave ultraviolet light (UVC) mutagenesis in either wild-type (CC-5082) or cw15 mutant (CC-1883) strains at the start of the assay. Genome sequencing identified UVC-induced mutations, which were enriched for transversions and non-synonymous mutations relative to natural variants among laboratory strains. Genes with mutations indicating positive selection were enriched for information processing genes related to DNA repair, RNA processing, translation, cytoskeletal motors, kinases, and ABC transporters. These data suggest that modification of DNA repair, signal transduction, and metabolite transport may be needed to improve growth rates in this spaceflight production system.

Lee E, Luo T. Long-distance Optical Pulling of Nanoparticle in a Low Index Cavity Using a Single Plane Wave. Sci Adv. 2020 May 20;6(21):3646.

Optical pulling force (OPF) can make a nanoparticle (NP) move against the propagation direction of the incident light. Long-distance optical pulling is highly desired for nano-object manipulation, but its realization remains challenging. We propose an NP-in-cavity structure that can be pulled by a single plane wave to travel long distances when the spherical cavity wrapping the NP has a refractive index lower than the medium. An electromagnetic multipole analysis shows that NPs made of many common materials can receive the OPF inside a lower index cavity. Using a silica-Au core-shell NP that is encapsulated by a plasmonic nanobubble, we experimentally demonstrate that a single laser can pull the Au NP-in-nanobubble structure for ~0.1 mm. These results may lead to practical applications that can use the optical pulling of NP, such as optically driven nanostructure assembly and nanoswimmers.

Lee E, Huang D, Luo, T. Ballistic Supercavitating Nanoparticles Driven by Single Gaussian Beam Optical Pushing and Pulling Forces. Nat Commun. 2020;11:2404.

Directed high-speed motion of nanoscale objects in fluids can have a wide range of applications like molecular machinery, nano robotics, and material assembly. Here, we report ballistic plasmonic Au nanoparticle (NP) swimmers with unprecedented speeds (~336,000 μm s-1) realized by not only optical pushing but also pulling forces from a single Gaussian laser beam. Both the optical pulling and high speeds are made possible by a unique NP-laser interaction. The Au NP excited by the laser at the surface plasmon resonance peak can generate a nanoscale bubble, which can encapsulate the NP (i.e., supercavitation) to create a virtually frictionless environment for it to move, like the Leidenfrost effect. Certain NP-in-bubble configurations can lead to the optical pulling of NP against the photon stream. The demonstrated ultra-fast, light-driven NP movement may benefit a wide range of nano- and bio-applications and provide new insights to the field of optical pulling force.

Smith RC, Cramer MS, Mitchell PJ, Lucchesi J, Ortega AM, Livingston EW, Ballard D, Zhang L, Hanson J, Barton K, Berens S, Credille KM, Bateman TA, Ferguson VL, Ma YL, Stodieck LS. Inhibition of myostatin prevents microgravity-induced loss of skeletal muscle mass and strength. PLoS ONE. 2020;15(4):e0230818.

The microgravity conditions of prolonged spaceflight are known to result in skeletal muscle atrophy that leads to diminished functional performance. To assess if inhibition of the growth factor myostatin has potential to reverse these effects, mice were treated with a myostatin antibody while housed on the International Space Station. Grip strength of ground control mice increased 3.1% compared to baseline values over the 6 weeks of the study, whereas grip strength measured for the first time in space showed flight animals to be -7.8% decreased in strength compared to baseline values. Control mice in space exhibited, compared to ground-based controls, a smaller increase in DEXA-measured muscle mass (+3.9% vs +5.6% respectively) although the difference was not significant. All individual flight limb muscles analyzed (except for the EDL) weighed significantly less than their ground counterparts at the study end (range -4.4% to -28.4%). Treatment with myostatin antibody YN41 was able to prevent many of these space-induced muscle changes. YN41 was able to block the reduction in muscle grip strength caused by spaceflight and was able to significantly increase the weight of all muscles of flight mice (apart from the EDL). Muscles of YN41-treated flight mice weighed as much as muscles from Ground IgG mice, with the exception of the soleus, demonstrating the ability to prevent spaceflight-induced atrophy. Muscle gene expression analysis demonstrated significant effects of microgravity and myostatin inhibition on many genes. Gamt and Actc1 gene expression was modulated by microgravity and YN41 in opposing directions. Myostatin inhibition did not overcome the significant reduction of microgravity on femoral BMD nor did it increase femoral or vertebral BMD in ground control mice. In summary, myostatin inhibition may be an effective countermeasure to detrimental consequences of skeletal muscle under microgravity conditions.