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Journal of Biomedical Materials... Mar 2024Sponge-like materials made from regenerated silk fibroin biopolymers are a tunable and advantageous platform for in vitro engineered tissue culture and in vivo tissue...
Sponge-like materials made from regenerated silk fibroin biopolymers are a tunable and advantageous platform for in vitro engineered tissue culture and in vivo tissue regeneration. Anisotropic, three-dimensional (3D) silk fibroin sponge-like scaffolds can mimic the architecture of contractile muscle. Herein, we use silk fibroin solution isolated from the cocoons of Bombyx mori silkworms to form aligned sponges via directional ice templating in a custom mold with a slurry of dry ice and ethanol. Hydrated tensile mechanical properties of these aligned sponges were evaluated as a function of silk polymer concentration (3% or 5%), freezing time (50% or 100% ethanol), and post-lyophilization method for inducing crystallinity (autoclaving, water annealing). Hydrated static tensile tests were used to determine Young's modulus and ultimate tensile strength across sponge formulations at two strain rates to evaluate rate dependence in the calculated parameters. Results aligned with previous reports in the literature for isotropic silk fibroin sponge-like scaffolds, where the method by which beta-sheets were formed and level of beta-sheet content (crystallinity) had the greatest impact on static parameters, while polymer concentration and freezing rate did not significantly impact static mechanical properties. We estimated the crystalline organization using molecular dynamics simulations to show that larger crystalline regions may be responsible for strength at low strain amplitudes and brittleness at high strain amplitudes in the autoclaved sponges. Within the parameters evaluated, extensional Young's modulus is tunable in the range of 600-2800 kPa. Dynamic tensile testing revealed the linear viscoelastic region to be between 0% and 10% strain amplitude and 0.2-2 Hz frequencies. Long-term stability was evaluated by hysteresis and fatigue tests. Fatigue tests showed minimal change in the storage and loss modulus of 5% silk fibroin sponges for more than 6000 min of continuous mechanical stimulation in the linear regime at 10% strain amplitude and 1 Hz frequency. Furthermore, we confirmed that these mechanical properties hold when decellularized extracellular matrix is added to the sponges and when the mechanical property assessments were performed in cell culture media. We also used nano-computed tomography (nano-CT) and simulations to explore pore interconnectivity and tortuosity. Overall, these results highlight the potential of anisotropic, sponge-like silk fibroin scaffolds for long-term (>6 weeks) contractile muscle culture with an in vitro bioreactor system that provides routine mechanical stimulation.
PubMed: 38469675
DOI: 10.1002/jbm.a.37703 -
Small (Weinheim An Der Bergstrasse,... Mar 2024Hydrogels are currently in the limelight for applications in soft electronics but they suffer from the tendency to lose water or freeze when exposed to dry environments...
Hydrogels are currently in the limelight for applications in soft electronics but they suffer from the tendency to lose water or freeze when exposed to dry environments or low temperatures. Molecular crowding is a prevalent occurrence in living cells, in which molecular crowding agents modify the hydrogen bonding structure, causing a significant reduction in water activity. Here, a wide-humidity range applicable, anti-freezing, and robust hydrogel is developed through the incorporation of natural amino acid proline (Pro) and conductive MXene into polyvinyl alcohol (PVA) hydrogel networks. Theoretical calculations reveal that Pro can transform "free water" into "locked water" via the molecular-crowding effect, thereby suppressing water evaporation and ice forming. Accordingly, the prepared hydrogel exhibits high water retention capability, with 77% and 55% being preserved after exposure to 20 °C, 28% relative humidity (RH) and 35 °C, 90% RH for 12 h. Meanwhile, Pro lowers the freezing temperature of the hydrogel to 34 °C and enhances its stretchability and strength. Finally, the PVA/Pro/MXene hydrogels are assembled as multifunctional on-skin strain sensors and conductive electrodes to monitor human motions and detect tiny electrophysiological signals. Collectively, this work provides a molecular crowding strategy that will motivate researchers to develop more advanced hydrogels for versatile applications.
PubMed: 38431936
DOI: 10.1002/smll.202400161 -
Scientific Reports Mar 2024Land use change and atmospheric composition, two drivers of climate change, can interact to affect both local and remote climate regimes. Previous works have considered...
Land use change and atmospheric composition, two drivers of climate change, can interact to affect both local and remote climate regimes. Previous works have considered the effects of greenhouse gas buildup in the atmosphere and the effects of Amazon deforestation in atmospheric general circulation models. In this study, we investigate the impacts of the Brazilian Amazon savannization and global warming in a fully coupled ocean-land-sea ice-atmosphere model simulation. We find that both savannization and global warming individually lengthen the dry season and reduce annual rainfall over large tracts of South America. The combined effects of land use change and global warming resulted in a mean annual rainfall reduction of 44% and a dry season length increase of 69%, when averaged over the Amazon basin, relative to the control run. Modulation of inland moisture transport due to savannization shows the largest signal to explain the rainfall reduction and increase in dry season length over the Amazon and Central-West. The combined effects of savannization and global warming resulted in maximum daily temperature anomalies, reaching values of up to 14 °C above the current climatic conditions over the Amazon. Also, as a consequence of both climate drivers, both soil moisture and surface runoff decrease over most of the country, suggesting cascading negative future impacts on both agriculture production and hydroelectricity generation.
PubMed: 38429332
DOI: 10.1038/s41598-024-55176-5 -
Acta Medica Okayama Feb 2024Ice bags are frequently used in medical care settings for pain relief, comfort, and in some cases, whole-body cooling. This study quantifies heat energy transfer...
Ice bags are frequently used in medical care settings for pain relief, comfort, and in some cases, whole-body cooling. This study quantifies heat energy transfer capacity of ice bags and evaluates their cooling effects on body temperature. Forty-eight healthy adults in their 20s were recruited. An ice bag wrapped in two layers of dry towel was applied to the forehead, neck, or palm of each participant for 10 min. The skin surface temperature, heat flow, and core temperature were recorded during the cooling and non-cooling periods, with energy transfer calculated by integrating heat flow over time. Over the non-cooling period, 31.4-53.6 kJ·m-2 of energy was dissipated over 10 min, whereas during the cooling period, the range increased to 180.0-218.7 kJ·m-2 over 10 min. Skin surface temperature decreased by 3.2-5.7°C, whereas core temperature was unchanged. Ice bag use augmented energy transfer by about 150-180 kJ·m-2 over 10 min, but this was insufficient for rapid whole body cooling due to the small skin-surface area in contact with the ice bag. The measured energy transfer indicated that topical ice bag application absorbs insufficient energy to affect core temperature. Quantitative assessment of energy transfer was shown to inform the safe and appropriate use of thermotherapy.
Topics: Adult; Humans; Hot Temperature; Temperature; Cold Temperature
PubMed: 38419315
DOI: 10.18926/AMO/66671 -
Vaccines Feb 2024The simultaneous administration of SARS-CoV-2 and influenza vaccines is being carried out for the first time in the UK and around the globe in order to mitigate the...
The simultaneous administration of SARS-CoV-2 and influenza vaccines is being carried out for the first time in the UK and around the globe in order to mitigate the health, economic, and societal impacts of these respiratory tract diseases. However, a systematic approach for planning the vaccine distribution and administration aspects of the vaccination campaigns would be beneficial. This work develops a novel multi-product mixed-integer linear programming (MILP) vaccine supply chain model that can be used to plan and optimise the simultaneous distribution and administration of SARS-CoV-2 and influenza vaccines. The outcomes from this study reveal that the total budget required to successfully accomplish the SARS-CoV-2 and influenza vaccination campaigns is equivalent to USD 7.29 billion, of which the procurement costs of SARS-CoV-2 and influenza vaccines correspond to USD 2.1 billion and USD 0.83 billion, respectively. The logistics cost is equivalent to USD 3.45 billion, and the costs of vaccinating individuals, quality control checks, and vaccine shipper and dry ice correspond to USD 1.66, 0.066, and 0.014, respectively. The analysis of the results shows that the choice of rolling out the SARS-CoV-2 vaccine during the vaccination campaign can have a significant impact not only on the total vaccination cost but also on vaccine wastage rate.
PubMed: 38400141
DOI: 10.3390/vaccines12020158 -
Therapeutic Hypothermia and Temperature... Mar 2024The study subject was a healthy, 47-year-old man, a low temperature Guinness World Record holder. He spent 50 days alone in Rovaniemi, Lapland, and functioned in the...
The study subject was a healthy, 47-year-old man, a low temperature Guinness World Record holder. He spent 50 days alone in Rovaniemi, Lapland, and functioned in the ambient temperature ranging from +2°C to -37°C. He did not use sources of heat, he did not eat warm meals or drink hot water, and did not dry his clothes. He slept in an igloo, on an ice cover of 20-30 cm. He spent 10 hours a day in a sleeping bag and for the remaining time he walked, skied, or rode a bicycle, and practiced swimming. The aim of the study was a laboratory assessment of renal capacity in a man exposed to long-term extremely low ambient temperatures. The study was approved by the Ethical Committee at the Regional Medical Chamber in Krakow, Poland (approval No.: 194/KBL/OIL/2019). Twice during the observation, urine and blood were collected and analyzed: before and after the prolonged exposure to extremely low ambient temperatures. Changes were seen in many blood and urine parameters, but in urine, they were more significant. In urine, decreased values of sodium (by 53.9%), potassium (by 22.6%), creatinine (by 65.5%), urea (by 61.3%), uric acid (by 58.4%), and protein (by 50%) were observed. Neutrophil gelatinase-associated lipocalin (NGAL) increased by 34%. Absence of calcium oxalate excretion was reported relative to the value before the exposure to cold. In blood, increased values of interleukin-6 (by 60%) and β-2-microglobulin (by 26.9%) were observed. Erythropoietin decreased by 22.4%. No changes were noted in estimated glomerular filtration rate. The study subject lost 10 kg in weight. On the basis of the results obtained during the observation, it can be determined that the probable cause of changes in the laboratory results of the subject was the diet used, and not a dysfunction of the excretory system. The body weight loss and activation of compensating mechanisms focused on saving vitally important diet components, caused by the insufficient diet, exclude the theory of a negative effect of exposure to extremely low temperatures on renal filtration function.
Topics: Male; Humans; Middle Aged; Temperature; Hypothermia, Induced; Kidney; Cold Temperature; Calcium Oxalate; Biomarkers
PubMed: 38394138
DOI: 10.1089/ther.2023.0086 -
Applied and Environmental Microbiology Mar 2024The ice-free McMurdo Dry Valleys of Antarctica are dominated by nutrient-poor mineral soil and rocky outcrops. The principal habitat for microorganisms is within rocks...
The ice-free McMurdo Dry Valleys of Antarctica are dominated by nutrient-poor mineral soil and rocky outcrops. The principal habitat for microorganisms is within rocks (endolithic). In this environment, microorganisms are provided with protection against sub-zero temperatures, rapid thermal fluctuations, extreme dryness, and ultraviolet and solar radiation. Endolithic communities include lichen, algae, fungi, and a diverse array of bacteria. is among the most abundant bacterial phyla present in these communities. Among the are four novel classes of bacteria, here named Spiritibacteria class. nov. (=UBA5177), Martimicrobia class. nov. (=UBA4733), Tarhunnaeia class. nov. (=UBA6077), and Uliximicrobia class. nov. (=UBA2235). We retrieved 17 high-quality metagenome-assembled genomes (MAGs) that represent these four classes. Based on genome predictions, all these bacteria are inferred to be aerobic heterotrophs that encode enzymes for the catabolism of diverse sugars. These and other organic substrates are likely derived from lichen, algae, and fungi, as metabolites (including photosynthate), cell wall components, and extracellular matrix components. The majority of MAGs encode the capacity for trace gas oxidation using high-affinity uptake hydrogenases, which could provide energy and metabolic water required for survival and persistence. Furthermore, some MAGs encode the capacity to couple the energy generated from H and CO oxidation to support carbon fixation (atmospheric chemosynthesis). All encode mechanisms for the detoxification and efflux of heavy metals. Certain MAGs encode features that indicate possible interactions with other organisms, such as Tc-type toxin complexes, hemolysins, and macroglobulins.IMPORTANCEThe ice-free McMurdo Dry Valleys of Antarctica are the coldest and most hyperarid desert on Earth. It is, therefore, the closest analog to the surface of the planet Mars. Bacteria and other microorganisms survive by inhabiting airspaces within rocks (endolithic). We identify four novel classes of phylum , and, based on interrogation of 17 metagenome-assembled genomes, we predict specific metabolic and physiological adaptations that facilitate the survival of these bacteria in this harsh environment-including oxidation of trace gases and the utilization of nutrients (including sugars) derived from lichen, algae, and fungi. We propose that such adaptations allow these endolithic bacteria to eke out an existence in this cold and extremely dry habitat.
Topics: Antarctic Regions; Bacteria; Fungi; Chloroflexi; Cold Temperature; Sugars
PubMed: 38372512
DOI: 10.1128/aem.02264-23 -
Clinical Biochemistry Mar 2024An analytical benchmark for high-sensitivity cardiac troponin (hs-cTn) assays is to achieve a coefficient of variation (CV) of ≤ 10.0 % at the 99th percentile upper...
BACKGROUND
An analytical benchmark for high-sensitivity cardiac troponin (hs-cTn) assays is to achieve a coefficient of variation (CV) of ≤ 10.0 % at the 99th percentile upper reference limit (URL) used for the diagnosis of myocardial infarction. Few prospective multicenter studies have evaluated assay imprecision and none have determined precision at the female URL which is lower than the male URL for all cardiac troponin assays.
METHODS
Human serum and plasma matrix samples were constructed to yield hs-cTn concentrations near the female URLs for the Abbott, Beckman, Roche, and Siemens hs-cTn assays. These materials were sent (on dry ice) to 35 Canadian hospital laboratories (n = 64 instruments evaluated) participating in a larger clinical trial, with instructions for storage, handling, and monthly testing over one year. The mean concentration, standard deviation, and CV for each instrument type and an overall pooled CV for each manufacturer were calculated.
RESULTS
The CVs for all individual instruments and overall were ≤ 10.0 % for two manufacturers (Abbott CV = 6.3 % and Beckman CV = 7.0 %). One of four Siemens Atellica instruments yielded a CV > 10.0 % (CV = 7.7 %), whereas 15 of 41 Roche instruments yielded CVs > 10.0 % at the female URL of 9 ng/L used worldwide (6 cobas e411, 1 cobas e601, 4 cobas e602, and 4 cobas e801) (CV = 11.7 %). Four Roche instruments also yielded CVs > 10.0 % near the female URL of 14 ng/L used in the United States (CV = 8.5 %).
CONCLUSIONS
The number of instruments achieving a CV ≤ 10.0 % at the female 99th-percentile URL varies by manufacturer and by instrument. Monitoring assay precision at the female URL is necessary for some assays to ensure optimal use of this threshold in clinical practice.
Topics: Humans; Male; Female; Prospective Studies; Canada; Myocardial Infarction; Biological Assay; Troponin; Troponin T; Biomarkers; Reference Values
PubMed: 38360198
DOI: 10.1016/j.clinbiochem.2024.110731 -
Langmuir : the ACS Journal of Surfaces... Feb 2024Fluid-infused (or swollen) elastomers are known for their antiadhesive properties. The presence of excess fluid at their surface is the main contributor to limiting...
Fluid-infused (or swollen) elastomers are known for their antiadhesive properties. The presence of excess fluid at their surface is the main contributor to limiting contact formation and minimizing adhesion. Despite their potential, the mechanisms for adhesion and contact aging to fluid-infused elastomers are poorly understood beyond contact with a few materials (ice, biofilms, glass). This study reports on adhesion to a model fluid-infused elastomer, poly(dimethylsiloxane) (PDMS), swollen with silicone oil. The effects of oil saturation, contact time, and the opposing surface are investigated. Specifically, adhesion to two different adherents with comparable surface energies but drastically different mechanical properties is investigated: a glass surface and a soft viscoelastic acrylic pressure-sensitive adhesive film (PSA, modulus ∼25 kPa). Adhesion between the PSA and swollen PDMS [with 23% (w/w) silicone oil] retains up to 60% of its value compared to contact with unswollen (dry) PDMS. In contrast, adhesion to glass nearly vanishes in contact with the same swollen elastomer. Adhesion to the PSA also displays stronger contact aging than adhesion to glass. Contact aging with the PSA is comparable for dry and unsaturated PDMS. Moreover, load relaxation when the PSA is in contact with the PDMS does not correlate with contact aging for contact with the dry or unsaturated elastomer, suggesting that contact aging is likely caused by chain interpenetration and polymer reorganization within the contact region. Closer to full saturation of the PDMS with oil, adhesion to the PSA decreases significantly and shows a delay in the onset of contact aging that is weakly correlated to the poroelastic relaxation of the elastomer. Additional confocal imaging suggests that the presence of a layer of fluid trapped at the interface between the two solids could explain the delayed (and limited) contact aging to the oil-saturated PDMS.
PubMed: 38359377
DOI: 10.1021/acs.langmuir.3c03413 -
Nature Feb 2024Late Pleistocene ice-age climates are routinely characterized as having imposed moisture stress on low- to mid-latitude ecosystems. This idea is largely based on fossil...
Late Pleistocene ice-age climates are routinely characterized as having imposed moisture stress on low- to mid-latitude ecosystems. This idea is largely based on fossil pollen evidence for widespread, low-biomass glacial vegetation, interpreted as indicating climatic dryness. However, woody plant growth is inhibited under low atmospheric CO (refs. ), so understanding glacial environments requires the development of new palaeoclimate indicators that are independent of vegetation. Here we show that, contrary to expectations, during the past 350 kyr, peaks in southern Australian climatic moisture availability were largely confined to glacial periods, including the Last Glacial Maximum, whereas warm interglacials were relatively dry. By measuring the timing of speleothem growth in the Southern Hemisphere subtropics, which today has a predominantly negative annual moisture balance, we developed a record of climatic moisture availability that is independent of vegetation and extends through multiple glacial-interglacial cycles. Our results demonstrate that a cool-moist response is consistent across the austral subtropics and, in part, may result from reduced evaporation under cool glacial temperatures. Insofar as cold glacial environments in the Southern Hemisphere subtropics have been portrayed as uniformly arid, our findings suggest that their characterization as evolutionary or physiological obstacles to movement and expansion of animal, plant and, potentially, human populations should be reconsidered.
Topics: Animals; Humans; Animal Migration; Australia; Cold Temperature; Desert Climate; Ecosystem; History, Ancient; Humidity; Ice Cover; Plants; Pollen; Volatilization
PubMed: 38326596
DOI: 10.1038/s41586-023-06989-3