Investigation of fungal biomolecules after Low Earth Orbit exposure: a testbed for the next Moon missions.

The Moon is characterized by extremely harsh conditions due to ultraviolet irradiation, wide temperature extremes, vacuum resulting from the absence of an atmosphere and high ionizing radiation. Therefore, its surface may provide a unique platform to investigate the effects of such conditions. For lunar exploration with the Lunar Gateway platform, exposure experiments in Low Earth Orbit are useful testbeds to prepare for lunar space experiments and to understand how and if potential biomarkers are influenced by extra-terrestrial conditions. During the BIOMEX (BIOlogy and Mars EXperiment) project, dried colonies of the fungus Cryomyces antarcticus grown on Lunar Regolith Analogue (LRA) were exposed to space conditions for 16 months aboard the EXPOSE-R2 payload outside the International Space Station. In this study, we investigated the stability/degradation of fungal biomarkers in LRA after exposure to (i) simulated space and (ii) real space conditions, using Raman spectroscopy, gas chromatography-mass spectrometry and DNA amplification. The results demonstrated that fungal biomarkers were detectable after 16 months of real space exposure. This work will contribute to the interpretation of data from future biological experiments in the Cislunar orbit with the Lunar Gateway platform and/or on the lunar surface, in preparation for the next step of human exploration.

Calcium silicate coating derived from Portland cement as treatment for hypersensitive dentine.

OBJECTIVES: To evaluate the in vitro effectiveness on dentine permeability and dentine morphology of a calcium silicate treatment based on Portland cement (DSC). METHODS: The experimental treatment consisted of a calcium silicate paste based on Portland cement that was applied on dentine surface for 3 min. A professional re-mineralizing treatment (GC Tooth Mousse), two in office desensitizing agents (D/Sense Crystal, and By Sealant) and a commercial toothpaste Dentosan S were studied as comparison materials. All materials were applied accordingly with manufacturer directions on wet dentine. The quantitative changes in the hydraulic conductance i.e., permeability through tubules of dentine discs samples produced by treatment were quantified in vitro using a hydrostatic device working at 6.9 kPa. SEM/EDX analyses of dentine were carried out to obtain qualitative information on dentine morphology and surface deposits and to study their relationship with the hydraulic conductance. After treatment, each dentine sample was immersed in artificial saliva and permeability re-evaluated. Finally, each sample was exposed to 0.02 M citric acid solution and the final permeability was assessed. RESULTS: The experimental treatment and both oxalate-based products (D/Sense Crystal and By Sealant) significantly decreased dentine permeability and created crystals and precipitates on the dentine surface that reduced the diameter of dentinal tubules. Artificial saliva immersion and citric acid challenge increased dentine permeability and partially modified the treated surfaces. Dentosan S and GC Tooth Mousse treatments partially reduced dentine permeability and created small amount of precipitates that were removed by saliva immersion and citric acid exposure. EDX revealed the presence of calcium-rich layer after DSC experimental treatment. CONCLUSIONS: The application of the experimental calcium silicate paste and oxalate-based treatments was determined to be effective on dentine permeability reduction and tubules occlusion. The clinical use as desensitizing agent of materials derived from Portland cement as desensitizing agent should be considered for dentine hypersensitivity treatment.