Pokročilé instrumentace a metody pro charakterizace materiálů
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- ItemApparent Young´s modulus of human cranial cancellous bone(Institute of Theoretical and Applied Mechanics of the Czech Academy of Sciences, 2024-05-14) Votava, Tomáš; Marcián, Petr; Borák, Libor; Fuis, Vladimír; Zikmund, Tomáš; Kaiser, Jozef; Wolff, JanThis study investigates the biomechanical behavior of cancellous bone in the os occipitale through finite element modeling. Utilizing micro-computed tomography scans, 47 bone segments were analyzed, and their apparent Young's moduli of each segment were determined in three orthogonal directions. The results revealed strong directional dependencies of Young’s modulus on bone volume fractions. In contrast, nondirectional dependency exhibited a weaker correlation, indicating an orthotropic elasticity. The derived correlation equations offer an efficient means to describe cancellous bone in cranial biomechanical simulations, especially when a detailed trabecular representation is impractical.
- ItemRaman microspectroscopy and laser-induced breakdown spectroscopy for the analysis of polyethylene microplastics in human soft tissues(CELL PRESS, 2024-09-30) Parobková, Viktória; Holub, Daniel; Kizovský, Martin; Kalčíková, Gabriela; Rozman, Ula; Urík, Milan; Novotný, Karel; Samek, Ota; Zikmund, Tomáš; Pořízka, Pavel; Kaiser, JozefPeople are exposed to microplastics (MPs) on a large scale in everyday life. However, it is not clear whether MPs can also be distributed and retained in certain tissues. Therefore, the development of analytical methods capable of detecting MPs in specific human organs/tissues is of utmost importance. In this study, the use and combination of spectroscopic techniques, namely Raman microspectroscopy and laser-induced breakdown spectroscopy (LIBS), was tested for the detection of polyethylene (PE) MPs in human tonsils. Preliminary results showed that Raman microspectroscopy was able to detect MPs down to 1 mu m in size and LIBS down to 10 mu m. In the next step, human tonsils were spiked with PE MPs, and digested. The filtered particles were analyzed using Raman microspectroscopy and LIBS, and complemented by X-ray fluorescence (XRF). The results showed that Raman microspectroscopy could reliably detect PE MPs in spiked human tonsils, while LIBS and XRF served as a reference analytical method to characterize particles that could not be classified by Raman microspectroscopy for their non-organic origin. The results of this study, supported by a current feasibility study conducted on clinical samples, demonstrated the reliability and feasibility of this approach for monitoring MPs in biotic samples.
- ItemInvestigating the effects of laser wavelengths and other ablation parameters on the detection of biogenic elements and contaminants in hydroxyapatite(ROYAL SOC CHEMISTRY, 2024-08-28) Fazlić, Aida; Faruzelová, Anna; Buday, Jakub; Michlovská, Lenka; Vojtová, Lucy; Modlitbová, Pavlína; Pořízka, Pavel; Kaiser, JozefThe main purpose of this work is to thoroughly describe sensitivity and resolution enhancement by systematically optimizing key parameters in laser-induced breakdown spectroscopy analysis. Simultaneous analysis of biogenic (C, P, Mg, and Ca) and contaminating (Pb) elements, which are commonly detected in selected biotic matrices (mammal teeth), was performed. Hydroxyapatite reference pellets were utilized as model matrices, which successfully reflect human dental tissue. The optimization involved precise adjustments of the used laser wavelengths (1064, 532, and 266 nm), relative defocus of the laser pulse, ablation pulse energies, and gate delays for collecting characteristic spectra. In addition, for Ca analysis, the signals of different ionization line types (Ca I 364.44 nm; Ca II 370.60 and 396.85 nm) were compared; in the case of Pb analysis, the limits of detection were established for each used laser wavelength, and the revealed differences were discussed in detail. We intend to demonstrate the benefits of rapid, low-cost analysis and also the importance of measurement parameters used in biotic sample testing. A comparison of laser ablation measurement parameters (laser wavelength, energy, gate delay, defocus, and spot size) to determine optimal settings for the detection of heavy metals and biogenic elements in a hard tissue matrix (hydroxyapatite).
- ItemFabrication of customized open-cell titanium foams by direct foaming for biomedical applications(ELSEVIER, 2024-11-01) Oliver Urrutia, Carolina; Casas Luna, Mariano; Koledová, Zuzana; Slámečka, Karel; Zikmund, Tomáš; Kaiser, Jozef; Čelko, Ladislav; Montufar Jimenez, Edgar BenjaminTitanium (Ti) foams offer a promising alternative for bone reconstruction and repair due to their high porosity and lower stiffness compared to solid metals, which improves in vivo osseointegration by reducing the stress shielding effect and allowing bone ingrowth. In this work, customized Ti foams were successfully fabricated for the first time at room temperature using a direct foaming method. Ti powder suspension with a water-soluble surfactant and environmentally friendly thickener was foamed by mechanical stirring. Then, 3D-printed moulds were utilized to achieve near-net shape foams, which were subsequently consolidated by sintering, thus avoiding the need for complex processing of molten Ti. The resulting Ti foams exhibited a cancellous-like open-cell structure, high porosity (> 80%), and a five times higher effective surface area than a 3D Ti mesh with a primitive cubic-based cell fabricated by additive manufacturing. In addition, the Ti foams exhibited similar mechanical properties to cancellous bone and facilitated the adhesion, proliferation, and maturation of human osteoblasts in vitro.
- ItemThe level of protein in the maternal murine diet modulates the facial appearance of the offspring via mTORC1 signaling(NATURE PORTFOLIO, 2024-03-26) Xie, Meng; Kaiser, Markéta; Gershtein, Yaakov; Schnyder, Daniela; Deviatiiarov, Ruslan; Gazizova, Guzel; Shagimardanova, Elena; Zikmund, Tomáš; Kerckhofs, Greet; Ivashkin, Evgeny; Batkovskyte, Dominyka; Newton, Phillip T.; Andersson, Olov; Fried, Kaj; Gusev, Oleg; Zeberg, Hugo; Kaiser, Jozef; Adameyko, Igor; Chagin, Andrei S.The development of craniofacial skeletal structures is fascinatingly complex and elucidation of the underlying mechanisms will not only provide novel scientific insights, but also help develop more effective clinical approaches to the treatment and/or prevention of the numerous congenital craniofacial malformations. To this end, we performed a genome-wide analysis of RNA transcription from non-coding regulatory elements by CAGE-sequencing of the facial mesenchyme of human embryos and cross-checked the active enhancers thus identified against genes, identified by GWAS for the normal range human facial appearance. Among the identified active cis-enhancers, several belonged to the components of the PI3/AKT/mTORC1/autophagy pathway. To assess the functional role of this pathway, we manipulated it both genetically and pharmacologically in mice and zebrafish. These experiments revealed that mTORC1 signaling modulates craniofacial shaping at the stage of skeletal mesenchymal condensations, with subsequent fine-tuning during clonal intercalation. This ability of mTORC1 pathway to modulate facial shaping, along with its evolutionary conservation and ability to sense external stimuli, in particular dietary amino acids, indicate that the mTORC1 pathway may play a role in facial phenotypic plasticity. Indeed, the level of protein in the diet of pregnant female mice influenced the activity of mTORC1 in fetal craniofacial structures and altered the size of skeletogenic clones, thus exerting an impact on the local geometry and craniofacial shaping. Overall, our findings indicate that the mTORC1 signaling pathway is involved in the effect of environmental conditions on the shaping of craniofacial structures. Children's faces resemble their parents to various degrees. Here they show that the maternal diet affects the facial appearances of newborns and that inherited and adaptive mechanisms sculpturing facial bones are linked via dietary protein levels and the mTOR signaling pathway.