Implementation of Different Conversion/Alloy Active Materials as Anodes for Lithium-Based Solid-State Batteries.

To complement or outperform lithium-ion batteries with liquid electrolyte as energy storage devices, a high-energy as well as high-power anode material must be used in solid-state batteries. An overlooked class of anode materials is the one of conversion/alloy active materials (e.g., SnO2, which is already extensively studied in liquid electrolyte-based batteries). Conversion/alloy active materials offer high specific capacities and often also fast lithium-ion diffusion and reaction kinetics, which are required for high C-rates and application in high-energy and high-power devices such as battery electric vehicles. To date, there are only very few reports on conversion/alloy active materials─namely, SnO2─as anode material in sulfide-based solid-state batteries, with a relatively complex electrode design. Otherwise, conversion-alloy active materials are used as a seed layer or interlayer for a homogeneous Li deposition or to mitigate the formation and growth of the SEI, respectively. Within this work, four different conversion/alloy active materials─SnO2, Sn0.9Fe0.1O2, ZnO, and Zn0.9Fe0.1O─are synthesized and incorporated as negative active materials ("anodes") in composite electrodes into SSBs with Li6PS5Cl as solid electrolyte. The structure and the microstructure of the as-synthesized active materials and composite electrodes are investigated by XRD, SEM, and FIB-SEM. All active materials are evaluated based on their C-rate performance and long-term cyclability by galvanostatic cycling under a constant pressure of 40 MPa. Furthermore, light is shed on the degradation processes that take place at the interface between the active material and solid electrolyte. It is evidenced that the decomposition of Li6PS5Cl to LiCl, Li2S, and Li3P at the anode is amplified by Fe substitution. Lastly, a 2D sheet electrode is designed and cycled to tackle the interfacial degradation processes. This approach leads to an improved C-rate performance (factor of 3) as well as long-term cyclability (factor of 2.3).

Lipid-related ion suppression on the herbicide atrazine in earthworm samples in ToF-SIMS and matrix-assisted laser desorption ionization mass spectrometry imaging and the role of gas-phase basicity.

In mass spectrometry imaging (MSI), ion suppression can lead to a misinterpretation of results. Particularly phospholipids, most of which exhibit high gas-phase basicity (GB), are known to suppress the detection of metabolites and drugs. This study was initiated by the observation that the signal of an herbicide, i.e., atrazine, was suppressed in MSI investigations of earthworm tissue sections. Herbicide accumulation in earthworms was investigated by time-of-flight secondary ion mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). Additionally, earthworm tissue sections without accumulation of atrazine but with a homogeneous spray deposition of the herbicide were analyzed to highlight region-specific ion suppression. Furthermore, the relationship of signal intensity and GB in binary mixtures of lipids, amino acids, and atrazine was investigated in both MSI techniques. The GB of atrazine was determined experimentally through a linear plot of the obtained intensity ratios of the binary amino acid mixtures, as well as theoretically. The GBs values for atrazine of 896 and 906 kJ/mol in ToF-SIMS and 933 and 987 kJ/mol in MALDI-MSI were determined experimentally and that of 913 kJ/mol by quantum mechanical calculations. Compared with the GB of a major lipid component, phosphatidylcholine (GBPC = 1044.7 kJ/mol), atrazine's experimentally and computationally determined GBs in this work are significantly lower, making it prone to ion suppression in biological samples containing polar lipids.

Benchmarking of Coatings for Cathode Active Materials in Solid-State Batteries Using Surface Analysis and Reference Electrodes.

Fast and reliable evaluation of degradation and performance of cathode active materials (CAMs) for solid-state batteries (SSBs) is crucial to help better understand these systems and enable the synthesis of well-performing CAMs. However, there is a lack of well-thought-out procedures to reliably evaluate CAMs in SSBs. Current approaches often rely on X-ray photoelectron spectroscopy (XPS) for the evaluation of degradation. Unfortunately, XPS sensitivity is not very high, and minor but relevant degradation products may not be detected and distinguished. Furthermore, degradation caused by the current collector (CC) itself is usually not distinguished from CAM-induced degradation. This study uses a modified CC, which allows us to separate electrochemical degradation caused by the CC from degradation at the CAM itself. Using this CC, we present an approach using time-of-flight secondary ions mass spectrometry (ToF-SIMS) that offers high sensitivity and reliability. Principal component analysis (PCA) is applied to differentiate secondary ions as well as identify those mass fragments that correlate with degradation products. This approach also enables distinguishing between different pathways of degradation. To evaluate the kinetic performance of the samples, three-electrode rate tests are performed. Electrochemical characterization evaluates the kinetic performance of the samples under investigation. The samples are finally rated with a score that allows a reliable comparison between the different materials and offers a complete picture of the materials' characteristics in terms of electrochemical performance and degradation.

Mechanistic interpretation of the sorption of terbuthylazine pesticide onto aged microplastics.

Microplastics (MPs) pose a global concern due to their ubiquitous distribution. Once in the environment, they are subject to aging, which changes their chemical-physical properties and ability to interact with organic pollutants, such as pesticides. Therefore, this study investigated the interaction of the hydrophobic herbicide terbuthylazine (TBA), which is widely used in agriculture, with artificially aged polyethylene (PE) MP (PE-MP) to understand how aging affects its sorption. PE was aged by an accelerated weathering process including UV irradiation, hydrogen peroxide, and ultrasonic treatment, and aged particles were characterized in comparison to pristine particles. Sorption kinetics were performed for aged and pristine materials, while further sorption studies with aged PE-MP included determining environmental factors such as pH, temperature, and TBA concentration. Sorption of TBA was found to be significantly lower on aged PE-MP compared to pristine particles because aging led to the formation of oxygen-containing functional groups, resulting in a reduction in hydrophobicity and the formation of negatively charged sites on oxidized surfaces. For pristine PE-MP, sorption kinetics were best described by the pseudo-second-order model, while it was intra-particle diffusion for aged PE-MP as a result of crack and pore formation. Sorption followed a decreasing trend with increasing pH, while it became less favorable at higher temperatures. The isotherm data revealed a complex sorption process on altered, heterogeneous surfaces involving hydrophobic interactions, hydrogen bonding, and π-π interactions, and the process was best described by the Sips adsorption isotherm model. Desorption was found to be low, confirming a strong interaction. However, thermodynamic results imply that increased temperatures, such as those resulting from climate change, could promote the re-release of TBA from aged PE-MP into the environment. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed TBA sorption onto PE.

Low-Fouling and Antibacterial Polymer Brushes via Surface-Initiated Polymerization of a Mixed Zwitterionic and Cationic Monomer.

The use of surface-grafted polymer brushes with combined low-fouling and antibacterial functionality is an attractive strategy to fight biofilm formation. This report describes a new styrene derivative combining a quaternary ammonium group with a sulfobetaine group in one monomer. Surface-initiated polymerization of this monomer on titanium and a polyethylene (PE) base material gave bifunctional polymer brush layers. Grafting was achieved via surface-initiated atom transfer radical polymerization from titanium or heat-induced free-radical polymerization from plasma-activated PE. Both techniques gave charged polymer layers with a thickness of over 750 nm, as confirmed by ToF-SIMS-SPM measurements. The chemical composition of the brush polymers was confirmed by XPS and FT-IR analysis. The surface charge, characterized by the ζ potential, was positive at different pH values, and the number of solvent-accessible excess ammonium groups was found to be ∼1016 N+/cm2. This led to strong antibacterial activity against Gram-positive and Gram-negative bacteria that was superior to a structurally related contact-active polymeric quaternary ammonium brush. In addition to this antibacterial activity, good low-fouling properties of the dual-function polymer brushes against Gram-positive and Gram-negative bacteria were found. This dual functionality is most likely due to the combination of antibacterial quaternary ammonium groups with antifouling sulfobetaines. The combination of both groups in one monomer allows the preparation of bifunctional brush polymers with operationally simple polymerization techniques.

Mesoporous Bioactive Glass-Incorporated Injectable Strontium-Containing Calcium Phosphate Cement Enhanced Osteoconductivity in a Critical-Sized Metaphyseal Defect in Osteoporotic Rats.

In this study, the in vitro and in vivo bone formation behavior of mesoporous bioactive glass (MBG) particles incorporated in a pasty strontium-containing calcium phosphate bone cement (pS100G10) was studied in a metaphyseal fracture-defect model in ovariectomized rats and compared to a plain pasty strontium-containing calcium phosphate bone cement (pS100) and control (empty defect) group, respectively. In vitro testing showed good cytocompatibility on human preosteoblasts and ongoing dissolution of the MBG component. Neither the released strontium nor the BMG particles from the pS100G10 had a negative influence on cell viability. Forty-five female Sprague-Dawley rats were randomly assigned to three different treatment groups: (1) pS100 (n = 15), (2) pS100G10 (n = 15), and (3) empty defect (n = 15). Twelve weeks after bilateral ovariectomy and multi-deficient diet, a 4 mm wedge-shaped fracture-defect was created at the metaphyseal area of the left femur in all animals. The originated fracture-defect was substituted with pS100 or pS100G10 or left empty. After six weeks, histomorphometrical analysis revealed a statistically significant higher bone volume/tissue volume ratio in the pS100G10 group compared to the pS100 (p = 0.03) and empty defect groups (p = 0.0001), indicating enhanced osteoconductivity with the incorporation of MBG. Immunohistochemistry revealed a significant decrease in the RANKL/OPG ratio for pS100 (p = 0.004) and pS100G10 (p = 0.003) compared to the empty defect group. pS100G10 showed a statistically higher expression of BMP-2. In addition, a statistically significant higher gene expression of alkaline phosphatase, osteoprotegerin, collagen1a1, collagen10a1 with a simultaneous decrease in RANKL, and carbonic anhydrase was seen in the pS100 and pS100G10 groups compared to the empty defect group. Mass spectrometric imaging by time-of-flight secondary ion mass spectrometry (ToF-SIMS) showed the release of Sr2+ ions from both pS100 and pS100G10, with a gradient into the interface region. ToF-SIMS imaging also revealed that resorption of the MBG particles allowed for new bone formation in cement pores. In summary, the current work shows better bone formation of the injectable pasty strontium-containing calcium phosphate bone cement with incorporated mesoporous bioactive glass compared to the bioactive-free bone cement and empty defects and can be considered for clinical application for osteopenic fracture defects in the future.

Contact-Biocide TiO2 Surfaces by Surface-Initiated Atom Transfer Radical Polymerization with Chemically Stable Phosphonate Initiators.

Surface-initiated atom transfer radical polymerization (SI-ATRP) is a powerful tool for grafting functional polymers from metal surfaces. It depends on the immobilization of suitable initiators on the surface before radical polymerization. Herein, we report a set of bifunctional initiators bearing a phosphonic acid group for surface binding and a bromoisobutyramide moiety for SI-ATRP. We have analyzed the impact of the connecting alkyl spacers on the grafting process of (vinylbenzyl)trimethylammonium chloride (VBTAC) from titanium as a base material. The thickness of the grafted polymer increased with the spacer length of the initiator. We obtained chemically stable polycationic surfaces with high charge densities of ∼1016 N+/cm2 leading to efficient contact activity of modified titanium coupons against S. aureus. Notably, SI-ATRP grafting was efficient with VBTAC as a styrene-derived ammonium compound. Thus, the reported protocol avoids post-grafting quaternization with toxic alkylating reagents.

Secondary ion mass spectrometry for bone research.

The purpose of this Tutorial is to highlight the suitability of time-of-flight secondary ion mass spectrometry (ToF-SIMS) and OrbiTrap™ SIMS (Orbi-SIMS) in bone research by introducing fundamentals and best practices of bone analysis with these mass spectrometric imaging (MSI) techniques. The Tutorial includes sample preparation, determination of best-suited measurement settings, data acquisition, and data evaluation, as well as a brief overview of SIMS applications in bone research in the current literature. SIMS is a powerful analytical technique that allows simultaneous analysis and visualization of mineralized and nonmineralized bone tissue, bone marrow as well as implanted biomaterials, and interfaces between bone and implants. Compared to histological staining, which is the standard analytical procedure in bone research, SIMS provides chemical imaging of nonstained bone sections that offers insights beyond what is conventionally obtained. The Tutorial highlights the versatility of ToF- and Orbi-SIMS in addressing important questions in bone research. By illustrating the value of these MSI techniques, it demonstrates how they can contribute to advance progress in bone research.

Zwitterionic surface modification of polyethylene via atmospheric plasma-induced polymerization of (vinylbenzyl-)sulfobetaine and evaluation of antifouling properties.

Zwitterionic polymer brushes were grafted from bulk polyethylene (PE) by air plasma activation of the PE surface followed by radical polymerization of the zwitterionic styrene derivative (vinylbenzyl)sulfobetaine (VBSB). Successful formation of dense poly-(VBSB)-brush layers was confirmed by goniometry, IR spectroscopy, XPS and ToF-SIMS analysis. The resulting zwitterionic layers are about 50-100 nm thick and cause extremely low contact angles of 10° (water) on the material. Correspondingly we determined a high density of > 1.0 × 1016 solvent accessible zwitterions/cm2 (corresponding to 2,0 *10-8 mol/cm2) by a UV-based ion-exchange assay with crystal violet. The elemental composition as determined by XPS and characteristic absorption bands in the IR spectra confirmed the presence of zwitterionic sulfobetaine polymer brushes. The antifouling properties of the resulting materials were evaluated in a bacterial adhesion test against gram-positive bacteria (S. aureus). We observed significantly reduced cellular adhesion of the zwitterionic material compared to pristine PE. These microbiological tests were complemented by tests in natural seawater. During a test period of 21 days, confocal microscopy revealed excellent antifouling properties and confirmed the operating antifouling mechanism. The procedure reported herein allows the efficient surface modification of bulk PE with zwitterionic sulfobetaine polymer brushes via a scalable approach. The resulting modified PE retains important properties of the bulk material and has excellent and durable antifouling properties.

Sol-Gel-Derived Ordered Mesoporous High Entropy Spinel Ferrites and Assessment of Their Photoelectrochemical and Electrocatalytic Water Splitting Performance.

The novel material class of high entropy oxides with their unique and unexpected physicochemical properties is a candidate for energy applications. Herein, it is reported for the first time about the physico- and (photo-) electrochemical properties of ordered mesoporous (CoNiCuZnMg)Fe2 O4 thin films synthesized by a soft-templating and dip-coating approach. The A-site high entropy ferrites (HEF) are composed of periodically ordered mesopores building a highly accessible inorganic nanoarchitecture with large specific surface areas. The mesoporous spinel HEF thin films are found to be phase-pure and crack-free on the meso- and macroscale. The formation of the spinel structure hosting six distinct cations is verified by X-ray-based characterization techniques. Photoelectron spectroscopy gives insight into the chemical state of the implemented transition metals supporting the structural characterization data. Applied as photoanode for photoelectrochemical water splitting, the HEFs are photostable over several hours but show only low photoconductivity owing to fast surface recombination, as evidenced by intensity-modulated photocurrent spectroscopy. When applied as oxygen evolution reaction electrocatalyst, the HEF thin films possess overpotentials of 420 mV at 10 mA cm-2 in 1 m KOH. The results imply that the increase of the compositional disorder enhances the electronic transport properties, which are beneficial for both energy applications.

Impact of the Chlorination of Lithium Argyrodites on the Electrolyte/Cathode Interface in Solid-State Batteries.

Lithium argyrodite-type electrolytes are regarded as promising electrolytes due to their high ionic conductivity and good processability. Chemical modifications to increase ionic conductivity have already been demonstrated, but the influence of these modifications on interfacial stability remains so far unknown. In this work, we study Li6 PS5 Cl and Li5.5 PS4.5 Cl1.5 to investigate the influence of halogenation on the electrochemical decomposition of the solid electrolyte and the chemical degradation mechanism at the cathode interface in depth. Electrochemical measurements, gas analysis and time-of-flight secondary ion mass spectrometry indicate that the Li5.5 PS4.5 Cl1.5 shows pronounced electrochemical decomposition at lower potentials. The chemical reaction at higher voltages leads to more gaseous degradation products, but a lower fraction of solid oxygenated phosphorous and sulfur species. This in turn leads to a decreased interfacial resistance and thus a higher cell performance.

Characterisation of Sr2+ mobility in osteoporotic rat bone marrow by cryo-ToF-SIMS and cryo-OrbiSIMS.

Strontium (Sr2+) ions are an effective therapeutic agent for the healing of osteoporotic bone fractures and are therefore used, for example, in form of strontium-modified bone cements. In order to reduce animal testing in further implant materials development in the future, a simulation of the Sr2+ release and transport in bone would be helpful. For such a simulation, knowledge of the experimental parameters for Sr2+ mobility in different compartments of bone (mineralised bone, bone marrow) is essential. In a previous study, we developed an experimental protocol for transport studies in bovine bone marrow by time-of-flight secondary ion mass spectrometry (ToF-SIMS). In the current proof-of-concept study, we investigated Sr2+ diffusion for the first time in bone marrow of rat bone sections. Additionally, orbitrap secondary ion mass spectrometry (OrbiSIMS) was applied for unambiguous signal identification of lipids and fatty acid species in rat bone marrow. Detailed 2D and 3D mass spectrometric imaging analyses, depth profiling as well as OrbiSIMS spectrometric analysis revealed faster Sr2+ diffusion in rat bone marrow areas with low intensity of lipid and fatty acid signals than in areas with higher lipid/fatty acid content. These results could be confirmed by histological staining and additional analysis of Sr2+ diffusion into pure fat sections.

A Ziegler-type spherical cap model reveals early stage ethylene polymerization growth versus catalyst fragmentation relationships.

Polyolefin catalysts are characterized by their hierarchically complex nature, which complicates studies on the interplay between the catalyst and formed polymer phases. Here, the missing link in the morphology gap between planar model systems and industrially relevant spherical catalyst particles is introduced through the use of a spherical cap Ziegler-type catalyst model system for the polymerization of ethylene. More specifically, a moisture-stable LaOCl framework with enhanced imaging contrast has been designed to support the TiCl4 pre-active site, which could mimic the behaviour of the highly hygroscopic and industrially used MgCl2 framework. As a function of polymerization time, the fragmentation behaviour of the LaOCl framework changed from a mixture of the shrinking core (i.e., peeling off small polyethylene fragments at the surface) and continuous bisection (i.e., internal cleavage of the framework) into dominantly a continuous bisection model, which is linked to the evolution of the estimated polyethylene volume and the fraction of crystalline polyethylene formed. The combination of the spherical cap model system and the used advanced micro-spectroscopy toolbox, opens the route for high-throughput screening of catalyst functions with industrially relevant morphologies on the nano-scale.

Determination of Sr2+ mobility in viscous bovine bone marrow by cryo-time-of-flight secondary ion mass spectrometry.

RATIONALE: In osteoporosis research, strontium ions (Sr2+ ) have emerged as promising therapeutic agent in modified bone cements for better fracture healing. Modeling of Sr2+ dispersion in bone could be used as a predictive tool for the evaluation of functionalized biomaterials in future. Therefore, determination of experimental parameters for Sr2+ transport in bone is essential. In this study, we focus on the determination of Sr2+ diffusion in viscous bovine bone marrow by time-of-flight secondary ion mass spectrometry (ToF-SIMS). METHODS: For this comparatively fast diffusion (FD) experiment, a specific experimental protocol of ToF-SIMS depth profiling under cryogenic conditions was developed. The validity of our experimental approach is proven by a time-dependent experimental series. Furthermore, 2D and 3D mass spectrometric imaging analysis was used to study Sr2+ surface and bulk distribution within bovine bone marrow. RESULTS: Detailed 2D and 3D mass spectrometric imaging analysis revealed that Sr2+ diffusion is slower in bone marrow areas with high intensity of lipid and fatty acid signals than in areas with less lipid content. The Sr2+ transport within this passive model can be described by Fickian diffusion. Average diffusion coefficients of Sr2+ in bovine bone marrow were obtained from diffusion profiles in FD areas (Dbovine,FD = [2.09 ± 2.39]·10-9 cm2 s-1 ), slow diffusion areas (Dbovine,SD = [1.52 ± 1.80]·10-10 cm2 s-1 ), and total area diffusion (Dbovine,TA = [1.94 ± 2.40]·10-9 cm2 s-1 ). CONCLUSIONS: We were able to show that cryo-ToF-SIMS is a useful tool for the characterization of rapid diffusion in water-containing highly viscous media. To the best of our knowledge, this is the first reported experimental approach for the investigation of the distribution of low concentrated therapeutic agents in bone marrow. Overall, our results provide important insights about Sr2+ diffusion in bovine bone marrow.

Cluster-induced desorption/ionization mass spectrometry of highlighter ink: unambiguous identification of dyes and degradation processes based on fragmentation-free desorption.

Highlighter inks were analyzed by means of soft Desorption/Ionization induced by Neutral SO2 clusters (DINeC) in combination with mass spectrometry (MS). The dye molecules of the different inks were directly desorbed from dots of ink drawn on arbitrary substrates. Fragmentation free spectra were observed and the dyes used in the dye mixtures of the different highlighter inks were unambiguously identified. The soft nature of cluster-induced desorption was used to investigate the decomposition of the dye molecules induced by either heat or UV-light. The two processes lead to different decomposition products which are clearly distinguished in the DINeC spectra. The two different degradation processes can thus be discriminated using DINeC-MS.

A mechanistic investigation of the Li10GeP2S12|LiNi1-x-yCoxMnyO2 interface stability in all-solid-state lithium batteries.

All-solid-state batteries are intensively investigated, although their performance is not yet satisfactory for large-scale applications. In this context, the combination of Li10GeP2S12 solid electrolyte and LiNi1-x-yCoxMnyO2 positive electrode active materials is considered promising despite the yet unsatisfactory battery performance induced by the thermodynamically unstable electrode|electrolyte interface. Here, we report electrochemical and spectrometric studies to monitor the interface evolution during cycling and understand the reactivity and degradation kinetics. We found that the Wagner-type model for diffusion-controlled reactions describes the degradation kinetics very well, suggesting that electronic transport limits the growth of the degradation layer formed at the electrode|electrolyte interface. Furthermore, we demonstrate that the rate of interfacial degradation increases with the state of charge and the presence of two oxidation mechanisms at medium (3.7 V vs. Li+/Li < E < 4.2 V vs. Li+/Li) and high (E ≥ 4.2 V vs. Li+/Li) potentials. A high state of charge (>80%) triggers the structural instability and oxygen release at the positive electrode and leads to more severe degradation.

Strontium substitution of gelatin modified calcium hydrogen phosphates as porous hard tissue substitutes.

Aiming at the generation of a high strontium-containing degradable bone substitute, the exchange of calcium with strontium in gelatin-modified brushite was investigated. The ion substitution showed two mineral groups, the high-calcium containing minerals with a maximum measured molar Ca/Sr ratio of 80%/20% (mass ratio 63%/37%) and the high-strontium containing ones with a maximum measured molar Ca/Sr ratio of 21%/79% (mass ratio 10%/90%). In contrast to the high-strontium mineral phases, a high mass loss was observed for the calcium-based minerals during incubation in cell culture medium (alpha-MEM), but also an increase in strength owing to dissolution and re-precipitation. This resulted for the former in a decrease of cation concentration (Ca + Sr) in the medium, while the pH value decreased and the phosphate ion concentration rose significantly. The latter group of materials, the high-strontium containing ones, showed only a moderate change in mass and a decrease in strength, but the Ca + Sr concentration remained permanently above the initial calcium concentration in the medium. This might be advantageous for a future planned application by supporting bone regeneration on the cellular level.

Conceptual Framework for Dislocation-Modified Conductivity in Oxide Ceramics Deconvoluting Mesoscopic Structure, Core, and Space Charge Exemplified for SrTiO3.

The introduction of dislocations is a recently proposed strategy to tailor the functional and especially the electrical properties of ceramics. While several works confirm a clear impact of dislocations on electrical conductivity, some studies raise concern in particular when expanding to dislocation arrangements beyond a geometrically tractable bicrystal interface. Moreover, the lack of a complete classification on pertinent dislocation characteristics complicates a systematic discussion and hampers the design of dislocation-modified electrical conductivity. We proceed by mechanically introducing dislocations with three different mesoscopic structures into the model material single-crystal SrTiO3 and extensively characterizing them from both a mechanical as well as an electrical perspective. As a final result, a deconvolution of mesoscopic structure, core structure, and space charge enables us to obtain the complete picture of the effect of dislocations on functional properties, focusing here on electric properties.

Gelatin-Modified Calcium/Strontium Hydrogen Phosphates Stimulate Bone Regeneration in Osteoblast/Osteoclast Co-Culture and in Osteoporotic Rat Femur Defects-In Vitro to In Vivo Translation.

The development and characterization of biomaterials for bone replacement in case of large defects in preconditioned bone (e.g., osteoporosis) require close cooperation of various disciplines. Of particular interest are effects observed in vitro at the cellular level and their in vivo representation in animal experiments. In the present case, the material-based alteration of the ratio of osteoblasts to osteoclasts in vitro in the context of their co-cultivation was examined and showed equivalence to the material-based stimulation of bone regeneration in a bone defect of osteoporotic rats. Gelatin-modified calcium/strontium phosphates with a Ca:Sr ratio in their precipitation solutions of 5:5 and 3:7 caused a pro-osteogenic reaction on both levels in vitro and in vivo. Stimulation of osteoblasts and inhibition of osteoclast activity were proven during culture on materials with higher strontium content. The same material caused a decrease in osteoclast activity in vitro. In vivo, a positive effect of the material with increased strontium content was observed by immunohistochemistry, e.g., by significantly increased bone volume to tissue volume ratio, increased bone morphogenetic protein-2 (BMP2) expression, and significantly reduced receptor activator of nuclear factor kappa-B ligand (RANKL)/osteoprotegerin (OPG) ratio. In addition, material degradation and bone regeneration were examined after 6 weeks using stage scans with ToF-SIMS and µ-CT imaging. The remaining material in the defects and strontium signals, which originate from areas exceeding the defect area, indicate the incorporation of strontium ions into the surrounding mineralized tissue. Thus, the material inherent properties (release of biologically active ions, solubility and degradability, mechanical strength) directly influenced the cellular reaction in vitro and also bone regeneration in vivo. Based on this, in the future, materials might be synthesized and specifically adapted to patient-specific needs and their bone status.

Effect of long term palmitate treatment on osteogenic differentiation of human mesenchymal stromal cells - Impact of albumin.

The long-term effects of palmitate (PA) on osteogenic differentiation capacity of human mesenchymal stromal cells (hMSCs) were investigated by cultivating the cells in osteogenic differentiation medium (O-w/o) and osteogenic medium containing PA (O-BSA-PA) for 21 days. Osteogenic medium containing BSA (O-BSA) was used as a control. By means of rt-qPCR, successful osteogenic differentiation was observed in the O-w/o regarding the levels of osteogenic and cell-communication related genes (OCN, Col1, BMP2, ITGA1, ITGB1, Cx43, sp1) in contrast to expression levels observed in cells incubated within basal medium. However, in the O-BSA, these genes were found to have decreased significantly. In cases of Cx43 and sp1, PA significantly reinforced the reductive effect of BSA alone. O-BSA notably decreased glucose and pyruvate consumption, whereas glutamine consumption significantly increased. In comparison to O-BSA addition of PA significantly reduced glycolysis and glutaminolysis. ToF-SIMS analysis confirmed increased incorporation of supplemented deuterated PA into the cell membranes, while the overall PA-concentration remained unchanged compared to cells incubated in the O-BSA and O-w/o. Therefore, the effects on gene expression and the metabolism did not result from the membrane alterations, but may have risen from inter- and intracellular effects brought on by BSA and PA.