SiOC Screens with Aligned and Adjustable Pore Structure for Screen Channel Liquid Acquisition Device.

The development of porous ceramic screens with high chemical stability, low density, and thermal conductivity can lead to promising screen channel liquid acquisition devices (SC-LADs) for propellant management under microgravity conditions in the future. Therefore, SiOC screens with aligned pores were fabricated via freeze-casting and applied as a SC-LAD. The pore window sizes and open porosity varied from 6 µm to 43 µm and 65% or 79%, depending on the freezing temperature or the solid loading, respectively. The pore window size distributions and bubble point tests indicate crack-free screens. On the one hand, SC-LADs with an open porosity of 79% removed gas-free liquid up to a volumetric flow rate of 4 mL s-1. On the other hand, SC-LADs with an open porosity of 65% were limited to 2 mL s-1 as the pressure drop across these screens was relatively higher. SC-LADs with the same open porosity but smaller pore window sizes showed a higher pressure drop across the screen and bubble ingestion at higher values of effective screen area when increasing the applied removal volumetric flow rate. The removed liquid from the SC-LADs was particle-free, thus representing a potential for applications in a harsh chemical environment or broad-range temperatures.

Influence of the Pyrolysis Temperature and TiO2-Incorporation on the Properties of SiOC/SiC Composites for Efficient Wastewater Treatment Applications.

This study focuses on the development of porous ceramer and SiOC composites which are suitable for microfiltration applications, using a mixture of polysiloxanes as the preceramic precursor. The properties of the membranes-such as their pore size, hydrophilicity, specific surface area, and mechanical resistance-were tailored in a one-step process, according to the choice of pyrolysis temperatures (600-1000 °C) and the incorporation of micro- (SiC) and nanofillers (TiO2). Lower pyrolysis temperatures (<700 °C) allowed the incorporation of TiO2 in its photocatalytically active anatase phase, enabling the study of its photocatalytic decomposition. The produced materials showed low photocatalytic activity; however, a high adsorption capacity for methylene blue was observed, which could be suitable for dye-removal applications. The membrane performance was evaluated in terms of its maximum flexural strength, water permeation, and separation of an oil-in-water emulsion. The mechanical resistance increased with an increase of the pyrolysis temperature, as the preceramic precursor underwent the ceramization process. Water fluxes varying from 2.5 to 370 L/m2·h (2 bar) were obtained according to the membrane pore sizes and surface characteristics. Oil-rejection ratios of 81-98% were obtained at an initial oil concentration of 1000 mg/L, indicating a potential application of the produced PDC membranes in the treatment of oily wastewater.

Assessment of nanoparticle immersion depth at liquid interfaces from chemically equivalent macroscopic surfaces.

HYPOTHESIS: We test whether the wettability of nanoparticles (NPs) straddling at an air/water surface or oil/water interface can be extrapolated from sessile drop-derived macroscopic contact angles (mCAs) on planar substrates, assuming that both the nanoparticles and the macroscopic substrates are chemically equivalent and feature the same electrokinetic potential. EXPERIMENTS: Pure silica (SiO2) and amino-terminated silica (APTES-SiO2) NPs are compared to macroscopic surfaces with extremely low roughness (root mean square [RMS] roughness ≤ 2 nm) or a roughness determined by a close-packed layer of NPs (RMS roughness âˆ¼ 35 nm). Equivalence of the surface chemistry is assessed by comparing the electrokinetic potentials of the NPs via electrophoretic light scattering and of the macroscopic substrates via streaming current analysis. The wettability of the macroscopic substrates is obtained from advancing (ACAs) and receding contact angles (RCAs) and in situ synchrotron X-ray reflectivity (XRR) provided by the NP wettability at the liquid interfaces. FINDINGS: Generally, the RCA on smooth surfaces provides a good estimate of NP wetting properties. However, mCAs alone cannot predict adsorption barriers that prevent NP segregation to the interface, as is the case with the pure SiO2 nanoparticles. This strategy greatly facilitates assessing the wetting properties of NPs for applications such as emulsion formulation, flotation, or water remediation.

Genipin-crosslinked chitosan/alginate/alumina nanocomposite gels for 3D bioprinting.

Immobilizing microorganisms inside 3D printed semi-permeable substrates can be desirable for biotechnological processes since it simplifies product separation and purification, reducing costs, and processing time. To this end, we developed a strategy for synthesizing a feedstock suitable for 3D bioprinting of mechanically rigid and insoluble materials with embedded living bacteria. The processing route is based on a highly particle-filled alumina/chitosan nanocomposite gel which is reinforced by (a) electrostatic interactions with alginate and (b) covalent binding between the chitosan molecules with the mild gelation agent genipin. To analyze network formation and material properties, we characterized the rheological properties and printability of the feedstock gel. Stability measurements showed that the genipin-crosslinked chitosan/alginate/alumina gels did not dissolve in PBS, NaOH, or HCl after 60 days of incubation. Alginate-containing gels also showed less swelling in water than gels without alginate. Furthermore, E. coli bacteria were embedded in the nanocomposites and we analyzed the influence of the individual bioink components as well as of the printing process on bacterial viability. Here, the addition of alginate was necessary to maintain the effective viability of the embedded bacteria, while samples without alginate showed no bacterial viability. The experimental results demonstrate the potential of this approach for producing macroscopic bioactive materials with complex 3D geometries as a platform for novel applications in bioprocessing.

Arsenic and sulfur nanoparticle synthesis mimicking environmental conditions of submarine shallow-water hydrothermal vents.

Arsenic and sulfur mineralization is a natural phenomenon occurring in hydrothermal systems where parameters like temperature and organic matter (OM) can influence the mobilization of the toxic metalloid in marine environments. In the present study we analyze the influence of temperature and OM (particularly sulfur-containing additives) on As and S precipitation based on the recent discovery of As-rich nanoparticles in the hydrothermal system near the coast of the Greek island Milos. To this end, we experimentally recreate the formation of amorphous colloidal particles rich in As and S via acidification (pH 3-4) of aqueous precursors at various temperatures. At higher temperatures, we observe the formation of monodisperse particles within the first 24 h of the experiment, generating colloidal particles with diameters close to 160 nm. The S:As ratio and particle size of the synthetized particles closely correlates with values for AsxSy particles detected in the hydrothermal system off Milos. Furthermore, organic sulfur containing additives (cysteine and glutathione, GSH) are a key factor in the process of nucleation and growth of amorphous colloidal AsxSy particles and, together with the temperature gradient present in shallow hydrothermal vents, dictate the stabilization of As-bearing nanomaterials in the environment. Based on these findings, we present a simple model that summarizes our new insights into the formation and mobility of colloidal As in aquatic ecosystems. In this context, amorphous AsxSy particles can present harmful effects to micro- and macro-biota not foreseen in bulk As material.

Synergistic and Competitive Adsorption of Hydrophilic Nanoparticles and Oil-Soluble Surfactants at the Oil-Water Interface.

Fundamental insights into the interplay and self-assembly of nanoparticles and surface-active agents at the liquid-liquid interface play a pivotal role in understanding the ubiquitous colloidal systems present in our natural surroundings, including foods and aquatic life, and in the industry for emulsion stabilization, drug delivery, or enhanced oil recovery. Moreover, well-controlled model systems for mixed interfacial adsorption of nanoparticles and surfactants allow unprecedented insights into nonideal or contaminated particle-stabilized emulsions. Here, we investigate such a model system composed of hydrophilic, negatively, and positively charged silica nanoparticles and the oil-soluble cationic lipid octadecyl amine with in situ synchrotron-based X-ray reflectometry, which is analyzed and discussed jointly with dynamic interfacial tensiometry. Our results indicate that negatively charged silica nanoparticles only adsorb if the oil-water interface is covered with the positively charged lipid, indicating synergistic adsorption. Conversely, the positively charged nanoparticles readily adsorb on their own, but compete with octadecyl amine and reversibly desorb with increasing concentrations of the lipid. These results further indicate that with competitive adsorption, an electrostatic exclusion zone exists around the adsorbed particles. This prevents the adsorption of lipid molecules in this area, leading to a decreased surface excess concentration of surfactants and unexpectedly high interfacial tension.

Effect of Collagen Nanofibers and Silanization on the Interaction of HaCaT Keratinocytes and 3T3 Fibroblasts with Alumina Nanopores.

During wound healing, a complex cascade of cellular and molecular events occurs, which is governed by topographical and biochemical cues. Therefore, optimal tissue repair requires scaffold materials with versatile structural and biochemical features. Nanoporous anodic aluminum oxide (AAO) membranes exhibit good biocompatibility along with customizable nanotopography and antimicrobial properties, which has brought them into the focus of wound treatment. However, despite their good permeability, such bioinert ceramic nanopores cannot actively promote cell growth as they lack biochemical cues to support specific ligand-receptor interactions. Therefore, we modified AAO nanopores with the biochemical features of collagen nanofibers or amino groups provided by silanization with (3-aminopropyl)triethoxysilane (APTES) to design a permeable scaffold material that can additionally promote cell adhesion. Viability assays revealed that the metabolic activity of both 3T3 fibroblasts and HaCaT keratinocytes on bare and silanized AAO pores was comparable to glass controls until 72 h. Interestingly, both cell types showed a reduced proliferation on AAO with collagen nanofibers. Nevertheless, scanning electron and fluorescence microscopy revealed that 3T3 fibroblasts exhibited a well-spread morphology with filopodia attached to the nanoporous surface of the underlying AAO membranes or nanofibrous collagen networks, thus indicating a close interaction with the composites. Keratinocytes, although growing in clusters on bare and APTES-modified AAO, also adhered well on collagen-modified AAO membranes. When in contact with Escherichia coli suspensions for 20 h, the AAO membranes successfully prevented bacteria penetration irrespective of the biochemical functionalization. In summary, both functionalization strategies have high potential to specifically control molecular signaling and cell migration to further develop alumina nanopores for wound healing.

One-dimensional polymer-derived ceramic nanowires with electrocatalytically active metallic silicide tips as cathode catalysts for Zn-air batteries.

New metallic nickel/cobalt/iron silicide droplets at the tips of polymer-derived ceramic (PDC) nanowires have been identified as stable and efficient cathode catalysts for Zn-air batteries. The as-prepared catalyst having a unique one-dimensional (1D) PDC nanowire structure with the presence of metallic silicide tips of 1D-PDC plays a crucial role in facilitating oxygen reduction/evolution reaction kinetics. The Zn-air battery was designed using Ni/PDC, Co/PDC and Fe/PDC as air electrode catalysts. In electrochemical half-cell tests, it was observed that the catalysts have a good bifunctional electrocatalytic activity. The efficiency of the catalysts to function as a cathode catalyst in real-time primary and mechanically rechargeable Zn-air battery configurations was determined. The primary battery testing results revealed that Ni/PDC and Co/PDC exhibited a stable discharge voltage plateau up to 29 h. The Fe/PDC sample, on the other hand, performed up to 23 h with an operating potential of 1.20 V at the discharge current density of 5 mA cm-2 after which the battery ceased to perform. The Ni/PDC, Co/PDC, and Fe/PDC cathode catalysts performed galvanostatic 1200 charge-discharge cycles in a mechanically rechargeable secondary Zn-air battery configuration. The results demonstrate that the Ni/PDC, Co/PDC, and Fe/PDC materials serve as excellent and durable bifunctional cathode electrocatalysts for Zn-air batteries.

Janus nanoparticles designed for extended cell surface attachment.

In this study, we present Janus nanoparticles that are designed for attaching to a eukaryotic cell surface with minimal cell uptake. This contrasts the rapid uptake via various endocytosis pathways that non-passivated isotropic particles usually encounter. Firmly attaching nanoparticles onto cell surfaces for extended periods of time can be a powerful new strategy to employ functional properties of nanoparticles for non-invasive interrogation and manipulation of biological systems. To this end, we synthesized rhodamine-doped silica (SiO2) nanoparticles functionalized with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE) on one hemisphere of the nanoparticle surface and high-molecular-weight long-chain poly(ethylene glycol) on the other one using the wax-Pickering emulsion technique. Nanoparticle localization was studied with NIH 3T3 rat fibroblasts in vitro. In these studies, the Janus nanoparticles adhered to the cell surface and, in contrast to isotropic control particles, only negligible uptake into the cells was observed, even after 24 h of incubation. In order to characterize the potential endocytosis pathway involved in the uptake of the Janus nanoparticles in more detail, fibroblasts and nanoparticles were incubated in the presence or absence of different endocytosis inhibitors. Our findings indicate that the Janus particles are not affected by caveolae- and receptor-mediated endocytosis and the prolonged attachment of the Janus nanoparticles is most likely the result of an incomplete macropinocytosis process. Consequently, by design, these Janus nanoparticles have the potential to firmly anchor onto cell surfaces for extended periods of time and might be utilized in various biotechnological and biomedical applications like cell surface tagging, magnetic manipulation of the cell membrane or non-invasive drug and gene delivery.

Surface Functionalization of Mesoporous Membranes: Impact on Pore Structure and Gas Flow Mechanisms.

Membranes showing monomodal pore size distributions with mean pore diameters of 23, 33, and 60 nm are chemically functionalized using silanes with varying chain length and functional groups like amino, alkyl, phenyl, sulfonate, and succinic anhydrides. Their influence on the morphology, pore structure, and gas flow is investigated. For this, single-gas permeation measurements at pressures around 0.1 MPa are performed at temperatures ranging from 273 to 353 K using He, Ne, Ar, N2, CO, CO2, CH4, C2H4, C2H6, and C3H8. Results show pore size and pore volume linearly depending on the length of functional molecules, as expected for monolayer deposition. However, the gas flow through functionalized membranes is disproportionally decreased up to a factor of around 10. Hence, the decreased pore size and pore volume cannot explain the large decrease in flow. Furthermore, there is no specific dependency between the decrease in flow and temperature or gas type other than the relation proposed by Knudsen (√RTM)-1. Considering the large variety of functional molecules used, it is very surprising that no correlations between the type of functional group and the flow have been found. The decrease in flow, however, is strongly dependent on the chain length of the silanes (factor of 10 at ∼2 nm length). This leads to the conclusion that the observed effect is not caused by sorption driven processes. It is proposed that steric interactions between functional groups and gas molecules lead to increased residence times on the surface and longer molecular trajectories, which, in turn, lead to a decrease in flow. In membrane design, any surface modification should, therefore, make use of functionalizing agents with chain length as short as possible.

A new silicon oxycarbide based gas diffusion layer for zinc-air batteries.

Rational material designs play a vital role in the gas diffusion layer (GDL) by increasing the oxygen diffusion rate and, consequently, facilitating a longer cycle life for metal-air batteries. In this work, a new porous conductive ceramic membrane has been developed as a cathodic GDL for zinc-air battery (ZAB). The bilayered structure with a thickness of 390 µm and an open porosity of 55% is derived from a preceramic precursor with the help of the freeze tape casting technique. The hydrophobic behaviour of the GDL is proved by the water contact angle of 137.5° after the coating of polytetrafluoroethylene (PTFE). The electrical conductivity of 5.59 * 10-3 S/cm is reached using graphite and MWCNT as filler materials. Tested in a ZAB system, the as-prepared GDL coated with commercial Pt-Ru/C catalyst shows an excellent cycle life over 200 cycles and complete discharge over 48 h by consuming oxygen from the atmosphere, which is comparable to commercial electrodes. The as-prepared electrode exhibits excellent ZAB performance due to the symmetric sponge-like structure, which facilitates the oxygen exchange rate and offers a short path for the oxygen ion/-electron kinetics. Thus, this work highlights the importance of a simple manufacturing process that significantly influences advanced ZAB enhancement.

Reversible Adsorption of Nanoparticles at Surfactant-Laden Liquid-Liquid Interfaces.

In this study, we show that hydrophilic nanoparticles can readily desorb from liquid-liquid interfaces in the presence of surfactants that do not change the wettability of the particles. Our observations are based on a simple theoretical approach to assess the number of adsorbed particles at the surfactant-laden liquid-liquid interface. We test this approach by studying the interfacial self-assembly of equally charged particles and lipids dissolved in separate immiscible phases. Hence, we investigate the interfacial adsorption of aminated silica particles (80 nm) and octadecylamine to the decane/water interface by interfacial tension measurements, which are supplemented by interfacial rheology of the adsorbed interfacial films, scanning electron microscopy images of Langmuir-Blodgett films, and measurements of the three-phase contact angle of the particle surface in the presence of surfactants. The measurements show that particles adsorb at the surfactant-laden interface at all investigated surfactant concentrations and compete with the surfactants for interfacial coverage. Additionally, the wettability of the hydrophilic particles does not change in the presence of the lipids, except for the highest investigated lipid concentration. Comparing the adsorption energies of one particle and of the lipids as a function of the particle contact angle provides an estimate of the tendency for interfacial adsorption of particles from which the particle coverage can be assessed. Based on these findings, equally charged particles and lipids show a competitive behavior at the interface determined by the bulk surfactant concentration and the attachment energies of the particles at the interface. This leads to a simple mechanistic model demonstrating that particles can readily desorb from the interface due to direct displacement by surfactants, which are loosely adsorbed at the oil-facing particle side. This mechanism critically lowers the otherwise high interfacial energy barrier against particle desorption, which otherwise would lead to virtually irreversible particle attachment at the interface.

Microbial fuel cell performance of graphitic carbon functionalized porous polysiloxane based ceramic membranes.

Proton-conducting porous ceramic membranes were synthesized via a polymer-derived ceramic route and probed in a microbial fuel cell (MFC). Their chemical compositions were altered by adding carbon allotropes including graphene oxide (GO) and multiwall carbon nanotubes into a polysiloxane matrix as filler materials. Physical characteristics of the synthesized membranes such as porosity, hydrophilicity, mechanical stability, ion exchange capacity, and oxygen mass transfer coefficient were determined to investigate the best membrane material for further testing in MFCs. The ion exchange capacity of the membrane increased drastically after adding 0.5 wt% of GO at an increment of 9 fold with respect to that of the non-modified ceramic membrane, while the oxygen mass transfer coefficient of the membrane decreased by 52.6%. The MFC operated with this membrane exhibited a maximum power density of 7.23 W m-3 with a coulombic efficiency of 28.8%, which was significantly higher than the value obtained using polymeric Nafion membrane. Hence, out of all membranes tested in this study the GO-modified polysiloxane based ceramic membranes are found to have a potential to replace Nafion membranes in pilot scale MFCs.

Embedding live bacteria in porous hydrogel/ceramic nanocomposites for bioprocessing applications.

In this work, we present a biocompatible one-pot processing route for ceramic/hydrogel nanocomposites in which we embed live bacteria. In our approach, we fabricate a highly stable alginate hydrogel with minimal shrinkage, highly increased structural and mechanical stability, as well as excellent biocompatibility. The hydrogel was produced by ionotropic gelation and reinforced with alumina nanoparticles to form a porous 3D network. In these composite gels, the bacteria Escherichia coli and Bacillus subtilis were embedded. The immobilized bacteria showed high viability and similar metabolic activity as non-embedded cells. Even after repeated glucose consumption cycles, the material maintained high structural stability with stable metabolic activity of the immobilized bacteria. Storing the bionanocomposite for up to 60 days resulted in only minor loss of activity. Accordingly, this approach shows great potential for producing macroscopic bioactive materials for biotechnological processes.

Polysiloxane microspheres encapsulated in carbon allotropes: A promising material for supercapacitor and carbon dioxide capture.

Recently, hierarchical porous materials have received tremendous attention in electrochemical supercapacitors and CO2 adsorption. Both areas of application have a positive impact on global warming by reducing CO2 emissions to the atmosphere. Herein, we synthesized new silica-based ceramic monoliths composed of polysiloxane microspheres sheathed by carbon allotropes (Graphene or MWCNT) and metal nanoparticles. The as-synthesized hybrid ceramics show a high specific surface area of 540 m2 g-1 with hierarchical micro-/meso-/macroporous structures. With the structural benefits, the obtained ceramics exhibits excellent performance in supercapacitors and for CO2 adsorption as probed in this study. As an electrode material for supercapacitor, the hybrid ceramics delivered the specific capacitance of 93 F/g at 2 mV s-1 in 0.5 M KOH electrolyte solution with a capacity retention of 88% after 50 cycles. Further, as a solid adsorbent, the hybrid ceramics shows the maximum CO2 adsorption capacity of 2 mmol g-1 at 100 kPa equilibrium pressure and 303 K, while maintaining 98% capacity retention after 10 cycles. Thus, the hybrid ceramics with its unusual properties make them a promising candidate for both, supercapacitors and CO2 capture in the sheer physical adsorption process.

Selective, Agglomerate-Free Separation of Bacteria Using Biofunctionalized, Magnetic Janus Nanoparticles.

This study presents a scalable method for designing magnetic Janus nanoparticles, which are capable of performing bacterial capture, while preventing agglomeration between bacterial cells. To this end, we prepared silica-coated magnetite Janus nanoparticles functionalized with a bacteria-specific antibody on one side and polyethylene glycol chains on the other, using the established wax-in-water emulsion strategy. These magnetic Janus nanoparticles specifically interact with one type of bacteria from a mixture of bacteria via specific antigen-antibody interactions. Contrarily to bacterial capture with isotropically functionalized particles, the bacterial suspensions remain free from cell-nanoparticle-cell agglomerates, owing to the passivation coating with polyethylene glycol chains attached to the half of the magnetic nanoparticles pointing away from the bacterial surface after capture. The selective magnetic capture of Escherichia coli cells was achieved from a mixture with Staphylococcus simulans without compromising bacterial viability and with an efficiency over 80%. This approach is a promising method for rapid and agglomeration-free separation of live bacteria for identification, enrichment, and cell counting of bacteria from biological samples.

Vibrational Spectroscopy as a Promising Toolbox for Analyzing Functionalized Ceramic Membranes.

Ceramic materials find use in many fields including the life sciences and environmental engineering. For example, ceramic membranes have shown to be promising filters for water treatment and virus retention. The analysis of such materials, however, remains challenging. In the present study, the potential of three vibrational spectroscopic methods for characterizing functionalized ceramic membranes for water treatment is evaluated. For this purpose, Raman scattering, infrared (IR) absorption, and solvent infrared spectroscopy (SIRS) were employed. The data were analyzed with respect to spectral changes as well as using principal component analysis (PCA). The Raman spectra allow an unambiguous discrimination of the sample types. The IR spectra do not change systematically with functionalization state of the material. Solvent infrared spectroscopy allows a systematic distinction and enables studying the molecular interactions between the membrane surface and the solvent.

Supercritical CO2 impregnation of PLA/PCL films with natural substances for bacterial growth control in food packaging.

Biodegradable polymers with antibacterial properties are highly desirable materials for active food packaging applications. Thymol, a dietary monoterpene phenol with a strong antibacterial activity is abundant in plants belonging to the genus Thymus. This study presents two approaches for supercritical CO2 impregnation of poly(lactic acid)(PLA)/poly(ε-caprolactone)(PCL) blended films to induce antibacterial properties of the material: (i) a batch impregnation process for loading pure thymol, and (ii) an integrated supercritical extraction-impregnation process for isolation of thyme extract and its incorporation into the films, operated in both batch or semi-continuous modes with supercritical solution circulation. The PCL content in films, impregnation time and CO2 flow regime were varied to maximize loading of the films with thymol or thyme extract with preserving films' structure and thermal stability. Representative film samples impregnated with thymol and thyme extract were tested against Gram (-) (Escherichia coli) and Gram(+) (Bacillus subtilis) model strains, by measuring their metabolic activity and re-cultivation after exposure to the films. The film containing thymol (35.8 wt%) showed a strong antibacterial activity leading to a total reduction of bacterial cell viability. Proposed processes enable fast, controlled and organic solvent-free fabrication of the PLA/PCL films containing natural antibacterial substances at moderately low temperature, with a compact structure and a good thermal stability, for potential use as active food packaging materials.

A New Clinically Relevant T-Score Standard to Interpret Bone Status in a Sheep Model.

BACKGROUND Osteoporosis is diagnosed by bone loss using a radiological parameter called T-score. Preclinical studies use DXA to evaluate bone status were the T-score is referenced on bone mineral density (BMD) values of the same animals before treatment. Clinically, the reference BMD represents values of an independent group of healthy patients around 30 years old. The present study established a clinically similar T-score standard to diagnose osteoporosis in a sheep model. MATERIAL AND METHODS We used 31 female merino land sheep (average 5.5 years old) to study osteoporosis. The following groups were compared using DXA measurement: 1) control; 2) ovariectomized (OVX); 3) OVX combined with a deficient diet (OVXD); and 4) OVXD combined with methylprednisolone administration (OVXDS). Further, an independent group of 32 healthy sheep (4-6 years old) were measured as an independent baseline. BMD was measured at 0 months, 3 months, and 8 months after treatment. RESULTS The same significance pattern between the treated groups and either baseline groups was seen. However, using an independent baseline changed the "clinical" interpretation of the data from an osteoporotic bone status (T-score <-2.5) after 3 months of OXDS treatment into an osteopenic bone status (T-score <-1.5 to -2.4). CONCLUSIONS Using an independent baseline enhanced the statistical significance and showed the clinical relevance. Furthermore, an independent baseline is a reliable alternative to use of a new control group for future experiments and thus reduces the number of animals needed by eliminating the need for a control and corresponding to clinical practice.

A novel, hydroxyapatite-based screw-like device for anterior cruciate ligament (ACL) reconstructions.

BACKGROUND: Rupture of the anterior cruciate ligament (ACL) is one of the most common injuries of the knee. Common techniques for ACL reconstruction require a graft fixation using interference screws. Nowadays, these interference screws are normally made of titanium or polymer/ceramic composites. The main challenge of application of a fixation device made entirely of bioactive ceramic is in relation to the low strength of such materials. The purpose of this study was to evaluate a novel geometry for a fixation device made of pure hydroxyapatite for ACL reconstructions that can overcome some problems of the titanium and the polymer/ceramic screws. METHODS: Finite Element Analysis was used for optimization of the stress distribution in conventional interference screw geometry. For experimental evaluation of the new fixation device, ex vivo tests were performed. RESULTS: The innovative screw-like fixation device is characterized by multiple threads with a large thread pitch. The novel design enabled the insertion of the screw into the bone without the application of an external torque or a screwdriver. In turn, it also allowed for the use of low-strength and high-bioactivity materials, like hydroxyapatite. Ex vivo tests showed that the novel screw can sustain pull-out forces up to 476 N, which is comparable to that of the commercially available BioComposite™ interference screws (Arthrex Inc., Germany), as a reference. CONCLUSIONS: In summary, the novel screw design is a promising strategy to develop all-ceramic fixation devices for ACL reconstructions, which may eliminate some drawbacks of the current interference screws.