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Laurie B. Gower - One of the best experts on this subject based on the ideXlab platform.
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Influence of fluoride on the mineralization of collagen via the polymer-induced Liquid-Precursor (PILP) process
Dental Materials, 2018Co-Authors: Neha Saxena, Maegan A. Cremer, Evan S. Dolling, Hamid Nurrohman, Stefan Habelitz, Grayson W. Marshall, Laurie B. GowerAbstract:Objective: The polymer-induced Liquid-Precursor (PILP) mineralization process has been shown to remineralize artificial dentin lesions to levels consistent with those of native dentin. However, nanoindentation revealed that the moduli of those remineralized lesions were only ∼50% that of native dentin. We hypothesize that this may be due to the PILP process having been previously optimized to obtain high amounts (∼70 wt%) of intrafibrillar crystals, but without sufficient interfibrillar mineral, another significant component of dentin. Methods: Fluoride was added to the PILP-mineralization of collagen from rat tail tendon at varying concentrations to determine if a better balance of intra- versus inter-fibrillar mineralization could be obtained, as determined by electron microscopy. Nanoindentation was used to determine if fluoridated apatite could improve the mechanical properties of the composites. Results: Fluoride was successfully incorporated into the PILP-mineralization of rat tail tendon and resulted in collagen-mineral composite systems with the mineral phase of hydroxyapatite containing various levels of fluoridation. As the fluoride concentration increased, the crystals became larger and more rod-like, with an increasing tendency to form on the fibril surfaces rather than the interior. Nanomechanical testing of the mineralized tendons revealed that fluoride addition did not increase modulus over PILP mineralization alone. This likely resulted from the separated nature of collagen fibrils that comprise tendon, which does not provide lateral reinforcement and therefore may not be suited for the compressive loads of nanoindentation. Significance: This work contributes to the development of minimally invasive approaches to caries treatment by determining if collagen can be functionally mineralized.
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functional remineralization of dentin lesions using polymer induced Liquid Precursor process
PLOS ONE, 2012Co-Authors: Anora K Burwell, Laurie B. Gower, Taili Thulamata, Stefan Habeliz, Michael P Kurylo, Yungching Chien, Jing Cheng, Nancy F Cheng, Stuart A Gansky, Sally J MarshallAbstract:It was hypothesized that applying the polymer-induced Liquid-Precursor (PILP) system to artificial lesions would result in time-dependent functional remineralization of carious dentin lesions that restores the mechanical properties of demineralized dentin matrix. 140 µm deep artificial caries lesions were remineralized via the PILP process for 7-28 days at 37°C to determine temporal remineralization characteristics. Poly-L-aspartic acid (27 KDa) was used as the polymeric process-directing agent and was added to the remineralization solution at a calcium-to-phosphate ratio of 2.14 (mol/mol). Nanomechanical properties of hydrated artificial lesions had a low reduced elastic modulus (E(R) = 0.2 GPa) region extending about 70 μm into the lesion, with a sloped region to about 140 μm where values reached normal dentin (18-20 GPa). After 7 days specimens recovered mechanical properties in the sloped region by 51% compared to the artificial lesion. Between 7-14 days, recovery of the outer portion of the lesion continued to a level of about 10 GPa with 74% improvement. 28 days of PILP mineralization resulted in 91% improvement of E(R) compared to the artificial lesion. These differences were statistically significant as determined from change-point diagrams. Mineral profiles determined by micro x-ray computed tomography were shallower than those determined by nanoindentation, and showed similar changes over time, but full mineral recovery occurred after 14 days in both the outer and sloped portions of the lesion. Scanning electron microscopy and energy dispersive x-ray analysis showed similar morphologies that were distinct from normal dentin with a clear line of demarcation between the outer and sloped portions of the lesion. Transmission electron microscopy and selected area electron diffraction showed that the starting lesions contained some residual mineral in the outer portions, which exhibited poor crystallinity. During remineralization, intrafibrillar mineral increased and crystallinity improved with intrafibrillar mineral exhibiting the orientation found in normal dentin or bone.
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a metastable Liquid Precursor phase of calcium carbonate and its interactions with polyaspartate
Faraday Discussions, 2012Co-Authors: Mark Alan Bewernitz, Denis Gebauer, Joanna R Long, Helmut Colfen, Laurie B. GowerAbstract:Invertebrate organisms that use calcium carbonate extensively in the formation of their hard tissues have the ability to deposit biominerals with control over crystal size, shape, orientation, phase, texture, and location. It has been proposed by our group that charged polyelectrolytes, like acidic proteins, may be employed by organisms to direct crystal growth through an intermediate Liquid phase in a process called the polymer-induced Liquid-Precursor (PILP) process. Recently, it has been proposed that calcium carbonate crystallization, even in the absence of any additives, follows a non-classical, multi-step crystallization process by first associating into a Liquid Precursor phase before transition into solid amorphous calcium carbonate (ACC) and eventually crystalline calcium carbonates. In order to determine if the PILP process involves the promotion, or stabilization, of a naturally occurring Liquid Precursor to ACC, we have analyzed the formation of saturated and supersaturated calcium carbonate–bicarbonate solutions using Ca2+ ion selective electrodes, pH electrodes, isothermal titration calorimetry, nanoparticle tracking analysis, 13C T2 relaxation measurements, and 13C PFG-STE diffusion NMR measurements. These studies provide evidence that, in the absences of additives, and at near neutral pH (emulating the conditions of biomineralization and biomimetic model systems), a condensed phase of Liquid-like droplets of calcium carbonate forms at a critical concentration, where it is stabilized intrinsically by bicarbonate ions. In experiments with polymer additive, the data suggests that the polymer is kinetically stabilizing this Liquid condensed phase in a distinct and pronounced fashion during the so called PILP process. Verification of this Precursor phase and the stabilization that polymer additives provide during the PILP process sheds new light on the mechanism through which biological organisms can exercise such control over deposited CaCO3 biominerals, and on the potential means to generate in vitro mineral products with features that resemble biominerals seen in nature.
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oriented hydroxyapatite in turkey tendon mineralized via the polymer induced Liquid Precursor pilp process
CrystEngComm, 2011Co-Authors: Rajendra Kumar Kasinath, Sang Soo Jee, Elaine Dimasi, Yiyeoun Kim, Laurie B. GowerAbstract:Bone is a hierarchically structured composite which imparts it with unique mechanical properties and bioresorptive potential. These properties are primarily influenced by the underlying nanostructure of bone, which consists of nanocrystals of hydroxyapatite embedded and uniaxially aligned within collagen fibrils. There is also a small fraction of non-collagenous proteins in bone, and these are thought to play an important role in bone's formation. In our in vitro model system of bone formation, polyanionic peptides are used to mimic the role of the non-collagenous proteins. In our prior studies, we have shown that intrafibrillar mineralization can be achieved in synthetic reconstituted collagen sponges using a polymer-induced Liquid-Precursor (PILP) mineralization process. This led to a nanostructured arrangement of hydroxyapatite crystals within the individual fibrils which closely mimics that of bone. This report demonstrates that biogenic collagen scaffolds obtained from turkey tendon, which consist of densely packed and oriented collagen fibrils, can also be mineralized by the PILP process. Synchrotron X-ray diffraction studies show that the mineralization process leads to a high degree of crystallographic orientation at the macroscale, thus emulating that found in the biological system of naturally mineralizing turkey tendon.
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development of bone like composites via the polymer induced Liquid Precursor pilp process part 1 influence of polymer molecular weight
Acta Biomaterialia, 2010Co-Authors: Taili T Thula, Laurie B. GowerAbstract:Abstract Bone is an organic–inorganic composite consisting primarily of collagen fibrils and hydroxyapatite crystals intricately interlocked to provide skeletal and metabolic functions. Non-collagenous proteins (NCPs) are also present, and although only a minor component, the NCPs are thought to play an important role in modulating the mineralization process. During secondary bone formation, an interpenetrating structure is created by intrafibrillar mineralization of the collagen matrix. Many researchers have tried to develop bone-like collagen–hydroxyapatite (HA) composites via the conventional crystallization process of nucleation and growth. While those methods have been successful in inducing heterogeneous nucleation of HA on the surface of collagen scaffolds, they have failed to produce a composite with the interpenetrating nanostructured architecture of bone. Our group has shown that intrafibrillar mineralization of type I collagen can be achieved using a polymer-induced Liquid-Precursor (PILP) process. In this process, acidic polypeptides are included in the mineralization solution to mimic the function of the acidic NCPs, and in vitro studies have found that acidic peptides such as polyaspartate induce a Liquid-phase amorphous mineral Precursor. Using this PILP process, we have been able to prepare collagen–HA composites with the fundamental nanostructure of bone, wherein HA nanocrystals are embedded within the collagen fibrils. This study shows that through further optimization a very high degree of mineralization can be achieved, with compositions matching that of bone. Synthetic collagen sponges were mineralized with calcium phosphate while analyzing various parameters of the reaction, with the focus of this report on the molecular weight of the polymeric process-directing agent. In order to determine whether intrafibrillar mineralization was achieved, an in-depth characterization of the mineralized composites was performed, including wide-angle X-ray diffraction, electron microscopy and thermogravimetric analyses. The results of this work lead us closer to the development of bone-like collagen–HA composites that could become the next generation of synthetic bone grafts.
Andreas Taubert - One of the best experts on this subject based on the ideXlab platform.
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cuo nanoparticles from the strongly hydrated ionic Liquid Precursor ilp tetrabutylammonium hydroxide evaluation of the ethanol sensing activity
ACS Applied Materials & Interfaces, 2012Co-Authors: Andreas Taubert, Franziska Stange, Mathias Junginger, Christina Gunter, Mike Neumann, Alwin FriedrichAbstract:The sensing potential of CuO nanoparticles synthesized via precipitation from a water/ionic Liquid Precursor (ILP) mixture was investigated. The particles have a moderate surface area of 66 m2/g after synthesis, which decreases upon thermal treatment to below 5 m2/g. Transmission electron microscopy confirms crystal growth upon annealing, likely due to sintering effects. The as-synthesized particles can be used for ethanol sensing. The respective sensors show fast response and recovery times of below 10 s and responses greater than 2.3 at 100 ppm of ethanol at 200 °C, which is higher than any CuO-based ethanol sensor described so far.
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room temperature zno mesocrystal formation in the hydrated ionic Liquid Precursor ilp tetrabutylammonium hydroxide
Crystal Growth & Design, 2008Co-Authors: Andriy Shkilnyy, Andreas TaubertAbstract:Zinc oxide particles can be grown from the hydrated ionic Liquid Precursor (ILP) tetrabutylammonium hydroxide (TBAH) at room temperature. The final particles are micrometers in size and are so-called mesocrystals, that is, larger crystals composed of nanoscale building blocks. Electron microscopy and particle size analysis reveal that, unlike ZnO grown from aqueous solution, the particle number in the TBAH/water mixtures decreases with increasing reaction time. Initially, numerous small particles precipitate. They transform into fewer, but larger, mesocrystals composed of rod-like primary particles.
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lessons from a failed experiment zinc silicates with complex morphology by reaction of zinc acetate the ionic Liquid Precursor ilp tetrabutylammonium hydroxide tbah and glass
Materials, 2008Co-Authors: Yaroslav Z Khimyak, Andreas TaubertAbstract:At elevated temperatures, the ionic Liquid Precursor (ILP) tetrabutylammonium hydroxide reacts with zinc acetate and the glass wall of the reaction vessel. While the reaction of OH- with the glass wall is not surprising as such and could be considered a failed experiment, the resulting materials are interesting for a variety of applications. If done on purpose and under controlled conditions, the reaction with the glass wall results in uniform, well-defined hemimorphite Zn4Si2O7(OH)2·nH2O and willemite Zn2SiO4 microcrystals and films. Their morphology can be adjusted by variation of the reaction time and reaction temperature. The hemimorphite can be transformed to Zn2SiO4 via calcination. The process is therefore a viable approach for the fabrication of porous films on glass surfaces with potential applications as catalyst support, among others.
Joachim Maier - One of the best experts on this subject based on the ideXlab platform.
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carbon nanotube wiring of electrodes for high rate lithium batteries using an imidazolium based ionic Liquid Precursor as dispersant and binder a case study on iron fluoride nanoparticles
ACS Nano, 2011Co-Authors: Chilin Li, Lin Gu, Jianwei Tong, Joachim MaierAbstract:To meet the energy and power demands of lithium-based batteries, numerous nanostructured and -decorated material prototypes have been proposed. In particular for insulating electrodes, a decrease of grain size coupled with wiring by a conductive phase is quite effective in improving the electroactivity. In this work, we report a novel electron-wiring method using single-wall carbon nanotubes in an imidazolium-based ionic Liquid Precursor, which enables them to be well disentangled and dispersed, even unzipped. As a case study, in situ formed iron fluoride nanoparticles (∼10 nm) are collected into micrometer-sized aggregates after wiring of merely 5 wt % carbon nanotubes in weight. These composite materials act as cathodes and exhibit a remarkable improvement of capacity and rate performances (e.g., 220 mAh/g at 0.1C and 80 mAh/g at 10C) due to the construction of mixed conductive networks. Therein, the ionic Liquid remainder also serves as an in situ binder to generate a nanographene-coated fluoride, whic...
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carbon nanotube wiring of electrodes for high rate lithium batteries using an imidazolium based ionic Liquid Precursor as dispersant and binder a case study on iron fluoride nanoparticles
ACS Nano, 2011Co-Authors: Jianwei Tong, Joachim MaierAbstract:To meet the energy. and power demands of lithium-based batteries, numerous nanostructured and -decorated material prototypes have been proposed. In particular for insulating electrodes, a decrease of grain size coupled with wiring by,a conductive phase Is quite effective In Improving the electroactivity. In this work, we report a novel electron-wiring method using single-wall carbon nanotubes in an imidazolium-based ionic Liquid Precursor, which enables them to be well disentangled and dispersed, even unzipped. As a case study, in situ formed iron fluoride nanoparticles (similar to 10 nm) are collected into micrometer-sized aggregates after wiring of merely 5 wt % carbon nanotubes in weight. These composite materials act as cathodes and exhibit a remarkable improvement of capacity and rate performances (e.g., 220 mAh/g at 0.1C and 80 mAh/g at 10C) due to the construction of mixed conductive networks. Therein, the ionic Liquid remainder also serves as an in situ binder to generate a nanographene-coated fluoride, which can even run well without the addition of extra conductive carbon and binder. This nanotechnological procedure based on an ionic Liquid succeeds without applying high temperature and pressure and is a significant step forward in developing high-power lithium batteries.
Sang Soo Jee - One of the best experts on this subject based on the ideXlab platform.
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oriented hydroxyapatite in turkey tendon mineralized via the polymer induced Liquid Precursor pilp process
CrystEngComm, 2011Co-Authors: Rajendra Kumar Kasinath, Sang Soo Jee, Elaine Dimasi, Yiyeoun Kim, Laurie B. GowerAbstract:Bone is a hierarchically structured composite which imparts it with unique mechanical properties and bioresorptive potential. These properties are primarily influenced by the underlying nanostructure of bone, which consists of nanocrystals of hydroxyapatite embedded and uniaxially aligned within collagen fibrils. There is also a small fraction of non-collagenous proteins in bone, and these are thought to play an important role in bone's formation. In our in vitro model system of bone formation, polyanionic peptides are used to mimic the role of the non-collagenous proteins. In our prior studies, we have shown that intrafibrillar mineralization can be achieved in synthetic reconstituted collagen sponges using a polymer-induced Liquid-Precursor (PILP) mineralization process. This led to a nanostructured arrangement of hydroxyapatite crystals within the individual fibrils which closely mimics that of bone. This report demonstrates that biogenic collagen scaffolds obtained from turkey tendon, which consist of densely packed and oriented collagen fibrils, can also be mineralized by the PILP process. Synchrotron X-ray diffraction studies show that the mineralization process leads to a high degree of crystallographic orientation at the macroscale, thus emulating that found in the biological system of naturally mineralizing turkey tendon.
Wolfgang Tremel - One of the best experts on this subject based on the ideXlab platform.
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strong stabilization of amorphous calcium carbonate emulsion by ovalbumin gaining insight into the mechanism of polymer induced Liquid Precursor processes
Journal of the American Chemical Society, 2011Co-Authors: Stephan E. Wolf, Jork Leiterer, Franziska Emmerling, Vitaliy Pipich, Raul A Barrea, Wolfgang TremelAbstract:The impact of the ovo proteins ovalbumin and lysozyme—present in the first stage of egg shell formation—on the homogeneous formation of the Liquid amorphous calcium carbonate (LACC) Precursor, was studied by a combination of complementing methods: in situ WAXS, SANS, XANES, TEM, and immunogold labeling. Lysozyme (pI = 9.3) destabilizes the LACC emulsion whereas the glycoprotein ovalbumin (pI = 4.7) extends the lifespan of the emulsified state remarkably. In the light of the presented data: (a) Ovalbumin is shown to behave commensurable to the ‘polymer-induced Liquid Precursor’ (PILP) process proposed by Gower et al. Ovalbumin can be assumed to take a key role during eggshell formation where it serves as an effective stabilization agent for transient Precursors and prevents undirected mineralization of the eggshell. (b) It is further shown that the emulsified LACC carries a negative surface charge and is electrostatically stabilized. (c) We propose that the Liquid amorphous calcium carbonate is affected by...