A sustainable one-pot method to transform seashell waste calcium carbonate to osteoinductive hydroxyapatite micro-nanoparticles

We have developed a straightforward, one-pot, low-temperature hydrothermal method to transform oyster shell waste particles (bCCP) from the species Crassostrea gigas (Mg-calcite, 5 wt% Mg) into hydroxyapatite (HA) micro/nanoparticles. The influence of the P reagents (H3PO4, KH2PO4, and K2HPO4), P/bCCP molar ratios (0.24, 0.6, and 0.96), digestion temperatures (25-200 & DEG;C), and digestion times (1 week-2 months) on the transformation process was thoroughly investigated. At 1 week, the minimum temperature to yield the full transformation significantly reduced from 160 & DEG;C to 120 & DEG;C when using K2HPO4 instead of KH2PO4 at a P/bCCP ratio of 0.6, and even to 80 & DEG;C at a P/bCCP ratio of 0.96. The transformation took place via a dissolution-reprecipitation mechanism driven by the favorable balance between HA precipitation and bCCP dissolution, due to the lower solubility product of HA than that of calcite at any of the tested temperatures. Both the bCCP and the derived HA particles were cytocompatible for MG-63 human osteosarcoma cells and m17.ASC murine mesenchymal stem cells, and additionally, they promoted the osteogenic differentiation of m17.ASC, especially the HA particles. Because of their physicochemical features and biological compatibility, both particles could be useful osteoinductive platforms for translational applications in bone tissue engineering

Formation of Aragonitic Layered Structures from Kaolinite and Amorphous Calcium Carbonate Precursors

Clay materials have been an ever-present accoutrement of modern civilization; improvements to process these materials have quickened their utilization for use in complex multiaxial load-bearing structures. Specifically, with better methods to organize the constituent metal oxide components in clay, the distribution of characteristic nematic and smectic phases can be controlled. In this work, we utilize the interactions of an amorphous calcium carbonate phase with kaolinite to form a complex composite that can be organized into distinct hierarchical structures. We demonstrate that these ACC–kaolinite composites can maintain characteristic long-range-ordered layer-by-layer structures across many length scales, from nano- to millimeter, through convenient and economical processing at room temperature

Additive Speciation and Phase Behavior Modulating Mineralization

Natural and synthetic composite materials as yet elude a complete understanding of their formation from organic and inorganic constituents. Addressing the interactions between organic additives and metastable inorganic precursors during mineral nucleation and growth is a critical challenge. In this study, we elucidate additive-controlled mineralization by a novel approach for the in situ continuous monitoring of a widely applied diffusion-based methodology, assisted by the quantitative assessment of mineral nucleation. The formation of amorphous superstructures is attributed to a complex interplay between additives and mineral species viz. ions, ion-clusters, and amorphous precursors as well as a unique phase behavior of the additive molecules relative to the maturing mineral phase. A pH-dependent conditioning of nucleation and demixing of transient liquid-like additive-ion complexes are shown to play critical roles in tuning mineral architecture. Thus, the modulation of mineral precursors and mineralization conditions by additive species determine material composition and morphology

Distinct Effects of Avian Egg Derived Anionic Proteoglycans on the Early Stages of Calcium Carbonate Mineralization

Artículo de publicación ISIThis Communication addresses the effects of egg membrane- and shell-associated proteoglycans, namely, keratan sulfate and dermatan sulfate, respectively, on the nascent stages of CaCO3 mineralization. Composed of calcitic columns intimately associated with a collagen membrane, the mechanisms underlying mineral growth are regulated by biomolecules. Of these, the role of proteoglycans is crucial because of their defined temporal and spatial distributions that direct mineral growth. The proteoglycans analyzed here induce dissimilar effects on the early stages of calcium carbonate mineralization. Egg-membrane associated keratan sulfate has a stabilizing effect toward soluble calcium carbonate prenucleation clusters and promotes formation of phases with lower solubility products after nucleation. In contrast, dermatan sulfate destabilizes prenu&ation clusters and leads to more soluble phases of calcium carbonate postnudeation. The distinct effects of proteoglycans on calcium carbonate crystallization elucidate their unique spatiotemporal localization during egg mineralization.FONDECYT - Chilean Council for Science and Technology (CONICYT) 112017

Advanced Multiwavelength Detection in Analytical Ultracentrifugation

This work highlights significant advancements in detector hardware and software for multiwavelength analytical ultracentrifugation (MWL-AUC) experiments, demonstrating improvement in both the spectral performance and UV capabilities of the instrument. The hardware is an extension of the Open AUC MWL detector developed in academia and first introduced in 2006 by Bhattacharya et al. Additional modifications as well as new analytical methods available for MWL data have since been reported. The present work describes new and continuing improvements to the MWL detector, including mirror source and imaging optics, UV sensitive acquisition modes and revised data acquisition software. The marked improvement of experimental data promises to provide access to increasingly complex systems, especially semiconductor nanoparticles, synthetic polymers, biopolymers, and other chromophores absorbing in the UV. Details of the detection system and components are examined to reveal the influences on data quality and to guide further developments. The benchmark comparisons of data quality across platforms will also serve as a reference guide for evaluation of forthcoming commercial absorbance optics

Hierarchically Structured Vanadium Pentoxide–Polymer Hybrid Materials

Biomimetic composite materials consisting of vanadium pentoxide (V₂O₅) and a liquid crystal (LC) “gluing” polymer were manufactured exhibiting six structural levels of hierarchy, formed through LC phases. The organic matrix was a polyoxazoline with pendant cholesteryl and carboxyl units, forming a lyotropic phase with the same structural orientation extending up to hundreds of micrometers upon shearing, and binding to V₂O₅ <i>via</i> hydrogen bridges. Composites consisting of V₂O₅–LC polymer hybrid fibers with a pronounced layered structuring were obtained. The V₂O₅–LC polymer hybrid fibers consist of aligned V₂O₅ ribbons, composed of self-assembled V₂O₅ sheets, encasing a chiral nematic polymer matrix. The structures of the V₂O₅–LC polymer composites strongly depend on the preparation method, <i>i.e</i>., the phase-transfer method from aqueous to organic medium, in which the polymer forms LC phases. Notably, highly defined micro- and nanostructures were obtained when initiating the synthesis using V₂O₅ tactoids with preoriented nanoparticle building units, even when using isotropic V₂O₅ dispersions. Shear-induced hierarchical structuring of the composites was observed, as characterized from the millimeter and micrometer down to the nanometer length scales using complementary optical and electron microscopy, SAXS, μCT, and mechanical nanoindentation

Hierarchical Structuring of Liquid Crystal Polymer–Laponite Hybrid Materials

Biomimetic organic–inorganic composite materials were fabricated via one-step self-organization on three hierarchical levels. The organic component was a polyoxazoline with pendent cholesteryl and carboxyl (<i>N</i>-Boc-protected amino acid) side chains that was able to form a chiral nematic lyotropic phase and bind to positively charged inorganic faces of Laponite. The Laponite particles formed a mesocrystalline arrangement within the liquid-crystal (LC) polymer phase upon shearing a viscous dispersion of Laponite nanoparticles and LC polymer in DMF. Complementary analytical and mechanical characterization techniques (AUC, POM, TEM, SEM, SAXS, μCT, and nanoindentation) covering the millimeter, micrometer, and nanometer length scales reveal the hierarchical structures and properties of the composite materials consisting of different ratios of Laponite nanoparticles and liquid-crystalline polymer

Insect Cell Glycosylation and Its Impact on the Functionality of a Recombinant Intracrystalline Nacre Protein, AP24

The impacts of glycosylation on biomineralization protein function are largely unknown. This is certainly true for the mollusk shell, where glycosylated intracrystalline proteins such as AP24 (Haliotis rufescens) exist but their functions and the role of glycosylation remain elusive. To assess the effect of glycosylation on protein function, we expressed two recombinant variants of AP24: an unglycosylated bacteria-expressed version (rAP24N) and a glycosylated insect cell-expressed version (rAP24G). Our findings indicate that rAP24G is expressed as a single polypeptide containing variations in glycosylation that create microheterogeneity in rAP24G molecular masses. These post-translational modifications incorporate O- and N-glycans and anionic monosialylated and bisialylated, and monosulfated and bisulfated monosaccharides on the protein molecules. AFM and DLS experiments confirm that both rAP24N and rAP24G aggregate to form protein phases, with rAP24N exhibiting a higher degree of aggregation, compared to rAP24G. With regard to functionality, we observe that both recombinant proteins exhibit similar behavior within <i>in vitro</i> calcium carbonate mineralization assays and potentiometric titrations. However, rAP24G modifies crystal growth directions and is a stronger nucleation inhibitor, whereas rAP24N exhibits higher mineral phase stabilization and nanoparticle containment. We believe that the post-translational addition of anionic groups (via sialylation and sulfation), along with modifications to the protein surface topology, may explain the changes in glycosylated rAP24G aggregation and mineralization behavior, relative to rAP24N