Calcium Phosphate Biomineralization Research Articles

Fluorochemicals from fluorspar via a phosphate-enabled mechanochemical process that bypasses HF.

All fluorochemicals-including elemental fluorine and nucleophilic, electrophilic, and radical fluorinating reagents-are prepared from hydrogen fluoride (HF). This highly toxic and corrosive gas is produced by the reaction of acid-grade fluorspar (>97% CaF2) with sulfuric acid under harsh conditions. The use of fluorspar to produce fluorochemicals via a process that bypasses HF is highly desirable but remains an unsolved problem because of the prohibitive insolubility of CaF2. Inspired by calcium phosphate biomineralization, we herein disclose a protocol of treating acid-grade fluorspar with dipotassium hydrogen phosphate (K2HPO4) under mechanochemical conditions. The process affords a solid composed of crystalline K3(HPO4)F and K2-xCay(PO3F)a(PO4)b, which is found suitable for forging sulfur-fluorine and carbon-fluorine bonds.

Tunable Enzyme-Assisted Mineralization of Apatitic Calcium Phosphate by Homogeneous Catalysis

While it has long been mimicked by simple precipitation reactions under biologically relevant conditions, calcium phosphate biomineralization is a complex process, which is highly regulated by physicochemical factors and involves a variety of proteins and other biomolecules. Alkaline phosphatase (ALP), in particular, is a conductor of sorts, directly regulating the amount of orthophosphate ions available for mineralization. Herein, we explore enzyme-assisted mineralization in the homogeneous phase as a method for biomimetic mineralization and focus on how relevant ionic substitution types affect the obtained minerals. For this purpose, mineralization is performed over a range of enzyme substrate concentrations and fluoride concentrations at physiologically relevant conditions (pH 7.4, T = 37 °C). Refinement of X-ray diffraction data is used to study the crystallographic unit cell parameters for evidence of ionic substitution in the lattice, and infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) are used for complementary information regarding the chemical composition of the minerals. The results show the formation of substituted hydroxyapatite (HAP) after 48 h mineralization in all conditions. Interestingly, an expansion of the crystalline unit cell with an increasing concentration of the enzyme substrate is observed, with only slight changes in the particle morphology. On the contrary, by increasing the amount of fluoride, while keeping the enzyme substrate concentration unchanged, a contraction of the crystalline unit cell and the formation of elongated, well-crystallized rods are observed. Complementary IR and XPS data indicate that these trends are explained by the incorporation of substituted ions, namely CO32- and F-, in the HAP lattice at different positions.

In Situ Fluorescence Probing of the Formation of Calcium Phosphate Prenucleation Clusters.

Initial-stage prenucleation clusters (PNCs) are critical in calcium phosphate (CaP) biomineralization and thus the formation mechanisms of human bones and teeth. However, several features of PNCs require further examination, e.g., structure, ionic stoichiometry, kinetics, thermodynamics, and nucleation mechanism. In this study, we used poly(acrylic acid) (PAA)-Ca(Eu) complexes with partial Eu3+ substitution as pre-PNCs and established a fluorescence method to study PNC formation in situ based on Eu-O charge-transfer transitions. The kinetics and thermodynamics of PNC formation were explored by probing the fluorescence changes of Eu-O charge-transfer transitions during bonding between the pre-PNCs and PO43-. PNC formation was consistent with the pseudo-second-order kinetic and Langmuir isothermal adsorption models. The flexible structures of PNCs aided in regulating the subsequent nucleation and crystallization. This study provides an in situ fluorescence probing method with critical guiding significance in addressing the features of PNC formation, in addition to biomineralization.

APATITIC NANOPOWDERS AND COATINGS: A COMPREHENSIVE REVIEW

The use of artificial biomaterials has been acclaiming potential therapeutic scope in diverse clinical applications. This review started with the description of the basics of biomaterials, and desirable properties, which are the prerequisites to understand biomaterials. The orthopedic biomaterials, their classification and the importance of calcium phosphate (CaP) materials for hard-tissue applications were utterly discussed. Furthermore, among the various CaP biominerals, the importance of hydroxyapatite (HAP) and its synthesis techniques was comprehensively reviewed. The sol–gel route for the synthesis of HAP nanoparticles and deposition of coatings were systematically studied. Among the metallic substrates, Ti6Al4V alloy remained the focus of this study. Moreover, several film pre-preparation methods were also given due importance. The importance of other surface modification techniques, especially in the context of Ti6Al4V substrates, was also discussed. Among several coating techniques to deposit CaP coatings, special attention was paid to the spin and dip coating techniques. In addition to monolithic HAP coatings, reinforced and antimicrobial HAP coatings were also reviewed from broad perspectives. Therefore, this review provides an in-depth insight into the preparation and properties of apatitic nanoparticles and their coatings for orthopedic and dental applications.

Enzymatic Approach in Calcium Phosphate Biomineralization: A Contribution to Reconcile the Physicochemical with the Physiological View.

Biomineralization is the process by which organisms produce hard inorganic matter from soft tissues with outstanding control of mineral deposition in time and space. For this purpose, organisms deploy a sophisticated “toolkit” that has resulted in significant evolutionary innovations, for which calcium phosphate (CaP) is the biomineral selected for the skeleton of vertebrates. While CaP mineral formation in aqueous media can be investigated by studying thermodynamics and kinetics of phase transitions in supersaturated solutions, biogenic mineralization requires coping with the inherent complexity of biological systems. This mainly includes compartmentalization and homeostatic processes used by organisms to regulate key physiological factors, including temperature, pH and ion concentration. A detailed analysis of the literature shows the emergence of two main views describing the mechanism of CaP biomineralization. The first one, more dedicated to the study of in vivo systems and supported by researchers in physiology, often involves matrix vesicles (MVs). The second one, more investigated by the physicochemistry community, involves collagen intrafibrillar mineralization particularly through in vitro acellular models. Herein, we show that there is an obvious need in the biological systems to control both where and when the mineral forms through an in-depth survey of the mechanism of CaP mineralization. This necessity could gather both communities of physiologists and physicochemists under a common interest for an enzymatic approach to better describe CaP biomineralization. Both homogeneous and heterogeneous enzymatic catalyses are conceivable for these systems, and a few preliminary promising results on CaP mineralization for both types of enzymatic catalysis are reported in this work. Through them, we aim to describe the relevance of our point of view and the likely findings that could be obtained when adding an enzymatic approach to the already rich and creative research field dealing with CaP mineralization. This complementary approach could lead to a better understanding of the biomineralization mechanism and inspire the biomimetic design of new materials.

Dopamine-Mediated Biomineralization of Calcium Phosphate as a Strategy to Facilely Synthesize Functionalized Hybrids.

Organic-inorganic hybrid materials have been considered to be promising carriers or immobilization matrixes for biomolecules due to their high efficiency and significantly enhanced activities and stabilities of biomolecules. Here, the well-defined dopamine/calcium phosphate organic-inorganic hybrids (DACaPMFs) are fabricated via one-pot dopamine-mediated biomineralization, and their structure and properties are also characterized. Direct stochastic optical reconstruction microscopy (dSTORM) is first used to probe the distribution of organic components in these hybrids. Combined with spectroscopic data, the direct observation of dopamine in the hybrids helps to understand the formation of a physical chemistry mechanism of the biomineralization. The obtained DACaPMFs with multiple-level pores allow the loading of doxorubicin with a high loading efficiency and a pH-responsive property. Furthermore, thrombin is entrapped by the hybrids to prove the controlled release. It is expected that such organic-inorganic hybrid materials may hold great promise for application in drug delivery as well as scaffold materials in bone tissue engineering and hemostatic material.

A Novel Magnetotactic Alphaproteobacterium Producing Intracellular Magnetite and Calcium-Bearing Minerals.

Magnetotactic bacteria (MTB) are prokaryotes that form intracellular magnetite (Fe3O4) or greigite (Fe3S4) nanocrystals with tailored sizes, often in chain configurations. Such magnetic particles are each surrounded by a lipid bilayer membrane, called a magnetosome, and provide a model system for studying the formation and function of specialized internal structures in prokaryotes. Using fluorescence-coupled scanning electron microscopy, we identified a novel magnetotactic spirillum, XQGS-1, from freshwater Xingqinggong Lake, Xi'an City, Shaanxi Province, China. Phylogenetic analyses based on 16S rRNA gene sequences indicate that strain XQGS-1 represents a novel genus of the Alphaproteobacteria class in the Proteobacteria phylum. Transmission electron microscopy analyses reveal that strain XQGS-1 forms on average 17 ± 3 magnetite magnetosome particles with an ideal truncated octahedral morphology, with an average length and width of 88.3 ± 11.7 nm and 83.3 ± 11.0 nm, respectively. They are tightly organized into a single chain along the cell long axis close to the concave side of the cell. Intrachain magnetic interactions likely result in these large equidimensional magnetite crystals behaving as magnetically stable single-domain particles that enable bacterial magnetotaxis. Combined structural and chemical analyses demonstrate that XQGS-1 cells also biomineralize intracellular amorphous calcium phosphate (2 to 3 granules per cell; 90.5- ± 19.3-nm average size) and weakly crystalline calcium carbonate (2 to 3 granules per cell; 100.4- ± 21.4-nm average size) in addition to magnetite. Our results expand the taxonomic diversity of MTB and provide evidence for intracellular calcium phosphate biomineralization in MTB. IMPORTANCE Biomineralization is a widespread process in eukaryotes that form shells, teeth, or bones. It also occurs commonly in prokaryotes, resulting in more than 60 known minerals formed by different bacteria under wide-ranging conditions. Among them, magnetotactic bacteria (MTB) are remarkable because they might represent the earliest organisms that biomineralize intracellular magnetic iron minerals (i.e., magnetite [Fe3O4] or greigite [Fe3S4]). Here, we report a novel magnetotactic spirillum (XQGS-1) that is phylogenetically affiliated with the Alphaproteobacteria class. In addition to magnetite crystals, XQGS-1 cells form intracellular submicrometer calcium carbonate and calcium phosphate granules. This finding supports the view that MTB are also an important microbial group for intracellular calcium carbonate and calcium phosphate biomineralization.

Functional derivatives of human dentin matrix protein 1 modulate morphology of calcium carbonate crystals.

Dentin matrix protein 1 (DMP1) is an acidic, extracellular matrix protein essential for biomineralization of calcium phosphate, in bone and dentin. It is proteolytically processed into two fragments, 44K and 56K. Recently, the presence of DMP1 was noticed in inner ear, specifically in otoconia, which are calcium carbonate biominerals involved in sensing of balance. In this study, the solution structure and biomineralization activity of otoconial 44K and 56K fragments toward calcium carbonate were investigated. The results of analytical ultracentrifugation, circular dichroism, and gel filtration indicated that DMP1 fragments are disordered in solution. Notably, 56K formed oligomers in the presence of calcium ions. It was also observed that both fragments influenced the crystal growth by in vitro biomineralization assay and scanning electron microscopy. In addition, they sequester the calcium ions during the calcite formation. Calcium carbonate crystals precipitated in vitro changed their size and shape in the presence of DMP1 fragments. Oligomerization propensity of 56K may significantly enhance this function. Our study indicates that intrinsically disordered DMP1 has a previously unknown regulatory function for biomineralization of otoconia.

Simulation of Calcium Phosphate Prenucleation Clusters in Aqueous Solution: Association beyond Ion Pairing.

Classical molecular dynamics simulations and free energy methods have been used to obtain a better understanding of the molecular processes occurring prior to the first nucleation event for calcium phosphate biominerals. The association constants for the formation of negatively charged complexes containing calcium and phosphate ions in aqueous solution have been computed, and these results suggest that the previously proposed calcium phosphate building unit, [Ca(HPO4)3]4–, should only be present in small amounts under normal experimental conditions. However, the presence of an activation barrier for the removal of an HPO42– ion from this complex indicates that this species could be kinetically trapped. Aggregation pathways involving CaHPO4, [Ca(HPO4)2]2–, and [Ca(HPO4)3]4– complexes have been explored with the finding that dimerization is favorable up to a Ca/HPO4 ratio of 1:2.

Unstructured Proteins in Biological Structures: The Case of Human Teeth from a Protein Chemist's Perspective

Proteins are the biomacromolecules that work downstream to genes in every living system. It is these protein molecules that are responsible for a plethora of functions in our body, ranging from building skeleton tissues to transmitting signal from one place to others. There was a period when biologists have the view that for a protein to function, the structure is of supreme importance. Nevertheless, this structure‐function paradigm is fairly obeyed by most of the proteins, if not all of them. Last two decades have witnessed the increased reports of proteins that do not have a stable three‐dimensional structure but are very much indispensable for the cellular and biological activities. These unstructured proteins are now known as “Intrinsically disordered proteins” (IDPs). Interestingly, these IDPs function not only in isolation (e.g. transcription factors) but helps in the formation of hard tissues like teeth, bone, and mollusks shell, by governing a process called biomineralization. Biomineralization is the process by which living organisms produce minerals, often to harden or stiffen existing tissues. Such tissues are called mineralized tissues.We have isolated total protein extracts from a healthy molar, premolar, canine and incisor teeth. We studied their protein secondary structural characteristics using various biophysical techniques. We have also investigated the effects of these protein extracts on mineralization of calcium phosphate through in vitro biomineralization assay followed by size‐based measurement analysis via Nanoparticle tracking analysis (NTA). The biophysical studies confirmed the presence of IDPs in the majority within these protein extracts. Moreover, these extracts were shown to elevate calcium phosphate biomineralization in a time‐dependent manner. This is the first time the effect of the whole protein extract was taken into account which in our view more closely imitates the in vivo process of tooth biomineralization. Furthermore, we also evaluated the differential proteome profile of the individual type of human teeth through Mass spectroscopy‐based method. The comparative qualitative and quantitative data of proteins from these different human teeth were obtained. The implication of these results will be discussed.Support or Funding InformationThere was no support or funding from any organizationThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Biomineralization of calcium phosphate revealed by in situ liquid-phase electron microscopy

Calcium phosphate biomineralization is essential to the formation of bones and teeth, and other pathological calcifications. Unravelling the mechanism of calcium phosphate nucleation and growth contributes significantly to understanding diseases caused by pathological mineralization, and also to designing biomimetic materials with suitable properties. Recently, calcium phosphate was proposed to mineralize following a non-classical crystal growth pathway of pre-nucleation cluster aggregation. Liquid-phase transmission electron microscopy allows dynamic processes to be recorded continuously inside liquid. Here we present direct evidence, based on continuous monitoring in liquid, to confirm that calcium phosphate mineralization from simulated body fluid occurs by particle attachment, shown with nanoscale spatial resolution and sufficient temporal resolution. This work may lay the foundation for future investigation of mineralization in other relevant biological systems in humans and vertebrates.

Biomineralization of Calcium Phosphate and Calcium Carbonate within Iridescent Chitosan/Iota-Carrageenan Multilayered Films.

This work systematically explores the biomineralization of calcium phosphate (CaP) and carbonate (CaCO3) within chitosan/iota-carrageenan multilayer films. Multilayer films of chitosan and iota-carrageenan (up to 128-coupled layers) were prepared on glass substrates by a layer-by-layer dip-coating technique. Cryo-scanning electron microscopy revealed dense interfaces between the chitosan and iota-carrageenan layers with thicknesses in the range 250 and 350 nm in the hydrated state, accounting for the iridescent nature of multilayer films when wet. Immersion of the multilayered films in simulated body fluid or simulated seawater at 25 °C resulted in the mineralization of CaP and CaCO3, respectively, at the interfaces between the biopolymer layers and modified the iridescence of the films. Lamellar scattering features in small-angle neutron scattering measurements of the mineralized films provided evidence of the localized mineralization. Further evidence of this was found through the lack of change in the dynamic and static correlation lengths of the polymer networks within the bulk phase of the chitosan and iota-carrageenan layers. CaP mineralization occurred to a greater extent than CaCO3 mineralization within the films, evidenced by the higher lamellar density and greater rigidity of the CaP-mineralized films. Results provide valuable new insights into CaP and CaCO3 biomineralization in biopolymer networks.

Mechanisms of Modulation of Calcium Phosphate Pathological Mineralization by Mobile and Immobile Small-Molecule Inhibitors.

Potential pathways for inhibiting crystal growth are via either disrupting local microenvironments surrounding crystal-solution interfaces or physically blocking solute molecule attachment. However, the actual mode of inhibition may be more complicated due to the characteristic time scale for the inhibitor adsorption and relaxation to a well-bound state at crystal surfaces. Here we demonstrate the role of citrate (CA) and hydroxycitrate (HCA) in brushite (DCPD, CaHPO4·2H2O) crystallization over a broad range of both inhibitor concentrations and supersaturations by in situ atomic force microscopy (AFM). We observed that both inhibitors exhibit two distinct actions: control of surface crystallization by the decrease of step density at high supersaturations and the decrease of the [1̅00]Cc step velocity at high inhibitor concentration and low supersaturation. The switching of the two distinct modes depends on the terrace lifetime, and the slow kinetics along the [1̅00]Cc step direction provides specific sites for the newly formed dislocations. Molecular modeling shows the strong HCA-crystal interaction by molecular recognition, explaining the AFM observations for the formation of new steps and surface dissolution along the [101]Cc direction due to the introduction of strong localized strain in the crystal lattice. These direct observations highlight the importance of the inhibitor coverage on mineral surfaces, as well as the solution supersaturation in predicting the inhibition efficacy, and reveal an improved understanding of inhibition of calcium phosphate biomineralization, with clinical implications for the full therapeutic potential of small-molecule inhibitors for kidney stone disease.

Calcium phosphate in plant trichomes: the overlooked biomineral.

Calcium phosphate was unknown as a plant biomineral until recently reported in Neotropical Loasaceae. Here, we demonstrate its widespread occurrence in the trichomes of several plant families, including Brassicaceae. Calcium phosphate is the primary biomineral in, e.g., the bones and teeth of higher animals; in plants, it was only recently discovered in the stinging hairs and scabrid-glochidiate trichomes of South American Loasaceae (Ensikat et al. in Sci Rep UK 6:26073, 2016), where it appears to be deposited highly specifically, often replacing the common plant biomineral silica. We initiated a broader survey in a range of different plant orders to investigate a possibly wider distribution of calcium phosphate biomineralization in plants. Scanning electron microscopy with EDX element analysis and mapping was used for the detection of the biominerals: calcium phosphate, calcium carbonate, and silica in the trichomes of several common plant species of different orders. Results were authenticated with Raman spectroscopy. Calcium phosphate was found in the trichomes of several species in the orders Malpighiales, Rosales, Boraginales, and Brassicales. It occurred in trichome tips, replacing the more common silica, or together with silica and calcium carbonate at specific locations in the trichome cell walls. Most surprisingly, it was found in the trichomes of Arabidopsis thaliana, one of the most studied plant species-where it had been overlooked so far. The wide distribution of calcium phosphate as plant biomineral here demonstrated and the striking mineralization patterns with three different biominerals in the walls of single-celled trichomes underscore an unexpected complexity in plant biomineralization.

Energetic Basis for Inhibition of Calcium Phosphate Biomineralization by Osteopontin.

Calcium oxalate kidney stones form attached to Randall's plaques (RP), calcium phosphate (Ca-P) deposits on the renal papillary surface. Osteopontin (OPN) suppresses crystal growth in the complex process of urinary stone formation, but the inhibitory role of active domains of OPN involved in the initial formation of the RPs attached to epithelial cells has yet to be clarified. Here we demonstrate the thermodynamic basis for how OPN sequences regulate the onset of Ca-P mineral formation on lipid rafts as a model membrane. We first quantify the kinetics of hydroxyapatite (HAP) nucleation on membrane substrates having liquid-condensed (LC) and liquid-expanded (LE) phases using in situ atomic force microscopy (AFM). We find that rates are sequence-dependent, and the thermodynamic barrier to nucleation is reduced by minimizing the interfacial free energy γ. Combined with single-molecule determination of the binding energy (ΔGB) of the OPN peptide segments adsorbed to the HAP (100) face, we show a linear relationship of γ and ΔGB, suggesting that the increase in the nucleation barriers correlates with strong peptide-crystal nuclei binding. These findings reveal fundamental energetic clues for inhibition of membrane-mediated nucleation by sequence motifs and subdomains within the OPN protein through spatial location of charged moieties and provide insight connecting peripheral cell membranes to pathological mineralization.

A first report of hydroxylated apatite as structural biomineral in Loasaceae - plants' teeth against herbivores.

Biomineralization provides living organisms with various materials for the formation of resilient structures. Calcium phosphate is the main component of teeth and bones in vertebrates, whereas especially silica serves for the protection against herbivores on many plant surfaces. Functional calcium phosphate structures are well-known from the animal kingdom, but had not so far been reported from higher plants. Here, we document the occurrence of calcium phosphate biomineralization in the South-American plant group Loasaceae (rock nettle family), which have stinging trichomes similar to those of the well-known stinging nettles (Urtica). Stinging hairs and the smaller, glochidiate trichomes contained nanocrystalline hydroxylated apatite, especially in their distal portions, replacing the silica found in analogous structures of other flowering plants. This could be demonstrated by chemical, spectroscopic, and diffraction analyses. Some species of Loasaceae contained both calcium phosphate and silica in addition to calcium carbonate. The intriguing discovery of structural hydroxylated apatite in plants invites further studies, e.g., on its systematic distribution across the family, the genetic and cellular control of plant biomineralization, the properties and ultrastructure of calcium phosphate. It may prove the starting point for the development of biomimetic calcium phosphate composites based on a cellulose matrix.

Exploring architectures at the nanoscale: the interplay between hydrophobic twin lipid chains and head groups of designer peptide amphiphiles in the self-assembly process and application.

The self-assembly of peptide amphiphiles (PAs) is found to be governed by the hydrophobic interactions induced by the hydrophobic groups/number of alkyl chains and the hydrophilic head groups. In this study, an assessment of the nanostructures formed by the self-assembly of simple twin chained PAs was carried out and compared to their single chain/short analogues. The spectroscopic and microscopic analysis revealed the fact that the twin chained amphiphiles had a high inclination to form β-sheet nanofibers and further towards hydrogelation. The mixture of twin chained PAs also exhibited cooperative self-assembly with improved aggregation behavior, although not much augmentation in β-type structuring was found. In contrast, the single chain/short analogue containing PAs showed very less of β-sheet type structures to a lesser extent and no hydrogelating behavior but resulted in mostly random conformations. The increase in the number or alteration of polar head groups in double chained PAs induced higher extent of β-type conformation and better gelling capability due to the combined hydrophobic effect of the twin chains. The overall results delineated the dominance of hydrophobic interactions. Finally, calcium phosphate bio-mineralization was done in the hydrogels of twin chained PAs with the aim of developing future biomaterials.

Precipitation of Amorphous Calcium Oxalate in Aqueous Solution

Inspired by the observation that crystalline calcium carbonate and calcium phosphate biominerals frequently form via amorphous precursors, a wide range of studies have been performed which demonstrate that many inorganic crystals can precipitate from solution via amorphous phases. This article considers the crystallization mechanism of calcium oxalate, which is a significant biomineral in many plants and the primary constituent of kidney stones in vertebrates, and shows that this can also precipitate via an amorphous precursor phase from aqueous solution. A range of approaches were employed to study calcium oxalate formation, including precipitation in bulk solution in the presence and absence of additives and in the spatially confined volumes offered by track etched membranes and a crossed cylinders apparatus. A freeze concentration method was also used to generate sufficient quantities of amorphous calcium oxalate (ACO) for analysis. The results show that amorphous calcium oxalate crystallizes rapidly in bulk solution but can be significantly stabilized through the concerted activity of additives and confinement. We also demonstrate that ACO has a composition of ≈CaC2O4:H2O. These data suggest that calcium oxalate biominerals, in common with their carbonate and phosphate counterparts, may also precipitate via amorphous phases.

Enzyme-assisted calcium phosphate biomineralization on an inert alumina surface

In this study a bioinspired approach to induce self-mineralization of bone-like material on alumina surfaces is presented. The mineralizing enzyme alkaline phosphatase (ALP) is covalently immobilized by a carbodiimide-mediated chemoligation method. The enzymatic activity of immobilized ALP and its mineralization capability are investigated under acellular conditions as well as in the presence of human bone cells. Analytical, biochemical and immunohistochemical characterization show that ALP is efficiently immobilized, retains its activity and can trigger calcium phosphate mineralization on alumina at acellular conditions. In vitro cell tests demonstrate that ALP-functionalized alumina clearly boosts and enhances bone cell mineralization. Our results underpin the great potential of ALP-functionalized alumina for the development of bioactive surfaces for applications such as orthopaedic and dental implants, enabling a fast and firm implant osseointegration.

Chitosan/chondroitin sulfate multilayers as supports for calcium phosphate biomineralization

We investigated the interaction of natural derived macromolecular multilayers with calcium and phosphate ions entirely processed using the layer-by-layer (LbL) technique. A nanostructured multilayer component, with 5 or 10 bilayers, was first produced using weak polyelectrolyte biopolymers, chitosan and chondroitin sulfate. This was followed by sequential passing of solutions containing Ca2+ and PO43− over the multilayers. QCM-D, SEM and EDX results conferred the formation of calcium phosphate (CaP) over the polyelectrolyte multilayers. Initiation of precipitation was observed earlier in the 10 bilayers coating than in the 5 bilayers one. These results indicate the potential of multilayers to trap ions, as a biomimetic approach that can be used to induce CaP precipitation. This could enable the preparation of more performant bioactive composite biomaterials for orthopedic applications, including in bone tissue engineering.