Hydroxyapatite Mineral Research Articles

Revealing nanoscale mineralization pathways of hydroxyapatite using in situ liquid cell transmission electron microscopy.

To treat impairments in hard tissues or overcome pathological calcification in soft tissues, a detailed understanding of mineralization pathways of calcium phosphate materials is needed. Here, we report a detailed mechanistic study of hydroxyapatite (HA) mineralization pathways in an artificial saliva solution via in situ liquid cell transmission electron microscopy (TEM). It is found that the mineralization of HA starts by forming ion-rich and ion-poor solutions in the saliva solution, followed by coexistence of the classical and nonclassical nucleation processes. For the nonclassical path, amorphous calcium phosphate (ACP) functions as the substrate for HA nucleation on the ACP surface, while the classical path features direct HA nucleation from the solution. The growth of HA crystals on the surface of ACP is accompanied by the ACP dissolution process. The discoveries reported in this work are important to understand the physiological and pathological formation of HA minerals, as well as to engineer the biomineralization process for bone healing and hard tissue repairs.

L-histidine controls the hydroxyapatite mineralization with plate-like morphology: Effect of concentration and media

Hydroxyapatite (HA) is the main inorganic component of bone and dentin, and their non-stoichiometric compositions and plate-shaped morphology is responsible for their bioactivity and osteoconductive nature. Collagenous (CPs) and non-collagenous proteins (NCPs) facilitate mineralization and regulate structural properties of HA through their side-chains. The bioactivity of synthetic HA does not usually match with the HA found in bone and, therefore, there is a need to understand the role of biomolecules in bone mineralization in order to develop non-stoichiometric plate-shaped HA for bone grafts. Role of several amino acids has been investigated but the role of L-his has been rarely investigated under physiological conditions even though it is a part of HA inhibitor proteins, like albumin, amelogenin, and histidine-rich proteins. In this study, L-his and L-glu were used to modify the structural properties of HA in different experimental conditions and buffer systems (tris and hepes). The results showed that L-his was able to regulate the plate-shaped morphology of HA in every experimental condition, unlike the L-glu, where the crystal morphology was regulated by experimental conditions. Both amino acids behaved differently in DI water, tris, and hepes buffer, and the media used influenced the precipitation time and structural properties of HA. Hepes and tris buffers also influenced the HA precipitation process. Overall, the studies revealed that L-his may be used as an effective regulator of plate-shaped morphology of HA, instead of large NCPs/proteins, for designing biomaterials for bone regeneration applications and the choice of buffer system is important in designing and evaluating the systems for mineralization. In cell culture studies, mouse osteoblast precursor cells (MC3T3-E1) showed highest proliferation on the bone-like plate-shaped HA, among all the HA samples investigated.

The structural role of osteocalcin in bone biomechanics and its alteration in Type-2 Diabetes

This study presents an investigation into the role of Osteocalcin (OC) on bone biomechanics, with the results demonstrating that the protein’s α-helix structures play a critical role in energy dissipation behavior in healthy conditions. In the first instance, α-helix structures have high affinity with the Hydroxyapatite (HAp) mineral surface and provide favorable conditions for adsorption of OC proteins onto the mineral surface. Using steered molecular dynamics simulation, several key energy dissipation mechanisms associated with α-helix structures were observed, which included stick–slip behavior, a sacrificial bond mechanism and a favorable binding feature provided by the Ca2+ motif on the OC protein. In the case of Type-2 Diabetes, this study demonstrated that possible glycation of the OC protein can occur through covalent crosslinking between Arginine and N-terminus regions, causing disruption of α-helices leading to a lower protein affinity to the HAp surface. Furthermore, the loss of α-helix structures allowed protein deformation to occur more easily during pulling and key energy dissipation mechanisms observed in the healthy configuration were no longer present. This study has significant implications for our understanding of bone biomechanics, revealing several novel mechanisms in OC’s involvement in energy dissipation. Furthermore, these mechanisms can be disrupted following the onset of Type-2 Diabetes, implying that glycation of OC could have a substantial contribution to the increased bone fragility observed during this disease state.

Matrix Vesicle Mediated Mineralization - A Review

Teeth are composed of the mineralized tissues dentine and cementum, and a mineralized structure, thedental enamel. The pulp may also mineralize in response to aging processes and/or pathologic aggressions.The process of mineralization is specific for each dental tissue. Matrix vesicles have been implicated inthe mineralisation of calcified cartilage, bone and dentin. It is an orchestrated sequence of ultrastructuraland biochemical events that lead to crystal nucleation and growth. Matrix vesicles appear to mineralize byconcentrating calcium and phosphate at a protected site close to the inner leaflet of the vesicle membrane.Calcium may be attracted by its affinity for acidic phospholipids of the vesicle membrane, and phosphatemay be concentrated by the action of transmembrane phosphatases of the matrix vesicle membrane.Evidence is accumulating to suggest that alkaline phosphatase of the matrix vesicle membrane functionsas a phosphotransferase or phosphate vector, transporting PO4 across the vesicle membrane. The influx ofphosphate ions into the matrix vesicle is mediated by several proteins such as TNAP, ENPP1, Pit1, annexinand so forth. The catalytic activity of ENPP1 generates pyrophosphate (PPi) using extracellular ATPs as asubstrate, and the resultant PPi prevents crystal overgrowth. However, TNAP hydrolyzes PPi into phosphateion monomers, which are then transported into the matrix vesicle through Pit1. Accumulation of Ca2+ andPO43- inside matrix vesicles then induces crystalline nucleation, with calcium phosphate crystals budding offradially, puncturing the matrix vesicle’s membrane and finally growing out of it to form mineralized nodules.Their exact role, if any, in the nucleation of hydroxyapatite mineral, and its association with collagen fibresThe organic Matrix has been debated and is controversial. Several hypotheses have been recently introducedto explain in greater detail how Matrix vesicles function in biomineralization. This review will summariserecent advances, and ultra-structural and biochemical aspects on Matrix vesicles - mediated mineralization.

Bone mineral as a drug-seeking moiety and a waste dump.

Bone is a dynamic tissue with a quarter of the trabecular and a fifth of the cortical bone being replaced continuously each year in a complex process that continues throughout an individual’s lifetime. Bone has an important role in homeostasis of minerals with non-stoichiometric hydroxyapatite bone mineral forming the inorganic phase of bone. Due to its crystal structure and chemistry, hydroxyapatite (HA) and related apatites have a remarkable ability to bind molecules. This review article describes the accretion of trace elements in bone mineral giving a historical perspective. Implanted HA particles of synthetic origin have proved to be an efficient recruiting moiety for systemically circulating drugs which can locally biomodulate the material and lead to a therapeutic effect. Bone mineral and apatite however also act as a waste dump for trace elements and drugs, which significantly affects the environment and human health.Cite this article: Bone Joint Res 2020;9(10):709–718.

Protein adsorption and bioactivity of functionalized electrospun membranes for bone regeneration

ObjectivesTo evaluate the adsorption of bone related proteins and bioactivity of experimental functionalized (carboxylated or aminated) polymeric membranes for bone regeneration. MethodsPolymethylmethacrylate-based membranes functionalized with carboxyl or amino radicals were tested. Membranes were zinc loaded and the adsorption isotherms of zinc were studied. Human plasma proteins, bovine serum albumin, fibrinogen and fibronectin adsorption were measured with a spectrophotometer applying an acid determination protocol. Biomimetic calcium phosphate precipitation on polymeric membranes was also assessed after simulated body fluid immersion. Scanning electron microscopy and elemental analysis by means of an energy dispersive system were used for mineral deposits identification. A commercially available polytetrafluoroethylene membrane was used as control. ResultsBoth experimental membranes produced higher protein adsorption than the commercial control that does not adsorb proteins. Carboxylated membranes adsorbed significantly more albumin than the aminated ones, the opposite occurred with fibrinogen. With plasma and fibronectin proteins both type of membranes performed similarly. Only carboxylated membranes were bioactive and precipitated calcium and phosphate on their surfaces. ConclusionsThe polymethylmethacrylate zinc-loaded membranes functionalized with carboxyl groups performed as high adsorbable membranes for bone regeneration related proteins. They also served as templates for mineralization of hydroxyapatite. Clinical significanceProtein adsorption is the initial reaction after the implantation of a biomaterial into the body and will influence subsequent cell function. The adsorption of bone related proteins together with the observed biomimetic calcium deposition on the experimental carboxylated membranes could be associated with their ability to promote bone regeneration.

Calcium montmorillonite and montmorillonite with hydroxyapatite layer as fillers in dental composites with remineralizing potential

Calcium montmorillonite and montmorillonite with hydroxyapatite layer were used as fillers with remineralizing potential in composites for dental applications. These fillers were also modified using silane to improve their adhesion to the methacrylic resin. The effectiveness of fillers preparation has been confirmed by techniques such as X-ray Diffractometry, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, Transmission Electron Microscopy, Nitrogen adsorption/desorption measurements, and Fourier-Transform Infrared Spectroscopy. Calcium incorporation, mineralization of hydroxyapatite on the surface of montmorillonite, and particles silanization were conducted successfully. The usefulness of these composites as dental fillings was determined by examining the following properties: degree of conversion, depth of cure, flexural and compressive strength, mass stability, and remineralizing potential, understood as the ability to release calcium ions in the conditions simulating natural oral environment. All composites with calcium and hydroxyapatite forms of montmorillonite show the ability to release Ca2+; however, the remineralizing potential of calcium form of this mineral is significantly higher. Due to the ability to incorporate and release calcium ions, it is worth conducting further research on the application of this calcium-rich form of montmorillonite as an active filler in composites with potential dental applications.

A Novel Method of Self-Healing in Cementitious Materials by Using Polyacrylic Hydrogel

Cementitious materials are the most widely used in the construction. However, cementitious materials have defects such as low tensile strength which is easy to cause the formation of cracks. In recent years, with the research and application of smart materials, intelligent cementitious materials with self-sensing, self-diagnosis and self-healing functions have received extensive researcher’s attention. In this paper, a polyacrylic hydrogel that could be utilized for self-healing of cementitious materials was designed, and the three-dimensional network structure of the hydrogel controlled the release rate of encapsulated repair agent. The phosphate-incorporated hydrogel was filled into cement slurry to prepare self-healing cementitious materials. After the cement sample cracked and water penetrated into the crack, the phosphate was released from hydrogel. Phosphate reacted with the calcium in the pore solution to form hydroxyapatite type minerals which healed the crack. The self-healing cementitious material is in a position to heal cracks of 300 μm in width. After healing for 28 days at 20oC and 95% of RH, the compressive strength of precracked specimens could reach 85% of that of intact ones.

High efficient strategy for the production of hydroxyapatite/silk sericin nanocomposites

AbstractBACKGROUNDSericin (SS) induces nucleation of bone‐like hydroxyapatite (HAp) when used as an organic matrix. HAp/SS nanocomposites have been conventionally synthesized through precipitation in stirred tank reactors (STs). Despite its simplicity, this process is time consuming and presents difficulties in scale‐up. In our study, HAp/SS nanocomposites were successfully synthesized in a ST and in a meso‐oscillatory flow reactor (meso‐OFR), to compare the efficiency of both reactors and to study HAp mineralization using SS as a template.RESULTSThe production of stable HAp, indicated by pH stabilization, was achieved after 180 min in the ST and after 30 min in the meso‐OFR. X‐ray diffraction and Fourier transform infrared analyses showed that the particles obtained in both reactors are HAp/SS nanocomposites with low crystallinity. Scanning electron microscopy evidenced the formation of rod‐ and plate‐shaped nanoparticles and revealed that the presence of SS led to the production of larger particles. The latter observation was confirmed by laser diffraction. Additionally, increasing SS concentration resulted in the formation of more plate‐like particles.CONCLUSIONSPrecipitation is more efficient in the meso‐OFR, HAp/SS being obtained four times faster. The presence and concentration of SS led to differences in the size and morphology of the synthesized particles, suggesting a critical role of SS in the mineralization process. This work reports a new approach for the manufacture of high‐added‐value nanocomposites with similar characteristics to biological bone and the results of a study of the influence of SS as an organic component in HAp nucleation. Further, the use of this protein and technology leads to significant waste minimization. © 2020 Society of Chemical Industry (SCI)

68Ga]Ga-THP-Pam: A Bisphosphonate PET Tracer with Facile Radiolabeling and Broad Calcium Mineral Affinity.

Calcium minerals such as hydroxyapatite (HAp) can be detected noninvasively in vivo using nuclear imaging agents such as [18F]NaF (available from cyclotrons), for positron emission tomography (PET) and 99mTc-radiolabeled bisphosphonates (BP; available from 99mTc generators for single photon emission computed tomography (SPECT) or scintigraphy). These two types of imaging agents allow detection of bone metastases (based on the presence of HAp) and vascular calcification lesions (that contain HAp and other calcium minerals). With the aim of developing a cyclotron-independent PET radiotracer for these lesions, with broad calcium mineral affinity and simple one-step radiolabeling, we developed [68Ga]Ga-THP-Pam. Radiolabeling with 68Ga is achieved using a mild single-step kit (5 min, room temperature, pH 7) to high radiochemical yield and purity (>95%). NMR studies demonstrate that Ga binds via the THP chelator, leaving the BP free to bind to its biological target. [68Ga]Ga-THP-Pam shows high stability in human serum. The calcium mineral binding of [68Ga]Ga-THP-Pam was compared in vitro to two other 68Ga-BPs which have been successfully evaluated in humans, [68Ga]Ga-NO2APBP and [68Ga]Ga-BPAMD, as well as [18F]NaF. Interestingly, we found that all 68Ga-BPs have a high affinity for a broad range of calcium minerals implicated in vascular calcification disease, while [18F]NaF is selective for HAp. Using healthy young mice as a model of metabolically active growing calcium mineral in vivo, we compared the pharmacokinetics and biodistribution of [68Ga]Ga-THP-Pam with [18F]NaF as well as [68Ga]NO2APBP. These studies revealed that [68Ga]Ga-THP-Pam has high in vivo affinity for bone tissue (high bone/muscle and bone/blood ratios) and fast blood clearance (t1/2 < 10 min) comparable to both [68Ga]NO2APBP and [18F]NaF. Overall, [68Ga]Ga-THP-Pam shows high potential for clinical translation as a cyclotron-independent calcium mineral PET radiotracer, with simple and efficient radiochemistry that can be easily implemented in any radiopharmacy.

Saturation indices of aqueous mineral phases as proxies of seasonal dynamics of a transitional water ecosystem using a geochemical modeling approach

The geochemistry and saturation indices (SI) of carbonate and non-carbonate mineral phases under standard thermodynamic conditions in an aqueous environment are largely influenced by the dynamic physico-chemical parameters. Based on the known feedback mechanisms of environmental parameters on the rates of mineralisation, the changes in environmental parameters such as pH, dissolved ionic concentrations and salinity were modelled as a function of their spatial and temporal distributions (dry and wet seasons) in a transitional aquatic ecosystem in South India, Pulicat lagoon. The investigation revealed the strong seasonal influence of these parameters on the magnitude and values of the SIs signalling dissolution or mineralisation. Hydroxyapatite and Talc were found to have higher positive SIs. Co-precipitation of calcite and aragonite were evident and found to be constrained by high salinities. Among the carbonates, dolomites and magnesium-calcites showed high SIs compared to calcite and aragonite, indicating that magnesium ions were incorporated into the mineral phases possibly due to the availability of nucleation sites through heterotrophic reactions. The formation of apatite was strongly influenced by pH changes, corresponding to low calcite precipitation in the wet season. High SI of hydroxyapatite, talc and silicate minerals indicate the low bioavailability of dissolved phosphate and silicates in the water during both the seasons. Strong evidences of seasonal control of pH, salinity and Total Dissolved Solids on the dissolution and mineralisation characteristics further influence nutrient bioavailability over varied spatio-temporal scales. The present study supports the potential application of the saturation indices as proxies to understand the complex biogeochemical dynamics of transitional water ecosystems.

Calcium-Rich 13X Zeolite as a Filler with Remineralizing Potential for Dental Composites.

A zeolite with high ion-exchange potential was used as an active filler with remineralizing potential in composites that can be applied in restorative dentistry. Two calcium-rich forms of the 13X zeolite were obtained by sodium to calcium ion exchange and mineralization of a hydroxyapatite layer. These fillers were also silanized and mixed with methacrylic resins and photoinitiators to obtain composite materials. First, the effectiveness of the filler preparation and silanization was confirmed by X-ray diffractometry, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, nitrogen adsorption/desorption measurements, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The physicochemical characteristics of composites with silanized and nonsilanized forms of sodium- and calcium-rich 13X zeolite fillers were examined. The degree of conversion, depth of cure, flexural and compressive strength, mass stability, and remineralizing potential, understood as the ability to release calcium ions in the conditions simulating a natural oral environment, were determined. The effect of ion exchange, hydroxyapatite mineralization, and silanization of fillers on the final composites' properties was examined. Composites with calcium-rich fillers proved to show the ability to release Ca2+ during incubation in saline for 14 days at 36.6 °C showing therefore remineralizing potential with good values of other parameters.

Physiological silicon incorporation into bone mineral requires orthosilicic acid metabolism to SiO44.

Under physiological conditions, the predominant form of bioavailable silicon (Si) is orthosilicic acid (OSA). In this study, given Si's recognized positive effect on bone growth and integrity, we examined the chemical form and position of this natural Si source in the inorganic bone mineral hydroxyapatite (HA). X-ray diffraction (XRD) of rat tibia bone mineral showed that the mineral phase was similar to that of phase-pure HA. However, theoretical XRD patterns revealed that at the levels found in bone, the 'Si effect' would be virtually undetectable. Thus we used first principles density functional theory calculations to explore the energetic and geometric consequences of substituting OSA into a large HA model. Formation energy analysis revealed that OSA is not favourable as a neutral interstitial substitution but can be incorporated as a silicate ion substituting for a phosphate ion, suggesting that incorporation will only occur under specific conditions at the bone-remodelling interface and that dietary forms of Si will be metabolized to simpler chemical forms, specifically [Formula: see text]. Furthermore, we show that this substitution, at the low silicate concentrations found in the biological environment, is likely to be a driver of calcium phosphate crystallization from an amorphous to a fully mineralized state.

Nisin-loaded polydopamine/hydroxyapatite composites: Biomimetic synthesis, and in vitro bioactivity and antibacterial activity evaluations

Microbial contamination caused by bacterial adhesion and colonization onto the materials surfaces has long been a serious threat to human health. Thus, it is imperative to develop advanced antimicrobial materials for bio-applications. Here, a unique polydopamine/ hydroxyapatite/nisin (PDA/HAP/Nisin) composite with good bioactivities and enhanced antibacterial activities have been developed. The uniform PDA particles are first prepared via the dopamine self-polymerization in an alkaline water-ethanol mixed solvent. Due to the abundance surface catecholamine moieties, PDA particles can serve as the powerful templates for the in-situ mineralization of hydroxyapatite (HAP) in a simulated body fluid (SBF) solution, forming PDA/HAP composites. Transmission electron microscopy, scanning electron microscopy, transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction are used to investigate the morphology, surface composition, and crystalline structure of the PDA/HAP composites. These PDA/HAP composites are utilized as the reservoir for loading the antimicrobial peptide–nisin. Ultraviolet visible spectrophotometry analysis shows that PDA/HAP composites have exhibited a high loading capacity and a superior loading efficiency for nisin. The resulting PDA/HAP/Nisin composites are ideal antimicrobial biomaterials for bio-application because they exhibit not only a significant in vitro cytocompatibility to human embryonic kidney HEK293 T cells, but also the enhanced antibacterial activities against Staphylococcus aureus (Gram-positive bacteria). These advantageous properties of the PDA/HAP/Nisin composites allow them as the promising candidates for a broad range of bio-applications, e.g., drug delivery, implant engineering, and bio-scaffold.

Aumento tecidual estético com associação de biomaterial sintético e L-PRF

A reabilitação com implantes osseointegráveis é uma opção terapêutica consolidada na literatura e que apresenta alta taxa de sucesso e previsibilidade. Entretanto, as perdas dos elementos dentais levam a um colapso tecidual que muitas vezes inviabilizam a instalação dos implantes dentários, acarretando defeitos atróficos nos maxilares de variadas magnitudes. O objetivo deste caso clínico foi demonstrar a associação de um biomaterial sintético com a Fibrina Rica em Plaquetas (L-PRF) com a finalidade de aumento tecidual gengival em área estética. O paciente foi submetido a exames pré-operatórios, clínicos e radiográficos (tomografia computadorizada Cone Beam) da região da maxila com a confecção de protótipo e acompanhado por um ano e quatro meses. Foi realizado um enxerto onlay homógeno com bloco cortico-medular na região do defeito ósseo. Após sete meses de remodelação óssea, o paciente realizou nova tomografia computadorizada e foram inseridos os implantes dentários, concomitante a enxertia de biomaterial particulado de hidroxiapatita mineral inorgânica, que recebeu associação do L-PRF em fase líquida e posteriormente foi recoberto com a membrana de L-PRF. Após seis meses, nova tomografia computadorizada foi realizada para avaliação do procedimento anterior e seguiu-se com a reabertura e colocação de provisórios com o condicionamento do tecido gengival. Após 3 meses foi feita a moldagem personalizada e confeccionada a prótese fixa metalocerâmica na região dos elementos 12 ao 22. Podemos concluir com o caso clínico que a enxertia de biomaterial sintético associado ao L-PRF mostrou-se uma técnica eficaz no aumento de volume tecidual.

In situ mineralization of nano-hydroxyapatite on bifunctional cellulose nanofiber/polyvinyl alcohol/sodium alginate hydrogel using 3D printing

This paper reports the manufacturing by 3D printing of scaffolds for in-situ mineralization of hydroxyapatite using aqueous suspensions of alginate and polyvinyl alcohol (PVA)-grafted cellulose nanofibers (CNF). Bifunctional CNF with carboxyl and aldehyde moieties were prepared from bleached bagasse pulp and crosslinked with PVA. Aqueous hydrogels for 3D printing were prepared by directly mixing PVA-grafted CNF with sodium alginate, with and without the addition of phosphate ions. A calcium chloride solution was sprayed during the printing process in order to partially crosslink alginate and to increase the dimensional stability of the printed gel. At the end of the printing process, the prepared scaffolds were dipped into a CaCl2 solution to: i) complete alginate crosslinking and ii) promote hydroxyapatite nucleation and growth by reaction with phosphate ions. In order to better understand the mechanisms governing manufacturing of scaffolds by 3D printing, the rheological behavior of alginate/PVA-grafted CNF and the mechanical properties of unit filaments obtained by direct hydrogel extrusion were investigated. The final scaffolds were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). This study shows that 3D printed sodium alginate/PVA-grafted CNF hydrogels are promising scaffold materials for bone tissue engineering.

Antibiofilm Activity of a Trichoderma Metabolite against Xanthomonas campestris pv. campestris, Alone and in Association with a Phage.

Biofilm protects bacteria against the host’s immune system and adverse environmental conditions. Several studies highlight the efficacy of lytic phages in the prevention and eradication of bacterial biofilms. In this study, the lytic activity of Xccφ1 (Xanthomonas campestris pv. campestris-specific phage) was evaluated in combination with 6-pentyl-α-pyrone (a secondary metabolite produced by Trichoderma atroviride P1) and the mineral hydroxyapatite. Then, the antibiofilm activity of this interaction, called a φHA6PP complex, was investigated using confocal laser microscopy under static and dynamic conditions. Additionally, the mechanism used by the complex to modulate the genes (rpf, gumB, clp and manA) involved in the biofilm formation and stability was also studied. Our results demonstrated that Xccφ1, alone or in combination with 6PP and HA, interfered with the gene pathways involved in the formation of biofilm. This approach can be used as a model for other biofilm-producing bacteria.

Mineralization of calcium phosphate controlled by biomimetic self-assembled peptide monolayers via surface electrostatic potentials

The functions of acidic-rich domains in non-collagenous protein during biomineralization are thought to induce nucleation and control the growth of hydroxyapatite. The tripeptide Asp-Ser-Ser (DSS) repeats are the most common acidic-rich repeated unit in non-collagenous protein of dentin phosphoprotein, the functions of which have aroused extensive interests. In this study, biomimetic peptides (DSS)n (n = 2 or 3) were designed and fabricated into self-assembled monolayers (SAMs) on Au (111) surface as biomimetic organic templates to regulate hydroxyapatite (HAp) mineralization in 1.5 simulated body fluid (1.5 SBF) at 37 °C. The early mineralization processes and minerals deposited on the SAMs were characterized by X-ray diffraction, scanning electron microscope, and Fourier transform infrared spectroscopy analyses. The SAM-DSS9/DSS9G showed the highest capacity to induce HAp nucleation and growth, followed by SAM-DSS6/DSS6G, SAM-COOH, and SAM-OH. The SAM-(DSS)n had more negative zeta potentials than SAM-COOH surface, indicating that DSS repeats contributed to the biomineralization, which not only provided strong affinity with Ca2+ ions through direct electrostatic bonds, but more importantly influence surface electrostatic potentials of the assembled organic template for nucleation.

Bacteriophages Promote Metabolic Changes in Bacteria Biofilm.

Bacterial biofilm provides bacteria with resistance and protection against conventional antimicrobial agents and the host immune system. Bacteriophages are known to move across the biofilm to make it permeable to antimicrobials. Mineral hydroxyapatite (HA) can improve the lytic activity of bacteriophages, and, together with eicosanoic acid (C20:0), can destroy the biofilm structure. Here, we demonstrate the efficacy of the combined use of phage, HA and C20:0 against Xanthomonas campestris pv campestris (Xcc) biofilm. We used nuclear magnetic resonance (NMR)-based metabolomics to investigate the molecular determinants related to the lytic action, aiming at identifying the metabolic pathways dysregulated by phage treatment. Furthermore, we identified specific markers (amino acids, lactate and galactomannan) which are involved in the control of biofilm stability. Our data show that Xccφ1, alone or in combination with HA and C20:0, interferes with the metabolic pathways involved in biofilm formation. The approach described here might be extended to other biofilm-producing bacteria.

Modeling the Human Bone-Tumor Niche: Reducing and Replacing the Need for Animal Data.

ABSTRACTBone is the most common site for cancer metastasis. Understanding the interactions within the complex, heterogeneous bone–tumor microenvironment is essential for the development of new therapeutics. Various animal models of tumor‐induced bone disease are routinely used to provide valuable information on the relationship between cancer cells and the skeleton. However, new model systems exist that offer an alternative approach to the use of animals and might more accurately reveal the cellular interactions occurring within the human bone–tumor niche. This review highlights replacement models that mimic the bone microenvironment and where cancer metastases and tumor growth might be assessed alongside bone turnover. Such culture models include the use of calcified regions of animal tissue and scaffolds made from bone mineral hydroxyapatite, synthetic polymers that can be manipulated during manufacture to create structures resembling trabecular bone surfaces, gel composites that can be modified for stiffness and porosity to resemble conditions in the tumor–bone microenvironment. Possibly the most accurate model system involves the use of fresh human bone samples, which can be cultured ex vivo in the presence of human tumor cells and demonstrate similar cancer cell–bone cell interactions as described in vivo. In addition, the use of mathematical modeling and computational biology approaches provide an alternative to preliminary animal testing. The use of such models offers the capacity to mimic significant elements of the human bone–tumor environment, and complement, refine, or replace the use of preclinical models. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.