Calcium Phosphate Layer Research Articles

Acidity-Actuated Polymer/Calcium Phosphate Hybrid Nanomotor (PCaPmotor) for Penetrating Drug Delivery and Synergistic Anticancer Immunotherapy.

Tumor acidity-driven nanomotors may offer robust propulsion for tumor-specific penetrating drug delivery. Herein, an acidity-actuated poly(amino acid) calcium phosphate (CaP) hybrid nanomotor (PCaPmotor) was designed, using a mPEG-PAsp-PPhe@THZ531 micelle (Poly@THZ) for CaP mineralization accompanied by αPD-L1 antibody encapsulation. Dissolution of the CaP layer in an acidic tumor environment gave off heat energy to propel the nanomotor to augment the cellular uptake and penetration into deeply seated cancer cells while facilitating αPD-L1 release. THZ531 delivered by the PCaPmotor inhibited CDK12 and its down-streamed phosphorylation of RNAP-II to increase the cancer immunogenicity events such as the DNA damage, cell apoptosis, immunogenic cell death, lysosomal function disturbance, and MHC-I upregulation. THZ531 and αPD-L1 cosupplied by PCaPmotor significantly increased the frequency of DCs maturation and intratumoral infiltration of CTLs, but the two free drugs did not. Consequently, the PCaP@THZ/αPD-L1 nanomotor resulted in synergistic anticancer immunotherapy in mice. This acid-actuated PCaPmotor represented a new paradigm for penetrating drug delivery.

Magnetically responsive micro-clustered calcium phosphate-reinforced cell-laden microbead sodium alginate hydrogel for accelerated osteogenic tissue regeneration

The rising prevalence of bone injuries has increased the demand for minimally invasive treatments. Microbead hydrogels, renowned for cell encapsulation, provide a versatile substrate for bone tissue regeneration. They deliver bioactive agents, support cell growth, and promote osteogenesis, aiding bone repair and regeneration. In this study, we synthesized superparamagnetic iron oxide nanoparticles (Sp) coated with a calcium phosphate layer (m-Sp), achieving a distinctive flower-like micro-cluster morphology. Subsequently, sodium alginate (SA) microbead hydrogels containing m-Sp (McSa@m-Sp) were fabricated using a dropping gelation strategy. McSa@m-Sp is magnetically targetable, enhance cross-linking, control degradation rates, and provide strong antibacterial activity. Encapsulation studies with MC3T3-E1 cells revealed enhanced viability and proliferation. These studies also indicated significantly elevated alkaline phosphatase (ALP) activity and mineralization in MC3T3-E1 cells, as confirmed by Alizarin Red S (ARS) and Von Kossa staining, along with increased collagen production within the McSa@m-Sp microbead hydrogels. Immunocytochemistry (ICC) and gene expression studies supported the osteoinductive potential of McSa@m-Sp, showing increased expression of osteogenic markers including RUNX-2, collagen-I, osteopontin, and osteocalcin. Thus, McSa@m-Sp microbead hydrogels offer a promising strategy for multifunctional scaffolds in bone tissue engineering.

Biomimetic Calcium Phosphate Nanoparticles: Biomineralization Models and Precursors for Composite Materials.

The formation of calcium phosphate under the control of water-soluble polymers is important for understanding bone growth in living organisms. These experiments also have spin-offs in the creation of composite materials, including for regenerative medicine applications. The formation of calcium phosphate (hydroxyapatite) from calcium chloride and diammonium phosphate was studied in the presence of polymers containing carboxyl, amine, and imidazole groups. Depending on the polymer composition, solid products and stable dispersions of positively or negatively charged nanoparticles were obtained. Oppositely charged nanoparticles can interact with each other to form a macroporous composite material, which holds promise as a filler for bone defects. The formation of a calcium phosphate layer around a living cell (dinoflagellate Gymnodinium corollarium A. M. Sundström, Kremp et Daugbjerg) using positive composite nanoparticles is a one-step approach to cell mineralization.

Alendronate as Bioactive Coating on Titanium Surfaces: An Investigation of CaP-Alendronate Interactions.

The surface modification of dental implants plays an important role in establishing a successful interaction of the implant with the surrounding tissue, as the bioactivity and osseointegration properties are strongly dependent on the physicochemical properties of the implant surface. A surface coating with bioactive molecules that stimulate the formation of a mineral calcium phosphate (CaP) layer has a positive effect on the bone bonding process, as biomineralization is crucial for improving the osseointegration process and rapid bone ingrowth. In this work, the spontaneous deposition of calcium phosphate on the titanium surface covered with chemically stable and covalently bound alendronate molecules was investigated using an integrated experimental and theoretical approach. The initial nucleation of CaP was investigated using quantum chemical calculations at the density functional theory (DFT) level. Negative Gibbs free energies show a spontaneous nucleation of CaP on the biomolecule-covered titanium oxide surface. The deposition of calcium and phosphate ions on the alendronate-modified titanium oxide surface is governed by Ca2+-phosphonate (-PO3H) interactions and supported by hydrogen bonding between the phosphate group of CaP and the amino group of the alendronate molecule. The morphological and structural properties of CaP deposit were investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and attenuated total reflectance Fourier transform infrared spectroscopy. This integrated experimental-theoretical study highlights the spontaneous formation of CaP on the alendronate-coated titanium surface, confirming the bioactivity ability of the alendronate coating. The results provide valuable guidance for the promising forthcoming advancements in the development of biomaterials and surface modification of dental implants.

Effects of Tb3+ on properties of luminescent calcium sulfate cement

Calcium sulfate powder materials containing terbium ions at 0, 1.0, or 2.0 mol.% were obtained. They are characterized by the presence of a CaSO4 × 0.5H2O phase, while Tb3+ is incorporated into the lattice at ≤1.0 mol.%. Specific surface area enlarged from 2.1 to 22.5 m2/g as crystallite size decreased from 68 to 31 nm. Thermal analysis showed that terbium slightly raises the temperature of CaSO4 × 2H2O-to-CaSO4 transition. Studies of solubility in SBF solution showed the presence of a calcium phosphate layer in terbium-containing cements on the 7th day. Luminescent properties were studied by excitation at 266 nm and 489 nm corresponding to absorption bands of the host and Tb3+ (7F6 - 5D4 absorption band). The recorded emission peaks of the materials showed that the luminescence of the samples was green, with the luminescence intensity increasing when Tb3+ was introduced. The developed materials can find applications in medicine as bioimplants with a possibility of noninvasive visualization of the bone restoration process.

Polyhydroxybutyrate-based osteoinductive mineralized electrospun structures that mimic components and tissue interfaces of the osteon for bone tissue engineering.

Scaffolds for bone tissue engineering should enable regeneration of bone tissues with its native hierarchically organized ECM and multiple tissue interfaces. To achieve this, inspired by the structure and properties of bone osteon, we fabricated polyhydroxybutyrate-based mineralized electrospun fibrous scaffolds. After studying multiple polyhydroxybutyrate (PHB)-based fibers, we chose 7%PHB/1%Gelatin fibers (PG) to fabricate mineralized fibers that mimic mineralized collagen fibers in bone. The mineralized PG (mPG) surface had a rough, hydrophilic layer of low crystalline calcium phosphate which was biocompatible to BMSCs, induced their proliferation and was osteoinductive. Subsequently, by modulating the electrospinning process, we fabricated mPG-based novel higher order fibrous scaffolds that mimic the macroscale geometries of osteons of bone ECM. Inspired by the aligned collagen fibers in bone lamellae, we fabricated mPG scaffolds with aligned fibers that could direct anisotropic elongation of mBMSCs. Further, we fabricated electrospun mPG-based osteoinductive tubular constructs which can mimic cylindrical bone components like osteons or lamellae or be used as long bone analogues based on their dimensions. Finally, to regenerate tissue interfaces in bone, we introduced a novel bi-layered scaffold-based approach. An electrospun bi-layered tubular construct that had PG in the outer layer and 7%PHB/0.5%Polypyrrole fibers (PPy) in the inner layer was fabricated. The bi-layered tubular construct underwent preferential surface mineralization only on its outer layer. This outer mineralized layer supported osteogenesis while the inner PPy layer could support neural cell growth. Thus, the bi-layered tubular construct may be used to regenerate haversian canal in the osteons which hosts nerve fibers. Overall, the study introduced novel techniques to fabricate biomimetic structures that can regenerate components of bone osteon and its multiple tissue interfaces. The study lays foundation for the fabrication of a modular scaffold that can regenerate bone with its hierarchical structure and complex tissue interfaces.

Fabrication of 3D porous polyurethane-graphene oxide scaffolds by a sequential two-step processing for non-load bearing bone defects

Bone defects as a common orthopedic disease lead to severe pains over a long period. Scaffolds are novel approaches in tissue engineering to treat bone problems and deal with their challenges. Here, 3D porous polyurethane (PU) scaffolds containing graphene oxide (GO) with different percentages (0, 0.1, 0.3, and 0.5 wt%) were developed through a combination of freeze-drying and salt etching techniques for bone tissue engineering applications. The morphologies of scaffolds, physicochemical properties, the degree of crystallinity, and hydrophilicity were evaluated by SEM, FTIR, XRD, and water contact angle assay, respectively. The porosity, degradation behavior, compressive strength, and elastic modulus of 3D porous scaffolds were also determined. To assess the scaffold bioactivity, the morphology of the deposited calcium phosphate layer on the scaffold with macro-structure was evaluated by SEM images. The viability and adhesion of MG63 osteoblast-like cells cultured on the fabricated scaffolds were examined by MTT assay and SEM images, respectively. The results show that adding GO particles not only had no effect on the interconnectivity and porosity of 3D porous macroscopic structures of neat PU but also smaller and more uniformed microscopically pores were obtained. The crystallinity, water contact angle, and weight loss of scaffolds increased as the higher GO concentrations were employed. Followed by increasing GO contents from 0 to 0.5 wt%, the compressive strength and Young’s modulus were increased by 232% and 245%, respectively. The bioactivity of scaffolds was fostered as GO concentration increased. Although, the MTT assay proved the biocompatibility of PU scaffolds containing 0.1 and 0.3 wt% GO, the samples loaded with 0.5 GO had a negative impact on the viability of MG63 cell lines. In conclusion, the present study demonstrates a high potential of PU scaffolds loaded with 0.1 and 0.3 wt% GO particles in bone tissue engineering applications.

Mesoporous bioactive scaffolds based on the 14.6Li2O⋅8.6ZrO2⋅67.3SiO2⋅9.5Al2O3 glass-ceramic as drug delivery for bone regeneration

Bioactive scaffolds based on the 14.6Li2O⋅8.6ZrO2⋅67.3SiO2⋅9.5Al2O3 glass-ceramic for use in drug delivery is presented. Powders of the parent glass (212 mm > particle size >38 mm) were heat-treated at 725 °C for 3 h for surface crystallization. They were subjected to a chemical attack with 6 vol% of hydrofluoric acid for 40 s for partial dissolution of the residual glass, and washed with deionised water and calcium carbonate. Structural and microstructural analyses were performed to identify the formed crystalline phases and porosity. Mesopores with 2.05 nm-radius were detected. The immersion method was used to insert alendronate sodium into the scaffolds. The drug delivering capability was evaluated by infrared spectroscopy and thermogravimetric analysis (TG). The FTIR spectra showed the typical functional groups existing in the alendronate sodium, confirming their impregnation into the scaffold's pores. Moreover, the TG thermograms showed loss weights of ∼2% indicating the effective inoculation of the drug into the scaffold. The bioactivity of the material was evaluated through calcium phosphate layer formation after incubation in a simulated body fluid for up to 28 days (37 ± 1 °C) and then analysed by infrared spectroscopy (FTIR). Calcium phosphates were identified after 24 h of immersion indicating the bioactivity of the glass-ceramic. The cytotoxicity and hemocompatibility tests showed that the LZSA glass-ceramic scaffold is not considered toxic to the human body at concentrations below 40 μg/mL and does not show hemolytic effects at all tested concentrations. Thus, the obtained microstructure renders the material promising for use as a drug delivery agent for bone regeneration.

Correlating immediate vapour reactivity with dentin remineralization and tubule occlusion capacity of a bioactive sol-gel borate glass

The use of bioactive glass as a mineralization agent in treating dentin hypersensitivity has been established for almost two decades where the melt-quench-derived silicate glass, 45S5, may be regarded as the gold standard formulation. Compared to silicate glasses, borate glasses are less chemically durable and have the potential to mineralize (i.e., convert to apatite) more rapidly. This study compared the apatite forming capacity of a sol-gel-derived calcium-borate glass, 40CaO–60B2O3 (SGB60), to that of 45S5, on demineralized dentin discs and its ability to occlude tubules on non-demineralized dentin discs, in vitro. Moreover, it investigated the vapour sorption reactivity of the glasses to explore the potential correlation between their immediate aqueous interactions and bioactivity in remineralization solution. Compared to 45S5, SGB60 demonstrated more rapid calcium-phosphate layer formation on demineralized dentin surfaces. On the other hand, after 24 h immersion in remineralization solution, the 45S5-induced calcium-phosphate layer occlusion of tubules in non-demineralized dentin surfaces appeared to be qualitatively greater than that induced by SGB60. Moreover, vapour sorption analysis under either air or nitrogen gas, demonstrated that the reactivity of 45S5 with vapour varied under the different purge gasses, with significant carbonate formation under air. In contrast, SGB60 showed a more rapid rate of initial weight increase with vapour under both purge gasses, and this vapour reactivity may be correlated to its more rapid calcium-phosphate layer formation on demineralized dentin surfaces when immersed in remineralization solution.

Copper-doped magnesium phosphate nanopowders for critical size calvarial bone defect intervention.

Calvarial defects of bone present difficult clinical situations, and their restoration using biocompatible materials requires special treatments that enable bone regeneration. Magnesium phosphate (MgP) is known as an osteoinductive biomaterial because it contains Mg2+ ions and P ions that enhance the activity of osteoplast cells and help in bone regeneration. In this study, MgP and CuO-doped MgP were fabricated and characterized for their physicomechanical properties, particle size, morphology, surface area, antibacterial test, and in vitro bioactivity evaluation using the following techniques: X-rays diffraction, Fourier-transformer infrared, TEM, and Brunauer, Emmett and Teller (BET) surface area, X-rays photoelectron spectroscopy (XPS), and Scanning electron microscopy (SEM). Furthermore, these nanopowders were implanted in adult inbred male Wistar rats and studied after two periods (28 and 56 days). The results demonstrated that the obtained semiamorphous powders are in nanoscale (≤ 50 nm). XPS analysis ensured the preparation of MgP as mono MgP and CuO were incorporated in the structure as Cu2+ . The bioactivity was supported by the observation of calcium phosphate layer on the nanopowders' surface. The in vivo study demonstrated success of MgP nanopowders especially those doped with CuO in restoration of calvarial defect bone. Therefore, fabricated biomaterials are of great potential in restoration of bone calvarial defects.

Bioactive glass enhanced alginate / carboxymethyl cellulose funcional dressings Li2O–ZrO2–SiO2

The healing of skin injuries is crucial for the human body, but the presence of harmful bacteria can be detrimental. Conventional dressings provide protection but do not promote active healing. In contrast, functional dressings can enhance regeneration by regulating moisture, facilitating gas exchange, preventing infection, and may even contain therapeutic compounds. Li2O–ZrO2–SiO2 (LZS) bioactive glasses possess antibacterial and regenerative properties but have not yet been explored in wound dressings. Therefore, this work aims to evaluate the potential of LZS glass to be used as an antibacterial biomaterial to obtain functional dressings. The antibacterial activity against Staphylococcus aureus and Escherichia coli was considered for this purpose. In-vitro biological studies were assessed by MTT (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide), and DNA damage. Alginate and carboxymethyl cellulose (CMC) dressings were prepared with the addition of LZS in a minimum bactericidal concentration (MBC). The dressings' bioactivity was assessed by exposing them to a simulated body fluid (SBF) and analyzing their structure and microstructure. The glass efficiently inhibited the tested microorganisms, with an MBC of 100 mg/mL. LZS glasses exhibited no cytotoxicity. The bioactive glass-incorporated dressings demonstrated appropriate thickness and fluid absorption capacity for application in wound treatment. The deposition of a calcium phosphate layer on the surface of the dressings proved its bioactivity. The optimized design exhibited a tensile strength of 0.28 MPa and an elongation of 15.63 %. The functional dressings obtained have potential for applications in tissue repair where bacterial proliferation is a concern.

Erratum: Deposition of insoluble calcium phosphate layers by combining finely dispersed calcium hydroxide sols with soluble phosphates

The proceedings editor, while fixing formatting issues, inadvertently introduced inaccuracies within the chemical formulas and the authors names. A corrected version of the article has been published.

Deposition of insoluble calcium phosphate layers by combining finely dispersed calcium hydroxide sols with soluble phosphates

Carbonate containing materials are subject to severe weathering. Traditional formulations of stone strengtheners have low compatibility with the original material and further they contain VOCs (volatile organic compounds), which endanger human health and the environment. This study explores the high potential of novel treatments based on water-soluble phosphates used as an agent to react with calcium carbonate (CaCO3) to form an insoluble film of calcium phosphate in the pore space of the treated material. Pretreatments with nanolime suspensions ensure greater availability of calcium ions and reduce the consumption of the original material in the reactions. An alkaline environment is required to promote the conversion of the CaCO3 components to hydroxyapatite-like compounds. Based on experiments in aqueous solutions, different sources of phosphate ions could be examined and compared for the development of effective treatments to apply on different test specimens. To implement the treatments, barium phosphate solutions were investigated. Important aspects of this research are the use of green solvents and the search of components that avoid the formation of byproducts, to increase the efficiency of the chemical reactions and reduce possible negative effects on the operator, the environment and the very same built heritage material. The developed treatments are a valuable alternative to the traditional methods, as it follows an improvement in the material properties without affecting the moisture transport within it and allows the evenly reaction of the strengthened material to external physical and mechanical stresses without creating internal tension between the grains.

Self-adjuvant Astragalus polysaccharide-based nanovaccines for enhanced tumor immunotherapy: a novel delivery system candidate for tumor vaccines.

The study of tumor nanovaccines (NVs) has gained interest because they specifically recognize and eliminate tumor cells. However, the poor recognition and internalization by dendritic cells (DCs) and insufficient immunogenicity restricted the vaccine efficacy. Herein, we extracted two molecular-weight Astragalus polysaccharides (APS, 12.19 kD; APSHMw, 135.67 kD) from Radix Astragali and made them self-assemble with OVA257-264 directly forming OVA/APS integrated nanocomplexes through the microfluidic method. The nanocomplexes were wrapped with a sheddable calcium phosphate layer to improve stability. APS in the formed nanocomplexes served as drug carriers and immune adjuvants for potent tumor immunotherapy. The optimal APS-NVs were approximately 160 nm with uniform size distribution and could remain stable in physiological saline solution. The FITC-OVA in APS-NVs could be effectively taken up by DCs, and APS-NVs could stimulate the maturation of DCs, improving the antigen cross-presentation efficiency in vitro. The possible mechanism was that APS can induce DC activation via multiple receptors such as dectin-1 and Toll-like receptors 2 and 4. Enhanced accumulation of APS-NVs both in draining and distal lymph nodes were observed following s.c. injection. Smaller APS-NVs could easily access the lymph nodes. Furthermore, APS-NVs could markedly promote antigen delivery efficiency to DCs and activate cytotoxic T cells. In addition, APS-NVs achieve a better antitumor effect in established B16-OVA melanoma tumors compared with the OVA+Alum treatment group. The antitumor mechanism correlated with the increase in cytotoxic T cells in the tumor region. Subsequently, the poor tumor inhibitory effect of APS-NVs on the nude mouse model of melanoma also confirmed the participation of antitumor adaptive immune response induced by NVs. Therefore, this study developed a promising APS-based tumor NV that is an efficient tumor immunotherapy without systemic side effects.

Gadolinium-Based Contrast Agents and Free Gadolinium Inhibit Differentiation and Activity of Bone Cell Lineages.

Administration of gadolinium-based contrast agents (GBCA) in magnetic resonance imaging results in the long-term retention of gadolinium (Gd) in tissues and organs, including the bone, and may affect their function and metabolism. This study aims to investigate the effects of Gd and GBCA on the proliferation/survival, differentiation, and function of bone cell lineages. Primary murine osteoblasts (OB) and osteoclast progenitor cells (OPC) isolated from C57BL/6J mice were used to test the effects of Gd 3+ (12.5-100 μM) and GBCA (100-2000 μM). Cultures were supplemented with the nonionic linear Gd-DTPA-BMA (gadodiamide), ionic linear Gd-DTPA (gadopentetic acid), and macrocyclic Gd-DOTA (gadoteric acid). Cell viability and differentiation were analyzed on days 4-6 of the culture. To assess the resorptive activity of osteoclasts, the cells were grown in OPC cultures and were seeded onto layers of amorphous calcium phosphate with incorporated Gd. Gd 3+ did not affect OB viability, but differentiation was reduced dose-dependently up to 72.4% ± 6.2%-73.0% ± 13.2% (average ± SD) at 100 μM Gd 3+ on days 4-6 of culture as compared with unexposed controls ( P < 0.001). Exposure to GBCA had minor effects on OB viability with a dose-dependent reduction up to 23.3% ± 10.2% for Gd-DTPA-BMA at 2000 μM on day 5 ( P < 0.001). In contrast, all 3 GBCA caused a dose-dependent reduction of differentiation up to 88.3% ± 5.2% for Gd-DTPA-BMA, 49.8% ± 16.0% for Gd-DTPA, and 23.1% ± 8.7% for Gd-DOTA at 2000 μM on day 5 ( P < 0.001). In cultures of OPC, cell viability was not affected by Gd 3+ , whereas differentiation was decreased by 45.3% ± 9.8%-48.5% ± 15.8% at 100 μM Gd 3+ on days 4-6 ( P < 0.05). Exposure of OPC to GBCA resulted in a dose-dependent increase in cell viability of up to 34.1% ± 11.4% at 2000 μM on day 5 of culture ( P < 0.001). However, differentiation of OPC cultures was reduced on day 5 by 24.2% ± 9.4% for Gd-DTPA-BMA, 47.1% ± 14.0% for Gd-DTPA, and 38.2% ± 10.0% for Gd-DOTA ( P < 0.001). The dissolution of amorphous calcium phosphate by mature osteoclasts was reduced by 36.3% ± 5.3% upon incorporation of 4.3% Gd/Ca wt/wt ( P < 0.001). Gadolinium and GBCA inhibit differentiation and activity of bone cell lineages in vitro. Thus, Gd retention in bone tissue could potentially impair the physiological regulation of bone turnover on a cellular level, leading to pathological changes in bone metabolism.

Developing a deposited calcium-phosphate layer on zirconia surface by chemical grafting of L-Serine molecules

Due to the proper mechanical properties and desirable aesthetic properties of zirconia, it is considered as a good candidate for replacement of metallic implants. In this study, zirconia was functionalized by l-serine amino acid to provide surface COOH/OH groups for calcium-phosphate formation (CPF) of hydroxyapatite and chemical bonding to bone tissue following implantation. Magnesia-partially stabilized zirconia (Mg-PSZ) discs were prepared and hydroxylated using hydrothermal process at 120 °C for different times to provide reactive hydroxyl groups. Thereafter, the discs were immersed in 0.01 mg/mL aqueous l-Serine solution at temperatures between 40 °C and 80 °C for different times and pH to graft l-Serine molecules on the zirconia surface. Afterward, the specimens were incubated in simulated body fluid (SBF) for 7 and 21 days. The results indicated that the grafting of l-Serine on the zirconia surface, at 80 °C in neutral pH, created negative charges. The hydroxyl apatite, on the surfaces grafted with l-Serine, started to nucleate and grow almost simultaneously after 7 days of exposure to alkaline pH. The soaking was continued for 21 days to form more uniform mineral apatite with developed surface wettability (i.e., contact angle of 18.3° ± 1.3). Herein, the absorption of calcium and phosphate ions caused the formation of hydroxyapatite nucleation and growth in 21 days.

Dissolution of Bioactive Glass S53P4 in Continuous Flows of Tris Buffer and Lactic Acid

In vitro dynamic dissolution of bioactive glass S53P4 particles was studied in a cascade of three reactors. Tris buffer (pH 7.40) and lactic acid (pH 2.00) with flow rates of 0.2 and 0.04 ml/min were fed through the reactors for 24 h. The increased ion concentrations in Tris inflows to the second and third reactors decreased the dissolution of the particles. However, the normalised surface-specific mass loss rate decreased from the first to the third reactor and with decreasing flow rate. No distinct differences were observed in the reaction layers on the particles in the three consecutive reactors. This implied that the ions released in the previous reactors contributed to the reaction layers formed in the following reactors. Highly incongruent dissolution with similar dissolution rates of sodium, calcium, and phosphorus occurred with the two flow rates in lactic acid. Although a thick silica-rich layer formed on the particles, the low pH prevented calcium phosphate layer precipitation. The results imply that S53P4 particles in an implant react at different rates depending on their location but form similar reaction layer morphologies independent of their location in physiological solutions (pH 7.4). On the other hand, S53P4 particles exposed to acidic solutions with a pH < 5 likely dissolve incongruently, leaving a slowly dissolving Si-rich layer. In such an environment, the dissolution rates of Na, Ca, and P are independent of the location of the S53P4 particle in the implant. Thus, the pH and fluid flow are critical factors for the dissolution of S53P4 bioactive glass particles.

KCl, KNO3, and Annealing for Modifying the Morphology and Properties of Ca-P Layers on Mg Alloy

The aim of the work was to obtain a dense and uniform calcium phosphate (Ca-P) coating on the studied magnesium (Mg) alloy using simple methods that are easy to implement on an industrial scale. In this work, Ca-P layers were prepared on the surface of a Mg alloy. The simple wet chemical method based on immersion in an aqueous solution was used to prepare the Ca-P layer on the Mg alloy (AM60) surface. The effect of chemical modification by potassium chloride (KCl) and potassium nitrate (KNO3), as well as annealing on the morphology of the phosphate layers on the AM60 alloy, was determined, as well as the impact of this layer on the evolution of hydrogen in Ringer’s solution. The addition of KCl and KNO3 to the phosphating bath caused coagulation and agglomeration of the elements of the Ca-P coating. Consequently, the flake structure of the Ca-P coating changes into two types of structures: chrysanthemum and rhombohedral. Annealing at 150 °C for 3 h allows one to obtain a dense and uniform Ca-P coating on the studied Mg alloy. The Ca-P coating obtained by annealing at 150 °C can greatly decrease the hydrogen evolution rate of AM60 alloy in Ringer’s solution to 0.02 ml/cm2/day, which is similar to the safe amount of hydrogen for the human body (H2 ≈ 0.01 ml/cm2/day).

Spectral Analysis of Strontium-Doped Calcium Phosphate/Chitosan Composite Films.

Strontium-doped calcium phosphate/chitosan films were synthetized on silicon substrates using the radio-frequency magnetron sputtering technique and the matrix-assisted pulsed laser evaporation technique. The deposition conditions associated with the radio-frequency magnetron sputtering discharge, in particular, include the high temperature at the substrate, which promotes the formation of strontium-doped tetra calcium phosphate layers. The physical and chemical processes associated with the deposition of chitosan on strontium-doped calcium phosphate layers were investigated using Fourier Transform Infrared Spectroscopy, Energy Dispersive X-ray Spectroscopy, and Scanning Electron Microscopy. Mass spectrometry coupled with laser induced ablation of the composite films proved to be a useful tool in the detection of the molecular ions characteristic to chitosan chemical structure.

Fabrication of a Fish-Bone-Inspired Inorganic-Organic Composite Membrane.

Biological materials have properties like great strength and flexibility that are not present in synthetic materials. Using the ribs of crucian carp as a reference, we investigated the mechanisms behind the high mechanical properties of this rib bone, and found highly oriented layers of calcium phosphate (CaP) and collagen fibers. To fabricate a fish-rib-bone-mimicking membrane with similar structure and mechanical properties, this study involves (1) the rapid synthesis of plate-like CaP crystals, (2) the layering of CaP-gelatin hydrogels by gradual drying, and (3) controlling the shape of composite membranes using porous gypsum molds. Finally, as a result of optimizing the compositional ratio of CaP filler and gelatin hydrogel, a CaP filler content of 40% provided the optimal mechanical properties of toughness and stiffness similar to fish bone. Due to the rigidity, flexibility, and ease of shape control of the composite membrane materials, this membrane could be applied as a guided bone regeneration (GBR) membrane.