X-ray photoelectron and ion scattering spectroscopic surface analyses of amorphous and crystalline calcium phosphate nanoparticles with different chemical histories

Fabrication of alginate composite hydrogel encapsulated retinoic acid and nano Se doped biphasic CaP to augment in situ mineralization and osteoimmunomodulation for bone regeneration

BACKGROUND

Bone tissue engineering endows alternates to support bone defects/injuries that are circumscribed to undergo orchestrated process of remodeling on its own. In this regard, hydrogels have emerged as a promising platform that can confront irregular defects and encourage in situ bone repair.

METHODS

In this study, we aimed to develop a new approach for bone tissue regeneration by developing an alginate based composite hydrogel incorporating selenium doped biphasic calcium phosphate nanoparticles, and retinoic acid. The fabricated hydrogel was physiochemically evaluated for morphological, bonding, and mechanical behavior. Additionally, the biological response of the fabricated hydrogel was evaluated on MC3T3-E1 pre-osteoblast cells.

RESULTS

The developed composite hydrogel confers excellent biocompatibility, and osteoconductivity owing to the presence of alginate, and biphasic calcium phosphate, while selenium presents pro osteogenic, antioxidative, and immunomodulatory properties. The hydrogels exhibited highly porous microstructure, superior mechanical attributes, with enhanced calcification, and biomineralization abilities in vitro.

SIGNIFICANCE

By combining the osteoconductive properties of biphasic calcium phosphate with multifaceted benefits of selenium and retinoic acid, the fabricated composite hydrogel offers a potential transformation in the landscape of bone defect treatment. This strategy could direct a versatile and effective approach to tackle complex bone injuries/defects and present potential for clinical translation.

Monitoring Photo-Fenton and Photo-Electro-Fenton process of contaminants emerging concern by a gas diffusion electrode using Ca10-xFex-yWy(PO4)6(OH)2 nanoparticles as heterogeneous catalyst

The catalytic performance of modified hydroxyapatite nanoparticles, Ca10-xFex-yWy(PO4)6(OH)2, was applied for the degradation of methylene blue (MB), fast green FCF (FG) and norfloxacin (NOR). XPS analysis pointed to the successful partial replacement of Ca by Fe. Under photo-electro-Fenton process, the catalyst Ca4FeII1·92W0·08FeIII4(PO4)6(OH)2 was combined with UVC radiation and electrogenerated H2O2 in a Printex L6 carbon-based gas diffusion electrode. The application of only 10 mA cm-2 resulted in 100% discoloration of MB and FG dyes in 50 min of treatment at pH 2.5, 7.0 and 9.0. The proposed treatment mechanism yielded maximum TOC removal of ∼80% and high mineralization current efficiency of ∼64%. Complete degradation of NOR was obtained in 40 min, and high mineralization of ∼86% was recorded after 240 min of treatment. Responses obtained from LC-ESI-MS/MS are in line with the theoretical Fukui indices and the ECOSAR data. The study enabled us to predict the main degradation route and the acute and chronic toxicity of the by-products formed during the contaminants degradation.

Biological and Physicochemical Analysis of Sr-Doped Hydroxyapatite/Chitosan Composite Layers

In this work results are presented on the evaluation of HAp, HApSr, HAp_CS, and HApSr_CS layers deposited on Ti substrates regarding L929 cell viability and cytotoxicity as well as antimicrobial activity against Staphylococcus aureus, in connection with their physicochemical properties. The HAp and HApSr layers generated by radio-frequency magnetron sputtering technique were further covered with chitosan by a matrix-assisted pulsed laser evaporation technique. During the plasma depositions, the Ti substrates were heated externally by a home-made oven above 100 °C. The HApSr_CS layers generated on the unpolished Ti substrates at 100 °C and 400 °C showed the highest biocompatibility properties and antimicrobial activity against Staphylococcus aureus. The morphology of the layer surfaces, revealed by scanning electron microscopy, is dependent on substrate temperature and substrate surface roughness. The optically polished surfaces of Ti substrates revealed grain-like and microchannel structure morphologies of the layers deposited at 25 °C substrate temperature and 400 °C, respectively. Chitosan has no major influence on HAp and HApSr layer surface morphologies. X-ray photoelectron spectroscopy indicated the presence of Ca 2p3/2 peak characteristic of the HAp structure even in the case of the HApSr_CS samples generated at a 400 °C substrate temperature. Fourier transform infrared spectroscopy investigations showed shifts in the wavenumber positions of the P-O absorption bands as a function of Sr or chitosan presence in the HAp layers generated at 25, 100, and 400 °C substrate temperatures.

A magnetic calcium phosphate for selective capture of multi-phosphopeptides

The specific enrichment of multi-phosphopeptides in the presence of non-phosphopeptides and mono-phosphopeptides was still a challenge for phosphoproteomics research. Most of these enrichment materials relied on Zn, Ti, Sn, and other rare precious metals as the bonding center to enrich multi-phosphopeptides while ignoring the use of common metal elements. The addition of rare metals increased the cost of the experiment, which was not conducive to their large-scale application in biomedical proteomics laboratories. In addition, multiple high-speed centrifugation steps also resulted in the loss of low-abundance multi-phosphopeptides in the treatment procedure of biological samples. This study proposed the use of calcium, a common element, as the central bonding agent for synthesizing magnetic calcium phosphate materials (designated as CaP-Fe3O4). These materials aim to capture multi-phosphopeptides and identifying phosphorylation sites. The current results demonstrate that CaP-Fe3O4 exhibited excellent selection specificity, high sensitivity, and stability in the enrichment of multi-phosphopeptides and the identification of phosphorylation sites. Additionally, the introduction of magnetic separation not only reduced the time required for multi-phosphopeptides enrichment but also prevented the loss of these peptides during high-speed centrifugation. These findings contribute to the widespread application and advancement of phosphoproteomics research.

Hierarchical porous PLLA/ACP fibrous membrane towards bone tissue scaffold

Electrospun fibres have emerged as vital components in developing tissue engineering scaffolds. Calcium phosphate-based materials, renowned for their bioactivity and biocompatibility, have garnered considerable attention in biomedical applications. This study focuses on the incorporation of amorphous calcium phosphate (ACP) nanoparticles into poly(L-lactic acid) (PLLA) to produce electrospun PLLA/ACP fibrous membranes. Subsequent treatment with acetone yielded a hierarchical porous structure, boasting an ultra-high surface area of 94.7753 ± 0.3884 m2/g. The ACP nanoparticles, initially encapsulated by PLLA, were exposed on the fibre surface after acetone treatment. Furthermore, the porous PLLA/ACP fibrous membrane exhibited superior mechanical properties (Young's modulus = 0.148 GPa, tensile strength = 3.05 MPa) and enhanced wettability. In a 7-day in vitro cell culture with human osteoblast-like cells, the porous PLLA/ACP fibrous membrane demonstrated a significant improvement in osteoblast adhesion and proliferation, with a proliferation rate increase of 252.0% and 298.7% at day 4 and day 7, respectively. These findings underscore the potential of the porous PLLA/ACP fibrous membrane as a promising candidate for bone tissue scaffolds.

Bandgap engineering approach for synthesising photoactive novel Ag/HAp/SnS2 for removing toxic anti-fungal pharmaceutical from aqueous environment

The present work shed light on synthesising a novel ternary Z-scheme Ag/HAp/SnS2 (AHS) nano photocatalyst to degrade metronidazole (MTZ) in wastewater through H2O2-assisted AOP under natural sunlight. HAp extracted from the fish scales of rohu fish through alkaline treatment was decorated with Ag nanoparticles using ascorbic acid as a bio-reductant. Tin disulphide (SnS2) was anchored over Ag/HAp to prevent agglomeration and enhance photocatalytic activity by delaying the electron-hole recombination rate. After 45 min of irradiation, a degradation efficiency of 98.85 ± 1.86% for 15 ppm MTZ could be achieved. The performance of the prepared photocatalyst in real wastewater was investigated by introducing several metal cations and anions in the photodegradation process. The degradation products were identified by HRLCMS analysis, and the breakdown mechanism of MTZ was proposed. The present study enlightens the importance of SnS2-based photocatalysts for organic pollutant degradation under natural sunlight through an advanced oxidation process. The characterization results showed that the enhanced photodegradation efficiency of AHS is attributed to the formation of an all-solid-state Z-scheme heterojunction with Ag nanoparticles acting as charge transfer medium and as electron accumulators helping in delaying charge recombination.

Pseudo-equilibrium equations for calcium phosphate precipitation with multi-unit particles

The chemistry underlying bone mineral formation in vertebrates is the reaction of calcium phosphate precipitation. In a near-neutral solution, an amorphous phase and hydroxyapatite nanoparticles appear successively, and the reaction system containing either of the two kinds of precipitates is in a non-equilibrium state. Here, we propose a pseudo-equilibrium approach to the solution chemistry of the precipitation reactions. We employed two series of reaction systems, collected samples at various stages, and analyzed the solution chemistry data on the basis of a simplified model of reaction. We derived two types of pseudo-equilibrium equations from the two series, respectively. These equations reveal the existence of multiple structural units in a precipitate particle and correlate the ionic product with the surface proportion per structural unit (m). The surface proportion, in turn, is related to the whole particle through a particle-surface equation. Notably, the two types of pseudo-equilibrium constants have the common expression of "Kd = ionic product" if the number of the structural units (u) is large enough. Together, these findings have revealed some aspects of the non-equilibrium thermodynamics of precipitation reactions, indicating the solution chemistry route to the equilibrium state. The concept of the multi-unit particle may shed new light on the study of precipitation reactions of other slightly soluble electrolytes. And the relationship between the ionic product and the surface proportion of a structural unit is not only fundamental in chemistry, but may also apply to non-equilibrium systems in nature and biology, such as marine sedimentation, human vascular calcification, and bone mineral metabolism.

Fabrication and Characterization of a Polydopamine-Modified Bacterial Cellulose and Sugarcane Filter Cake-Derived Hydroxyapatite Composite Scaffold

The search for environmentally friendly and sustainable sources of raw materials has been ongoing for quite a while, and currently, the utilization and applications of agro-industrial biomass residues in biomedicine are being researched. In this study, a polydopamine (PDA)-modified bacterial cellulose (BC) and hydroxyapatite (HA) composite scaffold was fabricated using the freeze-drying method. The as-prepared hydroxyapatite was synthesized via the chemical precipitation method using sugarcane filter cake as a calcium source, as reported in a previous study. X-ray diffraction analysis revealed a carbonated phase of the prepared hydroxyapatite, similar to that of the natural bone mineral. Wide-angle X-ray scattering analysis revealed the successful fabrication of BC/HA composite scaffolds, while X-ray photoelectron spectroscopy suggested that PDA was deposited on the surface of the BC/HA composite scaffolds. In vitro cell viability assays indicated that BC/HA and PDA-modified composite scaffolds did not induce cytotoxicity and were biocompatible with MC3T3-E1 preosteoblasts. PDA-modified composite scaffolds showed enhanced protein adsorption capacity in vitro compared to the unmodified scaffolds. On a concluding note, these results demonstrate that agro-industrial biomass residues have the potential to be used in biomedical applications and that PDA-modified BC/HA composite scaffolds are a promising biomaterial for bone tissue engineering.

Multifunctional Nanomaterials for Biofortification and Protection of Tomato Plants

Calcium phosphate nanoparticles were doped with zinc ions to produce multifunctional nanomaterials for efficient agronomic fortification and protection of plants. The resulting round-shaped nanoparticles (nanoZn) were composed of 20.3 wt % Ca, 14.8 wt % P, and 13.4 wt % Zn and showed a pH-controlled solubility. NanoZn were stable in aqueous solutions at neutral pH but dissolved in citric acid at pH 4.5 (i.e., the pH inside tomato fruits), producing a pH-responsive delivery of the essential nutrients Ca, P, and Zn. In fact, the foliar application of nanoZn on tomato plants provided tomatoes with the highest Zn, Ca, and P contents (causing, respectively, a 65, 65, and 15% increase with respect to a conventional treatment with ZnSO4) and the highest yields. Additionally, nanoZn (100 ppm of Zn) inhibited in vitro the growth of Pseudomonas syringae (Ps), the main cause of bacterial speck, and significantly reduced Ps incidence and mortality in tomato seeds, previously inoculated with the pathogen. Therefore, nanoZn present dual agricultural applicability, enriching crops with nutrients with important metabolic functions in humans and simultaneously protecting the plants against important bacterial-based diseases, with considerable negative impact in crop production.

Exploring Multifunctional Response of Ca10(PO4)6(OH)2-K0.5Na0.5NbO3 Ceramic Composite for Biomedical Applications

This study focuses on investigating the intriguing properties of Ca10(PO4)6(OH)2 (HAP)-K0.5Na0.5NbO3 (KNN) bioceramic composites, seeking to elucidate the relationship between their structural, electrical, biological, and optical behavior. The article begins with a close inspection of the O 1s spectra of the specimens obtained from X-ray photoelectron spectroscopy (XPS). The spectra reveal the peak related to lattice oxygen, O vacancy and the surface adsorbed O. The formed O vacancy strongly influences the changes in lattice parameters as observed from the X-ray diffraction (XRD) patterns. The frequency variation of the dielectric response for the composites in the radio frequency (RF) regime has electrical polarization effective for biomedical applications. Nyquist plots along with equivalent RC circuits further confirm that those electrical responses are mainly contributed from the grain boundaries. Adsorption dynamics of protein on the ceramic surface are investigated using bovine serum albumin (BSA), which established the major role of electrostatic interaction. Surface charge and O vacancies are modeled to understand the adsorption of protein and a linear correlation is reported. The role of O vacancies in modulating adsorption dynamics adds a new dimension to this study. The conformational change of BSA has also been considered by constructing the secondary structure following the protein-ceramic interaction. Excitingly, the composites are also found to be fluorescent active, a courtesy of the defects and vacancies leading to electron-hole recombination in the forbidden region. These promising properties envision an exciting future for HAP-KNN composites, especially in the domain of bioimaging and bone-tissue engineering.

Compositional Analysis of the Dental Biomimetic Hybrid Nanomaterials Based on Bioinspired Nonstoichiometric Hydroxyapatite with Small Deviations in the Carbonate Incorporation

In our paper, we discuss the results of a comprehensive structural-spectroscopic and microscopic analysis of non-stoichiometric nanocrystalline hydroxyapatite (CHAp) with low carbonate anion content and biomimetic hybrid nanomaterials produced on its basis. It was shown that hydroxyapatite nanocrystals synthesized by chemical precipitation and biogenic calcium source mimic the properties of biogenic apatite and also have a morphological organization of "core-shell" type. The "core" of the CHAp nanocrystal is characterized by an overabundance of calcium Ca/P~1.9. Thus "a shell" with thickness of ~3-5 nm is formed from intermediate apatite-like phases where the most probable are octocalcium phosphate, dicalcium phosphate dihydrate and tricalcium phosphate. The multimode model of the Raman profile of samples CHAp and biomimetic composites for spectral region 900-1100 cm-1 proposed in our work has allowed to allocate precise contribution of B-type carbonate substitution, taking into account the presence on a surface of "core" HAp nanocrystal of various third-party intermediate apatite-like phases. The calibration function constructed on the basis of the described model makes it possible to reliably determine small concentrations of carbonate in the structure of hydroxyapatite with the application of Raman express method of diagnostics. The results of our work can inspire researchers to study the processes of induced biomineralization in mineralized tissues of the human body, using non-destructive methods of control with simultaneous analysis of chemical bonding, as well as determining the role of impurity atoms in the functions exhibited by biotissue.

Calcium Phosphates-Chitosan Composite Layers Obtained by Combining Radio-Frequency Magnetron Sputtering and Matrix-Assisted Pulsed Laser Evaporation Techniques

In this work, we report the synthesis of calcium phosphate-chitosan composite layers. Calcium phosphate layers were deposited on titanium substrates by radio-frequency magnetron sputtering technique by varying the substrate temperature from room temperature (25 °C) up to 100 and 300 °C. Further, chitosan was deposited by matrix-assisted pulsed laser evaporation technique on the calcium phosphate layers. The temperature at the substrate during the deposition process of calcium phosphate layers plays an important role in the embedding of chitosan, as scanning electron microscopy analysis showed. The degree of chitosan incorporation into the calcium phosphate layers significantly influence the physico-chemical properties and the adherence strength of the resulted layers to the substrates. For example, the decreases of Ca/P ratio at the addition of chitosan suggests that a calcium deficient hydroxyapatite structure is formed when the CaP layers are generated on Ti substrates kept at room temperature during the deposition process. The Fourier transform infrared spectroscopy analysis of the samples suggest that the PO₄^3-/CO₃^2- substitution is possible. The X-ray diffraction spectra indicated that the crystalline structure of the calcium phosphate layers obtained at the 300 °C substrate temperature is disturbed by the addition of chitosan. The adherence strength of the composite layers to the titanium substrates is diminished after the chitosan deposition. However, no complete exfoliation of the layers was observed.

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 PO₄^3-. 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.

Carbon Dots Derived from Os Draconis and Their Anxiolytic Effect

Background

At present, people are susceptible to developing depression and anxiety disorders in response to stress. However, there is no specific medicine for anxiety. Os Draconis (OD, named "Long gu" in Chinese) are fossilized bones that have been used in traditional Chinese medicine to treat neurological diseases for thousands of years. Thus, we conducted this study to determine the biological basis for the anxiolytic effect of OD.

Methods

In this study, novel carbon dots (OD-CDs) from OD decoctions were discovered and separated. OD-CDs were anatomized using nanomaterials characterization methods to characterize the morphological structure, optical properties, and functional group properties. Four behavioural tests were conducted to observe the behavioural activities of mice, including the open field test (OFT), light/dark box test (LDT), elevated plus maze test (EPMT), and novelty-suppressed feeding test (NSFT), to determine its anxiolytic effects. Moreover, we assessed the possible mechanisms of the OD-CDs by detecting hormones associated with the hypothalamic-pituitary-adrenal (HPA) axis.

Results

OD-CDs were spherical and monodispersed with a narrow size distribution between 1 and 5 nm and had a yield of 3.67%. OD-CDs increased the activity time of mice in the central zone in the OFT. The mice in the experimental group showed more frequent activity in the light compartment and the open arms, in LDT and EPMT, respectively. In addition, OD-CDs shortened the feeding latency in the NSFT. Furthermore, the results after OD-CDs intervention showed a significant increase in serum serotonin (5-HT) and norepinephrine (NE). In addition, the concentrations of corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ATCH), and corticosterone (CORT) were decreased.

Conclusion

These results demonstrate a definite anxiolytic effect of OD-CDs and reveal the possible mechanism of action of OD-CDs' anxiolytic effect, which supports the research of OD for neurological disorders and a promising new trend of therapeutic approach and drug development.

In situ preparation of hydroxyapatite in lamellar liquid crystals for joint lubrication and drug delivery

Arthritis is a disease that seriously affects the quality of human life, which is partly caused by the reduction of joint lubrication performance. Thus, for the treatment of arthritis, how to improve the lubrication performance of joints is important. The lamellar liquid crystals (LLCs) systems have the potential to be used as joint lubrication due to their double-layer structure and good biocompatibility, however, the LLCs system alone could not provide a satisfactory lubrication effect. Herein, this work synthesized hydroxyapatite (HAP) in situ inside Tween 85/Tween 80/H₂O LLCs to construct a biocompatible HAP/Tween 85/Tween 80/H₂O LLCs (HAP/LLCs) lubrication system with both sustained drug release properties and anti-wear properties. HAP is the main component of bone with good stability and bioactivity. The LLCs have good lubricating and drug-carrying properties. The impact of HAP on the structure and lubrication properties of LLCs, the mechanism of friction, and the anti-wear reduction of HAP/LLCs were investigated. Moreover, the drug release behavior of the ibuprofen-loaded HAP/LLCs during the friction process was also studied. The results indicated that the addition of HAP could improve the lubricity performance of LLCs. The cumulative drug releasing increased with the friction frequency and was less affected by the load. The related studies provided the theoretical basis for HAP/LLCs for joint lubrication and synergistic therapy.

Altering Microbiomes with Hydroxyapatite Nanoparticles: A Metagenomic Analysis

Hydroxyapatite (HAp), the most abundant biological material among mammals, has been recently demonstrated to possess moderate antibacterial properties. Metagenomics provides a series of tools for analyzing the simultaneous interaction of materials with larger communities of microbes, which may aid in optimizing the antibacterial activity of a material such as HAp. Here, a microbiome intrinsic to the sample of sandy soil collected from the base of an African Natal plum (Carissa macrocarpa) shrub surrounding the children's sandbox at the Arrowhead Park in Irvine, California was challenged with HAp nanoparticles and analyzed with next-generation sequencing for hypervariable 16S ribosomal DNA base pair homologies. HAp nanoparticles overwhelmingly reduced the presence of Gram-negative phyla, classes, orders, families, genera and species, and consequently elevated the relative presence of their Gram-positive counterparts. Thermodynamic, electrostatic and chemical bonding arguments were combined in a model proposed to explain this selective affinity. The ability of amphiphilic surface protrusions of lipoteichoic acid in Gram-positive bacteria and mycolic acid in mycobacteria to increase the dispersibility of the bacterial cells and assist in their resistance to capture by the solid phase is highlighted. Within the Gram-negative group, the variability of the distal, O-antigen portion of the membrane lipopolysaccharide was shown to be excessive and the variability of its proximal, lipid A portion insufficient to explain the selectivity based on chemical sequence arguments. Instead, flagella-driven motility proves to be a factor favoring the evasion of binding to HAp. HAp displayed a preference toward binding to less pathogenic bacteria than those causative of disease in humans, while taxa having a positive agricultural effect were largely captured by HAp, indicating an evolutionary advantage this may have given it as a biological material. The capacity to selectively sequester Gram-negative microorganisms and correspondingly alter the composition of the microbiome may open up a new avenue in environmental and biomedical applications of HAp.

Role of nanostructured materials in hard tissue engineering

The rise in the use of biomaterials in bone regeneration in the last decade has exponentially multiplied the number of publications, methods, and approaches to improve and optimize their functionalities and applications. In particular, biomimetic strategies based on the self-assembly of molecules to design, create and characterize nanostructured materials have played a very relevant role. We address this idea on four different but related points: self-setting bone cements based on calcium phosphate, as stable tissue support and regeneration induction; metallic prosthesis coatings for cell adhesion optimization and prevention of inflammatory response exacerbation; bio-adhesive hybrid materials as multiple drug delivery localized platforms and finally bio-inks. The effect of the physical, chemical, and biological properties of the newest biomedical devices on their bone tissue regenerative capacity are summarized, described, and analyzed in detail. The roles of experimental conditions, characterization methods and synthesis routes are emphasized. Finally, the future opportunities and challenges of nanostructured biomaterials with their advantages and shortcomings are proposed in order to forecast the future directions of this field of research.

Urchin-like structured magnetic hydroxyapatite for the selective separation of cerium ions from aqueous solutions

In this study, bio-inspired urchin-like structured hydroxyapatite (UHdA) and its magnetic composite (UHdA@Fe₃O₄) were developed for efficient and easy separation of cerium ions (Ce³⁺) from aquatic waste streams. UHdA and UHdA@Fe₃O₄ exhibited superior Ce³⁺ adsorption capacities of 248.39 and 230.01 mg/g-UHdA respectively, compared to a commercial HdA (141.71 mg/g-HdA) due to their hierarchical mesoporous structure and large specific surface area. The adsorption of Ce³⁺ to UHdA and UHdA@Fe₃O₄ were heterogeneous, pseudo-second-order-kinetic, and the rate-limiting step was external mass transfer and intra-particle diffusion. Moreover, thermodynamic studies revealed that the adsorption process was spontaneous and endothermic nature. The high selectivity towards Ce³⁺ in multi-ionic systems is attributed to the strong affinity between strong Lewis acid (Ce³⁺) and base (PO₄^3- and OH^-) interactions. XRD, FTIR, and XPS analysis demonstrated that the adsorption was mainly attributable to the ion exchange of Ce³⁺ with Ca²⁺ and to surface complexation. The desorption of Ce³⁺ was efficiently accomplished using 0.1 M HNO₃. The results suggest that UHdA and UHdA@Fe₃O₄ could be promising choices for the adsorption and recovery of rare earth elements.

Sorption of Cd2+ on Bone Chars with or without Hydrogen Peroxide Treatment under Various Pyrolysis Temperatures: Comparison of Mechanisms and Performance

In this study, bone char pretreated with hydrogen peroxide and traditional pyrolysis was applied to remove Cd2+ from aqueous solutions. After hydrogen peroxide pretreatment, the organic matter content of the bone char significantly decreased, while the surface area, the negative charge and the number of oxygen-containing functional groups on the bone char surface increased. After being pyrolyzed, the specific surface area and the negative charge of the material were further improved. The adsorption kinetics and isotherms of Cd2+ adsorption were studied, and the influence of solution pH and the presence of ionic species were investigated. The experimental results showed that the samples with lower crystallinity exhibited less organic matter content and more surface oxygen-containing functional groups, resulting in stronger adsorption capacity. After being treated with hydrogen peroxide and pyrolyzed at 300 °C, the maximum adsorption capacity of bone char was 228.73 mg/g. The bone char sample with the lowest adsorption capacity(47.71 mg/g) was pyrolyzed at 900 °C without hydrogen peroxide pretreatment. Ion exchange, surface complexation, and electrostatic interactions were responsible for the elimination of Cd2+ by the bone char samples. Overall, this work indicates that hydrogen peroxide-treated pyrolytic bone char is a promising material for the immobilization of Cd2+.

Sustainable phosphorus management in soil using bone apatite

Soil fertility and phosphorus management by bone apatite amendment are receiving increasing attention, yet further research is needed to integrate the physicochemical and mineralogical transformation of bone apatite and their impact on the supply and storage of phosphorus in soil. This study has examined bone transformation in the field over a span of 10-years using a set of synchrotron-based microscopic and spectroscopic techniques. Transmission X-ray microscopy (TXM) observations reveal the in-situ deterioration of bone osteocyte-canaliculi system and sub-micron microbial tunneling within a year. Extensive organic decomposition, secondary mineral formation and re-mineralization of apatite are evident from the 3rd year. The relative ratio of (v₁ + v₃) PO₄^3- to v₃ CO₃^2- and to amide I increase, and the v_3c PO₄^3- peak exhibits a blue-shift in less than 3 years. The carbonate substitution of bone hydroxyapatite (HAp) to AB-type CHAp, and phosphate crystallographic rearrangement become apparent after 10 years' aging. The overall CO₃^2- peak absorbance increases over time, contributing to a higher acid susceptibility in the aged bone. The X-ray Photoelectron Spectroscopy (XPS) binding energies for Ca (2p), P (2p) and O (1s) exhibit a red-shift after 1 year because of organo-mineral interplay and a blue-shift starting from the 3rd year as a result of the de-coupling of mineral and organic components. Nutrient supply to soil occurs within months via organo-mineral decoupling and demineralization. More phosphorus has been released from the bones and enriched in the associated and adjacent soils over time. Lab incubation studies reveal prominent secondary mineral formation via re-precipitation at a pH similar to that in soil, which are highly amorphous and carbonate substituted and prone to further dissolution in an acidic environment. Our high-resolution observations reveal a stage-dependent microbial decomposition, phosphorus dissolution and immobilization via secondary mineral formation over time. The active cycling of phosphorus within the bone and its interplay with adjacent soil account for a sustainable supply and storage of phosphorus nutrients.

A biomimetic approach to evaluate mineralization of bioactive glass-loaded resin composites

PURPOSE

This study explores novel solutions other than standard SBF for biomimetic evaluations of mineralization particularly for resin composites containing bioactive glass (BAG).

METHODS

Experimental UDMA/TEGDMA resin composites with 0.0, 1.9, 3.8 or 7.7 vol% of 45S5 BAG fillers were prepared. Besides simulated body fluid (SBF) as control, the specimens were immersed in three other solutions either with bicarbonate which are Hank's balanced salt solution (HBSS) and cell culture medium (MEM), or without bicarbonate which is a novel Simple HEPES-containing Artificial Remineralization Promotion (SHARP) solution, for 3, 7 and 14 days. These solutions were then analyzed by ICP-OES and pH, and the surfaces of the BAG composites were analyzed by SEM, XRD and FTIR.

RESULTS

ICP-OES revealed Ca and P concentration continuously decrease, while Si concentration increases with time in the solutions other than SBF, which showed almost unchanged elemental concentration. Only SHARP solution is able to maintain a constant pH over the immersion time. SEM, together with XRD and FTIR, showed nano-sized octacalcium phosphate (OCP) nanospheres formation on 3.8 and 7.7 vol% BAG composites after 14 days immersion in HBSS (500-600 nm) and MEM (300-400 nm). SHARP solution enabled OCP formation after 3 days and then self-assembled into urchin-like carbonated hydroxyapatite (CHA) microspheres encompassed with nanorods of 100 nm width and 8 µm length after 14 days of immersion for 7.7 vol% BAG composites.

CONCLUSION

This study suggests SHARP solution can evaluate mineralization biomimetically whereas CHA microspheres can be formed on BAG-containing resin composites.

Catalytic reduction of 4-nitrophenol using CuO@Na2Ti(PO4)2⋅H2O

This article presents the synthesis, property characterization and catalytic application of CuO-supported disodium titanium phosphate, (CuO@Na₂Ti(PO₄)₂⋅H₂O) for the reduction of industrial pollutant 4-nitrophenol (4-NP). A simple hydrothermal route was developed to synthesize CuO@Na₂Ti(PO₄)₂⋅H₂O catalyst (CuO@Na₂TiP) from beach sand ilmenite. The prepared CuO@Na₂TiP was characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and nitrogen adsorption-desorption isotherms. The catalyst 12 wt.% CuO@Na₂TiP showed the fastest reduction kinetics for 4-NP.

Synthetic amorphous calcium phosphates (ACPs): preparation, structure, properties, and biomedical applications

Amorphous calcium phosphates (ACPs) represent a metastable amorphous state of other calcium orthophosphates (abbreviated as CaPO₄) possessing variable compositional but rather identical glass-like physical properties, in which there are neither translational nor orientational long-range orders of the atomic positions. In nature, ACPs of a biological origin are found in the calcified tissues of mammals, some parts of primitive organisms, as well as in the mammalian milk. Manmade ACPs can be synthesized in a laboratory by various methods including wet-chemical precipitation, in which they are the first solid phases, precipitated after a rapid mixing of aqueous solutions containing dissolved ions of Ca²⁺ and PO₄^3- in sufficient amounts. Due to the amorphous nature, all types of synthetic ACPs appear to be thermodynamically unstable and, unless stored in dry conditions or doped by stabilizers, they tend to transform spontaneously to crystalline CaPO₄, mainly to ones with an apatitic structure. This intrinsic metastability of the ACPs is of a great biological relevance. In particular, the initiating role that metastable ACPs play in matrix vesicle biomineralization raises their importance from a mere laboratory curiosity to that of a reasonable key intermediate in skeletal calcifications. In addition, synthetic ACPs appear to be very promising biomaterials both for manufacturing artificial bone grafts and for dental applications. In this review, the current knowledge on the occurrence, structural design, chemical composition, preparation, properties, and biomedical applications of the synthetic ACPs have been summarized.

Development of Biodegradable Bio-Based Composite for Bone Tissue Engineering: Synthesis, Characterization and In Vitro Biocompatible Evaluation

Several significant advancements in the field of bone regenerative medicine have been made in recent years. However, therapeutic options, such as bone grafts, have several drawbacks. There is a need to develop an adequate bone substitute. As a result, significant bone defects/injuries pose a severe challenge for orthopaedic and reconstructive bone tissue. We synthesized polymeric composite material from arabinoxylan (ARX), β-glucan (BG), nano-hydroxyapatite (nHAp), graphene oxide (GO), acrylic acid (AAc) through free radical polymerization and porous scaffold fabricated using the freeze-drying technique. These fabricated porous scaffolds were then coated with chitosan solution to enhance their biological activities. The complex structure of BG, nHAp, GO was studied through various characterization and biological assays. The structural, morphological, wetting and mechanical analyses were determined using FT-IR, XRD, XPS, SEM/EXD, water contact angle and UTM. The swelling (aqueous and PBS media) and degradation (PBS media) observed their behavior in contact with body fluid. The biological activities were conducted against mouse pre-osteoblast cell lines. The result found that BGH3 has desirable morphological, structural with optimum swelling, degradation, and mechanical behavior. It was also found to be cytocompatible against MC3T3-E1 cell lines. The obtained results confirmed that the fabricated polymeric scaffolds would be a potential bone substitute to regenerate defective bone with different loading bearing applications for bone tissue engineering.

Systematic changes of bone hydroxyapatite along a charring temperature gradient: An integrative study with dissolution behavior

The applicability of bone char as a long-term phosphorus nutrient source was assessed by integrating their mineral transformation and physicochemical properties with their dissolution behavior. We have explored synchrotron-based spectroscopic and imaging techniques (FTIR, XRD, and TXM) to investigate the physicochemical changes of bone and bone char along a charring temperature gradient (300-1200 °C) and used a lab incubation experiment to study their dissolution behaviors in solutions of different pH (4, 6, and 6.9). The thermal decomposition of inorganic carbonate (CO₃^2-) and the loss of organic components rendered a crystallographic rearrangement (blueshift of the PO₄^3- peak) and mineral transformation with increasing temperatures. The mineral transformation from B-type to AB- and A-type carbonate substitution occurred mainly at <700 °C, while the transformation from carbonated hydroxyapatite (CHAp) to more mineralogically and chemically stable HAp occurred at >800 °C. The loss of inorganic carbonate and the increase of structural OH^- with increasing temperatures explained the change of pH buffering capacity and increase of pH and their dissolution behaviors. The higher peak area ratios of phosphate to carbonate and phosphate to amide I band with increasing temperatures corroborated the higher stability and resistivity to acidic dissolution by bone chars made at higher temperatures. Our findings suggest that bone char made at low to intermediate temperatures can be a substantial source of phosphorus for soil fertility via waste management and recycling. The bone char made at 500 °C exhibited a high pH buffering capacity in acidic and near-neutral solutions. The 700 °C bone char was proposed as a suitable liming agent for raising the soil pH and abating soil acidity. Our study has underpinned the systematic changes of bone char and interlinked the charring effect with their dissolution behavior, providing a scientific base for understanding the applicability of different bone chars as suitable P-fertilizers.

Noble-metal-free hydroxyapatite activated by facile mechanochemical treatment towards highly-efficient catalytic oxidation of volatile organic compound

Controlling of volatile organic compound (VOC) emitted from industrial processes as most abundant and harmful air pollutant, has become one of the most important global environmental issues due to the rapid urbanization and industrialization. As an alternative and new type catalyst instead of conventional noble-metal nanoparticles widely utilized in oxidative decomposition of VOC, here we report the superior catalytic performance with 100% CO₂/CO conversion on hydroxyapatite (HAp, Ca₁₀(PO₄)₆(OH)₂) with structurally well-controlled active surface tailored via facile one-step mechanochemical treatment in ambient air. With detailed characterizations of particle morphology, crystallinity and chemical structure with respects to surface defect/oxygen vacancy formation, acidity/basicity and VOC affinity on HAps activated through different mechanical stresses when altered ball size is utilized in planetary ball-milling assisted mechanochemical process, it was found that the predominant defect/oxygen vacancy generation in PO₄^3- site and enhanced basic site population established by selective mechanochemical activation of c-plane, facilitates the favorable catalytic oxidation route towards highly-efficient CO₂/CO conversion of VOC. Regards to the cost-effectiveness and non-toxic nature of HAp, incorporated with the sustainable mechanochemical surface structure tuning process, the results presented in this work opens new strategy in development of novel noble-metal-free catalyst for VOC elimination and environmental cleaning techniques.

Highly stable luminescent europium-doped calcium phosphate nanoparticles for creatinine quantification

The determination of creatinine levels is essential for the detection of renal and muscular dysfunction. Luminescent nanoparticles are emerging as fast, cheap and highly selective sensors for the detection and quantification of creatinine. Nevertheless, current nanosensors only have a short shelf life due to their poor chemical and colloidal stability, which limits their clinical functionality. In this work, we have developed a highly stable, selective and sensitive nanosensor based on europium-doped, amorphous calcium phosphate nanoparticles (Eu-ACP) for the determination of creatinine by luminescence spectroscopy. The colloidal stability of Eu-ACP nanoparticles in aqueous solutions was optimised to ensure a constant signal after up to 4 months in storage. The luminescence intensity of Eu-ACP decreased linearly with the creatinine concentration over the range of 1-120 μM (R² = 0.995). This concentration-response relationship was used to determine creatinine levels in real urine samples resulting in good recovery percentages. Significantly, selectivity assays indicated that none of the potential interfering species provoked discernible changes in the luminescence intensity.