Search

This contribution attempts to provide a state-of-the-art account of the physicochemical and biomedical properties of the plasma-sprayed hydroxylapatite (HAp) coatings that are routinely applied to the surfaces of metallic endoprosthetic and dental root implants designed to replace or restore the lost functions of diseased or damaged tissues of the human body. Even though the residence time of powder particles of HAp in the plasma jet is extremely short, the high temperature applied induces compositional and structural changes in the precursor HAp that severely affect its chemical and physical properties and in turn its biomedical performance. These changes are based on the incongruent melting behavior of HAp and can be traced, among many other analytical techniques, by high resolution synchrotron X-ray diffraction, vibrational (Raman) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. In vivo reactions of the plasma-sprayed coatings to extracellular fluid (ECF) can be assessed and predicted by in vitro testing using simulated body fluids (SBFs) as proxy agents. Ways to safeguard the appropriate biological performance of HAp coatings in long-term service by controlling their phase content, porosity, surface roughness, residual stress distribution, and adhesion to the implant surface are being discussed. [ABSTRACT FROM AUTHOR]

Shujie Wang,1,2 Chunyan Shao,2 Xingkai Zhao,1 Yizhe Guo,1 Houhui Song,2 Lida Shen,3 Zhenlei Zhou,1 Zhen Li4,5 1College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu, 210095, People’s Republic of China; 2College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang Agriculture and Forestry University, Hangzhou, Zhejiang, 311300, People’s Republic of China; 3College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, 210016, People’s Republic of China; 4College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, 210095, People’s Republic of China; 5State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing, Jiangsu, 210008, People’s Republic of ChinaCorrespondence: Zhenlei Zhou, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu, 210095, People’s Republic of China, Tel +86 (25) 84395505, Email zhouzl@njau.edu.cn Zhen Li, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, 210095, People’s Republic of China, Tel/Fax +86 (25) 84399827, Email lizhen@njau.edu.cnIntroduction: Hydroxylapatite (HAp) is a biodegradable bone graft material with high biocompatibility. However, the clinical application of HAp has been limited due to the poor absorption rate in vivo.Methods: In this study, carbonated hydroxylapatite (CHAp) with a chemical composition similar to natural bone was synthesized. HAp and CHAp scaffolds were fabricated by 3D printing. Each material was designed by two types of scaffold model with a maximum width of 8 mm and a thickness of 2 mm, ie, structure I (round shape) and structure II (grid shape). Then, the HAp scaffolds were loaded with lutein. These scaffolds were implanted into the 8 mm bone defect on the top of the rabbit skull within 3 hours in the morning. The curative effects of the scaffolds were assessed two months after implantation.Results: The 3D printed scaffolds did not cause severe inflammation or rejection after implantation. It showed that the porous structures allow bone cells to enter into the scaffolds. Furthermore, CHAp scaffolds were more biocompatible than HAp scaffolds, and showed a higher level of degradation and new bone formation after implantation. Structure II scaffolds with a smaller mineral content degraded faster than structure I, while structure I had better osteoconductive properties than structure II. Besides, the addition of lutein significantly enhanced the rate of new bone formation.Discussion: The uniqueness of this study lies in the synthesis of 3D printed CHAp scaffolds and the implantation of CHAp in rabbit bone defects. The incorporation of suitable carbonate and lutein into HAp can enhance the osteoinductivity of the graft, and CHAp has a faster degradation rate in vivo, all of which provide a new reference for the research and application of apatite-based composites.Keywords: bone, 3D printing, hydroxylapatite, lutein, repair

One of the challenges in agriculture practices is guaranteeing an adequate and bioavailable phosphorus supply for plants on phosphorus-deficient soils. A promising alternative lies in the utilization of phosphate nano-fertilizers (NFs) through spray applications. Therefore, this short-term study aimed to investigate the yet undetermined widespread impact of P-NFs on crops characterized by broad leaves, an intensive rate of photosynthesis, and belonging to the oilseed plant, sunflower (Helianthus annuus L.). To achieve this, NFs were applied at lower concentrations of various phosphate-based NFs, including (i) nano-hydroxylapatite (nano-Hap) and (ii) a mixture of nano-calcium zinc phosphate and macro-sized parascholzite (nano/macro-ZnPhos), in comparison to the NF-free control. The study was carried out under authentic field conditions during the 2022 vegetation season at the Dolná Malanta site within the Central European Region. The empirical evidence presented herein indicates that the utilization of biocompatible and bioactive nano-Hap, initially engineered for biomedical applications, and nano/macro-ZnPhos, now foliarly applied at reduced concentrations, elicited a statistically significant elevation in quantitative parameters and seasonal physiological responses. The parameters analyzed included head diameter, dry head weight, seed yield per hectare, nutritional seed oiliness, etc. as well as the physiological normalized difference vegetation index (NDVI), stomatal conductance index (Ig), and crop water stress index (CWSI). In terms of agro-ecological terrestrial bio/diversity, it was evident that the nano/macro-ZnPhos was the most hospitable variant for the terrestric insect community, but surprisingly, the agronomically more popular nano-Hap showed only statistically insignificant changes in the diversity of the detected communities. However, the relevance of outcomes highlighted using nano-fertilizers, supporting the concept of precision and sustainable agriculture under field conditions. [ABSTRACT FROM AUTHOR]

The gas-detonation technique was used for the synthesis of biocompatible hydroxylapatite-based protective coatings on polymer and titanium substrates. Hydroxylapatite powder of high purity with a grain diameter of 50 µm was used as the raw material. The obtained coatings have the thickness close to 200 µm. It has been shown that the offered method enables to create of non-destructive hydroxylapatite-based coatings on polymer by varying the distance between the polymer target and the gun nozzle of gasdetonation setup. Using the data of Raman and X-ray measurements, it was ascertained that gas-detonation deposition doesn’t change the composition of the deposited material. The SEM investigation testifies that the formed hydroxylapatite-based coatings are porous. EPR studies have shown that there are no paramagnetic defects in the obtained coatings, and the coating itself has a higher radiation hardness as compared to the raw powder. [ABSTRACT FROM AUTHOR]

Valuable 5-amino-1-pentanol (5-AP) was efficiently synthesized from biomass-derived dihydropyran over hydroxylapatite nanorod supported Ni catalysts (Ni-HAP), by coupling the in situ generation of 5-hydroxypentanal (5-HP, via the ring-opening tautomerization of 2-hydroxytetrahydropyran (2-HTHP)) and its subsequent reductive amination. The Ni-HAP catalyst with 10 wt% Ni loading exhibited the highest 5-AP yield than the other Ni-HAP catalysts with different Ni loadings and several commercial hydrogenation catalysts, including Ru/C, Pt/C and Pd/C, as well as Raney Ni. High Ni particles dispersion, high reducibility and acidic intensity were found to account for the superior catalytic performance of 10Ni-HAP. The effect of reaction parameters on the catalytic performance was investigated, and an excellent 5-AP yield of 92% was achieved under mild reaction conditions of 80 °C and 2 MPa H2. The stability of the Ni-HAP catalyst was studied using a continuous flow reactor, and the sintering of Ni nanoparticles was considered as the major reason for the decline in hydrogenation activity. The Ni-HAP catalyst exhibited high catalytic performance to synthesis 5-AP due to the high Ni particles dispersion, reducibility and acidic intensity. [ABSTRACT FROM AUTHOR]

BACKGROUND: Transnasal-sphenoidal neuroendoscopic surgery has become the most common surgical method for anterior skull base midline and lateral skull base location due to its characteristics of minimal invasion, full exposure and quick recovery. With the continuous expansion of surgical indications, the scope of skull base opening becomes larger and larger, then the incidence of postoperative cerebrospinal fluid leakage is correspondingly increasing. Severe cerebrospinal fluid leakage can cause fatal intracranial infection. Therefore, after neuroendoscopic resection of tumors, reliable skull base reconstruction is an essential condition for successful surgery. In this paper, the principles and methods of skull base reconstruction and biological properties of different materials used in skull base reconstruction are reviewed. OBJECTIVE: To expound the principles and methods of skull base reconstruction, summarize the research progress of different reconstruction materials and the role of different biological characteristics in skull base reconstruction. METHODS: Articles were retrieved on Wanfang and PubMed databases published from January 2012 to January 2022. The Chinese and English search terms were “skull base reconstruction, neuroendoscopy, skull base bone defect, transnasal-sphenoidal operative approach, multiple repair, pedicled mucosal flap, polyether-ether-ketone (PEEK), hydroxylapatite”. Finally, 60 articles were included for review. RESULTS AND CONCLUSION: (1) Even if the skull base defect is getting bigger and bigger, the purpose of skull base reconstruction is still to prevent cerebrospinal fluid leakage and avoid serious complications after transnasal-sphenoidal neuroendoscopic surgery. Multilayer repair is a universally accepted principle. (2) Bone-like materials such as polyether-ether-ketone and hydroxylapatite for bony support are less clinically used because of their high price and cumbersome preoperative preparation. Clinicians mostly rely on dural-like biomaterials and pedicled mucosal flaps to complete the repair. However, limited by the weak repair support and the blood supply of the mucosal flap, a small number of patients still have a certain risk of cerebrospinal fluid leakage. (3) Therefore, intraoperative dura-like and bone-like structure artificial biomaterials and pedicled mucosal flaps to repair skull base defects are in line with the restoration of the anatomical repair of the skull base, and are helpful for the regeneration of the dura and bone structures. The research and development of biomaterials integrating hydrophobic tissue + dural-like mater + bone-like structure + mucosa have great prospects for skull base reconstruction. [ABSTRACT FROM AUTHOR]

Due to the development of modern biotechnologies and nanomaterials, in the near future it is expected to achieve a new, higher quality level in the design and improvement of the characteristics of intraosseous implants used in orthopedics. Calcium phosphate was synthesized from a model solution of synovia in the presence of albumin. Synthetic solid phases were studied using X-ray phase analysis, IR-Fourier spectroscopy, scanning electron microscopy, and energy dispersive analysis. The supernatant was examined for the presence of ions and to calculate the ratio. It was found that albumin does not affect the phase composition of the samples: the sediments are single-phase and consist of B-type hydroxylapatite carbonate. The study of the structure and morphology of the solid phase showed that the presence of proteins leads to formation of composites with a lower specific surface area compared to hydroxylapatite carbonate. The largest crystallite size is observed for the hydroxylapatite carbonate /albumin sample with the albumin concentration of 12 g/l. With the help of the thermal analysis of the fixation of thermal effects five stages of the thermal transformation were identified in the temperature range of 25-1000 °C; for all samples, the main stages are II–III, associated with the thermal destruction of organic additives. The study of the bioactivity of the samples showed that in the case of active resorption, the most soluble were the samples synthesized in the presence of albumin (>7 g/l), and in the case of passive resorption, the hydroxylapatite carbonate/albumin samples (5 and 7 g/l).

The review is based on the analysis of 53 literature sour­ces from PubMed, Google, Google Scholar, and Cochrane Library. Among the substitutes for autogenous bone grafts in spine surgery, ceramic biomaterials are the largest studied group, among which certain niche is occupied by calcium phosphate ceramics (CPCs). Hydroxylapatite, tricalcium phosphate and biphasic ceramics with all parts of hydroxylapatite and tricalcium phosphate are widely used in spine surgery. The advantage of using CPCs is their biocompa­tibility, osteoconductivity, osteoinductivity, osteoimmunomodulation and the ability to stimulate angiogenesis — the main components that ensure bone regeneration. In the given review, the peculiarities of regeneration in the interface “ceramic material — bone tissue” depending on the composition, surface structure, and crystallinity of the material are noted. The positive results of the experimental studies led to the use of CPCs in the clinic. CPCs with auto­genous bone grafts are successfully used in posterior and posterolateral lumbar spondylodesis, which allows reducing significantly the volume of autologous bone. A new direction is the development of non-metallic combined cages, which are used to perform anterior cervical discectomy and spondylodesis. The composition of these cages includes various polymers in combination with CPCs and bone autogenous graft to ensure high-quality spondylodesis, reduce of stress-shiel­ding and subsidence of the cage. A special approach requires the study of degradation and resorption by osteoclasts of various CPCs in order to control and synchronize the process of “resorption — bone formation”. Among the issues for the further research, the molecular mechanisms of osteoimunomodulation and factors that stimulate osseointegration and osteoinduction in the management of reparative osteogenesis should be further explored.

Background: Exosome research continues to flourish. Subsequent knowledge surrounding indications, dose–response, safety, efficacy, and the ability to combine exosome treatment as a "skin primer"—for biostimulation modalities such as calcium hydroxylapatite (CaHA), platelet‐rich plasma (PRP), and platelet‐rich fibrin matrix (PRFM) is growing rapidly. The objective of this study was to develop safe, reproducible methods of improving topical exosome absorption to enhance the quality of skin either by themselves, or in combination with injectable CaHA. Methods: Under IRB Approval (International Cell Surgical Society: ICSS‐2022‐007), 40 patients were enrolled in this study. Twenty patients underwent facial biostimulatory dermal infusion alone, to determine if this method allowed adequate exosome absorption. Five patients underwent facial biostimulatory infusion followed immediately by Dilute CaHA injection (1:1 dilution) to the face. Five patients underwent exosome biostimulatory dermal infusion followed immediately by hyperdilute CaHA (dilution 1:4) injection to the neck. Five patients underwent Facial Dilute CaHA injection (1:1 dilution) alone, without dermal infusion. Five patients underwent neck hyperdilute CaHA injection (1:4 dilution) alone, without dermal infusion. All patients had pretreatment Quantificare 3‐D photo‐documentation and skin analysis (Quantificare, France). In all patients, the skin was first cleansed with a gentle glycolic acid facial wash (Gregory MD). To induce a "homing inflammatory environment" for the exosomes, sea salt exfoliation was performed (SaltFacial®, SaltMed, Cardiff, CA). A nitric oxide—generating serum (N101 Pneuma Nitric Oxide, Austin, TX) was then applied to act as an enhanced vehicle for absorption. A 3 MHz ultrasound (SaltFacial®, SaltMed, Cardiff, CA) was then utilized to further deepen the absorption of the nitric oxide serum. A topical emulsion containing equal volumes (1.0 cc containing 1 million) of exosomes (Kimera Labs, Miramar, FL), 25 units of botulinum toxin (Xeomin, Merz Aesthetics, Raleigh, NC) and hyaluronic acid (Belatero, Merz Aesthetics, Raleigh, NC) was mixed via back‐and‐forth propulsion in a 3‐cc syringe. When adequately mixed, the emulsion was then applied to the treatment areas. The cavitating ultrasound was then used to aid in the absorption of the emulsion. The patients were then treated with high‐intensity LED therapy (SaltFacial®, SaltMed, Cardiff, CA), utilizing the collagen restoration preset program of combination red (660 nm) near‐infrared (930 nm) wavelength for 20 min. Post‐treatment Quantificare analysis was performed at 15 and 30 days after treatment. Results: Without exception, all dermal infusion alone and CaHA injection alone patients showed an improvement in the tone, quality, and texture of their skin. Quantificare results showed consistent improvement in wrinkles, pores, skin evenness, improved vascularity, and a reduction in oiliness and unwanted pigment. When employed as a skin primer prior to injections (CaHA), enhanced and more rapid results were seen. Conclusions: Biostimulatory dermal infusion can be achieved utilizing topical placental mesenchymal stem cell‐derived exosomes. These exosomes can be used alone, or mixed with ancillary ingredients such as botulinum toxin, hyaluronic acid dermal filler, and CaHA to customize and personalize treatments based upon individual patient needs. Topical absorption is enhanced with sea salt exfoliation, a topical nitric oxide‐generating serum, and 3 MHz cavitating ultrasound. Post‐absorption activity is enhanced with high‐intensity LED treatment. The addition of CaHA injections after the topical exosome "priming of the skin" yielded enhanced skin quality faster than exosomes or CaHA alone. [ABSTRACT FROM AUTHOR]

The mineral apatite, Ca10(PO4)6(F,OH,Cl)2, incorporates sulfur (S) during crystallization from S-bearing hydrothermal fluids and silicate melts. Our previous studies of natural and experimental apatite demonstrate that the oxidation state of S in apatite varies systematically as a function of oxygen fugacity (fO2). The S oxidation states –1 and –2 were quantitatively identified in apatite crystallized from reduced, S-bearing hydrothermal fluids and silicate melts by using sulfur K-edge X‑ray absorption near-edge structure spectroscopy (S-XANES) where S6+/ΣS in apatite increases from ~0 at FMQ-1 to ~1 at FMQ+2, where FMQ refers to the fayalite-magnetite-quartz fO2 buffer. In this study, we employ quantum-mechanical calculations to investigate the atomistic structure and energetics of S(-I) and S(-II) incorporated into apatite and elucidate incorporation mechanisms. One S(-I) species (disulfide, S 2 2 − ) and two S(-II) species (bisulfide, HS−, and sulfide, S2−) are investigated as possible forms of reduced S species in apatite. In configuration models for the simulation, these reduced S species are positioned along the c-axis channel, originally occupied by the column anions F, Cl, and OH in the end-member apatites. In the lowest-energy configurations of S-incorporated apatite, disulfide prefers to be positioned halfway between the mirror planes at z = 1/4 and 3/4. In contrast, the energy-optimized bisulfide is located slightly away from the mirror planes by ~0.04 fractional units in the c direction. The energetic stability of these reduced S species as a function of position along the c-axis can be explained by the geometric and electrostatic constraints of the Ca and O planes that constitute the c-axis channel. The thermodynamics of incorporation of disulfide and bisulfide into apatite is evaluated by using solid-state reaction equations where the apatite host and a solid S-bearing source phase (pyrite and Na2S2(s) for disulfide; troilite and Na2S(s) for sulfide) are the reactants, and the S-incorporated apatite and an anion sink phase are the products. The Gibbs free energy (ΔG) is lower for incorporation with Na-bearing phases than with Fe-bearing phases, which is attributed to the higher energetic stability of the iron sulfide minerals as a source phase for S than the sodium sulfide phases. The thermodynamics of incorporation of reduced S is also evaluated by using reaction equations involving dissolved disulfide and sulfide species [ H n S 2 (aq) (2 − n) and H n S (aq) (2 − n) ; n = 0 , 1 , and 2] as a source phase. The ΔG of S-incorporation increases for fluorapatite and chlorapatite, and decreases for hydroxyl-apatite, as these species are protonated (i.e., as n changes from 0 to 2). These thermodynamic results demonstrate that the presence of reduced S in apatite is primarily controlled by the chemistry of magmatic and hydrothermal systems where apatite forms (e.g., an abundance of Fe; solution pH). Ultimately, our methodology developed for evaluating the thermodynamics of S incorporation in apatite as a function of temperature, pH, and composition is highly applicable to predicting the trace and volatile element incorporation in minerals in a variety of geological systems. In addition to solid-solid and solid-liquid equilibria treated here at different temperatures and pH, the methodology can be easily extended to different pressure conditions by just performing the quantum-mechanical calculations at elevated pressures. [ABSTRACT FROM AUTHOR]

One of the challenges in agriculture practices is guaranteeing an adequate and bioavailable phosphorus supply for plants on phosphorus-deficient soils. A promising alternative lies in the utilization of phosphate nano-fertilizers (NFs) through spray applications. Therefore, this short-term study aimed to investigate the yet undetermined widespread impact of P-NFs on crops characterized by broad leaves, an intensive rate of photosynthesis, and belonging to the oilseed plant, sunflower (Helianthus annuus L.). To achieve this, NFs were applied at lower concentrations of various phosphate-based NFs, including (i) nano-hydroxylapatite (nano-Hap) and (ii) a mixture of nano-calcium zinc phosphate and macro-sized parascholzite (nano/macro-ZnPhos), in comparison to the NF-free control. The study was carried out under authentic field conditions during the 2022 vegetation season at the Dolná Malanta site within the Central European Region. The empirical evidence presented herein indicates that the utilization of biocompatible and bioactive nano-Hap, initially engineered for biomedical applications, and nano/macro-ZnPhos, now foliarly applied at reduced concentrations, elicited a statistically significant elevation in quantitative parameters and seasonal physiological responses. The parameters analyzed included head diameter, dry head weight, seed yield per hectare, nutritional seed oiliness, etc. as well as the physiological normalized difference vegetation index (NDVI), stomatal conductance index (Ig), and crop water stress index (CWSI). In terms of agro-ecological terrestrial bio/diversity, it was evident that the nano/macro-ZnPhos was the most hospitable variant for the terrestric insect community, but surprisingly, the agronomically more popular nano-Hap showed only statistically insignificant changes in the diversity of the detected communities. However, the relevance of outcomes highlighted using nano-fertilizers, supporting the concept of precision and sustainable agriculture under field conditions.

The archeological site at Sanxingdui preserves a considerable amount of ancient ivory tusks in its artifact pits, and accurately and quantitatively analyzing the original chemical signatures of these ivory tusks is a critical step in interpreting their buried history. In this study, 123 unearthed ivory tusks were characterized using Fourier-transformed infrared spectroscopy (FTIR), and seven in situ heating experiments were conducted. The hydroxylapatite crystallinity and carbonate concentration were quantitatively determined in line with the absorbance peak intensities of the corresponding bands. The average values of splitting factor (SF), type B carbonate/type A carbonate ratio (BC/AC), carbonate/phosphate ratio (C/P), type B carbonate/phosphate ratio (BPI), type A carbonate/phosphate ratio (API), and water–amide on the phosphate index (WAMPI) were calculated to be 3.84, 0.98, 0.12, 0.37, 0.38, and 0.11, respectively. The ratios of the 1,416 cm−1–1,454 cm−1 carbonate bands of the ivory tusks were used to quantitatively estimate the different types of carbonate content in the ivory tusks. Heating experiments were designed to simulate the effect of heat on the hydroxylapatite structures. We suggest that the SF and the C/P indices can serve as distinctive preservation indices of ancient ivory tusks as well as the BC/AC index and hydroxyl types.

The paper presents a study of the processes of precipitation of mineral-organic formations in a model solution of blood plasma in the presence of additives of albumin, glycine, glucose, glutamic and lactic acids. The phase composition of the samples was studied by the X-ray diffraction analysis. Photos were taken to measure the surface area of the sample with modified calcium phosphate. The solid phase coating areas were highlighted in the photos and the degree of coating of steel samples was calculated using the ToupView software. The deposition of the crystal phase occurs on all the studied samples. The differences are in the distribution of crystals on the surface of the plate. The additive albumin inhibits the deposition of hydroxyapatite on the studied samples. It is shown, that additions of glucose, glutamic and lactic acids catalyze the process of hydroxylapatite deposition on the surface of a steel sample. As a percentage of the total area of the image, the largest amount of precipitated hydroxylapatite powder is observed in samples with the addition of glucose.

The review is based on the analysis of 53 literature sources from PubMed, Google, Google Scholar, and Cochrane Library. Among the substitutes for autogenous bone grafts in spine surgery, ceramic biomaterials are the largeststudied group, amongwhich certain niche is occupied by calcium phosphate ceramics (CPCs). Hydroxylapatite, tricalcium phosphate and biphasic ceramics with all parts of hydroxylapatite and tricalcium phosphate are widely used in spine surgery. The advantage of using CPCs is their biocompatibility, osteoconductivity, osteoinductivity, osteoimmunomodulation and the ability to stimulate angiogenesis — the main components that ensure bone regeneration. In the given review, the peculiarities of regeneration in the interface “ceramic material — bone tissue” depending on the composition,surface structure, and crystallinity of the material are noted. The positive results of the experimentalstudiesled to the use of CPCsin the clinic. CPCs with autogenous bone grafts are successfully used in posterior and posterolateral lumbar spondylodesis, which allows reducing significantly the volume of autologous bone. A new direction is the development of non-metallic combined cages, which are used to perform anterior cervical discectomy and spondylodesis. The composition of these cagesincludes various polymers in combination with CPCs and bone autogenous graft to ensure high-quality spondylodesis, reduce of stress-shielding and subsidence of the cage. A special approach requires the study of degradation and resorption by osteoclasts of various CPCs in order to control and synchronize the process of “resorption — bone formation”. Among the issues for the further research, the molecular mechanisms of osteoimunomodulation and factorsthatstimulate osseointegration and osteoinduction in the management of reparative osteogenesis should be further explored. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bulk-incorporated Si effectively stabilized ACC for up to 680 days. • Si-ACC efficiently removed and recovered P from sludge and domestic sewage. • Si-ACC quickly transformed to nano calcite and reacted with P to form poor crystalline hydroxylapatite. • The recovered products have a maximum surface area of 209 m2/g and P 2 O 5 content of 18.0 %. • The recovered products could be a potential pollutant adsorbent and phosphate fertilizer. Phosphorus is a non–renewable resource that guarantees food production, while excessive phosphorus discharge leads to water eutrophication. Phosphorus removal/recovery could help improve water quality and ensure food security. In this contribution, silica–stabilized amorphous calcium carbonates (Si–ACC) were prepared and used to remove/recover phosphate in sludge and domestic sewage. The mechanisms were investigated via kinetic and isothermal adsorption studies and XRD, TEM, Raman, and FT–IR characterization. The results showed that the homogeneously distributed silica successfully inhibited ACC transformation and helped Si–ACC keep the amorphous feature within 680 d. During phosphorus adsorption, Si–ACC quickly transformed into calcite within 5 min and reacted with phosphorus to generate polycrystalline hydroxylapatite within 60 min. The recovered product possessed a maximum specific surface area (SSA) of 209 m2/g and available phosphorus content of 18.0 %, suggesting that Si–ACC was a promising phosphorus recovery material and the recovered product could be a potential phosphate fertilizer. [ABSTRACT FROM AUTHOR]

Porous hydroxyapatite-biochar composites with layered microstructures (SC–HA/C) were prepared by carbonizing sugarcane stem nodes and then soaking them in lime water and (NH4)2HPO4 solutions in rotation. The surface area of SC–HA/C ranges from 8.52 to 28.44 m2/g, and its microstructure inherits various macro-, meso-, and micro-pores in the cell walls of sugarcane and in the pits of the vessel walls. The maximum removal capacities were 11.50, 14.65, and 19.81 mg/g for the Cu (II) immobilization at 25 °C, 35 °C, and 45 °C with the solution Cu (II) concentration of 10~320 mg/L, respectively, which were in accordance with the copper sorption capacities of synthesized nano-hydroxylapatites. The Cu (II)-removal kinetics and isotherm followed the pseudo-second-order equation and the Langmuir equation very well. The formation of the Cu-containing hydroxylapatite solid solutions ((CuxCa1−x)5(PO4)3(OH)) through adsorption, ion exchange (x = 0.01~0.04), and dissolution-coprecipitation (x = 0.13~0.35) was the dominant process for the Cu (II) removal by the SC–HA/C composite. [ABSTRACT FROM AUTHOR]

A study is performed of the biogenic crystallization (adsorption and desorption) of amino acids on surfaces of hydroxylapatite. The effect the solution pH and the structure of the amino acid have on the maximum adsorption and desorption of a number of amino acids is revealed. Orders of amino acids with respect to adsorption and desorption from the hydroxylapatite surface are determined. A mechanism of amino acid–hydroxylapatite surface interaction is proposed. The mechanism is determined by the surface charge of the solid phase and the amino acid structure and has an electrostatic pattern. It is found that desorption from a hydroxylapatite surface reaches its limit value at a pH near the isoelectric point of the amino acid. [ABSTRACT FROM AUTHOR]

A hydroxylapatite bagasse biochar composite was prepared via the hydrothermal chemical precipitation method with bagasse as the primary raw material. The adsorption capacity of hydroxylapatite bagasse biochar composite for Pb(II) was determined using a series of batch adsorption experiments. The results showed that the point of zero charge value was near neutral pH, and the optimal pH ranged from 4.0 to 7.0. Langmuir isotherms were suitable for fitting the isothermal adsorption process of Pb(II) by the hydroxylapatite bagasse biochar composite. The maximum adsorption capacity of hydroxylapatite bagasse biochar composite in terms of Pb(II) was 210 mg·g -1 at 25 °C. Fourier transform infrared spectrometry analysis indicated that oxygen-containing functional groups were abundant on the external and internal surfaces of the composite sample, which provided numerous chemical sorption sites and resulted in an increase in the adsorption capacity of the composite sample. The Pb(II) removal mechanism of the hydroxylapatite bagasse biochar composite primarily utilized surface diffusion, electrostatic attraction, surface complexation, ion exchange, and a dissolving-coprecipitation reaction. The composite sample was suitable for the treatment of leadcontaminated water (containing zinc, arsenic, cadmium, etc.), which was a promising environmentally friendly material. [ABSTRACT FROM AUTHOR]

Removal of copper ions from aqueous solutions on synthetic and dentine waste hydroxyapatites (HAP) was investigated in batch sorption experiments. Kinetics of sorption followed a pseudo-first order model. Steady-state data show agreement with the Sips isotherm compared with Freundlich and Langmuir models. The higher surface area and carbonated nature of synthetic hydroxyapatite were not sufficient to reach higher sorption capacity than natural one. Ion-exchange and precipitation contributed on removal of Copper despite level ionization of hydroxyapatites. Proton and metal exchanges with copper ions contributed to process of sorption with prevalence of proton-exchange at low copper ion concentrations. High temperatures promoted the removal efficiency of Cu(II) onto the natural and synthesised hydroxyapatites. The thermodynamic parameters showed that sorption process was spontaneous, endothermic and associated entropy at the solid/solution interface increased at high temperatures.

In this study, we analyzed a tooth sample of a renal patient using wavelength-dispersive X-ray fluorescence (WDXRF) spectrometry and Fourier transform infrared (FT-IR) spectrometry to quantify major and trace elements, and heavy and toxic elements in particular. The elements detected and quantified in the tooth sample were calcium (Ca), phosphorus (P), carbon (C), oxygen (O), magnesium (Mg), sodium (Na), chlorine (Cl), sulfur (S), potassium (K), silicon (Si), iron (Fe), aluminum (Al), zinc (Zn), strontium (Sr), chromium (Cr), nickel (Ni), copper (Cu), and zirconium (Zr). FT-IR spectrometry has been used to extract relevant information about the molecular contents of the tooth sample. We have compared our results with those obtained in the laboratory for the healthy subjects, and also with the values reported in the literature as obtained using XRF spectrometry only. Elements found in the tooth sample were correlated with the chronic kidney disease (CKD) of the patients. An outline of the XRF apparatus and applications of XRF as a tool for analyzing to dental specimens are also briefly highlighted., Calcified tissues, such as bones and teeth, contain biological signatures from their living phase. The habitat and nutritional and environmental conditions of people can be determined by monitoring the trace [...]

The mineral components of powdered samples of cortical dense bone tissue of domestic animals (pig and cow) were studied by electron paramagnetic resonance (EPR). Bone tissue was heated in a temperature range 600-1000 ºС in an oven and then held for more than one year at room temperature. This was done to allow short-lived defects to decay and to let the mineral structures stabilize. In these heat-treated samples, within the limits of the sensitivity of the experiments, no EPR signals were detected, but after irradiation with X-rays, multicomponent EPR signals appeared. Spectra vary depending on the heating temperatures. Paramagnetic centers related to PO3 2–, NO4 2– ³- groups are observed. The g-factor of spectroscopic splitting and amplitude of ultrafine interaction of the indicated paramagnetic centers in the spectra were determined. Due to different relaxation behavior of the paramagnetic centers, and hence their saturation effects, the form of the total EPR signals significantly depends on the microwave power level at which the spectra are recorded. Therefore, EPR signals were recorded at high (5 mW) and low (0.13 mW) microwave power levels. The temperature dependency of EPR signal amplitude was determined for some paramagnetic centers in the range of 600-1000 ºС. The EPR signal properties of the heated bone samples and synthetic hydroxylapatites were compared. The spectra indicate that phosphates in bone tissue have a more complex structure than simple synthetic hydroxylapatite. The results of this work can be used to create synthetic analogs of bone tissue, to help in the manufacturing of implants that are used to treat bone tissue, and to study the processes related to the assimilation of mineralogic-based implants by living bone tissue. [ABSTRACT FROM AUTHOR]2 –, CO3 ³- groups are observed. The g-factor of spectroscopic splitting and amplitude of ultrafine interaction of the indicated paramagnetic centers in the spectra were determined. Due to different relaxation behavior of the paramagnetic centers, and hence their saturation effects, the form of the total EPR signals significantly depends on the microwave power level at which the spectra are recorded. Therefore, EPR signals were recorded at high (5 mW) and low (0.13 mW) microwave power levels. The temperature dependency of EPR signal amplitude was determined for some paramagnetic centers in the range of 600-1000 ºС. The EPR signal properties of the heated bone samples and synthetic hydroxylapatites were compared. The spectra indicate that phosphates in bone tissue have a more complex structure than simple synthetic hydroxylapatite. The results of this work can be used to create synthetic analogs of bone tissue, to help in the manufacturing of implants that are used to treat bone tissue, and to study the processes related to the assimilation of mineralogic-based implants by living bone tissue. [ABSTRACT FROM AUTHOR]

Calcification within breast cancer is a diagnostically significant radiological feature that generally consists of hydroxylapatite. Samples from 30 cases of breast carcinoma with calcification were investigated using optical microscopy, energy-dispersive X-ray analysis, transmission-electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, synchrotron radiation X-ray diffraction and X-ray fluorescence. Under optical microscopy, the calcifications were found to consist of either irregular aggregates with widths > 200 μm or spherical aggregates similar to psammoma bodies with an average diameter of 30 μm. Transmission-electron microscopy showed that short columnar or dumbbell-shaped crystals with widths of 10–15 nm and lengths of 20–50 nm were the most common morphology; spherical aggregates (~1 μm in diameter) with amorphous coatings of fibrous nanocrystals were also observed. Results indicated that hydroxylapatite was the dominant mineral phase in the calcifications, and both CO32– and cation substitutions (Na, Mg, Zn, Fe, Sr, Cu and Mn) were present in the hydroxylapatite structure. Fourier-transform infrared spectra show peaks at 872 and 880 cm–1 indicating that CO32– substituted both the OH– (A type) and PO43– (B type) sites of hydroxylapatite, making it an A and B mixed type. The ratio of B- to A-type substitution was estimated in the range of 1.1–18.7 from the ratio of peak intensities (I872/I880), accompanied with CO32– contents from 1.1% to 14.5%. Trace arsenic, detected in situ by synchrotron radiation X-ray fluorescence was found to be distributed uniformly in the calcifications in the form of AsO43– substituting for PO43–. It is therefore proposed that identifying these trace elements in breast cancer calcifications may be promising for future clinical diagnostics. [ABSTRACT FROM AUTHOR]

Silicone rubber (SR) has extensively been used for different industrial and biomedical applications, in view of its good elasticity, chemical inertness, and biocompatibility. However, cure inhibition features, poor mechanical properties, and hydrophobicity, often, limit the possible expansion of its spectrum of applications. The present work has been designed to address these issues by embedding a potential biocompatible filler, nano‐hydroxylapatite (n‐HA), within the SR matrix, through compression molding. The n‐HA particles were initially synthesized by a wet chemical method, and were subsequently introduced into SR quantitatively. The rheological features, compressive properties, simulated body fluid (SBF) uptake, bovine serum albumin (BSA) adsorption, blood compatibility, and cytocompatibility of n‐HA modified SR systems have been investigated. The change in rheological characteristics after n‐HA embedding within SR clearly indicated the favorable interactions between them, and a compatible functional existence under external stresses. The compressive strength, which is critical for the different applications of SR, has been found to be increased with an increase in n‐HA loading. In‐vitro mineralization studies using SBF showed the formation of apatite crystals on the surface of SR/n‐HA system indicating its biocompatibility. This has been confirmed by SEM and FTIR examinations. It has further been observed that the addition of n‐HA particles into SR matrix enhances the protein adsorption characteristics. The n‐HA embedded system exhibited excellent blood compatibility, which has been complemented through hemolysis (%) studies and thrombogenicity assay. The results indicate that the strategy of n‐HA embedding would do significant value addition to SR, and widen its scope in the industrial and biomedical sectors. [ABSTRACT FROM AUTHOR]

Porous hydroxyapatite-biochar composites with layered microstructures (SC–HA/C) were prepared by carbonizing sugarcane stem nodes and then soaking them in lime water and (NH4)2HPO4 solutions in rotation. The surface area of SC–HA/C ranges from 8.52 to 28.44 m2/g, and its microstructure inherits various macro-, meso-, and micro-pores in the cell walls of sugarcane and in the pits of the vessel walls. The maximum removal capacities were 11.50, 14.65, and 19.81 mg/g for the Cu (II) immobilization at 25 °C, 35 °C, and 45 °C with the solution Cu (II) concentration of 10~320 mg/L, respectively, which were in accordance with the copper sorption capacities of synthesized nano-hydroxylapatites. The Cu (II)-removal kinetics and isotherm followed the pseudo-second-order equation and the Langmuir equation very well. The formation of the Cu-containing hydroxylapatite solid solutions ((CuxCa1−x)5(PO4)3(OH)) through adsorption, ion exchange (x = 0.01~0.04), and dissolution-coprecipitation (x = 0.13~0.35) was the dominant process for the Cu (II) removal by the SC–HA/C composite.

Copyright of Travma is the property of Zaslavsky O.Yu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Večerná-Čárka cave system is the longest underground site of the Kuchyňa-Orešany Karst (Malé Karpaty Mountains, western Slovakia). Although its length is only 58 m, it is a site of remarkable interest in terms of speleogenesis that was strongly controlled by tectonic structure of the Middle Triassic limestone (Fatric Unit). Morphologically, the studied cave system represents a branched cave, formed by linear, and in some places intersecting passages. Their direction is strongly linked with two systems of steep parallel and crossing tectonic failures of N–S and NW–SE direction. Phreatic morphologies of passages show that the cave system originated by dissolution of limestone along these tectonic discontinuities, in several places the cave passages were enlarged by the destruction of parallel rock partitions. Probably, waters of deeper circulation ascended along steep tectonic fractures. Since these waters were relatively saturated, limestone mostly dissolved in the zone of mixing with seeping rainwater. A dense network of steep parallel and intersecting tectonic fractures allowed to diffuse groundwater circulation without much concentration of water flow into one or more main conduits. The absence of water table notches, ceiling cupolas as well as blind oval chimneys indicate that the caves formed below or just below the former piezometric surface of groundwater and without its significant oscillations, e.g. in the shallow phreatic zone. The estimated Pliocene (or late Pliocene?) age of the cave system (lying at an altitude of 413–419 m asl.) is determined based on its location above the recent hydrographic network (60 m above the floor of the valley) and by the remains of the Plio-Pleistocene planation surface located at 250–350 m asl. in the adjacent part of the Malé Karpaty Mountains. [ABSTRACT FROM AUTHOR]

Pole figures measured using X-ray diffractometry were used to analyze the orientation of crystalline hydroxylapatite (HAP) in the scales and fins of seawater Lateolabrax japonicus. An orientation distribution function (ODF) was calculated based on the pole figures of the lattice planes (002),(130), and (211) of HAP in the scales and those of (031),(120), and (132) in the fins. The pole figures indicate that the c-axis of HAP prefers three primary orientations in the scales and five primary orientations in the fins. In the scales, the preferred orientations of the HAP c-axis are parallel to the normal line of the scale face and intersect the normal line at about 39° and 63°. In the fins, the HAP c-axis intersects the normal line of the cross-section at 3°, 9°, 17°, 24°, and 36°. However, the calculated ODFs show that the preferred orientations of the HAP c-axes are nearly parallel to the face of the scales and perpendicular to the cross-section of the fins. As the pole figure only reflects a two-dimensional projection of the crystalline orientations, the preferred orientations determined by the pole figures are not very accurate. Conversely, three-dimensional ODF is more suitable for analyzing the preferred orientation of biominerals than the two-dimensional projection. The tendency of the c-axis to be parallel to the collagen fibers is controlled by organic matter and provides a good mechanical performance in hard tissue.

Amino acid adsorption on surfaces of brushite and hydroxylapatite (HA) is studied at different solution pH and amino acid concentration values. The synthesis of HA and brushite is conducted; the composition of the solid phases is confirmed by X-ray diffraction, IR spectroscopy, and optical microscopy. The specific surface area of brushite (9.0 m2/g) and HA (72.0 m2/g) is determined by the BET method. The effect of the solution pH on the maximum adsorption of amino acids on brushite and HA is revealed. To determine the adsorption mechanism, the sign of the surface charge of the solid phase of brushite and HA (positive) is determined by capillary analysis. The Gibbs free energy values are calculated. It is assumed that amino acids interact with the surface of brushite and HA in accordance with the physical adsorption mechanism. [ABSTRACT FROM AUTHOR]

Objective: The recently introduced Vector system is recommended to be used in conjunction with a polishing fluid containing hydroxylapatite granules (< 10 μm). The aim of the present study was to assess morphologic alterations of the root surface after ultrasonic treatment with the polishing fluid. Method and Materials: Cementum of 30 freshly extracted human teeth was removed to a level of 4 mm below the cementoenamel junction. Surfaces were root-planed and conditioned with citric acid to remove the smear layer. Teeth were divided into 5 groups, with group 1 as the untreated control. Group 2 was solely treated with the ultrasonic system. In group 3, the ultrasonic system was used in conjunction with the polishing fluid. Group 4 was treated with a medium-hard toothbrush and the polishing fluid. Group 5 was treated only with the toothbrush. Specimens were evaluated by both light and scanning electron microscopy. Results: Dentinal tubules were not covered by a smear layer in the control group, whereas in group 2, a smear layer could be observed in some specimens. In group 3 dentinal tubules were always covered by a layer consisting of granules of about 2 μm. In group 4 all samples showed a layer containing granules of about 5 μm, and in group 5 a thin smear layer could be observed. Conclusion: The use of a polishing fluid containing hydroxylapatite granules during treatment of the root surface results in a granular layer covering the dentinal tubules. This layer may reduce hypersensitivity after ultrasonic subgingival scaling. [ABSTRACT FROM AUTHOR]

Cellulose represents a low cost, abundant, and renewable polysaccharide with great versatility; it has a hierarchical structure composed of nanofibers with high aspect ratio (3–4 nm wide, hundreds of μm long). TEMPO-mediated oxidation represents one of the most diffused methods to obtain cellulose nanofibers (CNFs): It is possible to obtain physically crosslinked hydrogels by means of divalent cation addition. The presence of inorganic components, such as calcium phosphates (CaP), can improve not only their mechanical properties but also the bioactivity of the gels. The aim of this work is to design and characterize a TEMPO-oxidized cellulose nanofibers (TOCNFs) injectable hydrogel embedded with inorganic particles, CaP and CaP-GO, for bone tissue regeneration. Inorganic particles act as physical crosslinkers, as proven by rheological characterization, which reported an increase in mechanical properties. The average load value registered in injection tests was in the range of 1.5–4.4 N, far below 30 N, considered a reasonable injection force upper limit. Samples were stable for up to 28 days and both CaP and CaP-GO accelerate mineralization as suggested by SEM and XRD analysis. No cytotoxic effects were shown on SAOS-2 cells cultured with eluates. This work demonstrated that the physicochemical properties of TOCNFs-based dispersions could be enhanced and modulated through the addition of the inorganic phases, maintaining the injectability and bioactivity of the hydrogels.

In this study, the in vitro biocompatibility and osteoinductive ability of a recently developed biomorphic hydroxylapatite ceramic scaffold (B-HA) derived from transformation of wood structures were analyzed using human adipose stem cells (hASCs). Cell viability and metabolic activity were evaluated in hASCs, parental cells and in recombinant genetically engineered hASC-eGFP cells expressing the green fluorescence protein. B-HA osteoinductivity properties, such as differentially expressed genes (DEG) involved in the skeletal development pathway, osteocalcin (OCN) protein expression and mineral matrix deposition in hASCs, were evaluated. In vitro induction of osteoblastic genes, such as Alkaline phosphatase (ALPL), Bone gamma-carboxyglutamate (gla) protein (BGLAP), SMAD family member 3 (SMAD3), Sp7 transcription factor (SP7) and Transforming growth factor, beta 3 (TGFB3) and Tumor necrosis factor (ligand) superfamily, member 11 (TNFSF11)/Receptor activator of NF-κB (RANK) ligand (RANKL), involved in osteoclast differentiation, was undertaken in cells grown on B-HA. Chondrogenic transcription factor SRY (sex determining region Y)-box 9 (SOX9), tested up-regulated in hASCs grown on the B-HA scaffold. Gene expression enhancement in the skeletal development pathway was detected in hASCs using B-HA compared to sintered hydroxylapatite (S-HA). OCN protein expression and calcium deposition were increased in hASCs grown on B-HA in comparison with the control. This study demonstrates the biocompatibility of the novel biomorphic B-HA scaffold and its potential use in osteogenic differentiation for hASCs. Our data highlight the relevance of B-HA for bone regeneration purposes.

Hard tissues (e.g., bone, enamel, dentin) in vertebrates perform various and different functions, from sustaining the body to haematopoiesis. Such complex and hierarchal tissue is actually a material composite whose static and dynamic properties are controlled by the subtle physical and chemical interplay between its components, collagen (main organic part) and hydroxylapatite-like mineral. The knowledge needed to fully understand the properties of bony and dental tissues and to develop specific applicative biomaterials (e.g., fillers, prosthetics, scaffolds, implants, etc.) resides mostly at the atomic scale. Among the different methods to obtains such detailed information, atomistic computer simulations (in silico) have proven to be both corroborative and predictive tools in this subject. The authors have intensively worked on quantum mechanical simulations of bioapatite and the present work reports a detailed review addressed to the crystal-chemical, physical, spectroscopic, mechanical, and surface properties of the mineral phase of bone and dental tissues. The reviewed studies were conducted at different length and time scales, trying to understand the features of hydroxylapatite and biological apatite models alone and/or in interaction with simplified collagen-like models. The reported review shows the capability of the computational approach in dealing with complex biological physicochemical systems, providing accurate results that increase the overall knowledge of hard tissue science.

In order to understand the processes of stone formation, compositional, spectroscopic, mineralogical and crystallographic characteristics of human urinary stones collected from patients in Sri Lanka were investigated in detail. The data showed that the majority of urinary calculi were calcium oxalate, either whewellite or weddellite. Other solid phases of stones were composed of struvite, uricite and hydroxylapatite. However, mixed compositions were common except for whewellite stones which occur frequently in pure form. Scanning electron microscope observations and associated energy-dispersive X-ray analyses revealed that whewellite or weddellite was well crystalized compared to other stones types, while phosphate stones were mostly cryptocrystalline. The average δ13C and δ18O of stones were − 32.2‰ (− 37.3 to − 17.4‰) and − 24.2‰ (− 26.7‰ to − 8.9‰), respectively. The δ13C values were highly depleted compared to North American and European urinary stones. This may be due to food habits of Asians who consume rice as the staple food. [ABSTRACT FROM AUTHOR]

Adsorbed and structurally incorporated carbonate in bioapatite, the primary mineral phase of bone, is observed across vertebrates, typically at 2–8 wt%, and supports critical physiological and biochemical functions. Several turtle species contain elevated bone-associated carbonate, a property linked to pH buffering and overwintering survival. Prior studies of turtle bone utilized bulk analyses, which do not provide spatial resolution of carbonate. Using Raman spectroscopy, the goals of this study were to: (1) quantify and spatially resolve carbonate heterogeneity within the turtle shell; (2) determine if cortical and trabecular bone contain distinct carbonate concentrations; and (3) assess if simulated overwintering conditions result in decreased bioapatite carbonation. Here, we demonstrate the potential for Raman spectroscopic analysis to spatially resolve bioapatite carbonation, using the western painted turtle as a model species. Carbonate concentration was highly variable within cortical and trabecular bone, based on calibrated Raman spot analyses and mapping, suggesting heterogeneous carbonate distribution among crystallites. Mean carbonate concentration did not significantly differ between cortical and trabecular bone, which indicates random distribution of crystallites with elevated and depleted carbonate. Carbonate concentrations (range: 5–22 wt%) were not significantly different in overwintering and control animals, deviating from previous bulk analyses. In reconciling bulk and Raman analyses, two hypotheses explain how overwintering turtles potentially access carbonate: (1) mobilization of mineral-associated, surface components of bone crystallites; and (2) selective, dispersed crystallite dissolution. Elevated bioapatite carbonate in the western painted turtle, averaging 11.8 wt%, represents the highest carbonation observed in vertebrates, and is one physiological trait that facilitates overwintering survival. • Raman mapping facilitates spatially-resolved carbonate quantification in bone • Turtle shell cortical & trabecular bone contain elevated carbonate sources • Maximum value & range of bone-associated carbonate not decreased after anoxia • Bone carbonate source(s): adsorbed; dispersed crystallites; isolated bone areas [ABSTRACT FROM AUTHOR]

Abstract Apatite subspecies depend on their halogen and hydroxyl content; chlorapatite, hydroxylapatite and fluorapatite, with additional substitution of other elements within the lattice such as rare earth elements (REE), sodium, strontium and manganese also possible. Rare earth elements are vital to green and emerging technologies, with demand set to outstrip supply. Apatite provides a possible future source of REE. Processing rare earth deposits is often complex, with surface behaviour having a significant effect on the optimization of a process flow sheet. The effect of enrichment of natural apatite and the doping of synthetic apatite on surface behaviour can be determined by measuring the zeta potential and the isoelectric point of the mineral. In this paper, we review zeta potential studies of natural and synthetic apatite to determine the effect of elemental enrichment on surface behaviour. Fifty three studies of natural apatite and forty four studies of synthetic apatite were reviewed. The isoelectric point of apatite varied from pH 1 to pH 8.7, with studies of apatite specified to be >90% pure reducing the variation to pH 3 to pH 6.5. Of the four studies of rare earth enriched apatite found, three had IEP values between pH 3 and pH 4. A study of synthetic apatite showing enrichment of between 1 and 10% by the REE europium does not affect surface behaviour. However, no studies were found that investigated the effect of common REE processing reagents on REE enriched apatite zeta potentials. Therefore, in addition to comparing previous studies we also therefore present new zeta potential measurements of apatite from a REE enriched deposit under water and common flotation collector conditions. The IEP value of this apatite under water conditions was at pH 3.6, shifting to <3.5 under both hydroxamic acid and betacol conditions. When compared to previous studies, the behaviour of REE enriched apatite under collector conditions is similar to non-REE apatite. This result could be important for future processing of apatite enriched with REE, and therefore global apatite and rare earth supply. Graphical abstract Unlabelled Image Highlights • The iso electric point of natural apatite ranged from pH 1 to pH 8.7. • The iso electric point of synthetic apatite ranged from pH 3 to pH 8.1. • Chlorapatite had a higher zeta potential than hydroxyapatite in apatite. • Zeta potential measurement of apatite from REE enriched deposit give IEP of 3.6. • REE enriched apatite can be processed similarly to non REE enriched apatite. [ABSTRACT FROM AUTHOR]

The stalk internodes of sugarcane tops were used as the biotemplate to prepare a hydroxylapatite-carbon adsorbent with the hierarchical porous microstructure of sugarcane stalks (HAP/C-SS). The HAP/ C-SS adsorbent retained the porous microstructure of sugarcane top stalks, which essentially consisted of micropores, mesopores and macropores originating from the cavities of vessels, parenchyma cells, sclerenchyma cells and pits. The specific surface area was estimated to be 8.52–28.44 m²/g by the Brunauer–Emmett–Teller method and 5.63 m²/g by the mercury porosimetry method. The HAP/C-SS showed an excellent removal performance for Cd(II) ions. The removal capacities were determined to be 10.89, 18.00 and 51.93 mg/g for the adsorption at the initial Cd(II) concentrations of 10, 20 and 50 mg/L, respectively, which were comparable with the adsorption capacities of the synthetic hydroxylapatite nanoparticles. The pseudo-second-order kinetic model and the Langmuir isotherm could very well fit the experimental data. The formation of the (CdxCa1‒x)5(PO4)3(OH) solid solution through the coexisting ion exchange and dissolution–precipitation (x = 0.03–0.17) processes was the main mechanism for the Cd(II) adsorption onto the HAP/C-SS adsorbent. [ABSTRACT FROM AUTHOR]

The atomic arrangements of eight synthetic samples along the fluorapatite-hydroxylapatite join were examined using X‑ray crystallographic techniques; the results of those refinements demonstrate that the incorporation of both F and OH in the apatite anion column, mimicking the human apatite system as modified by fluoridation, is complex. The compositions of the anion columns in the phases ranged from [F0.40(OH)0.60] to [F0.67(OH)0.33], and the high-precision structure refinements yielded R1 values from 0.0116 to 0.0140. The apatite structure responds to the variable content of the anion columns. Counterintuitively, the OH groups in the anion column move monotonically closer to the mirror planes at z = 1⁄4, 3⁄4 with increasing F content, despite the decreasing size of the triangle of Ca2 atoms to which the column anions bond and the increasing overbonding of the hydroxyl oxygen. In the structure the F atoms are underbonded and have zero degrees of positional freedom in the (0,0,1⁄4) special position to relieve that underbonding; the bonding deficiency of the anion column is relieved by the overbonding of the O(H) atom in the anion column, overbonding that increases with increasing content of underbonded F in the anion column. Together the underbonded F and the overbonded OH meet the formal bond valence (1.0 v.u.) required by the anion column occupants. The changes in bonding from the individual anion column occupants to the surrounding Ca2 atoms with composition induce bond length changes principally in the irregular Ca2 polyhedron and also affect the a lattice parameter in the apatites. The bond valence values imparted on the F, OH column anions, when extrapolated to end-member compositions, suggest that different column anion arrangements may exist near the F and OH end-member compositions, as is also seen along the apatite Cl-OH join. These values have implications for the incorporation of fluoride in human teeth during the fluoridation process. [ABSTRACT FROM AUTHOR]

Streptococcus pneumoniae is a major pathogen that causes life-threatening diseases, such as pneumonia, otitis media, bacteremia, and meningitis, worldwide and especially in young children and the elderly. Pneumococcal surface protein A (PspA) is a widely studied candidate protein vaccine that represents a promising replacement for current polysaccharide and polysaccharide-conjugate vaccines. In this study, we describe a simple method to produce PspA of clade 4 from an Escherichia coli expression system using hydroxylapatite and ion-exchange chromatography. Using this method, we successfully expressed soluble PspA4 in 10 L of autoinducing culture medium, with a wet-cell yield of 19 g/L and a final PspA4 concentration of 22.8 mg/L. Additionally, we improved PspA4 purity from 17% to 70% in a single step through the use of hydroxylapatite, resulting in acquisition of recombinant PspA4 (>95% purity) at a final yield of 43% from the starting cell-lysis solution. We subsequently verified the secondary structure molecular weight of recombinant PspA4 by circular dichroism and mass spectrometry, respectively. These results demonstrated a highly efficient method for mass producing PspA4 protein and that can also be applied for purification of PspA proteins from other clades. [ABSTRACT FROM AUTHOR]

Threaded hydroxylapatite-coated implants of commercially pure (CP) titanium were inserted in the rabbit tibial metaphysis. Uncoated CP titanium screw implants inserted in the contralateral leg served as controls. After 6 weeks and 1 year postinsertion, the semiloaded implants were histomorphometrically analyzed. While not significant, there was more direct bony contact with the hydroxylapatite-coated implants after 6 weeks of follow-up. One year after insertion, there was significantly more direct bone-to-implant contact with the uncoated CP titanium controls. [ABSTRACT FROM AUTHOR]