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Since bone apatite is a carbonate apatite containing carbonate in an apatitic structure, carbonate content may be one of the factors governing the osteoconductivity of apatitic bone substitutes. The aim of this study was to evaluate the effects of carbonate content on the osteoconductivity of apatitic bone substitutes using three commercially available bone substitutes for the reconstruction of alveolar bone defects of a beagle mandible with simultaneous dental implant installation. NEOBONE, Bio-Oss, and Cytrans that contain 0.1, 5.5, and 12.0 mass% of carbonate, respectively, were used in this study. The amount of newly formed bone in the upper portion of the alveolar bone defect of the beagle's mandible was 0.7, 6.6, and 39.4% at 4 weeks after surgery and 4.7, 39.5, and 75.2% at 12 weeks after surgery for NEOBONE, Bio-Oss, and Cytrans, respectively. The results indicate that bone-to-implant contact ratio was the largest for Cytrans. Additionally, the continuity of the alveolar ridge was restored in the case of Cytrans, whereas the continuity of the alveolar ridge was not sufficient when using NEOBONE and Bio-Oss. Both Cytrans and Bio-Oss that have a relatively larger carbonate content in their apatitic structure was resorbed with time. We concluded that carbonate content is one of important factors governing the osteoconductivity of apatitic bone substitutes., (© 2019 Wiley Periodicals, Inc.)

Among the various bone substitutes, carbonate apatite (CO3Ap) has received significant attention in the field of hard tissue regeneration due to its similarity in chemical composition to natural bone and its osteoconductivity and bioresorbability. This study aimed to develop a cost-effective method for fabricating porous CO3Ap blocks while maintaining a balance between porosity and mechanical properties. The level of interconnectivity in the porous structure was achieved by adjusting the pore volume fractions of the starting materials. The phase and microstructure characteristics of the porous CO3Ap blocks were assessed using techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The diametral tensile strength (DTS) of the blocks was determined using a universal testing machine. The results demonstrated that the mechanical strength of the blocks stayed within a range that was suitable for handling properties. This advantage allows the porous blocks to withstand initial stress during implantation procedures or in the early stages of defect healing. [ABSTRACT FROM AUTHOR]

Carbonate apatite (CA) is a synthetic derivative of hydroxyapatite, which we have been exploring as a drug delivery nanocarrier in the context of cancer in vitro and in vivo. This nanocarrier showed great potential delivering anti-cancer drugs, plasmids containing tumour suppressor genes and siRNAs against oncogenes in pre-clinical models. We compared here two formulations of CA—the low-Ca2+ CA (made with 4 mM Ca2+) used for in vitro studies in cell lines and the high-Ca2+ CA (made with 40 mM Ca2+) used in mouse models—in terms of protein corona formed with different concentrations of serum in vivo and in vitro. The 10-fold more Ca2+ in high-Ca2+ CA helped produce enough particles in an injectable volume for in vivo delivery of therapeutics. Both formulations made particles of similar size, but their composition differed slightly in terms of Na and Mg content. In serum-containing media, the size of the particles was dependent on the serum concentration. The protein corona around both formulations was almost similar and included albumin, fetuin, haemoglobin, and immunoglobulins. CA was not cytotoxic, and instead an increased expression of ribosomal machinery and glycolytic and cytoskeletal proteins was observed, which promoted translation, growth, and proliferation in cancer cells. [ABSTRACT FROM AUTHOR]

The rate of resorption of calcium phosphate self-hardening materials for bone regeneration can be changed by changing the phase composition. The Ca3(PO4)2/CaCO3/Ca(H2PO4)2·H2O/Na2HPO4·12H2O system is important for the synthesis of self-curing bioactive materials with variable resorption rates by changing the ratios of the initial components. Cement compositions in twelve figurative points of a four-component composition diagram at a fixed content in the α-Ca3(PO4)2 system were studied with XRD, FTIR, SEM, calorimetric, and volumetric methods to obtain an idea of the effect of composition on solubility in vitro and resorption in vivo. It was found that the presence of the highly resorbable phase of dicalcium phosphate dihydrate in cement and the substitution of phosphate ions with the carbonate ions of hydroxyapatite increased solubility in vitro and resorption in vivo. The obtained results confirm the possibility of changing the solubility of a final product in the Ca3(PO4)2/CaCO3/Ca(H2PO4)2·H2O/Na2HPO4·12H2O system by changing the ratio of the initial components. [ABSTRACT FROM AUTHOR]

The environment model is used to describe the location of carbonate in nine carbonated apatites containing varied percentages of carbonate and Na+, K+, or NH4+ ions. Unlike the traditional model for carbonate substitution, which identifies different locations and orientations of the carbonate ion in the apatite structure, the environment model utilizes the different structural surroundings to describe the different types of carbonate. The A-type carbonate environment is assigned to channels lined only with calcium ions (A-channel configuration = Ca6) or to channels containing one Na+ or a vacancy (A′-channel configuration = Ca5Na or Ca5▢), and the B-type carbonate environment is the surroundings of the replaced phosphate ion. The assignments are made by peak-fitting the carbonate asymmetric stretch region (ν3) of the IR spectrum, following previously published criteria. These assignments lead to the conclusion that the percentage of channel carbonate (A- and A′-environments) is greater than that of B-type for each of these carbonated apatites. In general, the use of triammonium phosphate as the phosphate source in the synthesis produces apatites with larger amounts of channel carbonate (A- and A′-environments), while the use of sodium-containing phosphate reagents produces smaller amounts of channel carbonate. The environment model provides explanations for the differences within IR and NMR spectra obtained for apatites containing a range of total carbonate content. The B-type appearance of the carbonate ν3 region of the IR spectrum is found primarily in apatites containing sodium, which allows increased amounts of carbonation via co-substitution of Na+ with carbonate and creation of A′-environments with populations equal to that of B-type carbonate. The presence of ammonium or alkali metal salts with cations larger than Na+ results in the utilization of a charge-balance mechanism that produces vacancies rather than cation substitution in the channel. The carbonated apatites formed with primary utilization of the vacancy mechanism generally contain greater percentages of carbonate in the A-environment and carbonate IR spectra that contain an obvious high-frequency peak at about 1550 cm–1. The multiple peaks in the solid state 13C NMR spectra previously observed for carbonated apatite are attributed to substitution in the A-, A′-, and B-environments rather than different stereo-chemical orientations of the carbonate ion. [ABSTRACT FROM AUTHOR]

Carbonated apatite is the inorganic component of natural bone while the carbonate ion in the structure influences biological activities and osteoconductivity. However, thermal stability of carbonate apatite is a major importance since thermal stability of carbonate apatite is a function of carbonate content presented in the structure and heat treatment atmosphere. This research work investigates the effects of different carbonate contents on carbonate substitution, thermal stability, physical and mechanical properties of carbonate apatite synthesized by a precipitation method. The results indicated that the carbonate content influenced the properties of carbonated apatite powders. High carbonate substitution (10-11 wt.%) promoted the decomposition of carbonated apatite after heat treatment at 900 °C while a low amount of carbonate substitution (approx. 2 wt.%) resulted in the relocation of carbonate group from phosphate site to hydroxyl site without decomposition. It also demonstrated that a high carbonate amount resulted in a superior mechanical performance. Dense carbonated apatite with high carbonate content has achieved a relative density of 97% and a maximum fracture toughness of 1.4 MPa•m1/2. In the contrary, low carbonate content resulted in a compact with high porosity of about 40% and a low toughness value of 0.35 MPa·m1/2 when treatment at 900 °C. [ABSTRACT FROM AUTHOR]

We have developed an autologous transplantation method using adipose tissue-derived multi-lineage progenitor cells (ADMPCs) as a method of periodontal tissue regeneration that can be adapted to severe periodontal disease. Our previous clinical study confirmed the safety of autologous transplantation of ADMPCs and demonstrated its usefulness in the treatment of severe periodontal disease. However, in the same clinical study, we found that the fibrin gel used as the scaffold material might have caused gingival recession and impaired tissue regeneration in some patients. Carbonate apatite has a high spacemaking capacity and has been approved in Japan for periodontal tissue regeneration. In this study, we selected carbonate apatite as a candidate scaffold material for ADMPCs and conducted an in vitro examination of its effect on the cellular function of ADMPCs. We further performed autologous ADMPC transplantation with carbonate apatite as the scaffold material in a model of one-wall bone defects in beagles and then analyzed the effect on periodontal tissue regeneration. The findings showed that carbonate apatite did not affect the cell morphology of ADMPCs and that it promoted proliferation. Moreover, no effect on secretor factor transcription was found. The results of the in vivo analysis confirmed the space-making capacity of carbonate apatite, and the acquisition of significant new attachment was observed in the group involving ADMPC transplantation with carbonate apatite compared with the group involving carbonate apatite application alone. Our results demonstrate the usefulness of carbonate apatite as a scaffold material for ADMPC transplantation. [ABSTRACT FROM AUTHOR]

Carbonate apatite (CO3Ap) granules are useful as a bone substitute because they can be remodeled to new natural bone in a manner that conforms to the bone remodeling process. However, reconstructing large bone defects using CO3Ap granules is difficult because of their granular shape. Therefore, we fabricated CO3Ap honeycomb blocks (HCBs) with continuous unidirectional pores. We aimed to elucidate the tissue response and availability of CO3Ap HCBs in the reconstruction of rabbit mandibular bone defects after marginal mandibulectomy. The percentages of the remaining CO3Ap area and calcified bone area (newly formed bone) were estimated from the histological images. CO3Ap area was 49.1 ± 4.9%, 30.3 ± 3.5%, and 25.5 ± 8.8%, whereas newly formed bone area was 3.0 ± 0.6%, 24.3 ± 3.3%, and 34.7 ± 4.8% at 4, 8, and 12 weeks, respectively, after implantation. Thus, CO3Ap HCBs were gradually resorbed and replaced by new bone. The newly formed bone penetrated most of the pores in the CO3Ap HCBs at 12 weeks after implantation. By contrast, the granulation tissue scarcely invaded the CO3Ap HCBs. Some osteoclasts invaded the wall of CO3Ap HCBs, making resorption pits. Furthermore, many osteoblasts were found on the newly formed bone, indicating ongoing bone remodeling. Blood vessels were also formed inside most of the pores in the CO3Ap HCBs. These findings suggest that CO3Ap HCBs have good osteoconductivity and can be used for the reconstruction of large mandibular bone defects. [ABSTRACT FROM AUTHOR]

Carbonate apatite (CO3Ap) is an inorganic component of bone and replaces by natural bone after implantation into the bone defect. Because of this unique characteristic, CO3Ap granules have been used in the dental field. However, washing out of granules from the bone defect area is an issue. The aim of this study was to set CO3Ap granules by mixing CO3Ap granules with acidic phosphate solutions and evaluate the influence of the pH and ion components of the solutions. When Na+ was the counter ion, the amount of precipitated dicalcium phosphate dihydrate (DCPD) was small and the setting ability disappeared with increasing pH of the solutions. Alternatively, when the counter ion was Ca2+, the amount of precipitated DCPD was high and the setting ability was observed even at high pH. These results suggest the presence of Ca2+ in the acidic phosphate solution is a key for fabricating CO3Ap granular cement. [ABSTRACT FROM AUTHOR]

Granular-shaped carbonate apatite (CO 3 Ap) bone substitute has demonstrated good clinical results, especially in the bone augmentation procedure, because it has high osteoconductivity and can be replaced by a new bone. This study aimed to evaluate the potential usefulness of CO 3 Ap bone substitute for alveolar ridge preservation of beagle dogs during the 9-week follow-up period after surgery. Reconstruction of extraction sockets with CO 3 Ap granules (CO 3 Ap group) allowed approximately 1.0 mm higher alveolar bone height than that with a blood clot (control group) at 4 and 9 weeks after surgery. Additionally, the measured area at the buccal aspect of the alveolar bone in the CO 3 Ap group was approximately 2 mm2 larger than that in the control group at 4 and 9 weeks after surgery. Continuity from the buccal side to palatal side of the alveolar bone was restored, maintaining its contour at 4 weeks after surgery. The amount of bony tissue, especially the amount of mature bone, in the alveolar part was statistically larger than that of control group at 9 weeks after surgery even though complete replacement of CO 3 Ap granules with new bone was not observed within 9 weeks. In conclusion, CO 3 Ap granules have good potential for alveolar ridge preservation. [ABSTRACT FROM AUTHOR]

Carbonate apatite (CO 3 Ap) artificial bone has attracted much attention due to its high osteoconductivity and replacement to bone. CO 3 Ap is an inorganic component of bone, and has been fabricated by compositional transformation through a dissolution–precipitation reaction in Na 2 HPO 4 solution using calcium carbonate as a precursor. In this study, the effects of the CO 3 2− concentration in the Na 2 HPO 4 solution on the CO 3 Ap fabrication reaction and the properties of the fabricated CO 3 Ap were investigated. The rate of the compositional transformation became faster, and more CO 3 containing CO 3 Ap was fabricated using CO 3 2− concentrated in Na 2 HPO 4 solution. The crystal shape of CO 3 Ap changed from scale-like to hexagonal crystals. In addition, the crystallite size increased with increasing CO 3 2− concentration in the Na 2 HPO 4 solution. These changes lead to larger pores (≥0.02 μm) and decreased number of small pores (<0.02 μm) according to the CO 3 content in CO 3 Ap, even though the total pore volume remained the same. These findings indicate that the CO 3 2− concentration in Na 2 HPO 4 solution is an important factor for the CO 3 Ap fabrication reaction and affects the properties of the fabricated CO 3 Ap. [ABSTRACT FROM AUTHOR]

Interconnected porous carbonate apatite (CO 3 Ap) blocks that emulate cancellous bone have potential as an alternative to autografts. The present study aimed to evaluate the feasibility of fabricating a block via a stepwise compositional transformation to CO 3 Ap through dissolution-precipitation reactions of an interconnected porous calcium sulfate dihydrate (CSD) block, which was obtained by the setting reaction of calcium sulfate hemihydrate (CSH) granules. Exposure of the CSH granules to water resulted in a setting reaction. However, the gaps between the granules were clogged, preventing the fabrication of interconnected porous structures. Removing the water in the gaps using filter paper was beneficial in avoiding gap clogging and in fabricating interconnected porous CSD blocks. Although the CSD blocks transformed into CaCO 3 blocks, which maintained the interconnected porous structure through a dissolution-precipitation reaction in a Na 2 CO 3 solution, their mechanical strength was quite low (diametral tensile strength: DTS = 75 kPa). In contrast, a CaCO 3 block with a much greater mechanical strength (DTS = 0.98 MPa) was fabricated when a calcium sulfate anhydrous block made via the heat treatment of the CSD block was used as a precursor. The CaCO 3 block transformed into a CO 3 Ap block (DTS = 2.1 MPa), maintaining the interconnected porous structure through a dissolution-precipitation reaction when immersed in a Na 2 HPO 4 solution. The CO 3 Ap block had macropores initiated by the gaps between the granules and micropores created by the setting reaction of CSH granules and the dissolution-precipitation reactions to form CO 3 Ap. The results obtained in the present study demonstrate that this method is useful for fabricating interconnected porous CO 3 Ap blocks. [ABSTRACT FROM AUTHOR]

Titanium (Ti) implants that realize rapid osseointegration are required for favorable outcomes. Rough implant surfaces favor osseointegration, hence, coating implants with natural bone mineral, i.e., carbonate apatite (CO3Ap), may be effective for osseointegration. To achieve rapid osseointegration, rough‐Ti substrates are coated with CO3Ap (CO3Ap‐Ti) and the effects are evaluated in vitro and in vivo. For comparison, rough‐Ti without coating (rough‐Ti) and calcite‐coated rough‐Ti (calcite‐Ti) substrates are fabricated. The adhesive strengths of calcite and CO3Ap to the substrates are ≈56.6 and ≈76.8 MPa, respectively, being significantly higher than the strength defined in ISO13779‐2 (15 MPa). Calcite and CO3Ap coatings significantly promote preosteoblastic MC3T3‐E1 cell proliferation. Additionally, the CO3Ap coating promotes higher osteogenic differentiation activity than the calcite coating. Implantation of CO3Ap‐Ti into rabbit tibia defects prompts bone maturation, compared to calcite‐Ti or rough‐Ti implantation. The bone‐implant contact percentage with CO3Ap‐Ti and calcite‐Ti is higher than that with rough‐Ti. Consequently, CO3Ap‐Ti acquires a robust bond with the host bone at an early stage (4 weeks postimplantation), compared to calcite‐Ti or rough‐Ti: the CO3Ap‐Ti–bone bonding strength is ≈1.9‐ and ≈5.5‐fold higher than that of calcite‐Ti and rough‐Ti, respectively. Thus, CO3Ap coating of Ti implants effectively achieve rapid osseointegration. [ABSTRACT FROM AUTHOR]

In scaffolds used for bone regeneration, osteogenic ability increases and mechanical strength decreases with increasing porosity. To ensure both mechanical strength and osteogenesis, an optimal pore architecture is necessary. Porous glass has high porosity and high mechanical strength, as it is framed with a rigid interconnected silica network and void interspaces in the silica network. In this context, based on the porous structure of glass, we fabricated porous blocks composed of carbonate apatite (CO 3 Ap), which is the major component of human bone mineral, with both high mechanical strength and high porosity. To fabricate the CO 3 Ap blocks, first, calcite-polymethyl methacrylate (PMMA) mixture granules were prepared. Next, the calcite-PMMA granules were allowed to join together in the mold by fusing PMMA, resulting in the formation of porous blocks composed of interconnected calcite-PMMA granules. Next, PMMA was thermally removed and the resultant interconnected calcite granules were partially sintered. Finally, the composition of the interconnected granules was converted from calcite to CO 3 Ap in a dissolution-precipitation reaction. Consequently, CO 3 Ap blocks with a continuous pore architecture were successfully fabricated. The porosity and diametral tensile strength were controllable within the range of 60‒70% and 1.0‒1.5 MPa, respectively, by filling the space between the calcite-PMMA granules. As these values are suitable for clinical use, the porous CO 3 Ap blocks have potential applications as scaffolds for bone regeneration. [ABSTRACT FROM AUTHOR]

In recent years, focuse has moved to multiphase calcium orthophosphate scaffolds to balance the more stable calcium orthophosphate phase with another more soluble phase. This will enable the researchers to tailor the major biomedical properties to suit its intended application. In this study, beta tricalcium phosphate (β-TCP)/carbonate apatite (CO3 Ap) scaffolds were fabricated via freeze drying method. The effect of soaking time (2 h, 4 h and 6 h) on the phase transformation of β to alpha (α) phase was investigated. The scaffolds were sintered at 1300°C for respective soaking time and quenched in air to obtain biphasic β-TCP/α-TCP scaffolds. To obtain biphasic β-TCP/CO3 Ap scaffold, the obtained scaffolds were then subjected to hydrothermal treatment in 1 M of sodium bicarbonate at 200°C for 5 days for phase transformation of α-TCP phase into CO3 Ap phase via dissolution-precipitation process. X-ray diffraction (XRD) analysis before hydrothermal treatment confirms the existence of biphasic β and α phase at all soaking time. The percentage of α phase increases as soaking time increases. Fourier transform infrared (FTIR) analysis confirms the present of carbonate ions substitution into the scaffold after hydrothermal treatment. Therefore, it is concluded that as soaking time increases, the unstable phase of α-TCP increases in the biphasic β-TCP/ α-TCP scaffolds. Thus, the phase transformation from α-TCP phase to CO3 Ap phase increases as soaking time increases. [ABSTRACT FROM AUTHOR]

Two types of synthetic carbonate apatite [potassium-containing carbonate apatite (CAK) and sodium-containing carbonate apatite (CANa)] were prepared and characterized by thermogravimetric analysis, X-ray diffraction analysis (XRD) and Fourier transform infrared spectroscopy. The chemical formulas of carbonate apatite were determined to be Ca9.36K0.12(PO4)5.12(CO3)0.88(OH)1.73 and Ca8.72Na1.33(PO4)4.96(CO3)1.04(OH)1.80, respectively. Thermogravimetric analysis showed that the final weight loss at 1,200°C reached about 11.2% for CAK and 13.9% for CANa. Carbonate loss gradually occurred above 150°C and continued to 1,200°C. The crystallinity of the apatite phase was found to be much improved between 800 and 850°C for CAK and 750 and 800°C for CANa, where rapid carbonate loss occurred. A small amount of CaO formed above 900°C. For CANa, NaCaPO4 also formed above 700°C in both apatites. Although the lattice parameters of the carbonate apatites varied with temperature, the final a and c lattice parameters attained constant values of 0.9421 and 0.6881 nm. [ABSTRACT FROM AUTHOR]

Bone reconstructive surgery has become a common procedure, and bone transplantation has become the second most frequently performed tissue transplantation procedure worldwide. Therefore, the need for bone substitute materials has increased. Artificial bone substitutes exhibit osteoconductive properties and feature several advantages, including abundant resources, low cost, and low donor site morbidity. Carbonate apatite (CO3Ap) is a calcium phosphate ceramic that can be used as a synthetic bone graft. The carbonate content of this ceramic is similar to that of bone apatite. In this review, we show that carbonate apatite can be degraded given its chemical reactivity in a weakly acidic environment and through osteoclast resorption. Moreover, it is osteoconductive and promotes bone tissue formation without fibrotic tissue formation. Additionally, microstructural analysis revealed that new bone tissue is formed within the bone graft itself. [ABSTRACT FROM AUTHOR]

Abstract Objectives The aim of this present study was to investigate the effect of setting atmosphere on replacement of apatite cement with new bone both in vitro and in vivo. Material and methods Apatite cement consisting of an equimolar mixture of tetracalcium phosphate and anhydrous dicalcium phosphate was mixed with distilled water and allowed to set at 37 °C and 100% relative humidity under 0% , 5%, and 100% CO 2 atmospheres. X-Ray diffraction and Fourier Transform Infrared Spectroscopy were employed to confirm the carbonate apatite formation. Micro-CT and histological evaluation was made at 1 and 6 month(s) using twelve 10-week-old specific-pathogen-free male Wistar rats. Results B-type carbonate apatite was found when the apatite cement was set under 100% CO 2 and 5% CO 2. More carbonate apatite was formed in the case of 100% CO 2 when compared with 5% CO 2 , and none was formed under 0% CO 2. Interestingly, unreacted tetracalcium phosphate was significant when apatite cement was set under 0% CO 2 , indicating the formation of Ca-deficient hydroxyapatite. When a bone defect of rat tibia was reconstructed in these conditions of apatite cement and sintered hydroxyapatite, replacement of the apatite cement was confirmed 6 months after implantation, whereas no replacement was observed in the case of sintered hydroxyapatite. The amount of replacement of apatite cement with bone was greater, on the order of 100% CO 2 and 5% CO 2 , followed by 0% CO 2. Conclusion The results obtained in the present study demonstrated that setting atmosphere clearly plays an important role in the replacement of set apatite cement with bone. [ABSTRACT FROM AUTHOR]

Subcutaneous calcifications can lead to complications, including pain, inflammation, ulceration and immobilization. Studies on the pathophysiology of mineral compositions and effective treatment modalities are limited. We therefore studied 14 patients with subcutaneous calcifications. Mineral material was collected and analysed by Fourier transform infrared spectrometry. Blood analyses were run to evaluate systemic alterations of mineral metabolism. Carbonate apatite (CAP) was found to be the single constituent in the majority of patients (n = 9, 64.3%), 3 cases (21.4%) had a composition of CAP and calcium oxalate dihydrate and one case had a combination of CAP and magnesium ammonium phosphate, whereas CAP was the major component in all 4 cases. Only one case showed predominantly calcium oxalate. Thus, CAP was found to be the only or predominant component in most cases of subcutaneous calcifications. Chemical analyses of the mineral compositions may aid in the development of new treatment regimes to improve the solubility of mineral components and to decrease extraosseous calcifications. [ABSTRACT FROM AUTHOR]

Effect of trisodium citrate on the precipitation of carbonate apatite is studied. The experimental series are performed in the solution of artificial urine. The investigations are related to infectious urinary stones formation as carbonate apatite is one of the main components of this kind of stones. To mimic a real infection in urinary tract the aqueous ammonia solution was added to the solution of artificial urine. The spectrophotometric results demonstrate that trisodium citrate increases induction time with respect to carbonate apatite formation and decreases the efficiency of carbonate apatite precipitation. The inhibitory effect of trisodium citrate on the precipitation of carbonate apatite is explained in base of chemical speciation analysis. Such an analysis demonstrates that the inhibitory effect is mainly related with the fact that trisodium citrate binds Ca 2+ ions and causes the formation of CaCit − and Ca 10 (PO 4 ) 6 CO 3 complexes. Trisodium citrate binds Ca 2+ ions in the range of pH from 6 to 9.5 for which carbonate apatite is favored to be formed. [ABSTRACT FROM AUTHOR]

Background Urinary tract infections caused by Corynebacterium urealyticum are uncommon in veterinary medicine. Encrusted cystitis, encrusted pyelitis and uroliths have been described as complications in humans, but only encrusted cystitis and cystoliths have been reported in dogs so far. Because C. urealyticum is usually resistant to all standard antibacterial drugs, antimicrobial treatment and elimination of this microorganism are challenging. Case report An 11-month-old female spayed mixed-breed dog was evaluated because of a C. urealyticum urinary tract infection, mineralisation within both renal pelvises and failure of antimicrobial treatment. Physical examination, haematology and biochemistry were unremarkable. Radiographic and ultrasonographic examinations confirmed bilateral nephrolithiasis. Voided uroliths were composed of 100% carbonate apatite. Urinalysis was indicative of bacterial infection. Aerobic culture of the urine and 16S rRNA sequencing identified significant growth of C. urealyticum and susceptibility testing revealed sensitivity to only vancomycin and linezolid. Conclusion Treatment with the oxazolidinone antibacterial, linezolid, in combination with a urine-acidifying diet resulted in elimination of this multiresistant microorganism and complete resolution of nephrolithiasis. [ABSTRACT FROM AUTHOR]

Carbonate apatite (CO3AP), fabricated by dissolution-precipitation reaction based on an appropriate precursor, is expected to be replaced by bone according to bone remodeling cycle. One ofthe precursor candidates is gypsum because it shows self-setting ability, which then enables it to be shaped and molded. The aim of this study, therefore, was to fabricate CO3AP blocks from set gypsum. Set gypsum was immersed in a mixed solution of 0.4 mol/L disodium hydrogen phosphate (Na2HPO4) and 0.4 mol/L sodium hydrogen carbonate (NaHCO2) at 80-200°C for 6-48 h. Powder X-ray diffraction patterns and Fourier transform infrared spectra showed that CO3AP block was fabricated by dissolution-precipitation reaction in Na2HPO4-NaHCO3 solution using set gypsum in 48 b when the temperature was 100°C or higher. Conversion rate to CO3AP increased with treatment temperature. CO3AP block containing a larger amount of carbonate was obtained when treated at lower temperature. [ABSTRACT FROM AUTHOR]

Osteoclast responsive carbonate apatite (CAp) coatings with different carbonate content rates and non-bioabsorbable hydroxyapatite (HAp) coating were formed on Mg-4mass% Y-3mass% rare earth (WE43) alloy. Electrochemical impedance spectroscopy measurement in a cell culture medium was performed for 6 h and 10 weeks, and the corrosion morphology was observed using a scanning electron microscope. Coating layer resistance of the CAp-coated specimens for 6 h was 104 Ωcm2 which was higher than 2 × 103 Ωcm2 of the HAp-coated specimen. Mean polarization resistance for the initial 4 weeks for the former was 4 × 104–7.5 × 104 Ωcm2 which was higher than 2 × 104 Ωcm2 of the latter. [Display omitted] • Long-term impedance behavior of carbonate apatite- and hydroxyapatite-coated WE43. • Higher corrosion suppression ability of carbonate apatite than hydroxyapatite coating. • After coating breakdown, corrosion is dominated by the corroded area. • As carbonate content rate of coating increases, corrosion suppression ability increases. • Localized corrosion under carbonate apatite coating indicates a low level of defects. [ABSTRACT FROM AUTHOR]

Carbonate apatite-chitosan scaffolds (CA-ChSs) were fabricated using the lyophilization technique. It was found that ChSs prepared with 200 mg chitosan powder (ChSs200) had well-structured three-dimensional architecture with high porosity and good retentive form without brittleness. In addition, it was shown that the number of osteoblast-like cells MC3T3-E1 proliferated on desalinated ChSs200 was larger than that on the non-desalinated ChSs200. CA-ChSs were fabricated by adding 100 mg carbonate apatite (CA) to 200 mg chitosan gels followed by freeze-drying (CA100ChSs200). SEM observation revealed that CA100ChSs200 had favorable three- dimensional porous structures. The number of living cells increased more rapidly on CA100ChSs200 prepared with different amounts of CA than on ChSs. ALP activity significantly increased after day 14 and reached a plateau after day 21 in ChSs200 and CA100ChSs200. It was concluded that newly developed CA100ChSs200 may be a possible scaffold material for tissue engineering. [ABSTRACT FROM AUTHOR]

Sr-containing carbonate apatite (SrCAp) specimens of varied Sr contents, ranging from 0 to 13.3 mol%, were prepared through a phosphate treatment of set gypsum-and-carbonate mixture at 100°C for 7 days. Effects of Sr content in SrCAp on microstructure, osteoblast-like cell (MC3T3-E1) attachment and proliferation, and alkaline phosphatase (ALP) activity were evaluated. Sr2+ ion substituted Ca2+ ion in the apatite lattice. Carbonate content was about 9-13.6 wt%, increasing in content level as Sr content increased. Sr addition benefited cell attachment but had no significant influence on cell proliferation, although the latter was inhibited at the highest Sr content. ALP activity reached a peak in specimen containing 3.4 mol% of Sr. The present study revealed that SrCAp is a promising candidate for use as a bone substitute material with good resorbabilty and osteoconductivity. [ABSTRACT FROM AUTHOR]

Abstract: The ability of carbonate apatite (CO3Ap) to enhance antigen-specific immunity was examined in vitro and in vivo to investigate its utility as a vaccine carrier. Murine bone marrow-derived dendritic cells took up ovalbumin (OVA) containing CO3Ap more effectively than free OVA. Interestingly, mice immunized with OVA-containing CO3Ap produced OVA-specific antibodies more effectively than mice immunized with free OVA. Furthermore, immunization of C57BL/6 mice with OVA-containing CO3Ap induced the proliferation and antigen-specific production of IFN-γ by splenocytes more strongly than immunization with free OVA. Moreover, no significant differences were detected in the induction of delayed-type hypersensitivity responses, an immune reaction involving an antigen-specific, cell-mediated immune response between OVA-containing CO3Ap and OVA-containing alumina salt (Alum), suggesting that CO3Ap induced cell-mediated immune response to the same degree as Alum, which is commonly used for clinical applications. This study is the first to demonstrate the induction of antigen-specific immune responses in vivo by CO3Ap. [Copyright &y& Elsevier]

Abstract: Plasmid DNA is one of the indispensable components in molecular biology research and a potential biomaterial for gene therapy and DNA vaccination. Both quality and quantity of extracted plasmid DNA are of the great interests in cloning and subsequent expression of genes in vitro and in vivo for basic research and therapeutic interventions. Bacteria with extremely short generation times are the valuable source of plasmid DNA that can be isolated through a number of existing techniques. However, the current methods have some limitations in isolating high quality plasmid DNA since the multimeric plasmid which is believed to be more efficiently transcribed by RNA polymerase than the monomeric form, is almost lost during the extraction process. Recently, we developed a rapid isolation technique for multimeric plasmid based on generation of a ‘protein aggregate’ using a zwitterionic detergent and alkali. Here we have investigated the roles of different parameters in the whole extraction process to optimise the production of high quality multimeric plasmid DNA. Moreover, we have showed the advantageous effects of nanoparticles to effectively sediment the ‘protein aggregate’ for smooth elution of multimeric plasmid DNA from it. Finally, quality assessment study has revealed that the isolated multimeric DNA is at least 10 times more transcriptionally active than the monomeric form isolated by the commercially available Qiaget kit. [Copyright &y& Elsevier]

Abstract: Genetic manipulation of human cells through delivery of a functional gene or a gene-silencing element is an attractive approach to treat critical diseases very precisely and effectively. Extensive research on the genetic basis of human diseases with complete sequencing of human genome has revealed many vital genes as possible targets in gene therapy programs. On the other hand, to facilitate cell- or tissue-directed delivery of genes and gene-silencing nucleic acid sequences, both genetic and chemical engineering approaches have led to the generation of various viral and nonviral carriers. However, considering the issues of both safety and efficacy, none of the existing vectors is an ideal candidate for clinical use. We recently established pH-sensitive inorganic nanocrystals of carbonate apatite with capability of efficient intracellular delivery and release of associated DNA molecules for subsequent protein expression. Here we show a new synthetic approach for carbonate apatite crystals with stronger affinity toward DNA, leading to significant increment in both transgene delivery and expression. Moreover, CaCl2 and NaCl, existing as the major electrolytes in the bicarbonate-buffered solution, dose-dependently govern particle size and eventually internalization and expression of particle-associated DNA. [Copyright &y& Elsevier]

Abstract: mRNA instead of DNA provides a new and attractive approach for gene therapy and genetic vaccination. Delivery of mRNA can bypass nuclear localization step enabling protein expression directly in cytoplasm through transcription. Current technologies for mRNA delivery are predominantly based on cationic liposomes with low activity for transfection. We, previously reported that applying inorganic nano-particles of carbonate apatite onto cationic liposome of DOTAP {N-[1-(2,3-dioleoloxy)propyl]-N,N,N-trimethyl ammonium chloride} resulted in high transfection potency for luciferase mRNA both in mitotic and non-mitotic cells. In this paper, we expanded the previous work and performed in detail study especially on two important parts, evaluating the image of the complex and analyzing the steps of gene delivery to detect the determinant factor for enhanced transfection potency. Transmission electron microscopic (TEM) observation clearly indicated the presence of inorganic carbonate apatite particles on mRNA–liposome complex and demonstrated the structure of the new hybrid carrier material. Due to apparently higher gravitational force of absorbed inorganic nano-particles, cellular contact and internalization of hybrid-particle-associated mRNA were significantly enhanced compared to DOTAP. This analysis indicates rather than downstream steps, initial steps of cell membrane binding and subsequent way of internalization could be the determinant factor for final protein expression. Moreover, we compared transfection efficiency of mRNA and pDNA in Human Umbilical Vein Endothelial cell (HUVEC) to demonstrate advantages of mRNA delivery. [Copyright &y& Elsevier]

The effect of temperature on crystallinity of carbonate apatite (CAp) foam prepared from α-tricalcium phosphate (α-TCP) foam by hydrothermal treatment was investigated in the present study. The α-TCP foams were prepared through a conventional sintering method using polyurethane foam as template. Then, the resultant α-TCP foams were hydrothermally treated with Na2CO3 aqueous solution at 100°C, 150°C and 200°C for 72 h. After hydrothermal treatment, the cancellous bone-like macroporous structure of the α-TCP foams was maintained. However, microscopic morphology of the foams' frame significantly changed after the 72 h treatment period. The smooth surface of α-TCP foam disappeared and the whole surface was covered with plate-like deposits. The plate-like deposits treated at 150°C and 200°C had smooth surface while those treated at 100°C were constructed from spherical particles of approximately 200 nm in diameter. The results of X-ray diffraction and Fourier transform infrared analysis showed that α-TCP was completely converted to CAp and the crystallinity of CAp prepared at 100°C was significantly lower than those prepared at 150°C and 200°C. Hydrothermal treatment of α-TCP foam at 100°C allowed the formation of low-crystalline CAp foam but complete conversion needs a longer treatment period. [ABSTRACT FROM AUTHOR]

Biological apatite in enamel, dentin, cementum, and bone is highly individualized hydroxyapatite with high tissue dependency. Often, standard and average textbook values for biological apatite do not apply to actual subjects, and the reported results of analyses differ among investigators. In particular, the term biological apatite is often confusingly and incorrectly used to describe carbonate apatite. The purpose of this review is to prevent further confusion. We believe that apatite should be well understood across disciplines and the terminology clearly defined. According to a definition by the International Mineralogical Association's Commission on New Minerals Nomenclature and Classification, biological apatite formed by living organisms is a type of hydroxyapatite. More specifically, it is carbonated hydroxyapatite, which is quite different from frequently misnamed carbonate apatite. We hope that this definition will be widely adopted to remove confusion around the naming of apatite in many research and applied fields. [ABSTRACT FROM AUTHOR]

A 66-year-old woman developed firm, painless, slowly growing nodular masses over her elbows, fingers, toes, and left hip over four years. Aspiration of the elbow mass revealed a white chalky material that was shown to be carbonate apatite on infrared spectroscopy and energy dispersive X-ray spectroscopy. We discuss the classification of tumoral calcinosis and the nature of the calcium deposits. Tumoral calcinosis should be differentiated from tophaceous gout and calcium pyrophosphate dihydrate crystal deposition disease. Polarizing light microscopy and crystal analysis by X-ray and infrared spectroscopy, electron or X-ray diffraction will confirm the diagnosis. Secondary causes of tumoral calcinosis should also be excluded. [ABSTRACT FROM AUTHOR]

Our previous in vivo and in vitro studies revealed excellent tissue biocompatibility and osteoconductivity of porous sintered carbonate apatite (CA). The present study focused on the ultrastructural details of cells involved in the degradation of CA and new bone formation. Electron microscopy indicated that multinucleated giant cells (MNGCs) were actively involved in CA resorption. MNGCs extended their irregular cytoplasmic protrusions deeply into the interstitial spaces between CA particles. Endophagosomes were formed by encircling partially dissolved or intact CA crystals via the development of pseudopodia-like cytoplasmic protrusions, the configuration of which was somewhat different from that of the typical ruffled border of bone-resorbing osteoclasts. Subsequently, most CA particles in MNGCs were irregular in shape, suggesting that acidic degradation of CA occurred mainly intracellularly. Mononuclear cells, such as macrophage-like and/or fibroblast-like cells, also took up and degraded some CA Growth of very thin needle like crystals was observed in close association with CA Osteoblasts directly faced the CA and secreted osteoid matrix. At the CA-bone interface, an electron-dense and homogeneous thin layer free of collagen fibers was sometimes observed, suggesting an involvement in CA-bone bonding. [ABSTRACT FROM AUTHOR]

Abstract: Refinement of the single-crystal X-ray diffraction structure of a type A carbonate apatite [CAp; Ca10(PO4)6– y (CO3) x +(3/2) y (OH)2−2 x , , ; space group ] has been continued with independent positional and isotropic displacement parameters for the carbonate oxygen atoms, reducing the residual indices significantly (, ) and confirming the earlier structure assignment. The carbonate ion is located in the apatite channel at z≈0.5, and oriented with two oxygen atoms close to the c-axis. Rigid body refinement, giving a preferred structure, used a novel procedure for defining the ideal equilateral triangular geometry of the channel carbonate ion. Resolution of the channel carbonate ions in type A-B CAp (, ; P63/m) is also improved. Channel carbonate ions in CAp are canted, rotated and displaced to optimize Ca2–O bond distances. The rotation of the A1 carbonate in type A-B CAp is opposite to that of the channel carbonate in type A CAp, due mainly to the accommodation of a second channel carbonate ion (A2). These structures simulate the local structure of type A carbonate in hydroxyapatite of bone and dental enamel. [Copyright &y& Elsevier]

The structure of a complex, disordered type A–B carbonate apatite (CAp) of approximate composition Ca10(PO4)6-y(CO3)x+(3/2)y(OH)2-2x, x–0.7, y–0.6, synthesized at 3 GPa, 1400°C has been determined using single-crystal X-ray diffraction and FTIR spectroscopy at room temperature and pressure. Crystal data are: hexagonal, space group P63/m, Z=1; a=9.5143(3), c=6.8821(2) Å, V=539.5 Å3, and R=0.025. There are three structural locations for the carbonate ion. The channel carbonate is mainly in the closed vertical configuration of the P&3macr; structure, with two of its oxygen atoms close to the c-axis (A1 carbonate; IR bands at 1541 and 1449 cm-1), but subordinate amounts are also located in an open vertical configuration (A2 carbonate; IR bands at 1563 and 1506 cm-1). The type B carbonate ion is located close to the sloping faces of the PO4 tetrahedron (IR bands at 1474 and 1406 cm-1), confirming earlier inferences from polarized IR spectra. [Copyright &y& Elsevier]

The aim of this study was to detect, isolate and characterize the nanobacteria from human renal stones from a north Indian population, and to determine their role in biomineralization. Renal stones retrieved from the kidneys of 65 patients were processed and subjected to mammalian cell culture conditions. The isolated bacteria were examined using scanning (SEM) and transmission electron microscopy (TEM). They were characterized for the presence of DNA, proteins and antigenicity. The role of these bacteria in biomineralization was studied by using the 14C-oxalate based calcium oxalate monohydrate (COM) crystallization assay. We observed the presence of apatite forming, ultrafilterable gram negative, coccoid microorganisms in 62% of the renal stones. SEM studies revealed 60–200 nm sized organisms with a distinct cell wall and a capsule. TEM images showed needle like apatite structures both within and surrounding them. They were heat sensitive, showed antibiotic resistance and accelerated COM crystallization. A potent signal corresponding to the presence of DNA was observed in demineralized nanobacterial cells by flow cytometry. The protein profile showed the presence of several peptide bands of which those of 18 kDa and 39kDa were prominent. Apatite forming nanosized bacteria are present in human renal stones and may play a role in the pathophysiology of renal stone formation by facilitating crystallization and biomineralization. However, further studies are required to establish the exact mechanism by which nanobacteria are involved in the causation of renal stones. [ABSTRACT FROM AUTHOR]

X-ray and time of flight neutron diffraction data, FTIR and MAS-NMR spectra, and ICP-AES and carbonate analyses have been collected from a sodium-containing carbonate apatite (CO3 content 12.5(7) wt%). A structural model based on Holly Springs hydroxyapatite without CO32− ions showed an apparent reduction in the PO4 tetrahedral volume which is ascribed to CO32− replacing PO43− ions in the lattice. Four structural models from the literature with the CO32− ion explicitly modelled were fitted to the neutron diffraction data by the Rietveld method.The best fit was obtained with the CO32− ion in disorder between the mirror symmetry related faces of a vacant PO43− site and with the normal to the plane of the CO32− ion at ∼30° to the c-axis. This angle is consistent with results from previous polarised IR measurements on single crystals of francolite (a fluorocarbonate apatite) and human dental enamel. Further refinement of the model revealed a hitherto unknown atom site close to the unit cell origin, (possibly a water molecule). The refined hexagonal unit cell parameters from the neutron diffraction data were a=9.3446(3) A˚ and c=6.9199(4) A˚. [Copyright &y& Elsevier]

Electrolytically deposited carbonate apatite coating demonstrates higher strength but weaker support for bone marrow stromal cell attachment than do biomimetically deposited coatings. It is hypothesized that the incorporation of chitosan will increase the biocompatibility of electrolytic coating while maintaining its original strength. To verify this hypothesis, we formed a hybrid calcium phosphate/chitosan coating through electro-deposition. We found that the incorporation of chitosan influenced calcium phosphate formation and crystallization. Moreover, coating thickness and surface roughness decreased with increasing chitosan concentration. Hybrid coating exhibited an increased dissolution rate in both acidic and neutral simulated physiologic solution, whereas no significant difference on adhesive strength was found between the hybrid and original coatings (P > 0.05). Most importantly, the calcium phosphate/chitosan coating proved to be a more favorable surface for goat bone marrow stromal cell attachment than an unincorporated coating (P < 0.01). Considering its economic and simple production, a hybrid calcium phosphate/chitosan coating is thought to be an attractive candidate for future applications. [ABSTRACT FROM AUTHOR]

Biomimetically deposited octacalcium phosphate (OCP) and carbonate apatite (BCA) as well as electrolytically deposited carbonate apatite (ECA) were considered as promising alternatives to conventional plasma spraying hydroxyapatite. This study compared their physicochemical characteristics and cell attachment behavior. The physicochemical characteristics included scanning electron microscopy observation, X-ray diffraction analysis, Fourier transform infrared spectroscopy analysis, surface roughness, coating thickness, dissolution test and scratch test. Cell attachment tests included morphology observation with stereomicroscopy and scanning electron microscopy as well as cell number count with DNA content assay. The OCP coating had 100% crystallinity and was about 40 μm thick, composed of large plate-like crystals of 30 μm, with the lowest surface roughness (Ra=2.33 μm). The BCA coating had 60% crystallinity and was approximately 30 μm in thickness, composed of small crystals of 1–2 μm in size, with the highest surface roughness (Ra=4.83 μm). The ECA coating had intermediate characteristics, with 78% crystallinity, 45 μm thickness, crystals of 5–6 μm and an average roughness of 3.87 μm. All coatings could be seen by eyes dissolving quickly and completely into acidic simulated body fluid (simulated physiological solutions—SPS, pH 3.0) but slowly and incompletely into neutral SPS (pH 7.3). It was suggested that the main factor determining coating dissolution in acidic SPS was the solubility isotherm, while some other factors including crystallinity and crystal size joined to determine coating dissolution in neutral SPS. In regard to adhesive strength, results of scratch test showed the critical load at the first crack of coating (Lc1) was tightly related to crystal size as well as their arrangement, while the critical load at the total delamination of coating (Lc2) was also related to the coating thickness. The ECA coating had the highest values. Owing to higher dissolution rate and globular appearance, BCA coating demonstrated the best goat bone marrow stromal cells attachment at 1 day or 3 days, followed by OCP and ECA coating. [Copyright &y& Elsevier]

More than half of the analyzed calculi from patients from Macedonia are composed of whewellite, weddellite and carbonate apatite (as single components or in binary or ternary mixtures). In order to develop a simple and satisfactorily reliable method for quantitative analysis of urinary calculi, the possibility was explored to employ artificial neural networks (ANNs) as a tool for such a purpose. By changing the number of input and hidden neurons, a search was made for the three-layered feed-forward ANN which would give the best performance. The root-mean-square errors (RMSE) for the test samples are: 0.035 for whewellite, 0.064 for weddellite and 0.078 for carbonate apatite. The accuracy of the method was checked using standard-addition method on real samples. The discrepancies between calculated and predicted mass fraction of constituents were in the range acceptable for use of the proposed method in clinical laboratories. [Copyright &y& Elsevier]

A new space group and structure are reported for type A carbonate apatite (CAp) of composition Ca10(PO4)6[(CO3)x(OH)2−2x], x&ges;0.5, synthesized at 2 GPa, 1400–1500°C. Crystal data are trigonal, space group P3¯, Z=1; x&ap;0.75, a=9.5211(3), c=6.8725(2) A˚, V=539.5 A˚3, R=0.030, and Dx=3.152 g/cm3; x&ap;0.50, a=9.4917(2), c=6.8758(3) A˚, V=536.5 A˚3, R=0.030, and Dx=3.150 g/cm3. In the P3¯ structure, the type A carbonate ion is ordered along the apatite channel at z=0.5. Two of the oxygen atoms of the carbonate ion lie close to the c-axis, with the plane of the ion canted ∼12°. FTIR spectra are similar to that of type A carbonate hydroxylapatite. The present structure may be an appropriate model for the orientation of the type A carbonate ion in bone and enamel. [Copyright &y& Elsevier]

The objective of this study was to investigate a bone graft substitute containing carbonate apatite (CO3Ap) to analyze bone replacement and the state of bone formation in vitro and in vivo compared with autogenous bone (AB) or control. An osteoclast precursor cell line was cultured with AB or CO3Ap, and morphological analysis using scanning electron microscopy and a tartrate-resistant acid phosphatase activity assay were performed. The right maxillary first and second molars of Wistar rats were extracted and compensated by AB or CO3Ap granules. Following implantation, the bone formation state was evaluated after 3, 5, 7, 14, and 28 days of surgery by micro-computed tomography and immunohistostaining. The osteoclast-like cell morphology was typical with many cell protrusions in the AB and CO3Ap groups. Additionally, the number of osteoclast-like cells formed in the culture increased in each group; however, there was no significant difference between the AB and CO3Ap groups. Five days after tooth extraction, osteoclasts were observed near CO3Ap. The bone thickness in the CO3Ap group was significantly increased than that in the control group and the bone formation in the CO3Ap group increased by the same level as that in the AB group. CO3Ap is gradually absorbed by osteoclasts in the extraction socket and is easily replaced by alveolar bone. The process of bone replacement by osteoclasts is similar to that of autologous bone. By observing the process of bone replacement in more detail, it may be possible to gain a better understanding of the bone formation and control the amount of bone after surgery. [ABSTRACT FROM AUTHOR]

The ESR spectrum of X-irradiated carbonated apatites precipitated from aqueous solutions was studied as a function of their carbonate content and drying temperature. When the latter increases from 25 to 400 degrees C, the ESR spectrum is gradually modified and becomes similar to the spectrum of carbonated apatites, synthesized at high temperatures by solid state reactions. The latter ESR spectrum is dominated by CO3(3-)-contributions whereas the spectrum of precipitated samples dried at 25 degrees C can mainly be interpreted in terms of CO2-, CO3-, and O- ions. The behavior of these earlier-reported CO2-, CO3-, and O- centers is now studied as a function of drying temperature. In addition, the Spin Hamiltonian parameters of the CO3(3-) centers are determined and some other new paramagnetic radicals are discussed. It is shown that a CO3(2-) ion at a phosphate lattice site (B-type substitution) may give rise to either a CO2-, CO3-, or CO3(3-) radical on X-irradiation, depending on the sample preparation conditions. A surface CO3(2-) ion may cause a surface CO2-, CO3-, or O- radical. From the reported results it is not unambiguously clear whether the CO3(3-) ion detected in the samples with the relatively lowest carbonate content should be located on the surface or on a hydroxyl lattice site (A-type substitution). An important result is that the absolute concentration of the B-type CO3(3-) ion increases with increasing carbonate content as was also the case for the earlier reported B-type radicals (isotropic CO2- and CO3-). On the other hand, the absolute concentration of the surface radicals decreases with increasing carbonate content. The reported results show that similar deconvolution techniques can be applied in the future for the study of ESR spectra of calcified tissues. This will allow a more efficient phenomenological investigation of the latter. [ABSTRACT FROM AUTHOR]

Abstract: Leukemia and lymphoma cells are potential targets for genetic manipulation in cancer therapy. On the other hand, genetically modified autologous lymphocytes expressing a chimeric antigen against a receptor overexpressed in tumor cells or tumor vasculature are promising cell-based therapeutics for cancer.However, the lack of a smart device for efficient transgene delivery to the lymphocytes poses the major obstacle to the successful clinical applications of these attractive approaches. Recently, we developed a carbonate apatite-based nanocarrier system for effective intracellular delivery and release of DNA molecules, achieving very high level of transgene expression in both primary and cancer cells. Although its efficacy in human T leukemia cells is relatively poor, immobilization of fibronectin and/or chimeric E-cadherin-Fc on particle surface could enhance transgene delivery in presence of an actin filament disrupter. Here, we report for the first time that simultaneous stimulation of human T leukemia cells by a protein kinase C (PKC) activator, a Ca2+ ionophore and an actin filament disrupter dramatically accelerated carbonate apatite-mediated transgene delivery in the cells, resulting in over 100-fold more efficacy than commcercially available lipofectamine. [Copyright &y& Elsevier]

Abstract: Intracellular delivery of a functional gene or a nucleic acid sequence to specifically knockdown a harmful gene is a potential approach to precisely treat a critical human disease. The intensive efforts in the last few decades led to the development of a number of viral and non-viral synthetic vectors. However, an ideal delivery tool in terms of the safety and efficacy has yet to be established. Recently, we have developed pH-sensing inorganic nanocrystals of carbonate apatite for efficient and cell-targeted delivery of gene and gene-silencing RNA. Here we show that addition of very low level of fluoride to the particle-forming medium facilitates a robust increase in transgene expression following post-incubation of the particles with HeLa cells. Confocal microscopic observation and Southern blotting prove the cytoplasmic existence of plasmid DNA delivered by likely formed fluoridated carbonate apatite particles while degradation of plasmid DNA presumably by cytoplasmic nucleases was noticed following delivery with apatite particles alone. The beneficial role of fluoride in enhancing carbonate apatite-mediated gene expression might be due to the buffering potential of generated fluoridated apatite in endosomal acidic environment, thereby increasing the half-life of delivered plasmid DNA. [Copyright &y& Elsevier]

The utility of carbonate apatite (CO3Ap) as a bone substitute has been demonstrated. The feasibility of fabricating macroporous CO3Ap was evaluated through a two-step dissolution–precipitation reaction using gypsum as the precursor and spherical phenol resin as the porogen. Porogen-containing gypsum was heated to burn out the porogen and to fabricate macroporous structures. Gypsum transformed into CaCO3 upon immersion in a sodium carbonate solution, while maintaining its macroporous structure. Next, CaCO3 transformed into CO3Ap upon immersion in a Na2HPO4 solution while maintaining its macroporous structure. The utility of the macroporous CO3Ap for histologically reconstructing bone defects was evaluated in rabbit femurs. After 4 weeks, a much larger bone was formed inside the macroporous CO3Ap than that inside non-macroporous CO3Ap and macroporous hydroxyapatite (HAp). A larger amount of bone was observed inside non-macroporous CO3Ap than inside macroporous HAp. The bone defects were completely reconstructed within 12 weeks using macroporous CO3Ap. In conclusion, macroporous CO3Ap has good potential as an ideal bone substitute. [ABSTRACT FROM AUTHOR]