Apatitic Calcium Phosphate Research Articles

Sodium fusidate loaded apatitic calcium phosphates: Adsorption behavior, release kinetics, antibacterial efficacy, and cytotoxicity assessment

The present work reports the adsorption, release, antibacterial properties, and in vitro cytotoxicity of sodium fusidate (SF) associated with a carbonated calcium phosphate bone cement. The adsorption study of SF on cement powder compared to stoichiometric hydroxyapatite and nanocrystalline carbonated apatite was investigated to understand the interaction between this antibiotic and the calcium phosphate phases involved in the cement formulation and setting reaction. The adsorption data revealed a fast kinetic process. However, the evolution of the amount of adsorbed SF was well described by a Freundlich-type isotherm characterized by a low adsorption capacity of the materials toward the SF molecule. The in vitro release results indicated a prolonged and controlled SF release for up to 34 days. The SF amounts eluted daily were at a therapeutic level (0.5–2 mg/L) and close to the antibiotic minimum inhibitory concentration (0.1–0.9 mg/L). Furthermore, the release data fitting and modeling suggested that the drug release occurred mainly by a diffusion mechanism. The antibacterial activity showed the effectiveness of SF released from the formulated cements against Staphylococcus aureus. Furthermore, the biological in vitro study demonstrated that the tested cements didn’t show any cytotoxicity towards human peripheral blood mononuclear cells and did not significantly induce inflammation markers like IL-8.

Spectroscopic characterization of calcium phosphate precipitated under human eye conditions: An in vitro study

Calcification is a well-known process of calcium phosphate mineralization observed in intraocular lenses. Despite the many works conducted in this field, there is no strict explanation of the mechanisms of this process. In order to better understand the phenomenon, i.e., the mechanisms and structural conditions that promote calcification, any research observations should be conducted under conditions that best reflect those of the human eye. Taking into account the specific anatomy and physicochemical conditions of the human eye, the problem under discussion becomes difficult to solve in vitro. In the present study, calcium phosphates formed under conditions similar to those in the human eye were characterized using SEM/EDS and infrared spectroscopy.Conducted study showed the formation of white spherical precipitates, which are unstable when extracted from solution. Such precipitates were characteristic of solutions containing 1.5–3.0 mM2 of solutes. Elemental analysis showed a Ca/P ratio of 1.64–1.65, which is similar to the ratio for hydroxyapatite (1.67). Chemical structure analysis revealed the presence of broad bending and stretching bands at 475–830 cm−1 and 880–1250 cm−1, respectively, which are characteristic of PO43− groups in apatite calcium phosphates. In further analysis involving numerical fitting the bands corresponding to apatitic PO43− and indicating the presence of calcium phosphates hydration were found. The results allow the selection of immersion media for further studies involving the incubation of hydrogel intraocular lenses.

On the rocks: can urologists identify stone composition based on endoscopic images alone? A worldwide survey of urologists.

As part of the management of nephrolithiasis, determination of chemical composition of stones is important. Our objective in this study is to assess urologists' accuracy in making visual, intraoperative determinations of stone composition. We conducted a REDCap survey asking urologists to predict stone composition based on intraoperative images of 10 different pure-composition kidney stones of 7 different types: calcium oxalate monohydrate (COM), calcium oxalate dihydrate (COD), calcium phosphate (CP) apatite, CP brushite, uric acid (UA), struvite (ST) and cystine (CY). To evaluate experience, we examined specific endourologic training, years of experience, and number of ureteroscopy (URS) cases/week. A self-assessment of ability to identify stone composition was also required. With a response rate of 26% (366 completed surveys out of 1,370 deliveries), the overall accuracy of our cohort was 44%. COM, ST, and COD obtained the most successful identification rates (65.9%, 55.7%, and 52.0%, respectively). The most frequent misidentified stones were CP apatite (10.7%) and CY (14.2%). Predictors of increased overall accuracy included self-perceived ability to determine composition and number of ureteroscopies per week, while years of experience did not show a positive correlation. Although endoscopic stone recognition can be an important tool for surgeons, it is not reliable enough to be utilized as a single method for stone identification, suggesting that urologists need to refine their ability to successfully recognize specific stone compositions intraoperatively.

Tunable Enzyme-Assisted Mineralization of Apatitic Calcium Phosphate by Homogeneous Catalysis

While it has long been mimicked by simple precipitation reactions under biologically relevant conditions, calcium phosphate biomineralization is a complex process, which is highly regulated by physicochemical factors and involves a variety of proteins and other biomolecules. Alkaline phosphatase (ALP), in particular, is a conductor of sorts, directly regulating the amount of orthophosphate ions available for mineralization. Herein, we explore enzyme-assisted mineralization in the homogeneous phase as a method for biomimetic mineralization and focus on how relevant ionic substitution types affect the obtained minerals. For this purpose, mineralization is performed over a range of enzyme substrate concentrations and fluoride concentrations at physiologically relevant conditions (pH 7.4, T = 37 °C). Refinement of X-ray diffraction data is used to study the crystallographic unit cell parameters for evidence of ionic substitution in the lattice, and infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) are used for complementary information regarding the chemical composition of the minerals. The results show the formation of substituted hydroxyapatite (HAP) after 48 h mineralization in all conditions. Interestingly, an expansion of the crystalline unit cell with an increasing concentration of the enzyme substrate is observed, with only slight changes in the particle morphology. On the contrary, by increasing the amount of fluoride, while keeping the enzyme substrate concentration unchanged, a contraction of the crystalline unit cell and the formation of elongated, well-crystallized rods are observed. Complementary IR and XPS data indicate that these trends are explained by the incorporation of substituted ions, namely CO32- and F-, in the HAP lattice at different positions.

Review of Physical, Mechanical, and Biological Characteristics of 3D-Printed Bioceramic Scaffolds for Bone Tissue Engineering Applications.

This review focuses on the advancements in additive manufacturing techniques that are utilized for fabricating bioceramic scaffolds and their characterizations leading to bone tissue regeneration. Bioscaffolds are made by mimicking the human bone structure, material composition, and properties. Calcium phosphate apatite materials are the most commonly used scaffold materials as they closely resemble live bone in their inorganic composition. The functionally graded scaffolds are fabricated by utilizing the right choice of the 3D printing method and material combinations to achieve the requirement of the bioscaffold. To tailor the physical, mechanical, and biological properties of the scaffold, certain materials are reinforced, doped, or coated to incorporate the functionality. The biomechanical loading conditions that involve flexion, torsion, and tension exerted on the implanted scaffold are discussed. The finite element analysis (FEA) technique is used to investigate the mechanical property of the scaffold before fabrication. This helps in reducing the actual number of samples used for testing. The FEA simulated results and the experimental result are compared. This review also highlights some of the challenges associated while processing the scaffold such as shrinkage, mechanical instability, cytotoxicity, and printability. In the end, the new materials that are evolved for tissue engineering applications are compiled and discussed.

Formation of Calcium Phosphate Apatite in System CaO-P2O5-H2O: Equilibrium at 298 K Under a Nitrogen Atmosphere

Aims: The formation of calcium phosphate apatite (hydroxyapatite, carbonate-containing hydroxyapatite, fluorapatite and carbonate-containing fluorapatite) in aqueous systems has been studied for over a century. Background: However, in the region of low concentrations of liquid phases, the question of the nature, composition and region of existence of apatite compounds remains controversial. Objective: The results of studying the phase equilibrium in the system CaO-P2O5-H2O at 298 K in the isotherm region from the invariant point of dicalcium phosphate and monocalcium phosphate monohydrate to the lowest concentrations of the liquid phase components are presented. Method: Chemical analysis, thermogravimetry, IR spectroscopy and optical microscopy were used for the analysis. Result: Long-term monitoring of the establishment of equilibrium (up to 20 months) resulted in the determination of regions of stable solid phases of calcium orthophosphates, calcium-deficient apatites, hydroxyapatite, and apatite with (Ca/P)at >1.67. Two types of calcium-deficient apatite were identified that differ in the (Ca/P)at ratio: the first type is 1.33 < (Ca/P)at ≤ 1.5; the second one is 1.5 ≤ (Ca/P)at < 1.67. Conclusion: The invariant points of calcium orthophosphates and compounds with the apatite structure were determined. The diagram was constructed using the Miller-Kenrick method based on obtained experimental data, which confirms the established regions and invariant points of stable equilibrium solid phases of the studied ternary system. The data obtained can be useful for understanding the processes of formation and change of compounds with apatite structure.

SEM-EDX micro-analysis and FTIR infrared microscopy by ATR of a bladder stone from the IIIth millennium BC from the B1S passage-grave of the necropolis in Chenon (Charente, France)

Here is a case of bladder stone of average size dated to the Late Neolithic period, found in the multiple burial of the B1S passage-grave in Chenon (Charente, France). Chemical analysis showed a mixed composition. The core, intermediate and surface envelopes consist in calcium phosphate apatite associated with whitlockite and amorphous carbonated calcium phosphate, all clarified by Fourier Transform InfraRed spectroscopy. Calcium phosphatic stones are characteristic of communities, such as those of the Neolithic period, where the diet was rich in cereal carbohydrates and poor in animal proteins. The excavation of such extra-skeletal objects is an event that is particularly interesting as it provides documents on the history of diseases and diets in ancient populations. The complete set of data suggests that this bladder stone was formed during a urinary tract infection with a germ possessing a very active urease.

Relationship between calcinosis cutis in epidermal necrolysis and caspofungin, a physicochemical investigation

Epidermal necrolysis (EN) is a rare life-threatening condition, usually drug-induced and characterised by a diffuse epidermal and mucosal detachment. Calcinosis cutis is reported in various skin diseases, occurring preferentially with tissue damage, but has never been described in EN. Clinical, biological and histopathological characteristics of three patients were retrospectively obtained from medical charts. Immunohistochemistry of classical osteogenic markers was used to explore the pathogenesis of the calcifications; their chemical composition was determined by μFourier transform infra-red (μFTIR) spectroscopy and their localization and morphology by field-emission scanning electron microscopy (FE-SEM). In a recent letter, part of the results of this investigation has been already presented. In this contribution, we have added original data to this previous letter. We have investigated a set of biopsies corresponding to patients who presented atypical healing retardation due to calcinosis cutis. Through FE-SEM observations at the nanometre scale, we describe different areas where are present voluminous calcifications at the surface, submicrometre spherical entities within the papillary dermis and then large “normal” fibres. FE-SEM observations show clearly that “large” calcifications are the result of an agglomeration of small spherical entities. Moreover, micrometre scale spherical entities are the results of an agglomeration of nanometer scale spherical entities. Finally, the last set of data seems to show that the starting point of the calcifications process is “distant” from the epidermis in part of the dermis which appears undamaged. Regarding the chemical composition of large calcifications, different μFTIR maps which underlined the presence of calcium-phosphate apatite have been gathered. Moreover, histopathology indicates that these pathological calcifications are not induced following a trans-differentiation of the skin cells into an osteochondrogenic phenotype. The association of caspofungin administration, known to induce in vitro intracellular calcium influx, and inflammation, induced by EN, known to favor dystrophic calcifications in various inflammatory skin diseases, could explain this never-before reported occurrence of calcinosis cutis.

Nitrate‐Free Synthesis and Electrospinning of Carbonated Hydroxyapatite Coatings on TA6V Implants

AbstractTA6V (Ti‐6Al‐4V) titanium alloy is commonly used in implantology due to its biocompatibility and interesting mechanical properties. However, its lack of bioactivity is responsible for orthopedic implants loosening, eventually leading to the necessity for a revision surgery. In this study, inorganic coatings are developed with the aim of improving osteo‐integration of TA6V implants. To this end, a carbonated calcium phosphate apatite, already reported to be osteo‐conductive and naturally present in bone tissue, is shaped in the form of micro‐sized filaments, via the electrospinning process, in order to mimic the architecture of the collagen fibrils naturally present in the bone extracellular matrix. The process is then adapted to coat complex, 3D implants. Cellular assays with MG‐63 highlight that cell viability and proliferation are promoted on the coated implant, as a result of both its chemical and morphological properties.

Apical Sealing Ability of Experimental Apatite Calcium Phosphate based Coated Gutta-percha Points

Aims: This study aimed to assess the apical sealing ability of experimental apatite-coated gutta-percha points compared to various coated gutta-percha root filling materials.
 Study Design: Experimental in-vitro study.
 Place and Duration of Study: Department of Restorative Dentistry, University of Malaya, June 2014 and November 2014.
 Methodology: Ninety-six extracted permanent maxillary central incisors were standardized and prepared by ProTaper universal rotary files. The specimens were allocated into six groups (n=15) and filled using matching single cone technique as follows; EndoREZ points with EndoREZ sealer, Bioceramic coated points (BCGP), Active GP (ActiV GP), Conventional gutta-percha (GP), apatite coated GP (HAGP) all in combination with Endosequence BC sealer. The sixth group was filled using cold lateral compaction of Conventional GP and Endosequence BC sealer. The specimens were subjected to a dye leakage test. The remaining six teeth were divided equally to be used as a negative and positive control. One-way analysis of variance (ANOVA) followed by the post hoc Dunnett T3 test was performed for data analysis, and the significance value was set at P =.05.
 Results: ActiV GP had the least leakage followed by BCGP, HAGP, cold lateral compaction, conventional GP, and EndoRez.
 Conclusion: HAGP as root canal filling showed favourable sealing ability comparable to ActiV GP, BCGP, and conventional GP and it was superior to EndoREZ.

Experimental study on the interaction of insulin with apatitic calcium phosphates analogous to bone mineral: adsorption and release

The present work investigated the interaction of human insulin with synthesized poorly crystalline apatitic calcium phosphates containing simultaneously HPO42- and CO32- ions in various amount. The adsorption kinetics is very fast, while the release kinetics is generally slow. The chemical composition of apatite has an influence on both the adsorption and release processes. The experimental results show that the percentage of insulin adsorption and release decreased with the increase of the content of carbonate. The equilibrium adsorption data are fitted into Langmuir, Freundlich, Elovich, Temkin, and Dubinin–Radushkevich isotherms. The Langmuir model is best suited with a maximum monolayer adsorption capacity of 33.20 and 25.08 mg/g at 310 K corresponding to the carbonated and octocalcium phosphate apatite respectively. Isotherms parameters have revealed that the adsorption of insulin on these apatites is a feasible, spontaneous, and exothermic process. Fourier-transforms infrared confirm the fixation of insulin on non-carbonated and carbonated apatite. The adsorption and release of insulin molecules can be well described as an ions exchange-reaction between species in the hydrated layer of apatite and other species in solution. All of these results suggested that apatitic calcium phosphates can be used as systems for insulin delivery.

Enhanced BMP-2-Mediated Bone Repair Using an Anisotropic Silk Fibroin Scaffold Coated with Bone-like Apatite.

The repair of large bone defects remains challenging and often requires graft material due to limited availability of autologous bone. In clinical settings, collagen sponges loaded with excessive amounts of bone morphogenetic protein 2 (rhBMP-2) are occasionally used for the treatment of bone non-unions, increasing the risk of adverse events. Therefore, strategies to reduce rhBMP-2 dosage are desirable. Silk scaffolds show great promise due to their favorable biocompatibility and their utility for various biofabrication methods. For this study, we generated silk scaffolds with axially aligned pores, which were subsequently treated with 10× simulated body fluid (SBF) to generate an apatitic calcium phosphate coating. Using a rat femoral critical sized defect model (CSD) we evaluated if the resulting scaffold allows the reduction of BMP-2 dosage to promote efficient bone repair by providing appropriate guidance cues. Highly porous, anisotropic silk scaffolds were produced, demonstrating good cytocompatibility in vitro and treatment with 10× SBF resulted in efficient surface coating. In vivo, the coated silk scaffolds loaded with a low dose of rhBMP-2 demonstrated significantly improved bone regeneration when compared to the unmineralized scaffold. Overall, our findings show that this simple and cost-efficient technique yields scaffolds that enhance rhBMP-2 mediated bone healing.

Calcified Leg Ulcers in Older Patients: Clinical Description, Morphology, and Chemical Characterization.

Chronic wounds, including leg ulcers, constitute an important medical problem among older patients. Dystrophic calcifications (DC) are associated with a variety of disorders, including leg ulcers. The aim of this study was to report the clinical and biological characteristics of older patients with DC in leg ulcers and to determine the morphology and chemical composition of these calcifications. We conducted a prospective monocentric study in our Geriatric-Wound and Healing ward, Rothschild Hospital, Paris, from January 2018 to December 2019. Patients with leg ulcers were screened for DC by palpation. Patients' clinical, biological, and radiological findings were collected. DC morphology was analyzed using field-emission scanning electron microscopy and chemical composition was analyzed using µFourier transform infra-red spectroscopy and X-ray Fluorescence. Ten (7%) of the 143 patients hospitalized for leg ulcers presented DC. Older patients with DC were more likely to have leg ulcers with venous insufficiency (p = .015), colonized by Pseudomonas aeruginosa (p = .026), with a longer healing evolution (p = .0072) and hypercalcemia (p = .041). Five DC were extracted from ulcers: 2 presented 500 nm lacunar spheres and intermingled fibrils of about 10 nm in diameter, consistent with bacterial and biofilm imprints. DC were always composed of calcium-phosphate apatite and associated to the presence of zinc. Our analyses were consistent with the involvement of microorganisms and inflammatory process in DC formation. Early management of venous insufficiency, treatment of chronic bacterial colonization and use of calcium-solubilizing drugs seem to be rational strategies for calcified leg ulcer management in older patients.

Tb-based silicate apatites showing slow magnetization relaxation with identical parameters for the Tb3+ and Dy3+ counter ions.

Tb-diluted and Tb-rich apatite-type silicates with compositions Y7.75Tb0.25Ca2(SiO4)6O2 and Tb8Ca2(SiO4)6O2, respectively, exhibit field induced multiple slow relaxation of magnetization. The former reveals two slow relaxation paths, the latter only one with a longer relaxation time of several seconds. The relaxation features of the Tb-diluted one are comparable with those of analogue compounds, where Tb is replaced by Dy, as well as with those of a Tb-doped calcium phosphate apatite. The relaxation parameters of the Tb-rich compound virtually match those of the Dy-based analogue Dy8Ca2(SiO4)6O2. The latter represents the first instance of independence of magnetization relaxation on the nature of a paramagnetic rare-earth metal ion in single ion magnet like materials.

In situ techniques for classifying apatite in coal

Calcium phosphate apatite, Ca5 (PO4)3(OH,F,Cl), is a common accessory mineral in coal seams. Although minor, its role in hosting phosphorus (P) and fluorine (F) can reduce the economic viability of coking and thermal coal deposits. Apatite in coal is commonly <50 μm and may have several modes of occurrence. The modes of occurrence investigated as part of this study include apatite infilling small (i.e. less than 30 μm) cell lumens of fusinite and semifusinite macerals (pore-apatite); apatite infilling fractures (fracture-apatite); apatite occurring as discrete crystals in organic layers or in lithic lenses or bands (detrital-apatite); and apatite nodules or encrustations on silicate minerals (encrusting-apatite). However, the small size of the apatite and its intermixed relationship with the coal and other mineral matter precludes separating the apatite from the coal for analysis and has implications for commercial beneficiation. Therefore, this study documents the trialling of different in situ techniques for evaluating the halogens, specifically F, within these different apatite micro-crystals in polished mounts. In general, standards-based, fully quantitative analysis of major and minor elements (including F, Cl) was accomplished using electron probe microanalysis (EPMA). This in conjunction with electron backscatter diffraction was used to evaluate the measured halogen contents for the different apatites and confirmed that all of the apatites are technically fluorapatite with F contents >1 wt%. However, the small crystallite size of the encrusting-apatites and the pits on the polished surface of the detrital-apatites intermixed with the coal layers hindered determining the halogens by this method. Although, all of the apatites in the coals were able to be analysed by infrared spectroscopy, both the combined kaolinite and apatite spectra, and the noise in the spectra at the lower wavelengths hindered evaluating the F in the apatites using this method. Despite these limitations, the findings of this study show that EPMA is probably the most suitable analytical technique for determining the halogen contents of the different modes of apatites in situ in coal pellets. Future work should focus on determining whether the modes of occurrence reflect paragenesis.

Bio-inspired apatite particles limit skin penetration of drugs for dermatology applications

Most treatments of skin pathologies involve local administration of active agents. One issue can however be the partial transcutaneous diffusion of the drug to blood circulation, leading to undesirable effects. In this work, the original use of submicron mineral particles based on bio-inspired calcium phosphate apatite was explored for the first time as drug carriers for favoring topical delivery. The permeation of a model drug across synthetic and biological membranes was investigated in both static and dynamic conditions. Our data show that adsorption of the drug on the apatite particles surface drastically limits its permeation, with lower effective diffusion coefficients (Peff) and smaller total released amounts. The retention of the apatite colloidal particles on porcine ear skin explants surface was demonstrated by combining histological observations and Raman confocal microscopy. All results converge to show that association of the drug to apatite particles favors skin surface effects. These findings point to the relevance of mineral-based particles as drug carriers for local delivery to the skin, and open the way to novel applications of bio-inspired apatites in dermatology. Statement of SignificanceCalcium phosphates (CaP) are major biomaterials in orthopedics and dentistry. Their resemblance to bone mineral allows new applications beyond bone repair, e.g. in nanomedicine. In 2018, a 14-page detailed review (M. Epple, Acta Biomaterialia 77 (2018) 1–14) provided clear facts in favor of the non-toxicity of nanosized CaP as an answer to discussions from EU and US study groups, thus clarifying the path to novel applications of nano CaP. In the present paper, bio-inspired apatite nanoparticles are used for the first time as drug carriers for dermatology for drastically limiting drug transcutaneous permeation and retaining a topical effect. We demonstrate this proof of concept via permeation cell tests, histology, Raman microscopy and photoluminescence after application on porcine ear skin.

A new percentage of biphasic calcium phosphate (BCP) of nanoparticles synthesized directly by hydrothermal process

&lt;p&gt;Apatitic calcium phosphates have a mineral phase close to that of bone and are commonly used as substitutes or fillers in bone surgery. Also, they are used for their excellent biocompatibility and bioactivity. The purpose of this study is to produce directly biphasic calcium phosphate (BCP) from calcium-deficient apatite (CDHA), by the hydrothermal process. The precursors used were calcium acetate (CH&lt;sub&gt;3&lt;/sub&gt;COO)&lt;sub&gt;2 &lt;/sub&gt;Ca, phosphoric acid (H&lt;sub&gt;3&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;) and triethylamine N (CH&lt;sub&gt;2&lt;/sub&gt;CH&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;, the product was calcined at 900°C. The composition phase, morphology, particle size and the molecular structure of the product were studied using these techniques: X-Ray Diffraction techniques, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy, Fourier Transforms Infrared spectroscopy (FT-IR ) to reveal its phase content, Inductively Coupled Plasma-Atomic Emission Spectrometers (ICP-AES), Thermogravimetric analysis, Thermo-Differentials (ATG / ATD). The results showed that the synthesized product is CDHA. It gives after calcination at 900°C, the biphasic calcium phosphate (a mixture of HA + β-TCP). The product is also found with a new percentage and high crystallinity and nanometric size.&lt;/p&gt;

Colloidal Apatite Particles : A Multifunctional Platform in (Nano)Medicine

Calcium phosphate apatites are naturally present in all vertebrates, as a biomineral in teeth and bones. The possibility to prepare synthetic analogs in close-to-physiological conditions allows the development of bio-inspired materials for medical use. While apatite-based biomaterials are extensively developed for bone regeneration, their intrinsic biocompatibility also allows designing original applications as in nanomedicine. In this paper, we will illustrate why colloidal apatite particles can be seen as a multifunctional platform for (nano)medical uses, well beyond bone repair. Retrospective data will be summarized in this mini-review, especially relating to oncology and hematology applications of apatite colloidal particles. Then novel data will be presented, in the field of dermatology and of particle tracking, using Raman confocal microscopy and μPIXE elemental mapping on substituted apatites. By exploiting their exceptional surface and bulk reactivities, colloidal apatite particles appear as robust new comers to nanomedicine, with the capacity to exhibit tailorable functionalities.

Colloidal Apatite Particles : A Multifunctional Platform in (Nano)Medicine

Calcium phosphate apatites are naturally present in all vertebrates, as a biomineral in teeth and bones. The possibility to prepare synthetic analogs in close-to-physiological conditions allows the development of bio-inspired materials for medical use. While apatite-based biomaterials are extensively developed for bone regeneration, their intrinsic biocompatibility also allows designing original applications as in nanomedicine. In this paper, we will illustrate why colloidal apatite particles can be seen as a multifunctional platform for (nano)medical uses, well beyond bone repair. Retrospective data will be summarized in this mini-review, especially relating to oncology and hematology applications of apatite colloidal particles. Then novel data will be presented, in the field of dermatology and of particle tracking, using Raman confocal microscopy and μPIXE elemental mapping on substituted apatites. By exploiting their exceptional surface and bulk reactivities, colloidal apatite particles appear as robust new comers to nanomedicine, with the capacity to exhibit tailorable functionalities.

Development of an apatitic calcium phosphate cements: effect of liquid/powder ratio on the setting time

Calcium phosphate cement (CPC) sets in situ to form resorbable hydroxyapatite with chemical and crystallographic similarity to the apatite in human bones, hence it is highly promising for clinical applications. Among the clinical requirements for calcium phosphate bone cements are initial setting time and final setting time. α-tricalcium phosphate (α-TCP) and hydroxyapatite (HA) were mixed with dicalcium phosphate dehydrate (DCPD) to form the cement powder which is mixed with aqueous solutions of 3% Na 2 HPO 4 .2H 2 O in weight at four different liquid-to‐powder ratios (0.35, 0.40, 0.45 and 0.50 mL/g). The cement powder, on wetting with the medium, formed a workable putty. X-ray diffraction (XRD), Energy dispersive X-ray spectroscopic (EDS) , transmission electron microscope (TEM) and scanning electron microscopy (SEM) techniques were employed to evaluate the phase composition and surface morphology of the cements. The results revealed similar phase composition for all samples before and after soaking in distilled water at 37°C. According to the results, it is shown that almost complete transformation of cements in calcium-deficient hydroxyapatite (CDHA) occur after soaking 7 days in destilled water with nanosized rod-like hydroxyapatite crystals. Also by reducing the L/P ratio from 0.50 to 0.35, initial and final setting times of the CPCs decreased 11 and 10 minutes respectively.