Synthetic Hydroxyapatite Research Articles

Effect of anions on the structural,morphological and dielectric properties of hydrothermally synthesized hydroxyapatitenanoparticles

Synthetic nano hydroxyapatites (HA) have been considered aspotential biomaterials for bone tissue engineering applications because of itsexcellent biological properties. The present work deals with the synthesis of HAnanoparticles from different anion source materials via autoclave assistedhydrothermal method. All the prepared HA nanoparticles were characterized byX-ray diffraction (XRD), Fourier transformation infrared spectra, field emissionscanning electron microscopy, energy dispersive spectra and high resolutiontransmission electron microscopy. The XRD patterns reveal the pure and hexagonalphase structure with smaller crystallite size for HA obtained from variouscalcium salt precursors. HA particles prepared from nitrate precursors showspherical morphology with 32 nm grain size whereas those derived from theacetate, chloride and egg shell precursors respectively show needle-like,irregular and oval morphology. The effect of different anions on the dielectricproperties and alternating conductivity of HA is investigated, as a polarizedsurface can trigger biological reactions. For the particles obtained fromnitrate, acetate, chloride and egg shell precursors respectively give dielectricconstant (εʹ) values of 9.96, 13.22, 9.92 and 10.86 at 5 MHz. The εʹ anddielectric loss (εʹʹ) values for the HA nanoparticles decrease with increase inthe applied frequency as well. The alternating current conductivity valuesconfirm that the as-synthesized HA samples exhibit insulating behavior. In shortthis article provides the various applicability of HA particles inoptoelectronics and drug delivery.Graphic abstract

Characterization of Catla catla and Oreochromis niloticus fish scales derived hydroxyapatite scaffolds for regenerative medicine

Naturally derived biomaterials have been preferred since decades for the tissue regeneration to repair, replace, and improve the tissues/organs functionality. In the present study, the synthesis of raw fish scales derived hydroxyapatite scaffolds (FSHA) was carried out from two fish species namely, Catla (Catla catla) and Tilapia (Oreochromis niloticus). The control were chemically synthesized hydroxyapatite from gradual mixing of Ca(NO3)2 4H2O (0.40 M) and (NH4)2 HPO4 (0.24 M) solutions at room temperature, with maintaining pH at 11 with NH4OH. The raw powder was utilized to develop porous scaffold by using sacrificial template by sintering at 800 °C for two hours. The commercially available hydroxyapatite (sHA) were compared for the study as control. Further all group of powder and scaffold samples were characterized for their physico-chemical properties. The crystallinity and the compound purity, along with the chemical bond analysis were estimated by XRD and FTIR analysis. TGA was carried out to determine the thermal stability of the FSHA when subjected to temperature range 20–1000 °C. The morphological characterization of porosity and elemental composition and existence of other trace elements were carried out FESEM-EDS. The XRD analysis confirmed the synthesis of crystalline hydroxyapatite from fish scales and FTIR data indicated the presence of bonds supporting the cell-biomaterial interaction. The thermal stability of the developed fish scale derived scaffolds showed support towards physiological conditions. Thus, the performed study with the raw fish scales derived hydroxyapatite scaffolds and compared with synthetic hydroxyapatite as standard seems relevant towards the application for tissue regeneration.

Comparison of subcutaneous inflammatory response to commercial and engineered zinc hydroxyapatite implants in rabbits

ABSTRACT Hydroxyapatite (HA) is widely used as a biomaterial for bone repair and metallic prostheses coating. The main limitations of the current commercial synthetic hydroxyapatite compounds include high cost and decreased availability, especially for veterinary medicine purposes. Additionally, it is thought that HA biocompatibility and bioactivity could be enhanced by the addition of metal compounds. The objective of this work was to compare the subcutaneous tissue response of commercial and engineered hydroxyapatite obtained from the bovine femur diaphysis mixed with different concentrations of hexa-hydrated Zinc Nitrate in rabbits. Twenty-Five New Zealand female rabbits were used. Five treatments were done according to HA composition (commercial HA, no Zn-HA, 0.1M Zn, 0.2M Zn, and 0.3M Zn). Each treatment was evaluated at five time-points (8, 15, 30, 60 and 90 days post-implantation). Histopathologic analysis was performed to assess inflammation by polymorphonuclear cells infiltration, neovascularization, and fibrosis. Results obtained in this work suggest that general inflammation decreased after 60 days of implantation regardless of Zn concentration. Fibrosis score was increased in the commercial HP compared to control and Zn-hydrated HA. This paper shows that bovine hydroxyapatite is a biocompatible material regardless of nitrate Zinc concentration and has the same properties of commercial hydroxyapatite.

Controllable Synthesis of Biomimetic Hydroxyapatite Nanorods with High Osteogenic Bioactivity.

The development of biodegradable materials with high osteogenic bioactivity is important for achieving rapid bone regeneration. Although hydroxyapatite (HAp) has been applied as a biomaterial for bone engineering due to its good osteoconductivity, conventional synthetic HAp nanomaterials still lack sufficient osteogenesis, likely due to their high crystallinity and uncontrollable architecture. A design of HAp nanoparticles mimicking bone features may create good microenvironments that promote osteogenesis for rapid bone regeneration. In this study, HAp nanoparticles with a comparatively less crystalline structure and nanorod shapes mimicking biological HAp nanocrystals of natural bone were fabricated using a simple chemical precipitation approach with mild temperature control in the absence of any organic solvents. Transmission electron microscopy (TEM) indicated that HAp nanorods with aspect ratios from 2.0 to 4.4 were synthesized by adjusting the reaction time as well as the reaction temperature. Fourier transform infrared spectroscopy and X-ray diffraction experiments displayed that HAp nanorods prepared at 30 °C (HAp-30 with an aspect ratio of 2.9) had a low crystalline structure and B-type CO32- substitution similar to those of natural HAp originating from bone tissue. The energy-dispersive spectroscopy (EDS) results showed that the Ca/P ratio of HAp-30 was 1.66 ± 0.13. An in vitro biological evaluation against rat bone marrow-derived mesenchymal stem cells indicated that the resulting HAp nanorods had excellent biocompatibility (with an ∼80-fold increase in IC50 compared to that of conventional HAp nanoparticles). Interestingly, the alkaline phosphatase (ALP), alizarin red S, and immunofluorescence staining results all showed that stem cells display an obvious osteogenesis dependence on the HAp nanostructure. Specifically, HAp nanorods with a moderate aspect ratio had the optimal osteogenic capacity (e.g., HAp-30 offered a 2.8-fold increase in ALP expression and a 4-fold increase in OCN expression relative to that provided by irregular HAp at day 14). It is expected that HAp nanorods with controllable architectures and size have potential as a kind of new bioactive bone filler for bone defect repair.

Effects of argon plasma treatment on the osteoconductivity of bone grafting materials.

The osteoconductive properties of bone grafting materials represent one area of research for the management of bony defects found in the fields of periodontology and oral surgery. From a physico-chemical aspect, the wettability of the graft has been demonstrated to be one of the most important factors for new bone formation. It is also well-known that argon plasma treatment (PAT) and ultraviolet irradiation (UV) may increase the surface wettability and, consequently, improve the regenerative potential of the bone grafts. Therefore, the aim of the present in vitro study was to evaluate the effect of PAT and UV treatment on the osteoconductive potential of various bone grafts. The following four frequently used bone grafts were selected for this study: synthetic hydroxyapatite (Mg-HA), biphasic calcium phosphate (BCP), cancellous and cortical xenogenic bone matrices (CaBM, CoBM). Sixty-six serially numbered disks 10 mm in diameter were used for each graft material and randomly assigned to the following three groups: test 1 (PAT), test 2 (UV), and control (no treatment). Six samples underwent topographic analysis using SEM pre- and post-treatments to evaluate changes in surface topography/characteristics. Additionally, cell adhesion and cell proliferation were evaluated at 2 and 72 h respectively following incubation in a three-dimensional culture system utilizing a bioreactor. Furthermore, the effects of PAT and UV on immune cells were assessed by measuring the viability of human macrophages at 24 h. The topographic analysis showed different initial morphologies of the commercial biomaterials (e.g., Mg-HA and BCP showed flat morphology; BM samples were extremely porous with high roughness). The surface analysis following experimental treatments did not demonstrate topographical difference when compared with controls. Investigation of cells demonstrated that PAT treatment significantly increased cell adhesion of all 4 evaluated bone substitutes, whereas UV failed to show any statistically significant differences. The viability test revealed no differences in terms of macrophage adhesion on any of the tested surfaces. Within their limitations, the present results suggest that treatment of various bone grafting materials with PAT appears to enhance the osteoconductivity of bone substitutes in the early stage by improving osteoblast adhesion without concomitantly affecting macrophage viability. Treatment of bone grafts with PAT appears to result in faster osseointegration of the bone grafting materials and may thus favorably influence bone regeneration.

СИНТЕЗ И ИССЛЕДОВАНИЕ ФИЗИКО-ХИМИЧЕСКИХ СВОЙСТВ НАНОРАЗМЕРНОГО ГИДРОКСИАПАТИТА, ДОПИРОВАННОГО КАРБОНАТ- И СИЛИКАТ-АНИОНАМИ

Hydroxyapatite [Ca10(PO4)6(OH)2, HAp] is similar in chemical composition to bone tissue and widely used in clinical practice as a bone graft substitute. However, unmodified HAp has a low rate of resorption and a weak stimulating effect on the growth of new bone tissue. The introduction of carbonate ions into the structure of the HAp significantly affects the mineralization process and increases the rate of osseointegration. Silicon anions (up to 5%) also play an important and positive role, especially in the initial stages of bone matrix formation. In this regard, doping of synthetic hydroxyapatites with carbonate and silicate anions seems promising. This paper presents the results of the physico-chemical analysis of hydroxyapatite (HAp) samples doped with carbonate and silicate anions (CНAp, Si-HAp) synthesized by chemical precipitation in aqueous alkaline solutions. The structure and properties of the obtained samples are characterized using X-ray powder diffraction (XRD, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and infrared spectrometry(IR). It is established that during the precipitation of the solid phase of HAp, a partial of phosphate ions is replaced by carbonate and/or silicate anions. The results show that the synthesized materials have nanoscale-crystallites with needle-shaped (HAp) and/or spherical forms (CНAp, Si-HAp) (12-85.5 nm) and are single-phase. The intrusion of carbonate and silicate anions into the structure of HAp significantly affects their morphology and particle size. This allows to consider CHAp and Si-HAp samples as promising biomaterials for orthopedic and dental prosthetics.

Synthetic hydroxyapatite: a recruiting platform for biologically active molecules

Background and purpose — Targeted delivery of drugs is important to achieve efficient local concentrations and reduce systemic side effects. We hypothesized that locally implanted synthetic hydroxyapatite (HA) particles can act as a recruiting moiety for systemically administered drugs, leading to targeted drug accretion.Methods — Synthetic HA particles were implanted ectopically in a muscle pouch in rats, and the binding of systemically circulating drugs such as zoledronic acid (ZA), tetracycline and 18F-fluoride (18F) was studied. The local biological effect was verified in an implant integration model in rats, wherein a hollow implant was filled with synthetic HA particles and the animals were given systemic ZA, 2-weeks post-implantation. The effect of HA particle size on drug binding and the possibility of reloading HA particles were also evaluated in the muscle pouch.Results — The systemically administered biomolecules (ZA, tetracycline and 18F) all sought the HA moiety placed in the muscle pouch. Statistically significant higher peri-implant bone volume and peak force were observed in the implant containing HA particles compared with the empty implant. After a single injection of ZA at 2 weeks, micro HA particles showed a tendency to accumulate more 14C-zoledronic acid (14C-ZA) than nano-HA particles in the muscle pouch. HA particles could be reloaded when ZA was given again at 4 weeks, showing increased 14C-ZA accretion by 73% in microparticles and 77% in nanoparticles.Interpretation — We describe a novel method of systemic drug loading resulting in targeted accretion in locally implanted particulate HA, thereby biologically activating the material.

A Simple Method to Evaluate the Purity of Synthetic Hydroxyapatite Granules

Using a method based on the spectrophotometric analysis of the liquids remaining after washing ceramic granules, the type of impurity was determined, the wavelength for measuring the impurity was established, and the type of cuvette (polystyrene or quartz) was analyzed. The absorbance of the samples was measured at wavelengths between 190 and 1100 nm. The results showed that both cuvette types are useful; however, the greatest absorbances were detected using quartz ones at low wavelengths around 190 nm. The comparison of absorption spectra from the samples, centrifuged and noncentrifuged, enabled us to define the impurities as small apatite particles.

Hidroksiapatit / seryum oksit kompozitleri: Sinterleme, mikroyapısal, mekanik ve invitro biyoaktivite özellikleri

Effect of cerium oxide (CeO2) additive on the microstructure, mechanical and invitro bioactivity properties of a commercially synthetic hydroxyapatite (HA) was investigated. HA without CeO2 started to decompose at 1100 oC, but the decomposition temperature of the CeO2 added samples decreased up to 900 oC. Decomposition rate of the sintered samples increased as the sintering temperature reached to 1300 oC. It was about 5.8% for monolithic HA, and increased to 11.4% when the CeO2 additive to HA reached to 2.5 wt%. SEM images showed that an excessive grain growth as well as microcracks occured on the surface of monolithic HA when it was sintered at the temperatures than that of 1100 oC. The microcracks were also observed on the surface of HA-CeO2 composites, when they were sintered at 1300 oC. The composite of HA-0.5CeO2 sintered at 1100 oC possess the higher fracture toughness (Kıc) (2.510 ± 0.225 MPam1/2) and the higher compressive strength (152.73 ± 6.31 MPa) compared to other HA-CeO2 composites, and it's mechanical properties are higher than that of monolithic HA at about 2-3 times. In-vitro bioactivity test results showed that apatite layers on the surface of the samples were in the different morphologies.

Assembly Mechanism of Highly Crystalline Selenium-Doped Hydroxyapatite Nanorods via Particle Attachment and Their Effect on the Fate of Stem Cells.

Hydroxyapatite is the main inorganic component of human bone. Synthetic hydroxyapatite and its different modified forms, which have been shown to be biocompatible and osteoconductive, have been widely used in bone tissue engineering. It is still challenging to controllably synthesize hydroxyapatite with a targeted morphology. In this work, we synthesized highly crystalline selenium-doped hydroxyapatite nanorods (SeHAN) via a two-step alcohol thermal method and provided a complete explanation of the synthesis mechanism. Tracing the crystals obtained from the solvated phase to the crystal phase with high-resolution microscopy, the nanorod formation route can be briefly described as follows: as a basic unit, ∼30 nm amorphous apatite initially formed in the first step and partly crystallized in early part of the second step; after a period of alcohol thermal reaction, immature nanorods appeared, which were composed of nanocrystals; finally, immature nanorods transformed into single-crystal nanorods through crystallization by particle attachment. Since few works have focused on the osteogenesis ability of SeHAN, whose antitumor effect has been widely studied, we investigated the influences of SeHAN on rat-bone-marrow-resident mesenchymal stem cells (MSCs). Surprisingly, SeHAN exhibited excellent biocompatibility for MSCs, enhanced their osteogenic differentiation, and inhibited their adipogenic differentiation. This work provides not only a general method to controllably synthesize hydroxyapatite nanorods/SeHAN but also an insight into understanding the hydroxyapatite formation mechanism. The current study also highlights the effects of SeHAN on MSCs that could furnish a significative strategy for manufacturing functional biomaterials for biomedical applications and tissue engineering by enhanced ossification and reduced marrow adiposity.

Development of composites scaffolds with calcium and cerium-hydroxyapatite and gellan gum

Advances in bone defect treatment strategies have been the development of scaffolds. Among the materials used to produce scaffolds, synthetic hydroxyapatite (HAp) can simulate HAp found in human bone tissue and is used in the synthesis of scaffolds. Ion substitutions have been employed to enhance the characteristics of synthesized HAp, among them the ion exchange of Ca2+ ions for Ce3+. Biopolymers, gellan gum (GG), have potentiated the use of HAp acting as structuring agent in the composition. In this study was proposed the synthesis of two new materials, the scaffolds SH, composed by HAp with GG and, the scaffolds SCH composed by Ce-HAp and GG as materials can be potential to apply in bone defects. Scaffolds were characterized by FTIR, XRD, TG/DTG and SEM, and the techniques showed that the HAp phase and biopolymer were present in the scaffolds, besides revealed the porosity. The mechanical test showed that the scaffolds were sufficient strength to be applied as cancellous bone, implying potential for application in bone repair and regeneration.

Secretion of Hematopoietic Niche Signal Molecules under Conditions of Osteogenic Differentiation of Multipotent Mesenchymal Stromal Cells Induced By Relief Calcium Phosphate Coating

Using a multiplex kit the secretion of a number of cytokines, chemokines, and growth factors has been investigated in vitro in a culture of human adipose-derived multipotent mesenchymal stromal cells (hAMMSCs) under conditions of their osteogenic differentiation caused by 14-day contact with a calcium phosphate (CP) surface of different roughness. Bilateral X-ray amorphous CP coatings were prepared on the samples of commercially pure titanium in the anodal regime using a microarc method. The electrolyte consisted of aqueous orthophosphoric acid (20 wt %), calcium carbonate (9 wt %), and synthetic hydroxyapatite nanopowder (6 wt %, particle diameter of 10–30 nm with single agglomerates up to 100 nm). hAMMSCs isolated from lipoaspirate were co-cultured after 4 passages with the CP-coated samples at a final concentration of 1.5 × 105 viable karyocytes per 1.5 mL of standard nutrition medium (without osteogenic stimulators) for 14 days (determination of the [CD45,34,14,20], CD73, CD90, and CD105 cell immunophenotype; analysis of secretory activity) and 21 days (alizarin red S cell culture staining) with medium replacement every 3–4 days. Under conditions of in vitro contact with rough CP coating hAMMSCs differentiated into osteoblasts synthesizing the mineralized bone matrix; this was accompanied by a 2−3-fold increase in the proportion of [CD45,34,14,20]+ hemopoietic cells. The following humoral factors of hemopoietic niches acted as the signal molecules escalating in vitro the hemopoietic base in 14 days of differentiating three-dimensional culture of hAMMSCs: leukemia inhibitory factor (LIF) and stem cell factor (SCF) cytokines in the case of the mean index of CP roughness Ra = 2.4–2.6 µm or stromal derived factor-1 (SDF-1α, CXCL12 chemokine) in the case of Ra = 3.1–4.4 µm.

The impact of graft remodeling on peri‐implant bone support at implants placed concomitantly with transcrestal sinus floor elevation: A multicenter, retrospective case series

To evaluate the impact on peri-implant bone support (as assessed on periapical radiographs) of the remodeling dynamics of varying graft biomaterials used for transcrestal sinus floor elevation (tSFE). The study is a multicenter, retrospective series of cases undergone tSFE (performed according to the Smart Lift technique) and concomitant implant placement. At operator's discretion, tSFE was performed with bone core (BC) alone or supplemented by deproteinized bovine or porcine bone mineral (DBBM and DPBM, respectively), synthetic hydroxyapatite in a collagen matrix (S-HA), or ß-tricalcium phosphate (ß-TCP). Immediately after surgery, at 6-12months post-surgery, and at later (≥24months) follow-up intervals, the percentage proportion of the implant surface in direct contact with the radiopaque area was calculated for the entire implant surface (totCON%). Also, the height of the graft apical to the implant apex (aGH) was assessed. At 6-12months following tSFE, median totCON% was 100%, with a median aGH of 1.4mm. A tendency of aGH to decrease in height was observed at later follow-up intervals for sites treated with all grafting procedures. In all treatment groups, the majority of the implant surface was still surrounded by the radiopaque area at the longest follow-up visits. Although the height of the peri-implant radiopaque area apical to the implant apex tends to reduce overtime at sites which have received tSFE, the peri-implant bone support seems to be maintained long term irrespective of the graft material used.

OSTEOINDUCTIVE POTENTIAL AND BONE HEALING CAPACITY OF NANOCRYSTALLINE HYDROXYAPATITE (nHA)VERSUS BIODENTINE OF SURGICALLY CREATED DEFECTS IN RABBITS’ ALVEOLAR PROCESS (AN ANIMAL STUDY)

Background: Bone defects resulting from trauma, tumor resection, infection, and congenital or acquired deformities remains an important clinical problem. Synthetic nano-crystalline hydroxyapatite, Nano bone, was successfully used in healing of bone defects without revealing negative side effects. Biodentine; a calcium-silicate based material was reported to have osteogenic and angiogenic properties.Objectives: This study aims to investigate the initial osteoinductive potential of Nano Bone and Biodentine on surgically created defects in rabbit’s alveolar process.Methods: 30 adult male rabbits (1-1.5kg) were used in this study. Bilateral bone defects were created in the mandibles of all rabbits, one in each side; the right sides were experimental, and the lefts were kept empty as control. Animals were then divided into two groups (15 rabbits each); Group I (Biodentine): The right-side defects were loaded with Biodentine material. Group II (Nano Bone): Nano Bone was packed in the right-side defects. Five rabbits were euthanized from each group at; 3, 7 and 14 days postoperatively. Bone defects’ specimens were prepared for histological examination by light microscope as well as quantitative analysis of gene expression of collagen1 alpha and Runx-2 by real time PCR.Results: Biodentine had initiated osteogenesis; yet the newly formed bone was apparently of lesser quality than that formed with Nano Bone. Runx- 2 showed significant increase in Nano Bone compared to Biodentine at 1 week, while collagen1 alpha gene expression was significantly increased at all intervals.Conclusion: Both Nano Bone and Biodentine had initiated osteogenesis. Nano bone showed better healing results when compared to Biodentine.

Graft dimensional stability of fibrin rich in platelets and leucocytes associated with synthetic hydroxyapatite in maxillary sinus lift

Graft dimensional stability of fibrin rich in platelets and leucocytes associated with synthetic hydroxyapatite in maxillary sinus lift

Microstructure mechanism of the hydroxyapatite densification process

Hydroxyapatite (HA) is a well-known materials used as biomaterials in various applications. Numerous studied had been done for unlocking the pros and cons of this material. Sintering process has been used for extraction of pure HA that have similar Ca/P ratio to human bone mineral. This study aims to investigate the effect of sintering temperature on the properties of synthetic HA as well as to develop the mechanism of this densification process. Synthetic HA powder (Sigma-Aldrich #04238) was mixed together with binders, namely polyvinyl alcohol (PVA) and polyethene glycol (PEG) in wet mixing condition using ball mill. Pressed HA (15 g, 65 mm x 12 mm) was sintered with temperature ranging from 1000°C to 1200°C with heating rate and cooling rate of 10°C/min. It has been found that, pure HA was obtained when the HA was sintered with temperature ranging from 1000°C to 1200°C. The thermogravimetric analysis showed that there are there were two mass loss stages on the heating process from room temperature to 1250°C; 100-500°C (dehydroxylation) and 680-1080°C (decomposition). From the microstructure data, the mechanism of the densification process of HA was developed.

3D structures of hydroxyapatite obtained from Rapana venosa shells using hydrothermal synthesis followed by 3D printing

In this study, hydroxyapatite (HAp) obtained by hydrothermal synthesis from natural sources (whelk shells of Rapana thomasiana) was compared to synthetic hydroxyapatite (prepared from chemical reagents) and used for 3D printing of HAp-based structures. Rapana thomasiana can be found in Romanian coast of Black Sea. The visceral part of Rapana is used for culinary purposes, but the whelk shell, mainly consisting of CaCO3, remains as biowaste and can be used as a source of Ca for hydroxyapatite synthesis. Synthetic and natural hydroxyapatite nanopowders were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), dynamic light scattering (DLS) method and in vitro tests. XRD and FT-IR have confirmed the formation of nanostructured hydroxyapatite irrespective of the raw material used. Both types of powders were further used for 3D printing of HAp-based structures, which have also been characterized by SEM and in vitro tests. In vitro tests performed on natural HAp disks (made from whelk shell) lack cytotoxicity and were associated with cell viability similar to that for the synthetic hydroxyapatite disk.

Aspergillus fumigatus biofilm formation on different bone substitutes used in maxillary sinus augmentation: an in vitro analysis

BackgroundFungus ball (FB) typically affects healthy adults, and Aspergillus fumigatus is the most frequent etiologic agent: iatrogenic factors represent an important issue in FB pathogenesis. Moreover, a recent study suggested a significant association between the use of anorganic bovine bone as sinus grafting material and subsequent development of FB. The aim of the present investigation is to evaluate in vitro eventual differences in the ability of Aspergillus fumigatus to colonize different bone grafting materials and grow on them as biofilm.FindingsFive different bone substitutes (demineralized bone matrix, anorganic bovine bone, ß-tricalcium phosphate, synthetic nano-hydroxyapatite, and synthetic hydroxyapatite), commonly used in sinus floor augmentation procedures, were inoculated with conidia suspensions of A. fumigatus and incubated at 37 °C for 4 and 8 h, in standardized conditions. Biofilm bound to the different materials underwent quantitative and qualitative analysis by confocal and scanning electron microscopy. A. fumigatus proved to be able to adhere and form biofilm on all the tested bone substitutes. The surface plot representation of the samples displayed some differences in the density of the superficial layer, due to the physical characteristics of the biomaterials. Nevertheless, Kruskal–Wallis test showed no significant differences in biomass amount among the five bone substitutes (p = 0.236 and p = 0.55 after 4 and 8 h adhesion, respectively).ConclusionsAll the bone substitutes normally used in sinus floor augmentation represent a favorable substrate for fungal growth, due to their physical and chemical characteristics. During sinus floor elevation procedures, Schneiderian membrane integrity should be maintained in order to avoid the exposure of the grafting material at the respiratory environment, with potential risks of fungal colonization.

Fixed - bed Column Adsorption Studies Using Synthetic Hydroxyapatite for Pb(II) Removal from Aqueous Solutions

In the present paper, the adsorptive Pb(II) removal from synthetic aqueous solutions using a 2 cm diameter hydroxyapatite column has been studied through column adsorption experiments by varying column depths (1, 2, 3, 4 cm) and flow rate (10, 15, 22.5 mL/min). Different types of synthetic hydroxiapatites have been involved in experiments. Column design parameters such as critical bed depth and adsorption capacity have been determined from experimental studies. The results revealed the effectiveness of synthetic hydroxyapatite porous beads in Pb(II) removal from aqueous synthetic solutions.

Quantitative affinity parameters of synthetic hydroxyapatite and enamel surfaces in vitro

Particulate synthetic hydroxyapatite (HAP) is rapidly gaining importance as a biomimetic agent in oral care products. The prerequisite for an adequate effect of the treatment is an efficient attachment of the HAP particles to the tooth substance. However, quantitative data about the interaction and affinity parameters involved are scarce. The authors used an in vitro approach with standardized bovine tooth enamel surfaces and aqueous dispersions of chemically pure synthetic HAP particles as a model system. Structural characterization of the HAP powder using high-resolution scanning electron microscopy (SEM) shows that the particles are micrometer-sized stable clusters of crystallites that closely resemble the structure of natural enamel. Using SEM image analysis, the authors investigated the influence of HAP particle concentration and particle size on the efficiency of attachment to bovine tooth enamel based on pure mineral–mineral interaction. The results show that both play an important role and can be tailored for optimizing the efficiency of corresponding oral care formulations. The results also reveal the presence of structures resembling mineral bridges at the interfaces between HAP particles and enamel that provide indications for possible interaction mechanisms.