Size Of Hydroxyapatite Crystals Research Articles

The effect of burning on dental tissue: A macroscopic and microscopic investigation

Teeth are considered unique as fingerprints for identification purposes. Their structure and resilience mean they can remain for thousands and millions of years withstanding extreme conditions, including burning. During burning, bones undergo carbonization at approximately 400°C and calcination at approximately 700°C. This study aimed to investigate the effects of carbonization and calcination on dental tissue. It involved nondestructive analyses of 58 extracted human teeth before and after burning, using x-ray diffraction, micro-CT, and high-resolution confocal microscopy. The results revealed that during carbonization, dentin volume decreased in two thirds of the sample, accompanied by crack formation and significant reduction in hydroxyapatite crystal size (p<0.001). During calcination, dentin volume decreased in all teeth, along with a significant deepening of the cracks (p<0.001), while enamel crystal size increased slightly. Initial changes in teeth occurred at lower temperatures than had once been assumed, as indicated by the cracks during carbonization, and there was up to a 36% decrease in dentin volume during calcination, which should be considered when measuring burnt teeth. The results of this research provide new insight into understanding dental tissue response to burning. Thus, dental remains may contribute to the knowledge needed to reconstruct anthropological and forensic scenarios involving burning.

Modeling of Ca/P and deposit size responses of electrodeposited calcium-phosphate coating using full factorial design

PurposeThis study aims to investigate the effect of electrodeposition parameters (i.e. time and voltage) on the properties of hydroxyapatite (HA) coating fabricated on Ti6Al4V surface.Design/methodology/approachA full factorial design along with response surface methodology was utilized to evaluate the main effect of independent variables and their relative interactions on response variables. The effect of electrodeposition voltage and deposition time on HA coatings Ca/P molar ratio and the size of deposited HA crystals were examined by structural equation modeling (SEM). The formation of plate-like and needle-like HA crystals was observed for all experiments.FindingsThe results obtained showed that the higher electrodeposition voltage leads to lower Ca/P values for HA coatings. This is more significant at lower deposition times, where at a 20-minute deposition time, the voltage increased from 2 to 3 V and the Ca/P decreased from 2.27 to 1.52. Full factorial design results showed that electrodeposition voltage has a more significant effect on the size of the deposited HA crystal. With increasing the voltage from 2 to 3 V at a deposition time of 20 min, the HA crystal size varied from 99 to 36 µm.Originality/valueThe investigation delved into the impact of two critical parameters, deposition time and voltage, within the electrodeposition process on two paramount properties of HA coatings. Analyzing the alterations in coating characteristics relative to variations in these process parameters can serve as a foundational guide for subsequent research in the domain of calcium-phosphate deposition for implants.

Formulation and evaluation of alginate-gelatin hydrogel scaffolds loaded with zinc-doped hydroxyapatite and 5-fluorouracil

Alginate and gelatin are natural macromolecules used to formulate biocompatible drug delivery systems. Hydroxyapatite (HA) is an osteophilic ceramic used to prepare bone scaffolds. The current study aimed at preparing and characterizing HA, zinc-doped HA, and 5-fluorouracil(5-FU)-loaded alginate-gelatin-based hydrogel scaffolds using different crosslinking solutions. 5-FU incorporation efficiency, in-vitro drug release, antitumor bioassays, FTIR, X-ray-diffraction (XRD), High-Resolution Transmission, and Scanning-Electron Microscope (HR-TEM and SEM) studies were conducted. XRD showed the incorporation of Zn2+ into HA structure with a deformity in HA crystal lattice and inhibited crystal growth. FTIR-spectra represented the characteristic bands corresponding to HA structure. HR-TEM showed a decreased HA crystal size and rod-like crystallites that increased with increasing zinc content. Zn2+ content and 5-FU-loading caused significant effects on the scaffolds' thickness (p-value = 0.021 and 0.035, respectively). Burst 5-FU release within 10–15 min followed by 100 % release within 4 h was observed. Zinc content showed a significant positive effect on the cytotoxicity% of the blank and drug-loaded scaffolds. XRD and FTIR studies revealed that 5-FU was completely incorporated into the hydrogel with no chemical interaction. SEM-imaging showed interconnected pores and needle-shaped drug particles. The prepared formulations showed promising physico-chemical properties for targeted delivery of 5-FU in the form of biocompatible bone scaffolds.

Microstructure analysis and thermal stability of Mg2+/Sr2+/SO42- ions doped hydroxyapatite bionanomaterials

This study evaluates the influence of the addition of Mg2+, Sr2+, and SO4 2- ions on the microstructure and thermal stability of hydroxyapatite (HA). The materials were calcined at 500 °C and 800 °C for 2 h, then characterized by XRD, FTIR, SEM, EDX, and FTIR techniques. The degree of crystallinity and crystallite size of HA crystals were significantly decreased with the incorporation of Mg2+/Sr2+/SO4 2- ions. While the lattice parameters were reduced due to the substitution of ions, The high incorporation of Mg2+ ions lowered the thermal stability of HA. At the same time, the addition of Sr2+ ions enhanced thermal stability. A similar impact on phosphate bands was seen in FTIR results. HA existed in spherical nanoparticles; incorporating Mg, Sr, and S ions doesn’t change the particle shape.

Effect of simulated body fluid formulation on orthopedic device apatite-forming ability assessment.

Integration of native bone into orthopedic devices is a key factor in long-term implant success. The material-tissue interface is generally accepted to consist of a hydroxyapatite layer so bioactive materials that can spontaneously generate this hydroxyapatite layer after implantation may improve patient outcomes. Per the ISO 22317:2014 standard, "Implants for surgery - In vitro evaluation for apatite-forming ability of implant materials," bioactivity performance statements can be assessed by soaking the material in simulated body fluid (SBF) and evaluating the surface for the formation of a hydroxyapatite layer; however, variations in test methods may alter hydroxyapatite formation and result in false-positive assessments. The goal of this study was to identify the effect of SBF formulation on bioactivity assessment. Bioglass® (45S5 and S53P4) and non-bioactive Ti-6Al-4V were exposed to SBF formulations varying in calcium ion and phosphate concentrations as well as supporting ion concentrations. Scanning electron microscopy and X-ray powder diffraction evaluation of the resulting hydroxyapatite layers revealed that SBF enriched with double or quadruple the calcium and phosphate ion concentrations increased hydroxyapatite crystal size and quantity compared to the standard formulation and can induce hydroxyapatite crystallization on surfaces traditionally considered non-bioactive. Altering concentrations of other ions, for example, bicarbonate, changed hydroxyapatite induction time, quantity, and morphology. For studies evaluating the apatite-forming ability of a material to support bioactivity performance statements, test method parameters must be adequately described and controlled. It is unclear if apatite formation after exposure to any of the SBF formulations is representative of an in vivo biological response. The ISO 23317 standard test method should be further developed to provide additional guidance on apatite characterization and interpretation of the results.

High crystalline hydroxyapatite coating by eclipse type pulsed-laser deposition for low annealing temperature

The eclipse type pulsed-laser deposition (PLD) scheme as a droplet-eliminated method with irradiation on a β-tricalcium phosphate (β-TCP) slab target was employed to achieve high density without holes, high purity, and high crystallinity hydroxyapatite (HAp) coating on a zirconia substrate with a low annealing temperature under an H2O vapor pressure. An obstacle ball was set between the target and the substrate so that ablated droplets would collide with the ball and be eliminated, while other ablated atoms went around the ball and were deposited on the substrate. A flat, transparent, and high-density coating layer was deposited on the substrate in an H2O vapor atmosphere at 0.1 Torr for different substrate surface temperatures from 20 °C to 650 °C. The phase of the coating layers was significantly changed from amorphous calcium phosphate to crystalline HAp when the temperature was set to over 360 °C, as determined from Raman microscopy measurements. Raman spectroscopy also showed that the HAp crystal size became larger as the temperature was increased to over 360 °C. It was concluded that the eclipse type PLD method with irradiation on a β-TCP target would improve the quality of HAp coatings and allow effective lowering of the annealing temperature.

Effect of theobromine based dental varnish on the enamel surface microhardness- an in vitro study

Introduction: Theobromine in recent years has been used as a remineralization agent. It demonstrates increased enamel hydroxyapatite crystal size that strengthens the enamel thus making it resistant to acid attack. Hence in the present study theobromine-based dental varnish was developed and its effect on enamel surface microhardness was assessed. Methods: In this in-vitro study, 45 freshly extracted healthy human first premolar teeth were randomly allocated into three groups of 15. Group 1 was Placebo varnish, Group 2 was Standard 5% Sodium fluoride varnish which was commercially available, and Group 3 was Novel theobromine nanoparticles containing dental Varnish. The enamel blocks were prepared from the randomly selected teeth. Baseline surface microhardness of the prepared enamel blocks were measured at three different points on the polished surface using both Vickers hardness tester and nano-indentation hardness tester. The prepared enamel blocks were immersed in a demineralizing solution for 7 days. At the end of the 7th day, the enamel blocks were removed and cleaned thoroughly. Again, the enamel blocks microhardness was recorded. After demineralization, all the enamel blocks were treated with three different varnishes for 28 days. After the 28th day, the readings were recorded using both Vickers hardness tester and nano-indentation hardness tester again. The results were analyzed by one-way analysis of variance (ANOVA), repeated measures ANOVA, and Bonferroni’s post hoc analysis. Results: The mean enamel surface microhardness between the three groups at baseline (P>0.001) and after demineralization (P>0.001) were not statistically significant whereas after application of dental varnishes the mean enamel surface microhardness values showed significant differences between the groups (P<0.001). Group 3 showed significantly more enamel surface microhardness values after its application on demineralized enamel surface as compared to Group 1 and Group 2 respectively. Conclusions: Theobromine nanoparticles containing dental varnish can significantly increase the enamel surface microhardness after its application on the demineralized early white spot lesion. Keywords: Theobromine, Remineralization, Nanoparticles, Surface microhardness

The amelioration of T2DM rat femoral bone achieved by anti-osteoporosis of caprine CSN1S2 protein through bone morphogenetic protein signaling pathway.

We investigated the potential anti-glycation and anti-osteoporosis properties of Caprine milk CSN1S2 protein on the serum AGEs and sRAGE level, osteogenic factors expressions, femoral bone mesostructure, histomorphometry, and hydroxyapatite crystals changes in T2DM rats. Varying doses of Caprine milk CSN1S2 protein (0, 375, 750, and 1500 mg/kg BW) were used to treat the control and T2DM rats. We measured AGEs and sRAGE level; RUNX2, OSX, BMP2, and Caspase-3 expressions in rats using ELISA and immunohistochemistry, respectively. The mesostructure and histomorphometry of femoral bone was analyzed using SEM Microscope and BoneJ software, then hydroxyapatite crystal size was determined using SEM-XRD. T2DM rats showed a high level of AGEs and a low level of sRAGE, the RUNX2, OSX, and BMP2 expression was down regulated, BV, BV.TV, Tb.Th, Tb.Sp, increased and SMI levels declined, respectively. Vice versa, after administration of the CSN1S2 protein to T2DM rats, improvement in all levels of molecular and cellular markers was achieved. In the CSN1S2 highest dose, AGEs level declined and sRAGE level elevated in T2DM rats. The 375 and 750 mg/kgBW of CSN1S2 protein was able to upregulate the RUNX2, OSX, and BMP2 expression in T2DM rats, thus improving the normalization of osteoclasts and osteoblasts number. The whole dose of CSN1S2 triggered the thickening of trabecular bone wall, granule formation, and normalized the trabecular thickness (Tb.Th) parameter of T2DM rats. The hydroxyapatite crystal size was increased in the highest dose of CSN1S2-treated T2DM rats. This study indicated that CSN1S2 protein had a protective effect against osteoporosis in the T2DM rat bones by means of glycation pathway inhibition, bone histomorphometry and mesostructure improvement via bone morphometric protein signaling.

The development of a tool to predict temperature-exposure of incinerated teeth using colourimetric and hydroxyapatite crystal size data.

This study presents a novel tool to predict temperature-exposure of incinerated pig teeth as a proxy for understanding impacts of fire on human teeth. Previous studies on the estimation of temperature-exposure of skeletal elements have been limited to that of heat-exposed bone. This predictive tool was developed using a multinomial regression model of colourimetric and hydroxyapatite crystal size variables using data obtained from unheated pig teeth and teeth incinerated at 300 °C, 600 °C, 800 °C and 1000 °C. An additional variable based on the observed appearance of the tooth was included in the tool. This enables the tooth to be classified as definitely burnt (600°C-1000 °C) or uncertain (27 °C/300 °C). As a result, the model predicting the temperature-exposure of the incinerated teeth had an accuracy of 95%. This tool is a holistic, robust and reliable approach to estimate temperature of heat-exposed pig teeth, with high accuracy, and may act as a valuable proxy to estimate heat exposure for human teeth in forensic casework.

Succinic acid and apatite world in producing thin plate-shaped Nanocrystals

Octacalcium phosphate (OCP) crystal is composed of apatite having general formula Ca5(PO4)3X, where X=F, Cl or OH and they are key component of bone and teeth, where its hydrated layers producing thin plate-shaped hydroxyapatite (HAP) nanocrystals. Here, we have been reported the synthesis of sample of HAP nanocystals as CALPHOS or CONTROL and SUC or Suc-20 under hydrothermal condition from succinic acid’s ion based OCP at 180 0C for 3hours. During incorporating of succinate ions in OCP crystals the hydrogen phosphate (HPO42-) ions in the hydrated layers of OCP are being substituted by succinate ions. Since, HAP crystal system is hexagonal and it characterized by using of SEM, XRD and FTIR technique. The crystallite size of HAP crystals are as perpendicular to the (100) plane which can calculate by using as D100 = Kλ/(β cos θ) equation of Scherrer.

Composition and characteristics of trabecular bone in osteoporosis and osteoarthritis.

Bone strength depends on multiple factors such as bone density, architecture and composition turnover. However, the role these factors play in osteoporotic fractures is not well understood. The aim of this study was to analyze trabecular bone architecture, and its crystal and organic composition in humans, by comparing samples taken from patients who had a hip fracture (HF) and individuals with hip osteoarthritis (HOA). The study included 31 HF patients and 42 cases of HOA who underwent joint replacement surgery between 1/1/2013 and 31/12/2013. Trabecular bone samples were collected from the femoral heads and analyzed using a dual-energy X-ray absorptiometry, micro-CT, and solid-state high-resolution magic-angle-spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. No differences in proton or phosphorus concentration were found between the two groups using 1H single pulse, 31P single pulse, 31P single pulse with proton decoupling NMR spectroscopy, in hydroxyapatite (HA) c-axis or a-axis crystal length. Bone volume fraction (BV/TV), trabecular number (Tb.N), and bone mineral density (BMD) were higher in the HO group than in the HF group [28.6%±10.5 vs 20.3%±6.6 (p=0.026); 2.58mm-1±1.57 vs 1.5mm-1±0.79 (p=0.005); and 0.39g/cm2±0.10 vs. 0.28g/cm2±0.05 (p=0.002), respectively]. The trabecular separation (Tp.Sp) was lower in the HO group 0.42mm±0.23 compared with the HF group 0.58mm±0.27 (p=0.036). In the HO group, BMD was correlated with BV/TV (r=0.704, p<0.001), BMC (r=0.853, p<0.001), Tb.N (r=0.653, p<0.001), Tb.Sp (-0.561, p<0.001) and 1H concentration (-0.580, p<0.001) in the HO group. BMD was not correlated with BV/TV, Tb.Sp, Tb.Th, Tb.N, Tb.PF, 1H concentration or HA crystal size in the HF group. Patients with HO who did not sustain previous hip fractures had a higher femoral head BMD, BV/TV, and Tb.N than HF patients. In HO patients, BMD was positively correlated with the BV/TV and Tb.N and negatively correlated with the femoral head organic content and trabecular separation. Interestingly, these correlations were not found in HF patients with relatively lower bone densities. Therefore, osteoporotic patients with similar low bone densities could have significant microstructural differences. No differences were found between the two groups at a HA crystal level.

EFFECTS OF POLYASPARTIC ACID ON REMINERALIZATION OF INTRAFIBRILLAR DENTIN AND SIZE OF HYDROXYAPATITE CRYSTALS

Objective: The objective of this study was to analyze the intrafibrillar remineralization process and the size of hydroxyapatite crystals formed.Methods: The samples were divided into four groups. The control group was immersed in a demineralization solution, whereas the remaining threetreatment groups were immersed in a remineralization solution containing polyaspartic acid for 3, 7, or 14 days. The effect of polyaspartic acid onintrafibrillar remineralization during the polymer-induced liquid-precursor (PILP) process was evaluated using transmission electron microscopy,and the size of hydroxyapatite crystals was examined through X-ray diffraction.Results: Significant differences were detected in the intrafibrillar remineralization between the treatment groups (subjected to remineralization for3, 7, and 14 days) and the demineralized dentin control group. However, no significant differences were detected in the size of hydroxyapatite crystalsbetween the control and the treatment groups.Conclusion: Our data suggest that polyaspartic acid enables intrafibrillar remineralization during the PILP process.

A comparison of crystal structure in fresh, burned and archaic bone – Implications for forensic sampling

Standard protocols for extracting DNA from bone are variable and are largely dependent on the state of preservation. In archaic samples, endogenous DNA is believed to be tightly bound to crystal aggregates in the Hydroxyapatite (HAp) matrix requiring prolonged demineralisation to allow its release. By comparison, fresh bone contains abundant cellular material, discounting the need for demineralisation. Recommendations for incinerated bone, specifically how viable sampling sites should be selected and the ideal techniques for DNA recovery are unclear, and the protocol used is often selected based on macroscopic sample appearance.It has been postulated that like archaic bone, burned bone is ‘highly degraded’ and therefore aDNA techniques may present better results for DNA recovery than using fresh protocols. However, little research has been undertaken comparing the crystal structure of burnt, fresh and archaic bone. This study uses a combination of XRPD and SEM analysis to compare the crystalline profile and microscopic appearance of burned bone subjected to temperatures ranging from 100–1000°C, with archaic and fresh samples. Although macroscopically visually different, fresh samples and samples heated up to 500°C showed no microscopic differences or significant changes in crystallinity. By comparison, samples heated above 500°C became significantly more crystalline, with HAp crystal size increasing dramatically. Archaic samples were different again, more closely resembling the amorphous fresh samples than the highly crystalline incinerated samples. These results suggests that, potentially, samples burned at 500°C or lower can be treated as fresh samples, whilst samples exposed to higher temperatures may require adapted protocols. Whether or not these highly burned samples require demineralisation needs to be investigated.

Synthesis and size evolution of 1D hydroxyapatite crystals under surfactant-free hydrothermal conditions

Hydroxyapatite nanoparticulate materials have received a great deal of scientific attention due to their dental and orthopedic applications but simple strategies to control particle characteristics (e.g., surface area, shape and size distribution) are still needed. Among several hydroxyapatite structures, one-dimensional nanoscale materials such as nanowires, nanorods and nanobelts can be synthesized in the presence of specific surfactants added during synthesis in order to alter the particle growth. This contribution is aim to explore strategies to obtain one dimensional hydroxyapatite crystals without the use of surfactants. Particularly, we study the effect of several variables such as temperature, reaction time and pH on shape and size of hydroxyapatite crystals produced under hydrothermal conditions. The results obtained show the formation of hydroxyapatite nanorods as well as some interesting insights about how to control particle sizes in samples obtained at temperatures between 180 °C and 220 °C. These results have potential benefits at the time of producing one dimensional hydroxyapatite crystals in a simple and not expensive way.

A hydrothermal synthesis of natural hydroxyapatite obtained from Corbicula moltkiana freshwater clams shell biowaste

In this study, the natural hydroxyapatite (HA) has been obtained from Corbicula moltkiana shell (CS), which are available as waste from local food processing. The shell can be used as an inexpensive source of natural HA providing at the same time to give added value to food processing by-products as well as reducing the undesirable environmental impact. The synthesized natural HA have been characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), X-ray Fluorescence (XRF) spectrometer and transmission electron microscopy (TEM) studies. The XRD peaks were in agreement with the standard JCPDS file (ICSD-157481). The material obtained at 900 and 1000 °C (HA 900 and HA 1000) have a low crystallinity of hydroxyapatite. At 1000 °C, a tetracalcium phosphate (TTCP) peak was observed. In addition, the crystal size of HA calculated from XRD pattern was found to be a nanosized crystal of 28.90 nm and 6.31 nm for HA 1000 and HA 900 respectively.

Hydrothermal synthesis of nanocrystalline hydroxyapatite from phosphogypsum waste

Hydroxyapatite (HAp) nanorods are synthesized from phosphogypsum waste (PG) and potassium dihydrogen phosphate (KH2PO4) under hydrothermal conditions. The influence of several synthesis parameters such as temperature (100–200 °C), synthesis time (1–15 h), and solution pH (5–11) on product structure and purity is addressed by X-ray diffraction and Fourier Transformed-Infrared Spectroscopy. Phase-pure HAp nanorods with diameter and length of 18 and 63 nm, respectively, are obtained after 10 h at 200 °C and pH ∼ 11. The influence of Brij-93 surfactant on the morphology of prepared HAp is investigated by transmission and scanning electron microscopy. The aspect ratio and the mean size of HAp crystals increase to 1013 and 205 × 20 nm, respectively, with increasing the concentration of Brij-93 surfactant to 0.01 mol. Hence, the PG recycling could be accomplished using an easy synthesis route with relatively cheap reactants for the production of nanocrytalline HAp.

Temperature Affects the Hydroxyapatite Crystal Arrangement on Silk Fibroin Surfaces

A hydroxyapatite (HAP)/silk fibroin (SF) bone-like biomaterial was fabricated through a coprecipitation process using stepped temperatures. We evaluated the effect of increasing temperatures on hydroxyapatite crystal arrangement on a silk fibroin surface. We found that the HAP crystal particles self-assembled on the silk fibroin surface. Further we found that with rising temperature the HAP crystal c-axis became progressively more parallel to the long axis of the silk fibroin. This deposition pattern is similar to that seen with HAP and collagen assembly in normal bone. Based on the XRD, SEM, and TEM results, we conclude that higher temperatures promote crystal nucleation resulting in an increase in both HAP crystal size and HAP/SF particle size. These data support the use of HAP/SF bone-like biomaterials for bone replacement and regeneration.

Characterization and corrosion behavior of graphene oxide-hydroxyapatite composite coating applied by ultrasound-assisted pulse electrodeposition

Abstract Hydroxyapatite (HA) coating reinforced with graphene oxide (GO) had been developed for getting rid of restrictions associated with its brittleness. This study introduced a promising method of ultrasound-assisted pulse electrodeposition to fabricate the GO-HA coating on the anodized heat-treated surface of titanium. The SEM images indicated that the combined effect of employing ultrasonic waves and GO as a second mechanically resistant phase resulted in the formation of a fine and compact microstructure for the HA-based coating. The EDS elemental maps and micro-Raman spectra showed that the ultrasonic power of 60 W was more effective to incorporate the GO sheets into the coating. However, aggressive agitation of electrolyte with increasing the power to 100 W limited the electrocrystallization of HA crystals in some regions of the surface. The results of nanoindentation test demonstrated the highest nano-hardness (3.08 Gpa) and elastic modulus (41.26 Gpa) for the GO-HA coating prepared by the ultrasound-assisted method. The EDS and FTIR analyses revealed that both the GO sheets and highly reactive OH · radicals produced during the water sonolysis had a positive influence on the mineralization of HA phase. In addition, the pore size distribution diagrams calculated from the N 2 adsorption-desorption isotherms indicated a decrease in the pore size of HA crystals for the electro-co-deposited GO-HA sample. Finally, anodizing/heat-treatment process and the incorporation of GO sheets into the coating led to a significant improvement in the corrosion protection of titanium.

Hydroxyapatite formation from calcium carbonate single crystal under hydrothermal condition: Effects of processing temperature

Hydrothermal processing has been used for synthesis of hydroxyapatite (HAp) crystals with unique morphologies. Our previous studies reported that the morphology of HAp was affected by dissolution behavior of starting materials under a hydrothermal condition. In this study we evaluated the effects of processing temperature on formation and morphology of HAp crystals under a hydrothermal condition. Calcite (CaCO3) single crystal as a starting material was hydrothermally treated in a phosphate solution at various temperatures. After hydrothermal processing for 24h, needle-shaped HAp crystals formed on the surfaces of all the samples. The size of HAp crystals increased with increasing the processing temperature. Plate-shaped HAp was observed on the cross-section of the starting material treated at 200°C. The structure of HAp plates were generated by arrangement of needle-shaped HAp crystals during their crystal growth. The difference in the processing temperature affects the morphology and structure of HAp formed on the starting material under the hydrothermal condition.

Bioinspired synthesis of hydroxyapatite nanocrystals in the presence of collagen and l-arginine: Candidates for bone regeneration.

This work aims at the bioinspired synthesis of hydroxyapatite (HAp) crystals in the presence of both collagen and l-arginine, in an effort to obtain a homogeneous hybrid material, having a bone-like nanostructure. Collagen (Col) is the most commonly utilized protein in most species of life, while L-arginine (Arg) encourages cell attachment, proliferation, and differentiation on HAp surfaces. Transmission electron microscopy, X-ray diffraction and Fourier transform-infrared spectroscopy were used to analyze surface morphology and structure of nanocrystals obtained under different synthesis conditions. It was shown that collagen and arginine content affect HAp crystallization. Collagen has an inhibition effect since HAp crystal size is reduced with the increase of collagen content. The presence of arginine is crucial as a critical content exists (Ca(2+):Arg = 1:1) under which HAp nanocrystals coexist with brushite. Under the optimum synthesis conditions (HAp/Col weight ratio 70/30 and Ca(2+):Arg molar ratio 1:1) HAp nanoplates of a uniform size (around 10 × 10 nm) were obtained. The biocompatibility of this hybrid powder was assessed using human bone marrow derived mesenchymal stem cells (MSCs). Cell response in terms of MSC attachment (scanning electron microscopy) and viability/proliferation (Alamar Blue) demonstrated a noncytotoxic effect of the new material.