Size Of Hydroxyapatite Nanoparticles Research Articles

Role of strontium substitution in spray drying of hydroxyapatite: A comparative study on physical properties

AbstractSpray drying (SD) has the ability to tailor granule size and morphology, thus, it is used for producing hydroxyapatite (HA) granules. Recently, Sr functionalized HA (SrHA) has been recommended owing to its improved biological properties. The aim of this article was to produce SrHA granules with the combination of nanoparticle synthesis and spray‐drying. The effects of substitution on the physical properties of SrHA nanoparticles and spray‐dried granules were investigated. TEM analyzes revealed that Sr substitution reduced the mean size of HA nanoparticles from 4.59 nm to 2.31 nm. Besides, Sr substitution increased the viscosity of the prepared slurry for spray drying, which may be attributed to the smaller nanoparticle sizes. The reduced nanoparticle size caused to the agglomeration of the SrHA more than the pure HA nanoparticles. Moreover the 16 mol % Sr substituted HA (16SrHA) slurry were quickly hardened, which hampered the feeding of the slurry to the SD system; eventually the atomizer was blocked. The increase in the viscosity increased the mean granule size of HA from 41.53 µm to 49.18 µm. HA and 8SrHA granules presented HA phase dominantly after the heat treatment at 1000°C, while, 16SrHA decomposed to TCP according to RAMAN and XRD investigations.

Antimicrobial Activity of New Materials Based on Lavender and Basil Essential Oils and Hydroxyapatite

This study presents, for the first-time, the results of a study on the hydrodynamic diameter of essential oils (EOs) of basil and lavender in water, and solutions of EOs of basil (B) and lavender (L) and hydroxyapatite (HAp). The possible influence of basil and lavender EOs on the size of hydroxyapatite nanoparticles was analyzed by Scanning Electron Microscopy (SEM). We also investigated the in vitro antimicrobial activity of plant EOs and plant EOs hydroxyapatite respectively, against Gram-positive bacteria (methicillin-resistant Staphylococcus aureus1144 (MRSA 1144) and S. aureus 1426) and Gram-negative bacteria (Escherichia coli ATCC 25922 and Escherichia coli ESBL 4493). From the autocorrelation function, obtained by Dynamic Light Scattering (DLS) measurements it was observed that basil yielded one peak at an average hydrodynamic diameter of 354.16 nm, while lavender yielded one peak at an average hydrodynamic diameter of 259.76 nm. In the case of HAp nanoparticles coated with basil (HApB) and lavender (HApL) essential oil, the aggregation was minimal. We found that the lavender EO exhibited a very good inhibitory growth activity (MIC values ranging from <0.1% for E. coli reference strain to 0.78% for S. aureus strains). The biological studies indicated that HapL material displayed an enhanced antimicrobial activity, indicating the potential use of HAp as vehicle for low concentrations of lavender EO with antibacterial properties. Flow cytometry analysis (FCM) allowed us to determine some of the potential mechanisms of the antimicrobial activities of EOs, suggesting that lavender EO was active against E. coli by interfering with membrane potential, the membrane depolarization effect being increased by incorporation of the EOs into the microporous structure of HAp. These findings could contribute to the development of new antimicrobial agents that are urgently needed for combating the antibiotic resistance phenomena.

Effect of alginate as polymer matrix on the characteristics of hydroxyapatite nanoparticles

Hydroxyapatite (HA) nanoparticles were prepared in the presence of alginate, which exhibited spherical shapes. The size of HA nanoparticles decreased with increasing the content of alginate. The HAs synthesized in the presence of alginate agglomerated, leading to the formation of the secondary particles with a size of hundreds nanometer and very narrow size distribution. Thermal treatment also affected the aggregation behavior and particle shape of HAs. The mixture of spherical and rod-like nanoparticles was observed by thermal treatment at 600°C. FT-IR, XRD and XRF analyses confirmed that the stoichiometric HA nanoparticles could be synthesized with using alginate, in which the Ca/P molar ratio was ranged from 1.74 to 1.68. These HA nanoparticles showed the same crystalline phase with that of the stoichiometric HA after thermal treatment. In addition, the content of alginate contained in the products could affect the initial deposition rate of bone-like apatite on the surface of HA nanoparticles.

High Throughput Methodology for Continuous Preparation of Hydroxyapatite Nanoparticles in a Microporous Tube-in-Tube Microchannel Reactor

A microporous tube-in-tube microchannel reactor (MTMCR) was successfully adopted to prepare hydroxyapatite (HAP) nanoparticles. The rodlike HAP nanoparticles with a mean size of 58 nm, a specific surface area of 49.32 m2/g, and a narrow size distribution were obtained in an MTMCR under a high throughput of 3 L/min. The mean particle size sharply decreased with increasing the continuous phase flow rate, while first decreased and subsequently increased with increasing the dispersed phase flow rate and the reactant concentration. The extension of the mixing distance led to the initial rapid and following slight decrease of the mean particle size. The size of HAP nanoparticles was also strongly dependent on the micropore size on the surface of inner tube. Small micropore size was beneficial for producing small particles. For comparison, HAP nanoparticles were also prepared in a stirred tank reactor (STR) and a T-junction microchannel reactor (TMCR), clearly exhibiting the advantages of the MTMCR over the STR ...

Size-mediated cytotoxicity and apoptosis of hydroxyapatite nanoparticles in human hepatoma HepG2 cells

Hydroxyapatite nanoparticles (HAPN) have been discovered to exert cytotoxicity and apoptosis-induction in some cancer cells. But it is still not clear how tumor cells interact with HAPNs with various sizes. In this study, we investigated the effect of the particle size of the HAPN on the anti-tumor activity, apoptosis-induction and the levels of the apoptotic signaling proteins in human hepatoma HepG2 model cells. HAPNs within 20–180 nm size range were synthesized by a modified sol–gel method. The cellular internalization and biolocalization of the FITC-labeled HAPNs were also identified. The results showed that in HepG2 cells, the anti-tumor activity and HAPN-induced apoptosis strongly depended on the size of HAPNs, and the efficacies all decreased in the order of 45-nm > 26-nm > 78-nm > 175-nm. HAPNs, ranging from 20 nm to 80 nm, were found to effectively activate caspase-3 and -9, decrease the Bcl-2 protein level, and increase the levels of Bax, Bid and the release of cytochrome c from mitochondria into cytoplasm, with the best efficiency from 45-nm HAPN. Correlating the cellular response with the cellular internalization, it can be inferred that the size of HAPN and thereby the cellular localization had predominant effect on the HAPN-induced cytotoxicity, apoptotis, and the levels of the apoptotic proteins in HepG2 cells. The findings presented here could provide new means to modulate the cellular behaviors of HAPN and to guide the design of HAPN-based delivery and therapeutic systems.

Preparation and application of hydroxyapatite(HA) nanoparticles/NR2B-siRNA complex

Hydroxyapatite(HA) nanoparticles were prepared by coprecipitation-hydrothermal synthesis and their exosyndrome was estimated via transmission electron microscopy. Agarose gel electrophoresis and ultraviolet spectrophotometry were used to evaluate the ability of HA to bind NR2B-siRNA at different pH values and at different HA:NR2B-siRNA ratios. And the stability of the complex in saline was also evaluated. The effect of HA/NR2B-siRNA complex on chronic inflammatory pain was evaluated in vivo in mice. Transmission electron microscopy(TEM) reveals that HA nanoparticles are thin strips or short rod in shape and the one-dimensional particle size of HA nanoparticles is 40–50 nm. Under the acid or neutral condition, the Zeta potential of HA is positive; nanoparticles can completely bind NR2B-siRNA when the HA:NR2B-siRNA ratio is at or larger than 35:1; while under the alkaline condition, the affinity of HA to NR2B-siRNA is rather weak. HA/NR2B-siRNA complex is not dissociated when being resuspended in saline. The nociception of the tonic phase induced by formalin is significantly reduced in the HA/NR2B-siRNA treated mice as compared with the controls. Therefore, HA may be a new siRNA nano-vector material.

Controlled size and morphology of EDTMP-doped hydroxyapatite nanoparticles as model for 153Samarium-EDTMP doping

Hydroxyapatite (HA) nanoparticles have been studied as nano-sized carriers for the delivery of therapeutic agents. One important consideration for these carriers to be used effectively is their bio-distribution in vivo, of which particle size has a significant effect. In this work, HA nanoparticles doped with Ethylene-diamine-tetramethylene-phosphonate (EDTMP) were synthesized via co-precipitation as a model for HA doped with (153)Samarium ((153)Sm) EDTMP. EDTMP has high affinity for radioactive (153)Sm isotopes that can emit both gamma and beta radiation. The effects of synthesis temperature, amount of dopant and hydrothermal treatment on the size of HA-EDTMP nanoparticles were therefore studied. The results showed that the EDTMP ligand was successfully incorporated in the nanoparticles without changing the crystal structure as shown from X-ray diffractometer (XRD) analysis. From the Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) micrographs, it was observed that shorter rod-like nanoparticles, obtained at low synthesis temperatures, became elongated needle-like nanoparticles with increasing temperature. Increasing dopant amount by five fold increases particle size slightly, while a two fold increase in dopant amount has no significant effect. Hydrothermal treatment increases particle crystallinity and results in smooth elongated rod-like structures. The size of HA nanoparticles doped with EDTMP can therefore be manipulated by controlling synthesis temperature and through hydrothermal treatment.

Effect of reaction temperature on the morphology and size of hydroxyapatite nanoparticles in an emulsion system

Effect of reaction temperature on the morphology and size of hydroxyapatite nanoparticles in an emulsion system