Iranian Journal of Pharmaceutical Sciences
Volume:4 Issue: 2, Spring 2008

Biodegradable nanoparticulate carriers, have important potential applications for administration of therapeutic molecules. Chitosan based nanoparticles have attracted a lot of attention upon their biological properties such as biodegradability, biocom-patibility and bioadhesivity. The aim of the present investigation was to describe the synthesis and characterization of novel biodegradable nanoparticles based on chitosan for encapsulation of dexamethasone sodium phosphate. To achieve this objective, ionic gelation method were used. Drug containing nanoparticles were prepared with different amounts of drug. The mean size and size distribution of nanoparticles were measured by dynamic laser light scattering. The mean particle size, varied in the range of 250-350 nm. Values of loading capacity and loading efficiency varied between 33.7%-72.2% and 44.5%-76.0% for prepared nanoparticles.

In this work, Mn ferrite nanopowders were prepared by co-precipitation method and were characterized. Phase identification of the nanopowders was performed by X-ray diffraction method and the mean particle size of the nanopowders was calculated by Scherrer's formula, using necessary corrections. Magnetic parameters of the prepared nanopowders were measured by a vibrating sample magnetometer. A sensitive thermometer was used to measure the increase in temperature due to application of an alternating magnetic field on suspended magnetic nanopowders in water. Transmission electron microscope investigations showed that the particle size distribution was homogeneous and their size was in a good agreement with those obtained by Scherrer's formula. The results show that a single phase Mn ferrite can be obtained by co-precipitation method at 70 °C with a mean particle size of 5 nm and a 5 °C temperature increase is achievable in an AC magnetic field.

Nafion is a perfluorinated anionic polyelectrolyte. The increasing popularity of nafion for the fabrication of redox polymer modified electrodes in recent years arises from easy fabrication, good electrical conductivity and high partition coefficients of many redox compounds in nafion. To investigate the production of nano-compositions by mixing electron transfer material and nafion polymer for the modification of electrodes, a functional membrane composed of nano-particles of methylene blue, and nafion was constructed. The materials were characterized by the methods of scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet (UV)-visible and FT-IR. The average diameter of new nano-particles was estimated to be about 60 nm. A novel nafion-riboflavin membrane was also constructed and characterized by the methods of SEM, TEM and UV-visible spectroscopy. The estimated average diameter of new nanoparticles was about 60 nm. Our data has proven that nafion can be very interesting and helpful material in constructing nanoparticles of different electro-active materials and it can immobilize this material with a very good stability.

In this study, hydroxyapatite (HA) nanocrystals have been synthesized via chemical precipitation technique. Diammonium hydrogen phosphate and calcium nitrate 4-hydrate were used as starting materials and sodium hydroxide solution was used as the agent for pH adjustment. The powder sample was evaluated by techniques such as scanning electron microscope, transmission electron microscope, Fourier transform infra-red spectroscopy, differential thermal analysis, thermal gravimetric analysis, X-ray diffraction, atomic absorption spectroscopy and EDTA titration analyses. According to the above-experimental results, it was found that hydroxyapatite nanocrystals can successfully be produced through wet precipitation method. The bulk Ca/P molar ratio of synthesized hydroxyapatite was determined as 1.71 that was higher than stoichiometric ratio (1.667) which is expected for a pure HA phase. Finally, transmission electron microscopic technique demonstrated that the crystallites of prepared powder were nanosized with a needle-like morphology.

This article describes the preparation and analysis of nano hydroxyapatite (HA) films on stainless steel 316L through sol-gel technique. The process started with preparation of a nitrate and phosphate sol. After aging the sol for 24 h at room temperature a SS316 substrate was dip-coated and heat-treated at 350 to 450 °C for different times in air. The coating phase and structure on substrate were investigated by X-ray diffraction (XRD), fourier transform infrared (FT-IR), differential thermal analysis (DTA) and scanning electron microscopy (SEM). Degree of crystallinity and time temperature transformation (TTT) diagram of HA films obtained with using Avrami equation. Results indicated that HA phase began to crystallize after a heat treatment at 250 °C and the crystallinity increased at a temperature of 450 °C. The HA film showed a nano structure with suitable crystallinity after heat treatment.

The bone mineral consists of tiny hydroxyapatite (HA) crystals in the nanoregime. Nanostructured HA is also expected to have better bioactivity than coarser crystals. This paper reports on the in vitro evaluation of bone like HA nanopowders. The prepared HA nanopowder was characterized for its phase purity, chemical homogeneity and bioactivity. Fourier transform infrared (FT-IR) spectroscopy was used to identify the functional groups. X-ray diffraction analysis was carried out to study the phase composition. The in vitro test was performed in a stimulated body fluid medium. The changes in the pH of SBF medium were measured at pre-determined time intervals using a pH meter. The dissolution of calcium ions in the SBF medium was determined by an atomic absorption spectrometer. FT-IR spectroscopy result combined with the X-ray diffraction exhibited single phase of HA with carbonate peaks in the FT-IR spectrum. Results indicated that increasing the sintering temperature increases the crystallinity and the crystallite size of HA nanopowders. HA nanopowders ionic dissolution rate was found to be quite higher than conventional HA and closer to biological apatite owing to its nanostructure dimensions.

The aim of this study was to investigate the effect of alkaline and heat treatment and acid etching of titanium substrates on the formation of calcium phosphate layer and bioactivity in simulated body fluid (SBF) solution. In this research, at first the titanium surfaces were treated with 5N NaOH, 15% HNO3-10%HF-75% H2O and 5N NaOH followed by heating at 600 ºC for 1h. The samples were immersed in the SBF for 28 days to investigate the influence of surface treatments of titanium on in vitro bioactivity. The modified substrates were characterized using scanning electron microscopy, X-ray diffraction and profilometry of samples were investigated by light interferometry. The in vitro assessment was carried out through the immersion of samples in SBF. According to the results obtained in this work the deposit of calcium phosphate in alkali and alkali/heat treated samples were more stable than acid etched samples. Porous network structure containing the sodium titanate and the titanium oxide was characterized on the surface after the titanium was subjected to NaOH aqueous solution. Results have illustrated the fact that chemical surface treatment improves in vitro behavior of titanium.

Hydroxyapatite (HA) nano-rods with uniform morphology and controllable size have been successfully synthesized in the presence of cationic and non-ionic surfactants by a hydrothermal method. (NH4) 2HPO4 and Ca(NO 3)2.4H2O were used as the phosphorus and calcium sources, respectively. The composition of synthesized powders was characterized using X-ray diffraction, and Fourier transform infrared spectrometer and morphology of the resulting powders were examined by scanning electron microscopy. Results revealed the as- prepared HA nano-rods have a typical diameter of about 60-80 nm and an average aspect ratio of about 10-12, which indicates that the mixture of cationic and non-ionic surfactants acts as a soft template to regulate the nucleation and crystal growth of HA. Also effect of hydrothermal temperature was studied on the system.

In a hydrothermal route devoted for synthesis of Ca10(PO4)6(OH)2 (HA) nanostructures, morphology can be controlled by experimental condition to form magical HA or nanostructured nanoparticles. In an intermediate condition, a novel nanostructure namely rose-like bundle of HA rod-likes was found, which is different from known HA nanostructures. The chemical synthesis of nanopowders under hydrothermal process provides an opportunity to control the HA and is dependent on sonochemical process. Since the procedure is very simple, this method is of general interest, and can be used for similar syntheses. The phase purity of the as-prepared products was determined by X-ray diffraction (XRD), fourier transform infrared (FT-IR), and scanning electron microscopy was applied to investigate the morphology. The microstructure of the HA products was further observed by transmission electron microscopy and energy-dispersive X-ray spectroscopy. The chemical composition of the as-synthesized powder was analyzed by inductively coupled plasma atomic emission spectroscopy. Interestingly, the approach proposed can be used for the preparation of different nanostructures of HA.

In this investigation, fluor-hydroxyapatite (FHA) film was deposited on a titanium substrate by sol-gel method. Triethyl phosphite, ammonium fluoride and calcium nitrate in ethanol solutions were used respectively as P, F and Ca precursors. Typical apatite structures were obtained for all coatings after dipping and subsequent heat treatment at 550, 700 and 800 ºC, the coating layers were investigated with X-ray diffraction, Fourier transform infra- red and Scanning electron microscopy spectroscopy. Based on the results obtained from X-ray diffraction, the coatings heated at 550 ºC were composed of hydroxyapatite (HA) and fluorapatite (FA). Rutile (TiO2) phase was also found in the coatings heated at higher temperature. In addition, the formation of fluor-hydroxyapatite was confirmed by FT-IR results. SEM studies showed the samples heat treated at 550 ºC and 700 ºC have almost the same morphology. It seems the coating of samples heat treated in 800 ºC was more homogenous and smooth without any considerable porosity.