Luis Fernando Zubieta-Otero

The aim of this work was the development and characterization of iron oxide nanoparticles with magnetite phases (IONPs)-hydroxyapatite (HAp) composites. In this article, the chemical coprecipitation method was used to synthesize three different nanomaterials: IONPs, HAp, and IONPs-HAp composite. Rietveld analysis of the X-ray diffraction (XRD) revealed the crystal lattice parameters and presence of HAp and IONPS after synthesis, which was carried out at a temperature of 120 °C inductively coupled plasma (ICP) was used to identify the trace elements present, Fourier transform infrared (FTIR) spectroscopy to verify the functional groups present in each material and efficiency of washes for the composite material, transmission electron microscopy (TEM) to observe the morphology and nanoparticle size for IONPs 11 nm and IONPs-HAp 15 nm. ζ potential measurements to investigate the surface charges for all samples had a positive value, the apatite samples showed a very stable behavior, and vibrating sample magnetometry (VSM) to evaluate the magnetic properties showed that IONPs and IONPs-HAp composite exhibit superparamagnetic behavior, while HAp nanoparticles show diamagnetic behavior. It was also shown that the saturation magnetization and magnetic moments of the IONPs do not change upon formation of the IONPs-HAp composite.

The current study focuses on the synthesizing of novel hybrid nanosystems of bio‐hydroxyapatite (BioHAp)/synthetic‐hydroxyapatite (HAp‐Syn). Bio‐HAp was defatted, deproteinized, and then sonicated to obtain nanoparticles (nBioHAp). Hybrid nanosystems (HNS) were synthesized by wet chemical precipitation using nBioHAp as nucleation sites and applying four different precipitation times of 45, 90, 135, and 180 min. X‐ray diffraction (XRD) showed that the patterns of the nBioHAp and HAp‐Syn samples have broadened diffraction peaks due to simultaneous elastic and inelastic scattering. Their crystallite size is about 25 nm, while the hybrid nanosystems have a size between 35 and 40 nm. Fourier‐transform infrared spectroscopy (FT‐IR) revealed the main groups associated with hydroxyapatite (PO₃²⁻, OH⁻, and CO₃²⁻), and the nanometer character of the crystals was demonstrated by studying the full width at half maximum (FWHM) of the spectra. Scanning electron microscopy (SEM) revealed the differences between the morphologies of nBioHAp and HAp‐Syn. The shape of HNS resembled that of biogenic HAp, which was confirmed by transmission electron microscopy (TEM). Inductively coupled plasma spectroscopy (ICP‐OES) and energy dispersive X‐ray spectroscopy (EDS) were used to confirm the elemental composition of Mg, Na, K, and Zn as minority ions.

The optical properties of hydroxyapatites (HAps) and bio HAps have been studied using Raman and infrared (IR) spectroscopies to describe their crystalline quality. However, the size of the HAp crystals and their crystalline order effects have not been considered yet. This paper focuses on the study of the effect of the change in the crystallites size have on the width of the IR and Raman spectra for defatted and deproteinized bones as well as incinerated biogenic HAp obtained from bovine, porcine, and human bones. Bone samples were analyzed through Raman and IR spectroscopies, X‐ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma (ICP), and scanning electron microscopy (SEM). The Raman and IR spectra for raw samples showed broad bands but, after calcination at 720 °C, became narrow and well defined. TEM images showed that all raw crystallites are ordered nanoplates contrary to the so far well‐established concept that biogenic HAps have low crystalline quality. XRD data confirmed that raw samples display broad peaks that correlated with the HRTEM images of ordered nanocrystals. This fact confirmed that the broad Raman and IR bands of raw clean bones come from nanocrystal plates. SEM analysis confirmed the increase in the crystal size after calcination from nanomicron to submicron dimensions due to a coalescence phenomenon. These results imply that the interpretation of Raman and IR spectra in the case of HAp nanoparticles has been erroneous. These results contribute to the design of biomaterials for tissue engineering based on biogenic HAp for bone regeneration.