Systematic investigation and in vitro biocompatibility studies on mesoporous europium doped hydroxyapatite

Complex Evaluation of Nanocomposite-Based Hydroxyapatite for Biomedical Applications

A magnesium-doped hydroxyapatite in chitosan matrix (MgHApC) sample was developed as a potential platform for numerous applications in the pharmaceutical, medical, and food industries. Magnesium-doped hydroxyapatite suspensions in the chitosan matrix were obtained by the coprecipitation technique. The surface shape and morphological features were determined by scanning electron microscopy (SEM). The hydrodynamic diameter of the suspended particles was determined by Dynamic light scattering (DLS) measurements. The stability of MgHApC suspensions was evaluated by ultrasonic measurements. The hydrodynamic diameter of the MgHApC particles in suspension was 29.5 nm. The diameter of MgHApC particles calculated from SEM was 12.5 ± 2 nm. Following the SEM observations, it was seen that the MgHApC particles have a spherical shape. The Fourier-transform infrared spectroscopy (FTIR) studies conducted on MgHApC proved the presence of chitosan and hydroxyapatite in the studied specimens. In vitro antimicrobial assays were performed on Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231 microbial strains. The antimicrobial experiments showed that MgHApC exhibited very good antimicrobial properties against all the tested microorganisms. More than that, the results of the in vitro studies revealed that the antimicrobial properties of the samples depend on the incubation time. The evaluation of the sample's cytotoxicity was performed using the human colon cancer (HCT-8) cell line. Our results suggested the great potential of MgHApC to be used in future applications in the field of biomedical applications (e.g., dentistry, orthopedics, etc.).

Lanthanides-Substituted Hydroxyapatite for Biomedical Applications

Lately, there has been an increasing demand for materials that could improve tissue regenerative therapies and provide antimicrobial effects. Similarly, there is a growing need to develop or modify biomaterials for the diagnosis and treatment of different pathologies. In this scenario, hydroxyapatite (HAp) appears as a bioceramic with extended functionalities. Nevertheless, there are certain disadvantages related to the mechanical properties and lack of antimicrobial capacity. To circumvent them, the doping of HAp with a variety of cationic ions is emerging as a good alterative due to the different biological roles of each ion. Among many elements, lanthanides are understudied despite their great potential in the biomedical field. For this reason, the present review focuses on the biological benefits of lanthanides and how their incorporation into HAp can alter its morphology and physical properties. A comprehensive section of the applications of lanthanides-substituted HAp nanoparticles (HAp NPs) is presented to unveil the potential biomedical uses of these systems. Finally, the need to study the tolerable and non-toxic percentages of substitution with these elements is highlighted.

Cu-Doped 1D Hydroxyapatite as a Highly Active Catalyst for the Removal of 4-Nitrophenol and Dyes from Water

Metallic copper nanoparticle (Cu NP)-doped 1D hydroxyapatite was synthesized using a simple chemical reduction method. To describe the structure and composition of the Cu/HAP nanocomposites, physicochemical techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, inductively coupled plasma, N₂ adsorption-desorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy were used. The TEM scan of the Cu/HAP nanocomposite revealed a rod-like shape with 308 nm length and 117 nm width on average. The catalytic activity of Cu/HAP nanocomposites for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH₄ has been thoroughly investigated. The 0.7% Cu/HAP nanocomposite was shown to have superior catalytic activity than the other nanocomposites, converting 4-NP to 4-AP in ∼1 min with good recyclability. Moreover, this nanocomposite showed excellent catalytic performance in the organic dye reduction such as Congo red and acriflavine hydrochloride dyes. The high dispersion of Cu NPs on HAP support, the high specific surface area, and the small Cu particles contributed to its remarkable catalytic performance.

Physicochemical Characterization of Europium-Doped Hydroxyapatite Thin Films with Antifungal Activity

Owing to its unique biological and physicochemical properties, hydroxyapatite (HAp) represents one of the most extensively studied biomaterials for biomedical applications. It is well known that Candida is currently one of the fungi frequently involved in the onset and development of post-implant infections and, owing to the appearance of antifungal resistance, it is quite difficult to treat despite all the tremendous efforts made in this regard by the scientific world. Therefore, in this context, we report for the first time in this paper, the development and characterization of europium-doped thin films (5EuHAp, xEu = 0.05) on a Si substrate by a spin-coating method. The results of ultrasound (US), zeta (ζ) potential, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) studies are presented. The XRD studies conducted on 5EuHAp suspension revealed the nanometric dimensions of the particles and sample purity. In addition, a moderate stability of the 5EuHAp suspension was observed. XPS measurements revealed the presence of Eu 3d in the 5EuHAp thin films. In the SEM micrographs, the surface uniformity and the absence of the surface defects could be observed. Moreover, the results of the FTIR studies showed the presence of the vibrational bands specific to the HAp structure in the studied sample. The antifungal activity of the HAp and 5EuHAp suspensions and coatings was evaluated using the Candida albicans ATCC 10231 (C. albicans) fungal strain. The qualitative assays of the antifungal properties of HAp and 5EuHAp coatings were also visualized by SEM and CLSM. The antifungal studies revealed that both 5EuHAp suspensions and coatings exhibited noticeable antifungal activity against C. albicans cells.

Real-Time Tracking of Highly Luminescent Mesoporous Silica Particles Modified with Europium β-Diketone Chelates in Living Cells

Highly luminescent europium complexes modified mesoporous silica particles (MSP) were synthesized as an imaging probes for both in-vitro diagnostic and in-vivo cellular tracking agents. Europium β-diketone chelates (4,4,4-trifluoro-l-(2-thienyl)-l,3-butanedione) trioctylphosphine europium (III) (Eu(TTA)₃(P(Oct)₃)₃) were incorporated inside the nanocavities that existed in hierarchical MSP (Eu@MSP). The MSP and Eu@MSP on mouse bone marrow-derived macrophages (BMDMs) did not show any toxic effect. The MSP and Eu@MSP in the BMDMs were found at cytoplasm without any degradation and immunogenicity. However, both pro- and anti-inflammatory cytokines of macrophages were significantly increased when lipopolysaccharide and a high concentration (100 μg/mL) of MSP and Eu@MSP were treated simultaneously.

Cationic Substitutions in Hydroxyapatite: Current Status of the Derived Biofunctional Effects and Their In Vitro Interrogation Methods

High-performance bioceramics are required for preventing failure and prolonging the life-time of bone grafting scaffolds and osseous implants. The proper identification and development of materials with extended functionalities addressing socio-economic needs and health problems constitute important and critical steps at the heart of clinical research. Recent findings in the realm of ion-substituted hydroxyapatite (HA) could pave the road towards significant developments in biomedicine, with an emphasis on a new generation of orthopaedic and dentistry applications, since such bioceramics are able to mimic the structural, compositional and mechanical properties of the bone mineral phase. In fact, the fascinating ability of the HA crystalline lattice to allow for the substitution of calcium ions with a plethora of cationic species has been widely explored in the recent period, with consequent modifications of its physical and chemical features, as well as its functional mechanical and in vitro and in vivo biological performance. A comprehensive inventory of the progresses achieved so far is both opportune and of paramount importance, in order to not only gather and summarize information, but to also allow fellow researchers to compare with ease and filter the best solutions for the cation substitution of HA-based materials and enable the development of multi-functional biomedical designs. The review surveys preparation and synthesis methods, pinpoints all the explored cation dopants, and discloses the full application range of substituted HA. Special attention is dedicated to the antimicrobial efficiency spectrum and cytotoxic trade-off concentration values for various cell lines, highlighting new prophylactic routes for the prevention of implant failure. Importantly, the current in vitro biological tests (widely employed to unveil the biological performance of HA-based materials), and their ability to mimic the in vivo biological interactions, are also critically assessed. Future perspectives are discussed, and a series of recommendations are underlined.

Influence of Thermal Treatment on the Antimicrobial Activity of Silver-Doped Biological Apatite

In this paper, we report the structural and morphological properties of silver-doped hydroxyapatite (AgHAp) with a silver concentration x Ag = 0.5 before and after being thermal treated at 600 and 1000 °C. The results obtained by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy suggest that the structure of the samples changes gradually, from hydroxyapatite (AgHAp_40) to a predominant β-TCP structure (AgHAp_1000), achieved when the thermal treatment temperature is 1000 °C. In the AgHAp_600 sample, the presence of two phases, HAp and β-TCP, was highlighted. Also, scanning electron microscopy studies suggest that the shape and dimension of the nanoparticles begin to change when the temperature increases. The antimicrobial activity of the obtained compounds was evaluated against Klebsiella pneumoniae, Staphylococcus aureus, and Candida albicans strains.