Highly biocompatible, monodispersed and mesoporous La(OH)3:Eu@mSiO2 core-shell nanospheres: Synthesis and luminescent properties

Chitosan modified with lanthanum ions as implantable hydrogel for local delivery of bisphosphonates

Osteoporosis is a disease that affects many people around the world. One group of drugs used to treat it are bisphosphonates. However, they have poor bioavailability and many side effects. Therefore, research around the world is focused on developing bisphosphonate delivery systems. In this paper, we would like to present the design of a hydrogel material with chitosan matrix modified with lanthanum, that could serve as an implantable hydrogel capable of sustained and slow release of Zoledronate. Various research techniques were used to characterize the materials, and the swelling ratio and water solubility were also tested. The conducted research proved that the prepared hydrogel is capable of the long-term release of the Zoledronate. Thanks to this, the prepared material can be successfully used as an implantable hydrogel or a coating on titanium implants for the local delivery of drugs.

Development of Core@Shell γ-Fe2O3@MnxOy@SiO2 Nanoparticles for Hyperthermia, Targeting, and Imaging Applications

Monodispersed core@shell γ-Fe₂O₃@Mn_xO_y nanoparticles have been prepared through thermolysis of iron and manganese oleate. Further, these prepared nanoparticles are coated with biocompatible substances such as silica and polyethylene glycol. These particles are highly biocompatible for different cell lines such as normal and cancer cell lines. The nanoparticles are used as hyperthermia agents, and successful hyperthermia treatment in cancer cells is carried out. As compared to γ-Fe₂O₃@SiO₂, γ-Fe₂O₃@Mn_xO_y@SiO₂ shows the enhanced killing of cancer cells through hyperthermia. In order to make them potential candidates for targeting to cancer cells, folic acid (FA) is tagged to the nanoparticles. Fluorescein isothiocyanate (FITC) is also tagged onto these nanoparticles for imaging. The developed γ-Fe₂O₃@Mn_xO_y@SiO₂ nanoparticle can act as a single entity for therapy through AC magnetic field, imaging through FITC and targeting through folic acid simultaneously. This is the first report on this material, which is highly biocompatible for hyperthermia, imaging, and targeting.

Facile synthesized NaGdF4 :Yb, Er peanut-shaped, highly biocompatible, colloidal upconversion nanospheres

A facile method was used for the synthesis of peanut-shaped very emissive NaGdF₄ :Yb, Er upconversion nanospheres (UCNSs) at lower temperatures with uniform size distribution. Crystallographic structure, phase purity, morphology, thermal robustness, biocompatibility, colloidal stability, surface chemistry, optical properties, and luminesce properties were explored by X-ray diffraction (XRD), Scanning electron microscope (SEM), transmission electron microscope (TEM), zeta potential, Thermogravimetric/thermal differential analysis (TGA/DTA), Fourier transform infrared (FTIR), UV/visible and photoluminescence spectroscopic tools. XRD pattern verified the construction of a single-phase, highly-crystalline NaGdF₄ phase with a hexagonal structure. Peanut-shaped morphology of the sample was obtained from SEM micrographs which were validated from high-resolution TEM images, have an equatorial diameter of 170-200 nm and a length of 220-230 nm, with irregular size, monodispersed, porous structure, and rough surface of the particles. The positive zeta potential value exhibited good biocompatibility along with high colloidal stability as observed from the absorption spectrum. The prepared UCNSs revealed high dispersibility, irregular size peanut-shaped morphology, rough surface, good colloidal stability, and excellent biocompatibility in aqueous media. A hexagonal phase NaGdF₄ doped with Yb, and Er UCNSs revealed the characteristics of highly dominant emissions located at 520-525, 538-550, and 659-668 nm are corresponding to the ² H_11/2 →⁴ I_15/2 , ⁴ S_3/2 →⁴ I_15/2 , and ⁴ F_9/2 →⁴ I_15/2 transition of Er³⁺ ions, respectively, as a result of energy transfer from sensitizer Yb³⁺ ion to emitter Er³⁺ ion.

Phase Transformation, Photocatalytic and Photoluminescent Properties of BiPO4 Catalysts Prepared by Solid-State Reaction: Degradation of Rhodamine B

Polycrystalline bismuth phosphate BiPO4 was synthesized by solid-state reaction at different temperatures varying from 500 to 900 °C. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and Raman spectroscopy. The low-temperature phase of BiPO4 has monoclinic structure with a space group P21/n, and was transformed into the monoclinic phase P21/m with a slight distortion of monoclinic lattice when it was heated above 500 °C. The effect of the transformation on the structure, morphology and photocatalytic properties was examined. The photocatalytic activity of each sample, in presence of Rhodamine B (RhB) in aqueous solution, was carried out and analyzed under UV light irradiation. Photoexperiments showed that the material prepared at 500 °C is the best catalyst with degradation efficiency of the order of 96% after 12 min of reaction time under UV light irradiation. This high photocatalytic efficiency could be due to their structural and morphological changes. The photocatalytic degradation mechanism of RhB in the presence of the best photocatalyst BiP-500 °C is proposed. The stability of the catalyst was also examined by carrying out four successive tests of the degradation in the presence of BiP-500 °C. Total organic carbon (TOC) was used to further estimate the rate of mineralization in the presence of BiP-500 °C (83% TOC removal). Photoluminescence experiments performed under UV-laser light irradiation revealed emissions in the green-orange range, with optimal intensities for the mix systems observed at 550 °C.

Physiochemical characterization of highly biocompatible, and colloidal LaF3:Yb/Er upconversion nanoparticles

Highly colloidal upconversion nanoparticles (UCNPs) were synthesized at low temperatures by the thermal decomposition process. The structure, morphology, crystallinity, surface chemistry, and optical properties were systematically optimized and studied through various spectroscopic techniques. X-ray diffraction (XRD) patterns have shown the formation of single-phase, highly purified, well-crystalline, hexagonal LaF₃ NPs, while the TEM micrographs show small, irregular sizes, spherically shaped, and aggregated polycrystalline UCNPs with an average crystalline size of about 8-15 nm. The Negative Zeta Potential value exhibits good biocompatibility of the UCNPs, which supports the idea that surface-anchored hydroxyl groups facilitate the stabilization of the NPs in aqueous media, as well as enhance biomolecules' tagging efficiency. The absorption spectrum, Zeta Potential, and hydrodynamic size that were measured in aqueous media illustrate excellent dispersibility, colloidal stability, biocompatibility, and cytotoxicity character of the UCNPs. Zeta potential and MTT assay studies illustrated high biocompatibility, it could be due to the surface-anchored hydroxyl groups. The nanoproduct demonstrates an excellent UC luminescence spectrum (i.e., prominent green emission ⁴S_3/2 → ⁴I/_15/2) upon irradiation by the 980-nm laser diode. TEM micrographs, further, revealed that this optically active material with aqueous sensitivities, porous crystal structure, and excellent UCNPs, could be a favorable candidate for potential photonics-based bio-related applications.

SiO2:Tb3+@Lu2O3:Eu3+ Core-Shell Phosphors: Interfacial Energy Transfer for Enhanced Multicolor Luminescence

Uniform and well-dispersed SiO₂:x%Tb³⁺@Lu₂O₃:y%Eu³⁺ core-shell spherical phosphors were synthesized via a solvothermal method followed by a subsequent calcination process. The structure, phase composition, and morphology of the samples were studied by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that the Lu₂O₃:Eu³⁺ layer was evenly coated on the surface of SiO₂:Tb³⁺ spheres and the shell thickness was about 45-65 nm. The PL spectra and fluorescence lifetimes of the samples were further studied. It was proved that the multicolor luminescence of the samples could be realized by changing the doping concentration ratio of Eu³⁺ or by changing the excitation wavelengths. Compared with SiO₂@Lu₂O₃:3%Tb³⁺,6%Eu³⁺, SiO₂:3%Tb³⁺@Lu₂O₃:6%Eu³⁺ showed stronger luminescence intensity, longer fluorescence lifetime, and higher energy transfer efficiency, which was attributed to the effective interfacial energy transfer, and the interfacial energy transfer mechanism from Tb³⁺ to Eu³⁺ was a dipole-dipole interaction mechanism. The XPS results indicated that the sample contained a high content of Si-O-Lu bonds, which proved that there was a strong interaction between the SiO₂ core and the Lu₂O₃ shell, making the interfacial energy transfer possible. These results provided a new idea for luminescence enhancement and multicolor luminescence.

Optically active neodymium hydroxide surface-functionalized mesoporous silica micro-cocoons for biomedical applications

Neodymium hydroxide (Nd(OH)₃)-surface modified mesoporous silica micro-cocoon microstructures were prepared using a facile single-step sol-gel chemical process. XRD revealed the semi-crystalline nature of the as-prepared materials. TEM and SEM micrographs exhibited highly monodisperse, non-aggregated, typical ordered mesoporous, and irregular sized cocoon-shaped micro-structures with a narrow size distribution. Optical properties, that were examined in the aqueous media, revealed a high colloidal stability and the formation of a semi-transparent colloidal solution. The colloidal solution of Nd(OH)₃-surface functionalized micro-structures revealed well characteristics absorption bands of Nd³⁺ ions in the visible region. thus validating the successful coating of SiO₂@Nd(OH)₃ layer over the surface silica forming core-shell structures. Zeta potential, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium) bromide, and neutral red uptake assays were applied in a dose-dependent manner to investigate the biocompatibility and toxic potential of the designed cocoon-shaped microstructures. Both the assays and the high zeta potential value demonstrated good cell viability even at high concentrations and hydrophilic conditions, indicating excellent biocompatibility and non-toxicity. These highly hydrophilic, optically active, mesoporous, biocompatible, and non-toxic cocoon-shaped microstructures could be potentially suitable candidates for optical bio-probes and drug delivery applications.

Toxicity response of highly colloidal, bioactive, monodisperse SiO2@ Pr(OH)3 hollow microspheres

In a facile synthesis, highly colloidal, bioactive Pr(OH)₃-encapsulated silica microspheres (PSMSs) with an average diameter of 500-700 nm were successfully prepared via a sol-gel process followed by heat treatment. The phase formation, morphology, surface and optical properties of the as-synthesized PSMSs were characterized by various techniques including X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscope (TEM), N₂-adsorption-desorption, energy dispersive X-ray (EDX) analysis, Fourier transform infrared (FTIR) and UV/vis spectroscopy. The PSMSs were semi-amorphous or ultra-small in size, highly dispersible in water, mesoporous, irregular in size and spherical in shape. The SEM images show a well-ordered broad nanoporous structure which is preserved after coating with Pr(OH)₃ molecules, demonstrating interaction between the optically active Pr³⁺ ion and silanol (Si-OH) groups via hydrogen bonding. Optical spectra show well-resolved weak intensity 4f-4f absorption transitions in the visible region of the Pr³⁺ ion, indicating successful grafting of the Pr(OH)₃ layer. Toxicity was measured by MTT and NRU assays to determine potential toxicity. Cell viability was suppressed with increasing dosage of PSMSs, but showed greater than 55% cell viability at a concentration of 200 μg/mL, resulting in low toxicity. Due to its high aqueous dispersibility, optical activity, excellent biocompatibility and low toxic nature, it could be a favorable material for biomedical and drug delivery applications.

Aqueous dispersible green luminescent yttrium oxide:terbium microspheres with nanosilica shell coating

Tb-doped Y₂O₃ microspheres (MSs) were prepared via a homogeneous thermal degradation process at a low temperature and then coated with a nanosilica shell (Y₂O₃:Tb@SiO₂) using a sol-gel process. The core MSs were highly crystalline and spherical with a porous surface, single cubic phase, and particle size of 100-250 nm. Transmission electron microscopy (TEM) images clearly showed the spherical shape of the as-prepared core MSs, which were fully covered with a thick and mesoporous nanosilica shell. Fourier transform infrared (FTIR) spectra displayed the well-resolved infrared absorption peaks of silica (SiO, SiOSi, etc.), confirming the presence of the silica surface coating. The core MSs retained their spherical shape even after heat treatment and subsequent silica surface coating. It was observed that the core/shell MSs are easily dispersible in aqueous media and form a semi-transparent colloidal solution. Ultraviolet/visible and zeta potential studies were tested to prove the changes in the surface chemistry of the as-designed core/shell MSs and compare with their core counterpart. The growth of the amorphous silica shell not only increased the particle size but also enhanced remarkably the solubility and colloidal stability of the MSs in aqueous media. The strongest emission lines originating from the characteristic intra-shell 4f-4f electronic transitions of Tb ions were quenched after silica layer deposition, but the MSs still showed strong green (⁵D₄ → ⁷F₅ at 530-560 nm as most dominant) emission efficiency, which indicates great potential in fluorescent bio-probes. The emission intensity is discussed in relation to the quenching mechanism induced by surface silanol (Si-OH) groups, particle size, and surface charge.