Shanshan Huang

Self-activated luminescent and mesoporous strontium hydroxyapatite nanorods for drug delivery

Multifunctional strontium hydroxyapatite (SrHAp) nanorods with luminescent and mesoporous properties have been successfully synthesized by a hydrothermal method. SEM and TEM images indicate that the mesoporous SrHAp samples consist of monodiperse nanorods with lengths of 120-150 nm, diameters of around 20 nm, and the mesopore size of 3-5 nm. The as-obtained SrHAp nanorods show an intense bright blue emission (centered at 432 nm, lifetime 11.6 ns, quantum efficiency: 22%), which might arise from CO(2)(*-) radical impurities in the crystal lattice under long-wavelength UV-light irradiation. Furthermore, the amount of trisodium citrate has an obvious impact on the particle size and the luminescence properties of the products, respectively. The drug storage/release test indicates that the luminescent SrHAp nanorods show a drug loading and controlled release properties for ibuprofen (IBU). Additionally, the emission intensity of SrHAp in the drug carrier system increases with the cumulative released amount of IBU, making the drug release might be easily tracked and monitored by the change of the luminescence intensity. This luminescent material may be potentially applied in the drug delivery and disease therapy fields.

Controllable and white upconversion luminescence in BaYF5:Ln3+ (Ln = Yb, Er, Tm) nanocrystals

BaYF5:Yb3+, Er3+, Tm3+ nanocrystals have been successfully synthesized via a hydrothermal process. SEM and TEM images indicate that the size of the nanocrystals is about 20 nm. Under the excitation of a 980 nm single-wavelength diode laser, BaYF5:Er3+ nanocrystals give strong green upconversion (UC) emission centered at 523 and 541 nm, which is assigned to 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of Er3+, respectively. When Yb3+ is codoped in BaYF5:Er3+, red emission around 652 nm can be observed in the emission spectrum. This emission can be assigned to the 4F9/2 → 4I15/2 transition of Er3+. The intensity ratio of the green luminescence to the red luminescence decreases with increasing Yb3+ concentration in BaYF5:Yb3+, Er3+ nanocrystals. The blue UC emissions of BaYF5:Yb3+, Tm3+ nanocrystals appeared near 464 and 480 nm and are assigned to the 1D2 → 3F4 and 1G4 → 3H6 transitions of Tm3+, respectively. Based on the generation of red, green, and blue emissions, the BaYF5:Yb3+, Er3+, Tm3+ nanocrystals can produce different colors, including white, by controlling the doping concentration of Yb3+ in the BaYF5 nanocrystals. The BaYF5:40%Yb3+, 0.5%Er3+, 0.5%Tm3+nanocrystals show proper intensities of blue, green, and red emissions, which result in the production of white light (CIE: x = 0.346, y = 0.336).

Monodisperse core–shell structured up-conversion Yb(OH)CO3@YbPO4:Er3+ hollow spheres as drug carriers

In this work, we report a facile solution-phase synthesis of monodisperse core-shell structured Yb(OH)CO₃@YbPO₄ hollow spheres (size around 380 nm) by utilizing the colloidal sphere of Yb(OH)CO₃ as the sacrificial template via the Kirkendall effect. The Er³+ doped Yb(OH)CO₃@YbPO₄ core-shell hollow spheres can be prepared similarly, which exhibit strong green emission under 980 nm NIR laser excitation even after loading with drug molecules. Most importantly, the sample can be used as an effective drug delivery carrier. The biocompatibility test on L929 fibroblast cells using MTT assay reveals low cytotoxicity of the system. A typical anticancer drug, doxorubicin hydrochloride (DOX), is used for drug loading, and the release properties, cytotoxicity, uptake behavior and therapeutic effects were examined. It is found that DOX is shuttled into cell by core-shell hollow spheres carrier and released inside cells after endocytosis, and the DOX-loaded spheres exhibited greater cytotoxicity than free DOX. These results indicate that the core-shell Er³+ doped Yb(OH)CO₃@YbPO₄ hollow spheres have potential for drug loading and delivery into cancer cells to induce cell death.

Facile and Controllable Synthesis of Monodisperse CaF2 and CaF2:Ce3+/Tb3+ Hollow Spheres as Efficient Luminescent Materials and Smart Drug Carriers

Highly uniform and well-dispersed CaF(2) hollow spheres with tunable particle size (300-930 nm) have been synthesized by a facile hydrothermal process. Their shells are composed of numerous nanocrystals (about 40 nm in diameter). The morphology and size of the CaF(2) products are strongly dependent on experimental parameters such as reaction time, pH value, and organic additives. The size of the CaF(2) hollow spheres can be controlled from 300 to 930 nm by adjusting the pH value. Nitrogen adsorption-desorption measurements suggest that mesopores (av 24.6 nm) exist in these hollow spheres. In addition, Ce(3+)/Tb(3+)-codoped CaF(2) hollow spheres can be prepared similarly, and show efficient energy transfer from Ce(3+) to Tb(3+) and strong green photoluminescence of Tb(3+) (541 nm, (5)D(4)-->(7)F(5) transition of Tb(3+), the highest quantum efficiency reaches 77%). The monodisperse CaF(2):Ce(3+)/Tb(3+) hollow spheres also have desirable properties as drug carriers. Ibuprofen-loaded CaF(2):Ce(3+)/Tb(3+) samples still show green luminescence of Tb(3+) under UV irradiation, and the emission intensity of Tb(3+) in the drug-carrier system varies with the released amount of ibuprofen, so that drug release can be easily tracked and monitored by means of the change in luminescence intensity. The formation mechanism and luminescent and drug-release properties were studied in detail.

Tunable luminescence in Ce3+, Mn2+-codoped calcium fluorapatite through combining emissions and modulation of excitation: a novel strategy to white light emission

The Ce3+, Mn2+-codoped calcium fluorapatite [Ca5(PO4)3F, FAP] nanorods were prepared by a simple hydrothermal method. SEM and TEM images indicate that the FAP : Ce3+, Mn2+ sample consists of nanorods with lengths around 30–70 nm and diameters around 20 nm, respectively. The as-obtained FAP nanorods show an intense bright blue emission (centered at 432 nm, lifetime 7.5 ns) arising from CO2˙− radical impurities in the crystal lattice under UV light irradiation. In addition, codoped with Ce3+ and Mn2+, the as-synthesized FAP : Ce3+, Mn2+ sample shows the tunable luminescence from blue to white to yellow by the variation of excitation UV light. The emission spectra of the as-synthesized FAP : Ce3+, Mn2+ sample show three broad bands, which are associated with the CO2˙− radical impurities (blue emission), Ce3+ ions (ultraviolet emission), and Mn2+ ions (yellow emission), respectively. The coexistence of three broad emissions results in the bright white light directly under suitable excitation wavelength. The combination emissions of impurities and metal activator ions may provide a novel strategy to obtain white light and tunable luminescence.

Magnetic Fe3O4@mesoporous silica composites for drug delivery and bioadsorption

Magnetic Fe(3)O(4)@mesoporous silica (MS) composites were synthesized by generating Fe(3)O(4) nanoparticles in the mesoporous silica matrix using the sol-gel method in nitrogen atmosphere. The mesoporous silica hosts include SBA-15 particles owning highly ordered p6mm mesostructure, siliceous mesostructured cellular foams (MCFs), and fiber-like mesoporous silica (FMS) with unique pore structures. The X-ray diffraction (XRD), transmission electron microscopy (TEM), and N(2) adsorption/desorption results show that Fe(3)O(4) functionalized MCFs and FMS possess suitable mesoporous structure for the adsorption of both small-molecular drug and large biomolecules. The biocompatibility tests on L929 fibroblast cells using MTT assay reveal low cytotoxicity of these systems. These Fe(3)O(4)@mesoporous silica composites show sustained release properties for aspirin in vitro. The release of the aspirin molecules from the pores of the Fe(3)O(4)@mesoporous silica composites is basically a diffusive process. Fe(3)O(4)@MCFs and Fe(3)O(4)@FMS owning larger pore size are good candidates for the adsorption of bovine serum albumin (BSA). These magnetic composites can be potential vectors for drug delivery and bioadsorption.

Gelatin-encapsulated iron oxide nanoparticles for platinum (IV) prodrug delivery, enzyme-stimulated release and MRI

A facile method for transferring hydrophobic iron oxide nanoparticles (IONPs) from chloroform to aqueous solution via encapsulation of FITC-modified gelatin based on the hydrophobic-hydrophobic interaction is described in this report. Due to the existence of large amount of active groups such as amine groups in gelatin, the fluorescent labeling molecules of fluorescein isothiocyanate (FITC) and platinum (IV) prodrug functionalized with carboxylic groups can be conveniently conjugated on the IONPs. The nanoparticles carrying Pt(IV) prodrug exhibit good anticancer activities when the Pt(IV) complexes are reduced to Pt(II) in the intracellular environment, while the pure Pt(IV) prodrug only presents lower cytotoxicity on cancer cells. Meanwhile, fluorescence of FITC on the surface of nanoparticles was completely quenched due to the possible Förster Resonance Energy Transfer (FRET) mechanism and showed a fluorescence recovery after gelatin release and detachment from IONPs. Therefore FITC as a fluorescence probe can be used for identification, tracking and monitoring the drug release. In addition, adding pancreatic enzyme can effectively promote the gelatin release from IONPs owing to the degradation of gelatin. Noticeable darkening in magnetic resonance image (MRI) was observed at the tumor site after in situ injection of nanoparticles, indicating the IONPs-enhanced T2-weighted imaging. Our results suggest that the gelatin encapsulated Fe3O4 nanoparticles have potential applications in multi-functional drug delivery system for disease therapy, MR imaging and fluorescence sensor.

A luminescent and mesoporous core-shell structured Gd2O3 : Eu3+@nSiO2@mSiO2 nanocomposite as a drug carrier

In this paper, Gd(2)O(3) : Eu(3+) nanospheres have been encapsulated with nonporous silica and further layer of ordered mesoporous silica through a simple sol-gel process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N(2) adsorption/desorption, photoluminescence (PL) spectra, and kinetic decay were used to characterize the sample. The results indicate that the nanocomposite with general 50 nm shell thickness and 270 nm core size shows typical ordered mesoporous characteristics (2.4 nm) and has spherical morphology with a smooth surface and narrow size distribution. Additionally, the obtained inorganic nanocomposite shows the characteristic emission of Eu(3+) ((5)D(0)→(7)F(1-4)) even after the loading of drug molecules. The biocompatibility test on L929 fibroblast cells using MTT assay reveals low cytotoxicity of the system. Most importantly, the nanocomposite can be used as an effective drug delivery carrier. A typical anticancer drug, doxorubicin hydrochloride (DOX), was used for drug loading, and the DOX release, cytotoxicity, uptake behavior and therapeutic effects were examined. It was found that DOX is shuttled into the cell by the nanocomposite and released inside cells after endocytosis and that the DOX-loaded nanocomposite exhibited greater cytotoxicity than free DOX. These results indicate that core-shell structured Gd(2)O(3) : Eu(3+)@nSiO(2)@mSiO(2) nanocomposite has potential for drug loading and delivery into cancer cells to induce cell death.

Electrospinning preparation and drug delivery properties of Eu3+/Tb3+ doped mesoporous bioactive glass nanofibers

Luminescent Eu(3+)/Tb(3+) doped mesoporous bioactive glass nanofibers (MBGNFs) with average diameter of 100-120 nm were fabricated by electrospinning method. Pluronic P123 and N-cetyltrimethylammonium bromide (CTAB) were used as co-surfactants to generate porous structure of the nanofibers. N(2) adsorption-desorption measurement reveals that the MBGNF:Eu(3+) have a surface area of 188 m(2) g(-1), a pore volume of 0.246 cm(3) g(-1) and average pore size of 4.17 nm, and the MBGNF:Tb(3+) have a surface area of 171 m(2) g(-1), a pore volume of 0.186 cm(3) g(-1) and average pore size of 3.65 nm. Photoluminescence measurements reveal that the MBGNF:Eu(3+) show strong red emission dominated by the (5)D(0)→(7)F(2) transition of Eu(3+) at 614 nm with a lifetime of 1.356 ms, and MBGNF:Tb(3+) show strong green emission dominated by the (5)D(4)→(7)F(5) transition of Tb(3+) at 544 nm with a lifetime of 1.982 ms. The biocompatibility tests on L929 fibroblast cells using MTT assay reveal low cytotoxicity of MBGNF. These luminescent nanofibers show sustained release properties for ibuprofen (IBU) in vitro. The emission intensities of Eu(3+) in the drug delivery system vary with the released amount of IBU, thus making the drug release be easily tracked and monitored by the change of the luminescence intensity.

MCM-41 functionalized with YVO4:Eu3+: a novel drug delivery system

Luminescence functionalization of ordered mesoporous MCM-41 silica was realized by depositing a YVO4:Eu3+ phosphor layer on its surface via the Pechini sol-gel process. This material, which combines the mesoporous structure of MCM-41 and the strong red luminescence property of YVO4: Eu3+, has been studied as a host carrier for drug delivery/release systems. The structure, morphology, texture and optical properties of the materials were well characterized by x-ray diffraction ( XRD), Fourier infrared spectroscopy ( FT-IR), transmission electron microscopy ( TEM), N-2 adsorption and photoluminescence ( PL) spectra. The results indicated that the specific surface area and pore volume of MCM-41, which were directly correlated to the drug-loading amount and ibuprofen ( IBU) release rate, decreased in sequence after deposition of YVO4:Eu3+ and loading of IBU as expected. The IBU-loaded YVO4:Eu3+@ MCM-41 system still showed red luminescence under UV irradiation ( 365 nm) and a controlled release property for IBU. In addition, the emission intensity of Eu3+ increases with an increase in the cumulative released amount of IBU, making the extent of drug release easily identified, tracked and monitored by the change of luminescence, which demonstrates its potential application in drug delivery/release systems.