Biolabeling Applications Research Articles

ChemInform Abstract: Fluorescent Monomers as Building Blocks for Dye Labeled Polymers: Synthesis and Application in Energy Conversion, Biolabeling and Sensors

AbstractReview: 271 refs.

Enhanced photoluminescence and characterization of multicolor carbon dots using plant soot as a carbon source

Carbon dots (C-dots) are a class of novel fluorescent nanomaterials, which have drawn great attention for their potential applications in bio-nanotechnology. Multicolor C-dots have been synthesized by chemical nitric acid oxidation using the reproducible plant soot as raw material. TEM analysis reveals that the prepared C-dots have an average size of 3.1nm. The C-dots are well dispersed in aqueous solution and are strongly fluorescent under the irradiation of ultra-violet light. X-ray photoelectron spectroscopy characterization demonstrates that the O/C atomic ratio for C-dots change to from 0.207 to 0.436 due to the chemical oxidation process. The photo bleaching experiment reveals that the C-dots show excellent photostability as compared with the conventional organic dyes, fluorescein and rhodamine B. The fluorescence intensity of the C-dots did not change significantly in the pH range of 3–10. To further enhance the fluorescence quantum yield, the C-dots were surface modified with four types of passivation ligands, 4,7,10-trioxa-1,13-tridecanediamine (TTDDA), poly-L-lysine (PLL), cysteine and chitosan and the fluorescence quantum yields of the TTDDA, PLL, cysteine and chitosan passivated C-dots were improved 1.53-, 5.94-, 2.00- and 3.68-fold, respectively. Fourier-transform infrared (FTIR) spectra were employed to characterize the surface groups of the C-dots. The bio-application of the C-dots as fluorescent bio-probes was evaluated in cell imaging and ex vivo fish imaging, which suggests that the C-dots may have potential applications in biolabeling and bioimaging.

Modulated exciton-plasmon interactions in Au-SiO_2-CdTe composite nanoparticles

Well-defined Au-SiO(2)-CdTe composite nanoparticles were synthesized via a multistep chemical approach in water solution to gain insight into the interaction between metal and semiconductor nanostructures. Photoluminescence measurement reveals that the fluorescence of CdTe quantum dots (QDs) in this composite with optimized SiO(2) thickness (4 nm) has over ten times enhancement compared with that of bare CdTe QDs. The considerable fluorescence enhancement of CdTe QDs is attributed to the surface plasmon resonance, which is further confirmed by the lifetime measurement. The enhanced fluorescence can be used to improve the performance of CdTe QDs as fluorescence probe and may find potential applications in biolabeling.

Facile fabrication of water-soluble Ln3+-doped β-NaGdF4 nanocrystals (Ln = Ce, Tb, Eu, Dy) with multicolor luminescence and magnetic properties

Water-soluble Ln3+-doped β-NaGdF4 (Ln=Ce, Tb, Eu, Dy) nanocrystals were synthesized via a hydrothermal method followed by phase transferring. The nanocrystals crystallize in the hexagonal phase as β-NaGdF4. Tunable multicolor down-conversion emissions can be achieved from Ln3+-doped β-NaGdF4 nanocrystals under a single ultraviolet excitation. During the down-conversion emission, energy transfer process like Ce3+→Gd3+→(Gd3+)n→Ln3+ occurred, in which Gd3+ ions play an important intermediate role. The magnetic properties of the obtained nanocrystals were investigated in detail. The nanocrystals display paramagnetic and superparamagnetic properties with mass magnetic susceptibility values of 6.77×10−5emu/g · Oe and 1.92×10−3emu/g · Oe at 300K and 2K, respectively. The T1-weighted magnetic resonance image that measured in aqueous solutions with different Gd3+ concentrations reveals the contrast brightening increases with the concentration of Gd3+ ions. Such magnetic/luminescent dual-function material may have promising applications in multiple biolabels and magnetic resonance imaging.

Synthesis of NaYF4:Eu3+/Tb3+ nanostructures with diverse morphologies and their size- and morphology-dependent photoluminescence

Cubic α- and hexagonal β-phase lanthanide luminescent NaYF4:Eu3+/Tb3+ nanostructures with diverse morphologies were successfully synthesized via a mild solvothermal method. The effects of the synthetic parameters on the crystal phase structure, size and morphology of NaYF4:Eu3+/Tb3+ nanostructures were systematically investigated. By modifying the synthetic parameters, the crystal phase structure, size and morphology were well controlled, and the phase transition from cubic α- to hexagonal β- can be easily realized. Furthermore, the morphology evolution is revealed, and the surfactant modulating formation mechanisms with diverse morphologies was proposed. The photoluminescence properties were found to be in close correlation with their composition, phase structure and morphology. NaYF4:Eu3+/Tb3+ nanostructures possessing unique morphologies and highly efficient luminescence may find potential applications in optoelectronics, sensors and biolabels.

Fluorescent monomers as building blocks for dye labeled polymers: synthesis and application in energy conversion, biolabeling and sensors

This review focuses on side-chain functionalized polymers derived from direct (co)polymerization of fluorescent dyes. This overview about polymerizable dyes includes 1,8-naphthalimides, fluoresceins, rhodamines, coumarins, azo-dyes, oxadiazoles, diverse aromatic dyes as well as selected other dyes that cannot be classified within these groups. The discussed dyes have been functionalized with a polymerizable unit in order to apply straight-forward polymerization procedures. Therefore, the center of attention is set to the optical properties of the polymerizable dyes and the applicable polymerization techniques. Furthermore, the various applications (i.e., in biomedicine and pharmacy, as thermo-responsive materials and energy transfer materials, for dispersion of carbon nanotubes and others) of each polymer are discussed.

A new inorganic–organic hybrid In2Se3(en) as hollow nanospheres: hydrothermal synthesis and near-infrared photoluminescence properties

A new inorganic-organic hybrid In(2)Se(3)(en) was synthesized as hollow nanospheres via a facile and controllable hydrothermal method in a system containing ethylenediamine (en) and hydrazine hydrate. These as-obtained hybrid hollow nanospheres with an average diameter of 200 nm were assembled by irregularly small-sized (ca. 20 nm) nanoparticles. These hollow nanospheres were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The surface chemical composition of the In(2)Se(3)(en) hollow nanospheres were studied by X-ray photoelectron spectroscopy (XPS). The possible gas bubble-template growth mechanism is proposed to understand the formation of In(2)Se(3)(en) hollow nanospheres. Room-temperature UV-vis diffuse reflection spectra and photoluminescence (PL) spectra indicate that the as-obtained hybrid nanospheres possess a maximum absorption at 470 nm and single strong near-infrared emission peak centered at 1092 nm. The near-infrared luminescence endows the hybrid nanospheres with potential application in telecommunications, biolabeling and biomedical imaging, etc.

A facile fabrication of spherical and beanpod-like magnetic-fluorescent particles with targeting functionalities

Magnetic-fluorescent particles with targeting functionalities were fabricated by a modified Stöber method and two shapes (spherical and beanpod-like) were obtained by simply tuning the reaction temperature. The two multifunctional probes combined the useful functions of magnetism, fluorescence and FA (folic acid)-targeting recognition into one entity. The products were characterized by scanning electron microscopy, transmission electron microscopy, photoluminescence spectroscopy, confocal laser scanning microscopy, by a superconducting quantum interference device and by Fourier transform infrared spectroscopy. The experimental results show that the products possessed rapid magnetic response, relatively strong fluorescent signal, higher photostability and FA-targeting recognition as well as good water-dispersibility, suggesting that they would have potential medical applications in biolabeling and bioimaging.

Highly Luminescent–Paramagnetic Nanophosphor Probes for In Vitro High‐Contrast Imaging of Human Breast Cancer Cells

Highly luminescent-paramagnetic nanophosphors have a seminal role in biotechnology and biomedical research due to their potential applications in biolabeling, bioimaging, and drug delivery. Herein, the synthesis of high-quality, ultrafine, europium-doped yttrium oxide nanophosphors (Y(1.9)O(3):Eu(0.1)(3+)) using a modified sol-gel technique is reported and in vitro fluorescence imaging studies are demonstrated in human breast cancer cells. These highly luminescent nanophosphors with an average particle size of ≈6 nm provide high-contrast optical imaging and decreased light scattering. In vitro cellular uptake is shown by fluorescence microscopy, which visualizes the characteristic intense hypersensitive red emission of Eu(3+) peaking at 610 nm ((5)D(0)-(7)F(2)) upon 246 nm UV light excitation. No apparent cytotoxicity is observed. Subsequently, time-resolved emission spectroscopy and SQUID magnetometry measurements demonstrate a photoluminescence decay time in milliseconds and paramagnetic behavior, which assure applications of the nanophosphors in biomedical studies.

Aqueous Synthesis of Glutathione-Capped CdTe/CdS/ZnS and CdTe/CdSe/ZnS Core/Shell/Shell Nanocrystal Heterostructures

Here we demonstrate the aqueous synthesis of colloidal nanocrystal heterostructures consisting of the CdTe core encapsulated by CdS/ZnS or CdSe/ZnS shells using glutathione (GSH), a tripeptide, as the capping ligand. The inner CdTe/CdS and CdTe/CdSe heterostructures have type-I, quasi-type-II, or type-II band offsets depending on the core size and shell thickness, and the outer CdS/ZnS and CdSe/ZnS structures have type-I band offsets. The emission maxima of the assembled heterostructures were found to be dependent on the CdTe core size, with a wider range of spectral tunability observed for the smaller cores. Because of encapsulation effects, the formation of successive shells resulted in a considerable increase in the photoluminescence quantum yield; however, identifying optimal shell thicknesses was required to achieve the maximum quantum yield. Photoluminescence lifetime measurements revealed that the decrease in the quantum yield of thick-shell nanocrystals was caused by a substantial decrease in the radiative rate constant. By tuning the diameter of the core and the thickness of each shell, a broad range of high quantum yield (up to 45%) nanocrystal heterostructures with emission ranging from visible to NIR wavelengths (500-730 nm) were obtained. This versatile route to engineering the optical properties of nanocrystal heterostructures will provide new opportunities for applications in bioimaging and biolabeling.

Preparation and characterization of CS–Fe3O4@ZnS:Mn magnetic-fluorescent nanoparticles in aqueous media

Chitosan (CS) coated magnetic-fluorescent nanoparticles (CS–Fe3O4@ZnS:Mn) were synthesized in aqueous media under ambient pressure and characterized by X-ray diffraction, UV–vis absorption, fluorescence emission, transmission electron microscope and energy dispersion spectrum. The effects of experimental conditions on the fluorescence properties of CS–Fe3O4@ZnS:Mn were studied. It was found that the chitosan coating on the surface of Fe3O4 could effectively suppress the interaction between Fe3O4 and ZnS:Mn, as well as providing appropriate functional groups for the synthesis and modification of ZnS:Mn semiconductor nanocrystals. The obtained multifunctional nanoparticles are promising candidates for applications in simultaneous biolabeling, imaging, cell sorting and separation.

Microwave‐Assisted Aqueous Synthesis of Small‐Sized, Highly Luminescent CdSeS/ZnS Core/Shell Quantum Dots for Live Cell Imaging

AbstractThis study develops a reliable aqueous‐phase method for the synthesis of CdSeS/ZnS core/shell QDs employing microwave irradiation technique. Firstly, CdSeS core QDs were produced by heating a precursor solution containing Cd2+, 3‐mercaptopropionic acid (MPA) and Na2SeSO3 at 130 °C for 30 min. After purification through centrifugation, the CdSeS core QDs were successfully capped with a ZnS shell through heating a capping solution containing Zn2+, S2– and MPA at 100 °C for 1 h. Both the core/shell QDs and core QDs were characterised by X‐ray powder diffraction, transmission electron microscopy and X‐ray photoelectron spectroscopy, and the epitaxial growth of a ZnS shell on the surface of CdSeS QDs was confirmed. The prepared CdSeS/ZnS core/shell QDs showed significantly enhanced luminescence and photostability than that of CdSeS core QDs. Finally, the CdSeS/ZnS core/shell QDs were applied to image live Hela cells. The pilot experiments showed that the cells were successfully stained and exhibited bright green fluorescence. The small size QDs were localised predominantly in the nuclear compartment of Hela cells with negligible cytotoxicity, even at a concentration of 300 μg mL−1 after 24 h incubation. Our results suggest that the new core/shell QDs could be highly biocompatible and have wide applications in biolabelling and imaging.

Monodisperse Lanthanide Fluoride Nanocrystals: Synthesis and Luminescent Properties

Three types of high-quality, monodisperse lanthanide fluoride colloidal nanocrystals (NCs) including LnF(3) (Ln = La-Pr), NaLnF(4) (Ln = Sm-Er), and Na(5)Ln(9)F(32) (Ln = Tm-Lu) with two crystal phases (hexagonal and cubic) and a rich variety of morphologies have been synthesized in high boiling organic solvents oleic acid and 1-octadecene, via a thermal decomposition pathway. The as-synthesized NCs were well characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence (PL) spectra, respectively. It is found that the as-synthesized NCs consist of monodisperse nanoparticles with diverse shapes and narrow size distribution, which can easily disperse in nonpolar cyclohexane solvent. Additionally, a possible mechanism of NC nucleation and growth has been proposed. The results reveal that the formation of monodisperse NCs closely correlates with the inherent nature of lanthanide series from La to Lu. Under 980 nm NIR excitation, as-synthesized Yb(3+)/Ln(3+) (Ln = Er, Tm, Ho)-doped NaGdF(4) and Na(5)Lu(9)F(32) colloidal NCs show the respective characteristic up-conversion (UC) emissions of Er(3+), Tm(3+), and Ho(3+), which are promising for applications in biolabels, bioimaging, displays, and other optical technologies.

Synthesis and characterization of bifunctional terbium complex-based nanoparticles

Novel bifunctional terbium complex-based nanoparticles were developed using a modified Stober method and a layer-by-layer assembly process. A magnetic core of Fe3O4 nanoparticles was coated with a silica shell to form the first layer. Then a ternary Tb3+ complex (TESPPA-Tb), which acted as a luminescent marker, was covalently bound to the silica surface by stable Si-O-Si bonds. The TESPPA monomer was synthesized by binding pyridine 2,6-dicarboxylic acid to 3-aminopropyltriethoxysilane, which was used as a ligand for coordination with the Tb3+ ions. An outer shell of silica was applied to the nanoparticles to allow for versatility with surface functionalization. The nanoparticles were characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, vibration sample magnetometer, and photoluminescence spectroscopy. The bifunctional nanoparticles exhibited favorable superparamagnetic behavior and photoluminescence properties of Tb3+. These nanoparticles have potential applications in biolabeling, bioseparation, immunoassays, and pathogenic diagnosis.

Structural and magnetic properties of mesoporous SiO2 nanoparticles impregnated with iron oxide or cobalt-iron oxide nanocrystals

Magnetic nanocomposites of FeOx@SiO2 and CoFe2O4@SiO2 were prepared via a wet-impregnation route using mesoporous silica nanoparticles as a support matrix. The small pores in the matrix were exploited as nanocavities for controlled growth of the embedded oxide phase, initially examined by introducing different wt% loadings of FeOx in four different samples and sequentially treating them under oxidising and reducing conditions. Comparative examination of the morphological and structural properties of the FeOx@SiO2 compositions shows that a 17 wt% (nominal) loading of the oxide phase, a mixture of Fe3O4 (magnetite) and γ-Fe2O3 (maghemite), is fully embedded within the pores. The 60–70 nm dimensions of the SiO2 nanoparticles are visible in TEM micrographs which reveal a spheroidal shape. TEM also shows a ca. 3 nm size for the crystalline oxide particles embedded within, which agrees with the pore sizes estimated through porosimetric analysis. The measurements for field-cooled (FC), zero-field-cooled (ZFC) magnetizations, and hysteresis loops in the temperature range of 3 K to 300 K reveal that an enhancement in the density of magnetization is obtained for the 17 wt% FeOx@SiO2 sample following reductive thermal treatment. A CoFe2O4@SiO2 nanocomposite prepared with a nominal 14 wt% oxide shows comparable structure and morphology to the 17 wt% FeOx@SiO2 sample, yet superior magnetic properties. The higher density of magnetization in CoFe2O4@SiO2 is attributed to its 40% content of magnetic material in the crystalline phase, versus 6–8% in FeOx@SiO2. Efficient surface functionalisation with APTES, monitored by DRIFT-IR, implies that the magnetic nanocomposites could be used in bio-labelling applications. Data derived from Raman spectroscopy, N2 adsorption/desorption measurements, and TGA are also used to characterise the nanocomposite materials.

Room temperature synthesis of hydrophilic Ln3+-doped KGdF4 (Ln = Ce, Eu, Tb, Dy) nanoparticles with controllable size: energy transfer, size-dependent and color-tunable luminescence properties

In this paper, we demonstrate a simple, template-free, reproducible and one-step synthesis of hydrophilic KGdF(4): Ln(3+) (Ln = Ce, Eu, Tb and Dy) nanoparticles (NPs) via a solution-based route at room temperature. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and cathodoluminescence (CL) spectra are used to characterize the samples. The results indicate that the use of water-diethyleneglycol (DEG) solvent mixture as the reaction medium not only allows facile particle size control but also endows the as-prepared samples with good water-solubility. In particular, the mean size of NPs is monotonously reduced with the increase of DEG content, from 215 to 40 nm. The luminescence intensity and absolute quantum yields for KGdF(4): Ce(3+), Tb(3+) NPs increase remarkably with particle sizes ranging from 40 to 215 nm. Additionally, we systematically investigate the magnetic and luminescence properties of KGdF(4): Ln(3+) (Ln = Ce, Eu, Tb and Dy) NPs. They display paramagnetic and superparamagnetic properties with mass magnetic susceptibility values of 1.03 × 10(-4) emu g(-1)·Oe and 3.09 × 10(-3) emu g(-1)·Oe at 300 K and 2 K, respectively, and multicolor emissions due to the energy transfer (ET) process Ce(3+)→ Gd(3+)→ (Gd(3+))(n)→ Ln(3+), in which Gd(3+) ions play an intermediate role in this process. Representatively, it is shown that the energy transfer from Ce(3+) to Tb(3+) occurs mainly via the dipole-quadrupole interaction by comparison of the theoretical calculation and experimental results. This kind of magnetic/luminescent dual-function materials may have promising applications in multiple biolabels and MR imaging.

Combustion synthesis and characterization of Er3+-doped and Er3+, Yb3+-codoped YVO4 nanophosphors oriented for luminescent biolabeling applications

YVO 4:Er 3+ and YVO 4:Er 3+, Yb 3+ nanomaterials were prepared via combustion synthesis using urea as fuel and metal nitrates as precursor. The morphology and the structure of the prepared samples were characterized by x-ray diffraction, scanning electron microscopy and transmission electron microscopy. The average size of the prepared materials ranged from 20 to 30 nm in diameter. The effects of Er 3+ and Yb 3+ doping concentrations on structure and optical properties have been investigated. Optical properties of YVO 4:Er 3+ and YVO 4:Er 3+, Yb 3+ nanoparticles were measured by photoluminescent excitation and emission spectroscopies. For the YVO 4:Er 3+ and YVO 4:Er 3+, Yb 3+ samples, two strong green emissions centered at 524 and 552 nm are found, corresponding to the 2 H 11/2—4 I 15/2 and 4 S 11/2—4 I 15/2 transitions of Er 3+ ions, respectively. Upconversion emission in the green region of the YVO 4:Er 3+ nanoparticles under 980 nm excitation was also investigated. Strong emission from these materials is promising for luminescent biolabeling applications.

A versatile access to new halogenated 7-azidocoumarins for photoaffinity labeling: Synthesis and photophysical properties

A versatile methodology for the synthesis of 6/8-halogenated 7-aminocoumarins from the corresponding 7-hydroxy analogs using Pd-catalyzed amination reaction as the key step is presented. Further readily conversion into 7-azidocoumarins was performed and the resulting aryl azides proved higher stability and reactivity than the corresponding non-halogenated parent compound. These new compounds may thus constitute attractive scaffolds for designing novel photoaffinity reagents for various challenging bio-labeling applications.

Synthesis and optical properties of water-soluble fluoride nanophosphors co-doped with Eu 3+ and Tb 3+

The synthesis, structure and optical properties of water-soluble fluoride nanophosphors co-doped with Eu 3+ and Tb 3+ are presented. Nanocrystals of NaYF 4 were synthesized via a hydrothermal microwave-assisted technique. XRD, TEM, AFM, FTIR as well as photoluminescence (PL) spectra were used to characterize the doped nanocrystals. The average size of nanocrystals, determined from XRD, AFM and TEM measurements, was ca. 28 nm. It was found that energy transfer occurs between Tb 3+ and Eu 3+ ions embedded in NaYF 4 matrix, both in nanocrystals dispersed in chloroform and those in aqueous solution. We demonstrate that this simple colloidal system possesses the essential features required for both energy transfer and potential application in biolabeling.

Luminescent evolution of hybrid SiO 2-coated CdTe NCs

CdTe nanocrystals (NCs) were coated with a hybrid SiO 2 shell containing CdS-like clusters by a facile reflux. These hybrid SiO 2-coated CdTe NCs exhibited tunable photoluminescence (PL) and high fluorescence quantum yields (QYs) up to 70% (the QY of initial CdTe NCs is 24%) due to the CdS-like cluster in the SiO 2 shell nearby the CdTe core. The average fluorescence lifetime of the hybrid SiO 2-coated NCs and the CdTe NCs are 36 and 25 ns, respectively. Because increased fluorescence QYs and slightly blue-shifted PL peak wavelength for these hybrid NCs were observed after the removing of TGA and Cd 2+, the hybrid SiO 2 shell can sufficiently passivate PL, improve chemical stability, and prevent the surface deterioration of the CdTe NCs. This is crucial for applications in biolabeling and optoelectronic devices.