Many sulfides are toxic substances that easily harm the respiratory tract, therefore affecting respiratory function or damaging other organs of the body, leading to its failure. Therefore, there is a pressing need to develop methods for sensitive detection of sulfur ions (S2?). Based on luminescence resonance energy transfer (LRET) theory, we report the construction of a near‐infrared (NIR) excitation luminescence probe using NaGdF4:Yb3+,Er3+@NaYF4 upconversion nanoparticles (UCNPs) as the donor and dye‐670 as the receptor for detection of S2?. When UCNPs and dye‐670 molecules were combined using ligand exchange and electrostatic attraction, LRET occurred and UCNP luminescence was quenched. When S2? was added to the system, sulfide ions were able to destroy the double bond of the dye, inhibiting LRET and restoring UCNP luminescence. Under optimum condition, the linear range of S2? detection was 0.65–18.2 μM, and the detection limit was 34.2 nM. This method was applied for determination of S2? in water with satisfactory results. 相似文献
Lanthanide‐doped upconversion nanoparticles (UCNPs) have attracted widespread interests in the field of biomedicine because of their unique upconverting capability by converting near infrared (NIR) excitation to visible or ultraviolet (UV) emission. Here, we developed a novel UCNP‐based substrate for dynamic capture and release of cancer cells and pathogenic bacteria under NIR‐control. The UCNPs harvest NIR light and convert it to ultraviolet light, which subsequently result in the cleavage of photoresponsive linker (PR linker) from the substrate, and on demand allows the release of a captured cell. The results show that after seeding cells for 5 h, the cells were efficiently captured on the surface of the substrate and ?89.4% of the originally captured S. aureus was released from the surface after exposure to 2 W/cm2 NIR light for 30 min, and ?92.1% of HepG2 cells. These findings provide a unique platform for exploring an entirely new application field for this promising luminescent nanomaterial.
In this study, Bi3+ incorporation in NaYbF4:Er lattice and its influence on upconversion luminescence properties have been investigated in detail using techniques such as temperature‐dependent luminescence, Fourier transform infrared spectroscopy and X‐ray diffraction (XRD). The study was carried out to develop phosphors with improved upconversion luminescence. From photoluminescence and lifetime measurements it is inferred that luminescence intensity from NaYbF4:Er increases with Bi3+ addition. The sample containing 50 at.% Bi3+ ions exhibited optimum upconversion luminescence. Increased distance between Yb3+–Yb3+ and Er3+–Er3+ due to Bi3+ incorporation into the lattice and associated decrease in the extent of dipolar interaction/self‐quenching are responsible for increase in lifetime values and luminescence intensities from Er3+ ions. Incorporation of Bi3+ into NaYbF4:Er lattice reduced self‐quenching among Yb3+–Yb3+ions and this facilitated energy transfer from Yb3+ to Er3+. This situation also explains decrease in the extent of temperature‐assisted quenching of emission from thermally coupled 2H11/2 and 4S3/2 levels of Er3+. Based on Rietveld refinement of XRD patterns it was confirmed that a maximum of 10 at.% of Bi3+added was incorporated into the NaYbF4:Er lattice and the remaining complex co‐exists as a BiOF phase. These results are of significant interest in the area of development of phosphors based on Yb3+–Er3+ upconversion luminescence. 相似文献
Recently, lanthanide (Ln) luminescent nanocrystals have attracted increasing attention in various fields such as biomedical imaging, lasers, and anticounterfeiting. However, due to the forbidden 4f–4f transition of lanthanide ions, the absorption cross-section and luminescence brightness of lanthanide nanocrystals are limited. To address the challenge, we constructed an optical oscillator-like system to repeatedly simulate lanthanide nanocrystals to enhance the absorption efficiency of lanthanide ions on excitation photons. In this optical system, the upconversion luminescence (UCL) of Tm3+ emission of ~450 nm excited by a 980 nm laser can be amplified by a factor beyond 104. The corresponding downshifting luminescence of Tm3+ at 1460 nm was enhanced by three orders of magnitude. We also demonstrated that the significant luminescence enhancement in the designed optical oscillator-like system was general for various lanthanide nanocrystals including NaYF4:Yb3+/Ln3+, NaErF4@NaYF4 and NaYF4:Yb3+/Ln3+@NaYF4:Yb3+@NaYF4 (Ln = Er, Tm, Ho) regardless of the wavelengths of excitation sources (808 and 980 nm). The mechanism study revealed that both elevated laser power in the optical system and multiple excitations on lanthanide nanocrystals were the main reason for the luminescence amplification. Our findings may benefit the future development of low-threshold upconversion and downshifting luminescence of lanthanide nanocrystals and expand their applications. 相似文献
High-quality NaYF4:Yb/Er/Gd up-conversion nanoparticles (UCNPs) were first synthesized by a solvothermal method using rare earth stearate, sodium fluoride, ethanol, water, and oleic acid as precursors. Doped Gd3+ ions can promote the transition of NaYF4 from cubic to hexagonal phase, shorten the reaction time, and reduce the reaction temperature without reducing the luminescence intensity of NaYF4:Yb/Er UCNPs. X-ray diffraction, infrared spectroscopy, transmission electron microscopy, and luminescence spectroscopy were applied to characterize the UCNPs. The nanoparticles exhibited small size and excellent green up-conversion photoluminescence, making them suitable for biological applications. After the surfaces of NaYF4:Yb/Er/Gd UCNPs were modified with amino groups through the Stöber method, they could be brought close enough to the analytically important protein called R-phycoerythrin (R-PE) bearing multiple carboxyl groups so that energy transfer could occur. A luminescence resonance energy transfer (LRET) system was developed using NaYF4:Yb/Er/Gd UCNPs as an energy donor and R-PE as an energy acceptor. As a result, a detection limit of R-PE of 0.5 μg/ml was achieved by the LRET system with a relative standard deviation of 2.0%. Although this approach was first used successfully to detect R-PE, it can also be extended to the detection of other biological molecules. 相似文献
An redox luminescence switch was developed for the sensing of glutathione (GSH), l ‐cysteine (Cys) or l ‐ascorbic acid (AA) based on redox reaction. The Mn2+‐doped NaYF4:Yb,Er upconversion nanorods (UCNRs) with an emission peak located in the red region were synthesized. The luminescence intensity of the UCNRs could be quenched due to the Mn2+ could be oxidized to MnO2 by KMnO4. Subsequently, when the AA, GSH or Cys was added into the MnO2 modified upconversion nanosystem, which could reduced MnO2 to Mn2+ and the luminescence intensity was recovered. The concentration ranges of the nanosystem are 0.500–3.375 mM (R2 = 0.99) for AA, 0.6250–11.88 mM (R2 = 0.99) for GSH and 0.6250–9.375 mM (R2 = 0.99) for Cys, respectively. 相似文献
Tin oxide (SnO2) nanocrystalline powders doped with erbium ion (Er3+) in different molar ratios (0, 3, 5, and 7 mol%) were prepared using a solid-state reaction technique. These samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible absorption, visible upconversion, and near-infrared luminescence techniques. XRD analysis revealed the tetragonal rutile structure of SnO2 and the average crystallite size was about 32 nm. From Tauc's plots, it was confirmed that the substitution of Er3+ ions into the SnO2 host lattice resulted in the narrowing its band gap. Optical absorption bands at 520 and 654 nm correspond to the 4f electron transitions of Er3+ further confirming visible light absorption. Infrared luminescence spectra showed a broad band centred at 1536 nm which is assigned to the 4I13/2 → 4I15/2 transition of Er3+. Visible upconverted emission spectra under 980 nm excitation exhibit a strong red luminescence with a main peak at 672 nm which is attributed to the 4F9/2 → 4I15/2 transition of Er3+. Power-dependent upconversion spectra confirmed that two photons participated in the upconversion mechanism. Enhancement in the intensities of both visible and infrared luminescence was observed when raising the concentration. The results pave the way for the potential applications of these nanocrystalline powders in energy harvesting applications such as infrared light upconverting layer in solar cells, light emitting diodes, infrared broadband sources and amplifiers, and biological labelling. 相似文献
Lanthanide (Ln)-doped upconversion nanoparticles (UCNPs) with appropriate surface modification can be used for a wide range of biomedical applications such as bio-detection, cancer therapy, bio-labeling, fluorescence imaging, magnetic resonance imaging and drug delivery. The upconversion phenomenon exhibited by Ln-doped UCNPs renders them tremendous advantages in biological applications over other types of fluorescent materials (e.g., organic dyes, fluorescent proteins, gold nanoparticles, quantum dots, and luminescent transition metal complexes) for: (i) enhanced tissue penetration depths achieved by near-infrared (NIR) excitation; (ii) improved stability against photobleaching, photoblinking and photochemical degradation; (iii) non-photodamaging to DNA/RNA due to lower excitation light energy; (iv) lower cytotoxicity; and (v) higher detection sensitivity. Ln-doped UCNPs are therefore attracting increasing attentions in recent years. In this review, we present recent advances in the synthesis of Ln-doped UCNPs and their surface modification, as well as their emerging applications in biomedicine. The future prospects of Ln-doped UCNPs for biomedical applications are also discussed. 相似文献
Co‐registered reflectance confocal microscopy (RCM) imaging and multiphoton microscopy (MPM) imaging of human skin in vivo provide complementary information about the cellular structures of skin. MPM image shows cytoplasm and nucleus, while RCM image shows cellular membranes and intercellular materials. Picture: H. Wang et al., pp. 305–309 in this issue 相似文献
Chimeraplasty is a novel methodology that uses chimeric RNA/DNA oligonucleotides (chimeraplasts) to stimulate genomic DNA repair. Efficient uptake and nuclear localization of intact chimeraplasts are key parameters to achieve optimal correction of mutation defects into specific cell types.
Methods
A 5′‐end FITC‐labeled 68‐mer RNA/DNA oligonucleotide was complexed with the polycation polyethylenimine (PEI) and the cationic lipids Cytofectin and GenePorter. Flow cytometry was employed to evaluate chimeraplast uptake under different conditions. Intracellular chimeraplast distribution and co‐localization with endocytosis markers were assessed by confocal microscopy. Relative quantification of chimeraplast metabolism was performed by denaturing PAGE and GeneScan? analysis.
Results
In airway epithelial cells, optimized chimeraplast uptake reached near 100% efficiency with the carriers tested. However, chimeraplast nuclear localization could only be achieved using PEI or Cytofectin. Chimeraplast/GenePorter lipoplexes were retained in the cytoplasm. PEI polyplexes and Cytofectin lipoplexes displayed different uptake rates and internalization mechanisms. Chimeraplast/PEI polyplexes were internalized at least partially by fluid‐phase endocytosis. In contrast, phagocytosis may have contributed to the internalization process of large‐sized chimeraplast/Cytofectin lipoplexes. Moreover, significant chimeraplast degradation was detected 24 h after transfection with both PEI polyplexes and Cytofectin lipoplexes, although the latter seemed to confer a higher degree of protection against nuclease degradation.
Trivalent europium (Eu3+) and terbium (Tb3+) ions are important activator centers used in different host lattices to produce red and green emitting materials. The current work shows the design of new clay minerals to act as host lattices for rare earth (RE) ions. Based on the hectorite structure, nano‐chlorohectorites and nano‐fluorohectorites were developed by replacing the OH? present in the hectorite structure with Cl? or F?, thus avoiding the luminescence quenching expected due to the OH? groups. The produced matrices were characterized through X‐ray powder diffraction (XPD), transmission electron microscopy (TEM), FT‐IR, 29Si MAS (magic angle spinning) NMR, nitrogen sorption, thermogravimetry‐differential scanning calorimetry (TGA‐DSC) and luminescence measurements, indicating all good features expected from a host lattice for RE ions. The nano‐clay materials were successfully doped with Eu3+ and/or Tb3+ to yield materials preserving the hectorite crystal structure and showing the related luminescence emissions. Thus, the present work shows that efficient RE3+ luminescence can be obtained from clays without the use of organic ‘antenna’ molecules. 相似文献
With tunable excitation light, multiphoton microscopy is widely used for imaging biological structures at subcellular resolution. Axial chromatic dispersion, present in virtually every transmissive optical system including the multiphoton microscope, leads to focal (and the resultant image) plane separation. Here, we experimentally demonstrate a technique to measure the axial chromatic dispersion in a multiphoton microscope, using simultaneous 2‐color third‐harmonic generation imaging excited by a 2‐color soliton source with tunable wavelength separation. Our technique is self‐referenced, eliminating potential measurement error when 1‐color tunable excitation light is used which necessitates reciprocating motion of the mechanical translation stage. Using this technique, we demonstrate measured axial chromatic dispersion with 2 different objective lenses in a multiphoton microscope. Further measurement in a biological sample also indicates that this axial chromatic dispersion, in combination with 2‐color imaging, may open up opportunity for simultaneous imaging of 2 different axial planes. 相似文献
High cell densities for transient transfection with polyethyleneimine (PEI) can be used for rapid and maximal production of recombinant proteins. High cell densities can be obtained by different cultivation systems, such as batch or perfusion systems. Herein, densities up to 18 million cells/mL were obtained by centrifugation for transfection evaluation. PEI transfection efficiency was easily determined by transfected enhanced green fluorescence protein (EGFP) reporter plasmid DNA (pDNA). A linear correlation between fluorescence intensity and transfection efficiency was improved. The transfection efficiency of PEI was highly dependent on the transfection conditions and directly related to the level of recombinant protein. Several factors were required to optimize the transient transfection process; these factors included the media type (which is compatible with low or high cell density transfection), the preculture CHO‐K1 suspension cell density, and the pDNA to PEI level. Based on design of experiment (DoE) analyses, the optimal transfection conditions for 10 × 106 cells/mL in the CHOMACS CD medium achieved 73% transfection efficiency and a cell viability of over 80%. These results were confirmed for the production of transforming growth factor‐beta 1 (TGF‐β1) in a shake flask. The purified TGF‐β1 protein concentration from 60 mL supernatant was 27 µg/mL, and the protein was biologically active. 相似文献
Fluo-3 is widely used to study cell calcium. Two traditional approaches: (1) direct injection and (2) Fluo-3 acetoxymethyl ester (AM) loading, often bring conflicting results in cytoplasmic calcium ([Ca2+]c) and nuclear calcium ([Ca2+]n) imaging. AM loading usually yields a darker nucleus than in cytoplasm, while direct injection always induces a brighter nucleus which is more responsive to [Ca2+]n detection. In this work, we detailedly investigated the effects of loading and de-esterification temperatures on the fluorescence intensity of Fluo-3 in response to [Ca2+]n and [Ca2+]c in adherent cells, including osteoblast, HeLa and BV2 cells. Interestingly, it showed that fluorescence intensity of nucleus in osteoblast cells was about two times larger than that of cytoplasm when cells were loaded with Fluo-3 AM at 4 °C and allowed a subsequent step for de-esterification at 20 °C. Brighter nuclei were also acquired in HeLa and BV2 cells using the same experimental condition. Furthermore, loading time and adhesion quality of cells had effect on fluorescence intensity. Taken together, cold loading and room temperature de-esterification treatment of Fluo-3 AM selectively yielded brighter nucleus in adherent cells. 相似文献
More recently, tremendous progress has been achieved in the development of two‐dimensional semiconductor materials applied in catalyst, energy application, sensor device and bioengineering since the birth of graphene isolated from graphite. Layered molybdenum disulfide (MoS2) as an indirect gap semiconductor can efficiently emit photoluminescence (PL) excited by visible light, which shows a great potential in adaptive biological imaging. However, 1 photon PL of MoS2 for cell imaging purposes suffers from strong autofluorescence and ion‐induced PL quenching. Herein, we report single layer small chitosan decorated MoS2 nanosheets as a nonbleaching, nonblinking optical nanoprobe under near infrared femtosecond laser excitation and their applications for strong 2 photon luminescence (TPL) and strong second harmonic generation (SHG) bioimaging. Furthermore, the TPL can resist the ion‐induced quenching on the cellular membrane. The proposed TPL and SHG of single‐layer MoS2 show great potential for real‐time, deep, multiphoton and three‐dimensional bioimaging under low‐power laser excitation. 相似文献