Rapid fluorescent detection of neurogenin3 by CdTe quantum dot aggregation

Here we report a facile immunoassay for detecting a synthetic peptide fragment of neurogenin3 (amino acid sequence: SKQRRSRRKKANDRERNRMH) by harnessing the aggregation-dependent fluorescence property of antibody-conjugated CdTe quantum dots in the presence of the target.     

Highly sensitive rare cell detection based on quantum dot probe fluorescence analysis

This study presents an efficient and sensitive method for detecting rare cells without cell culture, in which cells are analyzed quantitatively using quantum dots (QDs) as a fluorescent probe. By the conjugation of QDs with cells, the biotin–streptavidin reaction functions as a bridge to connect QDs and cells. The cells can be quantified based on the correlation of the QD fluorescence intensity with the cell population. Non-specific adsorption and cross-reaction of QD625–streptavidin on T cell membrane are neglected by reacting with biotin anti-human CD3 and mixing with red blood cell, respectively. Additionally, the photo-activation period and pH can be controlled to enhance the fluorescence of cell populations, which increases linearly with the number of T cells from 40 to 100,000, not only in a single T cell line but also in mixing with a total of 10⁶ red blood cells. Moreover, the specific T cells can be detected in less than 15 min, even though rare specific cells may number only 40 cells. Among the advantages, the proposed system for detecting rare cells include simplicity of preparation, low cost, rapid detection, and high sensitivity, all of which can facilitate the detection of circulating tumor cells in early stages of diagnosis or prognosis.      

A fluorescent turn-on probe for bisulfite based on hydrogen bond-inhibited C=N isomerization mechanism

A fluorescence turn-on probe for bisulfite has been developed by taking advantage of the specific reaction of bisulfite and aldehyde in combination with the hydrogen bond inhibited C=N isomerization mechanism. The practical value of this selective and sensitive fluorescent probe was confirmed by its application to detection of bisulfite in granulated sugar.     

A ratiometric fluorescent probe for cyanide based on FRET

On the basis of FRET from 4-(N,N-dimethylamino)benzamide to fluorescein, a new ratiometric fluorescence probe bearing a hydrazone binding unit was developed for highly selective and sensitive detection of CN(-) in aqueous solution.     

一种萘酰亚胺类荧光共振能量转移型光酸探针

合成了一种未见文献报道的键合螺噁嗪单元的1,8-萘二甲酰亚胺类化合物3,通过核磁共振谱和高分辨质谱确证了其结构.化合物在某些有机溶剂中和粉末状态下都能发射较强的荧光,研究了化合物3在二甲基亚砜中聚集诱导荧光增强(AIE)性质.在滤纸上以及用薄层层析硅胶(TLC)都能检测到螺噁嗪单元的光致变色现象;螺噁嗪单元酸致开环产物...     

Thiol-stabilized luminescent CdTe quantum dot as biological fluorescent probe for sensitive detection of methyl parathion by a fluoroimmunochromatographic technique

Quantum dots (QDs) are preferred as high-resolution biological fluorescent probes because of their inherent optical properties compared with organic dyes. This intrinsic property of QDs has been made use of for sensitive detection of methylparathion (MP) at picogramme levels. The specificity of the assay was attributed to highly specific immunological reactions. Competitive binding between free MP and CdTe QD bioconjugated MP (MP-BSA-CdTe) with immobilized anti-MP IgY antibodies was monitored in a flow-injection system. The fluorescence intensity of MP-BSA-CdTe bioconjugate eluted from the column was found to be directly proportional to the free MP concentration. Hence, it was possible to detect MP in a linear range of 0.1–1 ng mL⁻¹ with a regression coefficient R ² = 0.9905. In this investigation, IgY proved advantageous over IgG class immunoglobulins in terms of yield, stability, cost effectiveness, and enhancement of assay sensitivity. The photo-absorption spectrum of bioconjugated CdTe QD (λ _max = 310 nm) confirmed nano-biomolecular interactions. The results suggest the potential application of bioconjugation and nano-biomolecular interactions of QDs for biological labeling and target analyte detection with high sensitivity.     

Electrochemical immunoassay using quantum dot/antibody probe for identification of cyanobacterial hepatotoxin microcystin-LR

The presence of cyanobacterial hepatotoxins such as microcystin-LR poses health threats to humans due to their potential for causing severe physiological effects when contaminated drinking water is ingested. Here, the electrochemical detection of microcystin-LR is explored using a quantum dot/antibody (QD/Ab) probe for nanoparticle-based amplification and direct electrochemical transduction. The immunological recognition of microcystin-LR using the QD/Ab probe was amplified and converted to an electrochemical signal by measuring the cadmium ions released from QD based on square wave stripping voltammetry under optimized electrochemical factors. Whereas a qualitative analysis for microcystin-LR was achieved using the specific peak potential of the anodic voltammogram at −0.6 ± 0.05 V, concentration of the toxin was quantified based on the charge density of the anodic peak; a dynamic range of 0.227 to 50 μg/L and limit of detection of 0.099 μg/L were obtained with high sensitivity. The extracted microcystin-LR from Microcystis aeruginosa was estimated as 1,944 μg/g of dried weight of the microorganism.     

A unique two-photon fluorescent probe based on ICT mechanism for imaging palladium in living cells and mice

Palladium(0) as one of the vital transition metals, is employed in numerous industries, such as drug synthesis, aerospace high-tech field and automobile industry. When the Pd(0) enter into the body, it will bind with thiol-containing amino acids, DNA, RNA, and other biomolecules damaging to human health. Thus, developing a novel tool for monitoring and imaging of Pd(0) in vivo is very urgent. In the work, based on a intramolecular charge transfer (ICT) mechanism a two-photon fluorescent probe NIPd had been designed and synthesized for the recognition Pd(0). In vitro experiments data displayed that probe NIPd exhibited a 13-fold fluorescent increase for Pd(0) in 30 min in the aqueous solution with a detection limit of 16 nmol/L. It also showed the outstanding selectivity and antijamming performance. More importantly, NIPd could be served as a two-photon fluorescent probe for real-time monitoring Pd(0) in living cells and mice.     

A unique two-photon fluorescent probe based on ICT mechanism for imaging palladium in living cells and mice

Palladium(0) as one of the vital transition metals, is employed in numerous industries, such as drug synthesis, aerospace high-tech field and automobile industry. When the Pd(0) enter into the body, it will bind with thiol-containing amino acids, DNA, RNA, and other biomolecules damaging to human health. Thus, developing a novel tool for monitoring and imaging of Pd(0) in vivo is very urgent. In the work, based on a intramolecular charge transfer (ICT) mechanism a two-photon fluorescent probe NIPd had been designed and synthesized for the recognition Pd(0). In vitro experiments data displayed that probe NIPd exhibited a 13-fold fluorescent increase for Pd(0) in 30 min in the aqueous solution with a detection limit of 16 nmol/L. It also showed the outstanding selectivity and antijamming performance. More importantly, NIPd could be served as a two-photon fluorescent probe for real-time monitoring Pd(0) in living cells and mice.     

A fluorescent probe for the detection of Hg2+ based on rhodamine derivative and modified CdTe quantum dots

Research on Chemical Intermediates - In this paper, Zn doped CdTe quantum dots (CdTe:Zn QDs) was synthesized and imbedded in silica particles via a reverse microemulsion method to form a QDs/silica...     

Synthesis of molecularly imprinted fluorescent probe based on biomass-derived carbon quantum dots for detection of mesotrione

Analytical and Bioanalytical Chemistry - A novel fluorescent probe based on molecularly imprinted polymers (MIPs) coupled with carbon quantum dots (CQDs) was fabricated and successfully used for...     

Multiplex competitive microbead-based flow cytometric immunoassay using quantum dot fluorescent labels

In answer to the ever-increasing need to perform the simultaneous analysis of environmental hazards, microcarrier-based multiplex technologies show great promise. Further integration with biofunctionalized quantum dots (QDs) creates new opportunities to extend the capabilities of multicolor flow cytometry with their unique fluorescence properties. Here, we have developed a competitive microbead-based flow cytometric immunoassay using QDs fluorescent labels for simultaneous detection of two analytes, bringing the benefits of sensitive, rapid and easy-of-manipulation analytical tool for environmental contaminants. As model target compounds, the cyanobacterial toxin microcystin-LR and the polycyclic aromatic hydrocarbon compound benzo[a]pyrene were selected. The assay was carried out in two steps: the competitive immunological reaction of multiple targets using their exclusive sensing elements of QD/antibody detection probes and antigen-coated microsphere, and the subsequent flow cytometric analysis. The fluorescence of the QD-encoded microsphere was thus found to be inversely proportional to target analyte concentration. Under optimized conditions, the proposed assay performed well within 30 min for the identification and quantitative analysis of the two environmental contaminants. For microcystin-LR and benzo[a]pyrene, dose–response curves with IC₅₀ values of 5 μg L⁻¹ and 1.1 μg L⁻¹ and dynamic ranges of 0.52–30 μg L⁻¹ and 0.13–10 μg L⁻¹ were obtained, respectively. Recovery was 92.6–106.5% for 5 types of water samples like bottled water, tap water, surface water and seawater using only filtration as sample pretreatment.     

Immunoasssay based on the antibody-conjugated PAMAM-dendrimer-gold quantum dot complex

An immunoassay based upon photoluminescent gold quantum dots aimed at detecting human IgG in aqueous solution from micromolar to nanomolar concentrations is described.     

Nuclease tolerant FRET probe based on DNA-quantum dot conjugation.

We have developed a fluorescence resonance energy transfer (FRET) probe based on the conjugation of a quantum dot (QD) with dye (YOYO-3) intercalated DNA. The FRET-inducing electrostatic coupling of DNA and the QD made structural changes to the QD-DNA conjugates, which significantly prevented an enzymatic reaction between the DNA and a conventional restriction endonuclease (EcoRI).     

A regenerable fluorescent quantum dot based nanoprobe for zinc(II), and the design of a molecular logic gate

We report on a simple, sensitive and regenerable fluorescent nanoprobe for Zn(II) ion. It is based on the use of glutathione capped CdTe quantum dots (GSH-CdTe Q-dots). The bright fluorescence of these Q-dots is quenched on addition of diethylenetriaminepentaacetic acid (DTPA) due to the binding of DTPA to GSH. If, however, Zn(II) is added, it will bind DTPA and detach it from the surface of the Q-dots, this resulting in the fluorescence recovery. Under optimum conditions, the intensity of the restored fluorescence is proportional to the concentration of Zn(II) in the 0.48 to 90 μmol · L⁻¹ range, with a limit of detection of 0.14 μmol · L⁻¹. The nanoprobe was applied to the determination of Zn(II) in spiked tap water and river water and gave satisfactory results. The findings were also applied to design a molecular logic gate where DTPA acts as the first input to the system by quenching the fluorescence of the GSH-CdTe Q-dots. Zn(II) acts as the second input and causes the detachment of DTPA from the Q-dots and a restoration of fluorescence. This system therefore represents a new IMP (IMPLICATION) logic gate.

We describe a fluorescent nanoprobe for Zn(II) based on quantum dots, and its use in an IMP molecular logic gate. The nanoprobe was successfully applied to the determination of Zn(II) in spiked tap water and river water.

     

A highly selective fluorescent probe for Hg based on a rhodamine-coumarin conjugate

A fluorescent probe 1 for Hg²⁺ based on a rhodamine-coumarin conjugate was designed and synthesized. Probe 1 exhibits high sensitivity and selectivity for sensing Hg²⁺, and about a 24-fold increase in fluorescence emission intensity is observed upon binding excess Hg²⁺ in 50% water/ethanol buffered at pH 7.24. The fluorescence response to Hg²⁺ is attributed to the 1:1 complex formation between probe 1 and Hg²⁺, which has been utilized as the basis for the selective detection of Hg²⁺. Besides, probe 1 was also found to show a reversible dual chromo- and fluorogenic response toward Hg²⁺ likely due to the chelation-induced ring opening of rhodamine spirolactam. The analytical performance characteristics of the proposed Hg²⁺-sensitive probe were investigated. The linear response range covers a concentration range of Hg²⁺ from 8.0 × 10⁻⁸ to 1.0 × 10⁻⁵ mol L⁻¹ and the detection limit is 4.0 × 10⁻⁸ mol L⁻¹. The determination of Hg²⁺ in both tap and river water samples displays satisfactory results.     

A pH-responsive fluorescent probe and photosensitiser based on a self-quenched phthalocyanine dimer

A self-quenched zinc(ii) phthalocyanine dimer linked with an acid-sensitive ketal unit has been prepared, which can be activated in an acidic environment (pH = 5.0-6.5) as a result of the cleavage of the ketal linker and separation of the phthalocyanine units, resulting in enhanced fluorescence emission and singlet oxygen production.     

A new highly fluorescent probe for monosaccharides based on a donor-acceptor diphenyloxazole

A diphenyloxazole substituted with a dimethylamino and a boronic acid group showing intramolecular charge transfer in the excited state undergoes large spectral changes in the presence of monosaccharides.     

A fluorescent probe for zinc ions based on N-methyltetraphenylporphine with high selectivity

N-methyl-alpha,beta,gamma,delta-tetraphenylporphine (NMTPPH) has been used to detect trace amount of zinc ions in ethanol-water solution by fluorescence spectroscopy. The fluorescent probe undergoes a fluorescent emission intensity enhancement upon binding to zinc ions in EtOH/H(2)O (1:1, v/v) solution. The fluorescence enhancement of NMTPPH is attributed to the 1:1 complex formation between NMTPPH and Zn(II) which has been utilized as the basis for the selective detection of Zn(II). The linear response range covers a concentration range of Zn(II) from 5.0x10(-7) to 1.0x10(-5)mol/L and the detection limit is 1.5x10(-7)mol/L. The fluorescent probe exhibits high selectivity over other common metal ions except for Cu(II).