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Exploring the construction of an interface with bright emission, fabulous stability, and good function to develop high-performance electrochemiluminescence (ECL) biosensors for tumor biomarkers is in high demand but faces a huge challenge. Herein, we report an oriented attachment and in situ self-assembling strategy for one-step fabrication of CdTe QD-encapsulated Hf polymer membrane onto an ITO surface (Hf-CP/CdTe QDs/APS/ITO). Hf-CP/CdTe QDs/APS/ITO is fascinating with excellent stability, high ECL emission, and specific adsorption toward ssDNA against dsDNA and mononucleotides (mNs). These interesting properties make it an ideal interface to rationally develop an immobilization-free ECL biosensor for cancer antigen 125 (CA125), used as a proof-of-concept analyte, based on target-aptamer recognition-promoted exonuclease III (Exo III)-assisted digestion. The recognition of ON by CA125 leads to the formation of CA125@ON, which hybridizes with Fc-ssDNA to switch Exo III-assisted digestion, decreasing the amount of Fc groups anchored onto the electrode's surface and blocking electron transfer. As compared to the case where CA125 was absent, significant ECL emission recovery is determined and relies on CA125 concentration. Thus, highly sensitive analysis of CA125 against other biomarkers was achieved with a limit of detection down to 2.57 pg/mL. We envision this work will provide a new path to develop ECL biosensors with excellent properties, which shows great potential for early and accurate diagnosis of cancer. [ABSTRACT FROM AUTHOR]

The photoelectrochemical (PEC) detection method, as a potential strategy for Cu2+ detection, has garnered widespread attention. In this paper, we present a PEC sensing platform using upconversion nanoparticles (UCNPs) as the conversion light source and CdTe quantum dots (QDs) as the photoactive material for the detection of Cu2+ in solution. When irradiated with a 980 nm light source, the UCNPs will absorb the 980 nm laser and emit fluorescence around 550 nm, which is then absorbed by the CdTe QDs. This absorption leads to electron-hole separation, with electrons transferring through the multi-walled carbon nanotubes (MWCNTs) into the indium tin oxide (ITO) electrode. In the presence of Cu2+, the Cu2+ will be reduced to Cu+ by the electrons generated by the CdTe QDs, thereby hindering the transfer of electrons from the CdTe QDs to the ITO electrode and resulting in a reduction in current. The photocurrent continuously decreases with increasing Cu2+ concentration and shows a good linear relationship with Cu2+ concentration in the range of 1 µM to 25 µM. The lowest detection limit is 0.5 µM. [ABSTRACT FROM AUTHOR]

The photoelectrochemical (PEC) detection method, as a potential strategy for Cu2+ detection, has garnered widespread attention. In this paper, we present a PEC sensing platform using upconversion nanoparticles (UCNPs) as the conversion light source and CdTe quantum dots (QDs) as the photoactive material for the detection of Cu2+ in solution. When irradiated with a 980 nm light source, the UCNPs will absorb the 980 nm laser and emit fluorescence around 550 nm, which is then absorbed by the CdTe QDs. This absorption leads to electron-hole separation, with electrons transferring through the multi-walled carbon nanotubes (MWCNTs) into the indium tin oxide (ITO) electrode. In the presence of Cu2+, the Cu2+ will be reduced to Cu+ by the electrons generated by the CdTe QDs, thereby hindering the transfer of electrons from the CdTe QDs to the ITO electrode and resulting in a reduction in current. The photocurrent continuously decreases with increasing Cu2+ concentration and shows a good linear relationship with Cu2+ concentration in the range of 1 µM to 25 µM. The lowest detection limit is 0.5 µM. [ABSTRACT FROM AUTHOR]

Abstract Heavy metal ions bioaccumulation can cause severe damage to environment and human health. Hence, the development of an effective detection assay of trace amounts of these ions is of great importance. Here, CdTe quantum dots (QDs) capped with mercaptosuccinic acid (MSA) ligands have been synthesized in aqueous solution with significant stability and good fluorescence properties. Photophysical characterization was performed using FTIR, XRD, HRTEM and UV–Vis. Absorption, PL and PLRT techniques, seeking their subsequent application as fluorescent probes for metal cations. CdTe-MSA QDs showed selective sensitivity toward Hg2+ ions by monitoring quantitative fluorescence quenching with increasing analyte content. Under optimal conditions, the linear range for the detection was 0.2–6 μM with a detection limit of 0.05 μM. According to the Stern–Volmer model, it can be inferred that a static quenching mechanism via Hg2+ selective binding to MSA carboxylate groups is operating with electron transfer process. Excess of mercuric ions further decreased and red shifted the fluorescence possibly due to competitive cation exchanges. To further explain the corresponding ligation mechanisms, adsorption behavior study was conducted via several isotherms as well as statistical physics models. The pseudo-first-order model can describe the adsorption kinetics of Hg2+ on CdTe-MSA QDs more accurately and the experimental data fitted well the Langmuir isotherm model of monolayer adsorption on homogeneous surface. Furthermore, this spontaneous process conforms to the Hill model as a physisorption with an adsorption energy of 32 kJ.mol−1 associated with the electrostatic interactions and hydrogen bonding. The developed system was assayed in the Hg2+ trace amount detection in real tap water and showed satisfactory accuracy performance meeting analytical requirements. The relevant results demonstrated that CdTe-MSA QDs could be deployed as promising Hg2+ fluorescent chemosensing system with high sensitivity and selectivity over wide linear detection range that have great potential for real water samples analysis.

Heavy metal ions bioaccumulation can cause severe damage to environment and human health. Hence, the development of an effective detection assay of trace amounts of these ions is of great importance. Here, CdTe quantum dots (QDs) capped with mercaptosuccinic acid (MSA) ligands have been synthesized in aqueous solution with significant stability and good fluorescence properties. Photophysical characterization was performed using FTIR, XRD, HRTEM and UV–Vis. Absorption, PL and PLRT techniques, seeking their subsequent application as fluorescent probes for metal cations. CdTe-MSA QDs showed selective sensitivity toward Hg2+ ions by monitoring quantitative fluorescence quenching with increasing analyte content. Under optimal conditions, the linear range for the detection was 0.2–6 μM with a detection limit of 0.05 μM. According to the Stern–Volmer model, it can be inferred that a static quenching mechanism via Hg2+ selective binding to MSA carboxylate groups is operating with electron transfer process. Excess of mercuric ions further decreased and red shifted the fluorescence possibly due to competitive cation exchanges. To further explain the corresponding ligation mechanisms, adsorption behavior study was conducted via several isotherms as well as statistical physics models. The pseudo-first-order model can describe the adsorption kinetics of Hg2+ on CdTe-MSA QDs more accurately and the experimental data fitted well the Langmuir isotherm model of monolayer adsorption on homogeneous surface. Furthermore, this spontaneous process conforms to the Hill model as a physisorption with an adsorption energy of 32 kJ.mol−1 associated with the electrostatic interactions and hydrogen bonding. The developed system was assayed in the Hg2+ trace amount detection in real tap water and showed satisfactory accuracy performance meeting analytical requirements. The relevant results demonstrated that CdTe-MSA QDs could be deployed as promising Hg2+ fluorescent chemosensing system with high sensitivity and selectivity over wide linear detection range that have great potential for real water samples analysis. [ABSTRACT FROM AUTHOR]

The extensive product and application of cadmium-quantum dots (Cd-QDs), one kind of semiconductor nanomaterials, lead to prolonged exposure to the environment. Cd-QDs have shown good properties in biomedical and imaging-related fields; the safety of Cd-QDs limits the application of these materials and technologies, however. The systematic distribution of CdTe QDs in organisms has been ascertained in previous studies. Nevertheless, it is relatively less reported about the toxicity of CdTe QDs to immune macromolecules and organs. Based on this, immunocytes (including lymphocyte subsets-CD4+ T and CD8+ T cells, splenocytes) and selenoprotein P (SelP) were chosen as targets for CdTe QDs immunotoxicity studies. Results indicate that CdTe QDs induced cytotoxicity to CD4+ T cells, CD8+ T cells and splenocytes by reducing cell viability and causing apoptosis as CdTe QDs and Cd2+ enter cells. At the molecular level, the direct interaction between CdTe QDs and SelP is proved by multispectral measurements, which demonstrated the alteration of protein structure. The combined results show that CdTe QDs induced adverse effects on the immune system at the cellular and molecular levels. This research contributes to a better understanding of CdTe QDs cause harmful damage to the immune system and provides new strategies for the inhibition and treatment of health damages caused by CdTe QDs. Graphical Abstract [ABSTRACT FROM AUTHOR]

In this paper, the complexation characteristics of CdTe QDs using butyrylcholine and thiocholine as capping agents were studied with density functional theory (DFT). The stable complexation configurations were first optimized, based on which the relevant adsorption energies, charge densities, UV-Vis absorption spectr and frontier molecular orbital were calculated. It is found that the adsorption energy of butyrylcholine on CdTe QDs is very small, and the electron interaction between butyrylcholine and CdTe QDs is quite weak, which therefore can be attributed as to physical adsorption. In the meantime, the absorption intensity of ultraviolet and visible light is weak as well. In contrast, the electron interaction between thiocholine and CdTe QDs is strong, which is chemical adsorption, and the absorption intensity of ultraviolet and visible light is strong. The research results provide theoretical support for the detection of butyrylcholinesterase using CdTe QDs in the experiment. [ABSTRACT FROM AUTHOR]

In this paper, the complexation characteristics of CdTe QDs using butyrylcholine and thiocholine as capping agents were studied with density functional theory (DFT). The stable complexation configurations were first optimized, based on which the relevant adsorption energies, charge densities, UV-Vis absorption spectra and frontier molecular orbital were calculated. It is found that the adsorption energy of butyrylcholine on CdTe QDs is very small, and the electron interaction between butyrylcholine and CdTe QDs is quite weak, which therefore can be attributed to physical adsorption. In the meantime, the absorption intensity of ultraviolet and visible light is weak as well. In contrast, the electron interaction between thiocholine and CdTe QDs is strong, which is chemical adsorption, and the absorption intensity of ultraviolet and visible light is strong. The research results provide theoretical support for the detection of butyrylcholinesterase using CdTe QDs in the experiment. [ABSTRACT FROM AUTHOR]

Abstract In this work, a sonication induced modified wet chemical approach is adopted to synthesize highly luminescent and water soluble cadmium telluride (CdTe) quantum dots (QDs). The morphology, size, crystal structural, and optical properties of CdTe QDs are investigated for different refluxing time (1–4 h). The refluxing time-dependent optical constants viz. band gap energy and Urbach energy of the QDs are estimated from UV–Visible absorption spectra. The optical band gap energy decreased from ~ 2.12 to 1.92 eV and the Urbach energy increased from ~ 361 to 487 meV, with the increase in refluxing time. CdTe QDs are found to be uniform in size. The average size of the QDs estimated from the High Resolution Transmission Electron Microscope image analysis is about 5.8 and 8.2 nm for refluxing times 1 and 4 h, respectively. The growth mechanism of the QDs as a function of refluxing time has also been discussed. The fluorescence spectra of the QDs, revealed emission peaks having wavelength from ~ 534 to 585 nm, under the excitation wavelength of 320 nm. The fluorescence emission peaks showed a bathochromic shift with increasing refluxing time. CdTe QDs also exhibit excitation-dependent fluorescence behaviour. Two crystalline phases of the CdTe QDs, namely hexagonal and cubic are confirmed from the High Resolution Transmission Electron Microscope images and Selected Area Electron Diffraction patterns analysis. The phase transformation from hexagonal to cubic is successfully achieved by tuning the refluxing time from 1 to 4 h.

Cadmium tellurium quantum dots (CdTe QDs) as one of the most widely used QDs have been reported the toxicity and biosafety in recent years, little work has been done to reduce their toxicity however. Based on the mechanisms of toxicity of CdTe QDs on liver target organs such as oxidative stress and apoptosis previously reported by other researchers, we investigated the mechanism of action of trace element selenium (Se) to mitigate the hepatotoxicity of CdTe QDs. The experimental results showed that Se-Met at 40–140 μg L−1 could enhance the function of intracellular antioxidant defense system and the molecular structure of related antioxidant enzymes by reduce the production of ROS by 45%, protecting the activity of antioxidants and up-regulating the expression of selenoproteins with antioxidant functions, Gpx1 increase 225% and Gpx4 upregulated 47%. In addition, Se-Met could alleviate CdTe QDs-induced apoptosis by regulating two apoptosis-inducing factors, as intracellular caspase 3/9 expression levels were reduced by 70% and 87%, decreased Ca2+ concentration, and increased mitochondrial membrane potential measurements. Overall, this study indicates that Se-Met has a significant protective effect on the hepatotoxicity of CdTe QDs. Se-Met can be applied to the preparation of CdTe QDs to inhibit its toxicity and break the application limitation.

Background and purpose: Quantum dots (QDs) are semiconductor nanocrystals that are widely used in biology due to their good optical properties. QDs, especially cadmium-based QDs, play an important role in the diagnosis and treatment of cancer due to their intrinsic fluorescence. . The aim of the present study was the evaluation of the cellular uptake mechanisms of CdTe QDs in ovarian cancer cell lines. Experimental approach: In this study, we used CdTe QDs coated with thioglycolic acid. The ovarian cancer cell lines SKOV3 and OVCAR3 were treated with different concentrations of QDs, triamterene, chlorpromazine, and nystatin, and cell viability was evaluated through the MTT test. To find the way of cellular uptake of CdTe QDs, we used the MTT test and interfering compounds in endocytic pathways. Intrinsic fluorescence and cellular internalization of CdTe QDs were assessed using flow cytometry and fluorescence microscopy imaging. Findings / Results: The viability of CdTe QDs-treated cells dose-dependently decreased in comparison to untreated cells. To evaluate the cellular uptake pathways of CdTe QDs, in most cases, a significant difference was observed when the cells were pretreated with nystatin. The results of flow cytometry showed the cellular uptake of CdTe QDs was dose- and time-dependent. Conclusion and implications: Nystatin had a measurable effect on the cellular uptake of CdTe QDs. This finding suggests that caveola-mediated endocytosis has a large portion on the internalization of CdTe QDs. According to the results of this study, CdTe QDs may have potential applications in cancer research and diagnosis.

Thanks to high absorption, narrow emission bandwidth and high photoluminescence quantum yield (PLQY), cadmium telluride (CdTe) quantum dots (QDs) have demonstrated excellent performance for photoelectronic devices. However, a large number of surface defects cause low device performance and must be deactivated. This paper reports a facile post-treatment method to passivate the surface defects of CdTe QDs by ZnCl2 aqueous solution. Consequently, the water phase of as-prepared CdTe QDs demonstrated improved PLQY. Furthermore, we fabricated a warm white light emitting diode (WLED) based on red-emitting CdTe QDs and yellow-emitting YAG:Ce3+ phosphors, which exhibited excellent performance, including a high color rendering index (Ra) of 90.8, low color temperature (Tc) of 5064 K and relatively high luminous efficiency (LE) of 70.56 lm W−1. These results suggest that ZnCl2 may passivate the defects of CdTe QDs well and sheds new light on high-quality fluorescent materials for WLEDs. [ABSTRACT FROM AUTHOR]

Chloramphenicol (CAP) is widely used in the food industry and animal husbandry due to its effective antibiotic effect active against gram-positive and gram-negative microorganisms. However, research shows that it can cause serious adverse reactions and side effects in the human body. In order to effectively monitor the residues of CAP, a novel and simple photoelectrochemical (PEC) sensor for sensitive detection of CAP is fabricated based on M-TiO2-CdTe QDs/CdS QDs composite. The results show that the prepared M-TiO2 not only retains the original morphology and structure of MIL-125(Ti), but also exhibits more abundant pore structure and good photoelectrochemical properties. Compared with M-TiO2, the as-prepared M-TiO2-CdTe QDs/CdS QDs composite exhibits excellent PEC performances including about ninefold enhancement of photocurrent intensity, which is ascribed to the large surface of M-TiO2 and the introduction of CdTe QDs and CdS QDs. Based on the selective inhibitory effect of CAP in the photocurrent intensity of the M-TiO2-CdTe QDs/CdS QDs PEC system, a novel PEC sensor for CAP concentration determination is constructed. The designed PEC sensor demonstrates a linear range from 1 to 140 nmol L−1 with a detection limit of 0.14 nmol L−1 (S/N = 3). Moreover, the method is applied to real milk samples to quantify the CAP residues with spiked recoveries in the range of 96.3–106%, and the possible detection mechanism of the M-TiO2-CdTe QDs/CdS QDs PEC system is also discussed. [ABSTRACT FROM AUTHOR]

In this paper, density functional theory (DFT) and time-dependent density functional theory (TDDFT) are used to study the complexation characteristics CdTe QDs with four different capping agents, i.e. 3-mercaptopropionic acid (MPA), reduced glutathione (GSH), 1-thioglycerol (TG) and 2-mercaptoethanesulfonate (MES). The properties of these complexes are analyzed by the complexation free energies, bond lengths, LOL, ADCH charges, frontier molecular orbitals and the UV–Vis absorption spectra. The results indicate that the four capping agents could form stable complexes with CdTe QDs. Whether the four capping agents interact with (CdTe)6 or (CdTe)9, MES has the strongest complexation ability with CdTe QDs and the MES-complexes are the most stable. For (CdTe)6, A2-MES is the most stable configuration. The complexation free energy and bond length of A2-MES are − 74.50 kcal/mol and 2.461 Å, respectively. When (CdTe)9 as substrate, A4-MES is the most stable configuration and corresponding complexation free energy is − 100.97 kcal/mol, which is followed by A4-MPA (− 57.75 kcal/mol) and A3-TG (− 60.20 kcal/mol), while A4-GSH (− 44.47 kcal/mol) is the weakest. Moreover, the electron amount transferred from MES to CdTe QDs is the most, and the ADCH charge value is 1.47 e. The absorption intensity of UV–visible light after complexation is also the largest. This is consistent with the result of the complexation free energy. Thus, it can be seen that the complexation abilities of four capping agents are in order of MES > MPA≈TG > GSH. [ABSTRACT FROM AUTHOR]

Based on the fluorescence quenching effect of citric yellow on GSH-CdTe QDs (GSH: glutathione), the concentration of citric yellow (LY) in soft drink was detected by quantum dot fluorescence quenching method, and the reaction mechanism was analysed. The results showed that: LY could be measured in the range of 1.1–46.2 μg∙mL−1 with a detection limit of 6.7 ng∙mL−1. Combined with the influence of temperature change on fluorescence quenching constant and UV-vis absorption spectrum, it can be seen that this process is a static quenching process. The influence of common interfering species on the LY detection was studied, the results showed that the probe is highly selective and sensitive for the detection of LY. Finally, the optical probe was successfully used for the determination of LY in three kinds of soft drink. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis method of MPA-CdTe QDs was improved to obtain an ideal quantum yield. • Fluorescence sensor of CdTe QDs was firstly used to detect aklomide and nitromide. • The binding of aklomide/nitromide to CdTe QDs was firstly investigated. • The methods were used for the determination in poultry samples. Based on the fluorescence sensor of 3-Mercaptopropionic acid (MPA) capped CdTe quantum dots (QDs), two novel detection methods for aklomide and nitromide were developed. The MPA-CdTe QDs were synthesized and characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), ultraviolet visible (UV–vis) and fluorescence (FL). The quenchings were all static. The binding constants (K a) at different temperatures were obtained. Electrostatic forces were the main forces for the two bindings. For the detection of aklomide and nitromide, under the optimal conditions, the effects of some metal ions, glucose, bovine serum albumin (BSA) and congeneric drug on the determination were explored. The standard equations were established and the limits of detection (LOD) were 0.0215 and 0.0388 μg mL−1 (3 S 0 / S), repectively. The methods were applied to analyse the samples of chicken and duck, the recoveries were 99.41 % – 101.24 % with RSDs of 0.29 % – 1.19 % (n = 5). [ABSTRACT FROM AUTHOR]

Nano-bio interface is significant concern in nanomedicine. When nanoparticles (NPs) come into contact with cells, they form complexes with proteins known as protein corona (PC). Cadmium telluride quantum dots (CdTe QDs) have been applied as bioimaging probes and for macrophage theragnostic. However, the impact of protein corona on the behavior of CdTe QDs is not well understood. Macrophages play a crucial role in defending against NPs. In this study, RAW264.7 cells were used to investigated the inflammatory response in macrophages when exposed to CdTe QDs before and after PC formation in fetal bovine serum. The results indicated that protein corona polarized more macrophages towards M1 phenotype. Transcriptomics analysis revealed that PC-CdTe QDs altered a greater number of differentially expressed genes (DEGs) compared to CdTe QDs (177 and 398) at 1.0 μM in macrophages. The DEGs affected by PC-CdTe QDs contained several personalized inflammatory cytokines. The enriched pathways after PC formation included Cytokine-cytokine receptor interaction, NOD-like receptor signaling pathway, and TNF signaling pathway, etc. Furthermore, PC specifically exacerbated the overexpression of CCL2 and IL-1β proteins. Importantly, PC altered the mechanism of CdTe QD-induced pyroptosis, shifting it from activating NLRC4 to both NLRP1 and NLRP3 inflammasomes, and from cleaving GSDMD and GSDMB to GSDMB alone. Overall, protein corona exacerbated the inflammatory response induced by CdTe QDs in macrophages. This study provides valuable insight into the pro-inflammatory effect of protein corona on CdTe QDs, with implications for their use in bioimaging or macrophage theragnostic by either exploiting or eliminating this biological interface effect., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A novel PS@CdTe multilayers fluorescence microsphere was successfully synthesized by the electrostatic layer-by-layer (LBL) self-assembly technique. The structure, the process of self-assembly and the fluorescence performance were confirmed by high-resolution transmission electron microscope (HRTEM), Zeta potentiometric analyzer and fluorescence spectrophotometer, respectively. The results manifest that when the pH of buffer solution is 7.8, the negative charge on the surface of CdTe quantum dots (QDs) is the largest, which is beneficial to the synthesis of electrostatic self-assembled microspheres. The fluorescence properties of PS@CdTe microspheres increased gradually with the number of layers coated increased, and the optimum number of coating layers is three. Under this condition, the PS@CdTe microspheres exhibited a great increase of 25-fold in fluorescence performance compared to the equal quantity of pure CdTe QDs. Moreover, the emission spectra of PS@CdTe microspheres recorded under the excitation of 410 nm, and shows a strong emission peak located at 524 nm. This kind of core-shell microspheres has a great potential to be used in the field of optoelectronics. The fabrication process of PS@CdTe multilayers core-shell microspheres using electrostatic LBL self-assembly method. Image 1 • Multilayer CdTe QDs are adsorbed on the surface of PS microspheres. • The PS@CdTe microspheres exhibited an excellent fluorescence performance. • The fluorescence performance of product slightly decreased by 8% under high temperature. [ABSTRACT FROM AUTHOR]

Simple, sensitive, and cost-effective detection of biomolecules is important to clinical analysis and treatment. Herein, a novel fluorescence turn-off method for the homogeneous detection of DNA and proteins was developed using selective recognition reaction and silver ion-mediated conformational switch. In this work, we discovered the new phenomenon that cadmium telluride (CdTe) quantum dots (QDs) could selectively differentiate silver ions (Ag+) from the cytosine (C)-Ag+-cytosine (C-Ag+-C) hairpin structure, owing to the ability of Ag+ to quench CdTe QDs which the C-Ag+-C complex didn't possess. With this method, the C-Ag+-C hairpin probe formed, followed by the reaction with the target DNA, thus the C-Ag+-C was opened and free Ag+ were released. This initiated the selective recognition reaction with CdTe QDs, leading to the decrease in the CdTe QDs fluorescence intensity. Therefore, the DNA concentration could be quantitatively measured by indirectly monitoring the fluorescence signal of CdTe QDs. Furthermore, the application of this sensor was extended to the detection of prostate-specific antigen (PSA) by employing its aptamer as the recognize elements, with the similar strategy used for the target DNA assay. Under the optimized conditions, this strategy achieved good analytical performance for both DNA assay with a limit of detection of 0.12 nM and linear dynamic range of 5–100 nM, and PSA assay with a limit of detection of 0.01 ng/mL and the linear dynamic range of 0.1–2.5 ng/mL. This new fluorescence method is simple in design and operation, with no need for oligonucleotide labeling and separation, and it has great potential to be applied in clinical diagnosis. A novel label-free, highly sensitive and homogeneous turn-off mode strategy for the fluorescence detection of DNA and protein using the selective recognition reaction of CdTe QDs and silver ion-mediated conformational switch was developed. Image 1 • A simple homogeneous fluorescence bioassay was developed via selective recognition and Ag+- mediated conformational switch. • The developed sensor presents a high sensitivity and selectivity for DNA and protein detection. • The biosensor was successfully applied to PSA detection in human serum samples. [ABSTRACT FROM AUTHOR]

Nanotechnology has achieved more commercial attention over recent years, and its application has increased concerns about its discharge in the environment. In this study, we have chosen human hepatic carcinoma (HuH-7) cells because liver tissue has played an important role in human metabolism. Therefore, the objective of this study was to determine DNA damaging and apoptotic potential of cadmium telluride quantum dots (CdTe QDs; average particle size (APS) 10 nm, 1–25 µg/ml) on HuH-7 cells and the basic molecular mechanism of its cellular toxicity. Cytotoxicity of different concentrations of CdTe QDs on HuH-7 cells was determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and lactate dehydrogenase (LDH) tests. Moreover, reactive oxygen species (ROS) generation, mitochondrial membrane potential, DNA damage, and Hoechst 33342 fluorescent staining morphological analysis of necrotic/apoptotic cells were detected; cellular impairment in mitochondria and DNA was confirmed by JC-1 and comet assay, respectively. A dose- and time-dependent cytotoxicity effect of CdTe QDs exposure was observed HuH-7 cells; the significant (p < 0.05) cytotoxicity was found at 25 μg/ml of CdTe QDs exposure. The percentage of cytotoxicity of CdTe QDs (25 μg/ml) in HuH-7 cells reached 62% in 48 h. CdTe QDs elicited intracellular ROS generation and mitochondrial depolarization, and DNA integrity cells collectively advocated the apoptotic cell death at higher concentration. DNA damage was observed in cells due to CdTe QDs exposure, which was mediated by oxidative stress. This study exploring the effects of CdTe QDs in HuH-7 cells has provided valuable insights into the mechanism of toxicity induced by CdTe QDs. [ABSTRACT FROM AUTHOR]

We report the interaction between different sizes of CdTe quantum dots (CdTe QDs) and copper (II) ion (Cu2+) via experimental and theoretical aspects. Different sizes of CdTe QDs are synthesized and size effects on the selectivity in the detection of Cu2+ ions are studied. Experimental results indicate that with the size of CdTe QDs from 1.8 nm to 2.7 nm and to 3.2 nm increases, the linear range gets wider. For the smallest size of QD (QD 524 , 1.8 nm), the linear range is 1.0–5.0 × 10−5 M with a limited detection of 2.8 × 10−5 M. The Stern–Volmer plots at different temperatures demonstrate that the fluorescence of CdTe QDs is quenched by Cu2+ ion through a dynamic quenching mechanism, and the physiological mechanism is analyzed. Electrons are transferred from CdTe QDs to Cu2+ ion, and Cu2+ ion acquire electrons and are reduced to Cu+ ion, leading to fluorescence quenching. Meanwhile, with the increase in the number of transferred electrons, the phenomenon of fluorescence quenching is more obvious. In order to validate the process of electron transfer, the amount of transferred charge between Cu2+ and CdTe QDs are calculated by using first principles density functional theory (DFT). Calculation results show that the smaller the QDs are, the more electrons they transfer. The linear range of the smaller size QDs (QD 524) is the narrowest, indicating fluorescence quenching is indeed the most obvious of all three sizes. • Size effects of CdTe QDs on the sensitivity and selectivity in the fluorometric detection of Cu2+ ion are studied. • The process of electron transfer between CdTe QDs and Cu2+ ion is validated by first-principles calculation. • The smaller sized CdTe QDs owns the larger number of transferred electrons, resulting in lower PL efficiency. [ABSTRACT FROM AUTHOR]

In this study, we developed a novel simple fluorescence resonance‐energy transfer (FRET) system between two‐color CdTe quantum dots (QDs) assisted by cetyltrimethylammonium bromide (CTAB). Mercaptopropionic (MPA)‐capped CdTe QDs serving as both donors and acceptors were successfully synthesized by changing the refluxing time in aqueous solution. CTAB micelles formed in water and minimized the distance between the donors and acceptors significantly by electrostatic interactions, improving FRET efficiency. Several factors that affected the fluorescence spectra of the FRET system were investigated. The prepared FRET system was feasible as an effective fluorescent probe to detect Hg(II) in aqueous solution. At pH 7.0, a linear relationship between the quenched fluorescence intensity of orange‐emitting acceptors (QDs(A)) and Hg(II) concentration was acquired in the range 5–250 nmol/L with a detection limit of 1.95 nmol/L. The developed method showed excellent analytical performance for Hg(II) with high sensitivity and acceptable selectivity, reproducibility and stability. This finding indicated that the method has a promising potential application for environmental monitoring. This study demonstrated the great promise of QDs for expedient, low‐cost and high‐sensitivity detection of Hg(II). [ABSTRACT FROM AUTHOR]

Abstract Luminescent, water soluble, CdTe colloidal QDs were synthesized by simple wet chemical method. The prepared CdTe QD samples were showing wide range of color tunability from green to red when irradiated with UV light. The quantum confinement effect of the synthesized QDs was confirmed using UV–vis absorption and fluorescence spectroscopy. The spherical morphology of the synthesized QDs was confirmed using transmission electron microscopy (TEM). The X-ray diffraction (XRD) analysis indicates that the QDs were having cubic structure. Analysis of the third order nonlinear property using Z-scan technique indicates that the QDs were having two photon absorption properties. Unlike the previous reported results, the variations in the third order nonlinear susceptibility (χ 3) was found to be in correlation with emission intensity. The value of imaginary part of nonlinear χ 3 and refractive index was found to be of the order of 10−11 and 10-7esu respectively. Imaginary part of χ 3 is found to be Gaussian dependent function of reaction time, which provides a possible way of tuning of imaginary part of third order susceptibility. The figure of merit (n 2 /β) of the synthesized QDs was found to be greater than that for the bulk material. Thus these QDs possess good nonlinear optical characteristics which enable them as a potential candidate for the optical limiting application. [ABSTRACT FROM AUTHOR]

Abstract Ag+ as one of the most commonly seen toxic heavy metal ions is involved in numerous vital biological processes, which would cause fatal damages and environmental contamination when Ag+ is excessive. In the present work, CdTe quantum dots (QDs) with green, orange, and red emission capped by mercaptoacetic acid (TGA) were synthesized at one time by controlling the synthesis time and utilized for Ag+ detection. Both fluorescence spectral red-shift and intensity decrease could be used for Ag+ discrimination. Fluorescence lifetime, Zeta potential, and XRD, etc. were carried out to analyze the detection mechanism. Results displayed that surface passivation and electron transfer due to binding effects of Ag+ to Te atom on traps of QDs could be relied on to explain the sensing mechanism. Additionally, in accordance with PCA analysis, Ag+ could be also be successfully differentiated from Hg2+ and the other metal ions. Importantly, a home-made portable device based on a 32 bit embed Micro Control Unit (MCU) system was first proposed for Ag+ detection. The power supply system adopt the mini-sized lithium cell instead of the power supply system, which ensure its practical applicability. The relative position of light source and detector is set at 90° to minimize the interference. According to the detection results, the linear detection range using the device was from 5 nM to 200 nM (with a larger coefficient of determination, R2), and the detection limit was calculated to be about 5 nM, which indicated that this proposed method and device could fulfil the practical application requirements. Graphical abstract Passivation and binding effects of Ag+ on traps of QDs could be relied on to explain the fluorescence response characteristics. Both of fluorescence intensity quenching and spectral red-shift could be used to realize linearly Ag+ detection. A portable sensing device based on 32 bit MCU was successfully applied for on-field Ag+ detection. fx1 Highlights • A portable sensing device with mercaptoacetic acid capped QDs as fluorescence probe was developed for Ag+ detection. • Electron transfer process occurred in Ag+ detection process was investigated. [ABSTRACT FROM AUTHOR]

Cadmium tellurium quantum dots (CdTe QDs) as one of the most widely used QDs have been reported the toxicity and biosafety in recent years, little work has been done to reduce their toxicity however. Based on the mechanisms of toxicity of CdTe QDs on liver target organs such as oxidative stress and apoptosis previously reported by other researchers, we investigated the mechanism of action of trace element selenium (Se) to mitigate the hepatotoxicity of CdTe QDs. The experimental results showed that Se-Met at 40–140 μg L−1 could enhance the function of intracellular antioxidant defense system and the molecular structure of related antioxidant enzymes by reduce the production of ROS by 45%, protecting the activity of antioxidants and up-regulating the expression of selenoproteins with antioxidant functions, Gpx1 increase 225% and Gpx4 upregulated 47%. In addition, Se-Met could alleviate CdTe QDs-induced apoptosis by regulating two apoptosis-inducing factors, as intracellular caspase 3/9 expression levels were reduced by 70% and 87%, decreased Ca2+ concentration, and increased mitochondrial membrane potential measurements. Overall, this study indicates that Se-Met has a significant protective effect on the hepatotoxicity of CdTe QDs. Se-Met can be applied to the preparation of CdTe QDs to inhibit its toxicity and break the application limitation. [Display omitted] ● Combining cellular and molecular levels to study the role and regulation mechanism of Se-Met in adverse effects induced by CdTe QDs. ● Se-Met maintains redox balance and mitochondrial function by protecting the structural changes of SOD/CAT and enhancing the antioxidant function of selenoproteins, reduces the level of apoptosis induced by CdTe QDs, and attenuates the toxicity of CdTe QDs on hepatocytes. [ABSTRACT FROM AUTHOR]

Abstract A novel ratiometric electrochemiluminescent (ECL) biosensor was designed for the detection of concanavalin A (Con A) based on two ECL emitters competing for the dissolved oxygen (O 2). In this strategy, CdTe quantum dots (QDs) were used as the cathodic emitter and N-(aminobutyl)-N-(ethylisoluminol) (ABEI) was used as the anodic emitter. With the presence of dissolved O 2 utilized as co-reactant, CdTe QDs showed an ECL emission at − 1.7 V, and ABEI showed an emission at + 0.6 V. Phenoxy-derivatized dextran (Dexp), as a recognition element, was immobilized by graphene oxide functionalized CdTe QDs (G-CdTe QDs) to recognize Con A, and further combine with Dexp, gold and platinum nanoparticles decorated ABEI (Dexp-Au-Pt-ABEI) to form a sandwich structure. With the increasing concentration of analyte Con A, the ECL signal of cathodic CdTe QDs decreased and the anodic response of ABEI increased, thus achieving a ratiometry detection of Con A with a wide linear range from 1.0 × 10−4 ng/mL to 10 ng/mL. The detection limit was low to 3.0 × 10−5 ng/mL. This proposed ratiometric ECL biosensor not only conquered the false errors caused by external interferences, but excluded the disability caused by exogenous co-reactant via the application of common dissolved O 2. It also exhibited an excellent stability, selectivity and reproducibility. Highlights • The ratiometric biosensing for Con A detection was the first time. • Two emitters CdTe QDs and ABEI competed for dissolved oxygen (O 2) as co-reactant to form the ratiometric ECL biosensor. • This biosensor not only conquered the false errors, but excluded the disability caused by exogenous co-reactant. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) have been proven to possess intrinsic peroxidase-like activity. However, by far, most of POMs with intrinsic peroxidase-like activity are stable at acid aqueous. Herein, we firstly utilized Na 10 [α-SiW 9 O 34 ] with the peroxidase-like property in basic pH condition to build a CdTe quantum dots (QDs)-based fluorometric method for detection of hydrogen peroxide. In the CdTe QDs stable pH value, Na 10 [α-SiW 9 O 34 ] can catalyze the decomposition of H 2 O 2 into·OH radicals that could efficiently quench the fluorescence of CdTe QDs. The limit of detection in this system were 3.8 nmol/L. The RSD of detection were range from 0.88% to 2.78%. And the linear range of H 2 O 2 is from 7.8 × 10 −9 to 2.5 × 10 −7 mol/L. The rate of recovery of sample addition was between 93.99% and 110.02%. The results not only built a simple, sensitive and easy handing assay but also enlarge the POMs’ analytic application field. [ABSTRACT FROM AUTHOR]

Malachite green (MG) is an industrial dye, but has been once abused in aquaculture for disease treatment. Because MG and its metabolite, leucomalachite green (LMG), present great harm to human health, it is essential to rapidly and accurately detect MG and LMG residues in aquatic products. However, the simultaneous screening of MG and LMG is still a challenge to date. In this work, a dual-template molecularly imprinted polymer (MIP) coated CdTe QDs was developed and applied as a nano-probe to simultaneously detect MG and LMG in fish samples via normal and synchronous fluorescence quenching. The molar ratios of templates (MG and LMG) to monomer (APTES) and cross-linker (TEOS), and the amount of CdTe QDs in the probe preparation were optimized. A normal fluorescence emission at 600 nm could be linearly quenched by MG, while the synchronous fluorescence emission at the wavelength interval of 340 nm could be quenched by both LMG and MG. The detection limits of MG and LMG were 17 nmol L −1 and 28 nmol L −1 (3 σ , n = 9), respectively. Based on the equations of Stern-Volmer, MG and LMG could be simultaneously detected without any conversion treatment. The recoveries of MG and LMG in fish samples ranged from 92% to 107% and from 91% to 108%, respectively. The results demonstrated that the as-prepared dual-template CdTe@MIP could be used as a fluorescent probe to rapidly and simultaneously detect MG and LMG in fish samples. [ABSTRACT FROM AUTHOR]

In the present paper, we have reported room temperature synthesis of CTAB capped CdTe quantum dots in an aqueous medium for free radical scavenging assay choosing BHA as the reference free radical. The formation of CdTe QDs required relatively shorter reaction time with quantum yield up to 40 %. Their optical properties, surface morphology and structural characterizations were employed through UV-Visible absorption spectroscopy, Photoluminescence, FE-SEM, Powder-XRD, Raman spectroscopy and DSC-TGA techniques. These QDs showed maximum absorption at 551 nm and their shape was spherical with average particle size of about 3-4 nm as noted by surface morphology. The results showed that the synthesized CdTe QDs have an excellent antioxidant activity. This type of semiconductor quantum dot is a promising material for the upcoming generation in high speed optics and biomedical fields. [ABSTRACT FROM AUTHOR]

A novel fluorescent probe based on CdTe QDs coated with molecularly imprinted polymers (MIP) was prepared for the determination of leucomalachite green (LMG) with the method of synchronous fluorescence quenching. When the wavelength interval of excitation and emission positions (Δl) was set as 340 nm, the strongest synchronous fluorescence emission of MIP-coated QDs was achieved at 260 nm, enabling the maximum fluorescent quenching of LMG because of the inner filter effect. According to this principle, a synchronous fluorescence quenching method for the rapid detection of LMG in fish was developed. MIP-coated QDs were synthesized using acrylamide (AM) and ethylene glycol dimethacrylate (EGDMA) as functional monomers and cross-linker, respectively. MIP-coated QDs with an average diameter around 67 nm were obtained at the optimum conditions (the molar ratio of 1:8:20 of LMG, AM and EGDMA, 60 mL of acetonitrile, 28 h of polymerization time). The synchronous fluorescence of MIP-coated QDs was linearly quenched by LMG at concentrations from 0.1 to 20 μmol L −1 . Detection limit was 30 nmol L −1 (3 σ , n = 9) with spiked recoveries from 94.0% to 107.8% in fish samples. The results indicate that the method can be applied to the accurate and rapid detection of LMG residues in fish samples. [ABSTRACT FROM AUTHOR]

Highly sensitive nickel sensor based on repeatable fluorescence quenching-emerging mechanism was developed. Highly luminescent thioglycolic acid capped CdTe nanocrystals in aqueous solution were applied as the fluorescence probe. These nanocrystals represented a considerable photoluminescence quantum yield as high as 61%. The florescence was quenched by addition of Ni ions to the CdTe nanocrystals solution. Then it was recovered by injection of the proper amount of dimethylglyoxime as the releasing reagent. The relative fluorescence intensity ( F 0 / F ) was linearly proportional to the concentration of nickel ions in the range of 0.01–10 μM, with detection limit as low as 7 nM. Described method is able to selectively determine Ni 2+ without any tangible influence of some potentially interfering ions such as Ag + , Cu 2+ , Zn 2+ , Co 2+ and Hg 2+ . The developed technique was employed for determination of Ni 2+ in different environmental water samples, and the results were verified by inductively coupled plasma-optical emission spectrometry. [ABSTRACT FROM AUTHOR]

In this study, a novel three-dimensional (3D) origami ion imprinted polymers microfluidic paper-based chip device for specific, sensitive and multiplexed detection of Cu 2+ and Hg 2+ ions has been proposed. In this device, the surface of the paper was activated by grafting with CdTe QDs through amino processing and formation of Cu 2+ or Hg 2+ IIPs and CdTe QDs complex that led to fluorescence quenching of QDs because the photo luminescent energy of QDs could be delivered to the complex. This method can realize the liquid phase of QDs@IIPs being transferred to the solid glass fiber paper and improve the portability of the device. Moreover, this platform allows to simultaneous detection of Cu 2+ and Hg 2+ ions with good selectivity and sensitivity. The proposed method reveals that the copper ion imprinted fluorescent sensor demonstrated a good linearity from 0.11 to 58.0 μg/L with the detection limit of 0.035 μg/L and the mercury ion linear range is 0.26–34.0 μg/L with detection limit of 0.056 μg/L. Importantly, this device can provide quantitative information conveniently and show great potential to be further extended to the detection of other metal ions for environmental monitoring and food safety field. [ABSTRACT FROM AUTHOR]

In most applications of quantum dots (QDs) for surface-assisted laser desorption/ ionization mass spectrometry (SALDI-MS), one side of QDs is supported by a solid substrate (stainless - steel plate), whereas the other side is in contact with the target analytes. Therefore, the surface capping agent of QDs is a key parameter for laser desorption/ionization mass spectrometry (LDI-MS). Cadmium telluride quantum dots (CdTe QDs) modified with different capping agents are synthesized, characterized, and applied for surface tuning laser desorption/ ionization mass spectrometry ( STLDI-MS). Data shows that CdTe quantum dot modified cysteine (cys@CdTe QDs) has an absorption that matches with the wavelength of the N laser (337 nm). The synergistic effect of large surface area and absorption of the laser irradiation of cys@CdTe QDs enhances the LDI-MS process for small - molecule analysis, including α-, β-, and γ-cyclodextrin, gramicidin D, perylene, pyrene, and triphenylphosphine. Cys@CdTe QDs are also applied using Al foils as substrates. Aluminum foil combined with cys@CdTe QDs enhances the ionization efficiency and is cheap compared to traditional matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) with a stainless - steel plate. [ABSTRACT FROM AUTHOR]

In this work, we have designed a novel kind of nanohybrid with magnetic and photoluminescence (PL) property for trypsin detection. The modified magnetic Fe 3 O 4 nanoparticles (MNPs) with polydopamine (PDA) and human serum albumin (HSA) were prepared through a one step self-polymerization under mild condition. The polydopamine (PDA) coating on MNPs can improve the biocompatibility of the MNP-PDA-HAS composite due to its hydrophilicity and multifunctional groups. When MNP-PDA-HSA composite was added into the Anti-HSA modified CdTe QDs (anti-HSA-QDs), HSA on the MNP-PDA-HSA composite was captured by the site of anti-HSA-QDs to form MNP-PDA-HSA/anti-HSA-QDs nanohybrid. Therefore, the photoluminescence of QDs can be quenched by Fe 3 O 4 nanoparticles due to the electron transfer. In the presence of trypsin, the protein (anti-HSA) was digested by trypsin and QDs was separated from the nanohybrid surface. As a result, the photoluminescence intensity of QDs was recovered. The magnetic/luminescent bifunctional nanohybrid displayed excellent analytical performance for the detection of trypsin in the range of 0.5–30 μg/mL with a low detection limit of 0.25 μg/mL. [ABSTRACT FROM AUTHOR]

A novel one-step microwave irradiation method has been introduced to synthesize 3-mercaptopropionic acid capped CdTe QDs (Quantum dots). The synthesis process required no special conditions such as an inert nitrogen atmosphere but was carried out using TeO 2 (Tellurium oxide) as opposed to the Te powder, Na 2 TeO 3 or Al 2 TeO 3 usually used for the tellurium source. The characterization of the QDs revealed that they were 2–3 nm in size. The application of aqueous synthesis of capped CdTe QDs for latent fingerprinting was explored and fast turnaround times were achieved. [ABSTRACT FROM AUTHOR]

In this paper, a systematic investigation of the interaction of bovine serum albumin (BSA) with water-soluble CdTe quantum dots (QDs) of two different sizes capped with carboxylic thiols is presented based on steady-state and time-resolved fluorescence measurements. Efficient Förster resonance energy transfer (FRET) was observed to occur from BSA donor to CdTe acceptor as noted from reduction in the fluorescence of BSA and enhanced fluorescence from CdTe QDs. FRET parameters such as Förster distance, spectral overlap integral, FRET rate constant and efficiency were determined. The quenching of BSA fluorescence in aqueous solution observed in the presence of CdTe QDs infers that fluorescence resonance energy transfer is primarily responsible for the quenching phenomenon. Bimolecular quenching constant ( k q) determined at different temperatures and the time-resolved fluorescence data provide additional evidence for this. The binding stoichiometry and various thermodynamic parameters are evaluated by using the van 't Hoff equation. The analysis of the results suggests that the interaction between BSA and CdTe QDs is entropy driven and hydrophobic forces play a key role in the interaction. Binding of QDs significantly shortened the fluorescence lifetime of BSA which is one of the hallmarks of FRET. The effect of size of the QDs on the FRET parameters are discussed in the light of FRET parameters obtained. [ABSTRACT FROM AUTHOR]

In the present study, we developed a sensitive method based on fluorescence resonance energy transfer (FRET) for the determination of the BCR/ABL fusion gene, which is used as a biomarker to confirm the clinical diagnosis of both chronic myelogenous leukemia (CML) and acute lymphocytic leukemia (ALL). For this purpose, CdTe quantum dots (QDs) were conjugated to amino-modified 18-mer oligonucleotide ((N)DNA) to form the QDs-(N)DNA nanosensor. In the presence of methylene blue (MB) as an intercalator, the hybridization of QDs-(N)DNA with the target BCR/ABL fusion gene (complementary DNA), brings the MB (acceptor) at close proximity of the QDs (donor), leading to FRET upon photoexcitation of the QDs. The enhancement in the emission intensity of MB was used to follow up the hybridization, which was linearly proportional to concentration of the target complementary DNA in a range from 1.0 x 10-9 to 1.25 x 10-7 M. The detection limit of the proposed method was obtained to be 1.5 x 10-10 M. Finally, the feasibility and selectivity of the proposed nanosensor was evaluated by the analysis of derived nucleotides from both mismatched sequences and clinical samples of patients with leukemia as real samples. [ABSTRACT FROM AUTHOR]

Arsenic (As) is a hazardous and ubiquitous element; hence the quantitative detection of arsenic in various kinds of environmental sample is an important issue. Herein, we reported L-cysteine capped CdTe Quantum dot based optical sensor for the fluorometric detection of arsenic (III) in real water sample. The method is based on the fluorescence quenching of QDs with the addition of arsenic solution that caused the reduction in fluorescence intensity due to strong interaction between As and L-cysteine to form As(Cys). The calibration curve was linear over 2.0 nM-0.5 μM arsenic with limit of detection (LOD) of 2.0 nM, correlation coefficient (r) of 0.9698, and relative standard deviation (RSD %) of 5.2%. The Stern-Volmer constant for the quenching of CdTe QDs with As at optimized condition was evaluated to be 1.17 × 10 L mol s. The feasibility of the sensor has been analyzed by checking the inference of common metal ions available in the water such as K, Na, Mg, Ca, Ba, Cu, Ni, Zn, Al, Co, Cr, Fe and its higher oxidation state As. [ABSTRACT FROM AUTHOR]

Reactivation of telomerase, which is observed in more than 85% of all known human tumours, is considered a promising tumour marker for cancer diagnosis. With respect to the biomedical importance of telomerase, we have developed a simple strategy based on liposomal fluorescent signal amplification for highly sensitive optical detection of telomerase activity using liposome-encapsulated cadmium telluride quantum dots. In this strategy, telomerase extracted from A549 cells elongated the biotinylated telomerase substrate primer, which was then immobilized on streptavidine-coated microplate wells. After the hybridization of the telomerase-elongated product with biotinylated capture probe, streptavidin was added to the assembly. In the next step, biotinylated liposome was conjugated with capture probe through streptavidin. Finally, QD-encapsulated liposomes were disrupted by Triton X-100, and the fluorescence intensity of the released QDs was measured to detect telomerase activity. The results showed that the proposed nanobiosensor was able to detect telomerase activity from as few as 10 A549 cells without the enzymatic amplification of telomerase extension products. In short, this method is not only convenient and sensitive, but also has a simple operating protocol and a wide detection range (10-5000 cells). A linear range was observed between 50 and 800 cells with a correlation coefficient of 0.982 and regression equation of y = 0.0444 x + 17.137. The proposed method is economical, more user-friendly, without error-prone PCR, with a wide detection range and simple operating protocol without the requirement for sophisticated equipment. [ABSTRACT FROM AUTHOR]

β-adrenergic agonists (β-agonists) recognized as a growth promoter will reflect the health of human. Sensitive detection of β-agonists in foodstuff is valuable for the health of animals and human. A novel ultrasensitive competition-type electrochemiluminescent (ECL) immunosensor was developed for detecting brombuterol (Brom) based on CdTe Quantum dot (QDs) and polyamidoamine dendrimer (PAMAM, G2) modified graphene oxide (GO) (CdTe QDs-PAMAM-GO composite) as bioprobe for the first time. The surface of glassy carbon electrode (GCE) was coated with AuNPs–ZnO NRs composite film as the platform, which facilitated the electronic transmission rate to enhance the ECL intensity and provide enough active sites for capturing antibody. The resulting ECL immunosensor enabled the real samples detection of Brom with a lower detection limit of 0.3 pg mL −1 (S/N=3) and a wider linear range from 0.001 to 500 ng mL −1 . The proposed immunosensor coupled with the excellent advantages of CdTe QDs-PAMAM-GO and AuNPs–ZnO NRs composite displayed high sensitivity and long-term stability, and provided an approach for determining other important biomarkers. [ABSTRACT FROM AUTHOR]

Eggshell membrane is a natural material, essentially made up of protein fibers having flexibility in the aqueous solution and possessing gas and water permeability. It was used as a biomembrane for immobilization of CdTe quantum dots (QDs) for the development of a simple and sensitive ascorbic acid (AA) biosensor. The layer-by-layer self-assembly technology was used to prepare the multilayer films via the electrostatic interaction between poly(dimethyldiallyl ammonium chloride) (PDDA) and CdTe QDs. Due to the efficient electron-transfer between CdTe QDs and Cu 2+ ions, the fluorescence of CdTe QDs was greatly quenched by Cu 2+ ions. Upon addition of AA, Cu 2+ was reduced to Cu + and the interaction of Cu 2+ - CdTe QDs was destroyed, which inhibit the quenching and thus leading to fluorescence recovery of CdTe QDs. Experimental results showed that the recovery in fluorescence intensity was linearly proportional to the concentration of AA in the range of 10 −12 to 10 −5 mol/L with a detection limit (LOD) of 4.38×10 −13 mol/L under the optimized experimental conditions. The proposed turn-on fluorescence probe was successfully applied for the determination of AA in real samples with satisfactory reproducibility and accuracy. Due to good stability, environmental friendly, cheapness, nontoxic, well behaved optical properties, and biocompatibility, the fabricated bioplatform has the promising future for practical applications. [ABSTRACT FROM AUTHOR]

The primary process in quantum dot solar cells is electron transfer between excited state QDs and semiconductor. There are several key factors controlling this electron transfer process including capping agents. Therefore fundamental understanding of capping agent dependent electron transfer dynamics is much needed. Here, we have employed two capping agents namely thioglycolic acid (TGA) and mercapto propionic acid (MPA) in which the later has one additional methylene group in its structure which plays a significant role on electron transfer process. Hence, we have studied the electron transfer dynamics of TGA and MPA capped CdTe QDs with methyl viologen (MV) in aqueous medium by using steady state and time resolved absorption and fluorescence techniques. The results show that MV quenches the fluorescence of CdTe QDs which is capping agent dependent. The obtained quenching rate constant for TGA and MPA capped CdTe QDs are 8.04×10 10 M −1 s −1 and 1.66×10 10 M −1 s −1 respectively. From the quenching rate constant values, it is clear that there is a significant role of capping agent on electron transfer process. This is due to MPA passivate the surface of QDs more than TGA, which slow down the electron transfer process from QDs to MV. Moreover, the observed radical cation (MV •+ ) from transient absorption measurements confirms that the fluorescence quenching of CdTe QDs by MV is attributed to electron transfer. These experimental results will help to understanding the behavior of QDs with various acceptors towards the applications of quantum dot solar cells. [ABSTRACT FROM AUTHOR]

The present work demonstrates in vitro folic acid sensing with a polyvinyl alcohol (PVA) based hybrid hydrogel as an efficient and cost effective fluorescence quenching based sensor. This new sensor PVA-tryptophan-CdTe QDs (PTQ), exhibited better sensing efficiency with an excellent limit of detection (0.57 pg/ml) compared to commercially available ELISA kits. The excellent sensitivity was attributed to a combination of a strong Photoinduced Electron Transfer process and an Inner Filter Effect in the sensor-folic acid interaction. The real time sensing applications of the sensor was investigated for folic acid present in the blood serum samples of healthy mice and human; and cancer infected mice and human. Our sensor exhibited efficient sensing for folic acid in the blood serum samples of acute myeloid leukemia [limit of detection (LOD) 42.29 ng/ml] and ovarian cancer effected patients (LOD 365 ng/ml). The LOD value indicates that our sensor is highly efficient toward sensing of FA in acute myeloid leukemia as its LOD value lies below 110 ng/ml. Such works will help to bring together material chemists, biologists and clinicians in a single platform to develop cost effective, photostable and specific assays for diagnostic purposes. [ABSTRACT FROM AUTHOR]

An ultrasensitive aptasensor was fabricated as an electrochemical nanotool based on the conformation switching of an aptamer (Apt). The Apt which was covalently attached on the surface of a glassy carbon electrode (GCE) covered with cadmium telluride (CdTe) quantum dots (QDs) works as a unique modifier for assaying cocaine. The Apt was combined with cocaine to form a three-way junction complex; this complex increased the steric hindrance of the modified GCE surface and resulted in a variation of the corresponding current of a redox probe. In the present study, DPV technique for cocaine detection was applied and resulted in an unprecedented detection limit (LOD) of 5.0±0.1 pmol L −1 , which is more sensitive than previously reported methods. One of the greatest advantages of this aptasensor is the elimination of enzymes or antibodies. It is also relatively a highly sensitive, simple, reproducible, and controllable nanotool. Likewise, it can be easily miniaturized, which is a necessary condition for the high-throughput system and on-site applications. The offered nanotool has a great promise for the routine analysis of the ultra-trace amounts of cocaine, which is important for law enforcement and clinical medicine. It is notable to say that further attempts are under way in our laboratory for the construction of other aptasensors with higher performance for specific targets such as the detection of methadone (MTD) and ibuprofen (IBP). [ABSTRACT FROM AUTHOR]

The LCC–CdTe quantum dots (QDs) hybrid was fabricated by mixing the N-lauryl-N, O-carboxymethyl chitosan (LCC) micelle with water-soluble CdTe QDs in an aqueous solution via hydrophobic forces and the electronic attraction. The structures of LCC and LCC–CdTe QDs hybrid were determined by differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The results showed that the lauryl and carboxymethyl were successfully grafted to chitosan oligosaccharide (CSO), and a number of CdTe QDs were encapsulated by LCC micelle to form a core/shell structure. The tested results of the fluorescent characteristics of LCC, CdTe QDs and LCC–CdTe QDs hybrid showed that there were some obvious fluorescent interactions between LCC and CdTe QDs. Meanwhile, with the change in LCC space structure, the fluorescent interactions between LCC and QDs showed different fluorescent characteristics. The QDs fluorescent (FL) intensity increased first and then decreased to almost quenching, while LCC FL intensity decreased continually. [ABSTRACT FROM AUTHOR]