One-pot synthesis of GSH-Capped CdTe quantum dots with excellent biocompatibility for direct cell imaging

Physico-Chemical Properties of CdTe/Glutathione Quantum Dots Obtained by Microwave Irradiation for Use in Monoclonal Antibody and Biomarker Testing

In this report, we present the results on the physicochemical characterization of cadmium telluride quantum dots (QDs) stabilized with glutathione and prepared by optimizing the synthesis conditions. An excellent control of emissions and the composition of the nanocrystal surface for its potential application in monoclonal antibody and biomarker testing was achieved. Two samples (QDYellow, QDOrange, corresponding to their emission colors) were analyzed by dynamic light scattering (DLS), and their hydrodynamic sizes were 6.7 nm and 19.4 nm, respectively. Optical characterization by UV-vis absorbance spectroscopy showed excitonic peaks at 517 nm and 554 nm. Photoluminescence spectroscopy indicated that the samples have a maximum intensity emission at 570 and 606 nm, respectively, within the visible range from yellow to orange. Infrared spectroscopy showed vibrational modes corresponding to the functional groups OH-C-H, C-N, C=C, C-O, C-OH, and COOH, which allows for the formation of functionalized QDs for the manufacture of biomarkers. In addition, the hydrodynamic radius, zeta potential, and approximate molecular weight were determined by dynamic light scattering (DLS), electrophoretic light scattering (ELS), and static light scattering (SLS) techniques. Size dispersion and the structure of nanoparticles was obtained by Transmission Electron Microscopy (TEM) and by X-ray diffraction. In the same way, we calculated the concentration of Cd2+ ions expressed in mg/L by using the Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-OES). In addition to the characterization of the nanoparticles, the labeling of murine myeloid cells was carried out with both samples of quantum dots, where it was demonstrated that quantum dots can diffuse into these cells and connect mostly with the cell nucleus.

Rice Seedlings and Microorganisms Mediate Biotransformation of Se in CdSe/ZnS Quantum Dots to Volatile Alkyl Selenides

Quantum dots (QDs) are widely applied and inevitably released into the environment. The biotransformation of Se in typical CdSe/ZnS QDs coated with glutathione (CdSe/ZnS-GSH) to volatile alkyl selenides and the fate of alkyl selenides in the hydroponically grown rice system were investigated herein. After a 10-day exposure to CdSe/ZnS-GSH (100 nmol L-1), seven alkyl selenides, dimethyl selenide (DMSe), dimethyl diselenide (DMDSe), methyl selenol (MSeH), ethylmethyl selenide (EMSe), ethylmethyl diselenide (EMDSe), dimethyl selenenyl sulfide (DMSeS), and ethylmethyl selenenyl sulfide (EMSeS), were detected in the exposure system using the suspect screening strategy. CdSe/ZnS-GSH was first biotransformed to DMSe and DMDSe by plant and microorganisms. The generated DMSe was volatilized to the gas phase, adsorbed and absorbed by leaves and stems, downward transported, and released into the hydroponic solution, whereas DMDSe tended to be adsorbed/absorbed by roots and upward transported to stems. The airborne DMSe and DMDSe also partitioned from the gas phase to the hydroponic solution. DMSe and DMDSe in the exposure system were further transformed to DMSeS, EMSeS, EMSe, EMDSe, and MSeH. This study gives a comprehensive understanding on the behaviors of Se in CdSe/ZnS-GSH in a rice plant system and provides new insights into the environmental fate of CdSe/ZnS QDs.

Glutathione-Capped ZnS Quantum Dots-Urease Conjugate as a Highly Sensitive Urea Probe

Abstract

Quantum dots (QDs) possess characteristic chemical and optical features. In this light, ZnS QDs capped with glutathione (GSH) were synthesized via an easy aqueous co-precipitation technique. Fabricated QDs were characterized in terms of X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), Fourier transform infrared (FTIR) and Zeta potential analyses. Optical properties were examined using photoluminescence (PL) and ultraviolet–visible (UV–visible) spectroscopies. Moreover, GSH-capped ZnS QDs were evaluated as an optical probe for non-enzymatic detection of urea depending on the quenching of PL intensity of ZnS QDs in the presence of urea from concentration range of 0.5–5 mM with a correlation coefficient (R2) of 0.995, sensitivity of 0.0875 mM−1 and LOD of 0.426 mM. Furthermore, GSH-capped ZnS QDs-urease conjugate was utilized as an optical probe for enzymatic detection of urea in the range from 1.0 µM to 5.0 mM. Interestingly, it was observed that urea has a good affinity towards ZnS QDs-urease conjugate with a linear relationship between the change of PL intensity and urea concentration. It was found that R2 is 0.997 with a sensitivity of 0.042 mM−1 for mM concentration (0.5–5 mM) and LOD of 0.401 mM. In case of µM concentration range (1–100 µM), R2 was 0.971 with a sensitivity of 0.0024 µM−1 and LOD of 0.687 µM. These data suggest that enzyme conjugation to capped QDs might improve their sensitivity and applicability.

Graphical Abstract

A facile and high-sensitive bio-sensing of the V617F mutation in JAK2 gene by GSH-CdTe-QDs FRET-based sensor

This study aimed to directly detect the V617F point mutation of the Janus kinase 2 (JAK2) gene in the target DNA using a FRET-based biosensor. The water-soluble GSH-CdTe-QDs were synthesized by a one-step process, then GSH-QD conjugated to the termini amino-modified oligonucleotides target via carboxylic groups on the QD surface. The prepared QDs-DNA biosensor was applied in the quantitative and rapid detection of V617F mutation with a detection limit of 3 × 10^-9 mol L^-1 based on the FRET mechanism. In other words, detecting the V617F mutation by bio-sensing technology would be much simpler, cheaper, time-saving, highly sensitive, and more convenient than molecular diagnostic tools. Furthermore, the nano-biosensor was applied to detect the V617F mutation in clinical samples compared to the common ARMS-PCR (Amplification Refractory Mutation System-Polymerase Chain Reaction) standard method. The results revealed that the GSH-capped biosensors would be effective for V617F mutation detection in samples distinguished with satisfactory analytical outcomes. Therefore, the designed fluorescence nanoprobe is suitable for the specific detection of V617F mutation of the JAK2 gene in clinical samples.

Immobilization of Glucose Oxidase on Glutathione Capped CdTe Quantum Dots for Bioenergy Generation

An efficient immobilization of Glucose oxidase (GOx) on an appropriate substrate is one of the main challenges of developing fuel cells that allow energy to be obtained from renewable substrates such as carbohydrates in physiological environments. The research importance of biofuel cells relies on their experimental robustness and high compatibility with biological organisms such as tissues or the bloodstream with the aim of obtaining electrical energy even from living systems. In this work, we report the use of 5,10,15,20 tetrakis (1-methyl-4-pyridinium) porphyrin and glutathione capped CdTe Quantum dots (GSH-CdTeQD) as a support matrix for the immobilization of GOx on carbon surfaces. Fluorescent GSH-CdTeQD particles were synthesized and their characterization by UV-Vis spectrophotometry showed a particle size between 5–7 nm, which was confirmed by DLS and TEM measurements. Graphite and Toray paper electrodes were modified by a drop coating of porphyrin, GSH-CdTeQD and GOx, and their electrochemical activity toward glucose oxidation was evaluated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Additionally, GOx modified electrode activity was explored by scanning electrochemical microscopy, finding that near to 70% of the surface was covered with active enzyme. The modified electrodes showed a glucose sensitivity of 0.58 ± 0.01 μA/mM and an apparent Michaelis constant of 7.8 mM. The addition of BSA blocking protein maintained the current response of common interferent molecules such as ascorbic acid (AA) with less than a 5% of interference percentage. Finally, the complex electrodes were employed as anodes in a microfluidic biofuel cell (μBFC) in order to evaluate the performance in energy production. The enzymatic anodes used in the μBFC allowed us to obtain a current density of 7.53 mAcm−2 at the maximum power density of 2.30 mWcm−2; an open circuit potential of 0.57 V was observed in the biofuel cell. The results obtained suggest that the support matrix porphyrin and GSH-CdTeQD is appropriate to immobilize GOx while preserving the enzyme’s catalytic activity. The reported electrode arrangement is a viable option for bioenergy production and/or glucose quantification.

Encapsulation of a Desmodium intortum Protein Isolate Pickering Emulsion of β-Carotene: Stability, Bioaccesibility and Cytotoxicity

Owing to their excellent characteristics, Pickering emulsions have been widely used in the development and the application of new carriers for embedding and for delivering active compounds. In this study, β-carotene was successfully encapsulated in a Pickering emulsion stabilized using Desmodium intortum protein isolate (DIPI). The results showed that the encapsulation efficiencies of β-carotene in the control group Tween 20 emulsion (TE) and the DIPI Pickering emulsion (DIPIPE) were 46.7 ± 2.5% and 97.3 ± 0.8%, respectively. After storage for 30 days at 25 °C and 37 °C in a dark environment, approximately 79.4% and 72.1% of β-carotene in DIPIPE were retained. Compared with TE, DIPIPE can improve the stability of β-carotene during storage. In vitro digestion experiments showed that the bioaccessibility rate of β-carotene in DIPIPE was less than that in TE. Cytotoxicity experiments showed that DIPI and β-carotene micelles within a specific concentration range exerted no toxic effects on 3T3 cells. These results indicate that DIPIPE can be used as a good food-grade carrier for embedding and transporting active substances to broaden the application of the protein-based Pickering emulsion system in the development of functional foods.

Two-Photon Time-Gated In Vivo Imaging of Dihydrolipoic-Acid-Decorated Gold Nanoclusters

Due to the unique advantages of two-photon technology and time-resolved imaging technology in the biomedical field, attention has been paid to them. Gold clusters possess excellent physicochemical properties and low biotoxicity, which make them greatly advantageous in biological imaging, especially for in vivo animal imaging. A gold nanocluster was coupled with dihydrolipoic acid to obtain a functionalized nanoprobe; the material displayed significant features, including a large two-photon absorption cross-section (up to 1.59 × 105 GM) and prolonged fluorescence lifetime (>300 ns). The two-photon and time-resolution techniques were used to perform cell imaging and in vivo imaging.

Multiplexed bio-imaging using cadmium telluride quantum dots synthesized by mathematically derived process parameters in a continuous flow active microreactor

Quantum dots (QDs) are semiconductor nanocrystals with unique size-tunable emissions. To obtain a precise emission spectrum, monodispersity in size is imperative, which is achieved by controlling the reaction kinetics in a continuous flow of active microreactors. Further, a multivariate approach (dimensional analysis) is employed to impose stringent control on the reaction process resulting in monodispersed preparation of cadmium telluride (CdTe) quantum dots. Dimensional analysis knits multiple variables into a dimensionless mathematical form which not only predicts parameters precisely to obtain narrow size tunability but also guarantees reproducibility in synthesis. Analytical, structural, and optical characterization of the microreactor synthesized polydimethylsiloxane (PDMS) coated CdTe QDs reveal quantum efficient (61.5%), photostable (44%), and biocompatible nanocrystals of 5-15 nm. Further, PDMS-coated QDs (P-QDs) are conjugated with organelle-specific antibodies/biomarkers for in-vitro imaging in NIH 3T3 cells. Likewise, proliferating cell nuclear antigen (PCNA) and anti-myosin (MF20), cardiomyocytes antibodies are conjugated with P-QDs (red and green, respectively) to image the zebrafish's cardiac tissue. Antibodies tagged with quantum dots are imaged simultaneously using confocal microscopy. Thus, multiplexed bio-imaging of in-vitro and zebrafish tissue is demonstrated successfully. The results indicate the suitability of continuous flow active microreactor in conjunction with the mathematical prediction of process parameters to synthesize reproducibly monodispersed and quantum efficient QDs.

Water-soluble ZnCuInSe quantum dots for bacterial classification, detection, and imaging

Bacteria are everywhere and pose severe threats to human health and safety. The rapid classification and sensitive detection of bacteria are vital steps of bacterial community research and the treatment of infection. Herein, we developed optical property-superior and heavy metal-free ZnCuInSe quantum dots (QDs) for achieving rapid discrimination of Gram-positive/Gram-negative bacteria by the naked eye; driven by the structural differences of bacteria, ZnCuInSe QDs are effective in binding to Gram-positive bacteria, especially Staphylococcus aureus (S. aureus), in comparison with Gram-negative bacteria and give discernable color viewed by the naked eye. Meanwhile, based on its distinctive fluorescence response, the accurate quantification of S. aureus was investigated with a photoluminescence system in the concentration ranges of 1 × 10³ to 1 × 10¹¹ CFU/mL, with a limit of detection of 1 × 10³ CFU/mL. Furthermore, we demonstrated the feasibility of ZnCuInSe QDs as a fluorescence probe for imaging S. aureus. This simple strategy based on ZnCuInSe QDs provides an unprecedented step for rapid and effective bacterial discrimination, detection, and imaging.

Multicolor nitrogen dots for rapid detection of thiram and chlorpyrifos in fruit and vegetable samples

The development of sensitive fluorescence sensors and efficient preparation of samples is a challenge in the detection of pesticides in complex samples. In this study, multicolor nitrogen dots (M-Ndots) were synthesised via microwave irradiation at 140 °C for 10 min with 5-amino-1H-tetrazole and p-phenylenediamine as precursors, which have a high fluorescence quantum yield of up to 31%. Furthermore, the M-Ndots were employed as fluorescence sensors for pesticide detection by being combined with a gas membrane separation device, to eliminate the interference from the complex sample matrix. In this process, the M-Ndots were used for sensing thiram and chlorpyrifos through their affinities to Cu²⁺ and Fe³⁺, respectively. Because thiram could decompose into volatile CS₂, its derivate was sensed using the fluorescence of M-Ndots via a complexation reaction with Cu²⁺. Chlorpyrifos, due to its volatility, can reduce the Fe³⁺ ion by inhibiting the activity of acetylcholinesterase, which produces H₂O₂ to oxidise Fe²⁺. In a real application, the time consumption for 96 samples was less than 30 min in one run of the gas membrane separation device. The recoveries for thiram and chlorpyrifos ranged from 90.0% to 115.0%, and the analytical results were validated using LC-MS/MS methods, with relative errors ranging from -7.4% to 10.1%.

Glutathione Modified Fluorescent CdS QDs Synthesized Using Environmentally Benign Pathway for Detection of Mercury Ions in Aqueous Phase

An adept, rapid and novel water-soluble glutathione functionalized CdS quantum dots (GSH@CdS QDs) were fabricated using green pathway for sensing of heavy metal contamination prevalent in industrial wastewater. GSH@CdS QDs were facilely synthesized in an aqueous phase reaction and were effectively characterized using FT-IR, XRD, FESEM, HRTEM and EDX techniques. The distinct fluorescence characteristics of GSH@CdS QDs were explored and the QDs showed selective sensitivity towards mercury ions with a low limit of detection of 0.54 nM under optimal conditions. The detailed interaction between GSH@CdS QDs and Hg²⁺ and the probable fluorescence quenching mechanism were established in this study. In comparison to already reported fluorescent probes, GSH@CdS QDs showed high sensitivity, biocompatibility, long fluorescence stability and convenient removal of mercury ions. Graphical Abstract Facile green route for the fabrication of glutathione capped CdS quantum dots for fluorescence-based detection of toxic Hg²⁺ ions.

A sensitive and visual molecularly imprinted fluorescent sensor incorporating CaF2 quantum dots and β-cyclodextrins for 5-hydroxymethylfurfural detection

Calcium fluoride (CaF₂) quantum dots have many applications in various fields. But there is no report on fluorescent characteristics of CaF₂ quantum dots (CaF₂ QDs). Here, a synthesis of multiple-color emission CaF₂ QDs by changing the temperature, time and raw ratio is reported, by which the CaF₂ QDs with purple, blue, green, and yellow emission can be obtained, respectively. They were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). On this basis, a novel molecular imprinting ratiometric fluorescence sensor (MIR sensor) had been constructed based on the prepared CaF₂ QDs and CdTe QDs, in which the yellow emission CaF₂ QDs was used as a responsive signal material and the red emission CdTe QDs was served as a reference signal material. And the β-CD and methylacrylic acid (MAA) as bifunctional monomers were used for constructing the specific molecularly imprinted polymers (MIPs) in MIR sensor. This MIR sensor was applied for highly selective and excellent sensitive detection of 5-hydroxymethylfurfural (HMF). Under optimum conditions, it exhibited an excellent linear relationship between the fluorescence intensity ratio (I₅₉₉/I₆₂₅) and the concentration of HMF in the range of 0.1-6.0 μg/mL with a detection limit of 0.043 μg/mL. Finally, the established HMF-MIR sensor was successfully utilized to detect HMF in honey with satisfactory results. This work provided a reference for the application of the CaF₂ QDs and the detection of the furfural substances.

Eco-friendly synthesis of glutathione-capped CdTe/CdSe/ZnSe core/double shell quantum dots: their cytotoxicity and genotoxicity effects on Chinese hamster ovary cells

In this work, we report green one-pot synthesis, cytotoxicity and genotoxicity of glutathione-capped CdTe/CdSe/ZnSe heterostructured quantum dots (QDs) using a label-free xCELLigence RTCA system as well as the Cytokinesis Blocked Micronucleus assay. The as-synthesised nanocrystals displayed good optical properties and were spherical in shape with an average particle diameter of 5.9 ± 1.13 nm. The intracellular uptake study showed that most of the as-synthesised glutathione stabilized QDs penetrated the cell membranes and were found randomly localized in the cytoplasm of Chinese Hamster Ovary (CHO) cells even at a lower concentration of 0.5 μg ml-1. The QDs showed no cytotoxicity to Chinese Hamster Ovary (CHO) cells at six concentrations tested (0.5, 1.0, 2.5, 5.0, 10, and 25 μg ml-1). However, at 50 and 100 μg ml-1 the material was cytotoxic at significant p values of 3.1 × 10-4 and 9.47 × 10-10, respectively. Likewise, the material was found to be genotoxic at almost all concentrations tested. The genotoxicity of the nanocrystals in question confers unfavorable potential to all complex heterostructured nanocrystals. Hence, more studies are needed to negate the prevailing assumption that multishell passivation provides enough protection against intracellular QD core dissolution or the production of reactive oxygen species (ROS) before these nanomaterials can be used in vivo for human health applications.