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Despite the versatility of quantum dots (QDs) in optoelectronics and biomedical field, their toxicity risks remain a considerable hindrance for clinical applications. Cytotoxicity of Cadmium containing QDs is well documented and reveals that they are toxic to cells. Reports suggest that the presence of toxic elements at the QD core (e.g., cadmium, selenium) is responsible for its toxicity in in vivo and in vitro levels. Hence, here the toxicity of heavy metal free ZnSe/ZnS QDs on two scenarios were assessed, (i) HEK cells as in vitro system and (ii) Swiss Albino mice as in vivo model. Before toxicity analysis, QDs subjected to various optical and physico-chemical characterization methods such as absorption and emission spectra analysis, observation under U.V light, TEM, DLS, Zeta potential, FTIR, Raman and XPS spectra, ICP-OES, TGA and DTG curve. It is very necessary to characterize the synthesized QDs because their toxicity greatly influenced by the physico-chemical properties. On checking the vulnerability of HEK cells on exposure to ZnSe/ZnS QDs, the obtained results disclose that ZnSe/ZnS QDs showed merest impact on cellular viability at a concentration less than 100 μg/ml. Acute toxicity of 10 mg/kg ZnSe/ZnS QDs was studied in mice and no clinical or behavioural changes were observed. It did not induce any changes in haematological parameters and any loss of body or organ weight. Moderate pathological changes were evident only in the liver, all others organs like kidney, spleen and brain did not show any manifestations of toxicity. Current work lays substantial bedrock for safe biomedical and environmental application of ZnSe/ZnS QDs in near future., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The asymmetric flow field-flow fractionation (AF4) coupled on-line with elemental (inductively coupled plasma-mass spectrometry, ICP-MS) and molecular (fluorescence and UV) detection has been investigated as a powerful tool for the characterization of bioinorganic nano-conjugates. In this study, we described methods for the characterization of biotin-antibody complexes bioconjugated with streptavidin quantum dots (QDs-SA-b-Ab). Operating parameters of AF4 separation technique were optimized and two procedures are proposed using a channel thickness of 350 μm and 500 μm. The use of a 500 μm spacer allowed to achieve an efficient AF4 separation of the QDs-SA-b-Ab complexes from the excess of individual species used in the bioconjugation that was required for a proper characterization of the bioconjugates. Optimization of the AF4 allowed a separation resolution good enough to isolate the QDs-SA-b-Ab bioconjugates from the free excess of b-Ab and QD-SA. The efficiency of the bioconjugation process could be then calculated, obtaining a value of 86% for a 1 QDs-SA: 5 b-Ab bioconjugation ratio. In addition, sample recovery around 90% was achieved., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Colloidal CdSe/ZnS quantum dots were water solubilized by overcoating with an amphiphilic polymer. Human serum albumin (HSA) as a model protein was either adsorbed or chemically linked to the surface of the polymer-coated quantum dots. As the quantum dots are intrinsically fluorescent, and as the polymer coating and the HSA were fluorescent labeled, the final nanoparticle had three differently fluorescent components: the quantum dot core, the polymer shell, and the human serum albumin corona. Cells were incubated with these hybrid nanoparticles, and after removal of non-internalized nanoparticles, exocytosis of the three components of the nanoparticles was observed individually by flow cytometry and confocal microscopy. The data indicate that HSA is partly transported with the underlying polymer-coated quantum dots into cells. Upon desorption of proteins, those initially adsorbed to the quantum dots remain longer inside cells compared to free proteins. Part of the polymer shell is released from the quantum dots by enzymatic degradation, which is on a slower time scale than protein desorption. Data are quantitatively analyzed, and experimental pitfalls, such as the impact of cell proliferation and fluorescence quenching, are discussed.

A current remaining challenge in nanotechnology is the fast and reliable determination of the ratios between engineered nanoparticles and the species attached to their surface after chemical functionalization. The approach proposed herein based on the online coupling of asymmetric flow field-flow fractionation (AF4) with inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS) allows for the first time the direct determination of such ratios in CdSe/ZnS core-shell quantum dot:rat monoclonal IgG2a antibody (QD:Ab) conjugate mixtures in a single run without any previous sample preparation (i.e., derivatization). AF4 provides full recovery and adequate resolution of the resulting bioconjugate from the excess of nanoparticles and proteins used in the different bioconjugation mixtures (1:1, 2:1, and 3:1 QD:Ab molar ratios were assessed). The point-by-point determination by ICP-MS/MS of the metal to sulfur ratios along the bioconjugate fractographic peak allowed disclosing the mixture of the different species in the bioconjugated sample, providing not only the limits of the range of QD:Ab ratios in the different bioconjugate species resulting after functionalization but also a good estimation of their individual relative abundance in the mixture. Interestingly, a wide variety of compositions were observed for the different bioconjugate mixtures studied (QD:Ab molar ratios ranging from 0.27 to 4.6). The resulting weighted QD:Ab ratio computed in this way for each bioconjugate peak matches well with both the global (average) QD:Ab ratio experimentally obtained by the simpler peak area ratio computation and the theoretical QD:Ab molar ratios assayed, which internally validates the procedure developed.

The retention of CdS/ZnS QDs on the epidermis has been confirmed to be one of the core procedures during the root uptake process. However, the retention mechanisms of QDs on the epidermis of woody plant were poorly understood for lacking of an appropriate QD quantitative method. In this study, a novel method for in situ determination of CdS/ZnS QDs retained on the root epidermis was established using synchronous nanosecond time-resolved fluorescence spectroscopy. No correlations between K f values of oleylamine-CdS/ZnS QDs retained on the epidermal tissues and the surface/bulk composition of mangrove root were observed (p > 0.05) due to the existence of endocytosis mechanisms during the QD uptake processes. Moreover, the difference of the CdS/ZnS QDs in water and further translocated to xylem/phloem of root rather than the combination with cell wall/membranes was the predominant reason that caused the K f values to follow the sequence of PEG-COOH-CdS/ZnS QDs < PEG-NH 2 -CdS/ZnS QDs ≪ oleylamine-CdS/ZnS QDs.

A simple fluorescence turn-on sensor has been designed for the highly sensitive detection of glycoproteins on the basis of boronic acid functional polymer capped Mn-doped ZnS quantum dots (QDs@MPS@AAPBA). In the absence of glycoproteins, the fluorescence emission intensity of the QDs@MPS@AAPBA was relatively weaker due to the effective electronic transfer from the QDs to the boron moieties on its surface. While the glycoproteins were introduced into the system, an obvious fluorescence enhancement was observed. It was attributed to the boron moieties covalent binding glycans of the glycoproteins resulting in the electronic transfer process being inhibited. Under the optimal conditions, this fluorescent probe not only could be applied in a wide pH range of 5.0-9.0, but also the binding constants and detection limits of the QDs@MPS@AAPBA for horseradish peroxidase (HRP) and transferrin (TRF) were up to 7.23 × 10 6  M -1 , 1.53 × 10 7  M -1 and 1.44 × 10 -10  M, 3.36 × 10 -10  M, respectively. Finally, this proposed method has also been utilized for the TRF determination in serum without any complicated pretreatment and the recovery was in the range of 95.7%-103.0%. As a result, it is promising for application on the glycoproteins detection in complex biological samples., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: Nanoparticle interactions with cellular membranes and the kinetics of their transport and localization are important determinants of their functionality and their biological consequences. Understanding these phenomena is fundamental for the translation of such NPs from in vitro to in vivo systems for bioimaging and medical applications. Two CdSe/ZnS quantum dots (QD) with differing surface functionality (NH 2 or COOH moieties) were used here for investigating the intracellular uptake and transport kinetics of these QDs., Results: In water, the COOH- and NH 2 -QDs were negatively and positively charged, respectively, while in serum-containing medium the NH 2 -QDs were agglomerated, whereas the COOH-QDs remained dispersed. Though intracellular levels of NH 2 - and COOH-QDs were very similar after 24 h exposure, COOH-QDs appeared to be continuously internalised and transported by endosomes and lysosomes, while NH 2 -QDs mainly remained in the lysosomes. The results of (intra)cellular QD trafficking were correlated to their toxicity profiles investigating levels of reactive oxygen species (ROS), mitochondrial ROS, autophagy, changes to cellular morphology and alterations in genes involved in cellular stress, toxicity and cytoskeletal integrity. The continuous flux of COOH-QDs perhaps explains their higher toxicity compared to the NH 2 -QDs, mainly resulting in mitochondrial ROS and cytoskeletal remodelling which are phenomena that occur early during cellular exposure., Conclusions: Together, these data reveal that although cellular QD levels were similar after 24 h, differences in the nature and extent of their cellular trafficking resulted in differences in consequent gene alterations and toxicological effects.

The influence of the chirality of semiconductor nanocrystals, CdSe/ZnS quantum dots (QDs) capped with L- and D-cysteine, on the efficiency of their uptake by living Ehrlich Ascite carcinoma cells is studied by spectral- and time-resolved fluorescence microspectroscopy. We report an evident enantioselective process where cellular uptake of the L-Cys QDs is almost twice as effective as that of the D-Cys QDs. This finding paves the way for the creation of novel approaches to control the biological properties and behavior of nanomaterials in living cells.

In the current work, using ZnSe ZnS quantum dots (QDs) as representative nanoparticles, the affinities of seven anticancer drugs for bovine serum albumin (BSA) were studied using fluorescence resonance energy transfer (FRET). The FRET efficiency of BSA-QD conjugates can reach as high as 24.87% by electrostatic interaction. The higher binding constant (3.63×10(7)Lmol(-1)) and number of binding sites (1.75) between ZnSe ZnS QDs and BSA demonstrated that the QDs could easily associate to plasma proteins and enhance the transport efficacy of drugs. The magnitude of binding constants (10(3)-10(6)Lmol(-1)), in the presence of QDs, was between drugs-BSA and drugs-QDs in agreement with common affinities of drugs for serum albumins (10(4)-10(6)Lmol(-1)) in vivo. ZnSe ZnS QDs significantly increased the affinities for BSA of Vorinostat (SAHA), Docetaxel (DOC), Carmustine (BCNU), Doxorubicin (Dox) and 10-Hydroxycamptothecin (HCPT). However, they slightly reduced the affinities of Vincristine (VCR) and Methotrexate (MTX) for BSA. The recent work will not only provide useful information for appropriately understanding the binding affinity and binding mechanism at the molecular level, but also illustrate the ZnSe ZnS QDs are perfect candidates for nanoscal drug delivery system (DDS)., (Copyright © 2014 Elsevier B.V. All rights reserved.)

To fully understand the biological and environmental impacts of nanomaterials requires studies that address both sublethal end points and multigenerational effects. Here, we use a nematode to examine these issues as they relate to exposure to two different types of quantum dots, core (CdSe) and core-shell (CdSe/ZnS), and to compare the effect to those observed after cadmium salt exposures. The strong fluorescence of the core-shell QDs allowed for the direct visualization of the materials in the digestive track within a few hours of exposure. Multiple end points, including both developmental and locomotive, were examined at QD exposures of low (10 mg/L Cd), medium (50 mg/L Cd), and high concentrations (100 mg/L Cd). While the core-shell QDs showed no effect on fitness (lifespan, fertility, growth, and three parameters of motility behavior), the core QDs caused acute effects similar to those found for cadmium salts, suggesting that biological effects may be attributed to cadmium leaching from the more soluble QDs. Over multiple generations, we commonly found that for lower life-cycle exposures to core QDs the parents response was generally a poor predictor of the effects on progeny. At the highest concentrations, however, biological effects found for the first generation were commonly similar in magnitude to those found in future generations.

In the biological sciences, the use of core-shell quantum dots (QDs) has gained wide usage but analytical challenges still exist for characterizing the QD structure. The application of energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy (XPS) to bulk materials is relatively straightforward; however, for meaningful applications of surface science techniques to multilayer nanoparticles requires novel modifications and analysis methods. To experimentally characterize the elemental composition and distribution in CdSe/CdS/ZnS QDs, we first develop a XPS signal subtraction technique capable of separating the overlapped selenium 3s (core) and sulfur 2s (shell) peaks (both peaks have binding energies near 230 eV) with higher precision than is typically reported in the nanoparticle literature. This method is valid for any nanoparticle containing selenium and sulfur. Then we apply a correction formula to the XPS data and determine that the 2 nm stoichiometric CdSe core is surrounded by 2 CdS layers and a stoichimetric ZnS monolayer. These findings and the multiapproach methodology represent a significant advancement in the detailed surface science study of multilayer nanoparticles. In agreement with recent surprising findings, the time-of-flight secondary mass spectrometry measurements suggest that the surface sites of the QDs used in this study are primarily covered with a mixture of octadecylphosphonic acid and trioctylphophine oxide.

Cationic multifluorescent quantum dot liposomes (QD-Ls) have been prepared with both hydrophobic and hydrophilic CdSe/ZnS quantum dots by reverse phase evaporation. QD incorporation was confirmed by fluorescence and confocal microscopy. Incorporation did not affect QD photoactivity or damage bilayer or liposome structure. Cell uptake was examined in human hepatocellular carcinoma cells (HuH-7) using cationic and zwitterionic QD-Ls. Cationic QD-Ls were stable in vitro and exhibited high uptake, while zwitterionic QD-Ls aggregated and exhibited low uptake. Given that liposomes are established and versatile platforms for creating cell-targeting therapeutic agents, multifluorescent QD-Ls may offer advanced techniques for imaging hydrophobic and hydrophilic domains simultaneously. If coupled with an encapsulated drug, QD-Ls could be multifunctional and provide imaging, detection, and drug delivery in a single assembly.

Nanoengineered fluorescent response is reported from semiconductor core-shell (CdSe/ZnS) quantum dots in proximity to the surface plasmon polariton field of periodic Ag nanoparticle arrays. Tuning the surface plasmon polariton resonance to the quantum dot exciton emission band results in an enhancement of up to approximately 50-fold in the overall fluorescence efficiency, in a design where each Ag nanoparticle is interconnected by a continuous Ag thin film. Propagating modes of surface plasmon resonances have a direct impact on the fluorescence enhancement.

A convenient route for the synthesis of high-quality overcoated II-VI quantum dots (QDs) is reported in this paper. Simple salts, such as Cd(Ac)2 and Zn(Ac)2 were used to replace organometallics, whose disadvantage is obvious. Size-tunable core/shell structured QDs (CdSe/ZnS, CdSe/CdS, etc.) were synthesized. They were of narrow size distribution and had good monodispersivity and photoluminescence (PL) properties. The spectrum was symmetrical and sharp-pointed (with the full width at half-maximum (fwhm) of about 20-30 nm). The quantum yield (QY) was improved to 60-80% from 20-30% for bare QDs and remained stable at least for 6 months. The primary overcoated QDs were modified with biomacromolecules by a direct mechanical rubbing strategy, which is very simple and fast. The results obtained by UV-vis, PL, atomic force microscopy (AFM), and fluorescence microscopy imaging showed that the modified QDs were of good fluorescent and monodisperse characteristics. They are likely to be used further for biological labels.