Development of acetylcholinesterase biosensor based on CdTe quantum dots/gold nanoparticles modified chitosan microspheres interface

In this paper, a novel acetylcholinesterase (AChE) biosensor was constructed by modifying glassy carbon electrode with CdTe quantum dots (QDs) and excellent conductive gold nanoparticles (GNPs) though chitosan microspheres to immobilize AChE. Since GNPs have shown widespread use particularly for constructing electrochemical biosensors through their high electron-transfer ability, the combined AChE exhibited high affinity to its substrate and thus a sensitive, fast and cheap method for determination of monocrotophos. The combination of CdTe QDs and GNPs promoted electron transfer and catalyzed the electro-oxidation of thiocholine, thus amplifying the detection sensitivity. This novel biosensing platform based on CdTe QDs-GNPs composite responded even more sensitively than that on CdTe QDs or GNPs alone because of the presence of synergistic effects in CdTe-GNPs film. The inhibition of monocrotophos was proportional to its concentration in two ranges, from 1 to 1000ngmL(-1) and from 2 to 15mugmL(-1), with a detection limit of 0.3ngmL(-1). The proposed biosensor showed good precision and reproducibility, acceptable stability and accuracy in garlic samples analysis.     

Luminescent gelatin nanospheres by encapsulating CdSe quantum dots

Quantum dots (QDs) have been encapsulated within gelatin nanoparticles (GNPs), which gives GNPs fluorescent properties and improves the biocompatibility of QDs. Hydrophilic CdSe QDs were produced through thermodecomposition following the ligand‐exchange method, and were then encapsulated in GNPs. The results of high‐resolution transmission electron microscopy and transmission electron microscopy show that CdSe QDs and QDs‐encapsulated GNPs (QDs‐GNPs) have average diameters of 5 ± 1 and 150 ± 10 nm, respectively. Results of both high‐resolution transmission electron microscopy and confocal laser scanning microscopy indicate that CdSe QDs are successfully encapsulated within GNPs. The QDs‐GNPs have distinctive fluorescent properties with maximum emission at 654 nm, with a 24 nm red‐shift comapred with hydrophilic mercaptoundecanoic acid (MUA)‐modified QDs. In addition, an in vitro cytotoxicity test shows that QDs‐GNPs do not have any toxic effect on cells. It is expected that QDs‐GNPs might be an excellent candidate as a contrast agent in bio‐imaging. Copyright © 2013 John Wiley & Sons, Ltd.     

Rapid DNA detection by interface PCR on nanoparticles

A novel, rapid DNA detection method based on fluorescence quenching of quantum dots (QDs) by gold nanoparticles (GNPs) through polymerase chain reaction (PCR) was developed. In proof-of-concept experiments, the length of the amplicon DNA ranging from 152 to 1003 base pairs (bp) could be determined based on quenched fluorescence intensity with 136 bp as the lower limit of effective range. And the real sample detections were also achieved successfully by this developed method. Therefore, this DNA detection method has the potential to be the powerful gene diagnostic tool.     

Autometallographic tracing of quantum dots

A short clarifying view of how semiconductor quantum dots (QDs) can be made visible in tissue sections by autometallographic (AMG) silver enhancement and how the introduction of AMG enhanceable gold nanoparticles into isolated cells can be used to follow the fate of these marked cells in organisms and cell cultures. As the AMG approach for visualizing quantum dots is extremely sensitive, QDs less than one nanometer can be made visible at both LM and EM levels.     

Bioconjugated quantum dots for cancer research: Present status,prospects and remaining issues

Semiconductor quantum dots (QDs) are nanoparticles in which charge carriers are three dimensionally confined or quantum confined. The quantum confinement provides size-tunable absorption bands and emission color to QDs. Also, the photoluminescence (PL) of QDs is exceptionally bright and stable, making them potential candidates for biomedical imaging and therapeutic interventions. Although fluorescence imaging and photodynamic therapy (PDT) of cancer have many advantages over imaging using ionizing radiations and chemo and radiation therapies, advancement of PDT is limited due to the poor availability of photostable and NIR fluorophores and photosensitizing (PS) drugs. With the introduction of biocompatible and NIR QDs, fluorescence imaging and PDT of cancer have received new dimensions and drive. In this review, we summarize the prospects of QDs for imaging and PDT of cancer. Specifically, synthesis of visible and NIR QDs, targeting cancer cells with QDs, in vitro and in vivo cancer imaging, multimodality, preparation of QD-PS conjugates and their energy transfer, photosensitized production of reactive oxygen intermediates (ROI), and the prospects and remaining issues in the advancement of QD probes for imaging and PDT of cancer are summarized.     

Influence of the KBr matrix on the luminescence properties of CdTe quantum dots

The investigation of the luminescence properties of CdTe/KBr composites with encapsulated quantum dots (QDs) of different sizes was performed and the influence of the KBr matrix on the luminescence properties of CdTe QDs was studied. Encapsulation of nanoparticles by a solid matrix caused a bathochromic shift in the luminescence peak and the shift value was the larger the smaller the size of the quantum dots. Interband quantum transition theory was used to explain the influence of the matrix on the luminescence properties of the capsulated CdTe QDs. Theoretical calculations showed that the observed QD luminescence peak corresponded to a 1 s–1 s electronic transition, and its low‐energy shift after the transfer of QDs from dielectric water to the KBr matrix was due to a corresponding decrease in the depths of electrons and holes potential wells.     

Maximizing specificity and yield of PCR by the quantum dot itself rather than property of the quantum dot surface

We found that semiconductor quantum dots (QDs) dramatically improved both product yield and specificity of PCR. The concentration of QDs is important for improving PCR amplification. In the presence of appropriate concentration of mercaptoacetic acid (MAA)-coated QDs, specificity and yield of PCR were enhanced. Also, strong nonspecific bands and weaker smeared bands were eliminated. At lower annealing temperatures (25–45 °C), addition of MAA-coated QDs into the PCR reagent produced specific PCR products without nonspecific sequence amplification. MAA alone did not improve PCR amplification. Streptavidin (SA) surface modified QDs with different size also effectively improved the specificity of PCR, demonstrating that the observed effect was not due to property of the QD surface but instead due to the QD itself. Bovine Serum Albumin (BSA) could relieve Taq polymerase from MAA-coated QDs in PCR by interaction with QDs and therefore imply that QDs improve specificity of PCR by interaction with Taq polymerase. These results demonstrate that QDs, added to reaction mixes at appropriate concentrations, can increase PCR yield and improve PCR specificity, even at low annealing temperatures. We assume that many different surface modified polymeric nanoparticles might have similar effects.     

Patterned Hydrophobic Domains in the Exopolymer Matrix of Shewanella oneidensis MR-1 Biofilms

Water-dispersible amphiphilic surface-engineered quantum dots (QDs) were found to be strongly accumulated within discrete zones of the exopolymer network of Shewanella oneidensis MR-1 biofilms, but not on the cell surfaces. These microdomains showed a patterned distribution in the exopolymer matrix, which led to a restricted diffusion of the amphiphilic nanoparticles.     

Quantum dots-based multifunctional dendritic superstructure for amplified electrochemiluminescence detection of ATP

A novel multifunctional dendrimeric CdSe-CdS-Quantum dots (QDs) hybrid superstructure with highly intense electrochemiluminescence (ECL), fluorescence and excellent magnetic property is prepared for the first time, and successfully applied to amplified ECL assays of ATP using DNA cycle amplification technique. The magnetic nanoparticles (MNPs) were firstly assembled with unique dendrimer nanoclusters (NCs), then large numbers of QDs were labeled onto the dendrimer NCs, the superstructure exhibits highly enhanced ECL and fluorescence than the pure QDs. Remarkable ECL quenching of the nanocomposites by gold nanoparticles (GNPs) was observed, based on which a novel strategy for highly sensitive ATP detection was developed by cycle amplification technique. Furthermore, the nanocomposites with excellent magnetic properties can be easily labeled, separated and immobilized onto a magnetic electrode. In particular, all the procedures such as linking GNPs, sensing target and DNA cycle amplification were directly accomplished on the nanocomposites, which is more rapid, convenient, complete and has better reproducibility than the conventional methods on electrode. To the best of our knowledge, this is the first report on the multifunctional QDs superstructure with highly intense ECL, fluorescence, excellent magnetism and its ECL biosensing, which opens a new pathway for developing QD-based nanocomposites for broad applications in ECL bioassays and optical imaging.     

Bioaccumulation and toxicity of gold nanoparticles after repeated administration in mice

Gold nanoparticles (GNPs) offer a great promise in biomedicine. Currently, there is no data available regarding the accumulation of nanoparticles in vivo after repeated administration. The purpose of the present study was to evaluate the bioaccumulation and toxic effects of different doses (40, 200, and 400 μg/kg/day) of 12.5 nm GNPs upon intraperitoneal administration in mice every day for 8 days.The gold levels in blood did not increase with the dose administered, whereas in all the organs examined there was a proportional increase on gold, indicating efficient tissue uptake. Although brain was the organ containing the lowest quantity of injected GNPs, our data suggest that GNPs are able to cross the blood-brain barrier and accumulate in the neural tissue. Importantly, no evidence of toxicity was observed in any of the diverse studies performed, including survival, behavior, animal weight, organ morphology, blood biochemistry and tissue histology. The results indicate that tissue accumulation pattern of GNPs depend on the doses administered and the accumulation of the particles does not produce sub-acute physiological damage.     

在光动力疗法中应用的量子点

概述了现存的主要量子点的构成及其特点,阐述了量子点的性质主要由量子点的成分、结构、包覆和尺寸所决定。并重点讨论量子点在光动力疗法中,量子点直接代替传统光敏剂、量子点的荧光共振能量转移、量子点作为宽禁带半导体材料TiO2的敏化剂等三种不同应用中,对量子点的要求,通过讨论指出由于其特性,量子点将在光动力疗法中得到更广泛的应用,也对在光动力疗法中应用的量子点的毒性及其他可能产生的问题提出了展望。     

Preparation and Biological Effect of Nucleotide-Capped CdSe/ZnS Quantum Dots on Tetrahymena thermophila

In this paper, we described the preparation and characterization of different types of modified CdSe/ZnS quantum dots (QDs) and explored the biological effects of QDs with different surface modifications on the whole growth of unicellular protozoan Tetrahymena thermophila BF(5) using a thermal activity monitor air isothermal microcalorimeter. Our results demonstrated that adenosine 5'-monophosphate (AMP) showed stronger interaction with QDs than other types of nucleotide. AMP-QDs could stimulate the growth of T. thermophila while mercaptoacetic acid-capped CdSe/ZnS quantum dots inhibited it. In addition, the population density determination and fluorescence imaging of T. thermophila BF(5) also confirmed the results obtained from microcalorimetry. It is believed that this approach will provide a more convenient methodology for the kinetics and thermodynamics of microorganism when coexisting with QDs in real time, and all of which are very significant to understanding the effect of QDs to organism.     

Potential therapeutic application of gold nanoparticles in B-chronic lymphocytic leukemia (BCLL): enhancing apoptosis

Background  

Neuroblastoma, a frequently occurring solid tumour in children, remains a therapeutic challenge as existing imaging tools are inadequate for proper and accurate diagnosis, resulting in treatment failures. Nanoparticles have recently been introduced to the field of cancer research and promise remarkable improvements in diagnostics, targeting and drug delivery. Among these nanoparticles, quantum dots (QDs) are highly appealing due to their manipulatable surfaces, yielding multifunctional QDs applicable in different biological models. The biocompatibility of these QDs, however, remains questionable.     

Nanogel-quantum dot hybrid nanoparticles for live cell imaging

We report here a novel carrier of quantum dots (QDs) for intracellular labeling. Monodisperse hybrid nanoparticles (38 nm in diameter) of QDs were prepared by simple mixing with nanogels of cholesterol-bearing pullulan (CHP) modified with amino groups (CHPNH2). The CHPNH2-QD nanoparticles were effectively internalized into the various human cells examined. The efficiency of cellular uptake was much higher than that of a conventional carrier, cationic liposome. These hybrid nanoparticles could be a promising fluorescent probe for bioimaging.     

Bacteria-mediated in vivo delivery of quantum dots into solid tumor

Semiconductor nanocrystals, so-called quantum dots (QDs), promise potential application in bioimaging and diagnosis in vitro and in vivo owing to their high-quality photoluminescence and excellent photostability as well as size-tunable spectra. Here, we describe a biocompatible, comparatively safe bacteria-based system that can deliver QDs specifically into solid tumor of living animals. In our strategy, anaerobic bacterium Bifidobacterium bifidum (B. bifidum) that colonizes selectively in hypoxic regions of animal body was successfully used as a vehicle to load with QDs and transported into the deep tissue of solid tumors. The internalization of lipid-encapsuled QDs into B. bifidum was conveniently carried by electroporation. To improve the efficacy and specificity of tumor targeting, the QDs-carrying bacterium surface was further conjugated with folic acids (FAs) that can bind to the folic acid receptor overexpressed tumor cells. This new approach opens a pathway for delivering different types of functional cargos such as nanoparticles and drugs into solid tumor of live animals for imaging, diagnosis and therapy.     

“Use of acidophilic bacteria of the genus Acidithiobacillus to biosynthesize CdS fluorescent nanoparticles (quantum dots) with high tolerance to acidic pH”

The use of bacterial cells to produce fluorescent semiconductor nanoparticles (quantum dots, QDs) represents a green alternative with promising economic potential. In the present work, we report for the first time the biosynthesis of CdS QDs by acidophilic bacteria of the Acidithiobacillus genus. CdS QDs were obtained by exposing A. ferrooxidans, A. thiooxidans and A. caldus cells to sublethal Cd²⁺ concentrations in the presence of cysteine and glutathione. The fluorescence of cadmium-exposed cells moves from green to red with incubation time, a characteristic property of QDs associated with nanocrystals growth. Biosynthesized nanoparticles (NPs) display an absorption peak at 360 nm and a broad emission spectra between 450 and 650 nm when excited at 370 nm, both characteristic of CdS QDs. Average sizes of 6 and 10 nm were determined for green and red NPs, respectively. The importance of cysteine and glutathione on QDs biosynthesis in Acidithiobacillus was related with the generation of H₂S. Interestingly, QDs produced by acidophilic bacteria display high tolerance to acidic pH. Absorbance and fluorescence properties of QDs was not affected at pH 2.0, a condition that totally inhibits the fluorescence of QDs produced chemically or biosynthesized by mesophilic bacteria (stable until pH 4.5–5.0). Results presented here constitute the first report of the generation of QDs with improved properties by using extremophile microorganisms.     

Cytotoxicity and cell death induced by engineered nanostructures (quantum dots and nanoparticles) in human cell lines

JBIC Journal of Biological Inorganic Chemistry - In recent years, the industrial use of ZnO quantum dots (QDs) and nanoparticles (NPs) has risen and there is a high chance of these nanoparticles...     

Plasmon-Enhanced Photoluminescence of SiC Quantum Dots for Cell Imaging Applications

Strong photoluminescence enhancement of chemically inert and biocompatible SiC quantum dots (QDs) ensured by their near-field coupling with multipolar localized plasmons is experimentally demonstrated. The main physical mechanisms responsible for this phenomenon are described with the use of three-dimensional FDTD simulations. Nano-Ag/SiN_X/glass plasmonic substrates were shown to be efficiently used for significant luminescence enhancement of fibroblast cells labeled with the SiC QDs. The proposed approach allows a plasmon-induced enhancement of fluorescent cell imaging.     

In vivo skin penetration and metabolic path of quantum dots

The skin is the largest organ of the body and is a potential route of exposure to sunscreens and cosmetics containing nanoparticles;however,the permeability of the skin to these nanoparticles is currently unknown.In this paper,we studied the transdermal delivery capacity through mouse skin of water-soluble CdSeS quantum dots(QDs) and the deposition of these QDs in the body.QD solution was coated onto the dorsal hairless skin of male ICR mice.Fluorescence microscopy and transmission electron microscopy(TEM) were used to observe the distribution of QDs in the skin and organs,and inductively coupled plasma-mass spectrometry(ICP-MS) was used to measure the 111Cd content to indicate the concentration of QDs in plasma and organs.Experimental results indicate that QDs can penetrate into the dermal layer and are limited to the uppermost stratum corneum layers and the hair follicles.Through blood circulation,QDs deposit mostly in liver and kidney and are difficult to clear.111Cd concentration was greater than 14 ng g-1 in kidney after 120 h after 0.32 nmol QDs was applied to a mouse.These results suggest that QDs have in vivo transdermal delivery capacity through mouse skin and are harmful to the liver and kidney.     

Enhancement of cell internalization and photostability of red and green emitter quantum dots upon entrapment in novel cationic nanoliposomes

Two quantum dots (QDs), a green emitter, CdSe and a red emitter, CdSe with ZnS shell are encapsulated into novel liposomes in two different formulations including cationic liposomes. Quantum dots have proven themselves as powerful inorganic fluorescent probes, especially for long‐term, multiplexed imaging and detection. Upon delivery into a cell, in endocytic vesicles such as endosomes, their fluorescence is quenched. We have investigated the potential toxic effects, photophysical properties and cell internalization of QDs in new formulation of liposomes as an in vitro vesicle model. Entrapment of QDs into liposomes is brought about with a decrease in their intrinsic fluorescence and toxicities and an increase in their photostability and lifetime. The biomimetic lipid bilayer of liposomes provides high biocompatibility, thereby enhancing the effectiveness of fluorescent nanoparticles for biological recognition in vitro and in vivo. The prepared lipodots could effectively prevent QDs from photo‐oxidation during storage and when exposed to ultraviolet (UV) light. Moreover, the flow cytometry of HEK 293 T cells showed that the cell internalization of encapsulated QDs in (DSPC/CHO/DOPE/DOAB) liposome is enhanced 10 times compared with non‐encapsulated QD (bare QDs).