Haoting Lu

The cytotoxicity of cadmium based, aqueous phase -Synthesized, quantum dots and its modulation by surface coating

In this report, we evaluated the cytotoxicity of a series of quantum dots (QDs) directly synthesized in aqueous phase, i.e., thiols-stabilized CdTe, CdTe/CdS core-shell structured and CdTe/CdS/ZnS core-shell-shell structured QDs, with a variety of cell lines including K562 and HEK293T. We have demonstrated that the CdTe QDs are highly toxic for cells due to the release of cadmium ions. Epitaxial growth of a CdS layer reduces the cytotoxicity of QDs to a small extent. However, the presence of a ZnS outlayer greatly improves the biocompatibility of QDs, with no observed cytotoxicity even at very high concentration and long-time exposure in cells. Our systematic investigation clearly shows that the cytotoxicity of QDs can be modulated through elaborate surface coatings and that the CdTe/CdS/ZnS core-shell-shell structured QDs directly synthesized in aqueous phase are highly promising biological fluorescent probes for cellular imaging.

Ultrasensitive, Multiplexed Detection of Cancer Biomarkers Directly in Serum by Using a Quantum Dot-Based Microfluidic Protein Chip

Sensitive and selective detection for cancer biomarkers are critical in cancer clinical diagnostics. Here we developed a microfluidic protein chip for an ultrasensitive and multiplexed assay of cancer biomarkers. Aqueous-phase-synthesized CdTe/CdS quantum dots (aqQDs) were employed as fluorescent signal amplifiers to improve the detection sensitivity. Secondary antibodies (goat anti-mouse IgG) were conjugated to luminescent CdTe/CdS QDs to realize a versatile fluorescent probe that could be used for multiplexed detection in both sandwich and reverse phase immunoassays. We found that our microfluidic protein chip not only possessed ultrahigh femtomolar sensitivity for cancer biomarkers, but was selective enough to be directly used in serum. This protein chip thus combines the high-throughput capabilities of a microfluidic network with the high sensitivity and multicolor imaging ability offered by highly fluorescent QDs, which can become a promising diagnostic tool in clinical applications.

H2O2-sensitive quantum dots for the label-free detection of glucose.

A novel label-free detection system based on CdTe/CdS quantum dots (QDs) was designed for the direct measurement of glucose. Herein we demonstrated that the photoluminescence (PL) of CdTe/CdS QDs was sensitive to hydrogen peroxide (H(2)O(2)). With d-glucose as a substrate, H(2)O(2) that intensively quenched the QDs PL can be produced via the catalysis of glucose oxidase (GOx). Experimental results showed that the decrease of the QDs PL was proportional to the concentration of glucose within the range of 1.8 microM to 1mM with the detection limit of 1.8 microM under the optimized experimental conditions. In addition, the QD-based label-free glucose sensing platform was adapted to 96-well plates for fluorescent assay, enhancing the capabilities and conveniences of this detection platform. An excellent response to the concentrations of glucose was found within the range of 2-30 mM. Glucose in blood and urine samples was effectively detected via this strategy. The comparison with commercialized glucose meter indicated that this proposed glucose assay system is not only simple, sensitive, but also reliable and suitable for practical application. The high sensitivity, versatility, portability, high-throughput and low cost of this glucose sensor implied its potential in point-of-care clinical diagnose of diabetes and other fields.

Ultra-photostable, non-cytotoxic, and highly fluorescent quantum nanospheres for long-term, high-specificity cell imaging

A new class of fluorescent quantum nanospheres (QNs) is directly achieved in aqueous phase through a facile one-pot microwave irradiation (MWI) strategy. Multi-color QNs with maximum emission wavelengths ranging from 525 to 610 nm and PLQY of 30-60% are facilely prepared through this new MWI strategy. In addition to strong fluorescence, these QNs possess excellent photostability, preserving ∼90% of the original intensity after 70 min high-power UV irradiation (100 W Xeon lamp). In sharp contrast, the fluorescence of CdTe/CdS/ZnS core-shell-shell quantum dots (QDs), recognized as established fluorescent probes with robust photostability, decrease to ∼50% under the same conditions. Besides, cytotoxicity assessment demonstrates that the prepared QNs exhibit favorable cytocompatibility to K562 cells with high concentration (3 μmol) and long-time incubation (24 h). Furthermore, cellular imaging results demonstrate that the as-prepared QNs are remarkably efficacious for long-term and high-specificity immunofluorescent cellular labeling, and multi-color cell imaging. Our systematical investigation clearly shows that these high-performance QNs may serve as practical and powerful tools for various biological researches, such as in vivo and in vitro imaging.

One‐Pot Encapsulation of Luminescent Quantum Dots Synthesized in Aqueous Solution by Amphiphilic Polymers

A simple one-pot polymer encapsulation method is developed for group II-VI semiconductor quantum dots (QDs) synthesized in aqueous solution. The micelles of amphiphilic polymers, such as octadecylamine-modified poly(acrylic acid), capture and encapsulate the QDs when the original hydrophilic ligands, namely 3-mercaptopropionic acid (MPA), capped on the CdTe/CdS core/shell QDs are partially or fully exchanged by the hydrophobic ligands, 1-dodecanethiol. The molar ratio of the amphiphilic polymer to QDs plays a crucial role in determining the final morphology of the encapsulated structures, including the number of QDs encapsulated in one polymeric micelle. Importantly, the polymer coating significantly improves the optical properties of the QDs, which enhances the photoluminescence quantum yield by about 50%. Furthermore, the photostability of the amphiphilic polymer-coated QDs is much better than that of the synthesized QDs capped with MPA.

A facile low temperature growth of CdTe nanocrystals using novel dithiocarbamate ligands in aqueous solution

Proline dithiocarbamic acid disodium salt (ProDTC) was first explored as a novel ligand, instead of the usual used thiols, for the synthesis of CdTe nanocrystals (NCs). Due to the weak bonding between Cd ions and ProDTC, CdTe NCs show rapid nucleation and growth at much lower temperature (30–50 °C) compared to the traditional synthesis in an aqueous solution. Moreover, faster growth of ProDTC-CdTe NCs under lower pH value was observed, while the thiol-CdTe system has an opposite tendency. The distinct growth kinetics is ascribed to the different complex constants between ProDTC-Cd and thiol-Cd, which has significant influence on the monomer activity. Although the photoluminescence quantum yield (PLQY) of as-prepared NCs was relatively low, it can be easily increased up to about 50% after further treatment of ligand exchange by replacing the surface-binding ProDTC molecules with the mercaptopropionic acid.

Microwave-assisted synthesis of water-dispersed core/(doped) shell quantum dots

CdTe/Cd1-xMnxS core-shell structure nanoparticles were successfully synthesized in aqueous solution assisted by microwave irradiation. The photoluminescence spectra showed that incorporating low level Mn2+ in outer inorganic shell will not quench the photoemission of quantum dos. The doped nanocrystals exhibited high photoluminescence quantum yield (PLQY), reaching 52% in water under optimum condition.

Label-free detection of glucose based on quantum dots

A simple nanobiosensor based on CdTe/CdS quantum dots (QDs) was designed for the direct determination of glucose with high sensitivity. Herein we demonstrated that the photoluminescence (PL) of CdTe/CdS QDs was sensitive to hydrogen peroxide (H2O2). With glucose as substrate and glucose oxidase (GOx) as catalyzer, the product, H2O2 could quench the fluorescence of QDs. Experimental results showed that the decrease of fluorescent intensity was proportional to the concentration of glucose within the range of 1.8µM-1mM under the optimized experimental conditions. In addition, the detection was completed in 96-well plate as an original model of blood sugar detector. A good linear relationship was found within the range of 2mM–30mM. This QDs based sensor for glucose has the potential to be a portable blood sugar detector due to its high sample throughput, short assay time, low sample consumption and reduced overall cost.