Tingting Zheng

Green and facile synthesis of highly biocompatible graphene nanosheets and its application for cellular imaging and drug delivery

A green and facile method for the preparation of gelatin functionalized graphene nanosheets (gelatin–GNS) was reported by using gelatin as a reducing reagent. Meanwhile, the gelatin also played an important role as a functionalized reagent to prevent the aggregation of the graphene nanosheets. The obtained biocompatible gelatin–GNS exhibited excellent stability in water and various physiological fluids including, cellular growth media as well as serum which were critical prerequisites for biomedicine application of graphene. Cellular toxicity test suggested that the gelatin–GNS was nontoxic for MCF-7 cells, even at a high concentration of 200 μg mL−1. Furthermore, the anticancer drug was loaded onto the gelatin–GNS at a high loading capacity via physisorption for cellular imaging and drug delivery. The doxorubicin/gelatin–GNS composite exhibited a high toxicity to kill MCF-7 cells and experienced a gelatin-mediated sustained release in vitro, which has the potential advantage of increasing the therapeutic efficacy. Therefore, the gelatin–GNS could be selected as an ideal drug carrier to be applied in biomedicine studies.

Robust Nonenzymatic Hybrid Nanoelectrocatalysts for Signal Amplification toward Ultrasensitive Electrochemical Cytosensing

We have discovered that magnetic Fe3O4 nanoparticles exhibit an intrinsic catalytic activity toward the electrochemical reduction of small dye molecules. Metallic nanocages, which act as efficient signal amplifiers, can be attached to the surface of Fe3O4 beads to further enhance the catalytic electrochemical signals. The Fe3O4@nanocage core-satellite hybrid nanoparticles show significantly more robust electrocatalytic activities than the enzymatic peroxidase/H2O2 system. We have further demonstrated that these nonenzymatic nanoelectrocatalysts can be used as signal-amplifying nanoprobes for ultrasensitive electrochemical cytosensing.

Design and Implementation of Electrochemical Cytosensor for Evaluation of Cell Surface Carbohydrate and Glycoprotein

A new strategy for assessing cell surface carbohydrates and P-glycoprotein (P-gp) expression status and quantifying the cell numbers with an electrochemical immunoassay was designed. In order to construct the base of the cytosensor, a novel 3-D architecture was initially fabricated by combining nitrogen-doped carbon nanotubes, thionine, and gold nanoparticles via a simple layer-by-layer method. The formed architecture provided an effective matrix for concanavalin A (Con A) binding and made the immobilized Con A hold high stability and bioactivity. On the basis of the specific recognition of cell surface mannosyl groups to Con A, the Con A/3-D architecture interface showed a predominant capability for cell capture. With another coupled signal amplification based on a enzymatic catalytic reaction of HRP toward the oxidation of thionine by the H(2)O(2), which was induced by two-step immunoreactions, the proposed cytosensor showed an excellent analytical performance for the detection of HeLa cells ranging from 8.0 x 10(2) to 2.0 x 10(7) cells mL(-1) with a limit of detection of 500 cells mL(-1). Moreover, with the use of preblocking procedures, the mannosyl groups and P-gp on single HeLa cell could be further detected to be (4 +/- 2) x 10(10) molecules of mannose moieties and 8.47 x 10(6) molecules of P-gp. This strategy offers great promise for sensitive detection of cancer cells and cell surface receptors and thus may help improve cancer diagnosis and treatment.

Toward the Early Evaluation of Therapeutic Effects: An Electrochemical Platform for Ultrasensitive Detection of Apoptotic Cells

The ability for early evaluation of therapeutic effects is a significant challenge in leukemia research. To address this challenge, we developed a novel electrochemical platform for ultrasensitive and selective detection of apoptotic cells in response to therapy. In order to construct the platform, a novel three-dimensional (3-D) architecture was initially fabricated after combining nitrogen-doped carbon nanotubes and gold nanoparticles via a layer-by-layer method. The formed architecture provided an effective matrix for annexin V with high stability and bioactivity to enhance sensitivity. On the basis of the specific recognition between annexin V and phosphatidylserine on the apoptotic cell membrane, the annexin V/3-D architecture interface showed a predominant capability for apoptotic cell capture. Moreover, a lectin-based nanoprobe was designed by noncovalent assembly of concanavalin A on CdTe quantum dots (QDs)-labeled silica nanospheres with poly(allylamine hydrochloride) as a linker. This nanoprobe incorporated both the specific carbohydrate recognition and the multilabeled QDs-based signal amplification. By coupling with the QDs-based nanoprobe and electrochemical stripping analysis, the proposed sandwich-type cytosensor showed an excellent analytical performance for the ultrasensitive detection of apoptotic cells (as low as 48 cells), revealing great potential toward the early evaluation of therapeutic effects.

Gold-Nanosponge-Based Multistimuli-Responsive Drug Vehicles for Targeted Chemo-Photothermal Therapy.

Gold-nanosponge-based multistimuli-responsive drug vehicles are constructed for combined chemo-photothermal therapy with pinpointed drug delivery and release capabilities and minimized nonspecific systemic spread of drugs, remarkably enhancing the therapeutic efficiency while minimizing acute side effects.

Nanoarchitectured electrochemical cytosensors for selective detection of leukemia cells and quantitative evaluation of death receptor expression on cell surfaces.

The variable susceptibility to the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) treatment observed in various types of leukemia cells is related to the difference in the expression levels of death receptors, DR4 and DR5, on the cell surfaces. Quantifying the DR4/DR5 expression status on leukemia cell surfaces is of vital importance to the development of diagnostic tools to guide death receptor-based leukemia treatment. Taking the full advantages of novel nanobiotechnology, we have developed a robust electrochemical cytosensing approach toward ultrasensitive detection of leukemia cells with detection limit as low as ~40 cells and quantitative evaluation of DR4/DR5 expression on leukemia cell surfaces. The optimization of electron transfer and cell capture processes at specifically tailored nanobiointerfaces and the incorporation of multiple functions into rationally designed nanoprobes provide unique opportunities of integrating high specificity and signal amplification on one electrochemical cytosensor. The high sensitivity and selectivity of this electrochemical cytosensing approach also allows us to evaluate the dynamic alteration of DR4/DR5 expression on the surfaces of living cells in response to drug treatments. Using the TRAIL-resistant HL-60 cells and TRAIL-sensitive Jurkat cells as model cells, we have further verified that the TRAIL susceptibility of various types of leukemia cells is directly correlated to the surface expression levels of DR4/DR5. This versatile electrochemical cytosensing platform is believed to be of great clinical value for the early diagnosis of human leukemia and the evaluation of therapeutic effects on leukemia patients after radiation therapy or drug treatment.

A novel aptamer-based competition strategy for ultrasensitive electrochemical detection of leukemia cells.

A robust, nanobiotechnology-based electrochemical cytosensing platform for the detection of acute leukemia cells was developed with high sensitivity, selectivity, acceptable rapidity and excellent extensibility. It utilized the competitive binding of cell-specific aptamers to acute leukemia cells and subsequent voltammetric quantification of the metal signature. Greatly enhanced sensitivity was achieved with dual signal amplification by using Fe3O4 magnetic nanoparticles (MNPs) as carriers to load a large amount of gold nanoparticles (AuNPs) and AuNP-catalyzed silver deposition. The proposed competitive cytosensor showed high sensitivity with a detection limit down to 10 cells. This simple and low-cost electrochemical cytosensing approach offers great promise to extend its application to early detection of human leukemia and possibly to other cancer cells.

Multiplex acute leukemia cytosensing using multifunctional hybrid electrochemical nanoprobes at a hierarchically nanoarchitectured electrode interface

We have developed a robust, nanobiotechnology-based electrochemical cytosensing approach with high sensitivity, selectivity, and reproducibility toward the simultaneous multiplex detection and classification of both acute myeloid leukemia and acute lymphocytic leukemia cells. The construction of the electrochemical cytosensor involves the hierarchical assembly of dual aptamer-functionalized, multilayered graphene-Au nanoparticle electrode interface and the utilization of hybrid electrochemical nanoprobes co-functionalized with redox tags, horseradish peroxidase, and cell-targeting nucleic acid aptamers. The hybrid nanoprobes are multifunctional, capable of specifically targeting the cells of interest, amplifying the electrochemical signals, and generating distinguishable signals for multiplex cytosensing. The as-assembled electrode interface not only greatly facilitates the interfacial electron transfer process due to its high conductivity and surface area but also exhibits excellent biocompatibility and specificity for cell recognition and adhesion. A superstructured sandwich-type sensor geometry is adopted for electrochemical cytosensing, with the cells of interest sandwiched between the nanoprobes and the electrode interface. Such an electrochemical sensing strategy allows for ultrasensitive, multiplex acute leukemia cytosensing with a detection limit as low as ~350 cells per mL and a wide linear response range from 5 × 10(2) to 1 × 10(7) cells per mL for HL-60 and CEM cells, with minimal cross-reactivity and interference from non-targeting cells. This electrochemical cytosensing approach holds great promise as a new point-of-care diagnostic tool for early detection and classification of human acute leukemia and may be readily expanded to multiplex cytosensing of other cancer cells.

Toward therapeutic effects evaluation of chronic myeloid leukemia drug: electrochemical platform for caspase-3 activity sensing.

In recent decades, advanced therapies and novel scientific drug evaluation systems for chronic myeloid leukemia (CML) treatment are very urgent due to its increasing morbidity. The combination of dasatinib with tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) was supposed to be effective for leukemia therapy. Taking full advantage of novel nano-biotechnology, we have developed a robust electrochemical cytosensing approach to profile the therapeutic effects of dasatinib and TRAIL by probing the activity of caspase-3 from apoptotic CML cells. The sensor was on a base of a glassy carbon electrode (GCE) modified with nano-materials composed of Au nanoparticles (AuNPs), poly(dimethyl diallyl ammonium chloride) (PDDA), and carbon nanotubes (CNTs). Then the platform immobilized the biotinylated DEVD-peptide (biotin-Gly-Asp-Gly-Asp-Glu-Val-Asp-Gly-Cys) via the strong bonding between AuNPs and the thiol group (Au-S bond). In particular, the sensor was then constructed with the environmentally friendly alkaline phosphatase (ALP) via the specific interaction between the biotin and streptavidin, and could retest detection indirectly for caspase-3 sensing by detecting the differential pulse voltammetry (DPV) signal of enzymatic catalysis product, ascorbic acid (AA). The results indicated that either dasatinib or TRAIL could successfully induce the apoptosis of CML cells, while the combination of dasatinib and TRAIL resulted in an improved therapeutic effect, suggesting a novel optimized strategy for CML therapy. This novel electrochemical sensing strategy exhibits attractive advantages of environmental benignity, simple performance, high stability, and may be readily expanded to evaluate other cancer therapeutic effects.

Controlled Dealloying of Alloy Nanoparticles toward Optimization of Electrocatalysis on Spongy Metallic Nanoframes

Atomic-level understanding of the structural transformations of multimetallic nanoparticles triggered by external stimuli is of vital importance to the enhancement of our capabilities to fine-tailor the key structural parameters and thereby to precisely tune the properties of the nanoparticles. Here, we show that, upon thermal annealing in a reducing atmosphere, Au@Cu2O core-shell nanoparticles transform into Au-Cu alloy nanoparticles with tunable compositional stoichiometries that are predetermined by the relative core and shell dimensions of their parental core-shell nanoparticle precursors. The Au-Cu alloy nanoparticles exhibit distinct dealloying behaviors that are dependent upon their Cu/Au stoichiometric ratios. For Au-Cu alloy nanoparticles with Cu atomic fractions above the parting limit, nanoporosity-evolving percolation dealloying occurs upon exposure of the alloy nanoparticles to appropriate chemical etchants, resulting in the formation of particulate spongy nanoframes with solid/void bicontinuous morphology composed of hierarchically interconnected nanoligaments. The nanoporosity evolution during percolation dealloying is synergistically guided by two intertwining structural rearrangement processes, ligament domain coarsening driven by thermodynamics and framework expansion driven by Kirkendall effects, both of which can be maneuvered by controlling the Cu leaching rates during the percolation dealloying. The dealloyed nanoframes possess large open surface areas accessible by the reactant molecules and high abundance of catalytically active undercoordinated atoms on the ligament surfaces, two unique structural features highly desirable for high-performance electrocatalysis. Using the room temperature electro-oxidation of methanol as a model reaction, we further demonstrate that, through controlled percolation dealloying of Au-Cu alloy nanoparticles, both the electrochemically active surface areas and the specific activity of the dealloyed metallic nanoframes can be systematically tuned to achieve the optimal electrocatalytic activities.