Jing-Jing Zhang

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.

Graphene-assisted dual amplification strategy for the fabrication of sensitive amperometric immunosensor

A sensitive electrochemical immunosensor with graphene-assisted signal amplification has been developed. In order to construct the base of the immunosensor, a novel hybrid architecture was initially fabricated by combining poly (diallyldimethylammonium chloride) functionalized graphene nanosheets (PDDA-G) and gold nanoparticles (AuNPs) via a simple sonication-induced assembly. The formed hybrid architecture provided an effective matrix for antibody immobilization with good stability and bioactivity. Subsequently, a smart, multilabel, and graphene-based nanoprobe that contains gold nanoparticles functionalized exfoliated graphene oxide and horseradish peroxidase-secondary antibodies was designed for constructing a novel sandwiched electrochemical immunosensor. Enhanced sensitivity was obtained by combining the advantages of high-binding capability and excellent electrical conductivity of hybrid architecture with the multilabel signal amplification. On the basis of the dual signal amplification strategy of graphene-based architecture and the multilabel, the immunosensor displayed excellent analytical performance for the detection of human IgG (HIgG) range from 0.1 to 200 ng/mL with a detection limit of 0.05 ng/mL at 3σ. Moreover, the proposed method showed good precision, acceptable stability and reproducibility, and could be used for the detection of HIgG in real samples. Therefore, the present strategy definitely paves a way for the wide application of graphene in clinical research.

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.

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.