concanavalin-a and cadmium-telluride

Semiconductor colloidal quantum dots (QDs) have been applied in biological analysis due to their unique optical properties and their versatility to be conjugated to biomolecules, such as lectins and antibodies, acquiring specificity to label a variety of targets. Concanavalin A (Con A) lectin binds specifically to α-d-mannose and α-d-glucose regions of saccharides that are usually expressed on membranes of mammalian cells and on cell walls of microbials. Candida albicans is the most common fungal opportunistic pathogen present in humans. Therefore, in this work, this fungus was chosen as a model for understanding cells and biofilm-forming organisms. Here, we report an efficient bioconjugation process to bind CdTe (Cadmium Telluride) QDs to Con A, and applied the bioconjugates to label saccharide structures on the cellular surface of C. albicans suspensions and biofilms. By accomplishing hemagglutination experiments and circular dichroism, we observed that the Con A structure and biochemical properties were preserved after the bioconjugation. Fluorescence microscopy images of yeasts and hyphae cells, as well as biofilms, incubated with QDs-(Con A) showed a bright orange fluorescence profile, indicating that the cell walls were specifically labeled. Furthermore, flow cytometry measurements confirmed that over 93% of the yeast cells were successfully labeled by QD-(Con A) complex. In contrast, non-conjugated QDs or QDs-(inhibited Con A) do not label any kind of biological system tested, indicating that the bioconjugation was specific and efficient. The staining pattern of the cells and biofilms demonstrate that QDs were effectively bioconjugated to Con A with specific labeling of saccharide-rich structures on C. albicans. Consequently, this work opens new possibilities to monitor glucose and mannose molecules through fluorescence techniques, which can help to optimize phototherapy protocols for this kind of fungus.

Topics: Cadmium Compounds; Candida albicans; Concanavalin A; Fluorescent Dyes; Glucose; Mannose; Microscopy, Fluorescence; Quantum Dots; Spectrometry, Fluorescence; Tellurium; Thiomalates

Sugar chains are important molecules in cellular recognition and signaling, and quantum dots (QDs) are a very powerful tool for in vitro and in vivo imaging. Herein, we report the preparation of stable sugar-chain-immobilized fluorescent nanoparticles (SFNPs) and their application to the analysis of sugar-chain-protein interactions and cellular imaging. SFNPs were easily prepared by mixing CdTe/CdS core/shell QDs with our previously developed sugar-chain-ligand conjugates. The obtained SFNPs were very stable and could be stored for several months. In the binding analysis, β-galactose- and α-glucose-immobilized SFNPs were specifically interacted with Ricinus communis agglutinin I and concanavalin A, respectively, and made into aggregates. The binding interaction was detected visually, fluorescently, or both. In the experiment for cellular imaging, it was found that SFNPs were predominantly taken up by human hepatocyto carcinoma cells (HepG2), suggesting the possible usage of our designed SFNPs for various biochemical analyses of sugar chains.

Topics: Cadmium Compounds; Concanavalin A; Galactose; Glucose; Hep G2 Cells; Humans; Microscopy, Confocal; Plant Lectins; Protein Binding; Quantum Dots; Selenium Compounds; Tellurium

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.

Topics: Annexin A5; Apoptosis; Cadmium Compounds; Cell Line, Tumor; Concanavalin A; Electrochemical Techniques; Electrodes; Flow Cytometry; Humans; Phosphatidylserines; Polyamines; Quantum Dots; Silicon Dioxide; Tellurium

A simple and rapid fluorescent method was developed for the in situ evaluation of cell surface carbohydrate by homogeneous specific recognition of a quantum dot-lectin nanoprobe to mannosyl groups on the cell surface. The strategy was further used for dynamically monitoring the alteration of cell surface carbohydrate expression in response to drugs.

Topics: Cadmium Compounds; Carbohydrates; Cell Line, Tumor; Cell Membrane; Concanavalin A; Fluorescent Dyes; Humans; K562 Cells; Nanoparticles; Propionates; Quantum Dots; Sensitivity and Specificity; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet; Spectroscopy, Fourier Transform Infrared; Tellurium