Candida albicans is the most frequent human opportunistic pathogenic fungus and one of the most important causes of
nosocomial infections. In fact, diagnosis of invasive candidiasis presents unique problems. The aim of this work was to
evaluate, by fluorescence image analysis, cellular labeling of C. albicans with CdTe/CdS quantum dots conjugated or
not to concanavalin A (ConA). Yeast cells were incubated with CdTe/CdS quantum dots (QD) stabilized with
mercaptopropionic acid (MPA) (emission peak at 530 nm) for 1 hour. In the overall study we observed no morphological
alterations. The fluorescence microscopic analysis of the yeast cells showed that the non-functionalized QDs do not label
C. albicans cells, while for the QD conjugated to ConA the cells showed a fluorescence profile indicating that the
membrane was preferentially marked. This profile was expected since Concanavalin A is a protein that binds specifically
to terminal carbohydrate residues at the membrane cell surface. The results suggest that the QD-labeled Candida cells
represent a promising tool to open new possibilities for a precise evaluation of fungal infections in pathological
conditions.
Quantum dots (QDs) are a promising class of fluorescent probes that can be conjugated to a variety of specific cell
antibodies. For this reason, simple, cheap and reproducible routes of QDs´s syntheses are the main goal of many
researches in this field. The main objective of this work was to demonstrate the ability of QDs as biolabels for flow
cell cytometry analysis. We have synthesized biocompatible water soluble CdS/Cd(OH)2 and CdTe/CdS QDs and
applied them as fluorescent labels of hematologic cells. CdTe/CdS QDs was prepared using using a simple aqueous
route with mercaptoacetic acid and mercaptopropionic acid as stabilizing agents. The resulting CdTe/CdS QDs can
target biological membrane proteins and can also be internalized by cells. We applied the CdTe/CdS QDs as
biolabels of human lymphocytes and compared the results obtained for lymphocytes treated and non-treated with
permeabilizing agents for cell membranes. Permeabilized cells present higher fluorescence pattern than non
permeabilized ones. We associated antibody A to the CdS/Cd(OH)2 QDs to label type A red blood cell (RBC). In
this case, the O erythrocytes were used as the negative control. The results demonstrate that QDs were successfully
functionalized with antibody A. There was a specific binding of QDs-antibody A to RBC membrane antigen only for
A RBCs. We have also monitored QDs-hematologic cell interaction by using fluorescence microscopy. Our method
shows that QDs can be conjugated to a variety of specific cell antibodies and can become a potential, highly efficient
and low cost diagnostic tool for flow cell cytometry, very compatible with the lasers and filters used in this kind of
equipments.
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