Patricia M. A. Farias

Investigation of red blood cell antigens with highly fluorescent and stable semiconductor quantum dots

We report a new methodology for red blood cell antigen expression determination by a simple labeling procedure employing luminescent semiconductor quantum dots. Highly luminescent and stable core shell cadmium sulfide/cadmium hydroxide colloidal particles are obtained, with a predominant size of 9 nm. The core-shell quantum dots are functionalized with glutaraldehyde and conjugated to a monoclonal anti-A antibody to target antigen-A in red blood cell membranes. Erythrocyte samples of blood groups A+, A2+, and O+ are used for this purpose. Confocal microscopy images show that after 30 min of conjugation time, type A+ and A2+ erythrocytes present bright emission, whereas the O+ group cells show no emission. Fluorescence intensity maps show different antigen expressions for the distinct erythrocyte types. The results obtained strongly suggest that this simple labeling procedure may be employed as an efficient tool to investigate quantitatively the distribution and expression of antigens in red blood cell membranes.

Studying taxis in real time using optical tweezers: Applications for Leishmania amazonensis parasites

Beads trapped by an optical tweezers can be used as a force transducer for measuring forces of the same order of magnitude as typical forces induced by flagellar motion. We used an optical tweezers to study chemotaxis by observing the force response of a flagellated microorganism when placed in a gradient of attractive chemical substances. This report shows such observations for Leishmania amazonensis, responsible for leishmaniasis, a serious disease. We quantified the movement of this protozoan for different gradients of glucose. We were able to observe both the strength and the directionality of the force. The characterization of the chemotaxis of these parasites can help to understand the mechanics of infection and improve the treatments employed for this disease. This methodology can be used to quantitatively study the taxis of any kind of flagellated microorganisms under concentration gradients of different chemical substances, or even other types of variable gradients such as temperature and pressure.

Fluorescent II-VI semiconductor quantum dots in living cells: nonlinear microspectroscopy in an optical tweezers system.

In this work we used a setup consisting of an optical tweezers combined with a nonlinear microspectroscopy system to perform scanning microscopy and obtain emission spectra using two photon excited (TPE) luminescence of captured single living cells labeled with core-shell fluorescent semiconductor quantum dots (QDs). The QDs were obtained via colloidal synthesis in aqueous medium with an adequate physiological resulting pH. Sodium polyphosphate was used as the stabilizing agent. The results obtained show the potential presented by this system as well as by these II-VI fluorescent semiconductor quantum dots to perform spectroscopy in living trapped cells in any neighborhood and dynamically observe the cell chemical reactions in real time.

Semiconductor Fluorescent Quantum Dots: Efficient Biolabels in Cancer Diagnostics

We present and discuss results and features related to the synthesis of water-soluble semiconductor quantum dots and their application as fluorescent biomarkers in cancer diagnostics. We have prepared and applied different core-shell quantum dots, such as cadmium telluride-cadmium sulfide, CdTe-CdS, and cadmium sulfide-cadmium hydroxide, CdS/Cd(OH)(2), in living healthy and neoplastic cells and tissues samples. The CdS/Cd(OH)(2) quantum dots presented the best results, maintaining high levels of luminescence as well as high photostability in cells and tissues. Labeled tissues and cells were analyzed by their resulting fluorescence, via conventional fluorescence microscopy or via laser scanning confocal microscopy. The procedure presented in this work was shown to be efficient as a potential tool for fast and precise cancer diagnostics.

Semiconductor Quantum Dots for Biological Applications

Publisher Summary This chapter examines nanoparticles quantum dots (QDs). QDs are semiconductor three-dimensional nanoparticles, with typical dimensions ranging from nanometers to tens of nanometers. A QD is often described as an artificial atom because the electron is dimensionally confined just like in a real atom and similarly it shows only discrete energy levels. The energy levels of QDs can be probed by optical spectroscopy techniques as well as in atoms. In other words, it is possible to excite these semiconductor nanocrystals, generate optical signals, and use their optical properties. The energy spectrum of a QD can be engineered by controlling size, shape, and strength of the confinement potential. QDs of the same material, but with different sizes, can emit light of different colors. As energy is related to wavelength, this means that the optical properties of the particle can be finely tuned depending on its size.

Fluorescent II-VI semiconductor Quantum Dots: potential tools for biolabeling and diagnostic

In this work we show and discuss the results obtained by using highly luminescent colloidal hydrophilic semiconductor Quantum Dots, synthesized in aqueous medium, physiological pH and functionalized with organic compounds for precise diagnostic of breast (ductal filling carcinoma), brain (glioblastoma) and cervical cancer.

Optical tweezers for studying taxis in parasites

In this work we present a methodology to measure force strengths and directions of living parasites with an optical tweezers setup. These measurements were used to study the parasites chemotaxis in real time. We observed behavior and measured the force of: (i) Leishmania amazonensis in the presence of two glucose gradients; (ii) Trypanosoma cruzi in the vicinity of the digestive system walls, and (iii) Trypanosoma rangeli in the vicinity of salivary glands as a function of distance. Our results clearly show a chemotactic behavior in every case. This methodology can be used to study any type of taxis, such as chemotaxis, osmotaxis, thermotaxis, phototaxis, of any kind of living microorganisms. These studies can help us to understand the microorganism sensory systems and their response function to these gradients.

Simple silanization routes of CdSe and CdTe nanocrystals for biological applications

Semiconductor colloidal quantum dots have been, for the past two decades, incorporated in a wide range of applications from catalysis and optical sensors to biolabels. For this reason, simple, cheap and reproducible routes of synthesis are the main goal of many research groups around the world. They seek the production of a very stable and extremely quantum efficient nanocrystal that can afford rough changes in the external environment. Silica capping is becoming a very common tool in the quest for a stable quantum dot, because of its strong and stable structure, this material provides a great insulator to the nanocrystal from the outside. The nanocrystal surface is not chemically favorable to the deposition of the bare silica shell, what demands a bifunctional molecule that provides the linkage between the core and the shell. In this work we present a comparison between several silanization methods of thiol capped CdSe and CdTe quantum dots, showing some simplifications of the routes and an application of the quantum dots produced as fluorescent cell markers in acquisition of confocal microscopy images.

Application of colloidal semiconductor quantum dots as fluorescent labels for diagnosis of brain glial cancer

In this work we present the preparation, characterization and conjugation of colloidal core shell CdS-Cd(OH)2 quantum dots to health and cancer glial rats living cells in culture media. The particles were obtained via colloidal synthesis in aqueous medium, with final pH=7.3-7.4. Laser Scan Confocal Microscopy (LSCM) and Fluorescence Microscopy were used to evaluate fluorescence intensities and patterns of health and cancer (glioblastoma) glial cells labeled with the quantum dots in different time intervals. Health and cancer glial cells clearly differ in their fluorescence intensities and patterns. These different fluorescence intensities and patterns may be associated to differences concerning cellular membrane and metabolic features of health and cancer cells. The results obtained indicate the potential of the methodology for fast and precise cancer diagnostics.

Glicemical Analysis of Human Blood Serum Using FT-Raman: A New Approach

BACKGROUND DATA Fourier transform Raman spectroscopy (FT-Raman) is a noninvasive diagnostic tool largely applied to the analysis of biological fluids and tissues. METHODS We examined the variation of carbohydrate concentration in human blood during 180 min relative to 29 spectra of patients split into four categories: hypoglycemic, healthy, threshold, and diabetic. The main bands monitored were placed in 960, 1030, 1091, 1128, and 1205 cm(-1). These bands were respectively attributed to C-O, C-C (stretching), C-O-H and C-O-C of carbohydrates. In this study, the Raman scattering signal of the all the blood samples was collected during 360 sec. The calculated correlation coefficient (R) between the concentration of carbohydrates and the Raman intensity was 0.923. CONCLUSIONS The obtained results are reasonable according to classical biochemical analysis. Our proposed FT-Raman-based method was shown to be suitable for the monitoring of carbohydrate concentration in human blood, and presented some advantages over classical biochemical methods, such as real-time analysis, required small sample volume, and was nondestructive, and the samples did not need any previous treatment.