RESEARCH
With the aim of designing new Quantum Dots (QDs) based on colloidal systems for biomedical applications, we integrate the knowledge and techniques of chemistry, physics, biology, materials science and nanotechnology. Our goal is to develop fluorescent markers to improve life quality, with fast, sensitive and specific diagnostics techniques by developing bioconjugates, biosensors and bimodal systems; and fighting pathogenic microorganisms and several other diseases by developing systems to photodynamic therapy. We also have applied QDs to better comprehension of cellular mechanisms, such as membrane carbohydrates’ distribution and the traffic of receptors inside the cells. Moreover, we study how to deliver QDs using nanostructured systems (liposomes) to study intracellular processes.
The development of biosensors that allow fast, cheaper, more precise and sensitive diagnostic systems is a general objective nowadays. In our group, QDs have been used to prepare electrochemical biosensors, thus they (1) increase the electrode surface area, (2) are synthesized in a simpler and cheaper way, (3) have an active surface for conjugation with other molecules, (4) have an isotropic structure allowing their organized disposal on the electrodes, and (5) possess unique optical and semiconductor properties. Therefore, QDs have been used to improve the biosensor quality promoting a fast diagnostic of several diseases.
QDs are semiconductors nanocrystals with dimensions of 2 to 10 nm that possess unique optical properties, due to their quantum confinement, such as great photostability, fluorescence tuned with the nanoparticle size and they possess an active surface that allows the conjugation with molecules allowing specific labeling. In our group, we develop new chemical and electrochemical strategies for the preparation of quantum dots, in water, and their conjugation with biomolecules.
Magnetic resonance image (MRI) is a powerful and versatile image technique, with a high spacial resolution. Nevertheless, the study of molecular events at cellular level is limited for this technique. In order to increase de MRI contrast a high local concentration of contrast agents is required. One approach to overcome this limitation is the association of the contrast agents with nanoparticles. In this context, we are associating quantum dots and magnetic/paramagnetic structures, producing bimodal systems that can be used for optical and magnetic resonance imaging. Our systems could improve the MRI contrast and, at the same time, with biochemical specificity due to the QDs’ fluorescence.
To take full advantages of quantum dots in intracellular studies, they need be deliver freely into the cytosol. Although, its passage through the cell membrane does not occur passively, they become trapped in endocytic vesicles. The methods already described for QDs intracellular delivery have some disadvantages, are laborious methods or can damage the cells. In this context, liposomes appear as a tool to solve these drawbacks, being vesicles of lipid bilayers that can fuse with the cells releasing its contents into the cytosol. To accomplish the delivery of QDs into cells, we use fluorescent fusogenic liposomes in different kinds of cells lines.
Our group, recently have applied quantum dots to photodynamic therapy (PDT). The association between quantum dots and photosensitizers for PDT applications is based on quantum dots' energy transfer. Where, QDs could function as energy donors to photosensitizer substances or directly to molecular oxygen (3O2), generating the reactive oxygen species that promote cell damage and consequently its death. The main applications are against pathogenic microorganisms, such as some kinds of bacteria, fungus and protozoa.
QDs have been applied in biological analysis due to their unique optical properties and their versatility to be conjugated to biomolecules, such as antibodies and lectins, becoming able to label a variety of targets with specificity. The use of QDs as fluorescent probes combined to the fluorescence confocal microscopy and other spectroscopic techniques have opened new prospects and possibilities to the real time monitoring of cellular and tissue events at molecular level. Therefore, based on QDs’ properties our group has studied receptors in cancer cells and the carbohydrates expression on cells membrane of several kinds of cells and tissues. This is important to a better comprehension of some diseases, such as the cancer.
Synthesis of Quantum Dots
Cells labeling by Quantum Dots
Bimodal systems based Quantum Dots
Quantum Dots encapsulated in Liposomes
Biosensors based Quantum Dots
Quantum Dots for Photodynamic Therapy
