Interação entre quantum dots de CdTe com polieletrólitos para detecção de ácidos nucleicos: estudos preliminares

Abstract

Quantum dots (QDs) are semiconductor nanoparticles that, due to their reduced dimensions, have particular optical properties, which can be altered by modifying their size and surface. The relative ease of adjusting the material's optical properties, such as maximum absorption and emission wavelengths, makes these nanoparticles excellent candidates for a multitude of applications, especially in the biological and medicinal fields, which have been widely explored. However, in biological systems, it is necessary to evaluate different physicochemical conditions in order to verify the feasibility of using the quantum dot, such as photostability, quantum yield and, mainly, its analytical response when in the presence of the biomolecule of interest. Therefore, this work aims to synthesize and characterize QD-CdTe (cadmium telluride), with a view to quantifying ctDNA and RNA present in biological samples. The QD-CdTe were functionalized using mercaptosuccinic acid (MSA) and synthesized at different times, namely, 60 min, 180 min and 360 min. In initial studies, the variation in the analytical signal of QD-CdTe functionalized against a cationic polyelectrolyte (POLI) (polydiallyldimethylammonium chloride) was explored using spectrofluorimetry and spectrophotometry, where different behaviors between the methods could be observed, such as the increase in fluorescence and decrease in absorbance, both as a function of increasing analyte concentration. Therefore, in order to validate the results, tests were carried out with different concentrations of the polyelectrolyte, DNA and RNA, presenting a linear range between 0.0005 and 0.1% (v/v) for the polyelectrolyte and 0.2 to 40 µgmL. -1 for ctDNA and RNA for fluorescence and absorption assays. Initially the tests were carried out at pH 7, and after optimizing some parameters, it was noticed that at pH 9 the study presented better results, thus fixing this condition. Finally, after optimizing other parameters, QD-CdTe was applied to real samples using saliva for the fluorescence recovery assay.