doctoralThesis
Quinoxalina funcionalizada: síntese de nanopartículas de prata como sensor de múltiplos analitos em meio aquoso e complexo de inclusão com β-ciclodextrina como um sistema de veiculação de fármacos em potencial
Fecha
2022-03-21Registro en:
NERI, Jannyely Moreira. Quinoxalina funcionalizada: síntese de nanopartículas de prata como sensor de múltiplos analitos em meio aquoso e complexo de inclusão com β-ciclodextrina como um sistema de veiculação de fármacos em potencial. 2022. 158f. Tese (Doutorado em Química) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2022.
Autor
Neri, Jannyely Moreira
Resumen
Quinoxalines, belonging to the class of nitrogenated heterocycles, have applications in
biological and technological areas, in addition to versatility when it comes to organic synthesis.
They are also present in chromogenic chemical sensors, which are defined as optical devices
for detection of analytes of interest, whose development has been stimulated in recent decades
because of the ease of use, low costs, and high selectivity and sensitivity, even in complex
samples. Recently, the use of silver nanoparticles as chemosensors has brought new
possibilities for the growth of this area. Metal cations and amino acids are important analytes
explored in the development of selective synthetic probes, especially because of their roles in
biological processes and environmental issues. The present work describes the synthesis of
silver nanoparticles (AgNPs) functionalized with the derivative 2,3-diethanolaminoquinoxaline
(DEQX) via a low environmental impact synthetic route. The QX-AgNPs system was
characterized by spectroscopy in the ultraviolet-visible (UV-vis) and infrared (ATR-FTIR)
region, as well as by transmission electron microscopy (MET), and then applied as a
chromogenic probe for selective detection of L-cysteine, as well as Mg2+ and Sn2+ in aqueous
solution. Qx-AgNPs were able to selectively detect cysteine and Mg2+ in alkaline medium
among various amino acids and metal cations, respectively. On the other hand, QX-AgNPs
were effective in detecting Sn2+ at pH 7.5. The selective detection of the analytes and the
respective mechanisms were adequately discussed based on UV-vis, MET and ATR-FTIR
analyses. The detection limits reached 2.7 nmol L-1
, 15 nmoL L-1
and 18 nmoL L-1
for cysteine,
Mg2+ and Sn2+, respectively. These limits were ratified as the success of quantification of
cysteine in urine and Mg2+ in tap water by Qx-AgNPs. Moreover, in view of the low water
solubility of DEQX and promising anticancer activity it has shown in recent works, the present
work also reports the obtainment of inclusion complexes of DEQX with β-cyclodextrin (βCD)
(DEQX/βCD), a useful excipient in a wide field of applications, obtained by physical mixing
(PM) and kneading (KND) methods, with the aim of improving the physicochemical properties
of said quinoxalin derivative. The DEQX/βCD complex was properly characterized by ATRFTIR, nuclear magnetic resonance (NMR), X-ray diffractometry (XRD), scanning electron
microscopy (SEM), as well as thermal analyses thermogravimetry (TG) and differential
scanning calorimetry (DSC). Phase solubility indicated that the solubility of DEQX increased
with increasing concentrations of βCD, that the DEQX/βCD complex is formed with 1:1
stoichiometry, and the inclusion trend of DEQX with βCD was adequate. In addition, the stable three-dimensional structure obtained with the molecular dynamics simulation method showed
insertion of DEQX into the cavity of βCD. The obtained inclusion complexes were also
evaluated against cytotoxic properties in human erythrocytes by hemolytic test, which showed
that both DEQX and its inclusion complexes with βCD, obtained by PM and KND were found
to be non-toxic. Therefore, the results obtained show the potential of DEQX for applications of
extreme relevance, indicating an important contribution to the area of nanosensors for multiple
detection of analytes in aqueous media, as well as for future advances in anticancer tests, after
evidence of association with βCD.