Banca de DEFESA: JANNYELY MOREIRA NERI

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : JANNYELY MOREIRA NERI
DATE: 07/04/2022
TIME: 09:00
LOCAL: videoconferência
TITLE:

FUNCTIONALIZED QUINOXALINE APPLIED TO THE SYNTHESIS OF SILVER NANOPARTICLES AND INCLUSION COMPLEX WITH β-CYCLODEXTRIN

KEY WORDS:

Quinoxaline, silver nanoparticles, cysteine, Mg², Sn²⁺, selective detection, inclusion complex, β-cyclodextrin.

PAGES: 158
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Analítica
SPECIALTY: Métodos Óticos de Análise
SUMMARY:

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 ATR-FTIR, 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.

BANKING MEMBERS:
Externa à Instituição - ANA CAROLINA DE OLIVEIRA NEVES MENEZES
Presidente - 1803692 - FABRICIO GAVA MENEZES
Interno - 1198847 - JOSE LUIS CARDOZO FONSECA
Externo à Instituição - JOSIEL BARBOSA DOMINGOS - UFSC
Externo à Instituição - VANDERLEI GAGEIRO MACHADO - UFSC