Banca de DEFESA: LARISSA EMENUELLE RODRIGUES DOS SANTOS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : LARISSA EMENUELLE RODRIGUES DOS SANTOS
DATE: 09/04/2021
TIME: 14:00
LOCAL: webconferência pelo Google Meet no link https://meet.google.com/hug-dpvk-itd
TITLE:

Synthesis and Characterization of a Raciometric Fluorescent Probe Based on Carbon Dots - Quantum Dots for Detection of Protamine

KEY WORDS:

Quantum dots, carbon dots, molecular fluorescence, protamine

PAGES: 72
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SUMMARY:

Carbon dots (CDs) and quantum dots (QDs) are luminescent nanoparticles (NPs) extensively applied in the field of biological sensors. In this sense, the aim of this work was to synthesize and characterize a luminescent raciometric system based on chitosan C-Dots and CdTe Q-Dots for protamine detection. The results showed that the NPs exhibited spherical morphology and an average size of 8.14 and 9.17 nm for C-Dots and Q-Dots, respectively. The UV-vis absorption spectra exhibited characteristic bands around 200 and 300 nm (π-π* and n - π * transitions, respectively) and 550 nm for C-Dots and Q-Dots, respectively. The FTIR spectrum of C-Dots showed characteristic functional groups of the precursor material, which are related to vibrational stretching of oxygenated and nitrogen groups. The photophysical properties of C-Dots, indicated an excitation wavelength dependent emission (λexc), which exhibited maximum emission in the blue at 427 nm when excited at 350 nm. For the same λexc CdTe exhibited a maximum emission in the red at 624 nm. The hybrid nanomaterial (Q-Dots/C-Dots) obtained by mixing the C-Dots and Q-Dots NPs exhibited a dual emission with components centered at 427 nm and 624 nm, which were used for the detection (ON/OFF) assays of protamine. The surface charge of the nanoparticles characterized through zeta potential (ζ) exhibited for Q-Dots (negatively charged) and C-Dots (positively charged) - 45 and + 20 eV respectively. With this the proposed method is based on a ratiometric probe (dual emission) formed by the electrostatic interaction between C-Dots and Q-Dots. The suggested mechanism is based in general on the fluorescence suppression of the probe in the presence of protamine. Based on the thermodynamic parameters and the DLS assays it is suggested that the interaction mechanism occurred preferentially by electrostatic interactions between the Q-Dots (negatively charged) and the analyte (cationic protein), forming C-Dots-Q- Dots/protamine type aggregates and generating an ON-OFF system. The results obtained from DLS in the absence and presence of different concentrations of protamine evidenced that with increasing protamine concentration, the average size distribution increased from 45.16 to 96.18 nm for the concentrations of 0.01 and 0.2 mg L-1. respectively, reinforcing the idea of aggregate formation. The proposed method was performed using a 1:2 ratio referring to 25 μL C-Dots and 50 μL of Q-Dot, in which it obtained best results at pH 7 with 50 mM sodium citrate buffer. The ionic strength of the medium had an influence on the sensitivity up to 50 mM (NaCl).  The reaction waiting time for analysis was 25 min, and both the Q-Dots-PR and C-Dots-PR systems showed photostability for up to 2 h with continuous radiation exposure. Under the optimized conditions, the system showed a linear range of 0.025-0.8 mg L-1 protamine, with a limit of detection (LOD) equivalent to 0.017 mg L-1.  The determination of protamine was performed in synthetic urine samples and showed a recovery above 98 %. 

BANKING MEMBERS:
Presidente - 1869296 - CINTYA D'ANGELES DO ESPIRITO SANTO BARBOSA
Interna - 1997465 - DANIELA SANTOS ANUNCIACAO
Interno - 1613338 - JOSUE CARINHANHA CALDAS SANTOS
Externo à Instituição - RODOLFO DE MELO MAGALHÃES SANTANA - UFBA