Banca de QUALIFICAÇÃO: BRUNA MOREIRA FREIRE

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : BRUNA MOREIRA FREIRE
DATA : 03/05/2022
HORA: 08:00
LOCAL: Santo André (virtual)
TÍTULO:

Evaluation of the use of selenium nanoparticles for biofortification of rice grains

PÁGINAS: 32
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Analítica
ESPECIALIDADE: Análise de Traços e Química Ambiental
RESUMO:

Se is an essential element for humans, which has several important functions in the body.
Still, it is present in low concentrations in most foods. There is evidence of Se deficiency
among the Brazilian population. Biofortification of food crops with Se is a relatively
cheap and safe alternative to combat this deficiency. In this sense, Se nanoparticles
(SeNPs) emerge as a possible alternative for biofortification, as they combine the benefits
of Se and a lower toxicity when compared to other chemical forms of this element. In this
study, SeNPs were synthesized using ascorbic acid as reducing agent and polyvinyl
alcohol (PVA) or chitosan (CS) as stabilizers. UV-vis spectrophotometry confirmed the
formation of SeNPs by identifying the absorption band at 264 nm. The SeNPs stabilized
with PVA were selected for the further studies based on the smallest hydrodynamic
diameter and polydispersity index obtained by DLS. The transmission and scanning
electron microscopy techniques indicated that the SeNPs have a spherical shape and mean
diameter of 50.1±5.6 nm, in addition to confirming the presence of Se as the major
component in the particles. To determine the total concentration of Se by ICP-MS, several
isotopes were evaluated plus the use of He as collision gas, which was effective in
minimizing interferences. For sizing the SeNPs by spICP-MS, He and H2 were evaluated
as collision/reaction gases, and the second one showed promising results, providing an
average diameter of 48 nm for the SeNPs, in agreement with the results obtained by TEM.
SeNPs showed bacteriostatic activity against three strains of Gram positive bacteria, in
addition to bactericidal activity against S. aureus. Germination and sterilization tests were
carried out with rice seeds, in which sterilization proved to be effective for controlling
the proliferation of fungi. Tests to evaluate the toxicity of SeNPs in rice seeds were
performed, and the concentration of 0.5 mg L-1
of SeNPs was defined as the optimal
concentration, as it resulted in an increase in the activity of antioxidant enzymes and a
decrease in the concentration of reactive oxygen species, without affecting the agronomic
parameters of the plant.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 2046361 - BRUNO LEMOS BATISTA
Membro Titular - Examinador(a) Externo à Instituição - DANIEL LAZARO GALLINDO BORGES - UFSC
Membro Titular - Examinador(a) Externo à Instituição - LEONARDO FERNANDES FRACETO - UNESP
Membro Suplente - Examinador(a) Interno ao Programa - 1844792 - AMEDEA BAROZZI SEABRA
Membro Suplente - Examinador(a) Externo à Instituição - FERNANDA POLLO PANIZ