Banca de DEFESA: Alan Kelbis Oliveira Lima

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : Alan Kelbis Oliveira Lima
DATE: 07/03/2024
TIME: 08:30
LOCAL: Videoconfêrencia e presencial auditorio 3 do IB
TITLE:

"Phytosynthesis of silver nanoparticles (AgNPs) using aqueous extract of guarana plant parts (Paullinia cupana Kunth): study of reaction parameters, characterization, and biological activities in vitro and in vivo".

KEY WORDS:

Amazon. Paullinia cupana. Green synthesis. AgNPs. Biological activity

PAGES: 220
BIG AREA: Ciências Biológicas
AREA: Biologia Geral
SUMMARY:

The synthesis of silver nanoparticles (AgNPs) using safer routes with less impact on the environment is of great interest because it involves biocompatible methods that can increase the scale of production and is also useful because it can be used to replace potentially toxic chemical methods. Called as "green synthesis", this route uses biological organisms or parts of them which, due to the presence of their metabolites, can reduce silver ions (Ag+ ) and promoting the stabilization of colloidal silver (Ag0 ). Therefore, this study proposed the green synthesis of AgNPs using aqueous extracts of guarana (Paullinia cupana), a plant native to the Amazon, investigating factors such as (i) the part of the plant used, (ii) how the extracts were prepared (iii) when the plant material was collected and (iv) the parameters involved in the synthesis (concentration of the extract, (iv) the parameters involved in the synthesis (concentration of extract, metal salt, temperature and equipment/energy source) which may influence the physicochemical properties, as well as the biological tests to which the nanostructures were subjected. The aqueous extracts of guarana leaves and flowers were characterized in terms of their phytochemical profile, revealing the presence of phenolic acids, alkaloids, and flavonoids as the main compounds, while the biochemical tests showed higher levels of total phenols and free radical scavenging capacity in the samples prepared by decoction. Regarding the part of the plant used and evaluating seasonality, the results showed that the AgNPs with desirable characteristics had hydrodynamic diameters of between 68.5 and 107.3 nm when synthesized with extracts from the leaves of the dry period (AgNPs-PS) and the rainy period (AgNPs-PC), respectively, and from 61.4 to 78.87 nm when using the extract from the flowers (AgNPs-FL). The morphology of the AgNPs was predominantly spherical, with a negative Zeta potential for all the samples analyzed, reaching around -30 mV, which indicates good colloidal stability. The investigations carried out by changing the reaction parameters involved in the green synthesis showed modulation in the formation of AgNPs and their physicochemical characteristics, with the best yields under the conditions optimized from the concentration of 2 mg/mL of the aqueous extract and 2 mM of the metal salt, a temperature of 70 ºC and with the synthesis carried out in a water bath. In terms of bioactivities, AgNPs showed antibacterial action against Gram-positive and Gram-negative strains. The AgNPs stood out in terms of their antioxidant capacity against DPPH and ABTS radicals in a dose-dependent manner, as well as demonstrating anticancer effects by reducing the cell viability of non-melanoma skin cancer and lung cancer tumor cell lines, albeit in a non-specific manner, since these effects have also been described for non-tumor cell lines. The AgNPs also showed catalytic activity, degrading the dye methylene blue in 40 minutes and methyl orange in up to 14 minutes. In relation to the insecticide tests, the lower CL50 and CL90 values of the AgNPs confirmed their efficacy against Aedes aegypti larvae and pupae compared to the action observed with the metal salt solution at different exposure times. In short, based on these results, it is possible to infer that the aqueous extracts of Paullinia cupana were presented as a biological source for the synthesis of AgNPs, thus contributing to the development of studies related to the modulation of the final characteristics of nanostructures, as well as their applications in various areas, showing new potentials for the use of this species of Brazilian biodiversity.

COMMITTEE MEMBERS:
Externo à Instituição - GUSTAVO FRIGI PEROTTI - UFAM
Interno - 1929494 - JOAO PAULO FIGUEIRO LONGO
Externa ao Programa - 2932843 - LAISE RODRIGUES DE ANDRADE - nullPresidente - 2220195 - MONICA PEREIRA GARCIA
Externa à Instituição - PATRICIA BENTO DA SILVA - PERKINELMER