Banca de DEFESA: ALANA GABRIELI DE SOUZA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ALANA GABRIELI DE SOUZA
DATA : 11/08/2022
HORA: 14:00
LOCAL: On line
TÍTULO:

Pickering emulsions: a new concept in antimicrobial solutions

PÁGINAS: 205
GRANDE ÁREA: Outra
ÁREA: Multidisciplinar
RESUMO:

Essential oils are natural compounds that have attracted a great deal of attention due to their excellent antibacterial, antiviral and antioxidant capacity. However, to obtain its maximum biocidal efficiency, its stabilization is necessary, avoiding its volatilization, oxidation or degradation. This work aimed to develop Pickering emulsions from three different essential oils (Ho wood – linalool, cardamom, and cinnamon), stabilized with nanocellulose. Emulsions were first prepared by varying process parameters (screening) to verify the conditions that induce greater stability to the system. The results indicated that the morphology of the nanocellulose determines the type of stabilization of the emulsion; cellulose nanocrystals (CNCs) form liquid emulsions stabilized by electrostatic interactions and cellulose nanofibers (CNFs) form a three-dimensional structure (gel) by steric stabilization. Each essential oil has a processing factor of greater impact in relation to stability, verified by Design of Experiments. Linalool is more influenced in terms of cream index and drop size by the homogenization speed, while for cardamom and cinnamon the concentration and morphology of nanocellulose, respectively, stand out. From the screening, the most stable samples were selected to evaluate the interactions and influences of nanoparticles with essential oils, considering their individual properties, such as chemical structure and polarity, study of their physicochemical, antimicrobial and antiviral properties against the SARS-CoV-2. The emulsions showed that the chemical structure of the essential oil can influence the stability of the system and surface tension through chemical bonds or interactions, with linalool showing hydrogen bonds between its hydroxyls and cellulose, while cardamom showed bonds of cellulose with α-terpineol acetate and cinnamon, due to its stable structure with the benzene ring, did not show chemical bonds. The rheology of the emulsions showed that those stabilized with CNC have Newtonian flow, while the gels with CNF have a pseudoplastic behavior resulting from the three-dimensional network formed by the cellulose nanofibers. The consistency of the gels, evaluated by the rheological models of Herschel-Bulkley and Ostwald-de-Waele, was higher for linalool > cardamom > cinnamon emulsions. Antimicrobial tests indicated that emulsification has an influence on the biocidal activity, depending on the structure of the essential oil. Cardamom decreased its antimicrobial efficiency after emulsification with CNF, reflecting the absence of Pseudomonas inhibition and a decrease in the S. aureus inhibition halo. Cinnamon emulsions showed antimicrobial activity similar to pure essential oil, indicating that the emulsification did not change the diffusivity of the essential oil or its bacteriostatic power. Initial tests of essential oils against the SARS-CoV-2 virus were carried out, with cinnamon oil taking only 5 minutes to inactivate the virus, while cardamom oil took 30 minutes and linalool oil did not show results considering the test employee. Thus, the results indicate that emulsions and their oils are potential natural active agents to be applied in disinfectants for cleaning highly contaminated surfaces, such as hospitals, pharmacies or public transport.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 1671275 - DERVAL DOS SANTOS ROSA
Membro Titular - Examinador(a) Interno ao Programa - 1760410 - JEVERSON TEODORO ARANTES JUNIOR
Membro Titular - Examinador(a) Externo ao Programa - 1997753 - LUIZ FERNANDO GRESPAN SETZ
Membro Titular - Examinador(a) Externo à Instituição - SIMONE DE FÁTIMA MEDEIROS SAMPAIO - USP
Membro Titular - Examinador(a) Externo à Instituição - DENISE FREITAS SIQUEIRA PETRI - USP
Membro Suplente - Examinador(a) Interno ao Programa - 1763443 - MARCIA APARECIDA DA SILVA SPINACE
Membro Suplente - Examinador(a) Externo à Instituição - HELIO WIEBECK - USP
Membro Suplente - Examinador(a) Externo à Instituição - DANIELLA REGINA MULINARI - UERJ