Effects of insecticide acephate on simple models of lipid membranes based on Langmuir films and GUVs: molecular level interactions and morphological changes

Author(s)

Luis Fernando do Carmo Morato

• Document type: Master's Dissertation
• Press: Bauru. 2021-03-01.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências. Bauru
• Defense date: 2021-01-21
• Advisor: Carlos José Leopoldo Constantino

Abstract

Acephate is one the agrochemicals most used in Brazilian crops and the first used in irregular ways registered by Anvisa. Being of organophosphorus family, this insecticide was chosen by its potential risk to the human health, mainly in the neurological system. In order to study the effects of acephate in cell membranes, mimetic systems of these structures based on lipid monolayers (Langmuir films) and bilayers (Giant Unilamellar Vesicles – GUVs and Large Unilamellar Vesicles - LUVs) were evaluated. We focused on the phospholipids DPPC, which has two saturated hydrocarbon chains and a zwitterionic head, and POPC, which differs from DPPC by an unsaturation and length in one of the aliphatic chain, but mimetics the fluid phase of cell membrane. Another four lipids which have saturated chain and shares chemical groups relative to the polar head of the phospholipids were used: DODAB (quaternary ammonium group); DHP (phosphate group); DPTAP (glycerol and choline group); and DPPA (glycerol and phosphate group). In Langmuir films experiments, only DODAB and DPTAP showed interaction with acephate, once its π-A isotherms shifted to smaller molecular areas and its morphology had alterations. PM-IRRAS spectra reveals that these effects are due the affinity between the positive head groups of DPPC, DODAB and DPTAP with acephate. Despite DPPC, POPC, DODAB and DPTAP GUVs morphology did not change in presence of acephate, DPPC, DODAB and DPTAP LUVs indicated that only cationic ones were affected in presence of the pesticide, once its size increase and the zeta potential diminish. Monolayers and bilayers of POPC does not reveal any interaction with the insecticide. However, due the affinity of acephate by positive structures, the results suggests that biological process governed by species which present those structures, if in presence of acephate, can loss its function by the action of the pesticide by electrostatic interaction. (AU)

• FAPESP's process: 18/01984-8 - Effects of acephate insecticide in simple models of lipid membrane based on Langmuir films and GUVs: molecular level interactions and morphological effects
• Grantee: Luis Fernando do Carmo Morato
• Support Opportunities: Scholarships in Brazil - Master