title: An environmentally safe larvicide against Aedes aegypti based on in situ gelling nanostructured surfactant systems containing an essential oil.
abstract: OBJECTIVE
  Liquid crystalline precursors, which are in situ gelling nanostructured surfactant systems, can undergo phase transition in aqueous solution and become more structured aggregates, controlling release of larvicides and acting as biotechnology alternatives for dengue control. Such systems can contain bioactive substances as Citrus sinensis essential oil (CSEO) which exhibits biological activity against Aedes aegypti (Ae. aegypti) larvae.
  
  
  METHODS
  The formulations were composed by fixed concentration of CSEO stabilized by Polyoxypropylene (5) Polyoxyethylene (20) Cetyl Ether (PPG-5 CETETH-20): oleic acid (OA) 2:1, increasing water content. The phase diagram was established and systems structure was evaluated by polarized light microscopy (PLM), small angle X-ray scattering (SAXS) and rheology. Median lethal concentration was determined against Ae. aegypti larvae.
  
  
  RESULTS
  The phase diagram exhibited four regions: liquid crystal (LC), emulsion, microemulsion (ME) and phase separation. The PLM and SAXS distinguished microemulsions, lamellar and hexagonal LC structures. Flow and oscillatory tests showed that increasing water content increases elasticity from Newtonian to non-newtonian behavior confirming the in situ gelation behavior. The larvicidal activity of formulations indicates that these nanostructured systems improved the oil solubility in aqueous medium and in addition are potential environmental larvicide against Ae. aegypti larvae.
authors.affiliation: Department of Pharmacy, Federal University of Sergipe, 49100-000 São Cristóvão, SE, Brazil.
authors.forename: S G
authors.initials: SG
authors.lastname: Ferreira
authors.affiliation: Department of Pharmacy, Federal University of Sergipe, 49100-000 São Cristóvão, SE, Brazil.
authors.forename: V S
authors.initials: VS
authors.lastname: Conceição
authors.affiliation: Department of Pharmacy, Federal University of Sergipe, 49100-000 São Cristóvão, SE, Brazil.
authors.forename: N S
authors.initials: NS
authors.lastname: Gouveia
authors.affiliation: Department of Pharmacy, Federal University of Sergipe, 49100-000 São Cristóvão, SE, Brazil.
authors.forename: G S
authors.initials: GS
authors.lastname: Santos
authors.affiliation: Department of Morphology, Federal University of Sergipe, 49100-000 São Cristóvão, SE, Brazil.
authors.forename: R L C
authors.initials: RL
authors.lastname: Santos
authors.affiliation: Department of Pharmacy, Federal University of Sergipe, 49100-000 São Cristóvão, SE, Brazil.
authors.forename: A A M
authors.initials: AA
authors.lastname: Lira
authors.affiliation: Department of Pharmacy, Federal University of Sergipe, 49100-000 São Cristóvão, SE, Brazil.
authors.forename: S C H
authors.initials: SC
authors.lastname: Cavalcanti
authors.affiliation: Department of Chemistry, Federal University of Sergipe, 49500-000 Itabaiana, SE, Brazil.
authors.forename: V H V
authors.initials: VH
authors.lastname: Sarmento
authors.affiliation: Department of Pharmacy, Federal University of Sergipe, 49100-000 São Cristóvão, SE, Brazil. Electronic address: rogeria.ufs@hotmail.com.
authors.forename: R S
authors.initials: RS
authors.lastname: Nunes
mesh_terms: D000330:Aedes / Q000187:drug effects*; D000818:Animals; D002957:Citrus; D003715:Dengue / Q000517:prevention & control*; D016503:Drug Delivery Systems; D004655:Emulsions; D005782:Gels; D006801:Humans; D007306:Insecticides / Q000737:chemistry*; D050866:Liquid Crystals / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry; D009822:Oils, Volatile / Q000737:chemistry*; D012542:Scattering, Radiation; D053838:Scattering, Small Angle; D013501:Surface-Active Agents / Q000737:chemistry*; D014783:Viscosity; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction; D014965:X-Rays
chemical_list: D004655:Emulsions; D005782:Gels; D007306:Insecticides; D009822:Oils, Volatile; D013501:Surface-Active Agents; D014867:Water
keywords: Aedes aegypti; Citrus sinensis; Dengue; In situ gelling; Liquid crystal; Microemulsion