title: Controlled release system for ametryn using polymer microspheres: preparation, characterization and release kinetics in water.
abstract: The purpose of this work was to develop a modified release system for the herbicide ametryn by encapsulating the active substance in biodegradable polymer microparticles produced using the polymers poly(hydroxybutyrate) (PHB) or poly(hydroxybutyrate-valerate) (PHBV), in order to both improve the herbicidal action and reduce environmental toxicity. PHB or PHBV microparticles containing ametryn were prepared and the efficiencies of herbicide association and loading were evaluated, presenting similar values of approximately 40%. The microparticles were characterized by scanning electron microscopy (SEM), which showed that the average sizes of the PHB and PHBV microparticles were 5.92±0.74 μm and 5.63±0.68 μm, respectively. The ametryn release profile was modified when it was encapsulated in the microparticles, with slower and more sustained release compared to the release profile of pure ametryn. When ametryn was associated with the PHB and PHBV microparticles, the amount of herbicide released in the same period of time was significantly reduced, declining to 75% and 87%, respectively. For both types of microparticle (PHB and PHBV) the release of ametryn was by diffusion processes due to anomalous transport (governed by diffusion and relaxation of the polymer chains), which did not follow Fick's laws of diffusion. The results presented in this paper are promising, in view of the successful encapsulation of ametryn in PHB or PHBV polymer microparticles, and indications that this system may help reduce the impacts caused by the herbicide, making it an environmentally safer alternative.
authors.affiliation: Department of Environmental Engineering, Univ Estadual Paulista, Avenida Três de Março, n° 511, CEP 18087-180 Sorocaba, SP, Brazil.
authors.forename: Renato
authors.initials: R
authors.lastname: Grillo
authors.forename: Anderson do Espirito Santo
authors.initials: Ado E
authors.lastname: Pereira
authors.forename: Nathalie Ferreira Silva
authors.initials: NF
authors.lastname: de Melo
authors.forename: Raquel Martins
authors.initials: RM
authors.lastname: Porto
authors.forename: Leandro Oliveira
authors.initials: LO
authors.lastname: Feitosa
authors.forename: Paulo Sergio
authors.initials: PS
authors.lastname: Tonello
authors.forename: Newton L
authors.initials: NL
authors.lastname: Dias Filho
authors.forename: André Henrique
authors.initials: AH
authors.lastname: Rosa
authors.forename: Renata
authors.initials: R
authors.lastname: Lima
authors.forename: Leonardo Fernandes
authors.initials: LF
authors.lastname: Fraceto
mesh_terms: D000383:Agriculture; D000465:Algorithms; D019540:Area Under Curve; D003692:Delayed-Action Preparations; D004339:Drug Compounding; D006540:Herbicides / Q000737:chemistry*; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D016273:Occupational Exposure / Q000517:prevention & control; D010316:Particle Size; D011091:Polyesters / Q000737:chemistry; D011108:Polymers; D012995:Solubility; D014227:Triazines / Q000737:chemistry*; D014462:Ultrafiltration; D014867:Water; D000094122:Polyhydroxybutyrates
chemical_list: D003692:Delayed-Action Preparations; D006540:Herbicides; D011091:Polyesters; D011108:Polymers; D014227:Triazines; D014867:Water; C052620:poly(3-hydroxybutyrate)-co-(3-hydroxyvalerate); D000094122:Polyhydroxybutyrates; C107955:poly(4-hydroxybutanoate); C100057:ametryne