Controlled release system for ametryn using polymer microspheres: Preparation, characterization and release kinetics in water

Department of Environmental Engineering, Univ Estadual Paulista, Avenida Três de Março, n° 511, CEP 18087-180 Sorocaba, SP, Brazil.
Journal of hazardous materials (Impact Factor: 4.53). 02/2011; 186(2-3):1645-51. DOI: 10.1016/j.jhazmat.2010.12.044
Source: PubMed


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.

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Available from: Renata de Lima, Jul 04, 2014
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    • "A series of synthetic and natural materials have been proposed as carriers for pesticide retention and release. These carriers include synthetic polymers, such as poly(vinyl alcohol) (Hartmann et al., 1985; Alemzadeh and Vossoughi, 2002), polylactic acid (Taki et al., 2001), and poly(hydroxybutyrate) (Grillo et al., 2011), and some natural organic compounds, such as starch (Cao et al., 2005), ethylcellulose (Sopena et al., 2005), alginate (Isiklan, 2006), and chitosan (Yi et al., 2011). "
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    ABSTRACT: Nanosized tubular halloysite (Hal) and platy kaolinite (Kaol) were used as carriers for the loading and release of the herbicide amitrole (AMT). The AMT loading content in Hal was 17.5 mass% (69.9% greater than in Kaol). This result is attributed to the significant loading of AMT in the lumen of Hal. The methoxy modification of Hal and Kaol made their interlayer spaces available for the intercalation of AMT, which substantially promoted the AMT loading. The AMT loading content in methoxy-modified Hal was 30.5 mass%, corresponding to 27.9% intercalated AMT and 72.1% non-intercalated AMT. The AMT loading content in methoxy-modified Kaol was 20.8 mass%, corresponding to 47.6% intercalated AMT and 52.4% non-intercalated AMT. The release profiles of the AMT fit with the modified Korsmeyer–Peppas model. The methoxy-modified Kaol exhibited a slow release of AMT, which resulted from two factors: (i) the high proportion of intercalated AMT, the diffusion of which was restricted by the lamellar structure of the methoxy-modified Kaol, and (ii) the long diffusion path of intercalated AMT because of the large size of Kaol particles in comparison with Hal particles.
    Full-text · Article · Sep 2015 · Applied Clay Science
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    • "Poly(3-hydroxybutirate) (PHB) and its copolymers with hydroxyvalerate (HV) are the most studied PHAs in literature [8]. PHB and PHBHV are completely biodegradable and produced by a variety of bacteria´s fermentation, [1] degrading throughout natural biological processes, turning them into excellent candidates for bioactive molecules release system´s production [9] [10] [11] [12] [13] [14] [15]. Both poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvaler‐ ate) (PHBHV) are biodegradable thermoplastic polyesters produced by a bacteria known as Ralstonia eutropha or Alcaligenes latus [16]. "

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    • "From the calculated RE values (Table 1), it can be seen that the formulations prepared using 0 and 40 lg/mL of chitosan presented similar release profiles, with both systems retarding the release of ATZ by around 43 % over the trial period. RE values between 75 and 87 % have been reported in the literature for polymeric microparticles containing ametryn (Grillo et al. 2011), which are of similar order as the values obtained here for the polymeric NC. "
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    ABSTRACT: Polymeric nanoparticles can be used as carrier systems for a variety of bioactive compounds, altering the physico-chemical properties of the substances that are incorporated in the particle matrix. Coating techniques are employed to modify the interactions of the particles with the target medium. The objective of this work was to prepare nanocapsules of poly(epsilon-caprolactone) containing the herbicide atrazine and study the effect of coating the nanocapsule surfaces using different concentrations of chitosan. The encapsulation efficiency, release kinetics profile, and physico-chemical stability of the formulations were evaluated. Encapsulation percentages of 64-84 % were achieved. The release kinetics profile of the herbicide was altered when the nanocapsules were coated, and the release mechanism could be described by a combination of diffusion and relaxation of the polymeric chains. The stability of the formulations was influenced by the concentration of chitosan used in the preparation procedure. Given the global application of herbicides in agriculture, the results indicate that their association with coated modified release carrier systems could be beneficial from both ecological and economic perspectives. These systems offer delivery that is more efficient, as well as improved adhesion of herbicides to the target plants.
    Full-text · Article · Sep 2013 · International journal of Environmental Science and Technology
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