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

Abstract

a b s t r a c tThe 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 m and 5.63 ± 0.68 m, 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.

Degradable Polyhydroxyalkanoates as Herbicide Carriers

“…Analysis of the available literature revealed that research on this concept is in its infancy. In previous studies, P(3HB/3HV) microspheres were prepared as a delivery system for the herbicides atrazine [21] and ametryne [22]. The effect of the herbicides on the morphology and size of the microspheres was characterized and the herbicide release profiles in aqueous medium were examined.…”

“…In initial experiments using the pesticides HCH and lindane, we demonstrated the potential of using degradable polyhydroxyalkanoates as a matrix for embedding these compounds to enable their targeted and controlled release to the environment [20]. Recently, the ability to prepare PHA microparticles loaded with herbicide or pesticide and viable biodegradable release systems for agrochemical purposes has been demonstrated [21][22][23]. These previous works mainly examine the compound release kinetics in vitro.…”

Microspheres prepared with biodegradable PHBV and PLA polymers as prolonged-release system for ibuprofen: in vitro drug release and in vivo evaluation

“…In contrast, the microspheres prepared with PHBV had a rough and porous polymeric matrix, especially those prepared only with this polymer (formulation A). According to the literature, roughness and porosity are common characteristics of microparticles prepared with PHBV (Grillo et al, 2011). After the incorporation of ibuprofen, it was possible to observe drug crystals on the microsphere surfaces, especially in the case of formulations C and D (Figure 2).…”

Formulation and Evaluation of Isorhamnetin Loaded Poly Lactic-Co-Glycolic Acid Nanoparticles

“…The IR-PLGA NPs were mounted on metal stubs using double-sided tape and coated with a 150 Å layer of gold under vacuum. Stubs were visualized under scanning electron microscope [31].…”