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.

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The use of nanoparticles in food packaging has been proposed on the basis that it could improve protection of foods by, for example, reducing permeation of gases, minimizing odor loss, and increasing mechanical strength and thermal stability. Consequently, the impacts of such nanoparticles on organisms and on the environment need to be investigated to ensure their safe use. In an earlier study, Moura and others (2008a) described the effect of addition of chitosan (CS) and poly(methacrylic acid) (PMAA) nanoparticles on the mechanical properties, water vapor, and oxygen permeability of hydroxypropyl methylcellulose films used in food packaging. Here, the genotoxicity of different polymeric CS/PMAA nanoparticles (size 60, 82, and 111 nm) was evaluated at different concentration levels, using the Allium cepa chromosome damage test as well as cytogenetic tests employing human lymphocyte cultures. Test substrates were exposed to solutions containing nanoparticles at polymer mass concentrations of 1.8, 18, and 180 mg/L. Results showed no evidence of DNA damage caused by the nanoparticles (no significant numerical or structural changes were observed), however the 82 and 111 nm nanoparticles reduced mitotic index values at the highest concentration tested (180 mg/L), indicating that the nanoparticles were toxic to the cells used at this concentration. In the case of the 60 nm CS/PMAA nanoparticles, no significant changes in the mitotic index were observed at the concentration levels tested, indicating that these particles were not toxic. The techniques used show promising potential for application in tests of nanoparticle safety envisaging the future use of these materials in food packaging.

The triazine class of herbicides includes the compounds ametryn, atrazine, and simazine, which are used to control weeds in plantations of crops such as maize, sorghum, and sugar cane. Despite their acceptance in agriculture, these herbicides can be dangerous to the environment, depending on their toxicity, the degree of contamination, and the duration of exposure. Controlled release systems are increasingly used to mitigate problems of toxicity and minimize environmental impacts, and can also increase herbicide efficiency. The objective of this work was to prepare poly(epsilon-caprolactone) nanocapsules containing ametryn and atrazine, and evaluate their toxicity to aquatic organisms as well as in cytogenetic tests employing human lymphocyte cultures. The PCL nanocapsules were prepared according to the interfacial deposition of pre-formed polymer method. Ecotoxicological assays were performed with the alga Pseudokirchneriella subcapitata and the microcrustacean Daphnia similis. The cytogenetic tests consisted of observing mitotic index alterations after exposing lymphocyte cell cultures to different formulations. Encapsulation of the herbicides in the nanocapsules resulted in lower toxicity to the alga and higher toxicity to the microcrustacean, compared to the herbicides alone. The cytogenetic tests showed that formulations of nanocapsules containing the herbicides were less toxic than the herbicides alone. The findings indicate the potential of the nanocapsule formulations in agricultural applications, where they could help to reduce the quantities of herbicides used as well as impacts on the environment and human health.

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