The growth regulator gibberellic acid (GA) has several uses in the field, improving germination, plant development, productivity, and the quality of food. This work describes the development of a nanocarrier system for GA, based on the poly(γ-glutamic acid) (γ-PGA) and chitosan (CS) polymers, Nanoparticles without GA (nano-γPGA/CS-GA) showed colloidal characteristics, with an average size of 117±9nm, PDI of 0.43±0.07, and zeta potential of -29±0.5mV. The encapsulated nanoparticles (nano-γPGA/CS-GA) presented an average size of 134±9nm, PDI of 0.35±0.05, zeta potential of 27.9±0.5mV, and 61% encapsulation. The images of nanoparticles observed by Transmission and scanning electron microscopy (TEM and SEM) showed a spherical shape of the nanoparticles. The system showed sustained release, with 58% release after 48h. Evaluation of thermal properties using DSC and TGA analyses indicated that there was an interaction between the CS and γ-PGA polymers. In tests using Phaseolus vulgaris seeds, nano-γPGA/CS-GA showed high biological activity, enhancing the rate of germination in the first day (50-70%) when compared with free GA (10-16%). Encapsulated GA was also more efficient than the free hormone in the increase of leaf area and the induction of root development (including the formation of lateral roots). These effects were not observed when seeds were treated with nano-γPGA/CS without GA. The results demonstrated the considerable potential of nano-γPGA/CS-GA for use in agriculture.
A series of commercial cyclic olefin copolymers (COC), namely, ethylene-norbornene (E-NB) and ethylene-tetracyclododecene (E-TD), were processed as thin films with thicknesses of 25 m by an extrusion process. The photodegradation of neat and formulated films with different metal stearates (Fe, Co, and Mn) was investigated using an ultraviolet (UV) light lamp (340 nm) for a period of 30 days in an accelerated weathering tester model QUV from Q-LAB according to the ASTM D 5208-01 standard practice. Changes in carbonyl index (CI) and tensile properties were used to evaluate the photodegradation of the films and other properties, such as variation by DSC, were also analyzed. The present study reveals that (E-NB) copolymers show higher sensitivity to photodegradation than (E-TD) resins, in the absence and presence of metal stearates. We also find that the Fe salt shows the highest oxidative activity.
A phenyleneethynylene polymer (here denoted pPy3E-sqS) was synthesized and characterized by UV-vis spectroscopy, fluorescence spectroscopy, and TEM, and was used for the staining of polymeric nanocapsules. The nanocapsules presented good temporal stability, without changes in shape or fluorescence, and were suitable for use in drug release systems. The mean particle size was around 430nm, the polydispersity index was below 0.2, and the zeta potential was around -13mV. The release kinetics is one of the most important factors to consider in drug delivery systems, and here it was observed that nanocapsules containing the fluorescent polymer still maintained the ability to modulate the release of the fungicides tebuconazole and carbendazim (used as model drugs) after 4days. Preliminary results indicated that staining with the fluorescent pPy3E-sqS polymer could be used as a valuable tool to track the behavior of polymeric systems in the environment. However, further studies will be needed to clarify the environmental behavior and possible toxicity.
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