Chitosan nanoparticles as carrier systems for the plant growth hormone gibberellic acid

This work concerns the development of nanocarriers composed of alginate/chitosan (ALG/CS) and chitosan/tripolyphosphate (CS/TPP) for the plant growth regulator gibberellic acid (GA3). ALG/CS nanoparticles with and without GA3 presented mean size of 450 ± 10 nm, polydispersity index (PDI) of 0.3, zeta potential of −29 ± 0.5 mV, concentrations of 1.52 × 1011 and 1.92 × 1011 nanoparticles mL−1, respectively, and 100% encapsulation efficiency. CS/TPP nanoparticles with and without GA3 presented mean size of 195 ± 1 nm, PDI of 0.3, zeta potential of +27 ± 3 mV, concentrations of 1.92 × 1012 and 3.54 × 1012 nanoparticles mL−1, respectively, and 90% encapsulation efficiency. The nanoparticles were stable during 60 days and the two systems differed in terms of the release mechanism, with the release depending on factors such as pH and temperature. Bioactivity assays using Phaseolus vulgaris showed that the ALG/CS-GA3 nanoparticles were most effective in increasing leaf area and the levels of chlorophylls and carotenoids. The systems developed showed good potential, providing greater stability and efficiency of this plant hormone in agricultural applications.