γ-Polyglutamic acid/chitosan nanoparticles for the plant growth regulator gibberellic acid: Characterization and evaluation of biological activity

Abstract

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.

Evaluation of the effects of polymeric chitosan/tripolyphosphate and solid lipid nanoparticles on germination of Zea mays, Brassica rapa and Pisum sativum

“…Although not tested separately in the present study, it is known that the CS polymer is nontoxic and for this reason has considerable potential for applications in agriculture, where it can act as a biostimulant and/or reduce abiotic stress in plants, as well as increase resistance against pathogens (Pichyangkura and Chadchawan, 2015). According to this, in recent studies of our group, different CS-based nanoparticles have been shown to not impair germination and initial growth of Phaseolus vulgaris (Pereira et al, 2017a(Pereira et al, , 2017b. Regarding the acetic acid, the concentration present in the CS/TPP nanoparticles is 0.038 mM, and as described in literature the phytotoxic effects of acetic acid on seeds are observed in concentration higher than 4 mM (Tunes et al, 2012).…”

Atrazine nanoencapsulation improves pre‐emergence herbicidal activity against Bidens pilosa without enhancing long‐term residual effect on Glycine max

“…Nanocapsules without atrazine led to a slight decrease of PSII photochemistry and root dry matter of soybean plants only in the short‐term experiment. Similarly, negative effects of unloaded chitosan nanoparticles on plant growth have been already reported, being related to biofilm formation and reduced water uptake . Another important aspect is the degradation of PCL in the environment, which can result from chemical hydrolysis of ester bonds or from microorganisms that secret extracellular enzymes, such as cutinase, lipase and esterase .…”

“…Similarly, negative effects of unloaded chitosan nanoparticles on plant growth have been already reported, being related to biofilm formation and reduced water uptake. 50 Another important aspect is the degradation of PCL in the environment, which can result from chemical hydrolysis of ester bonds or from microorganisms that secret extracellular enzymes, such as cutinase, lipase and esterase. 51,52 Kah and colleagues evaluated the fate of atrazine-loaded PCL nanocapsules in two agricultural soils, demonstrating that the nanoencapsulation did not change the degradation of atrazine.…”

Chitosan-Based Agronanochemicals as a Sustainable Alternative in Crop Protection

“…Chitosan-gibberellic acid nanoparticles exhibited a 37% and 82% increase of root development and leaf area in French bean, respectively, compared to the free hormone, gibberellic acid [38]. Apart from that, more lateral roots were formed upon supplementation of chitosan-γ-polyglutamic acid-gibberellic acid nanoparticles on French bean seedlings compared to the free hormone [39], hence highlighting the benefits of the nanoparticulate systems. Chickpea seeds treated with chitosan-thiamine nanoparticles exhibited a higher germination percentage with 90% compared to the mixture of chitosan-thiamine and control (water) with 84% and 75%, respectively [40].…”