No abstract

Nanotechnology is an emerging science with a wide array of applications involving the synthesis and manipulation of materials with dimensions in the range of 1–100 nm. Nanotechnological applications include diverse fields such as pharmaceuticals, medicine, the environment, food processing and agriculture. Regarding the latter, applications are mainly focused on plant growth and crop protection against plagues and diseases. In recent years, the biogenic reduction of elements such as Ag, Au, Cu, Cd, Al, Se, Zn, Ce, Ti and Fe with plant extracts has become one of the most accepted techniques for obtaining nanoparticles (NPs), as it is considered an ecological and cost‐effective process without the use of chemical contaminants. The objective of this work was to review NPs synthesized by green chemistry using vegetable extracts, as well as their use as antimicrobial agents against phytopathogenic fungi and bacteria. Given the need for alternatives to control and integrate management of phytopathogens, this review is relevant to agriculture, although this technology is barely exploited in this field. © 2020 Society of Chemical Industry

BACKGROUND: Hydrogels are materials with great potential in agricultural applications. Biodegradable hydrogels are used as preparations, for example to increase the substratum water capacity, and improve soil structure or agrochemical-controlled release. This work aimed to develop biodegradable hydrogels based on chitosan, gelatin and polyvinyl alcohol (PVA) for releasing inulin isolated from Dahlia tubers to induce protection in chili plants against Phytophthora capsici. The hydrogels were characterized by water absorption capacity, Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and stereomicroscopy microscopy, and degradation capacity using the soil burial test with sterile and inoculated soil. RESULTS: This work demonstrated the ability of a fabrication process in the preparation of gelatin-chitosan-PVA hydrogelsfor potential agricultural applications. The hydrogels showed a dense, tridimensional, interconnected and reticulated structure that was more evident in the hydrogel loaded with inulin. The hydrogels showed a water absorption capacity of ≤12 times its mass. FTIR and light microscopy demonstrated that the hydrogels were biodegradable. The percentage of degradation of hydrogels in inoculated soil was higher than in sterile soil using the soil burial test. Hydrogel loaded with inulin was found to be capable of inducing resistance in chili plants against Phytophthora capsici. CONCLUSION:The hydrogels prepared for the described methodology have great potential for use in the agricultural sector as a reservoir for agrochemicals and inductors in plant resistance treatments. Furthermore, the hydrogels were proven to be biodegradable, offering a promising tool in crop protection. Surface morphology of hydrogelsThe hydrogels have a polyhedral irregular shape. Figure 5(a) shows that the surface morphologies of the hydrogels revealed the formation of a reticulate heterogeneous network. When the hydrogel was loaded with inulin and freeze-dried again, inulin aggregates between the macro channels of the structure [Fig. 5(b)]. Biodegradation test of the hydrogelThe degradation of the hydrogels (H and HI), that were buried in the sterile and inoculated soil were monitored after 7, 14, J Chem Technol Biotechnol 2019; 94: 3495-3504

The use of selenium nanoparticles (SeNPs) in the biomedical area has been increasing as an alternative to the growing bacterial resistance to antibiotics. In this research, SeNPs were synthesized by green synthesis using ascorbic acid (AsAc) as a reducing agent and methanolic extract of Calendula officinalis L. flowers as a stabilizer. Characterization of SeNPs was performed by UV-vis spectrophotometry, infrared spectrophotometry (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) techniques. SeNPs of 40–60 nm and spherical morphologies were obtained. The antibacterial activity of marigold extracts and fractions was evaluated by disk diffusion methodology. The evaluation of SeNPs at different incubation times was performed through the colony-forming unit (CFU) count, in both cases against Serratia marcescens, Enterobacter cloacae, and Alcaligenes faecalis bacteria. Partial antibacterial activity was observed with methanolic extracts of marigold leaves and flowers and total inhibition with SeNPs from 2 h for S. marcescens, 1 h for E. cloacae, and 30 min for A. faecalis. In addition, SeNPs were found to exhibit antioxidant activity. The results indicate that SeNPs present a potentiated effect of both antimicrobial and antioxidant activity compared to the individual use of marigold extracts or sodium selenite (Na2SeO3). Their application emerges as an alternative for the control of clinical pathogens.