Green synthesis of silver nanoparticles using tomato leaf extract and their entrapment in chitosan nanoparticles to control bacterial wilt

• Published in: Journal of the science of food and agriculture Vol. 99; no. 9; pp. 4248 - 4259
• Main Authors: Santiago, Thaís R, Bonatto, Cínthia C, Rossato, Maurício, Lopes, Cláudio A P, Lopes, Carlos A, G Mizubuti, Eduardo S, Silva, Luciano P
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-07-2019; John Wiley and Sons, Limited
• Subjects: Anti-Bacterial Agents - chemical synthesis; Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - pharmacology; antibacterial; Antibacterial activity; Bacteria; Bacterial diseases; bacterial wilt; Biocompatibility; Biodegradability; Biodegradation; Biological properties; Biopolymers; biosynthesis; Chitosan; Chitosan - chemistry; Drug Carriers - chemistry; Drug Compounding; eco‐friendly; Entrapment; Genotypes; Green Chemistry Technology - methods; green nanotechnology; Leaves; Lycopersicon esculentum - chemistry; Lycopersicon esculentum - microbiology; Nanomaterials; Nanoparticles; Nanostructures - chemistry; Nanotechnology; Optical properties; Organic chemistry; Physicochemical properties; Plant bacterial diseases; Plant diseases; Plant Diseases - microbiology; Plant extracts; Plant Extracts - chemistry; Plant Leaves - chemistry; Polydispersity; Ralstonia - drug effects; Ralstonia - growth & development; Silver; Silver - chemistry; Silver - pharmacology; Stability; Synthesis; Tomatoes; Wilt; bacterial wilt; antibacterial; eco-friendly; biosynthesis; green nanotechnology
• ISSN: 0022-5142; 1097-0010
• DOI: 10.1002/jsfa.9656

BACKGROUND
Silver nanoparticles (AgNPs), particularly those entrapped in polymeric nanosystems, have arisen as options for managing plant bacterial diseases. Among the biopolymers useful for the entrapment of AgNPs, chitosan is promising because of its low cost, good biocompatibility, antimicrobial properties and biodegradability. The present study aimed: (i) to greenly‐synthesize AgNPs using different concentrations of aqueous extract of tomato leaves followed by entrapment of AgNPs with chitosan (CH‐AgNPs); (ii) to characterize the optical, structural and biological properties of the nanosystems produced; (iii) to evaluate the antimicrobial activities of AgNPs and nanomaterials; and (iv) to assess the effectiveness of AgNPs and nanomaterials for controlling tomato bacterial wilt caused by Ralstonia solanacearum.
RESULTS
Spherical and oval AgNPs had incipient colloidal instability, although the concentration of the tomato leaf extract influenced both size (< 87 nm) and the polydispersity index. Nanomaterials (< 271 nm in size) were characterized by a highly stable matrix of chitosan containing polydisperse AgNPs. Free AgNPs and CH‐AgNPs were stable for up to 30 days, with no significant alteration in physicochemical parameters. The AgNPs and nanomaterials had antibacterial activity and decreased bacterial growth at micromolar concentrations after 48 h. Morphological changes in R. solanacearum cells were observed after treatment with CH‐AgNPs. The application of CH‐AgNPs at 256 µmol L−1 reduced the incidence of bacterial wilt in a partially resistant tomato genotype but not in the susceptible line.
CONCLUSION
Greenly‐synthesized chitosan‐derived nanomaterials containing AgNPs produced with leaf extracts from their own species appear to comprise a promising and sustainable alternative in an integrated management approach aiming to reduce the yield losses caused by bacterial wilt. © 2019 Society of Chemical Industry