Characterisation of silver nanoparticles synthesised by Bacillus thuringiensis as a nanobiopesticide for insect pest control

ABSTRACT

Nanotechnology has become one of the most promising new approaches for pest control in recent years. In this research, biocompatible silver nanoparticles (Btk-AgNPs) were synthesised by using the entomopathogenic bacterium, Bacillus thuringiensis kurstaki (Btk) as a low-cost and eco-friendly production system. The AgNP samples exhibited a brownish-yellow colour that is characteristic for silver nanoparticles synthesis. Btk-synthesised AgNPs were produced using both the supernatant and pellet of Bt culture at various concentrations and AgNP particles were characterised by UV-Vis spectrophotometer and Dynamic Light Scattering (DLS). The variation of hydrodynamic diameter (D_h) and UV-Vis spectra of silver particles produced by various concentration of culture showed that production of AgNPs was maximised when using 20% for either supernatant or pellet treatments of Bt of culture and the size of particles was around 85 nm for both. The insecticidal efficacy of Btk-synthesised AgNPs against larvae of the cabbage looper, Trichoplusia ni (Hübner) and black cutworm, Agrotis ipsilon (Hufnagel) was tested. Results demonstrated that the treatments of either Btk-synthesised AgNP(s) made with Bt supernatant or Btk-synthesised AgNP(p) using Bt pellet were found to be significantly more virulent toward larvae of T. ni than to A. ipsilon.

KEYWORDS:

• Nanotechnology
• nanopesticide
• silver nanoparticles
• Bacillus thuringiensis

Acknowledgments

The authors thank Erica Goett for continual maintenance of the insect colony used for this research. The authors are grateful to Crop Bioprotection Research Unit and Plant Polymer Research Unit, NCAUR, ARS, USDA for providing necessary facilities to carry out this study.

Disclosure statement

Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. USDA is an equal opportunity provider and employer. Also, the authors have declared that no conflict of interest exists.

Additional information

Funding

This cooperative research was made possible by United States Department of Agriculture (USDA), Agricultural Research Service (ARS) and Ministry of State for Scientific Research, Science and Technology Development Fund (STDF), Short Term Fellowship that contracted with Agricultural Research Center (ARC), Plant Protection Research Institute (PPRI).