Evaluation of baiting fipronil-loaded silica nanocapsules against termite colonies in fields

Abstract

Various pesticide nanocarriers have been developed. However, their pest-control applications remain limited in laboratories. Herein, we developed silica nanocapsules encapsulating fipronil (SNC) and their engineered form, poly(ethyleneimine)-coated SNC (SNC-PEI), based on recombinant catalytic modular protein D4S2 and used them against termite colonies Coptotermes lacteus in fields. To achieve this, an integrated biomolecular bioprocess was developed to produce D4S2 for manufacturing SNC containing fipronil with high encapsulation efficiency of approximately 97% at benign reaction conditions and at scales sufficient for the field applications. PEI coating was achieved via electrostatic interactions to yield SNC-PEI with a slower release of fipronil than SNC without coating. As a proof-of-concept, bait toxicants containing varied fipronil concentrations were formulated and exposed to nine termite mounds, aiming to prolong fipronil release hence allowing sufficient time for termites to relocate the baits into and distribute throughout the colony, and to eliminate that colony. Some baits were relocated into the mounds, but colonies were not eliminated due to several reasons. We caution others interested in producing bait toxicants to be aware of the multilevel resistance mechanisms of the Coptotermes spp. "superorganism".

Outlooks of Nanotechnology in Organic Farming Management

“…Though these chemical fertilisers enhanced and enriched the soil fertility and crop production but also caused problems like soil acidification, water, and soil salinity, disturbance of the rhizosphere or micro-biota of the soil, formation of herbicideresistant species and superweeds, invasion of alien species, and loss of biota of soil and traditional crop plants, leaching and runoff chemicals in water reservoirs which ultimately lead to the soil and water pollution [37][38] . All these problems drew huge concern among scientists and ecologists to find alternatives for chemical fertilisers and were replaced by biofertilisers [39][40] .…”

Development of Core‐Shell Nanoparticle Drug Delivery Systems Based on Biomimetic Mineralization

“…[9e] Fipronil, as a hydrophobic molecule and an insecticide, is easy to dissolve in Miglyol 812 oil due to its high solubility in the oil (i. e., 10 mg/mL). [39] In the presence of a peptide SurSi or a protein D4S2, fipronil-loaded oil was emulsified by sonication, followed by silica shell formation through biosilicification, then fipronil-loaded oil-core/silica-shell NPs were produced. The thickness of silica shell can be controlled by varying reaction time, [40] and high fipronil encapsulation efficiencies of 96.3 and 97.5 % were achieved for the shell thickness of 40 and 77 nm, respectively.…”

“…[36,41] Furthermore, the D4S2 protein can be produced using a cost-effective chromatography free approach, which made it viable for their applications in termite trials in fields. [39] Silica can also be induced by positively charged polymers (e. g., poly-l-lysine and polyethylenimine). Jakhmola et al developed a core-shell NP for drug delivery.…”

“…described fipronil‐loaded oil‐core/silica nanocapsules for sustained release . Fipronil, as a hydrophobic molecule and an insecticide, is easy to dissolve in Miglyol 812 oil due to its high solubility in the oil (i. e., 10 mg/mL) . In the presence of a peptide SurSi or a protein D4S2, fipronil‐loaded oil was emulsified by sonication, followed by silica shell formation through biosilicification, then fipronil‐loaded oil‐core/silica‐shell NPs were produced.…”

“…Moreover, the mechanical property of the silica shell can be adjusted by using silica precursors having different chemical structures, for example, triethoxyvinylsilane (TEVS) for the soft shell and TEOS for the hard shell . Furthermore, the D4S2 protein can be produced using a cost‐effective chromatography free approach, which made it viable for their applications in termite trials in fields …”