Release and Degradation of Microencapsulated Spinosad and Emamectin Benzoate

Preparation of a long-lasting tablet of spinosad microspheres and its residual insecticidal efficacy against the yellow fever mosquito, Aedes aegypti (Diptera: Culicidae) larvae

BACKGROUNDS

In order to provide a long-lasting formulation for spinosad (SP) targeting larval stages of Aedes aegypti (Linnaeus) and others alike, a SP tablet was developed based on microspheres, using polylactic acid as inside coating material. The microspheres were encapsulated using polyethylene glycol and 1-hexadecanol to form a sustained-release SP tablet. Micromorphology, active ingredient loading, structure identification, photolysis resistance and biological activity were evaluated in this report.

RESULTS

(i) The SP microspheres had an average particle size of 6.16 ± 2.28 μm, low adhesion and good dispersion as evaluated by scanning electron microscopy and morphology. (ii) The average active ingredient loading and encapsulation of SP microspheres were 32.80 ± 0.74% and 78.41 ± 2.22%, respectively. (iii) The chemical structure of encapsulated SP was confirmed by Fourier transform infrared and 1H-nuclear magnetic resonance. (iv) The photostability of the microspheres and the tablets were evaluated. The results showed that DT50 (time required to dissipate 50% of the mass originally present) of SP was 0.95 days in microspheres and 6.94 days in tablets. (v) The long-term insecticidal activity of SP tablets was investigated, and the tablet had a long-lasting activity against the mosquito larvae, showing 100% larval mortality for 63 days.

CONCLUSIONS

The study provided a new long-lasting formulation of SP, which displayed good efficacy in the control of Ae. aegypti larvae. © 2024 Society of Chemical Industry.

Dual targeted 2-Benzylideneindanone pendant hydroxamic acid group exhibits selective HDAC6 inhibition along with tubulin stabilization effect

Abnormal epigenetics has been recognised as an early event in tumour progression and aberrant acetylation of lysine in particular has been understood in tumorigenesis. Therefore, it has become an attractive target for anticancer drug development. However, HDAC inhibitors have limited success due to toxicity and drug resistance concerns. Present study deals with design and synthesis of bivalent indanone based HDAC6 and antitubulin ligands as anticancer agents. Two of the analogues 9 and 21 exhibited potent antiproliferative activities (IC₅₀, 0.36-3.27 µM) and high potency against HDAC 6 enzyme. Compound 21 showed high selectivity against HDAC 6 while 9 exhibited low selectivity. Both the compounds also showed microtubule stabilization effects and moderate anti-inflammatory effect. Dual targeted anticancer agents with concomitant anti-inflammatory effects will be more attractive clinical candidates in future.

Evaluation of a Spinosad Controlled-Release Formulation Based on Chitosan Carrier: Insecticidal Activity against Plutella xylostella (L.) Larvae and Dissipation Behavior in Soil

Controlled-release pesticide formulations using natural polymers as carriers are highly desirable owing to their good biocompatibility, biodegradability, and improved pesticide utilization. In this study, the application potential of our previously prepared spinosad/chitosan controlled-release suspension (SCCS) was evaluated through both toxicity and dissipation tests. A comparison with the spinosad suspension concentrate and the commercial spinosad emulsion in water showed that the insecticidal activity of SCCS against Plutella xylostella larvae displayed the best quick-acting performance as well as long-term efficacy of more than 20 days. The 48 h LC50 for a 20-day efficacy was calculated to be 29.36 mg/L. The dissipation behavior of spinosad in the spinosad/chitosan microparticles in soil was found to follow the first-order kinetics, with a relatively shorter half-life (2.1 days) than that observed for the unformulated spinosad (3.1 days). This work showed the positive effect of chitosan on spinosad in improving insecticidal activity and reducing environmental risks in soil, which provided useful information on the application potential of pesticide-carrier systems based on natural polymer materials in crop protection and food safety.

Application of Solid Dispersion Technique to Improve Solubility and Sustain Release of Emamectin Benzoate

The solid dispersion technique, which is widely used in the medical field, was applied to prepare a pesticide dosage form of emamectin benzoate (EM). The preparation, physicochemical characterization, aqueous solubility, release dynamics, photolytic degradation, bioactivity, and sustained-release effects of the prepared EM solid dispersions were studied by a solvent method, using polymer materials as the carriers. Water-soluble polyvinyl pyrrolidone (PVP) K30 and water-insoluble polyacrylic resin (PR)III were used as the carriers. The influence of various parameters, such as different EM:PVP-K30 and EM:PRIII feed ratios, solvent and container choices, rotational speed and mixing time effects on pesticide loading, and the entrapment rate of the solid dispersions were investigated. The optimal conditions for the preparation of EM-PVP-K30 solid dispersions required the use of methanol and a feed ratio between 1:1 and 1:50, along with a rotational speed and mixing time of 600 rpm and 60 min, respectively. For the preparation of EM-PRIII solid dispersions, the use of methanol and a feed ratio between 1:4 and 1:50 were required, in addition to the use of a porcelain mortar for carrying out the process. Under optimized conditions, the prepared EM-PVP-K30 solid dispersions resembled potato-like, round, and irregular structures with a jagged surface. In contrast, the EM-PRIII solid dispersions were irregular solids with a microporous surface structure. The results of X-ray powder diffraction (XRD), differential scanning calorimetry (DSC), ultraviolet (UV) spectrometry, and infrared (IR) spectrometry showed that the solid dispersions were formed by intermolecular hydrogen bonding. The solid dispersion preparation in PVP-K30 significantly improved the solubility and dissolution rate of EM, particularly the aqueous solubility, which reached a maximum of 37.5-times the EM technical solubility, when the feed ratio of 1:10 was employed to prepare the dispersion. Importantly, the wettable powder of EM-PVP-K30 solid dispersion enhanced the insecticidal activity of EM against the Plutella xylostella larvae. Furthermore, the solid dispersion preparation in PRIII afforded a significant advantage by prolonging the EM technical release in water at a pH below 7.0, especially when the PRIII content in solid dispersions was high. While the amplified toxicity of the wettable powder of EM-PRIII solid dispersions against the P. xylostella larvae showed no significant differences from that of the EM technical, the long-term toxicity under the field condition was much better than that of the commercially available EM 1.5% emulsifiable concentrate. Notably, solid dispersions with both the PVP-K30 and PRIII carriers reduced the effect of UV photolysis.

Self-Assembly of TiO2 Nanofiber-Based Microcapsules by Spontaneously Evolved Multiple Emulsions

We demonstrate hierarchical nest/crust-like colloidosomes composed of interlocked titanium dioxide (TiO₂) nanofibers using spontaneously evolved n-butanol/water/ n-butanol (B/W/B) emulsions. We find two mechanisms to produce colloidosomes from B/W/B droplets due to their mutual solubility and dewetting discrepancy. Porous TiO₂ colloidal capsules with loosely intertwined nanofibers were obtained after the dewetting of nanofiber-coated B/W/B droplets, while crustlike TiO₂ colloidosomes with a thin shell and large hollow interior are developed from amphiphilic polymer-stabilized B/W/B droplets. We further investigate the effect of experimental parameters, including the initial droplet size, the nanofiber concentration, and the water/butanol ratios in butanol phases, on the droplet-to-colloidosome evolution and resultant morphology of colloidosomes. Our simple and versatile approach for fabricating TiO₂ colloidosomes can be extended to a range of irregular colloidal particles, and the products have great potential to act as host systems in electrochemical catalysis, photothermal therapy, or filtration materials.