Microencapsulation of pyriproxyfen using the particles from gas-saturated solutions process as a controlled-release system

The purpose of this investigation was to determine whether pyriproxyfen (PPF), a synthetic juvenile hormone analog (JHA), could be encapsulated in supercritical carbon dioxide (scCO₂) using the process particles from the gas-saturated solutions (PGSS) for a controlled-release system. The PGSS process represents a promising two-step production system especially suited for the encapsulation and controlled-release system (CRS). In contrast to traditional encapsulation methods that often involve the use of harsh organic solvents or high temperatures, the PGSS process offers a gentler approach employing scCO₂ as an alternative. The solubility of scCO₂ in polymer (poly-ϵ-caprolactone [PCL]) allowed for the formation of PPF microparticles, and the particle size distribution could be controlled by adjustment of operating pressure and temperature. The obtained particles had a mean particle size of 73.6 ± 2 μm and encapsulation efficiency of 78.8 ± 9% at 60°C and 10 MPa. Furthermore, the in vitro dissolution profiles of PPF–PCL particles showed a low-level release pattern (42.5 ± 5 ppb/d) in water, followed by zero-order kinetics indicating a high-performance CRS. Finally, the in vivo bioassay using microparticles treated water exhibited 95%–100% emergence inhibition of mosquitoes, suggesting the effectiveness of PPF–PCL particles as a mosquito control agent.