Larvicidal composite alginate hydrogel combined with a Pickering emulsion of essential oil.

Sulfonated cellulose nanocrystals (S-CNCs) can be used to encapsulate thyme white essential oil (EO) that is volatile and immiscible with water. S-CNCs form a Pickering emulsion (PE) with EOs and the micron-scale PEs are embedded in sodium alginate (SA) to form macroscale hydrogel beads. The incorporation of PEs with SA is confirmed with FTIR, XRD, SEM and confocal microscopic characterizations and the release behavior is monitored to understand the time-dependent biological activity of the EOs. The larvicidal performance of the SA-PE composite hydrogel beads is investigated with Aedes albopictus (Skuse) larvae. The larvicidal activity is higher for SA/PE hydrogel beads prepared at 0.5 % CaCl2 than 0.75 or 1.0 % CaCl2 due to their higher release rate.