Efficient Encapsulation and Controlled Release of N,N-Diethyl-3-methylbenzamide (DEET) from Oil-in-Water Emulsions Stabilized by Cationic Nanocellulose and Silica Nanoparticles

Oil-in-water emulsions containing N,N-diethyl-3-methylbenzamide (DEET) were developed aiming to extend the sustained release of the active compound, by using two oppositely charged nanomaterials, namely silica nanoparticles (SiNP) and cationic cellulose nanofibrils (CCNF), as stabilizers, and a mixture of food-grade nonionic surfactants to avoid precipitation by electrostatic aggregation. The formulations were stable for more than four months at room temperature, and strongly resistant to destabilization upon centrifugal and thermal stress. The results were correlated with the effect of SiNP on strengthening the network formation of CCNF in the aqueous phase by electrostatic interactions, which increased the viscosity of the external phase and, hence, emulsion stability. There was a significant size reduction of the internal oil phase containing DEET in the presence of CCNF, which was attributed to the increased viscosity in the external aqueous phase, as well as to interfacial stabilization. The combined action of CCNF and unmodified SiNP in the stabilization of the DEET-containing oil phase significantly decreased the release rate of the active compound, compared to non-emulsified DEET. Moreover, in the emulsions containing the CCNF/SiNP mixture there was a more sustained release for the period of 6 h, demonstrating the potential of these formulations for extended protection.

为延长活性成分的持续释放时长，本研究开发了含有避蚊胺（N,N-二乙基-3-甲基苯甲酰胺，DEET）的水包油乳液体系：采用两种带相反电荷的纳米材料作为稳定剂，即二氧化硅纳米颗粒（SiNP）与阳离子纤维素纳米纤维（CCNF），并复配食品级非离子表面活性剂以避免静电聚集引发的沉淀问题。该配方在室温下可稳定存放四个月以上，且对离心与热应力引发的失稳现象具有极强抗性。研究结果表明，SiNP可通过静电作用强化水相中CCNF的网络结构形成，提升外相黏度，进而增强乳液稳定性。当体系中存在CCNF时，含DEET的内部油相粒径显著减小，这一现象可归因于外水相黏度提升与界面稳定作用。相较于未乳化的DEET，CCNF与未改性SiNP协同稳定含DEET油相的作用，显著降低了活性成分的释放速率。此外，含CCNF/SiNP复配体系的乳液在6小时内展现出更持久的释放行为，证明该配方具备长效防护应用潜力。