Microencapsulation and controlled release of insect repellent geraniol in gelatin/gum arabic microcapsules

Microencapsulation is a promising method for controlling and prolonging the release of safer, bio-based insect repellents, which can be used for protection against many vector-borne endemic diseases. Geraniol is an effective insect repellent; however, its encapsulation in gelatin/gum arabic, and its long-term retention have not been studied to date. In this study, complex coacervation was used to obtain novel geraniol-containing microcapsules using gelatin/gum arabic. The effect of processing conditions on the size and morphology of the microcapsules and the subsequent release properties was investigated. Optimal conditions included a coacervation pH of 4.45 and a crosslinking pH of 6.0. Lower mixing rates produced single core capsules with larger particle size (93 µm). Higher mixing rates resulted in multi-core capsules with smaller average particle sizes (34 µm). The geraniol contents of microcapsules were found to be 90%, 68%, and 73% for mixing rates of 700 RPM, 1000 RPM, and 1300 RPM, respectively. Microcapsule formulations showed excellent release profiles into humid air without any burst release, with retentions of 80%, 74%, and 76% at 26 days for mixing rates 700 RPM, 1000 RPM, and 1300 RPM, respectively. Encapsulation of geraniol results in longer-lasting retention compared to similar systems; hence it can be used as textile coatings for use in insect repellent clothing or incorporated into various carrier solutions for application as an area treatment. Our research highlights the possibility of tuning diffusion characteristics based on microcapsule morphology opening new applications for this technique.