Mosquito repellency of carvacrol, thymol, and cinnamaldehyde nanogels against Aedes aegypti: a comparative study with DEET

Abstract

Aedes aegypti is a primary vector of arboviral diseases, including chikungunya, dengue fever, yellow fever, and Zika virus. Given the increasing global burden and the limitations of synthetic repellents, there is a growing need for safe and effective botanical alternatives, especially in endemic regions. This study formulated thymol-, carvacrol-, and cinnamaldehyde-loaded nanoemulsions via spontaneous emulsification and subsequently gelled using hydroxypropyl methylcellulose (HPMC). Viscosity and encapsulation efficiency were assessed using viscometry and Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy. The repellent efficacy of the resulting nanogels against Ae. aegypti was assessed and benchmarked against DEET (40% w/v). The nanoemulsions exhibited particle sizes of 208 ± 5 nm, 183 ± 6 nm, and 193 ± 4 nm for thymol, carvacrol, and cinnamaldehyde, respectively. Among all formulations, carvacrol-based nanogel (3% w/v) demonstrated the longest protection time (250 ± 34 min), exceeding the commercial DEET formulation (190 ± 17 min). These findings highlight the potential of HPMC-based nanogel repellents, particularly those containing carvacrol, as effective and safer botanical alternatives to conventional repellents, with promising implications for integrated vector management strategies.