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■Bio-mathematics, Statistics and Nano-Technologies: Mosquito Control Strategies

12.4

Antimicrobial activity and mosquito repellency of encapsulated essential oils

221

12.5

Conclusion ................................................................

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12.1

INTRODUCTION

Essential oils (EOs) are very promising in the biomedical industry due to their anti-

septic, antibacterial, antifungal and antioxidant properties. Especially, natural plant-based

ingredients like EOs have grown in popularity as they represent an eco-friendly and

biodegradable alternative for use in antimicrobial textile finishing. However, EOs have

shown to be difficult to achieve their full potential because of the chemical volatility and

instability they possess. This makes EOs prone to deterioration and loss of compounds

when exposed to environmental factors such as oxygen, heat, light and moisture. To over-

come these challenges, microencapsulation has been used as a viable technique to preserve

the essential biological and functional characteristics of the oils. The microencapsulation

can prevent the loss of volatile oil compounds while also allow for the controlled and sus-

tained release of the essential oils, enhancing bioavailability and efficacy against pathogens

(Chouhan et al. 2017).

Biopolymers, specifically natural occurring polysaccharides like chitosan and algi-

nates, are becoming popular carriers in encapsulation processes or nanoparticle forming

processes. The deacetylated form of chitin, chitosan, has been used to protect compounds

like EOs using methods like ionic gelation (Xu and Du 2003) and spontaneous emulsifi-

cation (Wilson et al. 2010). Keawchaoon and Yoksan (2011) prepared Carvacrol-loaded

chitosan nanoparticles using a two-step method combining emulsification and ionic gela-

tion, and showed that the resulting particles effectively inhibited the growth of E. coli, S.

aureus and Bacillus cereus with an MIC of 0.257 mg/mL and MBC of 8.225, 4.113 and

2.056 mg/ml respectively. Chitosan has also been used to successfully encapsulate oregano

EO, showing a two-phase release profile of the initial burst release and followed by a slow

drug release (Hosseini et al. 2013). Sayed et al. (2017) applied a nanoemulsion encapsu-

lating neem EO on cotton fabric and reported 71.73% and 65.69% reduction of S. aureus

and E. coli after 4 washes. In addition to their antimicrobial activity, a number of EOs also

possess mosquito repellent properties. Azeem et al. (2019) reported greater than 50% re-

pellency of Aedes aegypti mosquitos by Conyza sumatrensis, Erigeron canadensis, Mentha

spicata, Parthenium hysterophorus and Tagetes minuta EOs. M. spicata EO demonstrated

complete (100%) repellency and was comparable in activity to the commercially available

mosquito repellent N,N-diethyl-3-methylbenzamide (DEET). Specos et al. (2010) reported

greater than 90% repellency for up to 21 days when cotton fabric was treated with microen-

capsulated citronella EO.

Alginates are natural polymers extracted from brown algae and have been widely used

in the form of sodium alginate to encapsulate pharmaceutical actives and EO’s such as