Synthesis and characterization of thymol-loaded lauryl glycol chitosan for pesticide formulation

Thymol is a hydrophobic active ingredient and widely used as an alternative pesticide for pest control. However, due its low solubility in water, a water-soluble carrier is required in its formulation. Therefore in this study, the potential of an amphiphilic chitosan, namely lauryl glycol chitosan (LGC) as a carrier to encapsulate and release thymol was evaluated. The physical and chemical properties of LGC were characterized using Fourier Transform Infrared (FTIR) Spectrometer, Proton Nuclear Magnetic Resonance (¹H NMR) Spectrometer, UV-Visible Spectrophotometer, Thermogravimetric Analyser (TGA) and Transmission Electron Microscope (TEM). A Fluorescence Spectrometer was used to determine the critical micelle concentration (CMC) value of LGC in aqueous solution. The encapsulation efficiency of LGC for thymol was determined by using a High Performance Liquid Chromatography (HPLC). The FTIR and ¹H NMR analyses confirmed the structure of the synthesized LGC. It was noted that the addition of lauryl and glycol groups to the chitosan backbone has enhanced the solubility properties of chitosan in neutral and basic media. TEM observation confirmed that LGC could form self-aggregates in the solution with a spherical shape. The CMC value determined for LGC was 0.008 mg/mL. LGC exhibited good affinity towards thymol with an encapsulation efficiency of 58%. The findings from in vitro release study showed that the LGC could prolong the release of thymol from its micelles. Results from this study highlight that LGC possesses great characteristics to be further developed as a promising carrier in the pesticide formulation. (paper)