Optimization of nanoencapsulation of carvacrol and thymol in chitosan polymer by response surface methodology (RSM)

The volatility of essential oils and their instability against environmental factors limit their use. However, encapsulating these compounds in polymeric nanoparticles can significantly increase their half-life and make their use possible for longer periods. Chitosan, a biodegradable polymer with controlled release and low toxicity, is one of the polymers utilized in the encapsulation of essential oils. As a result, the present study was carried out with the aim of nanoencapsulation of carvacrol and thymol in chitosan using ionic gelation method and the concentration of chitosan (0.1-0.3%), TPP concentration (0.2-0.1%) and concentration of essential oil (0.1-0.2%) as three variables. The mean particle size of chitosan nanoparticles was optimized using response surface methodology and central composite design. The size and polydispersity index (PDI) were determined by DLS, essential oil loading confirmation was evaluated by FTIR, and the spectrophotometric method was used to measure the encapsulation efficiency. Then, the results of the optimization of nanoparticle synthesis were investigated. The optimum conditions for the synthesis of chitosan-thymol nanoparticles and achieving a size of 101 nm and encapsulation efficiency of 72%, a concentration of 0.11% chitosan, 0.19% TPP and 0.14% thymol were determined. In the case of chitosan-carvacrol nanoparticles, a concentration of 0.13% chitosan, 0.19% TPP and 0.15% carvacrol resulted in the formation of nanoparticles with a size of 95 nm and an encapsulation efficiency of 65%. In general, the results demonstrated the ability of the response surface methodology to predict the particle size and PDI of chitosan nano-formulations containing carvacrol and thymol.