Formulation and optimization of lemon balm extract loaded azelaic acid-chitosan nanoparticles for antibacterial applications

Abstract

Herein, preparation of chitosan/azelaic acid (CsAz) nanoparticles, loaded with lemon balm extract (LBE), and optimization of the formulation by using a mathematical model is reported. The model was designed by experimental design technique (DOE) to evaluate the effect of weight ratio of chitosan to azelaic acid (Cs/Az), tripolyphosphate (TPP) concentration and LBE weight on the loading efficiency of lemon balm in the chitosan nanoparticles. Data analysis from DOE indicated that the Cs/Az ratio (p-value 0.3014) exhibited no significant effect on the loading efficiency. Meanwhile, TPP concentration (p-values 0.0021) and LBE weight (p-value <0.0001) showed dominant and significant influences on the loading efficiency, respectively. Results demonstrated that the loading efficiency decreased by increasing LBE weight and TPP concentration. The optimum formulation to get maximum value of loading efficiency was determined as 2 (wt/wt) Cs/Az, 0.10 mg/ml TPP concentration and 68.5 mg LBE weight. The antimicrobial activity of the optimum sample was evaluated on 9 different species of gram-positive/gram-negative bacteria and 1 species of fungi. Results showed that a synergistic effect was observed between azelaic acid and LBE. In some cases, such as Enterococcus faecalis (ATCC 19433), the formulated system exhibited a better performance compared with neat azelaic acid or gentamicin. Finally, it is concluded that CsAz nanoparticles could be applied as potent and green antiseptic agent.