Improved antibacterial activity of topical gel-based on nanosponge carrier of cinnamon oil

Cinnamon essential oil (CEO) is a volatile oil, obtained from Cinnamomum zeylanicum has become one of the most important natural oil due to its antimicrobial activity. CEO suffers from various limitations such as instability and skin irritation. This problem has been overcome by formulating CEO-loaded nanosponges incorporated in carbopol gel with increased antimicrobial property and reduced skin irritation. The nanosponges were fabricated by solvent emulsion diffusion method and evaluated for Fourier transform infrared spectroscopy (FTIR) studies, particle size, field emission scanning electron microscopy studies (FE-SEM), in vitro dissolution studies, in vitro antibacterial studies, using agar diffusion method, in vivo antibacterial activity and skin irritation studies and stability studies. Nanosponge NS1 batch was found to be in the nanosize range. FTIR studies confirmed the absence of drug-polymer interaction. NS1 confirmed a porous structure with a uniform spherical shape using FE-SEM studies. In vitro dissolution studies of optimized NS1 revealed 80% drug release in 5 h whereas, incorporating the formulation into carbopol gel showed 100% release in 5h from G1 formulation. In vitro antibacterial study of the nanosponge (NS1 and NS3) showed remarkable antibacterial activity as seen from the zone of inhibition and gel formulation G1 also showed the highest zone of inhibition with 50±1.2 mm. NS1 and G1 were stable for 2 months under accelerated conditions and 3 months under room temperature conditions. Furthermore, the in vivo and skin irritation studies were performed with selected formulation against Staphylococcus aureus , where the results confirmed the significant antimicrobial activity with no skin irritation. Nanosponge carriers can be more therapeutically effective for essential oils which can further be incorporated into topical gels for convenient application.