Effect of polyherbal microemulsion on Staphylococcus epidermidis: Formulation development, CCD based optimization, characterization, and antibacterial activity by scanning electron microscopy

This research work is driven by the alarming rise in bacterial resistance due to over-prescription and irrational use of antibiotics. In this study, a combination therapy is customized using clove oil, cinnamaldehyde and berberine in a microemulsion system and its antibacterial activity was assessed against Staphylococcus epidermidis. The microemulsion was prepared using an oil mixture (clove oil and cinnamaldehyde), surfactant mixture (Tween 80 and PEG 400) and water. This polyherbal microemulsion was optimized using a central composite design. Oil(mix), S-mix, and water were selected as independent variables, whereas droplet size, PDI and viscosity were selected as dependent variables. The optimized formulation was found to be with 67.81 +/- 4.21 nm average droplet size, 0.347 +/- 0.009 PDI and 36.5 +/- 1.85 cPs viscosity. At a maximum concentration of 250 mu g/ml, the free radical scavenging activity of this optimized microemulsion was found to be 93.76 +/- 0.46%, which was comparable to ascorbic acid (94.84 +/- 2.16%). The optimized formulation was tested for its efficacy against S. epidermidis using scanning electron microscopy (SEM) which concluded its antibacterial effect on planktonic as well as biofilm-forming bacterial cells.