The aim of the present work was to study the main formulation variables that influence attributes of bioadhesive emulgels based on a combination of polymers, using response surface methodology (RSM). Bioadhesive products continue to gain attention in topical cutaneous administration as they allow long residence times on the application site, which is important when a long dermal action and a reduced product administration frequency are desired. A Box-Behnken design of experiments (DoE) was introduced to study the effect of formulation variables on quality attributes of the emulgels. The effects of concentration of carbomer interpolymer type A (Polym1), xanthan gum (Polym2) and mineral oil (Oil) on detachment force (Fdetch), spreadability (Spread), and phase separation by mechanical stress (PhSep) were investigated. RSM and desirability functions were applied for data analysis. Emulgels were further characterized by viscosity and extrudability measurements. Polym1 showed a positive effect on Fdetch, while the increase in concentrations of Polym2 and Oil decreased this property. Polym1 and Polym2 favored emulgel PhSep. However, their interaction effect decreased it. The combination of 0.4-0.6% of carbomer and 0.2-0.3% of gum was able to produce easy-to-spread bioadhesive emulgels with mineral oil as discontinuous phase in the presence of a low surfactant concentration. Based on the DoE results, value ranges for the variables, which could achieve for the experimental domain to get the critical quality attributes of emulgels jointly within the specification limits, were able to be identified using RSM supported by desirability functions.
Keywords: bioadhesion; emulgels; polymers; response surface methodology.