The influence of different bioadhesive polymers on physicochemical properties of thermoresponsive emulgels containing Amazonian andiroba oil

Abstract

Emulgels are amphiphilic semi-solid that can control the delivery of drugs showing different polarities. The use of a polymeric matrix in the hydrophilic portion leads to a higher thermodynamic stability system. Emulgels composed of poloxamer 407 (P407) and a bioadhesive polymer has shown improved contact time and adhesiveness on the site of administration, which can lead to an increase in the bioavailability of drugs. This work studied the effect of three different bioadhesive polymers, namely Carbopol 974P (C974P), polycarbophil (PCB) and poly(vinyl methyl ether-alt-maleic anhydride) (PMV/MA), on physicochemical characteristics of emulsion systems containing P407 and Amazonian andiroba oil. This oil is utilized as emollient, humectant and antioxidant. A factorial design 34 was utilized, and the physicochemical stability was investigated. The mechanical textural and rheological properties of the most stable formulations were evaluated for selection of potential emulsion systems. According to the texture profile and softness analyses, the selected formulations were mainly influenced by the type and amount of bioadhesive polymer, increase of andiroba oil, and P407 content. All formulations displayed pseudoplastic flow behavior and viscoelasticity. Bioadhesion assays in ear porcine skin showed the formulations as being equally bioadhesive. Transmission electron cryomicroscopy (Cryo-TEM) analysis showed well-structured micelles, with a size < 200 nm. The use of C974P (0.20 %, w/w) and P407 (17.5 %, w/w) constitutes a good strategy to produce emulgel systems for local administration of Andiroba oil from 4 to 8 % (w/w).