Novel biphasic gels containing mixture of silicone oil and sesame oil for topical drug delivery

Abstract

Bigels or biphasic gels are semisolid formulations offering the combined advantages of both hydrogels and oleogels. They are gaining interest in food, cosmetic and pharmaceutical applications. The aim of this study was to develop a new topical dosage form for both hydrophobic and hydrophilic drugs. A novel bigel was developed with the aid of cyclopentasiloxane (silicone oil). Bacitracin zinc (B) and neomycin sulfate were selected as hydrophobic and hydrophilic model drugs, respectively. Bigels were prepared by simply mixing hydrogels and sorbitan monostearate (SMS)-sesame oil oleogels. The hydrophobic drug was loaded in oleogel while the hydrophilic drug was loaded in hydrogel. Two types of hydrogel (xanthan gum (XG) and guar gum (GG) were investigated for bacitracin zinc, whereas only guar gum was studied for neomycin sulfate. The physicochemical properties of drug loaded bigels (BXG and BGG) (microscopy, FTIR spectroscopy, rheology, and mechanical properties), drug content, in vitro drug release and antimicrobial activity were evaluated and comparisons were made with bigels containing a mixture of silicone oil and sesame oil (BXGS and BGGS). The findings showed that the properties of bacitracin loaded bigels were dependent on the type of hydrogel and composition of oleogel. Superior properties of those with silicone were reported due to strong gel formation and high drug solubility in the mixture of silicone oil and sesame oil. The superior properties were aesthetic and sensory profiles, rheological and mechanical properties, drug content, drug release, antimicrobial activity and stability. The order of drug content, drug release and antimicrobial activity were BGGS >BXGS >BGG >BXG. Although BXGS showed slightly inferior properties than BGGS, the stability of BXGS was far better and stable for 6-month storage. Similar results were demonstrated for neomycin sulfate bigels. The higher drug content, drug release, antimicrobial activity and stability were obtained with the incorporation of silicone oil. The silicone oil improved the properties of bigels, therefore, this novel bigel could be a good carrier for topical delivery of both hydrophobic and hydrophilic drugs.

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