Self-assembly and thermoreversible rheology of perfluorocarbon nanoemulsion-based gels with amphiphilic copolymers

Cellulose derivatives and natural gums as gelling agents for preparation of emulgel-based dosage forms: A brief review

Incorporation of an emulsion onto a gel base develops a drug delivery system with improved characteristics, known as emulgel, that can envelop both hydrophilic and lipophilic molecules, and therefore increase stability and penetration of topical formulations. Such a drug delivery system provides controlled drug release that has more patient compliance and higher therapeutic efficacy. Emulgel is prepared in three main stages, preparation of water-in-oil or oil-in-water emulsion, providing the gel base, and incorporation of prepared emulsion onto gel base with continuous stirring. Various materials such as different oils (e.g. sesame oil, balsam oil, and mineral oil), emulsifiers (e.g. Tween® and Span® as the non-ionic surfactant, polyvinyl alcohol), and gelling agents including cellulose derivatives such as hydroxypropyl methylcellulose (HPMC), hydroxyethylcellulose (HEC) and carboxymethyl cellulose (CMC) in different concentrations are used in emulgel preparation. The physical properties, particle size distribution, spreadability, permeation, and drug release rate are evaluated in their development and characterization. They are used in skin disorders and other diseases such as chronic anal fisher. Also, anti-acne, analgesic, and anti-inflammatory drugs have been formulated as emulgel delivery system and their effects have been studied. In this article, the subject is to review the characteristics, preparation methods, and therapeutic efficacy as well as the potential clinical use of emulgels.

Experimental Study on Physicochemical Properties of a Shear Thixotropic Polymer Gel for Lost Circulation Control

Polymer gel lost circulation control technology is a common and effective technique to control fractured lost circulation. The performance of a lost circulation control agent is the key to the success of lost circulation control techniques. In this study, rheological tests were used to study the physical and chemical properties of a shear thixotropic polymer gel system, such as anti-dilution, high temperature resistance and high salt resistance. The results showed that the shear thixotropic polymer gel system had the ability of anti-dilution, and the gel could be formed under a mixture of 3 times volume of heavy salt water and 3/7 volume white oil, and could keep the structure and morphology stable. Secondly, the gel formation time of shear thixotropic polymer gel system could be controlled and had good injection performance under the condition of 140 °C and different initiator concentrations. Meanwhile, the shear thixotropic polymer gel system had the ability of high temperature and high salt resistance, and the gel formation effect was good in salt water. When the scanning frequency was 4 Hz and the temperature was 140 °C, the storage modulus (G′) of the gel was 4700 Pa. The gel was dominated by elasticity and had excellent mechanical properties. By scanning electron microscope observation, it was found that the shear thixotropic polymer gel system had a stable three-dimensional reticular space skeleton under the condition of high salt, indicating that it had excellent ability to tolerate high salt. Therefore, the shear thixotropic polymer gel had high temperature and high salt resistance, dilution resistance and good shear responsiveness. It is believed that the results presented in this work are of importance for extending real-life applications of shear thixotropic polymer gel systems.