Deep eutectic solvents for pharmaceutical formulation and drug delivery applications

Solvents play key roles in designing drug delivery systems (DDSs). They are used as the reaction media in the preparation of DDSs and as vehicles for delivery of problematic drugs. The number of pharmaceutically acceptable solvents is limited and developing new green ones is of a great of interest. A deep eutectic solvent (DES) is a room temperature liquid composed of a mixture of hydrogen bond acceptor and hydrogen bond donor. DESs exhibit interesting physical and chemical characteristics such as low vapor pressure, non-inflammability, chemically tailorable, solvency power for a wide range of solutes, and water non-reactivity. Furthermore, they can be easily prepared from low toxicity, readily available, and inexpensive constituents. Due to these properties, DESs have attracted growing attention as green solvents in different areas of science from chemistry to material engineering and biology. In this review, after a brief introduction about DESs, we provide an overview about current advances made over the last decade in utilizing of DESs for solubilization of water insoluble drugs, transdermal drug delivery, inorganic nanoparticle synthesis, and designing polymeric and self-assembled drug carriers. This paper also discusses main challenges and limitations of DESs that should be considered before using of them.