Abstract:

Bile acid salts, which are regarded as anionic steroid biosurfactants, have been widely used in the preparation of novel nanomaterials owing to their special amphiphilic skeleton structure, unique physical and chemical properties, good biocompatibility, and environmental friendliness. They can participate in the supramolecular self-assembly to form ordered aggregates in solution, and can be used as a template for the preparation of micro and nanomaterials. In this manuscript, we present an overview of our research work based on the effect of bile salts on the self-assembly of micro and nanomaterials along with related research done worldwide. The first section introduces the effect of small biological molecules such as amino acids, on the aggregation behavior of bile salts, wherein the interaction between amino acids and cholate has been studied extensively. Many in vivo and in vitro studies have been carried out mainly focusing on solutions and interfaces. Second part of this manuscript summarizes the research progress on the construction of supramolecular gels based on bile salts, including amino acids, rare earth salts, Graphene Oxide (GO), and surfactants. Cholic acid sodium, sodium deoxycholic acid, and lithocholic acid sodium cholic acid salt have special steroidal parent skeleton, which is much more complicated than the alkane surfactant, enabling them to self-assemble to form gel via non-covalent interactions such as van der Waals force, hydrogen bonding, and hydrophobic effect. Also addition of small molecules and other organic/inorganic fillers can increase the mechanical strength of the gels. Last part describes the formation of micro and nanomaterials by self-assembly in presence of bile salts, especially about their interaction with dye molecules, wherein the formed complex usually has novel and ordered microstructures. The interaction between surfactants and dye molecules are mainly driven by electrostatic forces, hydrogen bonding, and van der Waals force. Dye molecules are considered to be an ideal substrate for constructing functional nanomaterials and as biosurfactant, bile salts are often used to assist in the synthesis of micro and nanomaterials. In order to get a more comprehensive and in-depth understanding of the preparation of micro and nanomaterials in presence of bile salts, this article provides a solid foundation to explore future applications. Although the participation of bile salts in supramolecular self-assembly and in the preparation of various functional nanomaterials has not been studied much, the current research focuses on the template function of bile salt and ionic self-assembly. However, the biological and physiological aspects of bile salts are low; therefore the function of bile salts still needs to be probed.

Key words: Bile salt, Self-assemly, Aggregation behavior, Gels, Micro and nano materials