The emerging role of bile acids as critical components in nanotechnology and bioengineering: Pharmacology, formulation optimizers and hydrogel-biomaterial applications.

The role of endogenous bile acids as lipid stabilizers aiding uptake of lipophilic nutrients via micelle formation and saponification effects is well documented and precedes their growing applications in pharmaceutical sciences. Their utility stems from their unique physico-chemical profile and ability to modulate immune cell signalling pathways. It has been shown that bile acids alter specific receptor-mediated pathways of cellular respiration and metabolism, providing potential clinical therapies for cardio-metabolic disorders such as diabetes mellitus, hypercholesterolemia, and heart disease. Additionally, some bile acids exert profound anti-oxidant, anti-inflammatory and immunosuppressant properties, and are effective at reducing blood pressure and alleviating hypertension. Their unique amphoteric properties and proven ability as permeability enhancers make them a desirable pharmaceutical excipient. When incorporated with various carbohydrates, polymers, hydrogels and/or polyelectrolytes to form micro- or nano-capsules, they provide enhanced thermodynamic, osmotic and structural stability, and cater for controlled delivery via specific tissue targeting, pH dependant release and temperature guided sol-gel complexation. Additionally, due to their immunosuppressant properties, they enhance the immunogenicity of encapsulated cells, increasing the feasibility of bioartificial organs as transplantable therapeutics. This review explores existing and future applications of bile acids and provides a synopsis of their role in advanced, novel therapeutic delivery systems.