Engineering oral delivery of hydrophobic bioactives in real world scenarios

Bioactive compounds, often hydrophobic in nature tend to degrade during processing outside or inside the body with rapid clearance rates, resulting in poor bioavailability. In this review, we survey recent scientific advances in lipid-based colloidal delivery systems (conventional/nanoemulsions, Pickering emulsions, multi-layered and multiple emulsions, coated/uncoated-liposomes, natural microcapsules etc.) that have been employed to improve the bioaccessibility and/or bioavailability of hydrophobic bioactive compounds. Specifically, we use a ‘delivery to design’ approach i.e. we discuss the desired release kinetics of the bioactive compounds first. This enables us to paint a more reasonable image of the optimal microstructure sought in the gastrointestinal tract, in order to lay out the design principles for fabricating the next generation of oral delivery carriers. Finally, we outline the challenges for translation of the oral delivery vehicles that show promises in bench-top experiments and how multidisciplinary approaches might help overcoming some of those challenges.