Bio-inspired, bioengineered and biomimetic drug delivery carriers

There are various challenges and limitations associated with the delivery of free drugs. These include poor solubility, poor stability, unwanted toxicity and/or an inability to cross cell membranes.Although there have been considerable advances in the development of synthetic drug carriers, it has emerged that natural carrier systems — such as those used by bacteria, viruses and various cells within the body — have the potential to be therapeutically exploited and may be highly effective in addressing these challenges.Several strategies have been proposed that are based on the engineering of bacteria and viruses for therapeutic functions, including recombinant bacteria for protein delivery, tumour-targeting bacteria for chemotherapeutic applications, and viral gene vectors and virus-like particles for vaccination.Pathogens such as bacteria and viruses induce diseases by evading immune responses and inducing favourable interactions with target cells, a mechanism that bears a striking resemblance to the action of many drug delivery carriers. Several synthetic carriers attempt to mimic these features to enhance their therapeutic function, especially for vaccination.Various types of cells — including red blood cells, macrophages, dendritic cells and stem cells — have been used as carriers or they have inspired the design of new carriers.Technologies that take advantage of the complex structural features that are seen in biological systems as well as precision engineering and production (as seen in synthetic carriers) have great potential for the advancement of effective drug delivery strategies.