Polymeric carriers are a promising drug delivery system that are poised to treat numerous diseases, provided their abilities to control drug release and target specific parts of the body are successfully translated. The main issues preventing successful translation of polymeric carriers into the clinic includes poor vascular circulation, limited targeting and the inability to negotiate many biological barriers. Furthermore, multifunctional carriers capable of combining these functions have yet to be demonstrated. However, it is theoretically possible to design such multifunctional carriers as circulatory cells are capable of performing these same functions. During my Ph.D, I have developed three distinct blood-cell inspired drug delivery systems that improve the in vivo delivery abilities of polymeric carriers by utilizing and mimicking many of the abilities of the main individual cellular components in blood, namely: (i) erythrocytes, (ii) leukocytes and (iii) thrombocytes. The first two examples utilize a strategy known as "cellular hitchhiking", which involves the attachment of polymeric particles to the surface of circulatory cells so as to transfer innate circulatory and targeting abilities from cell to particle. The second strategy involves the design and application of synthetic platelets, dubbed platelet like nanoparticles (PLNs), which incorporate the essential biophysical (shape and flexibility) and biochemical (surface biology) parameters of natural platelets into a polymeric nanoparticle.