Magnetic Navigation Control of Microagents in the Vascular Network: Challenges and Strategies for Endovascular Magnetic Navigation Control of Microscale Drug Delivery Carriers

Although navigation control has been applied in a multitude of environments, relatively little is known about the challenges and issues of navigation control in the vascular network. In an adult human, the vascular network consists of nearly 100,000 km of blood vessels, with diameters ranging from a few millimeters in the artery to just a few micrometers in the capillaries, and blood flow rates ranging from a few tens of centimeters per second to a few millimeters per second. Although vascular networks present great challenges, due to various environmental conditions, they are of special interest in medical microrobotics since they allow navigable agents to be delivered anywhere within the body. Controlled endovascular navigation would allow targeted surgical, diagnostic, and therapeutic interventions. In cancer therapy, for instance, although many of the most deadly cancers are initially located in a single region, modern therapies such as chemotherapy continue to inject excessive amounts of toxic agents thecirculate systematically throughout the vascular network. In general, only a tiny fraction of the drug reaches the treatment region [1]. Even the level of targeting achieved by agents with special coatings to enhance tumor cell specificity is far from optimal when they are injected systematically in the vascular network. Since the therapeutics do not discriminate between cancerous and healthy cells, systemic circulation of these agents must be avoided to eliminate, or at least minimize, secondary toxicity that affects healthy organs.