How does it work - Scaling Analysis and Design


The existing treatments for many septicemic agents often require large quantities of medications that must be applied over long periods of time, and often achieve only incomplete eradication, or merely growth arrest, of the pathogen. A nanorobotic device that could safely provide quick and complete eradication of bloodborne pathogens using relatively low doses of devices would be a welcome addition to the physician's therapeutic armamentarium. The following analysis assumes a bacterial target (e.g. bacteremia), although other targets are readily substituted.

The microbivore is an oblate spheroidal nanomedical device consisting of 610 billion precisely arranged structural atoms plus another 150 billion mostly gas or water molecules when fully loaded . The nanorobot measures 3.4 microns in diameter along its major axis and 2.0 microns in diameter along its minor axis, thus ensuring ready passage through even the narrowest of human capillaries (~4 microns in diameter). Its gross geometric volume of 12.1056 micron3 includes two normally empty internal materials processing chambers totaling 4 micron3 in displaced volume. The device may consume up to 200 pW of continuous power while in operation and can completely digest trapped microbes at a maximum throughput of 2 micron3 per 30-second cycle, large enough to internalize almost all relevant microbes in a single gulp. To help ensure high reliability the system presented here has tenfold redundancy in all major components, excluding only the largest passive structural elements.

During each cycle of operation, the target bacterium is bound to the surface of the microbivore via species-specific reversible binding sites. Telescoping robotic grapples emerge from silos in the device surface, establish secure anchorage to the microbe's plasma membrane, then transport the pathogen to the ingestion port at the front of the device where the cell is internalized into a morcellation chamber. After sufficient mechanical mincing, the morcellated remains are pistoned into a digestion chamber where a preprogrammed sequence of engineered enzymes are successively injected and extracted, reducing the morcellate primarily to monoresidue amino acids, mononucleotides, glycerol, free fatty acids and simple sugars, which are then harmlessly discharged into the environment through an exhaust port at the rear of the device, completing the cycle.

This "digest and discharge" protocol is conceptually similar to the internalization and digestion process practiced by natural phagocytes, but the artificial process should be much faster and cleaner. For example, it is well-known that macrophages release biologically active compounds such as muramyl peptides during bacteriophagy, whereas well-designed microbivores need only release biologically inactive effluent.


lion©2006 Robert A Gorkin III