Artificial White Blood Cells
Microbivores constitute a potentially large class of medical nanorobots intended to be deployed in human patients for a wide variety of antimicrobial therapeutic purposes, for example as a first-line response to septicemia. The analysis focuses on a relatively simple device: an intravenous (I.V.) microbivore whose primary function is to destroy microbiological pathogens found in the human bloodstream, using the "digest and discharge" protocol.
The picture at the left shows an artist's conception of a team of microbivores being used to destroy a batch of E. coli.
What is a white blood cell?
White blood cells are the most important cellular components of the immune system helping to defend the body against infectious disease and foreign materials. White blood cells are produced in red bone marrow and lymphatic tissue and are released into the blood where they are transported throughout the body. The white blood cells have a rather short life cycle, living from a few days to a few weeks. A drop of blood can contain anywhere from 7 000 to 25 000 white blood cells at a time. If an invading infection fights back and persists, that number will significantly increase. As well as in the blood, white cells are also found in large numbers in the lymphatic system, the spleen and in other body tissues.
When a foreign material or germ does appear, the white blood cells have a variety of ways by which they can attack. Some will produce protective antibodies that will overpower the germ. Others will surround and devour the bacteria or foreign particle in a process called phagocytosis. Phagocytosis literally means cell-eating and applies to endocytosis ( or the internalization of substances) when solid particles are ingested and phagocytic vesicles are formed around the particle. White blood cells and some other cell types phagocytize bacteria, cell debris and foreign particles. Phagocytosis plays an important part in the elimination of harmful substances in the body. The picture at the right shows a white blood cell using the phogocytosis process to devour bacteria.
Why use microbivores?
Microbivores could be created as artificial white blood cells or - Nanorobotic phagocytes used to patrol the bloodstream, seeking out and digesting unwanted pathogens including bacteria, viruses, or fungi. During each cycle of nanorobot operation, a target bacterium becomes bound to the surface of the bloodborne microbivore like a fly on flypaper, 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 pathogen cell is internalized into a 2 micron3 morcellation chamber. After sufficient mechanical mincing, the chopped-up remains of the cell are pistoned into a separate 2 micron3 digestion chamber where a preprogrammed sequence of 40 engineered enzymes are successively injected and extracted six times, progressively reducing the mash to amino acids, mononucleotides, simple fatty acids and sugars. These basic molecules are then harmlessly discharged back into the bloodstream through an exhaust port at the rear of the device, completing the 30-second digestion cycle. No matter that a bacterium has acquired multiple drug resistance to antibiotics or to any other traditional treatment – the microbivore will eat it anyway, achieving complete clearance of even the most severe bloodborne infections in minutes to hours rather than taking weeks to months using present-day antibiotics, using only a few cc’s of nanorobots. Hence microbivores, each 2-3 microns in size, would be up to ~1000 times faster-acting than either unaided natural or antibiotic-assisted biological phagocytic defenses. Related nanorobots could be programmed to recognize and dissolve cancer cells, or to clear circulatory obstructions in a time on the order of minutes, thus quickly rescuing the stroke patient from ischemic damage.
©2006 Robert A Gorkin III