22-06-2012, 05:43 PM
Microbivores
[attachment=25153]
INTRODUCTION
What would an ideal drug delivery vehicle look like? To start with, it would be targetable not just to specific tissues or organs, but to individual cellular addresses within a tissue or organ. Alternatively, it would be targetable to all individual cells within a given tissue or organ that possessed a particular characteristic (e.g., all cancer cells, or all bacterial cells of a definite species, etc.). This ideal vehicle would be biocompatible and virtually 100% reliable, with all drug molecules being delivered only to the desired target cells and none being delivered elsewhere so that unwanted side effects are eliminated. The ideal vehicle would remain under the continuous control of the supervising physician, including post-administration. Even after the vehicles had been injected into the body, the doctor would still be able to activate or inactivate them remotely, or alter their mode of action or operational parameters. Once treatment was completed, all of the vehicles could be removed intact from the body, leaving no trace of their presence. Let’s call this hypothetical ideal drug delivery vehicle a “microbivore.” Microbivores are being self-powered, computer-controlled nanorobotic systems capable of digitally precise transport, timing, and targeted delivery of pharmaceutical agents to specific cellular and intracellular destinations within the human body. Drug molecules could be purposely delivered to one cell, but not to an adjacent cell, in the same tissue. To fully appreciate the scope of this future development it is helpful to briefly review some of the background and recent history of medical nanorobotics.
MICROBIVORE:
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. Such a machine is the microbivore, an artificial mechanical phagocyte.
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 which are ~4 microns in diameter. Its gross geometric volume of 12.1056 micron includes two normally empty internal materials processing chambers totaling 4 micron in displaced volume. The nanodevice consumes 100-200 pW of continuous power while in operation and can completely digest trapped microbes at a maximum throughput of 2 micron per 30-second cycle, large enough to internalize a single microbe from virtually any major bacteremic species in a single gulp. As in previous designs, to help ensure high reliability the microbivore has tenfold redundancy in all major components, excluding only the largest passive structural elements. The microbivore has a dry mass of 12.2 picograms.
SEPTICEMIA AND BACTEREMIA:
Septicemia, also known as blood poisoning, is the presence of pathogenic microorganisms in the blood. If allowed to progress, these microorganisms can multiply and cause an overwhelming infection. Bacteremia is the presence of bacteria in the human bloodstream. Although bacterial nutrients are plentiful in blood, the healthy human bloodstream is generally considered a sterile environment. Major antimicrobial defenses include the circulating neutrophils and monocytes (white cells) capable of phagocytosis (engulfing and digesting other cells) and the supporting components of humoral immunity including complement and immunoglobulin’s.
NEED OF MICROBIVORE:
The foregoing review suggests that existing treatments for many septicemic agents often require large quantities of medications that must be applied over long period of time; 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.
COMPARISON WITH NATURAL PHAGOCYTES:
Natural phagocytic cells are 100-1000 times larger in volume than microbivores but may consume almost as much power during comparable activities. Microbe ingestion times for natural professional phagocytes can be quite rapid, often a matter of minutes, but full digestion and excretion of the target pathogen may require hours. While macrophages can ingest up to ~25% of their volume per hour, microbes can process~2000% of their volume per hour, thus are ~80 times more efficient as phagocytic agents. In other words, a given volume of white cells or macrophages could digest them.
While microbivores can fully eliminate septicemic infections in minutes to hours, natural phagocytic defenses, even aided by antibiotics, can often require weeks or months to achieve complete clearance of target bacteria from the bloodstream. Thus microbivores appear to be up to ~1000 times faster-acting than either unaided natural or antibiotic-assisted phagocytic defenses.
[attachment=25153]
INTRODUCTION
What would an ideal drug delivery vehicle look like? To start with, it would be targetable not just to specific tissues or organs, but to individual cellular addresses within a tissue or organ. Alternatively, it would be targetable to all individual cells within a given tissue or organ that possessed a particular characteristic (e.g., all cancer cells, or all bacterial cells of a definite species, etc.). This ideal vehicle would be biocompatible and virtually 100% reliable, with all drug molecules being delivered only to the desired target cells and none being delivered elsewhere so that unwanted side effects are eliminated. The ideal vehicle would remain under the continuous control of the supervising physician, including post-administration. Even after the vehicles had been injected into the body, the doctor would still be able to activate or inactivate them remotely, or alter their mode of action or operational parameters. Once treatment was completed, all of the vehicles could be removed intact from the body, leaving no trace of their presence. Let’s call this hypothetical ideal drug delivery vehicle a “microbivore.” Microbivores are being self-powered, computer-controlled nanorobotic systems capable of digitally precise transport, timing, and targeted delivery of pharmaceutical agents to specific cellular and intracellular destinations within the human body. Drug molecules could be purposely delivered to one cell, but not to an adjacent cell, in the same tissue. To fully appreciate the scope of this future development it is helpful to briefly review some of the background and recent history of medical nanorobotics.
MICROBIVORE:
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. Such a machine is the microbivore, an artificial mechanical phagocyte.
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 which are ~4 microns in diameter. Its gross geometric volume of 12.1056 micron includes two normally empty internal materials processing chambers totaling 4 micron in displaced volume. The nanodevice consumes 100-200 pW of continuous power while in operation and can completely digest trapped microbes at a maximum throughput of 2 micron per 30-second cycle, large enough to internalize a single microbe from virtually any major bacteremic species in a single gulp. As in previous designs, to help ensure high reliability the microbivore has tenfold redundancy in all major components, excluding only the largest passive structural elements. The microbivore has a dry mass of 12.2 picograms.
SEPTICEMIA AND BACTEREMIA:
Septicemia, also known as blood poisoning, is the presence of pathogenic microorganisms in the blood. If allowed to progress, these microorganisms can multiply and cause an overwhelming infection. Bacteremia is the presence of bacteria in the human bloodstream. Although bacterial nutrients are plentiful in blood, the healthy human bloodstream is generally considered a sterile environment. Major antimicrobial defenses include the circulating neutrophils and monocytes (white cells) capable of phagocytosis (engulfing and digesting other cells) and the supporting components of humoral immunity including complement and immunoglobulin’s.
NEED OF MICROBIVORE:
The foregoing review suggests that existing treatments for many septicemic agents often require large quantities of medications that must be applied over long period of time; 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.
COMPARISON WITH NATURAL PHAGOCYTES:
Natural phagocytic cells are 100-1000 times larger in volume than microbivores but may consume almost as much power during comparable activities. Microbe ingestion times for natural professional phagocytes can be quite rapid, often a matter of minutes, but full digestion and excretion of the target pathogen may require hours. While macrophages can ingest up to ~25% of their volume per hour, microbes can process~2000% of their volume per hour, thus are ~80 times more efficient as phagocytic agents. In other words, a given volume of white cells or macrophages could digest them.
While microbivores can fully eliminate septicemic infections in minutes to hours, natural phagocytic defenses, even aided by antibiotics, can often require weeks or months to achieve complete clearance of target bacteria from the bloodstream. Thus microbivores appear to be up to ~1000 times faster-acting than either unaided natural or antibiotic-assisted phagocytic defenses.