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Nanorobots can be applied to treat a vast number of diseases ranging from common cold to more dreadful ones such as Cancer. Nanomedicine is the study of nanorobots which is a huge prospect to new treatment tools to improve the human biological system. This article presents a brief study in the development of nanorobots and some of their applications in the field of medicine.
Richard Feynman, a Nobel Laureate, predicted the emergence of a new science called nanotechnology in 1959. Nanotechnology has the potential to create many new materials and devices with a vast range of applications, such as in medicine, electronics and energy production. Nanorobotics refers to the still largely hypothetical nanotechnology engineering discipline of designing and building nanorobots, devices ranging in size from 0.1-10 micrometers and constructed of nanoscale or molecular components .
3. Nanorobotics in Medicine; Nanomedicine
Nanomedicine is the application of nanotechnology in the field of medicine. Advances in nanotechnology will enable scientists to develop programmable and externally controlled complex machines known as nanorobots to perform various functions inside the human body at molecular level. Nanomedicine seeks to deliver a valuable set of research tools and clinically helpful devices in the near future that will allow specialists in the field of medicine to overcome the limitations of current medicine to provide better diagnostic tools and cure diseases unresponsive to conventional methods. Nanomedicine can provide better healthcare for the patients. Potential applications for nanorobotics in medicine may include early diagnosis and targeted drug delivery for diseases, biomedical instrumentation, surgery, monitoring of diabetes, and health care.
4. Architecture of a Nanomedical Robot
Nanorobots are hypothetical devices and still in development phase. Current design of nanorobots is based on those already existing in the biological system . A nanorobot should be designed by viewing the human body from a molecular standpoint . A typical medical nanorobot will probably be a micron-scale robot assembled from nanoscale parts. These parts could range in size from 1-100 nm and might be fitted together to make a working machine measuring 0.5-3 microns in diameter . A nanorobot working in a tissue could be as large as 50-100 microns whereas the one in the bloodstream needs to be 500-3000nm to allow hindrance free flow through the capillaries . Carbon will likely be the principle element comprising the bulk of a medical nanorobot due to its strength, chemical inertness and biocompatibility. Carbon can be used in the form of diamond or diamondoid/fullerene nanocomposites. Other elements such as hydrogen, sulfur, oxygen, fluorine and silicon can be used for other components . To prevent phagocytosis by body's natural immune system, it is proposed that the outer surface of the nanorobot be made with diamond and should be smooth and flawless. Experimental studies suggest that diamond being chemically inert and biocompatible provokes less leukocyte activity and fibrinogen absorption . Furthermore, the nanorobots intended for medical purposes should be non-replicating as replication could increase device complexity, reduce reliability and interfere with medical function.
4.1 Introducing the Nanorobots inside the Body
A possible way of introducing the nanorobots inside the body could be by injecting few cubic centimeters of micron-sized nanorobots suspended in fluid (probably a water/saline suspension) directly into the circulatory system .
4.2 Moving the Nanorobot around the Body
The first possibility could be to allow the nanorobot to be carried to the site of operations by means of normal blood flow. Another possibility could be to propel the nanorobot to the target site. There are a number of means available for active propulsion of a nanorobot. These include propellers, cilia/flagella, electromagnetic pump, jet pump and membrane propulsion. These devices could be incorporated in the design of a nanorobot .
4.3 Navigating & Tracking the Nanorobot
This could be achieved by presence of external sensors. Their major purpose will be twofold. The first is to determine the location of the target site. The second purpose is to gain a rough idea of where the nanorobot is in relation to that site. These external sensors could include ultrasonic, NMR/MRI, radioactive dye, X-ray and radio/microwave/heat .
4.4 Recognition of the Target Site
This can be done by internal sensors which are an integral part of the nanorobot. These sensors include chemo tactic sensors keyed to the specific known antigens on the target cells, spectroscopic sensors, TV camera and UHF sonar .
4.5 Power Supply of the Nanorobot
The nanorobot could derive its power supply from sources within the body or from the outside. Sources within the body include metabolism of local glucose and oxygen within the blood stream and body heat. External sources may include externally supplied acoustic power like microwave, ultrasonic and induced magnetic. Another possibility is for the nanorobot to carry the full amount of energy required onboard using conventional chemical batteries and high voltage capacitors [19, 20].
4.6 Means of Recovery from the Body
Some nanodevices will be able to exfuse themselves from the body via the usual human excretory channels or they can be exfused by medical personnel using aphaeresis like process or active scavenger like systems .
5. Biomedical Applications of Nanorobotics
The proposed applications of nanorobots in medicine may advance biomedical intervention with minimally invasive surgeries, improve treatment efficiency and outcome through early diagnosis of diseases ranging from common cold to the more dreadful ones like cancer. It may also help hypertensive and diabetic patients who require constant body function monitoring .
5.1 Drug Delivery Systems
The long-term objective of drug delivery systems is the ability to target selected cells and/or receptors within the body. At present, the development of new drug delivery techniques is driven by the need on the one hand to more effectively target drugs to the site of disease, to increase patient acceptability and reduce healthcare costs and on the other hand, to identify novel ways to deliver new classes of pharmaceuticals that cannot be effectively delivered by conventional means . Nanoparticles used as drug carriers can enhance the solubility and transport of drugs that are poorly soluble in blood. They can also allow drugs to be released at the target site at a controlled rate and prevent its premature degradation. As a result, the efficacy of the drug is greatly enhanced and unwanted side effects are reduced to a minimum . One of the several methods of drug delivery includes encapsulation of drugs in materials that protect them during transit in body like liposome, polymers such as lactide co-glycolide (PLGA) which are used as micro scale particles. This method protects the drug against early enzymatic or chemical degradation thus enhancing its efficacy [1, 6]. Other promising drug carriers include liposome, dendrimers, hydrogels, molecularly imprinted polymers & microelectromechanical systems (MEMS) .
Multiple & high potency drugs can be delivered accurately at the target site resulting in high concentration of the drug where it is needed and reducing its systemic concentration. This will be helpful in treating disorders like, Parkinson's, Huntington's, Alzheimer's and diseases of the eyes .
5.2 Nanorobots in Diagnosis, Treatment & Control of Diabetes
The level of glucose in blood can be observed via constant glucose monitoring using medical nanorobotics. The protein hSGLT3 which is intrinsically related to the glucose molecule helps in the maintenance of proper gastrointestinal cholinergic nerve and skeletal muscle function activity. This protein can act as a sensor to identify glucose and hence define the glucose level in a diabetic patient .
The prototype model uses a CMOS (complementary metal oxide semi-conductor) based nanorobot. For glucose monitoring the nanorobot uses embedded chemo sensor that involves the modulation of hSGLT3 protein glucosensor activity. The nanorobot being biocompatible is not attacked by the body's immune system and hence it has no interference in detecting the blood glucose level . The nanorobot features a size of ~2 micrometer which allows it to flow freely along with the red blood cells through the bloodstream detecting the blood glucose level. At a typical glucose concentration, the nanorobot tries to keep the glucose level ranging from 90- 130 mg/dl. Any deviation from the normal which varies based on the medical prescription is detected by the onboard chemical sensors. The measured data can then be transferred automatically through the RF signals to the mobile phone carried by the patient. In case of emergencies where the glucose level rises to critical levels, the nanorobot emits an alarm through the mobile phone, prompting the patient to take any further action [2, 3].
Several blood borne nanorobots will allow glucose monitoring not just at a single site but at many different locations throughout the body. The nanorobots can also be programmed to measure blood glucose at specific and desired intervals of time. Other onboard sensors can measure diagnostically relevant information such as blood pressure, early signs of tissue gangrene and changes in local metabolism that could help in assessing the course and extent of disease . The important data collected will not only help doctors to supervise and improve patient's medication and diet but also increase patient compliance by avoiding the need for frequent needle pricks and glucose sampling which will eventually resulting in a better control of glucose levels in these patients.
5.3 Nanorobots in Cancer Detection and Treatment
Current treatments for cancer like chemotherapy and radiation therapy have many major unwanted side effects including destruction of more healthy cells than cancerous ones and depression of immune system causing more distress to the patient and the doctors. Advances in nanorobotics may provide the tool for the early detection and a non-depressed therapy for cancer.
The nanorobot architecture incorporates chemo tactic sensors which are able to distinguish between malignant and healthy cells by checking their surface antigens . Another method uses chemical nanobiosensors that can detect different levels of E-Cadherin and beta-Catenin in primary and metastatic phases of cancer. This may allow early detection of cancer . Once the tumor is detected, the nanorobot can be programmed to attach to it and attract other predefined nanorobots towards it to allow intensive chemotherapeutic action with precise drug delivery at the target site .
5.4 Nanorobots for Cardiology
Applications of nanotechnology to diseases of the cardiovascular system include non-invasive diagnosis and targeted therapy of atherosclerotic plaque.
A possible feature of the nanorobot will be the capability to located atherosclerotic lesion in the stenosed vessels and treat them either mechanically, chemically or pharmacologically [7.8]. Nanorobots working in the bloodstream could nibble away at arteriosclerotic deposits, widening the effected blood vessels. Furthermore they may also help restore damaged vessel wall and lining as a result of plaque formation within the vessel. This would help in prevention of heart attacks . Vasculocytes are hypothetical nanorobots intended for use in the limited vascular repair of arteriosclerotic lesions .
5.5 Nanorobots for Fight against Llife Threatening Infections
Studies have shown how nanorobots can effectively improve health care and medical defense. Current treatment for septicemia requires large quantities of medication given over a long period of time. This often achieves only incomplete eradication or growth arrest of the pathogen .
Nanorobotic artificial hypothetical phagocytes called "microbivore" whose primary function mimics that of the natural phagocyte could safely provide quick and complete eradication of blood borne pathogens. This nanorobot works on the "digest and discharge" protocol. These nanorobots could patrol the bloodstream, identifying and digesting unwanted pathogens including bacteria, viruses or fungi. Microbivores could have the ability to achieve complete clearance of even the most severe septicemic infections in hours or less. This is far better than the weeks and months needed for antibiotic assisted natural phagocytic defenses [2, 10].
5.6 Surgical Nanorobots
Medical devices that contain Nano and micro technologies will allow surgeons to perform tasks with greater precision and safety, monitor physiological and biomechanical parameters more accurately .
Nanorobots may also allow surgeon to perform long distance tele-operated surgeries .
Surgical nanorobots are being developed to provide surgeons with unprecedented control over precision instruments. This is particularly useful for minimally invasive surgery like laparoscopic surgeries for treatment of cancer. The surgeon's movements transform large motions on the remote controls into micro-movements on the robot arms to greatly improve mechanical precision and safety .
5.7 Nanorobots as Substitute for Blood Cells
A Respirocyte is a hypothetical nanorobot that functions as an artificial red blood cell with oxygen and carbon oxide carrying capabilities that can provide tissue oxygenation in the event of impaired circulation.
A respirocyte acts a pressure tank that can be pumped with oxygen and carbon dioxide and allowed to floats freely within the blood stream. It mimics the action of a natural red blood cell but it can deliver 236 times more oxygen per unit volume than a natural red blood cell [2, 12].
These simple nanotechnological devices can be used to treat anemia, perinatal and neonatal disorders, and a variety of lung diseases and conditions. It could also prevent asphyxia and help with artificial breathing in adverse environment. Hyperbaric oxygenation by respirocytes could help treat anaerobic and aerobic infections such as clostridial myonecrosis, chronic refractory osteomyelitis, and necrotizing soft tissue infections including cutaneous ulcers, and could assist in burn recovery by reducing fluid requirement, improving microcirculation, and reducing the need for grafting .
A clottocyte is an artificial mechanical platelet that may achieve hemostasis faster than natural platelets even in significantly large wounds. Clottocytes may perform clotting function that is equivalent to that performed by biological platelets, but at only 0.01% of the bloodstream concentration of those cells or about 20 nanorobots per cubic millimeter of serum. Hence clottocytes appear to be about 10,000 times more effective as clotting agents than an equal volume of natural platelets .
The Vasculoid is a single, multisegmented nanomedical robotic system capable of duplicating all thermal and biochemical transport functions of the blood, including circulation of respiratory gases, glucose, hormones, cytokines, waste products, and cellular components. The Vasculoid system conforms to the shape of the blood vessels and may serve as a complete replacement for natural blood .
5.8 Nanorobots for Chromosome Replacement Therapy
Chromallocyte is a hypothetical cell-repair nanorobot capable of vascular surface travel into the capillary bed of the target tissue or organ. It would be capable of replacing entire chromosomes in individual cells thus permanently curing any genetic disease and even permitting cancerous cells to be reprogrammed to a healthy state. This could also correct the accumulating genetic damage and mutations that leads to aging [2, 21].
Pharmacyte is a nanorobot capable of transport, timing and targeted delivery of pharmaceutical agents to specific location within the human body. Other applications of pharmacyte in medicine may include initiation of apoptosis in cancer and direct control of cell signaling process .
6. Further Applications of Nanorobots in Medicine
Tissue repair and regeneration are other areas where nanotechnology could have great impact. For example, biodegradable nanoparticles which release appropriate growth factors and angiogenic factors could improve the bioengineering of heart or lung tissue or the production of vascular grafts to build functional tissue . Nanotechnology can offer better diagnosis and in vivo treatment of several intracranial disorders including cerebral aneurysm and neurodegenerative diseases like Parkinson's and Alzheimer's [13, 14].
Nanorobots might be used to seek and break kidney and liver stones [9, 20]. Another possible application of nanorobots could be to assist inflammatory cells to repair injured tissues faster .Nanorobots equipped with nanosensors could be helpful to deliver anti-HIV drugs . To cure skin diseases, a cream containing nanorobots may be used. It could remove the right amount of dead skin, remove excess oils, add missing oils, apply the right amounts of natural moisturizing compounds, and even achieve the elusive goal of 'deep pore cleaning' by actually reaching down into pores and cleaning them out .
The nanorobots can also be used for wound debridement. Their size allows them to be very useful for removing dirt and foreign particles from incised and punctured wounds, as well as from burns. They can be used to do a more complete and less traumatic job than conventional techniques .
Nanorobots can also be used for parasite removal in the human body .
Application of nanotechnology in dentistry can greatly enhance oral health care. Its applications may include dentinal renaturalization, hypersensitivity treatment and single visit orthodontic alignment.
A mouthwash full of smart nanomachines could identify and destroy pathogenic bacteria while allowing the harmless flora of the mouth to flourish. Further, the devices would identify particles of food, plaque, or tartar, and lift them from teeth to be rinsed away. Being suspended in liquid and able to swim about, devices would be able to reach surfaces beyond reach of toothbrush bristles or the fibers of floss [16, 17].
The numerous other potential medical applications may include gene therapy via chromosome replacement therapy, anti-aging, retinal and cochlear implants and construction of complete replacement body organs [1, 2].
7. Conclusion & Critical Analysis
Nanomedicine since its inception has become one of the fastest growing fields in medicine and also the most debatable one. If application of nanorobots in medicine is as successful as scientists and researchers claim to be, its effect on medicine would be massive and may be able to reshape the future of current medicine. Though still hypothetical, nanomedicine is expected to revolutionize medicine in the next 20-30 years as some experts suggest. This however will require an excellent infrastructure and would require a lot of expenditure. It will have wide range of applications which will include diagnosis, prevention & treatment of life threatening diseases. Nanomedicine will be able to overcome the shortcomings of current conventional medicine and it will not only be able eliminate diseased cells from the body but will also aim to fix these cells to preserve and rebuild organ systems. It does however has its shortcomings which include safety concerns and toxicology issues. It is important that fundamental research be carried out to address these issues if successful and efficient application of this technology is going to be achieved. For now nanomedicine holds the greatest promise for curing diseases, reducing patient suffering and increasing the human health span of millions in need around the world.