Future Uses of Nanotechnology. Ben Wright. Paper Based on Pathology Lectures Vetsix 2004

Transcription

1 Future Uses of Nanotechnology By Ben Wright Paper Based on Pathology Lectures Vetsix

2 Future uses of Nanotechnology This paper is a brief account of the vast topic of nanotechnology; its developments so far and possible future applications of the field. Nanotechnology covers virtually all aspects of physics and many other areas besides; this report will focus on the uses and possible uses of the technology in medicine, specifically improvements in drug delivery systems and disease detection techniques and surgical procedures. Introduction: The concept of nanotechnology originated from Richard Feynman s speech There s plenty of room at the bottom in This vision of constructing machines from the atom upwards has come a long way since then. The first major breakthrough was the advent of Buckminsterfullerene in the 1980 s. These tiny footballs of 60 carbon atoms heralded the start of an industry that is rapidly expanding, while its products continually shrink. The reason that nanotechnology has been able to create such tiny objects is that it is concerned with building things from the bottom up; starting with individual atoms and arranging them as required rather than chopping atoms off larger structures as is done in micro-technologies and computing etc. Miniature biocomputers constructed in this fashion from RNA molecules (themselves made in specific sequences) have been made to solve chess problems (though not yet to the accuracy of silicon chips). This is a step forward in the development of a biological computer that can be implanted in the body. 1 These DNA-based computers it is said, will one day be able to select the most favourable approach to complex problems by testing vast amounts of solutions simultaneously. Conventional computers are currently unable to do this. Just earlier this year, a Japanese team lead by Koichi Komatsu managed to open up a buckyball (short for Buckminsterfullerene, a compound consisting of 60 carbon atoms arranged in a football structure), place a molecule inside it and then close the hole again with the new substance inside. 3 With the ability to place any substance inside a buckyball, all sorts of possibilities are open to scientists. Encasing noble gases such as xenon could enhance MRI scanners and if metals were to be captured they could be used as transistors or other electronic components in nanoscale circuits. Of course, this breakthrough could have dramatic implications in drug delivery. It is hoped that nanoparticles can be manipulated to carry drugs safely through the patient s digestive system, blood system, or any other biological pathway; directly to the places they are needed. Here the capsules will come apart to release the drug. The protective particles prevent the drugs being destroyed by the immune system and rendered useless before they have reached the desired area, where they are released. With the acquired knowledge of how to break buckyballs apart, this could soon become a reality. Another recent breakthrough in drug delivery is in the development of a system that allows nanocapsules to release their cargoes exactly where they are needed (i.e. tumours). A team of scientists lead by F. Caruso at Melbourne University came up with the method of encapsulating drugs in a casing containing gold nanoparticles and with tumour-locating antibodies affixed on the outside. This caused the capsules to accumulate round cancerous cells where the drugs were needed. The gold particles embedded in the casing are melted by a near-infrared laser (in amounts safe to living cells) which ruptures the capsules, releasing the drugs (see figure 1). 2 Use of this technique would localise the effect of the drugs and 2

3 Figure 1 reduce any unwanted side effects usually associated with chemotherapy. Another use of gold nanoparticles is to use them directly to target cancer cells, rather than using them along with a drug. These nanoshells are attached to antibodies specific to cancerous cells, and so collect around a tumour. When near infra-red is shone on them, they heat up and melt, heating their immediate surroundings. This causes the cancer cells membranes to become more permeable-killing the cells. 4 While the main focus of nanotechnology in medicine at present is on drug delivery systems, there have also been developments in the techniques used to manufacture and test new medicines. For example, artificial cells (tiny globular vials called liposomes) have been simultaneously trapped using an optical scalpel and tweezers by scientists from the National Institute of Standards and Technology. 5 This is an improved technique that allows for quantitative studies of chemicals reacting in samples of trillionths of litres. A procedure like this can be used to make pharmaceutical research both faster and cheaper; getting new drugs out into the market faster. Most of these methods being researched involve the use of antigens on the surface of pathogenic micro organisms to attract antibodies attached to the nanocapsules or particles. This makes use of nature s own techniques (as does the use of DNA and RNA in biocomputers), and so is very likely to succeed. Discussion: The future could include advances such as using nanoscale machines to enhance our immune systems. Artificial antibodies and T and B-lymphocytes could be created that are then left in the lymphatic system or the blood, to react to specific pathogens detected in the body. This will aid the cells and mechanisms already involved in destroying pathogens. Such procedures would be most useful in treatment of diseases such as AIDS and various autoimmune diseases (by maybe destroying the antibody-producing cells responsible for the diseases); defence against infection after surgery or after lacerations, and could even be used to enable more successful transplants to take place. The problem with many organ or tissue transplants is that the body s immune system doesn t recognise the cells antigens as being selfantigens and so attacks them. Nanotechnology has the capability to form machines that could protect the new cells, possibly by destroying the B-cells that produce the 3

4 antibodies against them. However, this may leave the person vulnerable to pathogens with similar antigens to those on the new cells. Evidently, such machines would have to be capable of analysing information and deciding which actions to take in order to know which cells to attack. This is where techniques already being researched such as attaching the appropriate antibodies to the machines or creating a miniature biocomputer would enable the artificial immune system to target specific types of cell or reach conclusions without external intervention. This support of the body s own immune system would require steps in the direction of a merging of biological and technological systems. This itself gives rise to all sorts of interesting possibilities. As well as defence, there is the repair of tissues after surgery or after an accident. Nano-fibres and platelets could be implanted onto a bandage, which when wrapped around a wound would speed up the clotting process. Nanocapsules could be used to take calcium and other substances needed to the site of bone fractures to speed up the knitting of bones. Eventually it may even be possible to manufacture new cells, tissues or even organs in vitro and then implant them into the body. Blindness might be cured with an artificial retina which could be constructed using nanotechnology (made much more sensitive to light than traditional electronic light sensors) and implanted in the eye. The ability to arrange atoms as required would enable mankind to mimic existing features of cells already in the body (such as antigens) precisely, thus improving the cells compatibility with the recipient. The production of a nanoscale biocomputer would mean that such a device could be implanted permanently into a body, where it would either circulate in the blood or remain attached to a specific point. It would then be able to monitor the levels of various substances in the blood and to analyze and act upon the findings. The reaction would be to release specific substances depending on what change has triggered it or to send a signal to outside the body so that the person can act for themself. One such example would be in the treatment of diabetics. If an excess of glucose in the blood or the presence of ketones in the urine is detected, the biocomputer would either release insulin into the blood or alert the person carrying it. A possible drawback for this is that it would only be able to carry a finite amount of chemicals that it can release, so the machine would have to be replenished or replaced at intervals. The process of actually inserting it could be done by injection (as are indentichips in pets). The recent research on treatment targeted to specific cells is likely to get results in the not so distant future. This exact application of drugs means that they act over a smaller area and thus smaller doses can be administered. As they are only affecting their target cells, there are very few side effects (unlike in current chemotherapy) and the drugs are not altered by chemical processes inside the body at all as they are encapsulated. As well as curing disease and fighting it once the pathogens are inside the body, nanotechnology could be used to keep them out of the body. For example, protective machines could be sprayed onto cuts and abrasions or they could be placed inside the mouth or nose. These are the places that pathogenic micro-organisms most often enter, and so they can be detected and destroyed before they even enter the body. This has profound implications in the control of epidemics and pandemics. If the viruses or bacteria behind an outbreak of disease can be identified and the spread noticed quickly enough, measures against its spread can be more effective. This could be achieved using nanoscale machines to detect pathogens and record the area 4

5 where each case of the illness occurred on a central computer (connected to all such nanobots). This can provide an accurate picture of the spread of the disease at a very early stage, allowing preventative measures to be put in place. The micro organisms causing outbursts of disease could one day be halted before the start point of the disease is even detected. Currently, surgeons are only able to perform very limited surgery when it comes to the size of the organelles they are operating on. This is due to the restricted size of the tools used. With the recent invention of nanomotors, nanotweezers, nanosized surgical lasers and other such devices, it may soon be possible to perform surgery on the nanoscale, repairing the exact body parts that are malfunctioning. These machines could be controlled using scaled down movements of a surgeon s hand (viewed on a screen) so that the doctors are still able to take charge if anything goes wrong or needs altering. Many current hereditary diseases could be fixed at source, by altering the genes that cause them. Genetic engineering has gone some way to being able to do this; however, it has to rely on ready-made genes being added or taken away from the chromosome of the organism being treated. Using the bottom-up technique developed in nanotechnology could allow the manipulation of individual bases (or even atoms) to create specific genes or to remove or fix faulty genes in a genome. This could make the development of strains of bacteria that produce specific substances a lot faster and more efficient. Diseases such as cystic fibrosis (where the mutation causing the disease is the same in 70% of cases) 6 could be the first to benefit from any research in this field. Ultimately it may be possible for entire chromosomes or even genomes to be created from scratch. Conclusion: It is likely that in the future, all the current research will devise techniques and machines that make possible the many opportunities presented by nanotechnology. However, there are still many aspects of the topic that are not fully understood, due to some extent to the huge diversity of the subject and its multidisciplinary nature, but also because it is a relatively new area to science. If procedures based on this technology are to be used in medicine, all possible forms and outcomes must be considered. Clinical trials will no doubt have to be extensive, and any initial use of nanomachines to enhance the immune system, monitor and influence the bodily systems or repair faulty body parts will have to be closely observed themselves and only employed in isolated instances so that any possible pitfalls that haven t been foreseen can be found and the methods altered accordingly. Another big issue is that of public response. Nanotechnology has already developed a stereotype of invisible machines and components in computers, and tends not to be associated with medical practice. Eric Drexler s grey goo theory, where invisible machines replicate out of control (1986, Engines of Creation) may have even supplied the public consciousness with a stigma about nanotechnology. The use of nanotechnology in genetic manipulation has massive ethical implications, and is unlikely to be received well by those who do not need treatment by any of these techniques. Other areas of concern may include the use of machines that cannot be directly controlled to administer drugs to our body. If the scientists get it wrong or a nanocomputer malfunctions inside a person, it could cause all sorts of problems that may not be easy to sort out. A possible solution to this worry is to have built-in destruct devices on each of the machines that can be operated from afar. 5

6 Nanotechnology is very much in its infancy, and many new and exciting developments can be expected in the not too distant future. People could soon be treated by things they cannot even see, that target exactly what the problem is, and doctors may soon have a much lighter workload. 6

7 References: 1. J. Knight, Biocomputers take their first step, 2. Rachel Nowak, Smart bombs to blast tumours, New Scientist (8 th Jan 2005), Pg C. Biever, Stuffed buckyballs, clearer MRI scans, New Scientist (22 nd Jan, 2005), Pg Shaoni Bhattacharya, Gold nano-bullets shoot down tumours, 5. Tiny test tubes may aid pharmaceutical R&D, 6. G & S Toole (1987), Understanding Biology for Advanced Level, Pg 124 Figure: