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Nanomedicine is defined as the field in which molecular tools and molecular knowledge are used to identify, protect, treat, improve and reduce the pain in the human body from diseases. This report mainly emphasis on the applications of nanomedicine for treating various diseases. Nanomedicine is a branch of nanotechnology which deals with medical applications. Firstly we study the origin of nanotechnology and how it influenced the research word. We will study the history of nanomedicine and their potential application in the medical field such as target drug delivery, tissue engineering and nano robotics. In detailed information is given regarding the tissue engineering which includes treating liver, intestine and heart valve and cancer treatment using drug delivery. Nano robotics explains about the three forms of nanorobots such as respirocytes, microbivores and clottocytes present in human body.
The word nanotechnology was originated from a lecture given by Richard Feynman in 1959 at California institute of technology on a topic "There is a plenty of Room at the bottom". But this idea is not recognised until 1986, when Eric Drexler proposed that molecular nanotechnology can be used to build any product from bottom up by using molecular control. Feynman's view is used today in several nano-assembly processes. Nanotechnology can be defined as the technology used to easily understand and control any type of matter between dimensions from 1 to 100 nanometres and produce possible novel applications, from this definition it suggests two important statements for nanotechnology, where 'nano' word suggest that nanotechnology involves only up to a limited size and 'novelty' describes that it not only concerned with small size but also deals with some properties due to nano-scale. [1-2]
In 2000 the United States president announced that he is allocating $457 million funds for research in nanotechnology, but he never used the word nanotechnology and used to describe it as a technology which is going to produce molecular computers at a size of tear drop. Then in 2004 the investment reached up to $849 million and in last year's the funding reached up to $1.64 Billion. European countries invested up to 1.3 billion Euros during 2003-2006 and for 2007-2013 funding up to 3464 million Euros was announced. [3-4-5]
The U.S national institute of health in December 2002 introduced a four year program in nano-science and technology for medicine, where the medical applications involved in nanotechnology is called as nanomedicine. Nanomedicine uses molecular tools and molecular knowledge of human body for identifying, treating, protecting from disease, reducing the pain and improves the human health. Present day nanomedicine act in structure of nano-particles as a Bucky-balls and as nano-shells that is used for targeted drug delivery. [3-6]
Before nanomedicine came into existence many treatments were implemented using nanotechnology. Artificial bone implants were done by using improved materials of nanotechnology, tissue growth is controlled by using nanostructure surfaces as scaffolding and tumor cells. When nanomedicine came into existence it has molecular understanding on cellular processes and now it has a capability to produce nanoscale materials in a controlled manner. [6-7]
History of Nanomedicine:
The history of nanomedicine starts from 1999 when Robert freitas in his book proposed an idea by describing about ongoing developments that leads to extravagant speculations (Excessive contemplation). In 2006 a speech was given at European science foundation, which states that in future they can detect a single molecule or cell in a complex biological environment. 
The main objective of nanomedicine is to cure the disease at molecular level. Nanomedicine is mainly categorised into three significant research areas namely drug delivery, tissue engineering and nanorobots. 
The main application of nanotechnology is target drug delivery. In case of cancer patients rather than using highly toxic chemotherapy we can inject coated nano-particles into body and there by heating them by using light we can eliminate the diseased tissues and cells. 
The second application is used in human tissue engineering. In this tissue engineering it helps to repair tissues that are damaged. 
The third application is in the area of nano-robots. These are introduced into human bodies to repair damaged tissues. 
We will now have a look at the applications of nanomedicine in detail,
1) Tissue engineering:
Every year in United States millions of people are effected with tissue loss by accidents or diseases. In recent years the medical devices were greatly developed for the patients affected by tissue loss, where transplantation field gained importance during the past 40 years. But this organ transplantation process was limited only for few years due to shortage of donor organs and also it is very costly and had many technical difficulties. Due to all these reasons an investigation has taken place whether a selective cell-transplantation can be done instead of full organ transplantation. Cell transplantation has many advantages; by taking only one donor organ tissue we can expand it by Vitro process, which supplies unlimited cells. In UK annually around 50% people were affected with damage tissues, where due to lack of donors it leads to produce viable tissue. Finally all these factors lead to the development of tissue engineering. Tissue engineering is defined as a field that can apply all the principles of sciences and engineering in the development of biological substitutes to improve the function of human tissues. Nanomedicine in tissue engineering is defined as the replacement of lost organ having regenerative medicine. [9-10]
Tissue engineering is an alternative for organ implantation and the loss of tissue; this can be treated by implantation of any biological substitute or with vivo system. The products of tissue engineering are fully functional at the treatment time like in liver assist devices. The three general principles of tissue engineering are given below. All three principles are co-relating and the main aim of these is to create a new tissue. [9-11]
In vitro the human tissues are designed and grown for lateral use for repairing the damaged tissue. This type of application can be observed in skin graft, this is used when burn occurs on skin and this type of tissue culture is available from the last 10 years. 
Placing cell free devices that are used for regeneration of human tissues. 
For example if we want to replace a bone or muscle for heart valve an external device must be developed with human tissue that can replace internal tissue that is affected. By using this method within the body a new system can be implanted. 
But now a day's third application is mainly used to develop an external device that can replace in body if any tissue is damaged. To produce a new tissue there are many approaches but the basic concept is same. Here in below we discuss about tissue engineering in liver, intestine and in heart valve. [11-9]
Liver: Before the idea of transplantation introduced more than 26000 people were died in United States due to the liver diseases. The liver transplantation have good success rate in treating end stage liver diseases when compared with diseases related to kidney or any failure of other organs. Annually around 3000 liver transplantations have been performed in United States; the main problem for the transplantation is the shortage of organ donors, this problem directed to probe into selective cell transplantation. 
Intestine: By using the principle of tissue engineering transplantation of intestine cells, new intestinal tissues are generated by using synthetic bio-degradable polymer scaffolds. This is also used in short bowl syndrome treatment. 
Heart valve: In United States the heart valve disease is a major reason of morbidity. The solution for this disease is valve substitution but there are some limitations in the prosthetic valve. To subdue the limitations fabrication of tissue engineered heart valve leaflets are investigated. The advantages of using heart valve leaflet are it has the capacity to repair, durability, growth and minimum risk of infection. 
The current challenge in tissue engineering is taking place on the blood vessels of the microcirculation. The problem involved is there is no own blood supplied due to size of tissues in vitro. Due to these sizes of tissues they consume entire oxygen within few hours and take many days to grow new blood vessels. 
Finally the use of nanotechnology in tissue engineering is involved to change the pathway of molecular level, assume them keeping back cells into three dimensional shape. Tissue engineering is also used in changing the structure of current state to another state to perform more effectively. Tissue engineering is not only limited for reconstruction of damage cells but also it includes in stabilizing the native tissue. Tissue engineering in nanomedicine is to change the environment condition by adding or subtracting or manipulating it allowing as required to our condition. 
2) Targeted drug delivery: In future the nanomedicine in drug delivery is been excepted to bring a change in both the biotechnology and pharmaceutical industries. Nanomedicine uses the nano size particles and system. 
Nanomedicine is used to detect and treat any type of diseases at molecular level by using nano sized particles and assigned a goal for eliminating the deaths occurred due to cancer by 2015. 
Here we are going to discuss about drug delivery in cancer treatment:
The anticancer transport to interestium is controlled by its properties of the body itself like size, change of pressure and the composition. There are some problems involved in deliver of therapeutic agents to tumor cells in vivo. They are at initial states only, the drug resistance at both tumor level and cellular level must be checked. Then distribution of anticancer drugs into body must be perfectly done. [14-15]
There are some methods and strategies for drug delivery that is used to fight with cancers, which are mentioned below.
The anticancer drug is directly injected to tumor i.e. the effected part in the body.
Tumor is killed by using therapy. 
Anticancer drug is injected to blood supply valves of cancer.
This anticancer drug can be injected into tumor by electro chemotherapy.
There are many routes for drug delivery to inject the anticancer drugs to tumors by nasal, pulmonary inhalation, oral, and by vascular route. 
The anticancer drug can be directly delivered to blood vessels of tumor by therapy like anti angiogenesis then directly the anticancer drug is delivered where blood is clotted in tumor. 
There are many ways of biological therapies for this drug delivery. They are cell therapy, gene therapy, antisense therapy, etc.
There are some pathways for drug delivery. They are nanoshells, nanoparticles, microspheres and then delivery of drugs and peptides for cancer therapy. 
There is a high potential for nanotechnology in preventing, detecting, treating cancer and also it can detect the target of tumor and can deliver anticancer drugs according to the tumor characteristics. The nano-particles are now being investigated by researchers that can target tumor and act as immune system. There is still research going on to deliver smart bombs that can deliver the anticancer drug to tumors directly. 
Until now in some experiments conducted the nano particles are delivered inside animal body and they are delivering the anticancer drug directly to effected tumor inside the body. And these anticancer drugs are having high toxic effects they can deliver high concentration of anti tumor with less toxic effect. From these the nanoparticles can deliver high anticancer drug to detect and kill the cancer cell. 
Nano particles that are made for challenging cancer diseases must be in size of sub micronic and made from polymers like Nanospheres, Nanoshells and Nanocapsules. Nanocapsule is a particle having drug in the cavity and it is designed as such it can act as drug delivery to deliver any antidrug to the effected tumor cell. [14-15]
3) Nano-Robotics: The next important development taking place in nanomedicine is in molecular nanotechnology of nano-robotics. As the research in biotechnology progresses there is an increase in the usage of nano-materials in many treatments and in the molecular nanotechnology and also expected to increase the comfort, speed, reducing the risk and cost and allows doctors to directly perform surgery to human cells in vivo. In future definitely the medicine is going to shift from medical science to medical engineering and to reach this goal nanomedicine possess two significant factors. They are nanoscale parts fabrication and assembly. Nanorobots with three dimensional structure monitoring inside the body to maintain nutrient concentration is a possible application. Nanorobots are also used to maintain red and white blood cells to repair damage tissues. And these are allowed to maintain chemical reactions in body and to cure injure organs. These are helpful for diabetes patients by including nanorobots with sensors inside the body to maintain glucose level and these nanorobots are also used in cancer for chemotherapy process and recently research is going on to deliver anti HIV drugs and these are termed as pharmacytes. [16-17]
Basically the idea of planning nanorobots inside a body may be odd but already in our body there are some nano devices. For example there are more than 40 trillion single celled microbes which are inside the body. Our bodies also maintain more than trillion nanodevices called fibroblasts, white cells with each having a size of loss. These types of natural nanorobots will move along our body and do repairs for all that are damaged. 
Today in MEMS there is an ongoing project on micro robotics that can use in vivo. Here a magnetic field is generated on a robot that contains ferromagnetic materials that gives power directly to a small device that moves entire human body. Here in first generation by this micro robotics they are used as targeted drug delivery and can open any valve that is blocked. 
In two or three decades the nanomedicine will be emerged when we know about the construction of artificial nanorobots using diamonded nanometer-scale parts with subparts like sensors and motors. These entire studies are not only to design a nano medical product but also to do research on set of designs and scaling issues. In below we can see how nano robots exist in human body. 
(a)Respirocytes: Respirocytes are nothing but artificial red blood cells that are in nanometer scale diamondiod shape with pressure of 1000atm as observed in figure (a) below. Here the pumping done actively and produces glucose and oxygen more than 236 times to the tissues. Nanorobot here formed with 18billion atoms and consists of 3billion oxygen atoms carbon dioxide molecules and these are released through the molecular pumps in a controlled manner. As the sensors are placed on these nanorobots, it is able to know gas concentrations inside and outside, when the oxygen must be loaded and carbon dioxide should be removed. Medical applications of respriocytes are applied in tumor therapies, lung disorders and artificial breathing, etc. 
Figure (a): Respirocytes-An Artificial Red blood cell 
(b)Microbivores: Microbivores means white blood cells and these are used to destroy microbiological pathogens in the human blood. These microbivores are in spherical shape with diameter of 3.4Î¼m as shown in figure (b) below. These microbivores can consume more continuous power up to 200pW. By using microbivores we can eliminate infections within minutes. Compare to natural defences the microbivores can work more than 1000 times faster. 
Figure (b): Microbivores-An Artificial White blood cell 
(c)Clottocytes: Clottocytes are artificial chemical blood platelet that can allow forming hemostasis for any large wound with in a second and this response time is more than naturally occurring system. Clottocytes is a serum oxy-glucose spherical nanorobot with 24Î¼m diameter. If there is any command from its control computer then it forms an immediate mesh there in desired cut position. If the computer says there is cut in blood vessel at desired position then it forms soluble thin films that are sticky because of plasma water and finally forms mesh in desired place. If there is a large cut in blood vessels up to 350 platelets then clottocytes rapidly communicate with all other devices and immediately a mesh will be formed within a second. Generally Clottocytes are appeared to be more powerful then natural platelets. 
From the report we can conclude that nanomedicine which is a part of nanotechnology has potential applications in the field of medicine. Nanomedicine is defined as a field which uses molecular tools and molecular knowledge of human body for identifying, protecting, treating the diseases as well as reducing the pain and improving the human health. Detailed information was given regarding the potential applications such as target drug delivery, tissue engineering and nanorobotics. Also various areas were identified in which these can be applied such as cancer, liver diseases, intestine related diseases were discussed. Finally tissue engineering, drug delivery and nano robotics are the three major applications of nanomedicine which has bright future, but there must be continuous research process in nanomedicine in order to reach the desired goals.