NANOBOT : A NEW TECHNIQUE FOR CANCER TREATMENT

CANCER - IN A NUTSHELL

              Fig : Uncontrolled cell division 

Cancers are a large family of diseases that involve abnormal cell growth with the potential to invade or spread to other parts of the body.They form a subset of neoplasm. A neoplasm or tumor is a group of cells that have undergone unregulated growth and will often form a mass or lump, but may be distributed diffusely.

All tumor cells show the 6 hallmarks of cancer. These characteristics are required to produce a malignant tumor. They include:

• Cell growth and division absent the proper signals
• Continuous growth and division even given contrary signals
• Avoidance of programmed cell death
• Limitless number of cell divisions
• Promoting blood vessel construction
• Invasion of tissue and formation of metastasis.

The progression from normal cells to cells that can form a detectable mass to outright cancer involves multiple steps known as malignant progression.

NANOBOT - WHAT IS IT ? 

Fig : Parts of a nanobot

The field of nanotechnology is concerned with the research and development of technology approximately 1 to 100 nano metres in scale. Therefore, nano robotics is focused on the creation of robots that are around this size. In practice, it’s difficult to engineer anything as small as one nano meter in scale and the term “nano-robotics” and “nanobot” is frequently applied to devices which are approximately 0.1 – 10 micrometers in size, which is still quite small.

Nano-machines are largely in the research and development phase,but some primitive molecular machines and nano-motors have been tested.The first useful applications of nano-machines may be in nano medicines. For example, biological machine could be used to identify and destroy cancer cells.

ARCHITECTURE OF NANOBOTS

Fig : Architecture of nanobots

The architecture is based on two criteria, which are means of nano robot navigation and methods to attach to the cancerous cells. It is important that the device is able to have a smooth trajectory path while navigating in the blood environment and at the same time does not cause any damage to other cells. On the other hand, a microcomputer consisting of a miniature processor might be needed to provide a “brain” to the nano robot.
The body of the nanobot will be constructed from carbon nanotube due to its intrinsic property where they tend to absorb near infrared light waves. Ultrasonic sensors are attached around the body of the nano robot for collision avoidance purposes. Folate materials on the body of the nano robot act as an agent that will cause the attraction of the nano robot to the cancerous cells, which is also known as the folate-receptor cells.The flagella provide the movement the nano robot in the blood environment. It is powered by flagella motors.  When the motors rotate the flagella in a counterclockwise direction as viewed along the flagella filament from outside.  When the motor rotates clockwise, the flagella fly apart, causing the bacteria to tumble, or change its direction. The flagella motors allow the nano robot to move at speed as much as 25 μm/s with directional reversals occurring approximately 1/s.

Fig : Nanobot trajectory

MANUFACTURING TECHNOLOGY

 Complementary metal oxide semiconductor (CMOS) very large scale integration systems design using deep ultraviolet lithography provide high precision and a commercial way for manufacturing early nano devices and nano electronics systems. 

CHEMICAL SENSOR

Chemical nano sensors can be embedded in the nano robot to monitor E-cadherin gradients. Thus, nanobots programmed for such a task can make a detailed screening of the patient whole body. In various medical nano robotic architecture, the mobile phone is applied to retrieve information about the patient conditions. For that, it uses electromagnetic waves to command.

Fig : Chemical sensor of nanobot

CHEMICAL SIGNALS INSIDE BODY

Power supply

The use of CMOS for active telemetry and power supply is the most effective and secure way to ensure energy as long as necessary to keep the nano robot in operation.  Nano circuits with resonant electric properties can operate as a chip providing electromagnetic energy supplying 1.7 mA at 3.3 V for power. Radio frequency (RF)-based telemetry procedures have demonstrated good results in patient monitoring and power transmission. The energy received can be also saved in ranges of ~1 μW while the nano robot stays in inactive modes.

Data transmission

The use of RFID for in vivo data collecting and transmission was successfully tested for electroencephalograms (EEG). For communication in liquid work spaces, depending on the application, acoustic, light, RF and chemical signals may be considered as possible choices for communication and data transmission. Chemical signaling is quite useful for nearby communication among nano robots for some teamwork coordination. Using integrated sensors for data transfer is the better answer to read and write data in implanted devices. Teams of nano robots may be equipped with single chip RFID CMOS based sensors. CMOS with sub-micron SoC design could be used for extremely low power consumption with nano robots communicating collectively for longer distances through acoustic sensors. 

Fig : Data transmission in nanobots

Nanobots in cancer detection and treatment

                                    Fig : Mechanism of action of nanobots in cancer treatment



 Various NPs used are cantilever, nano pores, nano tubes and quantum dots. These are being briefly described here in the literature.

Cantilever

As cancer cells secrete its molecular products, the antibodies coated on the cantilever fingers selectively bind to these secreted proteins. 

Nano pore

Another interesting device is nano pore. Improved methods of reading the genetic code will help researchers in detecting errors in gene that may contribute to cancer. Nano-pores contain a tiny hole that allows deoxyribonucleic acid (DNA) to pass through one stand at a time making DNA sequencing more efficient.

Nano tubes

Nano tubes carbon rods about half the diameter of a molecule of DNA will not only detect the presence of altered genes, but also pinpoint the exact location of those changes. 

Fig : Carbon nanotube of nanobots

Quantum dots

Quantum dots are tiny crystals that glow when they are stimulated by ultraviolet light. When injected into the body, they would drift around until encountering cancerous tissue. The light particles would serve as a beacon to show doctors where the disease has spread. The nano robots will be able to distinguish between different cell types that is the malignant and the normal cells by checking their surface antigens this can be accomplished by the use of chemo-tactic sensors keyed to the specific antigens on the target cells. Using chemical sensors they can be programmed to detect different levels of E-cadherin and beta-catenin in primary and metastatic phases. Medical nano-robots will then destroy only the cancerous cells. There are ongoing attempts to build micro-electromechanical system [MEMS]-based micro-robots intended for in-vivo use. Application of the first generation prototype might include targeted drug release, the reopening of blocked arteries, or taking biopsies. 

The nanobots may enable drug delivery and are loaded with therapeutic chemicals avoiding the cancer to advance further. Dendrimer and nano-shells, liposomes, NP, Michelle are used for drug delivery.

Dendrimers

These are spherical, highly branched and synthetic macro-molecules. A single dendrimer can carry a molecule that recognizes cancer cell, a therapeutic agent to kill those cells, a molecule that recognizes the signal of cell death. 

Nano-shells

Nano-shells have a core of silica and a metallic outer layer. By manipulating the thickness of the layer, scientist can design beads to absorb near infra-red light, creating an intense heat that is lethal to cancer cells. 

Liposomes

Liposomes have a long history as drug carrier systems because of their easy preparation, acceptable toxicity and biodegradability profiles. Drug loading in liposomes can be achieved through: (1) Liposome formation in an aqueous solution saturated with soluble drug; (2) the use of organic solvents and solvent exchange mechanisms; (3) the use of lipophilic drugs; and (4) pH gradient methods.

                      Fig : Liposome 

Polymeric NP

Polymeric NP, which include nano-spheres and nano-capsules, are solid carriers ranging from 10 to 1000 NM in diameter made of natural or artificial polymers which are generally biodegradable and in which therapeutic drugs can be adsorbed, dissolved, entrapped, encapsulated or covalent linked to the polymer backbone by means of a simple ester or amide bond that can be hydrolyzed in vivo through a change of pH. 

Michelle

Polymeric Michelle are biodegradable spherical nano-carriers with a usual size range of 10-200 NM. The hydrophobic core can be used to carry pharmaceuticals, especially lipophilic drugs, which are solubilized and physically entrapped in the inner region with high loading capacity. Polymeric micelles can simultaneously co-deliver two or more therapeutic agents and are capable of releasing drugs in a regulated manner. External conditions such as change of pH and temperature can also induce drug release from micelles. Moreover, the surface modification of micelles with ligands such as antibodies, peptides, or other small molecules can be used for targeted delivery and uptake of these nano-carriers.

Fig : Improvement of cancer treatment by nanobots

» Disadvantages

• The initial design cost is very high.
• Electrical systems can create stray fields which may activate bio electric-based molecular recognition systems in biology.
• Nanobots can cause a brutal risk in the field of terrorism. The terrorism and anti-groups can make use of nanobots as a new form of torturing the communities as nanotechnology also has the capability of destructing the human body at the molecular level
• Privacy is the other potential risk involved with Nanobots. As Nanobots deals with the designing of compact and minute devices, there are chances for more eavesdropping than that already exists.

» Conclusion

• This science might sound like a fiction now, but nano-robotics has strong potential to revolutionize health-care, to treat disease in future. It opens up new ways for vast, abundant research work in oncotherapy.
• We are at the dawn of a new era in which many disciplines will merge, including robotics, mechanical, chemical and biomedical engineering, chemistry, biology, physics and mathematics, so that a fully functional system will be developed.