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Nanotechnology
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Nanotechnology
Nanomedicine
Please Note: This article is a review of medical applications in the use of nanotechnology. It is not meant to be comprehensive. It does not include all the potential uses and current research involved in nanomedicine.
A nanometer is one-billionth of a meter. It is at nanoscale100 nanometers or lessthat that biological molecules and structures inside living cells operate.
The Promise of Nanomedicine
The ultimate promise of nanomedicine is the eradication of disease. To accomplish this goal requires the convergence of nanotechnology and biotechnology. In turn, nanomedicine is the convergence of many disciplines: biology, chemistry, physics, engineering and material science.
The eradication of disease involves three sub-goals:
1) Using nano-robots, nano-machines or other methods at the molecular level to search and destroy disease-causing cells
2) Same as above for the purposes of repairing damaged cells
3) Using pumps or similar technology at the molecular scale as a means of drug delivery
Nanotechnology involves the creation and use of materials and devices at the level of molecules and atoms. As life itself creates and uses molecular materials and devices, nanoscience will provide great insights in life science concepts, such as how molecular materials self-assemble, self-regulate, and self-destroy.
Nanomedicine eventually will infiltrate virtually every field of medicine, if not every realm of human endeavor.
Nanomedicine may be defined as the monitoring, repair, construction and control of human biological systems at the molecular level, using engineered nanodevices and nanostructures.
A sample list of areas covered by and converged with nanomedicine include: Biotechnology, Genomics, Genetic Engineering, Cell Biology, Stem Cells, Cloning, Prosthetics, Cybernetics, Neural Medicine, Dentistry, Cryonics, Veterinary Medicine, Biosensors, Biological Warfare, Cellular Reprogramming, Diagnostics, Drug Delivery, Gene Therapy, Human Enhancement, Imaging Techniques, Skin Care, Anti-Aging.
Nanomedical Issues
Other nanomedical issues include sensory feedback, control architectures, cellular repair and destruction, replication, safety, biocompatibility, environmental interaction, genetic analysis, diagnosis and treatment. Treatment covers the full range of illness and disease, from cardiovascular to trauma, amputations to burns, brain, spinal and other neural injuries/diseases, nutrition, sex and reproduction, cosmetics and aging.
Tools
Tools in nanomedicine involve microscopy techniques and equipment used to visualize cells, bacteria, viruses and single molecules at the nanoscale. Tools range from the atomic force microscope (AFM), scanning tunneling microscope (STM) to molecular modeling software and various production technologies.
Materials
Raw nanomaterials include nanoparticles and nanocrystalline materials that substitute for weaker performing bulk materials. Nanomaterials can be used as biocompatible materials or coatings in drug encapsulation, bone replacements, prostheses, and implants. Nanostructured materials are processed forms of raw nanomaterials that provide shapes or functionality.
Examples of nanostructured materials include quantum dots (nanostructures which force atoms to occupy discrete energy states as in biological markers), and dendrimers (branched polymers used for drug delivery, filtration and chemical markers).
Nanotubes and fullerenes are new forms of carbon molecules that produce materials 100 times stronger than steel and one-sixth of its weight, more conductive than copper, and can be safely used in some medical applications. While still in the development stage, the range of nanotube and fullerene applications includes artificial muscles, injection needles for individual cells, and drug delivery systems.
A nanotube is a long, cylindrical carbon structure consisting of hexagonal graphite molecules attached at the edges. The nanotube developed from the so-called fullerene, a structure similar to the way geodesic domes, originally conceived by R. Buckminster Fuller, are built. Because of this, nanotubes are sometimes called buckytubes.
Devices
Nanodevices will supplement current micro devices, which includes micro-electromechanical systems (MEMS), microfluidics, and microarrays. Examples of medical applications include biosensors and detectors to detect trace quantities of bacteria, airborne pathogens, biological hazards, and disease signatures, microfluidic applications for DNA testing and implantable fluid injection systems and MEMS devices which contain miniature moving parts for pacemakers and surgical devices.
MEMS stands for Micro Electronic Mechanical Systems, a technology used to integrate various electro-mechanical functions onto integrated circuits. A typical MEMS device combines a sensor and logic to perform a monitoring function. A typical example is the sensing device used to deploy airbags in cars and switching devices used in optical telecommunications cables. MEMS developers will be able to exploit nanotechnologies in fabricating new integrated circuits (NEMSNano Electrical Mechanical Systems).
Intelligent Materials and Machines
The future holds promise for robots called nanorobots or nanobots, injected into the body and used to destroy disease-causing cells and repair damaged ones. Other potential applications include intelligent materials that can sense external stimuli and adapt to changes in the environment, molecular machines that construct materials atom by atom, and molecular assemblers that can mass produce molecular machines.
For an animated video of nanorobots see:
http://www.bionano.neu.edu/mru.html
Drug Delivery
Nanotechnology provides a wide range of new technologies that optimize the delivery of pharmaceutical products. Drugs need to be protected during their transit to the target area in the body while maintaining their biological and chemicals properties. Some drugs are highly toxic.
Timing of drug delivery, as well as materials and production processes are critical in relation to absorption, distribution, metabolism, defense mechanisms, interaction with other drugs, binding and interaction with receptor and excretion. Side effects are a risk.
Drug Encapsulation
Protecting drugs as they are delivered through the body involve drug encapsulation materials like liposomes and polymers. The materials form capsules around the drugs and permit timed drug release to occur as the drug diffuses through the encapsulation material. Drugs are also released as encapsulation material degrades in the body.
When encapsulation materials are produced from nanoparticles in the 1 to 100nm size range instead of bigger microparticles, they have a larger surface area for the same volume, smaller pore size, improved solubility, and different structural properties. This can improve both the diffusion and degradation characteristics of the encapsulation material.
Many types of nanoparticles are being explored for encapsulation. The use of nanoparticle encapsulation is also being considered for neurological and vision disorders.
Nanostructures have the ability to enter cells that typically internalize materials below 100nm.
Drug Discovery
Both micro and nano technologies in combination with other technologies and tools such as combinatorial chemistry, computational biology, computer-aided drug design, data mining, and data processing tools are being explored as new ways in increasing the discovery and development of new drugs.
Implantable Materials and Tissue Repair
Nanotechnology provides a new generation of biocompatible nanomaterials for repairing and replacing human tissues.
Obstacles to overcome in implanted materials like artificial bones include immune rejection, corrosion due to body fluids and weak bonding to natural bone. Nanomaterials offer larger surface area to volume ratios and greater bonding qualities. Nanomaterials and coatings increase adhesion, durability and lifespan of implants.
Some parts of the anatomy are self-healing but can result in scar formation. Nanotechnology offers greater control and flexibility in such areas as skin grafting and other cosmetic applications. This is because nanoscale materials operate at the cellular and genetic level where repair and regeneration occurs.
A variety of natural materials are used as bone substitutes. These include autograft from the patients pelvis, allograft from another human, bovine material or coral blocks. Natural materials tend to be brittle and can lose mechanical strength during sterilization. They can cause inflammation, pain at the pelvis graft site, and potentially transmit disease. Bone cavities filled with synthetic bone cement have been linked to tissue damage, nerve root pain and other side effects. Nanomedicine promises to solve these problems with greater safety.
High strength nanoceramic materials, such as calcium phosphate apatite and hydroxyapatite can be made into a nanoparticle paste that interacts more positively with bone. These materials can be used for both weight bearing and non-weight bearing bones.
Bioresorbable Materials
Nanotechnology brings advances in bioresorbable materials. Bioresorbable polymers are currently used in degradable medical applications like sutures and orthopedic fixation devices. Bioresorbable implants will biodegrade and do not have to be removed manually.
Research is being done on a flexible nanofiber membrane mesh that can be applied to heart tissue in open-heart surgery. The mesh is infused with antibiotics, painkillers and medicines in small quantities, and then applied directly to the hearts tissues.
Smart Materials
Smart materials are nanomaterials that respond to changes in temperature and other changes in the environment. Possible applications include a smart polymer used as an artificial muscle with greater mechanical strength and flexibility. Smart materials can potentially sense disturbances or trigger physical reactions in the body far beyond current human performance limits.
Implantable Devices
Nanotechnology offers sensing technologies (sensor devices) that provide more accurate and timely medical information for diagnosing disease and administering treatment. Current diagnostic methods for many illnesses and diseases involve invasive procedures and extensive laboratory testing that can take weeks before results are available.
Some medical information is extremely time sensitive such as blood flow to an organ or tissue after transplant or surgery, before irreversible damage occurs. Many tests such as biopsies are subjective and can result in erroneous conclusions. Self-administered tests are risky, like those used in diabetes, especially where children and the elderly are concerned.
Exposure to radiation or hazardous chemicals increases the risk of illness. Implanted nanodevices can provide early detection and even initiate timely treatment with a higher chance of success before damage occurs.
Nanotechnology can offer new implantable and/or wearable sensing technologies that provide continuous and extremely accurate medical information for both diagnosis and treatment.
Sensors
NASA is researching nanosized sensors for detecting radiation levels in astronauts. Sensor microchips are also being developed to continuously monitor key body parameters including pulse, temperature and blood glucose. A chip would be implanted under the skin and transmit a signal that could be monitored continuously.
Nano-sized implantable fluid injection systems can dispense drugs electrically on demand making use of microfluidic systems, miniature pumps, and reservoirs. Initial applications may include chemotherapy that directly targets tumors in the colon and are programmed to dispense precise amounts of medication at the right times.
Implantable sensors can monitor and regulate the heart or any other organ in the body. Sensors can more accurately measure strain and other processes involving artificial limbs while at the same time remaining non-intrusive. Functional Electrical Stimulation (FES) is a current method for treating paralyzed limbs by electrically stimulating paralyzed muscles with implanted electrodes.
Nanotechnology is being used to develop more powerful devices to restore lost vision and hearing functions. The devices collect and transform data into precise electrical signals that are delivered directly to the human nervous system.
In the ear (cochlea), for instance, the inner and outer hair sensory cells are sensitive transducers that convert mechanical fluid motion into electrical impulses in the auditory nerve. Cochlear implants are designed to substitute for the function of the middle ear, cochlear mechanical motion, and sensory cells. Implants in the cochlea have a number of drawbacks like major surgery or loss of hearing or distorted hearing.
Nanotechnologies are being used in a new generation of implantable devices for improving sensory loss and to allow surgeons to monitor physiological and biomechanical processes and perform tasks with greater precision and safety and less stress.
Smart Instruments
Surgical tools such as scalpels, forceps, grippers, retractors and drills are being embedded with miniature sensors to provide real-time information and added functionality to aid surgeons. Surgeons can be given continuous data on the force and performance of their instruments, the tissue type about to be cut (i.e. cartilage, bone, muscle, vascular, etc) and specific tissue properties, such as density, temperature, pressure, and electrical impulses.
Robotics
Robotic surgical systems are being developed to provide surgeons with unprecedented control over precision instruments. This is particularly useful for minimally invasive surgery. Instead of manipulating surgical instruments, surgeons use their thumbs and fingers to move joystick handles on a control console to maneuver two robot arms containing miniature instruments that are inserted into ports in the patient. The surgeons movements transform large motions on the remote controls into micro-movements on the robot arms to greatly improve mechanical precision and safety.
A third robot arm holds a miniature camera, which is inserted through a small opening into the patient. The camera projects highly magnified 3-D images on a console to give a broad view of the interior surgical site. The surgeon controlling the robot is seated at an ergonomically designed console with less physical stress than traditional operating room conditions.
Other Applications
New imaging technologies will provide high quality images not currently possible with current devices. This allows greater surgical precision and targeted treatment. Chasing cancerous cells or removing tumors can result in severely damaged normal tissue or the loss of abilities like hearing and speech as in the case of brain tumors. Nanotechnology can offer new solutions for the early detection of cancer and other diseases.
Nanoprobes can be used with magnetic resonance imaging (MRI). Nanoparticles with a magnetic core are attached to a cancer antibody that attracts cancer cells. The nanoparticles are also linked with a dye, easily seen on an MRI. The nanoprobes latch onto cancer cells and once detected by MRI, can then emit laser or low dosage killing agents that attack only the diseased cells.
Miniature devices are also implantable for imaging not possible currently. A pill, for instance, can contain a miniature video system. When the pill is swallowed, it moves through the digestive system and takes pictures every few seconds. The entire digestive system can be assessed for tumors, bleeding, and diseases in areas not accessible with colonoscopies and endoscopies.
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