If your drug use consists of an occasional aspirin, you may not see the need for serious work on drug delivery. But if you were diabetic, having to inject insulin several times a day, or a cancer patient experiencing debilitating side effects from your treatment, the benefits of improved drug delivery could change your life.
Perhaps the most publicized use of nanotechnology in drug delivery under development is the use of nanoparticles to deliver drugs to cancer cells. Particles are engineered so that they are attracted to diseased cells, which allows direct treatment of those cells. This technique reduces damage to healthy cells in the body.
However, that’s just the tip of the drug delivery iceberg: there are a number of other ways that nanotechnology can make the delivery of drugs more efficient and potentially less unpleasant for the patient. Some techniques are only imagined, while others are at various stages of testing, or actually being used today. The following survey of nanomedicine applications in drug delivery introduces many of these techniques.
Researchers are also continuing to look for more effective methods to target nanoparticles carrying therapeutic drugs directly to diseased cells. For example scientists are MIT have demonstrated increased levels of drugs delivery to tumors by using two types of nanoparticles. The first type of nanoparticle locates the cancer tumor and the second type of nanoparticle (carrying the therapeutic drugs) homes in on a signal generated by the first type of nanoparticle.
Two researcher groups have been focused on the best shape of nanoparticle to use for delivering drugs to cancer tumors. One research group has found that a disk shaped nanoparticle (nanodisk) will stick to the surface of a tumor longer than a spherical shaped nanoparticle, providing more efficient transfer of therapeutic drugs to the tumor. Another set of researchers have found that rod shaped nanoparticles are more effective at delivering chemotherapy drugs to breast cancer cells than spherical nanoparticles.
For more details see Nanoparticle Chemotherapy
Researchers are investigating the use of bismuth nanoparticles to concentrate radiation used in radiation therapy to treat cancer tumors. Initial results indicate that the bismuth nanoparticles would increase the radiation dose to the tumor by 90 percent.
A method to make radiation therapy more effect in fighting prostate cancer is using radioactive gold nanoparticles attached to a molecule that is attracted to prostate tumor cells. Researchers believe that this method will help For concentrate the radioactive nanoparticles at the cancer tumors, allowing treatment of the tumors with minimal damage to healthy tissue.
For more details see Nanoparticles in Cancer Radiation Therapy
Another technique delivers chemotherapy drugs to cancer cells and also applies heat to the cell. Researchers are using gold nanorods to which DNA strands are attached. The DNA strands act as a scaffold, holding together the nanorod and the chemotherapy drug. When Infrared light illuminates the cancer tumor the gold nanorod absorbs the infrared light, turning it into heat. The heat both releases the chemotherapy drug and helps destroy the cancer cells.
Targeted heat therapy is being developed to destroy breast cancer tumors. In this method antibodies that are strongly attracted to proteins produced in one type of breast cancer cell are attached to nanotubes, causing the nanotubes to accumulate at the tumor. Infrared light from a laser is absorbed by the nanotubes and produces heat that incinerates the tumor.
For more details see Nanoparticles in Cancer Heat Therapy
Researchers at North Carolina State University are developing a method to deliver cardiac stem cells to damaged heart tissue. They attach nanovesicles that are attracted to an injury to the stem cells to increase the amount of stem cells delivered to an injured tissue.
Researchers at the University of Georgia are working with nanoparticles that are both artificial HDL and contain a MRI contrasting agent (iron oxide). The researchers are now conducting animal studies to determine how well the artifical HDL treats arterial plaque.
Researchers are developing polymer nanoparticles that home in on inflamed tissue such as arterial plaque and dissolve, releasing drugs, in the presence of hydrogen peroxide that is present in the inflamed tissue.
More info on applications of Nanotechnology to Heart Disease
Drugs to treat glaucoma is being attached to nanodiamonds which are embedded in contact lenses. The drug molecules are released from the nanodiamonds are in contact with tears, providing a more consistent dosing than often occurs using eye drops.
Researchers are improving dental implants by adding nanotubes to the surface of the implant material. They have demonstrated to the ability to load the nanotubes with anti-inflammatory drugs that can be applied directly to the area around the implant. As well they have shown that bone adheres better to titanium dioxide nanotubes than to the surface of standard titanium implants.
Researchers have developed nanoparticles that release insulin when glucose levels rise. The nanoparticles contain both insulin and an enzyme that dissolve in high levels of glucose. When the enzyme dissolves the insulin is released. In lab test these nanoparticles were able to control blood sugar levels for several days.
Another method being developed to release insulin uses a sponge-like matrix that contains insulin as well as nanocapsules containing an enzyme. When the glucose level rises the nanocapsules release hydrogen ions, which bind to the fibers making up the matrix. The hydrogen ions make the fibers positively charged, repelling each other and creating openings in the matrix through which insulin is released.
A method being developed to tackle autoimmune diseases uses nanoparticles to deliver antigens for a particular disease into the blood stream. The antigens reset the immune system, stopping white blood cells from attacking healthy cells. This method has been tested in the lab on mice with a disease similar to multiple sclerosis with promising results.
Researchers are developing nanoparticles that can delivery drugs across the brain barrier to tackle neurologic disorders.
A method being developed to fight aging uses mesoporous nanoparticles with a coating that releases the contents of the nanoparticle when an emzyme found in aging cells is present.
Skin creams that uses proteins derived from stem cells to prevent aging of the skin. These proteins are encapsulated in liposome nanoparticles which merge with the membranes of skin cells to allow delivery of the proteins.
Researchers have developed a nanoparticle that can slip through mucus coating surfaces such as lung tissue. This ability to penetrate the mucus coating should provide the capability to coat lung tissue with therapeutic drugs.
Medical implants made of porous plastic, coated with carbon nanotubes. Therapeutic drugs, which are attached to the nanotubes can be released into the bloodstream, for example, when a change in the blood chemistry signals a problem. NASA is developing these implants, called a "biocapsule", to protect astronauts from the effects of radiation however the implants may also be useful for releasing insulin for diabetes patients or for delivering chemotherapy drugs directly to tumors.