Cancer is one of the biggest killers in the world. Every year it takes more than 8 million lives which amounts to approximately 50% of the amount diagnosed with the disease. The most unfortunate is the suffering that the patient and the family has to go through. This is primarily due to the side effects of chemotherapy drugs and related treatments.
The disease form tumors in tissues or in body flow system as a result of abnormal cell growth caused by DNA damage. Although, there is a debate, it’s generally believed that cancer is caused by genetic and environmental reasons. Surgery, chemotherapy and radiation treatment are among the most used conventional cancer treatment methods. Surgery is quite effective if the cancer is identified at the initial stage. Chemotherapy uses drugs to battle malignant cancer cells and quite widely used in treatment of both early and advanced stages of cancer. Radiotherapy use ionizing radiation such as X-Rays and gamma rays to kill remaining cancer cells after chemotherapy and/or surgery treatment.
Chemotherapy is at the heart of any conventional cancer treatment procedure. It has been used quite effectively and the efficiency and the specificity of the drugs to the cancer cells have been increased over the years. However, chemotherapy drugs still greatly lacks the ability of specifically target only the cancer cells. When conventional chemotherapy drugs are injected in to the blood stream they will be distributed across the body attacking both cancer and normal cells. This can set off various side effects depending on the type of the cancer, location of the tumor, type of the drug, dosage and the general health of the patient. The side effects can range from headaches to painful mouth sores, to permanent damage to vital organs in the body.
Nanobot to deliver the cancer drug
It’s quite right to say, developing a drug system that only target cancer cells while leaving healthy cells unharmed is the holy grail of cancer research. Two years back a group of scientists from Harvard’s Wyss Institute made a huge advancement towards this goal by designing and fabricating a nanobot that can autonomously target a cancer cell and deliver a payload of chemotherapy drugs.
Some of you may be used to the idea of nanobots from the 2009 movie, G.I Joe where cobra commandos tried to destroy the world with a warhead containing deadly nanobots called “Nanomites”. However, the nanobots, developed at Harvard are much simpler, and instead of killing, it was designed to save lives. It’s so simple and you wouldn’t believe that to be a machine at the first sight. The device is extremely small and only 35 nanometers in width. To make this length in to a perspective; it’s around 200 times smaller than a red blood cell.
The fabricated nanobot looks like a nanocage similar to an open ended barrel. This molecular barrel has two halves which can open and close in a manner much similar to a clamshell. These two halves are connected to each other by molecular hinges and kept close by two molecular locks or latches that are actually made of DNA double halixes. The chemotheraphy drug can be encaged in to the barrel core and secured by molecular anchors inside the nanocage. To do this scientists need to modify the drug molecule with a linker strand, again made with short strand of DNA molecule. Drug loading is carried out simply by mixing the nanobots and the drugs together. Chemotherapy drug simply diffuse in to the inner structure of the nanocage as a result of the mutual attraction between the linker strand and the molecular anchors inside the nanocage.
Scientists at Wyss institute have used DNA molecules to fabricate this nanobot using a technique called DNA origami. It is a popular method used by scientists to make nanoscale objects that are atomically precise. In the process, scientists mix small amount of long single stranded, template forming DNA with relatively large amount of pre designed short stranded DNAs which will undergo self-assembly to make an intricate nanoscale structures with desired shapes.
Logical programing at molecular stage
The real ingenuity of the discovery is in the DNA latches. Our ability to program these latches to open for a specific ligand or a marker is what makes this sophisticated nanocage in to a nanobot. In the absence of the key, the DNA duplexes that function as latches are held sufficiently strong to keep the entire nanocage closed. However, when a specific biomarker is present, specially designed DNA binds with the biomarker key, unzipping the DNA duplex. When both these DNA latches are opened, entire structure will open up delivering the drug. This works much similar to a combination lock, but at the molecular stage.
Cancer cells are slightly different from healthy cells when the surface chemistry of the cell wall is considered. They have special molecular proteins that are not present in healthy cells. Scientists exploit this property and program DNA latches of the nanobot only to open when these markers or keys are present. This allows the nanobot to specifically attack small population of target cells that lives within a large population of other cells, which should be left alone. This is only possible because only those target cells express the correct set of keys that open up the nanocage releasing the toxins.
Scientists at Wyss institute have tested these medical nanobots in experimental cell lines and in animal models. They have made different variations of these nanobots having unique set of locks appropriately designed for different cancer types. By mixing the cancer cells and nanobots together they have demonstrated that nanobots can target specific cell lines depending on locks that was selected. There was almost zero collateral damage to other by standing cells.
This type of smart molecular device has a great potential not only as a nanotechnology cancer treatment method but also as a medical nanotechnology application for diagnosis and imaging. This DNA nanobot cancer treatment system has been developed to identify 12 different types of human cancers including leukemia; a notorious type of cancer involving cancer growth in bone marrow. A patient was identified to test this novel drug delivery system who has given few more months to live by the doctors. However, the group of scientists who developed the nanobot cancer therapeutic system is confident that they can target and eliminate the cancer within a month. Let’s just hope them good luck with their experiment!
DNA Nanorobots: A New Method For Treating Cancer, by Brandon Tomlin (personal blog post by one of the scientists involved in the project)