Nanomedicine continues to show promise of developing innovative and effective techniques for combating cancer. The great benefit of most of these treatments is that they attack malignant tumors and cells directly without damaging healthy tissue. This is a welcome contrast to traditional chemotherapy treatments that damage healthy and cancerous tissue alike.
Tumors need a blood supply to grow and this is proving to be a weakness that researchers in nanomedicine are finding ways to exploit. Researchers at the University of Iowa developed a method for introducing chemotherapy drugs directly into a tumor through nano-sized holes in the blood vessels that feed the tumor. Now, researchers at Arizona State University and the National Center for Nanoscience and Technology of the Chinese Academy of Sciences are using nanorobots to target tumors and choke off their blood supply. Their work was reported in the journal Nature Biotechnology.
How it works
The nanorobot is made from a flat DNA sheet that measures 90 nanometers by 60 nanometers. A nanometer is a billionth of a meter; for comparison, human hair ranges from 80,000 to 100,000 nanometers in diameter. Molecules of thrombin, an enzyme that causes blood clotting, are attached to the surface of the sheet. The sheet is then rolled into a tube with the thrombin inside.
DNA aptamers that seek out a protein called nucleolin are attached to the surface of the tube. Nucleolin is typically present in endothelial cells on the surface of tumors and is not present on the surface of healthy cells.
The DNA aptamers seek out nucleolin and attach to the surface of a tumor. The nanorobot appears benign to the tumor because the thrombin is hidden inside. The nanorobot penetrates a blood vessel that feeds the tumor and then unrolls releasing the thrombin molecules. The thrombin kicks off a clotting process that reduces blood flow and starves the tumor.
How it was tested
An IV was used to inject the nanorobots into the bloodstream of mice with breast cancer, melanoma, ovarian or lung cancer tumors. Within hours the nanorobots had located and surrounded the tumors. Within 24 hours, tissue damage that resulted from blocking the blood supply was observed, and the nanorobots had degraded and become nonfunctional. Advanced blood clotting (thrombosis) was observed after 48 hours and blood clots in all tumors were observed after 72 hours. Three of the eight mice that had melanoma showed complete regression of the tumors. Studies with Bama miniature pigs produced equivalent results.
The nanorobots were clearly successful in attacking the cancerous tumors, but if they also attack healthy tissue, the consequences for human patients could be more severe than standard chemotherapy treatments. That does not appear to be a concern. Mice and Bama pigs without tumors were injected with the nanorobots and showed “no detectable changes in normal blood coagulation or cell morphology” according to Dr. Yuliang Zhao, one of the lead researchers on the study.
Of course, it’s early days, but this research is very encouraging for several reasons. First and foremost, the nanorobots successfully attacked malignant tumors without harming healthy tissue. The fact that the treatment worked with both mice and Bama pigs demonstrates that its effects are not limited to smaller mammals. Finally, the effectiveness of the treatment against a wide variety of cancers holds great hope for the future. Tumors need a blood supply and using nanomedicine techniques to target that blood supply may be an effective way to kill the tumor without harming the patient.
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