A significant development in the treatment of cancer was the pairing of siRNA (small interfering RNA) treatments with nanoparticle delivery. In 1999, siRNA was first described as a novel means of inhibiting protein expression in cells. However, the RNA strands were often destroyed by cellular mechanisms before reaching their targets. Nanoparticles provide the protection and delivery mechanisms siRNA molecules need to reach target tissues. Several companies have already entered clinical trials of nanoparticles-delivered siRNA therapies (Alper 2006).
Molecular self-assembly is the phenomenon through which molecules assemble spontaneously into defined, stable formations based on atomic interactions such as hydrogen bonding, hydrophobic and van der Waals forces. “Bottom-up” construction of nanoparticles takes advantage of molecular self-assembly to build specific structures based on our understanding of these spontaneous formations. One application of this is to use the specificity of Watson-Crick DNA base pairing to build nucleic acids of defined structures with particular uses. In another novel application of molecular self-assembly, under development in Switzerland, pore proteins are introduced into nanoparticles during polymer assembly. The pores are incorporated into the surface matrix, and their opening and closing allow drug delivery specific to certain environmental conditions (in this case pH changes) in the cell (Broz et al. 2006). Pores often open or close as they react to pH, temperature or other environmental factors. Use of similar pores in nanoparticles allows specific delivery or biosensing under specific cellular conditions, for example, insulin delivery when blood sugar levels indicate a need.
Following payload delivery, it is often desirable for the nanoparticles to somehow be removed or metabolized, ideally without any toxic side effects. Indeed, the advantages to using nanoparticles are that toxic side effects of traditional radiation and chemotherapies can be avoided, by treating only the tumor, or unhealthy, cells and not damaging nearby healthy tissue. Some nanoparticles are expected to be relatively safe because of their propensity to dissolve once inside cells, and some consist of materials that are already in use in biomedicine, such as nanoparticles made from the same polymers as are used for sutures (Bullis, 2006). Whatever the approach, the benefits of nanoparticle delivery are enormous and include improved bioavailability of drugs by targeting specific organs, tissues or tumors, thereby providing the highest dose of drug directly where it is needed, and reducing waste and costs due to breakdown prior to a drug meeting its target.
Nanomedicine is a relatively new area of biotechnology, but the possibilities for new therapies and surgeries to treat illnesses and diseases such as cancer, seem endless. The concept of nanorobots and cell repair machines is also viable and may some day be as commonplace as taking an asprin is today.
Sources:
Kim, 2007. Nanotechnology platforms and physiological challenges for cancer therapeutics. In Press, doi.org/10.1016/j.nano.2006.12.002.
Alper, 2006, Nanoparticles and siRNA – Partners on the pathway to new cancer therapies. NCI Alliance for Nanotechnology in Cancer. http://nano.cancer.gov/news_center/monthly_feature_2006_august.asp.
Broz et al., 2006. Toward intelligent nanosize bioreactors: A pH-switchable, channel-equipped, functional polymer nanocontainer. Nano Letters 6(10): 2349-2353.
Bullis, 2006. Single-Shot Chemo. Technology Review. http://www.technologyreview.com/read_article.aspx?ch=specialsections&sc=emergingtech&id=16469.
