WHY NANOPARTICLES?
Cancer is one of the most difficult to fight diseases in the world, and the mortality rates continue to rise. The market standard anti-cancer drug performs adequately but may do some long-lasting damage to your body. Some of this damage can eventually cause the death of patients. Nanoparticles possess properties that make them better suited for anti-cancer treatment than today’s product. In fact, almost all of the nanoparticles listed in Table 1 have been used with an anti-cancer drug of some kind.
NPs have the ability to trigger drug release in creative ways, such as targeted heating or the flipping of magnetic fields. Some of these ways are invasive, but some are not. Yet all of the methods used are able to pinpoint the NPs and deliver the drugs in an effective manner.
The primary reason that nanoparticles are taking over the anti-cancer drug market is due to their ability to directly target cells. There are multiple ways in which tumor cells can be found. Some tumors grow rapidly, and this gorwth produces low pH levels that can be utilized for detection and drug release. Other tumors have known receptors that can be targeted by NPs. Chemotherapy drugs are extremely harmful to all cells that they come into contact with, so targeting only the cancerous tumor cells would be advantageous to patients. He and Shi say that “it has been frequently said that cancer patients died more from poisonous chemotherapeutic drugs, than from cancers.”
NPs have the ability to trigger drug release in creative ways, such as targeted heating or the flipping of magnetic fields. Some of these ways are invasive, but some are not. Yet all of the methods used are able to pinpoint the NPs and deliver the drugs in an effective manner.
The primary reason that nanoparticles are taking over the anti-cancer drug market is due to their ability to directly target cells. There are multiple ways in which tumor cells can be found. Some tumors grow rapidly, and this gorwth produces low pH levels that can be utilized for detection and drug release. Other tumors have known receptors that can be targeted by NPs. Chemotherapy drugs are extremely harmful to all cells that they come into contact with, so targeting only the cancerous tumor cells would be advantageous to patients. He and Shi say that “it has been frequently said that cancer patients died more from poisonous chemotherapeutic drugs, than from cancers.”
SOLVING PROBLEMS USING NANOPARTICLES
There are three main problems that researchers, doctors, and pharmaceutical companies face when dealing with anti-cancer drugs: severe toxic side effects of the drugs, multi-drug resistance, and metastasis.
1. Toxic Side Effects
Standard chemotherapy drugs on the market today kill normal cells and suppress immune systems along with cancer cells. To help reduce these side effects, researchers have begun to use NPs in a variety of ways. One of the main ways to combat this suppression is to use a NP like MSN and increase the dosage of the drug. The interconnected pores make the increased dosage a nonissue. Other ways to combat the side effects include the specific targeting of tumor cells. Picking up on one of the tumor spotting methods mentioned earlier, ligands, or necessary molecules are bound to the surface of the NP and expected to actively or passively target the tumor. Some receptors can be over-expressed, and they can become targets for these NPs.
As time moves on, the ultimate goal of killing cancer cells is to get the nucleus of the tumor. Nuclei are usually open complexes, so all that needs to be done is get a small enough, but effective, NP into one of them. When inside the nucleus of a tumor, the payload can be delivered, and the cancer cells will die.
2. Multidrug Resistance
It is said that up to 90% of tumor patients die in some way relating to MDR, or Multidrug Resistance. It is an ever-present problem that will continue to grow as drugs get more effective. It works using simple survival of the fittest. After the first wave of chemotherapy, the cancer cells still left behind have a better resistance to the drug used. When the cancer begins to return, the cancerous cells will have a better resistance to the original chemo drug as well as drugs that work of a similar delivery mechanism. Research is being done to increase the effectiveness against MDR.
MDR can be overcome by considerably upping the dosage of each drug. Again, this can lead to complications when using a harmful anti-cancer treatment. Some researchers have suggested ideas that use passive and active targeting, as well asdirect injection of treatment into the affected areas. Multiple drugs are delivered using the same nanoparticle in hopes of confusing the target cells. A common combination is a chemotherapeutic drug coupled with an ABC transporter.
3. Metastasis
“Metastasis is defined as the ability of tumor cells to invade local tissues at the primary site and to traverse basement membranes and tissue barriers to re-establish at distant secondary sites. When malignant tumors are first diagnosed, more than 60% of them have been in the progression of metastasis, namely the formation of secondary tumor(s) in distant organs, while other tumor patients are also subject to tumor metastasis during treatment and even after first recovery for several years. Therefore, tumor metastasis is one of the most vital causes resulting in the high mortality of cancer patients.” (He and Shi)
Currently there is very little work being done to prevent or inhibit metastasis, or the spreading of cancerous cells. There is also little research done to fully understand or model metastatic tumors. Ideally, doctors hope to catch metastasis in one of the earlier stages of its process to stop it before it ever becomes a problem.
Nanoparticles and medical imaging
Nanoparticles have an extremely versatile set of properties that range from diagnostic to therapeutic. Imaging technology has kept up in the race with nanotechnology because of its utility. Diagnosing problems is just as important as solving them. Nanoparticles can both diagnose and treat diseases at the same time; this dual ability is called “theranostics”. Some theranostic NPs include liposomes, emulsions, and nanogels.
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The bulk of research in this area is conducted with liposomes due to their size control properties, biocompatibility, and loading capacity with hydrophilic and hydrophobic drugs. Liposomes are often hybridized with another nanoparticle or material that allows them to improve various in vivo qualities or be better imaged.
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Conclusions
Nanoparticles allow for a greater range of benefits for drug delivery and therapy. One of the largest portions of nanomedicine research is focused on anti-cancer drugs, since the targeting capabilities of nanoparticles make them extremely versatile for anti-cancer medicine. As research continues, current problems with cancer treatment will be solved. Nanoparticle drug delivery will help save the lives of cancer patients around the world while lowering the price of treatment.
SOURCES:
He, Q., & Shi, J. (2014). MSN Anti‐Cancer Nanomedicines: Chemotherapy Enhancement, Overcoming of Drug Resistance, and Metastasis Inhibition.Advanced Materials, 26(3), 391-411.
Park, J. H., Cho, H. J., Yoon, H. Y., Yoon, I. S., Ko, S. H., Shim, J. S., ... & Kim, D. D. (2014). Hyaluronic acid derivative-coated nanohybrid liposomes for cancer imaging and drug delivery. Journal of Controlled Release, 174, 98-108.
Minko, T., Rodriguez-Rodriguez, L., & Pozharov, V. (2013). Nanotechnology approaches for personalized treatment of multidrug resistant cancers.Advanced drug delivery reviews, 65(13), 1880-1895.
Bamrungsap, S., Zhao, Z., Chen, T., Wang, L., Li, C., Fu, T., et al. (2012, January 1). Nanotechnology in Therapeutics. . Retrieved July 21, 2014, from http://www.medscape.com/viewarticle/770397_1