Posted: August 17, 2010

Porous silica nanoparticles deliver anticancer therapy

(Nanowerk News) In cancer research, nanotechnology holds great promise for the development of targeted, localized delivery of anticancer drugs, in which only cancer cells are affected. By carrying out comprehensive studies on mice with human tumors, scientists at the University of California, Los Angeles, have obtained results that move the research one step closer to this goal.
In a paper published in the journal Small ("Biocompatibility, Biodistribution, and Drug-Delivery Efficiency of Mesoporous Silica Nanoparticles for Cancer Therapy in Animals"), Fuyuhiko Tamanoi and colleagues demonstrated that mesoporous silica nanoparticles (MSNs), can store and deliver chemotherapeutic drugs in vivo and effectively suppress tumors in mice. The investigators also showed that MSNs accumulate almost exclusively in tumors after administration and that the nanoparticles are excreted from the body after they have delivered their chemotherapeutic drugs.
In the study, Dr. Tamanoi and his colleagues found that MSNs circulate in the bloodstream for extended periods of time and accumulate predominantly in tumors. The tumor accumulation could be further improved by attaching a targeting moiety to MSNs, the researchers said.
Treating mice with camptothecin-loaded MSNs led to shrinkage and regression of xenograft tumors. By the end of the treatment, the mice were essentially free of tumors, and acute and long-term toxicity of MSNs to the mice was negligible. Mice with breast cancer were used in this study, but the researchers have recently obtained similar results using mice with human pancreatic cancer.
Two properties of these nanoparticles proved important in creating this promising anticancer therapy, according to the investigators. First, these nanoparticles appear to evade the surveillance mechanism that normally removes materials foreign to the body, enabling the nanoparticles to accumulate in tumors. Second, most of the nanoparticles that were injected into the mice were excreted out through urine and feces within four days. The latter results, say the investigators, was somewhat of a surprise and might explain the low toxicity observed in the biocompatibility experiments they conducted.
Source: National Cancer Institute