Now that nanotech researchers know it is possible to target tumors with drug-carrying nanoparticles, the challenge is to get those little carriers to stick around the tumor for a while and bombard it with as much of the therapy as possible.
A research team at Boston University has developed a nanoparticle that responds to the acidic pH inside tumor cells by expanding, releasing the anticancer agent paclitaxel slowly over a period of 24 hours. Tests with these new nanoparticles demonstrated that they not only decreased tumor growth, but prevented new tumors from implanting themselves in the abdominal cavity.
This could be especially useful, researchers say, for patients with ovarian cancer or mesothelioma who develop metastases that spread within the abdominal cavity. When that happens, chances of surviving beyond five years drops to less than 40 percent even after surgical removal of the metastatic tumors.
Mark Grinstaff led the research team that published its work in the journal Biomaterials. Investigators from Brigham and Women's Hospital also participated in this study. The investigators set out to create a nanoparticle that would release paclitaxel only when taken up by tumors, release drug slowly to maximize the number of dividing cells exposed to the drug, and that would remain in the vicinity of the tumors while it released the drug. They created a material that remains intact but swells when it's in the low pH environment near tumor cells. Tests with paclitaxel-loaded nanoparticles showed that they release about 4 percent of their drug load each hour for 24 hours, creating a sustained load of drug in the vicinity of the nanoparticle. When added to mesothelioma cells growing in culture, the drug-loaded nanoparticles continued to substantially kill cells.
Other experiments conducted by the investigators showed that when injected into the abdominal cavity, the drug-loaded expandable nanoparticles homed to tumor sites and remained there for at least seven days.