They’re the first nanomedicine to progress from concept to the clinic, and now scientists are using these microscopic “bubbles” as a kind of heat-seeking grenade to make tumor cells explode.
You may not have heard of liposomes, but these tiny little fatty spheres have great potential for the field of nanomedicine. Invented back in the '60s, they consist of a closed spherical membrane that scientists can stuff with drugs or gene medicines and guide to specific areas of the body, allowing the targeted delivery of a high dose of therapeutic molecules.
So how do scientists get the drugs to the right area? This is an ongoing challenge for modern medicine, especially with cancer treatments that can have off-target effects. That’s largely because many are designed to attack any rapidly dividing cells, a hallmark of cancer, which unfortunately also includes things like hair follicles and cells in the stomach and bowels, hence the unpleasant side effects.
To get round this problem, researchers behind a new investigation, based at the University of Manchester, created liposomes that would only release their therapeutic payload at a certain temperature – 42 degrees Celsius (107.6 degrees Fahrenheit). That’s five degrees warmer than the normal human body temperature, so they shouldn’t blow their cargo prematurely and in the wrong place.
“Once they reach a ‘hotspot’ of warmed-up cancer cells, the pin is effectively pulled and the drugs are released,” study author Kostas Kostarelos said in a statement. “This allows us to more effectively transport drugs to tumors, and should reduce collateral damage to healthy cells.”
But such an increase in temperature isn’t a unique characteristic of tumors; rather, the scientists themselves warm them up. So far they’re tried it on lab samples and mice with models of human cancer, but the researchers say that there are techniques out there that could potentially be used in human patients, some of which are already in clinical use. The work is currently unpublished but is due to be presented at the National Cancer Research Institute Cancer Conference this week.
This isn’t the only promising technique for targeted delivery of chemotherapy-loaded liposomes, though. Scientists have also been trying to use light, enzymes, and specific pH levels as triggers, but many attempts have been unsuccessful so far. One method that could potentially turn out to be useful involves attaching cancer-specific antibodies to the liposomes, but research is still in its infancy at the moment.