"Corkscrew” microrobots skewer cancer cells for targeted drug delivery
In the not too distant future, tiny robots could be delivering drugs inside our bodies, but there are still a few hurdles to clear before we realize that scenario. Now researchers have developed corkscrew microrobots that drill into cancer and hold fast while they drop off the drug payload, preventing them being washed away by the flow of blood or other fluids.
Drugs are most effective if they’re delivered directly to the target tissue. But unfortunately the body is a dynamic environment and they can be dispersed, leaving them less effective on the targeted area and triggering unwanted side effects in healthy tissue. Chemotherapy drugs, for instance, are well known for wreaking havoc through the body.
In recent years, scientists have been experimenting with using microrobots to deliver drugs exactly where they’re needed. Inspired by everything from bacteria to scallops to submarines, these tiny bots swim, crawl or flip-flop through the body to get where they need to be, then deliver the drugs there – and only there.
In order to do that, microrobots need to stay in that place for a certain amount of time. But that can be a challenge in itself, since body fluids will often push them around. And this is the problem that a new study has tackled, thanks to researchers at Daegu-Gyeongbuk Institute of Science & Technology (DGIST) in the Republic of Korea.
Some previous microrobots are held in place using magnetic fields, applied by doctors from outside the body. But for the new study, the team designed a bot that could hold its own without requiring a magnetic field be sustained for long periods of time.
The new microrobot is shaped like a corkscrew, tipped with a needle. The outside is coated in layers of nickel and titanium oxide, which allow it to be guided magnetically. Drugs can then be loaded inside the needle, and into the pores of the corkscrew scaffold.
The idea is that doctors guide the robot to the desired location in the body using a magnetic field, and once it’s there it spears into the target cells, which may be things like cancer. That allows it to stay there until the delivery is complete.
The researchers tested the microrobots in fluid-filled chambers, directing them to attach to tissue samples. When manually manipulating the magnetic field, it took 55 seconds, but a specially designed automatic targeting system managed it in as little as 7 seconds.
Afterwards, the team found that it took flow speeds of 480 mm per second to dislodge the needle. That would work well in some places – small arterioles, for example, have flow speeds of about 100 mm per second – but larger veins and arteries can exert much more pressure.
In another experiment, the team tested the design out on human colorectal cancer cells. Sure enough, the microbots were able to target and kill the cells effectively.
While it’s still a long way off use in humans, the team says the next steps are to find ways to load more drugs onto the microrobots, and develop better control of the magnetic field to guide it.
The research was published in the Journal of Advanced Healthcare Materials.