Chemotherapy is one of the most common and most powerful forms of cancer treatment. However, chemotherapy drugs not only kill cancer cells, they can also wreak havoc on the rest of the body. Administering drugs directly to cancer cells could help reduce these unpleasant side effects of chemotherapy.
In a proof of concept study, researchers developed fish-shaped microrobots magnetically driven to the cancer cell to release an active chemotherapy ingredient. Because tumors exist in acidic microenvironments, the team built microrobots that can change shape in response to lowering pH.
Curative microrobot transformer
Microrobots consist of a 3D printed pH-sensitive hydrogel and come in different shapes - a crab, butterfly or fish. The team coded the morphing of the pH-sensitive shape by adjusting the print density in certain areas of the shape, such as the edges of the crab's claws or the fish's mouth, so that they can open or close in response to changes in acidity. Then, they made the microrobots magnetic by placing them in a suspension of iron oxide nanoparticles.
In laboratory tests, the researchers showed various capabilities of the microrobots in different tests. For example, the fish-shaped microrobot has an adjustable "mouth" that encapsulates the drug in a saline solution and releases it by opening the mouth when in a slightly acidic environment. The team showed they could guide the fish through simulated blood vessels to reach cancer cells in a specific region. When they lowered the pH of the solution, the fish opened their mouths to release the chemotherapy drug, which killed nearby cells.
Next step: little ones!
Although this study is very promising, microrobots need to be made even smaller to navigate real blood vessels, and a suitable imaging method needs to be identified to track their movements in the body, the researchers say. With continued optimization of size, motion control and imaging technology, these shape-transforming magnetic microbots will provide ideal platforms for complex drug delivery operations.