Fluorescence microscopy images of tubular polymersomes, or plastic nanoparticles that can encapsulate drugs. (Credit: UNSW)

Scientists have developed a way to control the shape of polymer molecules so that they self-assemble into nonspherical nanoparticles — an advance that could improve the delivery of toxic drugs to tumors.

Researchers say the breakthrough means they can predictably make smart polymers that shift their shape according to the different conditions around them to form tiny ellipsoidal or tubular structures that can encapsulate drugs.

The scientists worked with polymer molecules that contain a water-soluble portion and a non-water-soluble portion, and which self-assemble into round, hollow structures, known as polymersomes, in solution.

The team’s novel chemical design is to add a non-water-soluble perylene polymer group to the membrane of the polymersome. The shape and size of the polymersome can then be adjusted by changing the amount of water in the solvent. The team used cryogenic-transmission electron microscopy to determine how the polymer molecules were packed together in solution.