Microalga with attached spherical cargoes

A swimming algal cell (green) is bedecked with spherical cargo carriers (red) that can be loaded with drugs. Credit: O. Yasa et al./Adv. Mater.

Biomaterials

Bionic algae barrel through blood to deliver drugs

Plant cells pressed into service as swift and biodegradable couriers.

Swimming algae have been enlisted to carry drugs to individual cells, raising the prospect that such ‘microswimmers’ could deliver targeted therapies.

Miniscule devices propelled by living organisms can ‘swim’ through the body to deliver cargo such as doses of drugs. A variety of organisms have been joined with artificial structures to treat some tumours, but the most commonly used organisms — bacteria — can be toxic and multiply rapidly, limiting their use.

As an alternative, Metin Sitti and his colleagues at the Max Planck Institute for Intelligent Systems in Stuttgart, Germany, tested the freshwater alga Chlamydomonas reinhardtii. Nontoxic and biodegradable, it moves by lashing a propeller-like tail. The researchers outfitted individual algal cells with magnetic polymer beads that could hold drugs in small amounts and allowed the researchers to steer the algae by applying a magnetic field to them.

In the lab, these microswimmers darted through bodily fluids such as blood at more than 100 micrometres per second and successfully deposited payloads onto mammalian cells. The authors plan future in vivo tests to determine the microswimmers’ compatibility with the human immune system.