Tumors that travel to the lungs, or lung metastases, pose a formidable challenge in the realm of cancer treatment. Conventional chemotherapy often falls short because it’s inefficient. It doesn’t directly target the lungs and accumulate in a high enough concentration to kill tumors.

Algae drug delivery

Synthetic microrobots are typically made of rigid metallic or polymeric structures that are difficult to manufacture. They’re unable to access certain organs and tissues, and they can be toxic to humans.

Microalgae overcome these concerns. For one, microalgae can move autonomously by using a hair-like appendage called flagella to propel themselves through organs such as the lungs. They are less toxic compared with other microorganisms. They are also cheaper and easier to produce.

Our biohybrid microrobot – called algae-NP(DOX)-robot – combines microscopic, live green microalgae commonly used in pharmaceuticals, Chlamydomonas reinhardtii, with nanoparticles coated with red blood cell membranes. The cell membranes act as a natural “camouflage” to enhance the microrobot’s biocompatibility and prevent it from being attacked by the patient’s immune system. Within the nanoparticles is a common type of chemotherapy drug called doxorubicin.

We tested our algae-based microrobots in mice with lung metastases. By administering these algae-based microrobots through the trachea, we could transport the drug directly into the lungs and minimize side effects to other organs. Once in the lungs, our algae-based microrobot could swim and distribute the drug across lung tissue. It could also evade destruction by immune cells in the lungs, allowing the drug to be gradually released from the nanoparticles.