Microscopic robots that deliver cancer-killing drugs to tumors could ‘revolutionize oncology’

STUTTGART, Germany — Magnetically controlled microscopic robots that kill cancer have been created by a team of scientists. The tiny machines swarm around tumors releasing a payload of chemotherapy drugs.

An army of bacterial “biohybrids” unleash hell on diseased cells, leaving healthy tissue alone. The microscopic robots could revolutionize oncology. Scientists harnessed the power of intestinal E. coli bugs — not the strain that causes sickness — equipping them with artificial components.

“Imagine we inject such bacteria-based microrobots into a cancer patient’s body,” says first author Birgul Akolpoglu, a PhD student at the Max Planck Institute in Stuttgart, in a statement. “With a magnet, we could precisely steer the particles towards the tumor. Once enough microrobots surround the tumor, we point a laser at the tissue and by that trigger the drug release. Now, not only is the immune system triggered to wake up, but the additional drugs also help destroy the tumor.”

Biohybrid microrobots
Figure 2: Schematic showing bacterial biohybrid microrobots magnetically guided through fibrous environments. Bacterial biohybrids can release their payload upon NIR irradiation. (Credit: Akolpoglu et al., Sci. Adv. 8, eabo6163 (2022).)

E. coli are the “superheroes” of the microbial world —  fast, versatile swimmers that can go through liquids or highly viscous tissues. They also have highly advanced sensors. Bacteria are drawn to chemical gradients such as low oxygen levels or high acidity, both prevalent near tumors. The German team loaded the vehicles with magnetic particles and spherical shaped carriers called liposomes that contain the medication.

In experiments, they were successfully steered through different courses to miniature tumors grown in the lab. They included an L-shaped channel with two compartments on each end, with one tumor “spheroid” in each and an even narrower set-up resembling blood vessels. The microbots even travelled through a thick collagen gel resembling cancerous tissue with three levels of stiffness and porosity, ranging from soft to medium to stiff.

Once they added a magnetic field, the bacteria manage to navigate all the way to the other end as it had a higher force. At their destination, a near infrared laser generated rays with temperatures of up to 55 degrees Celsius. It melted liposome and released the enclosed drugs. A low acidic environment also causes the proteins to break so they open near a tumor automatically.

Bacterial biohybrids
Figure 1: Bacterial biohybrids carrying nanoliposomes (200 nm) and magnetic nanoparticles (100 nm). Nanoliposomes are loaded with chemotherapeutic DOX and photothermal agent ICG, and both cargoes are conjugated to E. coli bacteria (2 to 3 µm in length) via biotin-streptavidin interactions. (Credit: Akolpoglu et al., Sci. Adv. 8, eabo6163 (2022).)

“This on-the-spot delivery would be minimally invasive for the patient, painless, bear minimal toxicity and the drugs would develop their effect where needed and not inside the entire body,” says study co-author Dr. Yunus Alapan.

Over the past decade, scientists have manipulated magnetic forces to guide medical devices inside the human body, including a heart catheter and gut video capsules.

“Bacteria based biohybrid microrobots with medical functionalities could one day battle cancer more effectively. It is a new therapeutic approach not too far away from how we treat cancer today,” adds co-author Dr. Metin Sitti. “The therapeutic effects of medical microrobots in seeking and destroying tumor cells could be substantial. Our work is a great example of basic research that aims to benefit our society.”

The research is published in the journal Science Advances.

Report by South West News Service writer Mark Waghorn.

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