Developed by engineers at the University of California San Diego, the approach has shown promise in mice where it inhibited the growth and spread of tumours that had metastasised to the lungs. The findings are detailed in a paper published in Science Advances.
The microrobots, which combine biology and nanotechnology, are a joint effort between the labs of Joseph Wang and Liangfang Zhang, both professors in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at the UC San Diego Jacobs School of Engineering.
To create the microrobots, the researchers chemically attached drug-filled nanoparticles to the surface of green algae cells. The algae enable the nanoparticles to efficiently swim around in the lungs and deliver their therapeutic payload to tumours.
The nanoparticles are made of biodegradable polymer spheres, which are loaded with the chemotherapeutic drug doxorubicin and coated with red blood cell membranes.
This coating protects the nanoparticles from the immune system, allowing them to stay in the lungs long enough to deliver their anti-tumour effects.
In a statement, Zhengxing Li, PhD student and study co-first author, said: “This coating makes the nanoparticle look like a red blood cell from the body, so it will not trigger an immune response.”
This formulation of nanoparticle-carrying algae is safe, the researchers said. The materials used to make the nanoparticles are biocompatible while the green algae employed, Chlamydomonas reinhardtii, are recognised as safe for use by the US Food and Drug Administration.
For this study, mice with melanoma that had metastasised to the lungs were treated with the microrobots, which were administered to the lungs through a small tube inserted into the windpipe.
Treated mice are said to have experienced a median survival time of 37 days, an improvement over the 27-day median survival time observed in untreated mice, as well as mice that received either the drug alone or drug-filled nanoparticles without algae.
“The active swimming motion of the microrobots significantly improved distribution of the drug to the deep lung tissue, while prolonging retention time,” said Li. “This enhanced distribution and prolonged retention time allowed us to reduce the required drug dosage, potentially reducing side effects while maintaining high survival efficacy.”
Looking ahead, the team is working on advancing this microrobot treatment to trials in larger animals, with the goal of human clinical trials.
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