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Scientists use magnets to deliver cancer-killing 'micro-robots' into the body

Interesting Engineering
Interesting Engineering
 2022-11-12
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Cancer-killing bacteria

Scientists have conceived of a new way to deliver cancer-killing compounds, called enterotoxins, to tumors using bionic bacteria that are steered by a magnetic field, according to a report by Inverse published last week.

These bacteria function as “micro-robots” that can hunt down and rally around a specific tumor. They then release their own naturally produced anti-cancer chemicals and shrink the tumor.

“Cancer is such a complex disease, it’s hard to combat it with one weapon,” said Simone Schürle-Finke, a micro-roboticist at the Swiss Federal Institute of Technology in Zürich, Switzerland, and one of the authors of the new study.

Schürle-Finke further added that once these newly-engineered microbes reach a tumor, “you basically have a little nano-factory that continues to release molecules that can be toxic to cancer cells.”

An exciting new idea

The researcher came up with the idea of using magnets to guide bacteria when thinking about how inoperable some tumors are because of their inaccessible locations. But there weren’t many bacteria that could be controlled by magnets to reach those destinations.

However, one special group of aquatic bacteria did have this special quality: magnetotactic bacteria. The bacteria use tiny iron crystals produced in their bodies like an internal compass making them susceptible to being guided by a magnetic force.

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The tiny robots consist of bacteria. Dr_Microbe/iStock

To test the capacity of these creatures to target cancer cells, Schürle-Finke’s team equipped the bacteria with fluorescent tags and nanoparticles filled with drugs. The result was genetically engineered bacterial robots whose nanoparticles could propel them to release cancer-fighting compounds on cue.

Tested on cancerous mice

Then, they tested the robots on cancerous mice by injecting the bacteria bots into them. They further used an externally generated magnetic field to direct the bacteria toward the mice’s tumors. They were able to achieve this goal with more than three times the precision of the control group which was not exposed to any magnetic field.

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The invention, although exciting, is not entirely new. In November of 2021, researchers created a new way of moving chemotherapy drugs to the site of cancer cells with microbots.

The innovation was said to substantially enhance cancer treatment because it enabled the direct injection of chemo drugs into the cancerous cells.

The tiny microbots developed were guided to their goal (in this case, cancer cells) via magnets. Once there, they released the drug payload.

Composed of 3D-printed hydrogel in the shape of various animals (including a butterfly, crab, and fish), the little robotic critters exhibited gaps on the inside where engineers could stuff particles.

In April of 2022, researchers engineered a slimy turd-like robot powered by magnets that they said could one day be used to grab things from inside the body.

It consisted of a mixture of a polymer called polyvinyl alcohol, borax, and particles of neodymium magnets responsible for the magnetic attraction that leads to the slime's movements.

The new study was published in the journal Science.

Study abstract:

Biohybrid bacteria–based microrobots are increasingly recognized as promising externally controllable vehicles for targeted cancer therapy. Magnetic fields in particular have been used as a safe means to transfer energy and direct their motion. Thus far, the magnetic control strategies used in this context rely on poorly scalable magnetic field gradients, require active position feedback, or are ill-suited to diffuse distributions within the body. Here, we present a magnetic torque–driven control scheme for enhanced transport through biological barriers that complements the innate taxis toward tumor cores exhibited by a range of bacteria, shown for Magnetospirillum magneticum as a magnetically responsive model organism. This hybrid control strategy is readily scalable, independent of position feedback, and applicable to bacterial microrobots dispersed by the circulatory system. We observed a fourfold increase in translocation of magnetically responsive bacteria across a model of the vascular endothelium and found that the primary mechanism driving increased transport is torque-driven surface exploration at the cell interface. Using spheroids as a three-dimensional tumor model, fluorescently labeled bacteria colonized their core regions with up to 21-fold higher signal in samples exposed to rotating magnetic fields. In addition to enhanced transport, we demonstrated that our control scheme offers further advantages, including the possibility for closed-loop optimization based on inductive detection, as well as spatially selective actuation to reduce off-target effects. Last, after systemic intravenous injection in mice, we showed significantly increased bacterial tumor accumulation, supporting the feasibility of deploying this control scheme clinically for magnetically responsive biohybrid microrobots.

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