Scientists have assembled tiny biological robots, dubbed "anthrobots," entirely from human cells that demonstrate the ability to promote neuron growth in cell cultures. This innovative development brings medicine one step closer to a future where miniaturized living robots could be deployed inside the body to help heal injuries.
Background on Xenobots and Biobots
The anthrobots originate from an emerging field of synthetic biology focused on constructing tiny biological robots, or biobots. In 2020, researchers from Tufts University and the University of Vermont announced the creation of xenobots – biobots assembled from the stem cells of the African frog Xenopus laevis.
These millimeter-sized xenobots could move around, work together in groups, and demonstrate self-healing abilities. While promising, there were concerns over introducing frog cells inside the human body.
The new research from a team at Harvard University sidesteps this barrier through the use of human cells to construct biobots, paving the way for their safe use in medical therapies.
How the Human Cell Anthrobots Were Assembled
The Harvard team built their anthrobots using two of the most abundant cell types found in the human trachea – tracheal basal stem cells and tracheal secretory cells. Rather than harnessing stem cells, they relied on the natural ability of differentiated adult human cells to remain plastic and reconfigure themselves into new arrangements.
By using specialized micropatterning techniques to adhere the cells to formed shapes, they coaxed the tracheal cells to self-organize into simple cell structures and more complex folded assemblies over the course of days.
The team tested 50 different cell arrangements before landing on the optimal anthrobot design of basal stem cells on the outside enveloping secretory cells on the interior. This configuration provided maximum speed, control, and longevity.
| Cell Type | Role in Anthrobot |
|---|---|
| Tracheal basal stem cells | Outer cell layer providing structure and mobility |
| Tracheal secretory cells | Inner cell mass offering longevity and control |
The anthrobots measure about half a millimeter in diameter – small enough to be injected through a standard needle. Their human cell composition makes them well-suited for medical use inside the body.
Anthrobots Show Promise For Healing Neurons
A critical experiment tested whether the anthrobots could promote regeneration in neuron cells, which lose their ability to regrow after injury in humans.
The researchers cultured damaged neurons with anthrobots and observed the interactions under a microscope. Remarkably, they witnessed the anthrobots migrating toward injured neuron branches and remnants. Upon contact, the anthrobots appeared to remove inhibitory debris and stimulate regrowth.
Neurons cultured alone showed no signs of regeneration. But the presence of anthrobots boosted neuron regrowth 2-3 fold over five days. This demonstrates the therapeutic potential of anthrobots to one day treat spinal cord injuries and neurodegenerative diseases inside the body.
Multiple Applications Envisioned in Regenerative Medicine
Looking forward, the scientists foresee broad applications for the anthrobots in tackling all sorts of injuries involving tissue damage. The tiny biobots could assist with clearing blood clots, removing scar tissue, delivering supportive drugs directly to wounds, and kickstarting regeneration.
Custom anthrobots could be designed using cell types from the intended tissues, like skin, heart, and bone cells. Their diminutive size allows them to navigate through blood vessels and intricate spaces unreachable by larger technological devices.
Programmed swarm behaviors could also enable anthrobots to distribute themselves throughout injuries and coordinate their healing activities for greater impact. Further into the future, perhaps a repertoire of specialized anthrobots, each with designated repair roles, could be deployed as teams to drive tissue regeneration.
Concerns Over Safety and Control
However promising, some scientists warn about the uncertainties of unleashing replicating living systems, even highly-specific human cell anthrobots, inside the body. Establishing control systems and containment will be critical before progressing to human trials. Hybrid approaches that pair anthrobots with microscale synthetic constructs or chemical payloads could provide more direction over their activities.
Governmental oversight will also be necessary over any new biotechnologies introduced into the clinic to uphold rigorous safety standards. But the Harvard researchers stress anthrobots offer a more targeted approach over things like engineered viruses with lower risks. Continued responsible innovation in this area paired with comprehensive trials can help realize the benefits while mitigating the risks.
The Next Targets: Broken Hearts and Damaged Brains
Having established a proof of healing concept with neurons, the Harvard team has already set their sights on two major applications – repairing heart tissue damaged after heart attacks and restoring brain tissue destroyed by neurodegenerative disease.
They are currently developing cardiac and neural anthrobots derived from the relevant human cell types that could one day patch failing hearts or reconnect damaged circuitry in the brain. If the neuronal regeneration with generic tracheal anthrobots is any indication, the future looks hopeful for these custom anthrobots to help heal hearts and brains.
The advent of anthrobots marks a new phase in the progress of miniature biobots. With continued development, the promise of deploying living human cell robots to remove injuries and kickstart tissue regeneration from within could very well become reality over the next decade. What once seemed like science fiction is steadily nearing clinical fruition through stepwise innovations from labs worldwide.
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