Neurosurgery is a dauntingly tricky business. The brain is an immensely complex environment, with numerous functional structures densely packed together, making it incredibly hard to navigate. Then there’s the fact that, with the brain literally keeping us alive, even the slightest mistake could have devastating consequences.
No wonder, then, that operating on brain tumours is so difficult. Radiotherapy, too, is a tricky proposition due to the delicate nature of the brain. As for the third of the usual cancer treatment options, chemotherapy, the problem is getting the drugs to the brain: they struggle to cross the blood-brain barrier, meaning it’s hard to deliver a strong enough dose. This is especially problematic with deep-seated tumours – those that lie in hard-to-reach areas or near critical functional areas such as the brainstem, thalamus and behind the eye sockets, places where would be particularly inadvisable to risk damaging.
Soft microrobot from patient’s own blood
A team led by Professor Zhang Li from CUHK’s Department of Mechanical and Automation Engineering may have found a better option. The team has created tiny robots made from a patient’s own blood that can navigate even the most tortuous parts of the brain and hit tumours where it hurts, delivering chemotherapy drugs directly to their doorstep. Resembling strands of fibre, these robots can be just micrometres thick, allowing them to move through spaces as narrow as 2 mm.
Specifically, the team extracted fibrin, a protein produced during the blood clotting process, and combined it with a hydrogel, an extremely flexible material consisting of solid polymers suspended in water. The resulting robots are texturally similar to brain tissue, with the hydrogel matching its softness while offering greater elasticity. This enables them to move through even the most complex areas of the brain without causing damage, and also reduces the likelihood of immune rejection.
Precision navigation and targeted drug delivery by magnets
The robots also have magnetic nanoparticles embedded in them, meaning that they can be observed using X-rays imaging and controlled in real time via magnets.
“This strategy enables different modes of locomotion, including swinging, rolling and crawling, tailored to specific environments,” says Professor Zhang. “For example, rolling offers higher speed but requires larger spaces, crawling suits narrow or uneven surfaces, and swinging works in fluid-filled cavities. By dynamically adjusting the magnetic field’s direction and intensity, the robots can adapt their motion to complex intracranial terrain, ensuring precise and safe navigation.”
Surgeons can guide the robots precisely to the tumour, where an intense magnetic field causes them to rupture, depositing their load of chemotherapy drugs exactly where they’re needed.
Instead of blood vessels, the robots move through the cerebrospinal fluid (CSF). This offers several advantages, says Professor Zhang. Blood flows at 30 cm/s or higher but CSF flows at just 0.3–1.0 cm/s, which allows easier control. It also bypasses the blood-brain barrier and avoids rapid drug clearance, unlike in the bloodstream.
“Compared to traditional therapy, chemotherapeutic drugs applied this way are significantly more effective due to their localised and targeted delivery. It can achieve higher drug concentrations in the affected area while minimising systemic exposure and associated side effects,” says the professor.
A new frontier in cancer treatment
The robots were developed at the SIAT-CUHK Joint Laboratory of Robotics and Intelligent Systems, with contributions from Professor Ben Wang, an associate professor at Shenzhen University’s College of Chemistry and Environmental Engineering, who led the design; and Dr Xu Tiantian from the Shenzhen Institutes of Advanced Technology (SIAT), part of the Chinese Academy of Sciences, who engineered their locomotion.
In studies, the robots stopped tumours growing in pigs. Next, the team plans to test them in more complex animal models, paving the way for human trials within three to five years.
“The next step for this technology is to optimise the design and functionality for future clinical applications,” says Professor Zhang. “We’re refining the fibre structure beyond the current simple design to enable more complex shapes, enhancing locomotion and drug delivery systems for greater precision and efficiency, and exploring ways to integrate advanced imaging and control systems to improve real-time tracking and remote operation.”
While particularly useful against tumours in hard-to-reach or sensitive locations, the technology could potentially be used to treat most brain tumours – and even those in other inaccessible areas of the body. Soon, we could have a whole new cohort of handy little helpers in our ongoing battle against cancer.
