Researchers in China have developed magnetically controlled microrobots made from diatoms for the treatment of glioblastoma using photodynamic therapy. These microrobots exhibit excellent magnetic responsiveness and programmable motion capabilities, enabling them to precisely target and navigate to glioblastoma lesion areas. Once positioned at the tumor site, the diatom-based microrobots can be activated by laser irradiation, triggering a photodynamic therapeutic effect.

The research team, from the Shenyang Institute of Automation (SIA) of the Chinese Academy of Sciences, in collaboration with Shengjing Hospital of China Medical University, engineered the microrobots using naturally occurring diatoms—a type of unicellular organism.

Animal experiments have shown that the diatom-based microrobots produced a significant cytotoxic effect on primary glioblastoma cells and demonstrated good biocompatibility.

The findings were published in the journal Bio-Design and Manufacturing on February 16.

Diatoms typically range from several to tens of micrometers in size and are widely distributed in marine, freshwater, and wetland environments. They are among the smallest photosynthetic life forms on Earth. A diatom cell resembles a tiny box. Its porous outer cell wall, known as the frustule, is composed of colorless, transparent, rigid silica. Under a microscope, diatom frustules display a rich variety of structures featuring uniform micropores.

Inspired by these structural features, the researchers utilized the endogenous chlorophyll inherent in the diatoms as a natural photosensitizer, achieving photodynamic therapy (PDT) against glioblastoma without the need for additional drug modification or loading.

To construct the microrobots, the researchers used acid treatment techniques to process the diatoms into micro- and nanoscale robotic platforms. The intrinsic porous architecture of the frustule enables potential drug loading, while an external magnetic field is employed to control their movement, making them suitable for precise drug delivery. During fabrication, the natural chlorophyll contained within the diatom cells was deliberately preserved to function as a natural "drug."

Using artificial intelligence algorithms, the diatom robots achieved autonomous closed-loop motion control, enabling navigation along preset trajectories. The robots also demonstrated the ability to traverse narrow gaps and target cancer cells within cellular environments.

In animal experiments, the researchers injected the diatom microrobots directly into intracranial glioblastoma lesions in mice and activated photodynamic therapy using laser irradiation. The treatment reduced the survival rate of primary glioblastoma cells to 19.5%. Further results confirmed that the microrobots effectively inhibited tumor growth without causing significant systemic toxicity.

"This type of microrobot, which does not rely on exogenous drug loading, may help circumvent the risks of drug leakage associated with targeted delivery, thereby reducing the risk of damage to healthy tissues and cells," said Prof. JIAO Niandong, a researcher at SIA.

In the future, by combining this technology with intraoperative navigation systems and techniques for long-distance in vivo delivery, the researchers aim to enhance its targeting capability and therapeutic efficacy.

Schematic illustration of Mag-Diatom-mediated PDT (Image by SIA)