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2020

Researchers at Zhejiang University have developed micro-nano robots with magnetic coatings.

Microrobots are robots with dimensions at the micron and nanometer scale capable of performing precise operations. They possess capabilities such as flexible movement, precise targeting, and drug delivery, and have broad application prospects in biomedical fields such as disease diagnosis and treatment, targeted delivery, and minimally invasive surgery. However, at present, most research on microrobots in the biomedical field focuses on in vitro levels, and their application at in vivo levels still presents significant challenges.

A research team led by researcher Zhou Min at the Second Affiliated Hospital of Zhejiang University School of Medicine/Institute of Translational Medicine developed a microrobot. Using a miniature spirulina as a living template and applying a magnetic coating, it is targeted to tumor tissue, successfully improving the hypoxic microenvironment of the tumor and effectively achieving tumor diagnosis and treatment under magnetic resonance/fluorescence/photoacoustic trimodal medical imaging navigation. This research was published in the renowned materials journal Advanced Functional Materials and selected as a cover feature for that issue.

The tumor microenvironment, especially the hypoxic microenvironment within the tumor tissue, is one of the major reasons for the development of resistance to numerous cancer treatments. In particular, in commonly used radiotherapy in clinical practice, oxygen participates in assisting ionizing radiation-induced damage to the DNA double helix structure, promoting cell apoptosis. Hypoxia affects radiotherapy efficacy, leading to tumor cell resistance. Therefore, effectively reducing or reversing tumor hypoxia is a key research area for enhancing the effectiveness of radiotherapy.

This system is a photosynthetic biohybrid system that maintains the high oxygen production activity of microalgae while also possessing the directional magnetic driving capability of magnetite nanoparticles.

Magnetically engineered PBNs can be targeted and accumulated in tumors under external magnetic field control. Through photosynthesis, they produce oxygen in situ to reduce the degree of hypoxia within the tumor, thereby improving the efficiency of radiotherapy (RT). Simultaneously, the chlorophyll released by PBNs after irradiation can act as a photosensitizer, generating cytotoxic reactive oxygen species (ROS) under laser irradiation, achieving synergistic photodynamic therapy (PDT). In addition to the excellent T2-mode magnetic resonance imaging (MRI) function provided by the Fe3O4 coating, PBNs also possess natural fluorescence (FLI) and photoacoustic imaging (PAI) functions based on chlorophyll, allowing for non-invasive monitoring of tumor treatment and changes in the tumor microenvironment.

In a mouse model of in situ breast cancer, the enhanced combined therapy showed a significant inhibitory effect on tumor growth. During treatment, microrobots were targeted and accumulated in the tumor using an external magnetic field, and external light irradiation was used to produce oxygen in situ through photosynthesis to reduce the degree of hypoxia within the tumor, thereby improving the efficiency of radiotherapy. In a mouse model of in situ breast cancer, the enhanced combined therapy showed a significant inhibitory effect on tumor growth.

The photosynthetic biohybrid microrobot system not only has a positive effect on radiotherapy, but the chlorophyll released after irradiation can also act as a photosensitizer, generating cytotoxic reactive oxygen species to kill tumor cells, achieving synergistic photodynamic therapy. "Normal photodynamic therapy requires oxygen and reactive oxygen species to proceed smoothly, and the current microrobots can effectively address these two needs." In addition, the large amount of chlorophyll in microalgae also has natural fluorescence and photoacoustic imaging functions, allowing for non-invasive monitoring of tumor treatment and changes in the tumor microenvironment.

More importantly, this microrobot, being a natural biological entity, can be effectively degraded in vivo, providing translational prospects for the application of biohybrid materials in targeted delivery and in vivo biomedicine. This microrobot, being a natural biological entity, can be effectively degraded in vivo, providing translational prospects for the application of biohybrid materials in targeted delivery and in vivo biomedicine.

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