Diatom-derived magnetic biohybrid microrobots for photodynamic therapy in glioblastoma

Diatoms, as natural sources of porous silica, have important potential for biomedical applications. Biohybrid microrobots also show promise for targeted delivery; however, research on converting diatoms into biohybrid microrobots and exploiting their intrinsic properties for cancer treatment remains limited. In this study, Thalassiosira weissflogii was transformed into biohybrid microrobots (Mag-Diatoms) while retaining its natural chlorophyll, thereby enabling Mag-Diatom-mediated photodynamic therapy (PDT) without additional drug modification. In this system, Mag-Diatoms acted as microrobots, and their intrinsic chlorophyll served as a photosensitizer, exhibiting excellent biological safety. The autonomous closed-loop motion of the Mag-Diatoms was achieved using an artificial intelligence algorithm, which enabled controlled navigation along a preset trajectory. Mag-Diatoms also exhibited the ability to traverse narrow slits and target cancer cells within a cellular environment. The PDT effect was validated in vitro using human malignant glioblastoma (GBM) cell lines and primary cells derived from patients. The results revealed that the cell viability was closely related to the Mag-Diatom concentration, laser intensity, and irradiation time. Under combined Mag-Diatoms and laser treatment, viability decreased to 19.5% in primary cells and 3.6% in cell line models. Moreover, in vivo experiments using a mouse glioma model revealed that Mag-Diatom-mediated PDT effectively suppressed GBM progression. These findings highlight the potential of diatom-derived biohybrid microrobots, leveraging their natural properties, as a novel material and solution for PDT-based GBM therapy.