Platinum Wire-Embedded Culturing Device for Interior Signal Recording from Lollipop-Shaped Neural Spheroids

Three-dimensional (3D) neural cultures are increasingly recognized for their complexity and resemblance to in vivo neural microenvironments. In this paper, we present a novel 3D cell culturing and noninvasive characterization technique of neural spheroids. Based on embedded platinum wires, the cultured cells are lollipop-shaped spheroids where axons are extended and integrated around the embedded wires. Electrical microstimulation enhanced the connectivity between spheroids and demonstrated signal propagation among them. The resultant axonal elongation facilitated the formation of robust neural tracts interconnecting the neural spheroids. Variation of cells' density allows to adjust the spheroid's diameter, identifying 1 million cells as good number of cells for robust spheroid formation. Recordings of spheroid activities reveal higher-quality neural signal measurement from interior cells compared to those obtained from exterior cells. Viability assays confirmed the efficacy of the proposed culturing technique for sustained growth of neural spheroids over a 1-month period. The proposed spheroid culturing technique holds potential applications in various fields, such as development of brain organoids, which enables real-time interconnection characterization and sensing of environment conditions.