Functionalized\nNanodiamonds for Targeted Neuronal\nElectromagnetic Signal Detection

Intracellular sensing\ntechnologies necessitate a delicate balance\nof spatial resolution, sensitivity, biocompatibility, and stability.\nWhile existing methods partially fulfill these criteria, none offer\na comprehensive solution. Nanodiamonds (NDs) harboring nitrogen-vacancy\n(NV) centers have emerged as promising candidates due to their sensing\ncapabilities under biological conditions and their ability to meet\nall aforementioned requirements. This study focuses on expanding the\napplication of NDs and NV center-based sensing to neuronal contexts\nby investigating their functionalization and subsequent effects on\nthree distinct cell lines relevant to neurodegenerative disease research.\nOur study concentrates on positioning fluorescent NDs (FNDs) with\nNV center point defects onto neuronal cell surfaces. Achieving this\nthrough specific antibody attachment enhances the proximity of FND\n to neurites, facilitating the detection of local action potentials.\nTargeting voltage-dependent calcium channels (Cav2.2) with biotin–streptavidin-bound\nantibodies enables the precise positioning of FNDs. The functionalized\nFNDs (f-FNDs) show increased size and zeta potential, confirming the\nantibody presence without compromising cell viability. Two-color confocal\nimaging and co-localization algorithms are employed to further attest\nto the success of the functionalization. The f-FNDs are applied to\ncell cultures of three cell lines: SH-SY5Y, differentiated dopaminergic\nneurons, and hippocampal rat neurons; their biocompatibility and effects\non synaptic activity are explored. Moreover, preliminary total internal\nreflection fluorescence - optically detected magnetic resonance (TIRF-ODMR)\nexperiments across cellular sites demonstrate the magnetic field sensitivity\nof our sensor network. The successful establishment of this sensor\nnetwork provides a platform for characterizing neuronal signaling\nin healthy models and conditions mimicking Parkinson’s disease.