Detecting intracellular onion-like carbon nanostructures based on cell biolens’ properties by holographic flow cytometry

In recent years, onion-like carbons (OLCs), as a new type of carbon nanostructure, have emerged as significant in biomedical fields. OLCs are capable of being internalized by cells, interacting with various organelles, and thereby influencing cellular physiological processes. Consequently, there is considerable interest in the rapid, non-invasive detection and statistical analysis of intracellular OLCs. Holographic flow cytometry provides a high-throughput, label-free imaging approach, introducing a new approach for detecting intracellular OLCs. Indeed, cells can act as biological lenses, and the presence of intracellular OLCs alters their refractive index distribution, affecting their optical focusing and lensing features. In this study, we merged the 3D refractive index distribution of cells, obtained through in-flow tomographic experiments, with appropriate numerical simulations. This combination demonstrates that intracellular OLCs can be effectively detected by analyzing 2D quantitative phase maps, without the need for additional manual labeling. The experiments were conducted on colon cancer cells, both with and without intracellular OLCs. The results indicate that the biolens properties of cells can serve as a valuable biomarker for detecting intracellular OLCs. This promotes the research on OLCs-related physiological processes using holographic flow cytometry, enabling high-throughput, non-invasive screening of statistically significant number of cells.