Facile One Pot Synthesis\nof Hybrid Core–Shell\nSilica-Based Sensors for Live Imaging of Dissolved Oxygen and Hypoxia\nMapping in 3D Cell Models

Fluorescence imaging allows for noninvasively visualizing\nand measuring\nkey physiological parameters like pH and dissolved oxygen. In our\nwork, we created two ratiometric fluorescent microsensors designed\nfor accurately tracking dissolved oxygen levels in 3D cell cultures.\nWe developed a simple and cost-effective method to produce hybrid\ncore–shell silica microparticles that are biocompatible and\nversatile. These sensors incorporate oxygen-sensitive probes (Ru(dpp)\nor PtOEP) and reference dyes (RBITC or A647 NHS-Ester). SEM analysis\nconfirmed the efficient loading and distribution of the sensing dye\non the outer shell. Fluorimetric and CLSM tests demonstrated the sensors’\nreversibility and high sensitivity to oxygen, even when integrated\ninto 3D scaffolds. Aging and bleaching experiments validated the stability\nof our hybrid core–shell silica microsensors for 3D monitoring.\nThe Ru(dpp)-RBITC microparticles showed the most promising performance,\nespecially in a pancreatic cancer model using alginate microgels.\nBy employing computational segmentation, we generated 3D oxygen maps\nduring live cell imaging, revealing oxygen gradients in the extracellular\nmatrix and indicating a significant decrease in oxygen level characteristics\nof solid tumors. Notably, after 12 h, the oxygen concentration dropped\nto a hypoxic level of PO<sub>2</sub> 2.7 ± 0.1%.