Tapered hydrogel optical fiber probe for rapid and localized luminescence lifetime-based dissolved oxygen sensing.

Real-time monitoring of dissolved oxygen (DO) is critical in cellular physiology but remains challenging in complex environments. Here, we present a compact tapered hydrogel optical fiber probe for localized DO sensing based on luminescence lifetime. The probe features a polyethylene glycol diacrylate (PEGDA) tapered tip fabricated via self-focusing photopolymerization, encapsulating the oxygen-sensitive complex Ru(bpy)32+. By measuring the phase shift of modulated luminescence, the sensor provides stable quantification independent of dye concentration or light intensity fluctuations. We systematically optimized the probe composition, achieving an apparent t90 of ∼20 s during temporal measurements and stable operation for at least two weeks. Its practical utility was demonstrated by dynamically monitoring oxygen consumption in osteosarcoma spheroids, successfully differentiating between normal and drug-inhibited cellular respiration. This hydrogel-based, compact, and easily fabricated probe offers a practical tool for investigating oxygen metabolism in biomedical applications.