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.