A Luminescence Resonance Energy Transfer (LRET)‐Based Nanoprobe for Ascorbic Acid Detection in Living Cells and Real Samples

Ascorbic acid (AA) is a ubiquitous and essential, water-soluble electron donor in living organisms which must be obtained from the diet. AA deficiency is closely associated with the pathogenesis and/or progression of various diseases, including diabetes and neurodegenerative disorders affecting hippocampal neurogenesis and cognitive function. Thus, it is beneficial to monitor AA in living cells and real samples. However, few probes have been developed for AA monitoring in both living cells and real samples. Here, we developed an LRET-based nanoprobe for AA detection, leveraging the near-infrared (NIR) excitation properties and spectral tunability of up-conversion nanoparticles (UCNPs). Upon exposure to AA, the MnO₂ layer undergoes gradual decomposition, leading to a significant decrease in absorption. The detection limit was determined to be 0.097 µg/mL. As the MnO₂ layer decomposes, the quenching effect on UCNPs is inhibited, leading to a 5.2-fold enhancement in up-conversion emission. The detection limit for this luminescence-based approach was determined to be 2.48 µg/mL. Moreover, UCNP@MnO₂ exhibits low cytotoxicity and efficiently enters cells, making it suitable for application in both living cells and real samples. This research demonstrates the dual-sensing capabilities of UCNP@MnO₂ to AA, and validates its application in both living cells and real samples.