An Oxygen-Sensitive Phosphorescent Probe for the Determination of l‑Ascorbic Acid in Serum

The level of l-ascorbic acid (AA) in serum reflects biological nutritional status and antioxidant defense capacity, while also indicating the severity of chronic wasting diseases such as malignancy or inflammation. Accurate detection of AA in serum samples is therefore critical for disease diagnosis and health monitoring. However, conventional methods suffer from several drawbacks, including severe matrix interference and complex pretreatment procedures. Herein, we present a stable phosphorescent probe, constructed from aluminum/pyromellitic acid phosphorescent materials (Al/PMA-PMs), for the sensitive detection of AA in complex biological matrices, obviating the need for any pretreatment. The Al/PMA-PMs exhibit strong blue room-temperature phosphorescence (RTP) in the dry state; upon dispersion in water, they show a prolonged lifetime (from 479.72 to 1073.55 ms) and a red-shifted emission (from 447 to 535 nm). The redshift is attributed to a reduced degree of polymerization, while the water stability stems from the strong Al³⁺-PMA coordination, which restricts molecular motion and suppresses nonradiative quenching. Importantly, the addition of AA effectively enhances the RTP intensity of Al/PMA-PMs by virtue of its high oxygen-scavenging ability, yielding a linear detection range of 0.1-10 μM and a detection limit of 66 nM. Owing to their strong anti-interference capability, the probe enables direct and accurate determination of AA in the serum of both healthy subjects and cancer patients, with excellent recoveries. Furthermore, serum samples validation against liquid chromatograph-mass spectrometer confirms the probe's accuracy and reliability, giving a correlation coefficient of 0.995 and demonstrating good agreement between the two methods. This work develops a water-stable phosphorescent probe that enables sensitive and practical AA detection in complex serum samples, providing a promising strategy for monitoring disease progression in cancer patients.