Long-term stable tetrahedral DNA functionalized upconversion nanoparticles for point-of-care detection of neutrophil gelatinase-associated lipocalin

Achieving point-of-care detection of neutrophil gelatinase-associated lipocalin (NGAL) contributes to the early diagnosis and treatment of acute kidney injury (AKI), but the lack of highly sensitive and long-term stable detection methods is a major challenge. In this work, tetrahedral DNA (tDNA)-functionalized large-sized upconversion nanoparticles (t-UCNP₃₀₀) were synthesized with high luminescence intensity. Leveraging the dual effects of surface charge density and the rigid structure of tDNA, the developed t-UCNP₃₀₀ exhibited long-term stability for over 60 days after being stored in phosphate buffer at 25 °C and pH 7.4, with no obvious aggregation and only slight luminescence attenuation. By using this developed t-UCNP₃₀₀, a luminescent lateral flow immunoassay (LFIA) strip was developed for point-of-care detection of NGAL, with a detection linearity range of 2.00–250 ng/mL and limit of detection (LOD) of 1.00 ± 0.07 ng/mL (S/N = 3). Taking advantage of the developed LFIA strip for NGAL with high selectivity and a rapid response time of <5 min, it was successfully applied for the determination of NGAL in artificial urine samples.