Upconversion nanoprobe counting analysis for specific detection of insulin-like growth factor-1 in Milk products

UNCA employs upconversion nanoparticles as signal probes for specific IGF-1 recognition. • Single-molecule counting enables IGF-1 detection with a low LOD of 6.04 pg/mL. • This method exhibits low cross reactivity and good recovery rates in milk products. There is rapidly growing interest in food nutrition assessment, particularly for nutrients present at low abundance. Here, an upconversion nanoprobe counting analysis (UNCA) is designed for ultra-sensitive detection of insulin-like growth factor-1 (IGF-1). The high sensitivity is attributed to the strong fluorescent intensity of upconversion nanoparticles (UCNPs) and highly specific antibody-antigen binding. Core–shell structured UCNPs are synthesized via co-precipitation followed by layer-by-layer epitaxial growth, and detection probes are constructed through hydrophilic ligand exchange and antibody conjugation. Two detection methods, traditional fluorescent intensity detection and single-molecule counting, are established with linear working ranges of 0.05–5000 ng/mL, which reach limit of detections (LODs) of 21.23 and 6.04 pg/mL, respectively. UNCA is further employed for analyzing three representative milk products, achieving recovery of 73.90%–107.09% with coefficients of variation (CVs) between 2.24% and 7.57%. This method demonstrates quantitative detection of trace-level IGF-1, especially via single-molecule counting. Download: Download high-res image (111KB) Download: Download full-size image