Fabrication of dBSA@Hemin@Ag nanozyme based biosensor and application for the assessment of longitudinal concentration changes of choline in human breast milk

Choline in human breast milk is crucial for infant neurodevelopment. However, choline concentration variation in human breast milk remains understudied. In this work, a colorimetric biosensor of bovine serum albumin@Hemin@Ag nanozyme was developed, leveraging its peroxidase-like activity to oxidize 2,2′-azino-bis(3ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt in the presence of hydrogen peroxide generated from choline oxidation by choline oxidase. Under the optimal conditions, a wide linear range (1–500 μM) and a low limit of detection (0.55 μM) were obtained for choline quantification. Longitudinal analysis of paired human breast milk samples revealed a significant decline in choline level from 15- to 90-d postpartum, influenced by maternal diet during pregnancy and pre-pregnancy body mass index. This research not only provides a robust tool for evaluating breast milk's quality, but also underscores the importance of diet during pregnancy and body mass index management for lactating mothers.