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Construction of a Liquid Crystal-Based Sensing Platform for Sensitive and Selective Detection of l-Phenylalanine Based on Alkaline Phosphatase

Zhou, Lele, Hu, Qiongzheng, Kang, Qi, Fang, Ming, Yu, Li
Langmuir 2018 v.35 no.2 pp. 461-467
alkaline phosphatase, calorimetry, essential amino acids, liquid crystals, neonates, phenylalanine, phenylketonuria, phosphates, sodium, titration, urine
The detection of l-phenylalanine (l-Phe) has become one of the most pressing issues concerning diagnosis and treatment of phenylketonuria in neonates; however, a simple and robust methodology is yet to be developed. Here, the application of novel liquid crystals (LCs)-sensing platform for sensitive, selective, and label-free detection of l-Phe was reported at the first time. We devised a strategy to fabricate the sodium monododecyl phosphate (SMP)-decorated LC sensing platform with the appearance of dark. Then, a dark to bright (D–B) optical images alteration of LCs was observed after transferring alkaline phosphatase (ALP) to the interface, owing to cleavage of SMP induced by ALP. LCs remained dark images after the SMP-decorated interface in contact with the pre-incubated ALP and l-Phe. Such optical appearance resulted from the inhibition of ALP by l-Phe, which was further verified by the isothermal titration calorimetry (ITC). The strategy was applied to sensing l-Phe, which have been proven to allow for sensitively and selectively differentiation of l-Phe from interfering compounds with similar aromatic groups, as well as seven other essential amino acids. More importantly, the detection limit of l-Phe reached 1 pg/mL in urine samples, further demonstrating its value in the practical applications. Results obtained in this study clearly demonstrated the superiority of LCs toward the l-Phe detection, which can pave a way for the development of high performance and robust probes for l-Phe detection in clinical applications.