posted on 2024-01-22, 14:37authored byChang Liu, Yanan Wu, Mengying Li, Fang Liu, Pengfei Kong, Haifeng Yang, Xinling Liu
Salivary d-alanine (d-Ala) and d-proline
(d-Pro) are of concern for their potential in the noninvasive
diagnosis of gastric cancer (GC). Most reports have succeeded in determining
the total concentration of d-Ala and d-Pro. However,
for personalized diagnosis and better elucidation of the underlying
specific correlation of d-Ala (or d-Pro) with GC,
it is desirable to determine the specific concentration of d-Ala or d-Pro. Herein, we propose an enantiomer-specific
tandem assay of d-Ala based on the colorimetric reaction
between 2,4-dinitrophenylhydrazine and pyruvic acid generated from
the deamination of d-Ala catalyzed by d-amino acid
oxidase, which is easily distinguished from l-form amino
acids, d-Pro, and many other species. A linear concentration
range is established from 20 to 400 μmol/L with a limit of detection
of 1.01 μmol/L. Real saliva sample tests reveal that the levels
of d-Ala in GC cases are remarkably higher than those in
healthy individuals, which offers a simple and low-cost strategy for
GC diagnosis. Simultaneously, the total concentrations of d-Ala and d-Pro in saliva are determined. Hence, the concentration
of d-Pro and the proportion of d-Ala could be calculated,
which further provides more molecule- and individual-specific information.
This research may offer a convenient method for noninvasive diagnosis
of GC and pave a new route to explore the potentials of rare d-form amino acids in disease diagnosis and treatment.