Enhancement of the efficiency of a salivary alpha amylase biomarker for the sympathetic nervous system by a nano-optical sensor Tb–acetyl acetone complex

Abstract

A new nano-optical sensor Tb–acetylacetone (Tb–ACAC) complex is developed for assessing the activity of a salivary alpha amylase enzyme. The salivary alpha amylase enzyme is used as a biomarker for the assessment of the sympathetic nervous system activity in different saliva samples of unstressed, physically active (flight and fight), or psychologically active (examination) and smoking or non-smoking humans aged 20–55 years. The assessment of the alpha amylase activity is carried out through quenching of the luminescence intensity of the nano optical sensor Tb–ACAC complex at 545 nm by 2-chloro-4-nitrophenol (2-CNP) produced from the reaction of the enzyme with 2-chloro-4-nitrophenyl-α-D-maltotrioside (CNPG3) as a substrate. The remarkable quenching of the luminescence intensity at 545 nm of nano Tb–ACAC doped in a sol–gel matrix with various concentrations of 2-CNP was successfully used as an optical sensor for the assessment of α-amylase activity. A calibration plot was achieved over a concentration range of 3.0 × 10⁻⁴–8.0 × 10⁻⁹ mol L⁻¹ 2-CNP and over a linear range of enzyme activity of 0.5–300 U L⁻¹ with a correlation coefficient of 0.997 and a detection limit of 1.2 × 10⁻⁹ mol L⁻¹ and 0.05 U L⁻¹, respectively. The method was used satisfactorily for the assessment of α-amylase activity as a biomarker for the sympathetic nervous system in all studied cases of human saliva.