Synthesis and spectroscopic characterization of europium-tetracyclines complexes for potential applications in areas of biomedicine, industry and environment

Abstract

The objective of this work is the synthesis and the spectroscopic characterization of Europium-Tetracyclines complexes (EuTC) for potential applications in clinical analysis of hydrogen peroxide, urea peroxide, glucose, cholesterol and its fractions in aqueous solutions. Europium-Tetracycline complex (EuTc) presents interesting optical properties. It has absorption around 400 nm and emission around 615 nm and, therefore great Stokes shift. The europium emission proceeding from an antenna effect is strongly dependent of the characteristics of the solution, such as pH and presence or absence of hydrogen peroxide, urea peroxide, cholesterol, etc. The europium emission lifetime in the EuTc complex, is long, ~20 microsecond, and distinct of the biological medium. In the presence of hydrogen peroxide, the (EuTc) complex weakly fluorescent transforms into the (EuTc-HP) complex that it is highly fluorescent. With addition of small amounts of hydrogen peroxide in solution with neutral pH, occurs an increase of up to 15 times in the europium emission band around 615 nm. The emission lifetime in the EuTC-HP complex increases to ~60 microsseconds due to a reduction of luminescence "quenching"; by energy transfer. Similar effect occurs in the formation of EuTc complexes with urea peroxide and cholesterol. Such characteristics provide to the measures of emission and lifetime, high sensibility, high sensitivity and specificity in the detection of hydrogen peroxide, urea peroxide and cholesterol. The EuTc complex is of easy synthesis, operates in pH neutral, presents high stability and low cost. All these properties confer to the EuTc complex, the possibility of being a sensor of hydrogen peroxide, urea peroxide, glucose, cholesterol, among others, with potential applications in areas of the biomedicine, the industry and the environment. (AU)