Visual analysis of pyrophosphatase assisted by red and green two-color distance-reading test strips for the diagnosis of hyperthyroidism

Abstract

The aberrant expression of pyrophosphatase (PPase) plays an important role in hyperthyroidism; therefore, detecting PPase is highly significant for the diagnosis and treatment of hyperthyroidism. This study reports a dual-fluorescence, binary red and green two-color distance-reading method for detecting PPase using Probe-Cu²⁺ (520 nm) and cadmium telluride quantum dots (CdTe QDs; 694 nm) as signal reporters. The methods integrates the selective recognition properties of Probe-Cu²⁺ and the QDs for Cu²⁺ and pyrophosphate (PPi) complexes (PPi–Cu²⁺–PPi), using dip-dying and ink-jet printing technologies for making test strips. Under fluorescence mode, the detection ranges of Probe-Cu²⁺ and the QDs were 10–150 and 10–125 U L⁻¹ PPase, with limit of detection (LOD) values of 3 and 4 U L⁻¹, respectively. By contrast, the distance-reading mode enabled the analysis of 10–150 U L⁻¹ PPase with a LOD of 10 U L⁻¹ with the naked eye. Fluorescence and the color distance-reading mode were used to quantify PPase in 73 and 12 clinical serum samples, respectively. These results were consistent with clinical diagnosis and thyroid color Doppler scan images, using 500 U L⁻¹ as the cut-off value for hyperthyroidism diagnosis. These results showed that the PPase analysis strategy shows great potential for the clinical diagnosis of hyperthyroidism.