Photometric detection of amino acid sarcosine using its hydrolysis by sarcosine oxidase and amplex red fluorophore

Prostate cancer is the most common malignant tumor in men, whose incidence is significantly different geographically and increases with age. For rapid diagnostics, new tumor markers with higher prognostic relevance are still being sought. A very promising candidate molecule is the amino acid sarcosine. The aim of this work was to design a highly sensitive photometric detection system for the sarcosine determination. An original methodology for determining the amino acid sarcosine using Trinder's reaction with sarcosine oxidase and Amplex Red fluorophore has been proposed. To improve the enzymatic reaction sarcosine oxidase and horseradish peroxidase were immobilised on superparamagnetic irone oxide nanoparticles (SPIONs). Absorbance dependence on sarcosine concentration read off at the wavelength of 572 nm was linear over a total range of 0 - 1000 μM (r ≥ 0.99) with limit of detection (LOD) of 2 μM and limit of quantification (LOQ) of 6 μM. The suggested procedure allows to analyze the content of sarcosine in real urine specimens. The proposed method is capable of detecting sarcosine at micromolar concentrations.