Determination of sarcosine based on magnetic cross-linked enzyme aggregates for diagnosis of prostate cancer

As a biomarker of prostate cancer, sarcosine plays an important role in the diagnosis of cancer. The specificity of enzymatic reaction between sarcosine oxidase and sarcosine could be applied for the rapid and specific assay of sarcosine. Enzyme-based sarcosine quantification method has attracted our attention due to its high specificity and selectivity, but its wide use is restricted by the poor stability and challenging reusability. In this study, sarcosine oxidase was used to synthesize magnetic cross-linked enzyme aggregates (MCLEAs) with great stability and recyclability. The MCLEAs were characterized by transmission electron microscope, X-ray photoelectron spectroscopy, thermogravimetric analysis, X-ray diffractometer, and vibrating sample magnetometer, respectively. Subsequently, a colorimetric assay of sarcosine was developed based on the enzymatic reaction between MCLEAs and the substrate. The method can be used to quantify sarcosine with a linear range from 0.3125 to 10 mu g mL(-1) and recoveries ranging 87.50-97.75 %, suggesting its potential for reliable analysis of sarcosine in urine.