a colorimetric paper-based sensor with nanoporous sba-16 for the sensing of amino acid cysteine in urine

We described a method for the determination of cysteine in urine sample by using a microfluidic paper-based sensor modifies with sba-16 [1]. cysteine is an essential amino acid in humans. cysteine metabolism problems like cystinuria, exist and are marked by increased cysteine levels in the blood or urine. sba-16 mesoporous silica molecular was successfully synthesized and characterized by fourier transform infrared spectroscopy, powder x-ray diffraction and used on the surface of paper based sensor [2]. the paper-based microfluidic sensor was made with a wax pen, a piece of filter paper and modified by mesoporous sba-16 and applicated it to determine the quantity of cysteine amino acid in urine sample. the sensor consist of six distribution channels: 6 circle zones with diameter of 6 mm on the ends of the channels and one circle zone with diameter of 8 mm in the center. the fabricated sensors for cysteine assay are operated based on an indicator displacement assay (ida) [3]. the sensor was optimized for determination of cysteine. the image of the colorimetric assay was captured with a camera and was opened by image j software in rgb color format so the image was inverted and the mean red values in detection zone were obtained by subtracting the blank value. the linear range of the calibration curve and the detection limit (s/n=3) were between 0.1 to 90 µm, 1.2 µm. the recoveries for the human urine samples analysis were in the range of 92%–111% for cysteine. so that the paper-based sensor method in this work could be used to determination the cysteine in urine.