Improvement of the Sensitivity of the Direct Determination Method of Protein on Fabric by Covering with Transparent Sheet

Abstract

  A method for directly determining protein adherence to fiber substrate was investigated using a BCA reaction. Water to moisten the fabric, protein (bovine serum albumin) solution, and BCA solution were added to a test fabric swatch, which was then sandwiched between two polyethylene sheets to prevent air contact. After a predetermined time, the surface reflectance of the test swatch was measured from above the sheet to determine the degree of purple coloring due to the BCA reaction. It was found that a sufficient BCA reaction on the cotton swatch (2.5 cm × 2.5 cm) occured under conditions of 25℃, 8.0 μL/cm² of water, 4.8 μL/cm² of protein solution, and 16 μL/cm² of BCA solution. Furthermore, the calibration curve between the protein concentration in the range of 0.96–14 μg/cm² and the K/S value calculated from surface reflectance had the correlation coefficient R2＝0.9974, showing good linearity. Unlike the conventional method, sensitivity determination is possible because of the large inclination of the calibration curve.