RGBradford: Accurate measurement of protein concentration using a smartphone camera and the blue to green intensity ratio

Abstract

The color shift caused by the interaction between proteins and Coomassie Brilliant Blue in the Bradford assay can be recorded with a smartphone camera. Color data can then be extracted from pictures and processed as analytical signals. Here, I present a simple procedure to accurately measure protein levels using color data from pictures of microplates. Plotting the ratio of blue to green intensity (RGB scale) as a function of protein concentration results in a linear (R² ≥ 0.99) relationship, from which protein levels in biological samples can be calculated with no significant difference from values obtained using absorbance data (RGB versus absorbance curves).

Keywords: Colorimetry; Coomassie Brilliant Blue; Digital image analysis; Mobile phone; Portable instrumentation; Spectrophotometry.