Colorimetry-based quantification of protein droplets using "ImageJ"

The objective of this study is to analyze protein concentration on a colorimetric basis by utilizing the openly accessible 'ImageJ' software. We herein report the successful measurement of protein concentration on a parafilm surface, following the application of Bradford reagent and subsequent photography with a smartphone, followed by analysis using the ImageJ software. Ovalbumin (OVA) and bovine serum albumin (BSA) were dissolved in phosphate buffered saline (PBS) and used as standards. The results demonstrated a linear correlation between integrated density and the actual weight of the standard, with R² values of 0.9908 for OVA samples in the range of 0-1.5 mg/ml and 0.9781 for BSA in the range of 0.25-1.5 mg/ml. The straightforward nature of the experiments and analyses makes the study we present here an invaluable resource for researchers and students who are constrained by equipment limitations, such as the lack of access to spectrophotometers.