Accessible Protein Quantification with a Low-Cost Spectrophotometer Using Bradford Reagent

Ensuring accessible and cost-effective laboratory equipment is essential for advancing scientific research in resource-limited settings. This study introduces a novel; low-cost spectrophotometer built with an Arduino microcontroller and a BH1750 light sensor to measure protein concentration using the Bradford method. The device features a 595 nm LED as the light source, encased in a 3D-printed PLA filament housing. Casein served as the standard protein for calibration and testing. The system demonstrated a linear detection range of 100 to 700 ppm, with a regression equation of y = 0.0007x + 0.1418 and a high correlation coefficient (R2 = 0.9921) compared to commercial spectrophotometers. The limit of detection and quantification were 58.43 and 194.77 ppm, respectively. Precision was confirmed with a HORRAT value of 0.161 using a 500 ppm sample, and accuracy was 103.34% for a 100 ppm sample. The device showed good selectivity against 200 ppm glucose interference. This open-source solution significantly reduces the cost of spectrophotometric analysis while improving accessibility in educational and remote laboratories. The practical implication of this study is it has strong potential for use in educational settings and field-based protein quantification due to its low cost, portability, and adequate performance.