Smartphone-Assisted Protein to Creatinine Ratio Determination on a Single Paper-Based Analytical Device

Abstract

Proteinuria is a condition in which an excessive amount of protein is excreted in urine. It is, among others, an indicator of kidney disease or risk of cardiovascular disease. Rapid and reliable diagnosis and monitoring of proteinuria is of great importance for both patients and their physicians. For that reason, a paper-based sensor for proteinuria diagnosis was designed, optimized, and validated utilizing smartphone-assisted signal acquisition. In the first step, a few commonly employed protein assays were optimized and compared in terms of analytical performance on paper matrix. The tetrabromophenol blue method was selected as the one providing a sufficiently low limit of detection (39 mg·L−1) on the one hand and appropriate long-term stability (up to 3 months) on the other hand. The optimized assay was employed for protein-to-creatinine ratio (PCR) determination on a single paper-based sensor. For both analytes the linear ranges were within the clinically relevant range. The analytical usefulness of the developed sensors was demonstrated by a PCR recovery study in artificial urine. The obtained PCR recoveries were from ca. 80 to 150%.

Paper microzone assay embedded on a 3D printed support for colorimetric quantification of proteins in different biological and food samples

“…Few studies have evaluated the analytical performance of BPB assay in PADs but nevertheless, they are sufficient to make several comparisons. We achieved a LOD of 0.05 mg mL −1 ; it is comparable to the value of 0.039 mg mL −1 obtained by Lewinska and colleagues 10 and from 7-fold to 18-fold lower than the LOD detected in previous studies. 7,9 In terms of precision, our assay ranges from 3.2% to 8%, similarly to the values previously observed (2.6–6.4%).…”

“…To fill this gap, two recent independent studies developed a smartphone-assisted PAD for protein determination in human biological samples by comparing the analytical performance of the most common colorimetric assays available. 9,10 The results showed that the bromophenol blue (BPB) dye-binding method exhibited the best analytical performance and aligned with previous colorimetric PAD methods which have been developed. 5–8 In this assay, following the binding of BPB with proteins under acidic conditions (pH < 3), the colour of the substrate switches from yellow to green/blue, and the intensity of the colour developed is directly proportional to the protein concentration.…”

“…To perform these phases different tools have been successfully employed for (a) the fabrication of PADs (photolithography, 5,6 wax printing, 10 plotter cutting 7 and pen drawing 9 ), (b) image digitalization (digital camera, flatbed scanner and smartphone), and (c) quantitative image analysis in the detection zones (ImageJ, photoshop, digital color meter and corel photo-paint). Regarding the image analysis, the most common colour spaces used as analytical signals are the RGB (red, green, and blue) and the CMYK (cyan, magenta, yellow, and black).…”

“…Regarding the image analysis, the most common colour spaces used as analytical signals are the RGB (red, green, and blue) and the CMYK (cyan, magenta, yellow, and black). 6,7,9,10…”

“…As a result, a linear correlation was observed in the red channel, or in the cyan channel of the RGB and CYMB colour spaces, respectively. 7,9,10…”