Diagnosis of pathogen infection via a multiple-wavelength colorimetric sensor platform with loop-mediated isothermal amplification

Diagnosis of pathogen infection based on loop-mediated isothermal amplification (LAMP) is suitable for the point-of-care test due to fast process time, cost-effectiveness, and high specificity for target deoxyribonucleic acids (DNAs). In this diagnosis method, the presence of a target DNA in a tested solution can be determined by the color change during the LAMP reaction and the color change is typically monitored by naked-eye observation. However, although the evaluation by naked-eye is simple and fast, human subjectivity can significantly affect the diagnosis result because of an inconsistent positive threshold for diagnosis. In this study, we developed a colorimetric sensor platform that can accurately monitor the color change of LAMP solutions in 8-tube strips for diagnosing pathogen infection. To determine color change from a shift of light spectrum, this sensor contains eight pairs of red/green/blue (RGB) light-emitting diodes and RGB photodetectors to monitor a color change in a broad visible wavelength region. We also developed an evaluation algorithm based on a correlated-variation nulling technique to maximize the distance between negative and positive output distribution bands and calibrate the inherent tube-to-tube variation of color changes. The accuracy of the developed method was evaluated by testing 233 clinical samples for diagnosing Streptococcus agalactiae (also known as group B Streptococcus) bacterial infection and comparing the results with that by agarose gel electrophoresis. The accuracy was as high as 99.1%. This method can be one of standard diagnostic assays for gene amplification-based diagnosis of pathogen infection.