Access to rapid point-of-care (POC) tests in resource-limited settings has been acknowledged by the World Health Organization (WHO) to decrease the cost and improve the efficiency of patient care. Among other applications POC tests are often desired to diagnose viral, bacterial, or fungal pathogens using their nucleic acids. Outside of the chemical laboratory, in rural clinical settings, detection of nucleic acids is especially difficult due to the lack of instrumentation. We developed a rapid, robust, and instrument-free colorimetric detection method for nucleic acids down to a concentration of 5 ug/mL using Nile Blue. Nile Blue is a cationic benzophenoxazine dye which has well-known binding interactions with nucleic acids and has been used in instrumental methods for DNA quantification. When combined with dsDNA, the color of Nile Blue shifts from blue to purple. Images of this color shift are collected using a smartphone and the images are subjected to image analysis. Changes in the red and green channel color intensities can be correlated to the ratios of dsDNA to Nile Blue, creating a semi-quantitative colorimetric sensor for dsDNA. By combining results from sensor regions with different concentrations of Nile Blue, we found it possible to quantitate dsDNA solutions with concentrations ranging from 10-100 ug/mL. This range is comparable to the range of nucleic acid concentrations that can be quantified using gold-standard UV-Vis spectroscopy. Unknown solutions of salmon sperm dsDNA ranging from 0-100 ug/mL were correctly identified within ± 10 ug/mL of true concentration through the use of k-means cluster analysis, and the concentrations of yeast DNA isolated from cultures of Saccharomyces cerevisiae were accurately predicted. As an instrument-free detection method, Nile Blue allows for rapid and robust quantification of dsDNA without the use of harsh reagents or specialized tools. Potential applications for this detection method include as a colorimetric probe for quantifying nucleic acid concentrations following amplification as well as for field-friendly paper analytical devices for detection of nucleic acids.

Rapid and robust semi-quantitative detection of DNA using Nile blue, a visible-region cationic dye

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.