Visual detection of bacterial DNA using activated paper stripe

A rapid and accurate detection of pathogens is essential for bedside or on-site diagnosis. Filter paper is an ideal diagnostic tool as it requires no equipment, possesses a high surface-area-to-volume ratio and a high capacity of capillary force. The functionalization of the surface of cellulose filter paper was explored by using glutaric anhydride, N-hydroxysuccinimide, and N,N'-dicyclohexylcarbodiimide. The activated surface systems enable aminated DNA to be immobilized on the surface of filter paper. Both synthetic oligonucleotides and bacterial genomic DNA of Staphylococcus aureus, Escherichia coli, and Campylobacter jejuni were detected successfully. The system produces a clear, consistent and highly visible brown signal within 1-5 min. The digital image can also be analyzed quantitatively due to the brown color resulting from the presence of magnetic beads. Bacterial DNA detection was accomplished by using 16S rDNA probe on the activated paper surface for universal bacterial diagnosis. The method is stable and repeatable. It can detect at least 0.5 pmol of a 120-base synthetic oligonucleotide per assay and 5-10 ng of bacterial DNA per assay. Graphical abstract Schematic representation of the method: a. functionalization of cellulose filter paper, b. printing of aminated probes, c. incubation, d. blocking of unreacted functional groups (as dots shown), e. a visual detection of targets, f. quantitative analysis of image.