Colorimetric Detection of a Bacterial Biomarker Using a Modified Litmus Test
Transcript
Start with an RNA-cleaving DNAzyme, a catalytic DNA that, on binding to a specific bacterial biomarker, gets activated.
The DNAzyme is linked to a streptavidin-coated magnetic bead via biotin at its 5' end. At the 3' end, it is bound to an oligonucleotide-linked urease, forming a functional magnetic bead.
To a tube containing functional magnetic beads, add an E. coli lysate.
A specific E. coli biomarker from the lysate, activates the DNAzyme, triggering cleavage of the RNA linkage, causing the detachment of the DNAzyme-urease conjugate.
Use a magnetic stand to immobilize the beads and remove the bead-bound DNAzyme-urease conjugate.
Transfer the released urease-containing supernatant to another tube.
Add a pH indicator dye — phenol red, and a urea solution.
The urease hydrolyzes urea into ammonia and carbon dioxide.
Ammonia, a weak base, raises the pH of the solution, causing a color change, that indicates the presence of the E. coli biomarker.
