A supercharged fluorescent protein as a versatile probe for homogeneous DNA detection and methylation analysis.

Supercharged proteins are a new class of functional proteins with exceptional stability and potent ability to deliver bio-macromolecules into cells. As a proof-of-principle, a novel application of supercharged proteins as a versatile biosensing platform for nucleic acid detection and epigenetics analysis is presented. Taking supercharged green fluorescent protein (ScGFP) as the signal reporter, a simple turn-on homogenous method for DNA detection has been developed based on the polyionic nanoscale complex of ScGFP/DNA and toehold strand displacement. This assay shows high sensitivity and potent ability to detect single-base mismatch. Furthermore, combined with bisulfite conversion, this ScGFP-based assay was further applied to analyze site-specific DNA methylation status of genomic DNA extracted from real human colon carcinoma tissue sample with ultrahigh sensitivity (4 amol methylated DNA).