A novel label-free fluorescent detection of histidine based upon Cu2+-specific DNAzyme and hybridization chain reaction.

A novel label-free fluorescent sensor for histidine was developed based upon Cu2+-specific DNAzyme, hybridization chain reaction(HCR) and triplex DNA. Cu2+ can bind to the histidine, in the presence of histidine, leading to the inhibition of the cleavage of substrate strand of Cu2+-dependent DNAzyme, then the intact substrate strand trigger the HCR between H1 and H2. The HCR product can be recognized by triplex-forming oligonucleotide (TFO) through triplex formation and reported by the fluorescence of berberine, the fluorescence intensity of the sensing system was proportional to the concentration of histidine during the range of 5.7-455 nmol L-1, with a detection limit of 2.0 nmol L-1.