Electrochemical real-time detection of L-histidine via self-cleavage of DNAzymes.

Herein, a rapid electrochemical biosensor for L-histidine based on highly specific, L-histidine-dependent DNAzymes is described. DNA with a single, sessile ribo-adenine, self-cleaves in the presence of L-histidine, allowing a ferrocene tag to transfer electrons to the electrode. The double-stranded DNA complex was chemi-absorbed to a gold electrode via a 3' terminal thiol. The signal of this proposed sensor is linear over the range, 1 nM to 10 μM, with R=0.98775. To improve signal intensity, gold nanoparticles were anchored to a gold electrode surface which had been previously modified with self-assembled monolayers of 1,6-hexanedithiol. With gold nanoparticle modification, a lower detection limit of 0.1 pM L-histidine and a good linear relationship over the range, 0.1 pM to 50 nM were obtained. The proposed biosensor presents high specificity for L-histidine, is not affected by the presence of other amino acids, and demonstrates excellent enantio-selectivity toward L-histidine. This proposed sensor protocol offers reasonable selectivity, rapid speed, and operational convenience for real sample assays.