Fluorescent cysteine probe based on a signal amplification unit, a catalyzed hairpin assembly reaction and Forster resonance energy transfer

This work developed a sensitive DNA-based fluorescent probe comprising a cysteine binding unit and a signal amplification unit based on a catalyzed hairpin assembly (CHA) reaction. The cysteine binding unit comprises a homodimer of single-stranded DNA (ssDNA) rich in cytosine and held together by silver ions. In the presence of cysteine, the homodimer is disintegrated because of cysteine-silver binding that liberates the ssDNA, which drives the CHA reaction in the signal amplification unit. Forster resonance energy transfer (FRET) was used to report the generation of the amplified double-stranded DNA (dsDNA) product. Under the optimal conditions, the probe provided a good linearity (100-1200 nM), a good detection limit (47.8 +/- 2.7 nM) and quantification limit (159.3 +/- 5.3 nM), and a good sensitivity (1.900 +/- 0.045 mu M-1). The probe was then used to detect cysteine in nine real food supplement samples. All results provided good recoveries that are acceptable by the AOAC, indicating that it has potential for practical applications.

Automated summary

This study developed a DNA-based fluorescent probe for sensitive detection of cysteine using a catalyzed hairpin assembly reaction. The probe exhibited good linearity, detection limit, and sensitivity, and showed potential for practical applications in detecting cysteine in food supplement samples.