Facile Colorimetric Detection of a Nucleic Acid Target via Catalytic Hairpin Assembly

The detection of disease-associated biomarkers is crucial for the early detection of illness and positive prognoses for patients. A colorimetric detection method that incorporates a DNA-based catalytic hairpin assembly (CHA) reaction with gold nanoparticles was designed and tested. While direct aggregation relies on a single inter-particle linkage between nanoparticles, a catalytic reaction releases target after linkages have formed allowing for formation of multiple nanoparticle bridges from one target strand. Gold nanoparticles were functionalized with thiolated DNA strands as a part of a unique two phase catalytic reaction scheme to accelerate the CHA reaction. Absorbance spectra was recorded for different times and target concentrations and compared to direct aggregation. The catalytic hairpin assembly reaction showed greater sensitivity to low target concentrations with respect to direct and demonstrated no leakage when prepared without target stands. Gel electrophoresis confirmed product formation of the catalytic hairpin aggregation scheme at low target concentrations. This detection scheme allows for portable, field-deployable, colorimetric readout with high levels of sensitivity and may be modified to detect a range of biomarkers