An unmodified gold nanorods-based DNA colorimetric biosensor with enzyme-free hybridization chain reaction amplification

•A novel and simple DNA optical biosensor based on unmodified gold nanorods and hybridization chain reaction was developed.•This new colorimetric biosensor exhibits wide linear range, high sensitivity and selectivity for DNA detection.•This method is label-free, modification-free, and enzyme-free, which hold great promise for routine sensing application.