G-quadruplex-based ultrasensitive and selective detection of histidine and cysteine

► A label-free, G-quadruplex-based approach for histidine and cysteine detection was provided. ► The present fluorescent method is endowed with high sensitivity and selectivity. ► Detection limits 3 nM for histidine and 5 nM for cysteine were achieved by practical measurement. ► Histidine and cysteine can be detected in spite of the interference from urine.