Development of a highly sensitive label-free DNA based fluorescent sensor for cisplatin detection

Cisplatin, or cis-diamminedichloroplatinum (II), is a platinum-based chemotherapeutic drug. It is widely used against many types of cancer. However, there are various side effects in patients taking cisplatin. The side effects are also found in chemotherapists or health workers exposed to contaminating cisplatin in workplace. Therefore, there is a need for sensors for cisplatin contamination detection. This work reports the development of a highly sensitive fluorescent sensor using single stranded ssDNA as a sensing element. It contains consecutive guanine bases to allow an efficient cisplatin binding. Then, an enzyme-free DNA amplification technique called catalyzed hairpin assembly (CHA) was employed to increase the sensor sensitivity. It comprises two hairpin DNAs (H1 and H2) which are in meta-stable states and can form a hybrid only in the presence of the cisplatin sensing ssDNA described above. H1 is designed such that after the hybrid formation, a newly exposed overhang forms a G-quadruplex (GQ). The GQ formation can be monitored by mixing a GQ binding dye called Thioflavin T (ThT) in the solution. ThT fluorescence quantum yield is negligible if ThT is free in solution but increases over 1000 folds when bound to GQ. The formation of H1 :H2 hybrid and ThT-GQ complex is disrupted if cisplatin binds to the sensing ssDNA. Therefore, the decrease in ThT fluorescence signifies the increase in cisplatin concentration and vice versa. The developed sensor capable to detect the cisplatin in the range of 500 7500 nM and the limit of detection is 182 nM. The merit of this novel sensor is that it is label-free therefore economical yet highly sensitive. It is expected that the sensor can help monitor cisplatin contamination in chemotherapeutic workplaces.