"Turn off-on" fluorescent sensor for platinum drugs-DNA interactions based on quantum dots.

A "turn off-on" mode has been established by using the interaction between platinum anticancer drugs and DNA as input signal and the fluorescence reversible change of quantum dots (QDs) as output signal. The QDs fluorescence can be quenched by platinum anticancer drugs via photo-induced electron transfer process, rendering the system into "turn off" status, and the system can then be "turned on" when fluorescence is restored due to covalent conjugation between DNA and platinum anticancer drugs. This dual-directional fluorescence change realized the detection of cisplatin and DNA, overcoming the selectivity problem commonly existed in the traditional mono-directional fluorescence detection mode. The reversible fluorescent "turn off-on" mode has been further employed to study the interactions between DNA and different platinum anticancer drugs (cisplatin, oxaliplatin and carboplatin). Furthermore, the impacts of different types of DNAs (different in base sequence, chain length and ssDNA/dsDNA) on the mode are also explored. This simple, fast and convenient spectroscopic method owns promising applications in the study on interaction between medical molecules and DNA, and in biochemical detections.