DNA coated CoZn-ZIF metal-organic frameworks for fluorescent sensing guanosine triphosphate and discrimination of nucleoside triphosphates.

Imidazole-based metal-organic frameworks (MOFs) are easy to prepare as well-dispersed nanoparticles, which have attracted a lot of interest in sensing. Metal substitution is an effective way to regulate the composition and performance of MOFs. Herein, by tuning the contents of Co and Zn, a series of homobimetallic CoZn-ZIF (x = 0-100) were synthesized. Using a fluorescently-labeled DNA oligonucleotide probe, guanosine triphosphate (GTP) can readily displace the adsorbed DNA from CoZn-ZIF, resulting in over 30-fold fluorescence enhancement with 1 mM GTP. CoZn-ZIF could specifically recognize adenosine triphosphate (ATP), whereas CoZn-ZIF and CoZn-ZIF responded to both ATP and GTP. For comparison, CoNi-ZIF and CoCu-ZIF were also prepared, but none of them were selective for any of the molecules, indicating a synergetic effect of cobalt and zinc in CoZn-ZIF for the selective recognition of GTP. This system can sensitively detect GTP with a detection limit of 0.13 μM. Moreover, based on the varying binding affinities of these CoZn-ZIFs towards different nucleoside triphosphates (NTPs), a ZIF fluorescent sensor array was also designed for the discrimination of the four types of NTPs.