Design of Metal–Organic Framework-Based Nanoprobes for Multicolor Detection of DNA Targets with Improved Sensitivity

Metal–organic frameworks (MOFs) receive more and more interest in the field of analytical chemistry for their diverse structures and multifunctionality. In this study, we have designed and fabricated nanoscale MOF-based nanoprobes for multicolor detection of DNA targets with improved sensitivity. To do so, MOF-based nanoprobes, constructed by using porous MOFs as a scaffold to load signal dyes and a DNA hairpin structure as capping shell, have been prepared. Once the target has been introduced, a competitive displacement reaction triggers the release of fluorophores from the MOFs' pores. Consequently, a significantly enhanced fluorescence signal can be observed owing to the high loading capacity of MOFs. Therefore, the stimuli-responsive nanoprobes can enable sensitive detection of DNA targets with a low detection limit of 20 fM and selective identification to discriminate single-base mismatch. Moreover, the MOFs can encapsulate different fluorophores with different DNA gatekeepers designed according to the sequence of the target DNA, resulting in more kinds of stimuli-responsive nanoprobes for multiplexed DNA analysis in the same solution. Furthermore, these smart nanoprobes reported in this paper may provide a unique MOF-based tool for detection of various targets via stimuli-responsive systems in the future to widen the applications of MOFs.