Metal organic frameworks (MOFs) have made great progress in the field of fluorescent sensing; however, whether the electronic structure and recognized sites can be adjusted by external functionalization still remains challenging. Here, by postmodifying 5-carboxyfluorescein (Flu), externally coupled orbitals were introduced into the electronic structure of UiO-66-OH, and thus an effective photo-induced energy transfer (PET) process was established in functionalized MOFs (UiO-66-Flu), resulting in the reduction of the intrinsic blue fluorescence. Due to the formation of the ester bond by effective incorporation of the surface –OH with Flu, the hydrazinolysis reaction triggered by hydrazine could happen and the Zr6O6 clusters could further reduce the reaction energy barrier through strong hydrogen bonding with hydrazine, resulting in a remarkably low limit of detection (LOD, 27.17 nM) and a fast response (4 s). Furthermore, with polyvinylidene fluoride (PVDF) as the dispersion medium, UiO-66-Flu was fabricated into a UiO-66-Flu/PVDF film sensor, enabling the rapid detection of gaseous hydrazine within 2 s in simulated practical scenarios. We expect that the present fluorescent ligand modifying concept will not only deepen the understanding of electronic structure engineering in functionalized MOF design, but also shine light on the exploration of high-performance MOF-based sensing strategies.
Junmin Qian,Minghui Xu,Aili Suo,Weijun Xu,Ting Liu,Xuefeng Liu,Yu Yao,Hongjie Wang
To minimize the side effects and enhance the efficiency of chemotherapy, a novel folate-decorated hydrophilic cationic star-block terpolymer , [poly( l -glutamic acid γ-hydrazide)- b -poly(N,N-dimethylaminopropyl methacrylamide)] 3 - g -poly(ethylene glycol) ((PGAH- b -PDMAPMA) 3 - g -PEG), with disulfide linkages between the PEG and PDMAPMA blocks, was developed for targeted co-delivery of doxorubicin and Bcl-2 small interfering RNA (siRNA) into breast cancer cells. The terpolymer was synthesized by a combination of ring-opening polymerization, reversible addition–fragmentation chain transfer polymerization, PEGylation and hydrazinolysis. The chemical structures of the polymers were confirmed by 1 H-NMR analysis. The terpolymer could conjugate doxorubicin via an acid-labile hydrazone linkage and simultaneously efficiently complex siRNA through electrostatic interaction at N/P ratios of ⩾4:1 to form “two-in-one” nanomicelleplexes, which displayed a spherical shape and had an average size of 101.3 nm. The doxorubicin loading efficiency and content were 61.0 and 13.23%, respectively. The cytotoxicity, drug release profile, targeting ability, cellular uptake and intracellular distribution of the nanomicelleplexes were evaluated in vitro. We found that the release behaviors of doxorubicin and siRNA had a pH/reduction dual dependency. They were released faster under reductive acidic conditions (pH 5.0, glutathione : 10 mM) than under physiological conditions (pH 7.4). The folate-decorated nanomicelleplexes could deliver doxorubicin and Bcl-2 siRNA more efficiently into the same MCF-7 cell and exhibited a higher cytotoxicity than non-targeted nanomicelleplexes. These results indicate that the terpolymer could act as an efficient vehicle for targeted intracellular co-delivery of doxorubicin and therapeutic siRNA in cancer therapy.
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