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A sensitive electrochemical sensor is designed for DNA detection based on mimetic catalysis of metal-organic framework (MOF) and allosteric switch of hairpin DNA. The functional MOFs are synthesized as signal probes by a one-pot encapsulation of iron(III) meso-5,10,15,20-tetrakis(4-carboxyphenyl) porphyrin chloride (FeTCPP) into a prototypal MOF, HKUST-1(Cu), and sequentially conjugated with streptavidin (SA) as a recognition element. The resulting FeTCPP@MOF composites can mimetically catalyze the oxidation of o-phenylenediamine (o-PD) to 2,2'-diaminoazobenzene, which is a good electrochemical indicator for signal readout. The presence of target DNA introduces the allosteric switch of hairpin DNA to form SA aptamer, and thus, FeTCPP@MOF-SA probe is brought on the electrode surface via the specific recognition between SA and the corresponding aptamer, resulting in the enhancement of electrochemical signal. The "signal-on" electrochemical sensor can detect target DNA down to 0.48 fM with the linear range of 10 fM to 10 nM. Moreover, the MOF-based electrochemical sensor exhibits acceptable selectivity against even a single mismatched DNA and good feasibility in complex serum matrixes. This strategy opens up a new direction of porphyrin-functionalized MOF for signal transduction in electrochemical biosensing.

A facile strategy is presented to form 3D porous Cu@Cu O aerogel networks by self-assembling Cu@Cu O nanoparticles with the diameters of ca. 40 nm for constructing catalytic interfaces. Unexpectedly, the prepared Cu@Cu O aerogel networks display excellent electrocatalytic activity to glucose oxidation at a low onset potential of ca. 0.25 V. Moreover, the Cu@Cu O aerogels also can act as mimicking-enzymes including horseradish peroxidase and NADH peroxidase, and show obvious enzymatic catalytic activities to the oxidation of dopamine (DA), o-phenyldiamine (OPD), 3,3,5,5-tetramethylbenzidine (TMB), and dihydronicotinamide adenine dinucleotide (NADH) in the presence of H O . These 3D Cu@Cu O aerogel networks are a new class of porous catalytic materials as mimic peroxidases and electrocatalysts and offer a novel platform to construct catalytic interfaces for promising applications in electrochemical sensors and artificial enzymatic catalytic systems.

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A photosensitized and caspase-responsive multifunctional nanoprobe was designed by assembling a porphyrin, a folate targeting-motif and a dye-labelled peptide in a metal-organic framework (MOF) cage, which significantly increases the singlet oxygen quantum yield of porphyrin by 6.2 times, and achieves high efficient cancer therapy and in situ therapeutic monitoring with caspase-3 activation. The integration of theranostic functions in a single nanocarrier holds great promise in precision cancer diagnosis and treatment.

A catalytic hairpin assembly (CHA)-programmed porphyrin-DNA complex was designed to trigger the chemiluminescence as photoelectrochemical initiator for DNA sensing. First, the programmed double strand DNA (dsDNA) was formed using two hairpin DNAs as assembly components via target-assisted CHA reaction, and then immobilized on a capture DNA/CdS quantum dots modified electrode. The porphyrin (FeTMPyP) was conveniently assembled on a dsDNA scaffold via the groove interaction. The FeTMPyP@dsDNA complex possessed high catalytic activity toward luminol oxidation to generate the desirable chemiluminescence with high stability under various temperature and alkaline conditions. By integrating the signal amplification capacity of CHA and in situ FeTMPyP-mediated chemiluminescence as excitation light, an amplified photoelectrochemical sensing strategy is proposed for DNA detection. Under optimized conditions, the biosensor shows a wide linear range from 5 to 10000 fM with a detection limit of 2.2 fM. Moreover, the developed photoelectrochemical device exhibits excellent selectivity, high stability, and acceptable fabrication reproducibility. The CHA-programmed porphyrin-DNA strategy not only extends the applications of photoelectrochemistry, but also presents a novel methodology in bioanalysis.