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We designed and synthesized three new berberine-based compounds, namely, pyridine-2,6-dimethyl-/2,2'-bipyridine-3,3'-dimethyl-tethered berberine dimers BD1 and BD2, and a tetrakis(4-benzyl)ethylene linked berberine tetramer BD4. We identified that the dimer BD2 and tetramer BD4, as well as 1,10-phenanthroline-2,9-dimethyl-linked berberine dimer BD3 previously reported by us, showed remarkable aggregation-induced emission (AIE) properties which endowed them with higher singlet oxygen (

To improve the efficiency of radiation therapy (RT) for breast cancer, a designable multifunctional core-shell nanocomposite of FeP@Pt is constructed using Fe(III)-polydopamine (denoted as FeP) as the core and platinum particles (Pt) as the shell. The hybrid structure is further covered with hyaluronic acid (HA) to give the final nanoplatform of FeP@Pt@HA (denoted as

The low X-ray attenuation coefficient of tumor soft tissue and the hypoxic tumor microenvironment (TME) during radiation therapy (RT) of breast cancer results in RT resistance and thus reduced therapeutic...

High sensitivity and specificity imaging of miRNA in living cells plays an important role in understanding miRNA-related regulation and pathological research. Localized DNA circuits have shown good performance in reaction rate and sensitivity and have been proposed for sensitive imaging of miRNA in living cells. However, most reported localized DNA circuits have a high risk of derailment or a limited loading rate capacity, which hinder their further application. To solve these issues, we herein developed a domino-like localized cascade toehold assembly (LCTA) amplification-based DNA nanowire to achieve highly sensitive and highly specific imaging of miRNAs in living cells by using DNA nanowires as reactant delivery vehicles and confining both reactant probes in a compact space. The LCTA is constructed by interval hybridization of DNA double-stranded probe pairs to a DNA nanowire with multiplex footholds generated by alternating chain hybridization. Due to the localized effect, the LCTA showed high reaction kinetics and sensitivity, and the method could detect miRNAs as low as 51 pM. The LCTA was proven to be able to accurately distinguish the miRNA expression difference between normal cells and cancer cells. In particular, the developed LCTA could be used to construct an OR logic gate to simultaneously image the total amount of multiple miRNAs in living cells. We believe that the developed LCTA can be an effective intracellular nucleic acid imaging tool and can promote the development of nucleic acid-related clinical disease diagnosis and DNA logical sensors.

Traditional RCA methods face some drawbacks including limited specificity and amplification templates with sequence dependence. Herein, a universal RCA (URCA) strategy for label-free nucleic acid sensing with high specificity was proposed, which could be used for sensing of different nucleic acids without redesigning or synthesizing new amplification templates. The URCA strategy also showed high accuracy for miRNA analysis in practical samples.

Sensitive and specific imaging of microRNA (miRNA) in living cells is of great value for disease diagnosis and monitoring. Hybridization chain reaction (HCR) and DNAzyme-based methods have been considered as powerful tools for miRNA detection, with low efficient intracellular delivery and limited amplification efficiency. Herein, we propose a Hairpins@MnO

Zwitterionic metal-organic frameworks (MOFs) of {[Cu(Cbdcp)(Dps)(H2O)3]·6H2O}n (MOF 1) and [Cu4(Dcbb)4(Dps)2(H2O)2]n (MOF 2) (H3CbdcpBr = N-(4-carboxybenzyl)-(3,5-dicarboxyl)pyridinium bromide; H2DcbbBr = 1-(3,5-dicarboxybenzyl)-4,4'-bipyridinium bromide; Dps = 4,4'-dipyridyl sulfide) quench the fluorescence of cytosine-rich DNA tagged with 5-carboxytetramethylrhodamine (TAMRA, emission at 582 nm, denoted as C-rich P-DNA-1) and yield the corresponding P-DNA-1@MOF hybrids. Exposure of these hybrids to Ag+ results in the release of the P-DNA-1 strands from the MOF surfaces as double-stranded, hairpin-like C-AgI-C (ds-DNA-1@Ag+) with the restoration of TAMRA fluorescence. The ds-DNA-1@Ag+ formed on the surface of 1 can subsequently sense biothiols cysteine (Cys), glutathione (GSH), and homocysteine (Hcy) due to the stronger affinity of mercapto groups for Ag+ that serves to unfold the ds-DNA-1@Ag+ duplex, reforming P-DNA-1, which is re-adsorbed by MOF 1 accompanied by quenching of TAMRA emission. Meanwhile, MOF 2 is also capable of co-loading a thymine-rich probe DNA tagged with 5-carboxyfluorescein (FAM, emission at 518 nm, denoted as T-rich P-DNA-2) to achieve synchronous sensing of Ag+ and Hg2+, resulting from the simultaneous yet specific ds-DNA-1@Ag+ and T-HgII-T duplex (ds-DNA-2@Hg2+) formation, as well as the distinctive emission wavelengths of TAMRA and FAM. Detection limits are as low as 5.3 nM (Ag+), 14.2 nM (Cys), 13.5 nM (GSH), and 9.1 nM (Hcy) for MOF 1, and 7.5 nM (Ag+) and 2.6 nM (Hg2+) for MOF 2, respectively. The sequential sensing of Ag+ and biothiols by MOF 1, and the synchronous sensing of Ag+ and Hg2+ by MOF 2 are rapid and specific, even in the presence of other mono- and divalent metal cations or other biothiols at much higher concentrations. Molecular simulation studies provide insights regarding the molecular interactions that underpin these sensing processes.

The highly sensitive detection of low-abundant apurinic/apyrimidinic endonuclease 1 (APE1) activity is of great significance for early diagnosis of disease and pathological research. Many methods for detecting APE1 based on isothermal nucleic acids amplification have been developed for improving its sensitivity. However, some of these methods have certain limitations, such as multiple reaction steps, narrow linear range, and complicated processes for fluorescent labeling. Herein, we develop a highly sensitive and label-free APE1 fluorescence detection method based on rolling circle amplification combined with G-quadruplex (RCA-G4). A hairpin probe (HP) labeled with the AP site can be recognized and cleaved by APE1, leading to the release of the primer sequence, which triggered RCA to produce long chain amplification products with a great amount of repeated sequences. The formed amplicon contains a series G-quadruplex structure, which can be combined with Thioflavin T (ThT) to produce fluorescence and achieve high sensitivity label-free detection of APE1. Benefit from the high amplification efficiency of RCA and the high fluorescence quantum yield of G-quadruplex/ThT, a detection limit as low as 1.52 × 10

Three-dimensional (3D) and two-dimensional (2D) Ag-based zwitterionic metal–organic frameworks (MOFs) [Ag2(Cedcp)]n (1, 3D, H3CedcpBr denotes N-(carboxyethyl)-(3,5-dicarboxyl)-pyridinium bromide) a...

PIWI-interacting RNAs (piRNAs) are a complex class of small non-coding RNAs which specifically interact with the PIWI protein to play important roles in germline development and somatic tissues. Aberrant expressions of piRNAs have been recently found in a variety of malignant tumors and associated with cancer hallmarks. However, current methods of analyzing piRNAs are limited to reverse transcription quantitative polymerase chain reaction and next generation sequencing. In this study, we have developed a universal catalytic hybridization assembly system (uniCHA) to quantify piRNAs as well as microRNAs. The system simply comprises two universal hairpin DNA strands and one starting hairpin DNA which can be tailored by a simple rule to bind different piRNA and miRNA targets. The uniCHA system was proved to be able to analyze various piRNAs and miRNAs at the same reaction condition with low leakage and high sensitivity of pM level. With this system, we have detected piR-651 and miR-1246 in 10

Designing and developing nanomedicine based on the tumor microenvironment (TME) for effective cancer treatment is highly desirable. In this work, polyvinyl pyrrolidone (PVP) dispersed nanoscale metal-organic framework (NMOF) of Fe-TCPP (TCPP = tetrakis (4-carboxyphenyl) porphyrin) loaded with hypoxia-activable prodrug tirapazamine (TPZ) and coated by the cancer cell membrane (CM) is constructed (the formed nanocomposite denoted as PFTT@CM). Due to the functionalization with the homologous cancer cell membrane, PFTT@CM is camouflaged to evade the immune clearance and preferentially accumulates at the tumor site. Once internalized by cancer cells, PFTT@CM is activated by the TME through redox reaction and Fenton reaction between Fe

Sensitive, specific and rapid methods for detecting microRNAs (miRNAs) play critical roles in disease diagnosis and therapy. Enzyme-free amplification techniques based on DNAzyme assembly have recently been developed for the highly specific miRNA analysis. However, traditional DNAzyme-based assembly (free DNAzyme) amplifiers is mainly dependent on the target-induced split DNAzyme fragments to assemble into activated DNAzyme structures, which have made a compromise between the sensitivity and specificity due to the random diffusion of dissociative probes in a bulk solution with poor kinetics. Herein, based on a rationally designed DNA probe, we developed an intramolecular DNAzyme assembly (intra-DNAzyme) method to overcome these challenges. The miR-373 is used as model analyte for our current proof-of-concept experiments. Compared with the free-DNAzyme method, our method showed significantly improved analytical performance in terms of dynamic range, assay sensitivity and speed. This method can detect miR-373 specifically with a detection limit as low as 4.3 fM, which is about 83.7 times lower than the previous free-DNAzyme method. This intra-DNAzyme strategy would be of great value in both basic research and clinical diagnosis.

Development of versatile sensing methods for sensitive and specific detection of clinically relevant nucleic acids and proteins is of great value for disease monitoring and diagnosis. In this work, we propose a novel isothermal Self-primer EXPonential Amplification Reaction (SPEXPAR) strategy based on a rationally engineered structure-switchable Metastable Hairpin template (MH-template). The MH-template initially keeps inactive with its self-primer overhanging a part of target recognition region to inhibit polymerization. The present targets can specifically compel the MH-template to transform into an "activate" conformation that primes a target-recyclable EXPAR. The method is simple and sensitive, can accurately and facilely detect long-chain single-stranded nucleic acids or proteins without the need of exogenous primer probes, and has a high amplification efficiency theoretically more than 2n. For a proof-of-concept demonstration, the SPEXPAR method was used to sensitively detect the characteristic sequence of the typical swine fever virus (CSFV) RNA and thrombin, as nucleic acid and protein models, with limits of detection down to 43 aM and 39 fM, respectively, and even the CSFV RNA in attenuated vaccine samples and thrombin in diluted serum samples. The SPEXPAR method may serve as a powerful technique for the biological research of single-stranded nucleic acids and proteins.

α,β-Unsaturated phosphine sulfides may exhibit different reactivity from α,β-unsaturated phosphine oxides toward nucleophilic addition and thus may find new applications in copper(I)-catalyzed asymmetric reactions. Herein, various α,β-unsaturated phosphine sulfides were prepared in moderate to excellent yields from the parent α,β-unsaturated phosphine oxides with Lawesson’s reagent. The reaction enjoys a broad substrate scope and tolerates a variety of functional groups.

We herein report an efficient Ag+ and S2− dual sensing scenario by a three-dimensional (3D) Cu-based metal–organic framework [Cu(Cdcbp)(bpea)]n (MOF 1, H3CdcbpBr = 3-carboxyl-(3,5-dicarboxybenzyl)-pyridinium bromide, bpea = 1,2-di(4-pyridinyl)ethane) shielded with a 5-carboxytetramethylrhodamine (TAMRA)-labeled C-rich single-stranded DNA (ss-probe DNA, P-DNA) as a fluorescent probe. The formed MOF-DNA probe, denoted as P-DNA@1, is able to sequentially detect Ag+ and S2− in one pot, with detection limits of 3.8 nM (for Ag+) and 5.5 nM (for S2−), which are much more lower than the allowable Ag+ (0.5 μM) and S2− (0.6 μM) concentration in drinking water as regulated by World Health Organization (WHO). The detection method has been successfully applied to sense Ag+ and S2− in domestic, lake, and mineral water with satisfactory recoveries ranging from 98.2 to 107.3%. The detection mechanism was further confirmed by molecular simulation studies.

A metal–organic framework of Cu(II) supported by a zwitterionic pyridinium dicarboxylate and 4,4′-bipyridine mixed ligands was prepared and impregnated with three dye-labeled DNA sequences with fixed wavelength differences. This hybrid material formed is capable of the synchronous detection of three conserved Zika virus RNA sequences with high sensitivity and selectivity, and low detection limits of 0.56 ± 0.02, 0.16 ± 0.04, and 0.19 ± 0.05 nM, without any cross-reactions, as confirmed by both experimental and molecular simulation studies.

Calcium supplementation is effective in alleviating the process of osteoporosis and the occurrence of osteoporotic fractures for people with long-term calcium deficiency. Herein, five water-stable calcium carboxylate compounds, that is, mononuclear coordination compound [Ca(Cbdcp)(H2O)6]·0.5H2O (1, H3CbdcpBr = N-(4-carboxybenzyl)-(3,5-dicarboxyl)pyridinium bromide), and metal organic frameworks (MOFs) {[Ca3(Dcbdcp)2(H2O)12]·2H2O}n (2, H4DcbdcpBr = N-(3,5-dicarboxybenzyl)-(3,5-dicarboxyl)pyridinium bromide), {[Ca(Cmdcp)(H2O)4]·3H2O}n (3, H3CmdcpBr = N-carboxymethyl-(3,5-dicarboxyl)pyridinium bromide), {[Ca(Cdcbp)]·2H2O}n (4, H3CdcbpBr = 3-carboxyl-(3,5-dicarboxybenzyl)-pyridinium bromide) and {[Ca0.5(Cmcp)]·2H2O}n (5, H2CmcpBr = N-carboxymethyl-(3-carboxyl)pyridinium bromide), were synthesized from the reaction of CaCl2 with five different kinds of zwitterionic carboxylate ligands in the presence of NaOH, respectively. Compounds 1–5 were characterized by Fourier-transform infrared (FTIR) spectroscopy, elemental analyses, single-crystal X-ray crystallography, and inductively coupled plasma mass spectrometry (ICP-MS). Compound 1 features a mononuclear structure and MOF 2 with a one-dimensional (1D) structure while MOFs 3 and 5 with 2D layer structures and MOF 4 showing a 3D structure. Compounds 1–5 exhibited good water stability and possessed considerable biocompatibility with primary mice osteoblasts. The in vitro ability of compounds 1–5 in regulating osteoblastic differentiation was studied via alkaline phosphatase (ALP) staining, alizarin red S (ARS) staining, and quantitative real-time polymerase chain reaction (qPCR). Among these 5 compounds, MOF 4 showed the overall best in vitro osteogenic effects. Then, we administrated MOF 4 intragastrically to bilaterally ovariectomized mice for 8 weeks and found that bone loss caused by ovariectomy (OVX) was significantly alleviated. Besides, MOF 4 administration showed no toxic effects in the main organs of the mice. Altogether, zwitterionic carboxylate ligands-based calcium compounds provide a new strategy for calcium agents development.

Liquid biopsy is becoming an innovative tool in precision oncology owing to its noninvasive identification of biomarkers circulating in the body fluid at various time points for continuous and real-time analysis of disease progression. MicroRNAs in blood exosomes are identified as a new promising class of potential biomarkers for cancer diagnostics and prognostics. Conventional detection of blood exosomal microRNAs need multiple-step, complicated, costly, and time-consuming sample preparation of exosomes isolation and RNA extract, which affect the accuracy and reproducibility of analytical results. In this work, we set up an in situ quantitative analysis of human plasma exosomal miR-1246 by a probe of 2'-O-methyl and phosphorothioate modified molecular beacon. The probe has outstanding nuclease resistance in highly active RNase A/T1/I, which makes it stable for direct application in blood samples. With rapid rupture of exosomes membrane by Triton X-100, the probe can enter exosomes to specifically target miR-1246 exhibiting quantitative fluorescent signals. Using the output signals as a diagnostic marker, we differentiated 33 breast cancer patients from 37 healthy controls with 97.30% sensitivity and 93.94% specificity at the best cutoff. The blood biopsy is simple without extracting plasma exosomes and their nucleic acids content, time-saving in about 2 h of total analysis process, and microvolumes needed for plasma sample, suggesting its good potential to clinical application.

In situ analysis of tumor-related messenger RNAs (mRNAs) is significant in identifying cancer cells at the genetic level in the early stage. Rolling circle amplification (RCA)-based methods are primary tools for in situ mRNA assay, however, the necessary ligation reaction not only shows low ligation efficiency, but also greatly prolongs the assay time that increases the risk of cells losing and mRNAs leakage. In this work, we propose a novel toehold-mediated ligation-free RCA (TMLFRCA) on a designed structure-switchable dumbbell-shaped probe (SDP). Target mRNA can specifically activate SDP from its circular form by toehold strand displacement, thereby initiates in situ RCA for mRNA imaging with the help of a short DNA primer. For the proof-of-concept demonstration, the TK1 mRNA was sensitively detected by TMLFRCA in less than 3.5 h with a limit of detection (LOD) of 0.39 fM (corresponds to 2.39 × 10 8 c o p i e s L − 1 ), and significantly improved specificity capable for distinguishing single base difference. The sensitivity of the TMLFRCA for TK1 mRNA in situ assay is ∼29-fold and ∼7-fold higher than that of FISH and ligase-assisted RCA method, respectively, which enables the TMLFRCA method capability of highly sensitive and specific distinction mRNA expression levels between cancer cells and normal cells. We believe this TMLFRCA strategy would be of great value in both basic research and clinical diagnosis.

Herein, a luminescent water-stable terbium-based metal-organic framework (MOF) {[Tb(Cmdcp)(H

Zwitterionic metal-organic frameworks (MOFs) of {[Cu(Cbdcp)(Dps)(H

Breast cancer is the second cause of cancer mortality in women globally. Early detection, treatment, and metastasis monitoring are of great importance to favorable prognosis. Although conventional diagnostic methods, such as breast X-ray mammography and image positioning biopsy, are accurate, they could cause radioactive or invasive damage to patients. Liquid biopsy as a noninvasive method is convenient for repeated sampling in clinical cancer prognostic, metastatic evaluation, and relapse monitoring. MicroRNAs encased in exosomes circulating in biofluids are promising candidate cancer biomarkers because of their cancer-specific expression profiles. Here, we report an in situ detection of microRNA-1246 (miR-1246) in human plasma exosomes as breast cancer biomarker by a nucleic acid functionalized Au nanoflare probe. Needing neither time-consuming and costly isolation of exosomes from the plasma sample nor transfection means, the Au nanoflare probe can directly enter the plasma exosomes to generate fluorescent signal quantitatively by specifically targeting miR-1246. Only 40 μL of plasma is needed to incubate 4 h with the probe, giving signal sensitive enough to distinguish samples of breast cancer to normal control. Using plasma miR-1246 level detected by our assay as a marker, we differentiated 46 breast cancer patients from 28 healthy controls with 100% sensitivity and 92.9% specificity at the best cutoff. This simple, accurate, sensitive, and cost-effective liquid biopsy by the Au nanoflare probe is potent to be developed as a noninvasive breast cancer diagnostic assay for clinical adaption.

A 2D metal–organic framework (MOF) of {[Cu(Dcbb)(Bpe)]·Cl}n (1, H2DcbbBr = 1-(3,5-dicarboxybenzyl)-4,4′-bipyridinium bromide, Bpe = trans-1,2-bis(4-pyridyl)ethylene)) has been prepared. MOF 1 associates with the thymine-rich (T-rich), single-stranded probe DNA (ss-DNA, denoted as P-DNA) labeled with fluorophore FAM (FAM = carboxyfluorescein) and quenches the FAM emission to give a nonemissive P-DNA@1 hybrid (off state). The P-DNA in the hybrid subsequently captures the Hg2+ to give a rigid double-stranded DNA featuring T–Hg2+–T motif (ds-DNA@Hg2+) and detach from MOF 1, triggering the recovery of the FAM fluorescence (on state). Upon subsequent addition of I–, Hg2+ was further sequestrated from the ds-DNA@Hg2+ duplex, driven by the stronger Hg–I coordination. The released P-DNA is resorbed by MOF 1 to regain the initial P-DNA@1 hybrid (off state). The P-DNA@1 sensor thus detects Hg2+ and I– sequentially via a fluorescence “off–on–off” mechanism. The sensor is highly selective and sensitive, yielding detec...

From a three-dimensional (3D) metal-organic framework (MOF) of {[Cu(Cmdcp)(phen)(H2O)]2·9H2O}n (1, H3CmdcpBr = N-carboxymethyl-(3,5-dicarboxyl)pyridinium bromide, phen = phenanthroline), a sensitive and selective fluorescence sensor has been developed for the simultaneous detection of ebolavirus conserved RNA sequences and ebolavirus-encoded microRNA-like (miRNA-like) fragment. The results from molecular dynamics simulation confirmed that MOF 1 absorbs carboxyfluorescein (FAM)-tagged and 5(6)-carboxyrhodamine, triethylammonium salt (ROX)-tagged probe ss-DNA (probe DNA, P-DNA) by π…π stacking and hydrogen bonding, as well as additional electrostatic interactions to form a sensing platform of P-DNAs@1 with quenched FAM and ROX fluorescence. In the presence of targeted ebolavirus conserved RNA sequences or ebolavirus-encoded miRNA-like fragment, the fluorophore-labeled P-DNA hybridizes with the analyte to give a P-DNA@RNA duplex and released from MOF 1, triggering a fluorescence recovery. Simultaneous detection of two target RNAs has also been realized by single and synchronous fluorescence analysis. The formed sensing platform shows high sensitivity for ebolavirus conserved RNA sequences and ebolavirus-encoded miRNA-like fragment with detection limits at the picomolar level and high selectivity without cross-reaction between the two probes. MOF 1 thus shows the potential as an effective fluorescent sensing platform for the synchronous detection of two ebolavirus-related sequences, and offer improved diagnostic accuracy of Ebola virus disease.

A mild and operationally simple copper-catalyzed vinylogous aerobic oxidation of β,γ- and α,β-unsaturated esters is described. This method features good yields, broad substrate scope, excellent chemo- and regioselectivity, and good functional group tolerance. This method is additionally capable of oxidizing β,γ- and α,β-unsaturated aldehydes, ketones, amides, nitriles, and sulfones. Furthermore, the present catalytic system is suitable for bisvinylogous and trisvinylogous oxidation. Tetramethylguanidine (TMG) was found to be crucial in its role as a base, but we also speculate that it serves as a ligand to copper(II) triflate to produce the active copper(II) catalyst. Mechanistic experiments conducted suggest a plausible reaction pathway via an allylcopper(II) species. Finally, the breadth of scope and power of this methodology are demonstrated through its application to complex natural product substrates.

Inspired by the enormous importance attributed to the biological function of miRNA, we pour our attention into the design and synthesis of four ruthenium(II) complexes and evaluate their applications as miR-185 detection agents by spectroscopic measurements. It was found that all complexes can form sensing platform for the detection of the complementary target miR-185 through the introduction of carboxyfluorescein (FAM) labeled single stranded DNA (P-DNA), giving the detection limits of 0.42nM for Ru 1, 0.28nM for Ru 2, 0.32nM for Ru 3, 0.85nM for Ru 4, all with instantaneous detection time in 1min. The results of the binding constant, fluorescence anisotropy (FA) and polyacrylamide gel electrophoresis experiments (PAGE) revealed that the ruthenium(II) complexes prefer to bind P-DNA other than hybrid duplexes DNA@RNA upon recognition, resulting in the detection of miR-185. These results provide useful suggestions in the new type of metal-based miRNA detection agents.

A water soluble and stable metal-organic framework (MOF) [Cu(Dcbcp)(bpe)] n ( 1 , Dcbcp = N-(3,5-dicarboxylbenzyl)-(3-carboxyl) pyridinium, bpe = 1,2-bis(4-pyridyl)ethylene) was synthesized. MOF 1 possesses a three-dimensional open framework with large pores and has a high affinity toward carboxyfluorescein (FAM) or 5(6)-carboxyrhodamine, triethylammonium salt (ROX)-tagged single-stranded probe DNA (P-DNA) through π stacking, electrostatic interactions, thus quenching the fluorescence of tag. The two formed P-DNA@ 1 systems can be applied for simultaneous detection of Dengue virus (DENV) and Zika virus (ZIKV) RNA sequences, which is attributed to the different affinities of MOF 1 with P-DNA and the double-stranded DNA/RNA formed upon recognition. With the same detection time of 36 min and 2 min, the detection limits are 332 and 192 pM with the single detection method, 184 and 121 pM with synchronous fluorescence detection method. Both assays are highly specific and not interfered by other mismatched RNA sequences, even down to single-base mismatched RNA sequences. There was no cross-reaction between the two probes for synchronous detection. Comparing these two methods, synchronous fluorescence analysis improves the detection efficiency by saving the time and increasing the detection limits, which may attribute to its avoiding the interference of Raleigh light scattering signal to the fluorescence signal.

Reactions of La(NO3)3·6H2O with the polar, tritopic quaternized carboxylate ligands N-carboxymethyl-3,5-dicarboxylpyridinium bromide (H3CmdcpBr) and N-(4-carboxybenzyl)-3,5-dicarboxylpyridinium bromide (H3CbdcpBr) afford two water-stable metal–organic frameworks (MOFs) of {[La4(Cmdcp)6(H2O)9]}n (1, 3D) and {[La2(Cbdcp)3(H2O)10]}n (2, 2D). MOFs 1 and 2 absorb the carboxyfluorescein (FAM)-tagged probe DNA (P-DNA) and quench the fluorescence of FAM via a photoinduced electron transfer (PET) process. The nonemissive P-DNA@MOF hybrids thus formed in turn function as sensing platforms to distinguish conservative linear, single-stranded RNA sequences of Sudan virus with high selectivity and low detection limits of 112 and 67 pM, respectively (at a signal-to-noise ratio of 3). These hybrids also exhibit high specificity and discriminate down to single-base mismatch RNA sequences.

We report herein five sensing platforms for the detection of five gastric cancer associated microRNAs (miRNAs). The sensing platforms are hybrids formed from a water-stable metal organic framework (MOF) {[Cu(dcbb)2(H2O)2]·10H2O}n (1, H2dcbbBr=1-(3,5-dicarboxybenzyl)-4,4'-bipyridinium bromide), respectively with five carboxyfluorescein (FAM) labeled probe single-stranded DNA (probe ss-DNA, denoted as P-DNA). Within the hybrid, MOF 1 tightly interacts with the P-DNA through electrostatic and/or π-stacking interactions and results in fluorescence quenching of FAM via a photo-induced electron transfer (PET) process. In the presence of the complementary target miRNAs miR-185, miR-20a, miR-92b, miR-25 and miR-210, which are expressed abnormally in the plasma of gastric carcinoma patients, P-DNA is released from the surface of MOF 1 ascribed to the stronger base pair matching, leading to the FAM fluorescence recovery. Each P-DNA@1 system is effective and reliable for the detection of its complementary target miRNA with the detection limits from 91 to 559pM, and is not interfered by other four miRNA sequences.