Aptasensor based on gold nanostructure-decorated 2D Cu metal-organic framework nanosheets for highly sensitive and specific electrochemical lipopolysaccharide detection.

Detecting lipopolysaccharide (LPS) using electrochemical methods is significant because of their exceptional sensitivity, simplicity, and user-friendliness. Two-dimensional metal-organic framework (2D-MOF) that merges the benefits of MOF and 2D nanostructure has exhibited remarkable performance in constructing electrochemical sensors, notably surpassing traditional 3D-MOFs. In this study, Cu[tetrakis(4-carboxylphenyl)porphyrin] (Cu-TCPP) and Cu(tetrahydroxyquinone) (Cu-THQ) 2D nanosheets were synthesized and applied on a glassy carbon electrode (GCE). The 2D-MOF nanosheets, which serve as supporting layers, exhibit improved electron transfer and electronic conductivity characteristics. Subsequently, the modified electrode was subjected to electrodeposition with Au nanostructures, resulting in the formation of Au/Cu-TCPP/GCE and Au/Cu-THQ/GCE. Notably, the Au/Cu-THQ/GCE demonstrated superior electrochemical activity because of the 2D morphology, redox ligand, dense Cu sites, and improved deposition of flower-like Au nanostructure based on Cu-THQ. The electron transfer specific surface area was increased by the improved deposition of Au nanostructures, which facilitates enriched binding of LPS aptamer and significantly improved the detection performance of Apt/Au/Cu-THQ/GCE electrochemical aptasensor. The limit of detection for LPS reached 0.15 fg/mL with a linear range of 1 fg/mL - 100 pg/mL. The proposed aptasensor demonstrated the ability to detect LPS in serum samples with satisfactory accuracy, indicating significant potential for clinical diagnosis.

On-Site-Activated Transmembrane Logic DNA Nanodevice Enables Highly Specific Imaging of Cancer Cells by Targeting Tumor-Related Nucleolin and Intracellular MicroRNA.

The ability to specifically image cancer cells is essential for cancer diagnosis; however, this ability is limited by the false positive associated with single-biomarker sensors and off-site activation of "always active" nucleic acid probes. Herein, we propose an on-site, activatable, transmembrane logic DNA (TLD) nanodevice that enables dual-biomarker sensing of tumor-related nucleolin and intracellular microRNA for highly specific cancer cell imaging. The TLD nanodevice is constructed by assembling a tetrahedral DNA nanostructure containing a linker (L)-blocker (B)-DNAzyme (D)-substrate (S) unit. AS-apt, a DNA strand containing an elongated segment and the AS1411 aptamer, is pre-anchored to nucleolin protein, which is specifically expressed on the membrane of cancer cells. Initially, the TLD nanodevice is firmly sealed by the blocker containing an AS-apt recognition zone, which prevents off-site activation. When the nanodevice encounters a target cancer cell, AS-apt (input 1) binds to the blocker and unlocks the sensing ability of the nanodevice for miR-21 (input 2). The TLD nanodevice achieves dual-biomarker sensing from the cell membrane to the cytoplasm, thereby ensuring cancer cell-specific imaging. This TLD nanodevice represents a promising strategy for the highly reliable analysis of intracellular biomarkers and a promising platform for cancer diagnosis and related biomedical applications.

DNAzyme-Amplified Cascade Catalytic Hairpin Assembly Nanosystem for Sensitive MicroRNA Imaging in Living Cells.

Sensitive imaging of microRNAs (miRNAs) in living cells is significant for accurate cancer clinical diagnosis and prognosis research studies, but it is challenged by inefficient intracellular delivery, instability of nucleic acid probes, and limited amplification efficiency. Herein, we engineered a DNAzyme-amplified cascade catalytic hairpin assembly (CHA)-based nanosystem (DCC) that overcomes these challenges and improves the imaging sensitivity. This enzyme-free amplification nanosystem is based on the sequential activation of DNAzyme amplification and CHA. MnO2 nanosheets were used as nanocarriers for the delivery of nucleic acid probes, which can resist the degradation by nucleases and supply Mn2+ for the DNAzyme reaction. After entering into living cells, the MnO2 nanosheets can be decomposed by intracellular glutathione (GSH) and release the loaded nucleic acid probes. In the presence of target miRNA, the locking strand (L) was hybridized with target miRNA, and the DNAzyme was released, which then cleaved the substrate hairpin (H1). This cleavage reaction resulted in the formation of a trigger sequence (TS) that can activate CHA and recover the fluorescence readout. Meanwhile, the DNAzyme was released from the cleaved H1 and bound to other H1 for new rounds of DNAzyme-based amplification. The TS was also released from CHA and involved in the new cycle of CHA. By this DCC nanosystem, low-abundance target miRNA can activate many DNAzyme and generate numerous TS for CHA, resulting in sensitive and selective analysis of miRNAs with a limit of detection of 5.4 pM, which is 18-fold lower than that of the traditional CHA system. This stable, sensitive, and selective nanosystem holds great potential for miRNA analysis, clinical diagnosis, and other related biomedical applications.

Neoadjuvant Camrelizumab for Non-Small Cell Lung Cancer: A Retrospective Multicenter, Real-World Study (CTONG2004).

BACKGROUND: Camrelizumab has shown encouraging efficacy in advanced non-small cell lung cancer (NSCLC), either as monotherapy or combined with chemotherapy. However, evidence of neoadjuvant camrelizumab for NSCLC remains lacking. METHODS: Patients with NSCLC treated with neoadjuvant camrelizumab-based therapy followed by surgery between December 2020 and September 2021 were retrospectively reviewed. Demographic and clinical data, details of neoadjuvant therapy and surgical information were retrieved. RESULTS: In this multicenter retrospective real-world study, 96 patients were included. Ninety-five patients (99.0%) received neoadjuvant camrelizumab combined with platinum-based chemotherapy, with a median of 2 cycles (range 1-6). The median interval from the last dose to surgery was 33 days (range 13-102 days). Seventy patients (72.9%) underwent minimally invasive surgery. Lobectomy was the most frequent surgical procedure (94 [97.9%]). The median estimated intraoperative blood loss was 100 mL (range 5-1200 mL), and the median operative time was 3.0 h (range 1.5-6.5 h). The R0 resection rate was 93.8%. Twenty-one patients (21.9%) experienced postoperative complications, with the most common being cough and pain (both 6 [6.3%]). The overall response rate was 77.1% (95% CI 67.4-85.0%), and the disease control rate was 93.8% (95% CI 86.9-97.7%). Twenty-six patients (27.1%, 95% CI 18.5-37.1%) had pathological complete response. Neoadjuvant treatment-related adverse events of grade ≥ 3 were reported in seven patients (7.3%), with the most frequent being abnormal liver enzymes (two [2.1%]). No treatment-related deaths were reported. CONCLUSION: The real-world data indicated that camrelizumab-based therapy had promising efficacy for NSCLC in the neoadjuvant setting, with manageable toxicities. Prospective studies investigating neoadjuvant camrelizumab are warranted.

Identification of TCR rearrangements specific for genetic alterations in EGFR-mutated non-small cell lung cancer: results from the ADJUVANT-CTONG1104 trial.

Tumor response T cells, which have specific T cell receptor (TCR) rearrangements in tumor-infiltrating lymphocytes, determine their ability to interact with the mutation-derived neoantigens presented by antigen-presenting cells. Little is known about the genetic alterations related to specific TCR clones in non-small cell lung cancer (NSCLC) patients who have an epidermal growth factor receptor (EGFR) mutation. In this study, tumor tissues were collected from 101 patients with stage II/III resectable NSCLC with an EGFR mutation (57 patients were treated with gefitinib and 44 were treated with chemotherapy) in the ADJUVANT-CTONG1104 trial for high-throughput TCRß V region and exome sequencing. Ten clonal TCRs were associated with EGFR exon 19 deletion (del), EGFR exon 21 mutation (L858R), RB1 alteration, TP53 exon 4/5 missense mutation, TP53 nonsense mutation, or copy number gains in NKX2-1 and CDK4. Among the TCRs, there was frequent use of Vß20-1Jß2-3 specifically for EGFR exon 19 del or Vß9Jß2-1 specifically for EGFR exon 21 mutation (L858R), and these were significantly associated with favorable overall survival (OS) for NSCLC patients harboring EGFR exon 19 del or exon 21 L858R, particularly in the adjuvant gefitinib setting. Moreover, in comparison with the chemotherapy-preferable (CP) group, higher frequencies of Vß20-1Jß2-3 and Vß9Jß2-1 were found in the highly TKI-preferable (HTP) or TKI-preferable (TP) groups. Altogether, we identified ten TCR rearrangements specific for genetic alterations in NSCLC. Importantly, high abundance Vß20-1Jß2-3 or Vß9Jß2-1 may be an immune biomarker for guiding adjuvant gefitinib decisions for NSCLC patients harboring EGFR exon 19 del or EGFR exon 21 L858R.

NanoSuit-Assisted Liquid-Cell Scanning Electron Microscopy Enables Dynamic Gold Nanoparticle Monitoring for the Aggregation and Transmembrane Processes in Living Cells.

Dynamic observation of the behaviors of nanomaterials in the cellular environment is of great significance in mechanistic investigations on nanomaterial-based diagnostics and therapeutics. Realizing label-free observations with nanometer resolution is necessary but still has major challenges. Herein, we propose a NanoSuit-assisted liquid-cell scanning electron microscopy (NanoSuit-LCSEM) method that enables imaging of the behaviors of nanoparticles in living cells. Taking A549 cells and gold nanoparticles (AuNPs) as a cell-nanoparticle interaction model, the NanoSuit-LCSEM method showed a significantly improved resolution to 10 nm, which is high enough to distinguish single and two adjacent 30 nm AuNPs in cells. The continuous observation time for living cells is extended to 30 min, and the trajectories and velocities for the transmembrane movement of AuNP aggregates are obtained. This study provides a new approach for dynamic observation of nanomaterials in intact living cells and will greatly benefit the interdisciplinary research of nanomaterials, nanomedicine, and nanotechnology.

Isolation of Structurally Heterogeneous TCR-CD3 Extracellular Vesicle Subpopulations Using Caliper Strategy.

Cells in different states can release diverse types of extracellular vesicles (EVs) that participate in intracellular communication or pathological processes. The identification and isolation of EV subpopulations are significant to explore their physiological functions and clinical value. In this study, structurally heterogeneous T-cell receptor (TCR)-CD3 EVs were proposed and verified for the first time using a caliper strategy. Two CD3-targeting aptamers were designed in the shape of a caliper with an optimized probe distance and were assembled on gold nanoparticles (Au-Caliper) to distinguish TCR-CD3 monomeric and dimeric EVs (m/dCD3 EVs) in skin-transplanted mouse plasma. Phenotyping and sequencing analysis revealed clear heterogeneity in the isolated m/dCD3 EVs, providing the potential for mCD3 EVs as a candidate biomarker of acute cellular rejection (ACR) and holding great prospects for distinguishing EV subpopulations based on protein oligomerization states.

Highly Efficient Isolation and Sensitive Detection of Small Extracellular Vesicles Using a Paper-Based Device.

Small extracellular vesicles (sEVs) play important roles in mediating intercellular communication and regulating biological processes. Facile sEV isolation is the essential and preliminary issue for their function investigation and downstream biomedical applications, while the traditional methods are challenged by tedious procedures, low purity, low yield, and potential damage. In this work, we developed an sEV isolation paper-based device (sEV-IsoPD) based on a three-dimensional (3D) paper chip, which is composed of a porous membrane for size exclusion and a metal-organic framework (MOF)/antibody-modified paper for immunoaffinity capture. In combination with a peristaltic pump-driven flow system, the sEV-IsoPD can efficiently isolate EV from cell culture medium and serum. Compared with the ultracentrifugation method, sEV-IsoPD exhibited a 5.1 times higher yield (1.7 × 109 mL-1), 1.6 times higher purity (1.6 × 1011 mg-1), and 7.5 times higher recovery (77.3%) with only 8.3% of the time (30 min) and 1.0% of the instrument cost ($710). Moreover, sEV concentration can be visually detected in a quantitative manner with this paper-based device with a linear range from 3.0 × 106 to 3.0 × 1010 mL-1 and a detection limit of 2.2 × 106 mL-1. The sEV-IsoPD provides an efficient and practical approach for the rapid isolation and visible detection of sEVs, which are promising for the preparation of sEVs and diagnosis of disease.

Dual-Locked DNAzyme Platform for In Vitro and In Vivo Discrimination of Cancer Cells.

Imaging of tumor-associated microRNAs (miRNAs) can provide abundant information for cancer diagnosis, whereas the occurrence of trace amounts of miRNAs in normal cells inevitably causes an undesired false-positive signal in the discrimination of cancer cells during miRNA imaging. In this study, we propose a dual-locked (D-locked) platform consisting of the enzyme/miRNA-D-locked DNAzyme sensor and the honeycomb MnO2 nanosponge (hMNS) nanocarrier for highly specific cancer cell imaging. For a proof-of-concept demonstration, apurinic/apyrimidinic endonuclease 1 (APE1) and miR-21 were chosen as key models. The hMNS nanocarrier can efficiently release the D-locked DNAzyme sensor in living cells due to the decomposition of hMNS by glutathione, which can also supply Mn2+ for DNAzyme cleavage. Ascribing to the smart design of the D-locked DNAzyme sensor, the fluorescence signal can only be generated by the synergistic response of APE1 and miR-21 that are overexpressed in cancer cells. Compared with the miRNA single-locked DNAzyme sensor and the small-molecule (ATP)/miRNA D-locked DNAzyme sensor, the proposed enzyme (APE1)/miRNA D-locked DNAzyme sensor exhibited 2.6-fold and 2.4-fold higher discrimination ratio (Fcancer/Fnormal) for cancer cell discrimination, respectively. Owing to the superior performance, the D-locked strategy can selectively generate a fluorescence signal in cancer cells, facilitating accurate discrimination of cancer both in vitro and in vivo. Furthermore, this D-locked platform is easily adaptable toward other target molecules by redesigning the DNA sequences. The outstanding performance and expansibility of this D-locked platform holds promising prospects for cancer diagnosis and related biomedical applications.

Light-Controlled Recruitable Hybridization Chain Reaction on Exosome Vehicles for Highly Sensitive MicroRNA Imaging in Living Cells.

Sensitive imaging of intracellular microRNA (miRNA) in living cells is of great significance. Isothermal hybridization chain reaction (HCR)-based methods, although have been widely used to monitor intracellular low-abundance miRNA, are still subjected to the challenges of limited signal amplification efficiency and compromised imaging resolution. In this work, we design a light-controlled recruitable HCR (LCR-HCR) strategy that enables us to well overcome these limitations. Exosomes as delivery and recruitment vehicles are modified with three cholesterol-modified hairpins (H1, H2, and H3), in which H1 is for anchoring target miRNA and H2 and H3 with photocleavable linkers (PC-linkers) are designed for spatiotemporal HCR. By controllably releasing probes with high local concentrations to efficiently trigger HCR and further recruiting the generated double-stranded DNA (dsDNA) polymers instead of dispersion in the cytoplasm, the LCR-HCR method can significantly improve the imaging contrast by confining all of the reactants on exosome vehicles. For a proof-of-concept demonstration, the miR-21 was analyzed by LCR-HCR with a limit of detection (LOD) down to 3.3 pM (corresponding to 165 amol per 50 µL) in vitro and four times higher response than traditional HCR in vivo. In general, the LCR-HCR method provides a powerful tool for sensitive miRNA imaging in living cells and cancer diagnosis.

Long-term continuous monitoring of microRNA in living cells using modified gold nanoprobe.

Long-term and continuous monitoring of the microRNA (miRNA) expression in living cells is essential in biomedical research, but it is currently limited by fast consumption and easy digestion of probes in the intracellular environment. Herein, we report polydopamine-modified gold nanoparticles (AuNPs@PDA) as protective and efficient nanocarriers for DNA hairpin probes (hpDNA), achieving long-term monitoring (48 h) of the miRNA (let-7a) levels in living cells after drug treatments. This method enabled excellent sensitivity and high selectivity toward let-7a with a limit of detection of 0.51 nM (n = 3) and a linear range from 1 to 100 nM. More importantly, AuNPs@PDA can not only efficiently improve the loading of hpDNA on each nanoparticle, but also effectively protect hpDNA from hydrolysis in the cell microenvironment, finally realizing the continuous monitoring of let-7a in living cells for 48 h. This simple method would be of great significance for drug screening and precision medicine.

Targeted Therapy in Early Stage Non-small Cell Lung Cancer.

OPINION STATEMENT: Tyrosine kinase inhibitors (TKIs) have dramatically improved tumor response rates and survival benefits in advanced oncogenic non-small-cell lung cancer (NSCLC). Given the impressive success, a renewed interest has been raised in the study of these agents in the perioperative setting. Preliminary data have shown dramatic effectiveness compared to conventional chemotherapy. Given the explicit need to induce durable responses and raise cure rates, we summarize the current progression, identify key challenges, and raise potential opportunities for perioperative targeted therapy that range from precise biomarkers to optimal adjuvant regimens for individual patients. As perioperative treatment indeed provides researchers with a unique platform to address the challenges mentioned above, investigators could obtain a comprehensive analysis of genomic profiling and trace resistance mechanisms. Multidisciplinary collaboration and adaptive clinical trial designs are warranted to integrate translational research into personalized perioperative TKI treatment paradigms.

Elucidating the interaction of rhizosphere bacteria and environmental factors in influencing active ingredient content of Lycium barbarum fruit in China.

AIMS: This study aimed to compare the differences in the bacterial community structure of Lycium barbarum rhizosphere and elucidate the contribution of rhizosphere bacteria to the active ingredients of L. barbarum fruit. METHODS AND RESULTS: This study investigated the soil and meteorological characteristics of L. barbarum rhizosphere during three growth stages across three production regions of China. High-throughput sequencing showed significant differences in the bacterial community diversity of L. barbarum rhizosphere across the three production regions, and norank_o_Gaiellales, norank_f_Anaerolineaceae and norank_f_AKYG1722 were the highest in Ningxia. In addition, regression and path analysis revealed that pH, norank_o_Gaiellales and norank_f_AKYG1722 significantly promoted the accumulation of total sugar and flavonoids in L. barbarum fruit directly or indirectly. Soil organic matter (SOM), norank_f_Anaerolineaceae and humidity significantly promoted the accumulation of betaine. The average temperature during the growth stages, norank_f_AKYG1722, and norank_o_Gaiellales promoted the accumulation of polysaccharides. CONCLUSIONS: The interaction between rhizosphere bacteria and environmental factors promoted the accumulation of active ingredients in L. barbarum fruits. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results provided insights to improve the quality of L. barbarum fruit.

Flexible Cuprous Triazolate Frameworks as Highly Stable and Efficient Electrocatalysts for CO2 Reduction with Tunable C2 H4 /CH4 Selectivity.

Cu-based metal-organic frameworks have attracted much attention for electrocatalytic CO2 reduction, but they are generally instable and difficult to control the product selectivity. We report flexible Cu(I) triazolate frameworks as efficient, stable, and tunable electrocatalysts for CO2 reduction to C2 H4 /CH4 . By changing the size of ligand side groups, the C2 H4 /CH4 selectivity ratio can be gradually tuned and inversed from 11.8 : 1 to 1 : 2.6, giving C2 H4 , CH4 , and hydrocarbon selectivities up to 51 %, 56 %, and 77 %, respectively. After long-term electrocatalysis, they can retain the structures/morphologies without formation of Cu-based inorganic species. Computational simulations showed that the coordination geometry of Cu(I) changed from triangular to tetrahedral to bind the reaction intermediates, and two adjacent Cu(I) cooperated for C-C coupling to form C2 H4 . Importantly, the ligand side groups controlled the catalyst flexibility by the steric hindrance mechanism, and the C2 H4 pathway is more sensitive than the CH4 one.

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Neuroblastoma (NB) is the most common extracranial solid tumor in children and has the features of high recurrence rate and low survival rate, and therefore, early diagnosis, treatment response evaluation, and recurrence monitoring are of great significance for NB patients. Liquid biopsy refers to the detection of cells and nucleic acids in fluid specimens, mainly blood. It is noninvasive and can overcome tumor heterogeneity, thus making it possible to achieve the early diagnosis and dynamic detection of NB. This review introduces the latest advances in clinical research on the application of liquid biopsy in NB.

Pearl Necklacelike Strategy Enables Quantification of Global 5-Hydroxymethylcytosine and 5-Formylcytosine by Inductively Coupled Plasma-Atomic Emission Spectrometry.

5-Hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC) are key intermediates of active DNA demethylation, for which the global detection methods are still restricted by high cost and long operation time. Here, we demonstrate a pearl necklacelike strategy to accurately quantify global 5hmC and 5fC in genomic DNA. In this method, the metal-organic framework (MOF), [Cu3(BTC)2] (denoted as HKUST-1, H3BTC = 1,3,5-benzenetricarboxylic acid), with a diameter of ∼30 nm that contains ∼15 000 copper ions (Cu2+) as the "super label" was in situ grown in the carboxylated 5hmC and 5fC loci of genomic DNA via the coordination between Cu2+ and the carboxyl group. After the acid digestion of MOF, the concentration of Cu2+, which has a quantitative relationship with the 5hmC/5fC content, was measured by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The metal element enrichment during MOF growth has amplified the signal by 4 orders of magnitude, realizing sensitive and accurate quantification of global 5hmC and 5fC in different tissues with a detection limit of 0.031% and 0.019‰ in DNA, respectively. The bisulfite- and mass spectrometry-free strategy is easily performed in almost all research and medical laboratories and would provide potential capability to quantify other candidate modifications in nucleotides.

Highly Sensitive Fluorescence Detection of Global 5-Hydroxymethylcytosine from Nanogram Input with Strongly Emitting Copper Nanotags.

Quantitative analysis of 5-hydroxymethylcytosine (5hmC) has remarkable clinical significance to early cancer diagnosis; however, it is limited by the requirement in current assays for large amounts of starting material and expensive instruments requring expertise. Herein, we present a highly sensitive fluorescence method, termed hmC-TACN, for global 5hmC quantification from several nanogram inputs based on terminal deoxynucleotide transferase (TdT)-assisted formation of fluorescent copper (Cu) nanotags. In this method, 5hmC is labeled with click tags by T4 phage ß-glucosyltransferase (ß-GT) and cross-linked with a random DNA primer via click chemistry. TdT initiates the template-free extension along the primer at the modified 5hmC site and then generates a long polythymine (T) tail, which can template the production of strongly emitting Cu nanoparticles (CuNPs). Consequently, an intensely fluorescent tag containing numerous CuNPs can be labeled onto the 5hmC site, providing the sensitive quantification of 5hmC with a limit of detection (LOD) as low as 0.021% of total nucleotides (S/N = 3). With only a 5 ng input (∼1000 cells) of genomic DNA, global 5hmC levels were accurately determined in mouse tissues, human cell lines (including normal and cancer cells of breast, lung, and liver), and urines of a bladder cancer patient and healthy control. Moreover, as few as 100 cells can also be distinguished between normal and cancer cells. The hmC-TACN method has great promise of being cost effective and easily mastered, with low-input clinical utility, and even for the microzone analysis of tumor models.

Polymerization retardation isothermal amplification (PRIA): a strategy enables sensitively quantify genome-wide 5-methylcytosine oxides rapidly on handy instruments with nanoscale sample input.

The current methods for quantifying genome-wide 5-methylcytosine (5mC) oxides are still scarce, mostly restricted with two limitations: assay sensitivity is seriously compromised with cost, assay time and sample input; epigenetic information is irreproducible during polymerase chain reaction (PCR) amplification without bisulfite pretreatment. Here, we propose a novel Polymerization Retardation Isothermal Amplification (PRIA) strategy to directly amplify the minute differences between epigenetic bases and others by arranging DNA polymerase to repetitively pass large electron-withdrawing groups tagged 5mC-oxides. We demonstrate that low abundant 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxycytosine (5caC) in genomic DNA can be accurately quantified within 10 h with 100 ng sample input on a laboratory real-time quantitative PCR instrument, and even multiple samples can be analyzed simultaneously in microplates. The global levels of 5hmC and 5fC in mouse and human brain tissues, rat hippocampal neuronal tissue, mouse kidney tissue and mouse embryonic stem cells were quantified and the observations not only confirm the widespread presence of 5hmC and 5fC but also indicate their significant variation in different tissues and cells. The strategy is easily performed in almost all research and medical laboratories, and would provide the potential capability to other candidate modifications in nucleotides.

Metastable Dumbbell Probe-Based Hybridization Chain Reaction for Sensitive and Accurate Imaging of Intracellular-Specific MicroRNAs In Situ in Living Cells.

Sensitive and accurate imaging of intracellular-specific microRNAs (miRNAs) in situ in living cells is seriously challenged by the susceptibility of nucleic acid probes and the low dynamics of the hybridization reaction in cellular environments. Herein, we engineer a set of new metastable dumbbell probes (M xDPs) to overcome these key limitations by concurrently boosting transfection, antidigestibility, assembly dynamics, and nanostructural uniformity. The M xDPs can maintain their stability up to 16 h in living cells and produce uniform and dense DNA nanostructures rapidly (<2 h) and specifically from a hybridization chain reaction (HCR). A sharp signal from the cascade accumulation of fluorescence resonance energy transfer (FRET) further minimizes the effect of system fluctuations. The M xDPs-based HCR (M xDPHCR) method showed identical performance in the analysis of miR-27a in cell lysate and buffer condition and obtained a limit of detection down to 3.2 pM (corresponding to 160 amol per 50 µL), which is 44-fold lower than on conventional hairpin probes. The M xDPHCR method clearly distinguished normal cells from tumor cells and provided more accurate quantitative information on the intracellular-specific miRNAs. The strategy would offer a powerful tool for visualizing and localizing desired nucleic acids in living cells.

In Situ Enzyme Immobilization with Oxygen-Sensitive Luminescent Metal-Organic Frameworks to Realize "All-in-One" Multifunctions.

Metal-organic frameworks (MOFs) for enzyme immobilization have already shown superior tunable and designable characteristics, however, their diverse responsive properties have rarely been exploited. In this work we integrated a responsive MOF into a MOF-enzyme composite with the purpose of designing an "all-in-one" multifunctional composite with catalytic and luminescence functions incorporated into a single particle. As a proof-of-concept, glucose oxidase (GOx) was encapsulated in situ within an oxygen (O2 )-sensitive, noble-metal-free, luminescent CuI triazolate framework (MAF-2), denoted as GOx@MAF-2. Owing to the rigid scaffold of MAF-2 and confinement effect, the GOx@MAF-2 composite showed significantly improved stability (shelf life of 60 days and heat resistance up to 80 °C) as well as good selectivity and recyclability. More importantly, owing to the O2 sensitivity of MAF-2, the GOx@MAF-2 composite exhibited a rapid and reversible response towards dissolved O2 , thereby allowing direct and ratiometric sensing of glucose without the need for chromogenic substrates, cascade enzymatic reactions, or electrode systems. High sensitivity with a detection limit of 1.4 µm glucose was achieved, and the glucose levels in human sera were accurately determined. This strategy has led to a new application for MOFs that can be facilely extended to other MOF-enzyme composites due to the multifunctionality of MOFs.