Asymmetric Nanopore Sensor for Logic Detection of Dam and M.SssI Methyltransferases in Combination of DNA Walker and Autocatalytic Hybridization Reaction.

The detection of DNA methyltransferase (MTase) was crucial for understanding gene expression regulation, cancer mechanisms, and various biological processes, contributing significantly to disease diagnosis and drug development. Herein, a nanopore sensor based on cascaded signal amplification of DNA walker and autocatalytic hybridization reaction (AHR) was developed for the ultrasensitive determination of various MTases. In the presence of Dam MTase, the hairpin structure HD underwent methylation and cleavage by DpnI endonuclease, forming T-DNA fragments. These T-DNA fragments were used to activate the DNA walker, which moved across the surface of magnetic beads step by step, generating a large quantity of initiator I by cleaving the substrate. The initiator I subsequently activated the AHR. The AHR included a hybridization chain reaction (HCR) amplifier and a catalytic hairpin assembly (CHA) convertor. The HCR amplifier generated multiple novel CHA triggers, which activated the CHA convertor. This, in turn, stimulated the HCR amplifier, creating an AHR circuit that resulted in the formation of numerous DNA nanowires. These DNA nanowires were adsorbed onto the G4-PAMAM-modified nanopore surface under the influence of an electric field, thereby altering the surface charge of the nanopore and changing the ionic rectification curve. The detection limit of the Dam MTase nanopore sensor reached 0.0002 U/mL. By modification of the recognition sites of the probes, this nanopore system could also be used for the detection of M.SssI MTase. Moreover, a four-input parallel concatenated logic circuit (AND//INHIBIT-OR) had been constructed and applied for the multivariate detection of Dam MTase and M.SssI MTase, presenting a novel conceptual model for advancing the construction of nanopore logic gate systems and their applications in biosensing.

Photoelectron-transfer-effect grafting: Validation of a generalized strategy for fluorescence and photoelectrochemical dual-mode detection of hydrogen sulfide.

BACKGROUND: The progress of modern research is constantly fueled by the convergence of multiple technologies. Despite the enormous potential of both fluorescence (FL) and photoelectrochemical (PEC) technologies, the development of synergistic PEC-FL sensing platforms that combine the advantages of both is still in its early stages due to their relatively recent inception. Hydrogen sulfide (H2S), possessing dual irritant and asphyxiating traits, poses challenges for environmental preservation and human health. The development of the PEC-FL detection methodology for H2S in complex environmental settings is imperative. RESULTS: Combining FL and PEC sensing techniques, this work presented a new concept of photoinduced electron-transfer (PET) effect grafting for dual-mode fluorescence and PEC analysis. Briefly, a well-designed fluorescent molecule (BTFM-DNP) featuring the PET effect was synthesized and implemented to modulate the photoelectric response of the indium tin oxide (ITO)/BiOI photocathode electrode. After reacting with H2S, the thiolysis of dinitrophenyl ether eliminated the intramolecular PET effect and recovered the significant fluorescence of the probe. Remarkably, the newly formed 2,4-dinitrobenzenethiol (DBT) with strong electron-withdrawing groups was then grafted to the ITO/BiOI photoelectrode and achieved the successful transfer of the PET process, resulting in a sharp decrease in photocurrent. The as-developed dual-mode protocol exhibited good performance in terms of ultra-sensitivity, high selectivity, fast response, and a wide detection range from 1 pM to 80 µM. SIGNIFICANCE: The newly developed PEC-FL sensing platform can be applied to detect H2S levels in both the environment and food. This study demonstrates a promising synergy between fluorescent probes and PEC sensors, offering a novel perspective on the advancement of multi-mode analysis techniques. This approach has the potential to significantly enhance detection accuracy and reliability.

Cascading CRISPR/Cas and Nanozyme for Enhanced Organic Photoelectrochemical Transistor Detection with Triple Signal Amplification.

Innovative signal amplification and transduction play pivotal roles in bioanalysis. Herein, cascading CRISPR/Cas and the nanozyme are integrated with electronic amplification in an organic photoelectrochemical transistor (OPECT) to enable triple signal amplification, which is exemplified by the miRNA-triggered CRISPR/Cas13a system and polyoxometalate nanozyme for OPECT detection of miRNA-21. The CRISPR/Cas13a-enabled release of glucose oxidase could synergize with peroxidase-like SiW12 to induce catalytic precipitation on the photogate, inhibiting the interfacial mass transfer and thus the significant suppression of the channel current. The as-developed OPECT sensor demonstrates good sensitivity and selectivity for miRNA-21 detection, with a linear range from 1 fM to 10 nM and an ultralow detection limit of 0.53 fM. This study features the integration of bio- and nanoenzyme cascade and electronic triple signal amplification for OPECT detection.

Molecule Engineering Metal-Organic Framework-Based Organic Photoelectrochemical Transistor Sensor for Ultrasensitive Bilirubin Detection.

The functionalization of metal-organic frameworks (MOFs) with organic small molecules by in situ postsynthetic modification has garnered considerable attention. However, the precise engineering of recognition sites using this method remains rarely explored in optically controlled bioelectronics. Herein, employing the Schiff base reaction to embed the small molecule (THBA) into a Zr-MOF, we fabricated a hydroxyl-rich MOF on the surface of titanium dioxide nanorod arrays (U6H@TiO2 NRs) to develop light-sensitive gate electrodes with tailored recognition capabilities. The U6H@TiO2 NR gate electrodes were integrated into organic photoelectrochemical transistor (OPECT) sensing systems to tailor a sensitive device for bilirubin (I-Bil) detection. In the presence of I-Bil, coordination effects, hydrogen bonding, and π-π interactions facilitated strong binding between U6H@TiO2 NRs and the target I-Bil. The electron-donating property of I-Bil influenced the gate voltage, enabling precise control of the channel status and modulation of the channel current. The OPECT device exhibited exceptional analytical performance toward I-Bil with wide linearity ranging from 1 × 10-16 to 1 × 10-9 M and a low limit detection of 0.022 fM. Leveraging the versatility of small molecules for boosting the functionalization of materials, this work demonstrates the great potential of the small molecule family for OPECT bioanalysis and holds promise for the advancement of OPECT sensors.

Transforming waste into valuables: Preparation and evaluation of dual-ligand hydrophobic charge-induction chromatography using two poor performing ligands.

In conventional chromatographic ligand screening, underperforming ligands are often dismissed. However, this practice may inadvertently overlook potential opportunities. This study aims to investigate whether these underperforming ligands can be repurposed as valuable assets. Hydrophobic charge-induction chromatography (HCIC) is chosen as the validation target for its potential as an innovative chromatographic mode. A novel dual-ligand approach is employed, combining two suboptimal ligands (5-Aminobenzimidazole and Tryptamine) to explore enhanced performance and optimization prospects. Various dual-ligand HCIC resins with different ligand densities were synthesized by adjusting the ligand ratio and concentration. The resins were characterized to assess appearance, functional groups, and pore features using SEM, FTIR, and ISEC techniques. Performance assessments were conducted using single-ligand mode resins as controls, evaluating the selectivity against human immunoglobulin G and human serum albumin. Static adsorption experiments were performed to understand pH and salt influence on adsorption. Breakthrough experiments were conducted to assess dynamic adsorption capacity of the novel resin. Finally, chromatographic separation using human serum was performed to evaluate the purity and yield of the resin. Results indicated that the dual-ligand HCIC resin designed for human antibodies demonstrates exceptional selectivity, surpassing not only single ligand states but also outperforming certain high-performing ligand types, particularly under specific salt and pH conditions. Ultimately, a high yield of 83.9 % and purity of 96.7 % were achieved in the separation of hIgG from human serum with the dual-ligand HCIC, significantly superior to the single-ligand resins. In conclusion, through rational design and proper operational conditions, the dual-ligand mode can revitalize underutilized ligands, potentially introducing novel and promising chromatographic modes.

Hydrogen-bond tuned conjugated architectures for nitric oxide sensing in single-benzene framework: Advances and mechanistic insights.

In contrast to the conventional fluorescence enhancement resulting from the cessation of the photoinduced electron transfer effect upon capturing nitric oxide (NO) by o-phenylenediamine, we found an interesting fluorescence quench within small molecule fluorophores characterized by intramolecular hydrogen bonding. Herein, the integration of a push-pull electron system with intramolecular hydrogen bonding onto an ultra-small fluorophore was employed to fabricate a hydrogen bond-tuned single benzene core fluorescent probe with an exceptional fluorescence quantum yield of 26 %, denoted as HSC-1. By virtue of its small size and low molecular weight (mere 192 g/mol), it demonstrated superior solubility and biocompatibility. Given the optimized conditions, HSC-1 manifested extraordinary linearity in detecting NO concentrations ranging from 0.5 to 60 µM, with an outstanding detection limit of 23.8 nM. Theoretical calculations unraveled the photophysical properties of hydrogen bonding-related probe molecules and highlighted the NO sensing mechanism. This pioneering work offers an important platform for the design of small fluorescence probes only with a single benzene core applied to NO sensing, which will potentially emerge as a new frontier in the area.

Improving the hydrothermal stability of Al-rich Cu-SSZ-13 zeolite via Pr-ion modification.

Al-rich (Si/Al = 4-6) Cu-SSZ-13 has been recognized as one of the potential catalysts to replace the commercial Cu-SSZ-13 (Si/Al = 10-12) towards ammonia-assisted selective catalytic reduction (NH3-SCR). However, poor hydrothermal stability is a great obstacle for Al-rich zeolites to meet the catalytic applications containing water vapor. Herein, we demonstrate that the hydrothermal stability of Al-rich Cu-SSZ-13 can be dramatically enhanced via Pr-ion modification. Particularly, after high-temperature hydrothermal aging (HTA), CuPr1.2-SSZ-13-HTA with an optimal Pr content of 1.2 wt% exhibits a T80 (temperature window of NO conversion above 80%) window of 225-550 °C and a T90 window of 250-350 °C. These values are superior to those of Cu-SSZ-13-HTA (225-450 °C for T80 and no T90 window). The results of X-ray diffraction Rietveld refinement, electron paramagnetic resonance (EPR) and spectral characterization reveal that Pr ions mainly located in the eight-membered rings (8MRs) in SSZ-13 zeolite can inhibit the generation of inactive CuOx during hydrothermal aging. This finding is further supported by density functional theory (DFT) calculations, which suggest that the presence of Pr ions restrains the transformation from Cu2+ ions in 6MRs into CuOx, resulting in enhanced hydrothermal stability. It is also noted that an excessive amount of Pr ions in Cu-SSZ-13 would result in the production of CuOx that causes the decline of catalytic performance. The present work provides a promising strategy for creating a hydrothermally stable Cu-SSZ-13 zeolite catalyst by adding secondary metal ions.

Reticular Heterojunction for Organic Photoelectrochemical Transistor Detection of Neuron-Specific Enolase.

Reticular heterojunctions on the basis of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have sparked considerable interest in recent research endeavors, which nevertheless have seldom been studied in optoelectronic biosensing. In this work, its utilization for organic photoelectrochemical transistor (OPECT) detection of the important cancer biomarker of neuron-specific enolase (NSE) is reported. A MOF@COF@CdS quantum dots (QDs) heterojunction is rationally designed to serve as the photogating module against the polymeric channel. Linking with a sandwich complexing event, target-dependent alternation of the photogate is achieved, leading to the changed photoelectric conversion efficiency as indicated by the amplified OPECT signals. The proposed assay demonstrates good analytical performance in detecting NSE, featuring a linear detection range from 0.1 pg mL-1 to 100 ng mL-1, with a detection limit of 0.033 pg mL-1.

Photoresponsive Hydrogen-Bonded Organic Frameworks-Enabled Organic Photoelectrochemical Transistors for Sensitive Bioanalysis.

A facile route for exponential magnification of transconductance (gm) in an organic photoelectrochemical transistor (OPECT) is still lacking. Herein, photoresponsive hydrogen-bonded organic frameworks (PR-HOFs) have been shown to be efficient for gm magnification in a typical poly(ethylene dioxythiophene):poly(styrenesulfonate) OPECT. Specifically, 450 nm light stimulation of 1,3,6,8-tetrakis (p-benzoic acid) pyrene (H4TBAPy)-based HOF could efficiently modulate the device characteristics, leading to the considerable gm magnification over 78 times from 0.114 to 8.96 mS at zero Vg. In linkage with a DNA nanomachine-assisted steric hindrance amplification strategy, the system was then interfaced with the microRNA-triggered structural DNA evolution toward the sensitive detection of a model target microRNA down to 0.1 fM. This study first reveals HOFs-enabled efficient gm magnification in organic electronics and its application for sensitive biomolecular detection.

Oxygen Vacancy-Mediated CuWO4/CuBi2O4 Samples with Efficient Charge Transfer for Enhanced Catalytic Activity toward Photodegradation of Pharmacologically Active Compounds.

Photocatalytic degradation is a promising method for controlling the increasing contamination of the water environment due to pharmacologically active compounds (PHACs). Herein, oxygen vacancy (OV)-modulated Z-scheme CuWO4/CuBi2O4 hybrid systems were fabricated via thermal treatment by loading of CuWO4 nanoparticles with OVs on CuBi2O4 surfaces. The synthesized CuWO4/CuBi2O4 hybrid samples exhibited an enhanced photodegradation ability to remove PHACs under visible-light irradiation. More importantly, an optimized sample (10 wt % CuWO4/CuBi2O4) exhibited superior catalytic activity and excellent recycling stability for PHAC photodegradation. In addition, possible degradation paths for PHAC removal over the CuWO4/CuBi2O4 hybrid systems were proposed. The enhanced photocatalytic performance could be attributed to the efficient separation and transfer of photoformed charge pairs via the Z-scheme mechanism. This Z-scheme mechanism was systematically analyzed using trapping experiments of active species, ultraviolet photoelectron spectroscopy, electron spin resonance, and the photodepositions of noble metals. The findings of this study can pave the way for developing highly efficient Z-scheme photocatalytic systems for PHAC photodegradation.

Nanofluidic sensing platform for PNK assay using nonlinear hybridization chain reaction and its application in DNA logic circuit.

In this study, a polyethyleneimine (PEI)/Zr4+-functionalized nanofluidic sensing platform based on nonlinear hybridization chain reaction (NHCR) was developed for PNK activity assay. With the existence of PNK, the hairpin HPNK was cleaved by λ exonuclease, liberating the initiator T-DNA. Then T-DNA triggered the nonlinear HCR in solution and the reaction products were absorbed onto the nanopore, which changed the surface charge of nanofluidic device and could be detected by current-voltage characteristic curves. Compared to traditional linear HCR, the nonlinear HCR exhibits a higher sensitivity and order of growth kinetics, making it a powerful signal amplifier in bioanalysis. Due to the powerful amplification efficiency of nonlinear HCR, high sensitivity of the nanopore and specific recognition site of PNK/λ-Exo, an ultrasensitive and selective PNK sensing approach had been developed and applied to precisely quantitate the PNK activity with a LOD of 0.0001 U/mL. Moreover, utilizing this nanofluidic system as a foundation, we constructed a logic circuit that utilized PNK, adenosine diphosphate (ADP), and (NH4)2SO4 as input elements. ADP and (NH4)2SO4 had a crucial function in facilitating the PNK to regulate the DNA logic gate. By modifying the target and inhibitors, the nanofluidic device could detect a variety of stimuli and execute more advanced logical operations.

Biological Transformation of AgI on MOF-on-MOF-Derived Heterostructures: Toward Polarity-Switchable Photoelectrochemical Biosensors for Neuron-Specific Enolase.

The sensitive detection of neuron-specific enolase (NSE) as a biomarker for lung cancer at an early stage is critical but has long been a challenge. The emergence of polarity-switchable photoelectrochemical (PEC) bioanalysis has opened up new avenues for developing highly sensitive NSE sensors. In this study, we present such a biosensor depending on the bioinduced AgI transition on MOF-on-MOF-derived semiconductor heterojunctions. Specifically, treatment of ZnO@In2O3@AgI by bioproduced H2S can in situ generate the ZnO@In2O3@In2S3@Ag2S heterojunction, with the photocurrent switching from the cathodic to anodic one due to the changes in the carrier transfer pathway. Linking an NSE-targeted sandwich immunorecognition with labeled alkaline phosphatase (ALP) catalyzed generation of H2S, such a phenomenon was correlated to NSE concentration with good performance in terms of selectivity and sensitivity and a low detection limit of 0.58 pg/mL. This study offered a new perspective on the use of MOF-on-MOF-derived heterostructures for advanced polarity-switchable PEC bioanalysis.

Ultrasensitive fluorescence detection of multiple DNA methyltransferases based on DNA walkers and hyperbranched rolling circle amplification.

The accurate and ultrasensitive detection of multiple methyltransferases was in great request for clinical diagnosis and epigenetic therapy. Here, a novel fluorescence assay was proposed for ultrasensitive CpG methyltransferase (M.SssI) and DNA adenine methyltransferase (Dam) activity detection based on hyperbranched rolling circle amplification (HRCA) and DNA walkers. The biosensor showed an extremely high sensitivity due to the dual-amplification strategy of HRCA and DNA walker. The LOD of the biosensor for M.SssI and Dam methyltransferase was estimated at 0.0004 U/mL and 0.001 U/mL, respectively. Without the presence of M.SssI methyltransferase, the corresponding recognition site of hairpin HM was cleaved by HpaII endonuclease, generating a DNA fragment (T-DNA) and inducing the DNA walker-HRCA reaction. Since the HRCA products contained numerous double-strand DNA (dsDNA), SYBR Green I could be embedded in the dsDNA, leading to a high fluorescent signal. In the presence of M.SssI methyltransferase, the corresponding recognition site of hairpin HM was methylated and the HpaII endonuclease-catalyzed stem of hairpin HM dissociation was hindered, leading to no DNA fragment (T-DNA) present. Hence, the DNA walker-HRCA reaction was not initiated and the fluorescent signal of SYBR Green I remained at a low level. Similarly, DNA adenine methyltransferase (Dam) and its inhibitors could also be detected by redesigning hairpin HD with the Dam recognition sequences. Furthermore, the sensing system was applied to analyze the endogenic Dam methyltransferase in the real samples such as E. coli cell lysate.

Metal-organic framework-derived nitrogen-doped carbon-confined CoSe2 anchored on multiwalled carbon nanotube networks as an anode for high-rate sodium-ion batteries.

Metal selenides, as potential alternative candidates for sodium storage, have promising applicability due to their high theoretical specific capacity. However, their huge volume change and sluggish electrode kinetics during sodium ion uptake and release processes can result in insufficient cycling life and inferior rate performance, hindering their practical application. Herein, nitrogen (N)-doped carbon-confined cobalt selenide anchored on multiwalled carbon nanotube networks (denoted as CoSe2@NC/MWCNTs) was designed and successfully built through a selenization process with ZIF-67 MOF as the template. The existence of the interconnected MWCNT network plays a crucial role in not only enhancing the electronic conductivity and ion/electron-transfer efficiency but also ensuring structural stability. Consequently, the optimized CoSe2@NC/MWCNTs composite delivers a high reversible capacity of 479.6 mA h g-1 at a current rate of 0.2 A g-1, accompanied by a 92.0% capacity retention over 100 cycles and a predominant rate performance of 227.4 mA h g-1 even under 20 A g-1 when examined as the anode in Na-ion batteries. Moreover, the kinetic behaviors were confirmed using CV profiles at various rates, as well as the galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). Besides, the HRTEM images clearly reveal the sodium-ion storage mechanism of the CoSe2 hybrid. These results make CoSe2@NC/MWCNTs a prospective anode material in advanced sodium-ion batteries.

Engineering of Portable Smartphone Integrated with Liposome-Encapsulated Curcumin for Onsite Visual Ratiometric Fluorescence Imaging of Hypochlorite.

Precisely onsite monitoring of hypochlorite (ClO- ) is of great significance to guide its rational use, reducing/avoiding its potential threat toward food safety and human health. Considering ClO- could quench fluorescence of curcumin (CCM) by oxidizing the o-methoxyphenol of CCM into benzoquinone, a portable ratiometric fluorescence sensor integrated with smartphone was designed for realizing the visual point-of-care testing (POCT) of ClO- . The amphiphilic phospholipid polymer was used as carrier to wrap curcumin, forming a novel liposome-encapsulated CCM, which provided a scaffold to bind with [Ru(bpy)3 ]2+ through electrostatic interaction, thus assembling [Ru(bpy)3 ]2+ -functionalized liposome-encapsulated CCM ([Ru(bpy)3 ]2+ @CCM-NPs). Further integrated with smartphone, visual imaging of [Ru(bpy)3 ]2+ @CCM-NPs could be achieved and the accurate onsite detection of ClO- could be realized with a detection limit of 66.31 nM and a linear range of 0.2210 to 80.0 µM. In addition, the sensor could monitor ClO- in real samples with an onsite detection time of ∼154.0 s.

Ultrasensitive and Label-Free Detection of Multiple DNA Methyltransferases by Asymmetric Nanopore Biosensor.

DNA methylation is catalyzed by a family of DNA methyltransferases that play crucial roles in various biological processes. Therefore, an ultrasensitive methyltransferase assay is highly desirable in biomedical research and clinical diagnosis. However, conventional assays for the detection of DNA methyltransferase activity often involve radioactive labeling, costly equipment, and laborious operation. In this study, an ultrasensitive and label-free method for detecting DNA adenine methyltransferase (Dam) and CpG methyltransferase (M.SssI) was developed using the nanopore technique coupled with DNA cascade signal amplification reactions. A hairpin DNA (HD) comprising of the methylation-responsive sequences was skillfully designed. In the presence of Dam methyltransferase, the corresponding recognition site of hairpin HD was methylated and specifically cleaved by DpnI endonuclease, thus forming a DNA fragment that induces the catalytic hairpin assembly and hybridization chain reaction (CHA-HCR). The generated products could be absorbed onto the Zr4+-coated nanopore, resulting in an ion current rectification signal change. Considering the high sensitivity of the nanopore and excellent specificity toward the recognition of methyltransferase/endonuclease, our developed method could detect both Dam and M.SssI methyltransferases in the same sensing platform. Furthermore, the designed nanopore sensor could realize the multiplex detection of Dam and M.SssI methyltransferases after integration with the cascaded INHIBIT-AND logic gate. This ultrasensitive methyltransferase assay holds great promise in the field of cancer diagnosis.

Rational Utilization of Photoelectrochemistry of Photosystem II for Self-Powered Photocathodic Detection of MicroRNA in Cells.

The photoanode, photosystem II (PSII)/hierarchical inverse opal (IO) TiO2, is coupled to the complementary photocathode, PbS quantum dots (QDs)/DNA probes, which is then integrated into a two-compartment photoelectrochemical (PEC) cell to achieve a self-powered system to enable photocathodic detection of microRNA-10b from HeLa cells. In such a system, all of the PSII catalytic products, i.e., electrons, protons, and O2, were rationally utilized and could overcome the general issue of varied O2 levels in photocathodic detection. The correlation between the target-triggered formation of the DNA complexes and the catalytic reduction of the dissolved O2 makes possible the steady microRNA-10b detection with good sensitivity and selectivity. This work has unveiled the ability of PSII to construct self-powered detecting devices and shed light on its application in new arenas.

Three-dimensional microspheres constructed with MoS2 nanosheets supported on multiwalled carbon nanotubes for optimized sodium storage.

Molybdenum disulfide (MoS2) has been regarded as a promising anode material in the field of sodium-ion batteries (SIBs), with the advantages of high theoretical capacity and large interlayer spacings. Unfortunately, its intrinsic poor electrical conductivity and large volume changes during the sodiation/desodiation reactions still limit its practical application. To deal with this shortcoming, we built MoS2 nanosheet/multiwalled carbon nanotube (denoted as MoS2-MSs/MWCNTs) composites with a three-dimensional (3D) micro-spherical structure, assembled in situ from MoS2 nanosheets. These nanosheets are connected to each other by the MWCNTs network, which provides a highly conductive pathway for electrons/ions through interparticle and intraparticle interfaces, accelerating charge transfer and ion diffusion capabilities. More importantly, the carbon network can boost electrical conductivity and relieve structural strain. Consequently, the as-prepared MoS2-MSs/MWCNTs composite presents a high reversible specific capacity of 519 mA h g-1 at 0.1 A g-1 after 100 cycles with a capacity retention of 94.4% and excellent rate performance (227 mA h g-1 at 10 A g-1). Outstanding cycling stability was also achieved (327.1 mA h g-1 over 1000 cycles at 2 A g-1) and was characterized by scanning electron microscopy (SEM) analysis. Our findings provide a simple and effective strategy to explore anode materials with advanced sodium storage properties.

Twin Nanopipettes for Real-Time Electrochemical Monitoring of Cytoplasmic Microviscosity at a Single-Cell Level.

Cytoplasmic microviscosity (CPMV) plays essential roles in governing the diffusion-mediated cellular processes and has been recognized as a reliable indicator of the cellular response of many diseases and malfunctions. Current CPMV studies are exclusively established by probe-assisted optical methods, which nevertheless necessitate the complicated synthesis and delivery of optical probes into cells and thus the issues of biocompatibility and bio-orthogonality. Using twin nanopipettes integrated with a patch-clamp system, a practical electrochemical single-cell measurement is presented, which is capable of real-time and long-term CPMV detection without cell disruption. Specifically, upon the operation of the twin nanopipettes, the cellular CPMV status, which is correlated to cytoplasmic ionic mobility, could be sensibly transduced via the ionic current passing through the nanosystem. The average CPMV value of HeLa cells was detected as ca. 86 cP. Notably, the correlation between chemotherapy and CPMV alterations makes this approach possible for the real-time and long-term assessment of the evolution of external stimuli, as exemplified by the two natural products taxol and colchicine. Integrated with the patch-clamp setup, this study features the first use of twin nanopipettes for electrochemical CPMV monitoring of single living cells, and it is expected to inspire more interest in the exploitation of dual- and multiple nanopipettes for advanced single-cell analysis.

Photocontrolled Nanopipette Biosensor for ATP Gradient Electroanalysis of Single Living Cells.

Emerging nanopipette tools have demonstrated substantial potential for advanced single-cell analysis, which plays vital roles from fundamental cellular biology to biomedical diagnostics. Highly recyclable nanopipettes with easy and quick regeneration are of special interest for precise and multiple measurements. However, existing recycle strategies are generally plagued by operational complexity and limited efficiency. Light, acting in a noncontact way, should be the ideal external stimulus to address this issue. Herein, we present the photocontrolled nanopipette capable of probing cellular adenosine triphosphate (ATP) gradient at single-cell level with good sensitivity, selectivity, and reversibility, which stems from the use of ATP-specific azobenzene (Azo)-incorporated DNA aptamer strands (AIDAS) and thereby the sensible transduction of variable nanopore size by the ionic currents passing through the aperture. Photoisomerized conformational change of the AIDAS by alternative UV/vis light stimulation ensures its noninvasive regeneration and repeated detection. Inducement and inhibition of the cellular ATP could also be probed by this nanosensor.