Switchable Probes Research Articles

Arthroscopic Debridement and Resection of a Bennett Lesion in a Collegiate Baseball Pitcher

Background: Overhead throwing athletes are predisposed to ossification along the superior to inferior posterior glenoid rim, termed thrower's exostosis or a Bennett lesion. These lesions can result in posterior shoulder pain during throwing and decreased shoulder range of motion, and they can be associated with posterior labral tears and undersurface rotator cuff tears. In this video technique, we describe the arthroscopic debridement and resection of a symptomatic unstable Bennett lesion in a collegiate baseball pitcher who had unsuccessful nonoperative treatment. Indications: Currently, there is no standard treatment algorithm for Bennett lesions. Arthroscopic intervention is typically indicated in overhead throwers who have unsuccessful nonoperative protocols, including stretching of the posterior capsule, strengthening of the rotator cuff, and injections. Technique Description: In the lateral decubitus position, standard posterior viewing and anterior working arthroscopic portals are created followed by diagnostic arthroscopy. A high anterior accessory portal is created to view the posterior labrum and evaluate for tears. The location of the Bennett lesion is determined using a switching stick or probe. In this case, an accessory posterior viewing portal and capsulotomy are created under spinal needle visualization and a 70° scope is utilized for an improved view. Through the capsulotomy, a motorized shaver and radiofrequency wand is used to work along the posterior inferior glenoid neck to expose the lesion. Once the lesion is fully demarked, a hooded bur is utilized to debride the entirety of the lesion back to the smooth bony surface of the glenoid neck. After resection, the capsule is left open to avoid overtightening the posterior capsule in overhead throwing athletes. Results: Arthroscopic debridement and resection of a symptomatic Bennett lesion in a collegiate baseball pitcher allowed the patient to return to pain-free pitching at the same level of collegiate play the following season. Discussion/Conclusion: An unstable Bennett lesion can be a source of pain in the overhead throwing athlete. If nonoperative treatment modalities fail to resolve symptoms, arthroscopic debridement and excision of this lesion utilizing a posterior capsulotomy and accessory posterior viewing portal as described in this video technique is a safe and effective surgical option. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

The Discovery of Highly Efficient and Promising ABA Receptor Antagonists for Agricultural Applications Based on APAn Modification.

Abscisic acid (ABA) is one of the many naturally occurring phytohormones widely found in plants. This study focused on refining APAn, a series of previously developed agonism/antagonism switching probes. Twelve novel APAn analogues were synthesized by introducing varied branched or oxygen-containing chains at the C-6' position, and these were screened. Through germination assays conducted on A. thaliana, colza, and rice seeds, as well as investigations into stomatal movement, several highly active ABA receptor antagonists were identified. Microscale thermophoresis (MST) assays, molecular docking, and molecular dynamics simulation showed that they had stronger receptor affinity than ABA, while PP2C phosphatase assays indicated that the C-6'-tail chain extending from the 3' channel effectively prevented the ligand-receptor binary complex from binding to PP2C phosphatase, demonstrating strong antagonistic activity. These antagonists showed effective potential in promoting seed germination and stomatal opening of plants exposed to abiotic stress, particularly cold and salt stress, offering advantages for cultivating crops under adverse conditions. Moreover, their combined application with fluridone and gibberellic acid could provide more practical agricultural solutions, presenting new insights and tools for overcoming agricultural challenges.

Development of a CRISPR/Cas12a-mediated aptasensor for Mpox virus antigen detection

The emergence and rapid spread of Mpox (formerly monkeypox) have caused significant societal challenges. Adequate and appropriate diagnostics procedures are an urgent necessity. Herein, we discover a pair of aptamers through the systematic evolution of ligands by exponential enrichment (SELEX) that exhibit high affinity and bind to different sites towards the A29 protein of the Mpox virus. Subsequently, we propose a facile, sensitive, convenient CRISPR/Cas12a-mediated aptasensor for detecting the A29 antigen. The procedure employs the bivalent aptamers recognition, which induces the formation of a proximity switch probe and initiates subsequent cascade strand displacement reactions, then triggers CRISPR/Cas12a DNA trans-cleavage to achieve the sensitive detection of Mpox. Our method enables selective and ultrasensitive evaluation of the A29 protein within the range of 1 ng mL−1 to 1 μg mL−1, with a limit of detection (LOD) at 0.28 ng mL−1. Moreover, spiked A29 protein recovery exceeds 96.9%, while the detection activity remains above 91.9% after six months of storage at 4 °C. This aptasensor provides a novel avenue for exploring clinical diagnosis in cases involving Mpox as facilitating development in various analyte sensors.

An integrated hinged dual-probe for co-target fast switching imaging.

The diversity of functional applications of atomic force microscopes is the key to the development of nanotechnology. However, the single probe configuration of the traditional atomic force microscope restricts the realization of different application requirements for the same target area of a single sample, and the replacement of the working probe will lead to the loss of the target area. Here, the design, simulation, fabrication, and application of a unique atomic force microscope dual-probe are presented, which consists of a pair of parallel cantilevers with a narrow gap and a U-shaped hinged probe base. The Integrated Hinged Dual-Probe (IHDP) is developed specifically for fast switching of probes working in limited space and independent and precise manipulation of each probe. The deflection signal sensing of two cantilevers is achieved simultaneously by a single laser beam, and the decoupled independent cantilever deflection signals do not interfere with each other. The switching of the working probe is achieved by a piezoelectric ceramic with a 2 µm stroke and U-shaped hinge structure, which is fast and does not require tedious and repetitive spatial position calibration. By measuring standard grid samples, IHDP exhibits excellent measurement and characterization capabilities. Finally, a working probe switching imaging experiment was conducted on solidified rat cardiomyocytes, and the experimental process and imaging results demonstrated the superiority of IHDP in switching probe scanning imaging of the same target area of a single sample. The two probes of IHDP can undergo arbitrary functionalization modifications, which helps achieve multidimensional information acquisition for a single target.

A hierarchically porous MOF confined CsPbBr3 quantum dots: Fluorescence switching probe for detecting Cu (II) and melamine in food samples

The hypersensitivity of Perovskite quantum dots (PeQDs) towards external environmental conditions and the water quenching of their fluorescence have limited their practical analytical applications. In this work highly luminescent CsPbBr3 was confined into a hierarchically porous ZIF-8 metal organic framework (HZIF-8) through a simple two step in situ growth method. XRD, FTIR, SEM, TEM, and XPS investigations confirmed the successful synthesis of the CsPbBr3/HZIF-8 nanocomposite. CsPbBr3 PeQDs are uniformly distributed within the HZIF-8 MOF matrix and exhibited intense green emission at 510 nm with a FWHM value of 25 nm in ambient conditions. The nanocomposite showed enhanced stability against moisture and UV light. The intense PL emission of the nanocomposite was well maintained in an aqueous solution also, with no noticeable change in fluorescence characteristics for 15 days of storage in aqueous solution. The CsPbBr3/HZIF-8 composite was then utilized as an on–off-on luminescent probe for the detection of Cu2+ metal ions and melamine in real samples. Because of the porous nature of the MOF, the target analytes can be quickly located and this nanosensor is found to be very sensitive toward Cu2+ and melamine detection. A linear relationship from 3 to 500 nM and 30–1500 nM was found for melamine and Cu2+ under an optimal experimental condition, with a limit of detection value of around 4.66 nM and 2.64 nM for Cu2+ and melamine respectively.

Assembling G-wire-induced pyrene excimer switching for microRNA amplified detection based on exonuclease III-assisted target recycling and Fe3O4@PDA nanoparticles

We reported a novel assembled G-wire-induced pyrene excimer switching probe for microRNA (miRNA) amplified detection on the basis of exonuclease III (Exo III)-assisted target recycling and Fe3O4@PDA nanoparticles. The multifunctional hairpin (HP) probe recognized and effectively bound to target miRNA, which formed a 3′-blunt terminal for Exo-III digestion and miRNA regeneration to initiate another Exo III-mediated cycling cleavage. After digestion, numerous HP-caged c-myc sequences were released, which were positively related to target miRNA and folded to the parallel G-quadruplex with K+. Additionally, Fe3O4 polydopamine nanoparticles (Fe3O4@PDA NPs)-based magnet separation was conducted to reduce background fluorescence signal, and parallel G-quadruplexes self-asembled into filamentous G-wires with Mg2+. G-wires generated from 5′-terminal pyrene-labeled c-myc sequences made close distance between two labeled pyrene molecules, and induced the “turn-on” fluorescence signal of pyrene excimer switching. Moreover, gamma-cyclodextrin (γ-CD) was added, which promoted pyrene moiety, causing signal amplification in pyrene excimer fluorescence. Therefore, miRNA was efficiently measured within the homogeneous solution. This method detected miRNA within the dynamic range of 1 pM to 5 nM, with the miR-141 limit of detection (LOD) being 99 fM. It distinguished perfect-matched and mismatched target miRNAs, and showed an accurate detection of miRNA levels in different cell lines and favorable reproducibility when analyzing miRNAs within spiked serum samples. We propose a promising method for G-wire-based biosensing in disease-related biomarkers detection.

Hairpin DNA-enabled ratiometric electrochemical aptasensor for detection of malathion

A hairpin DNA-enabled ratiometric electrochemical aptasensor is reported for sensitive and reliable detection of malathion (MAL). The approach employs hairpin DNA (ferrocene-labeled, Fc-hDNA) as a carrier to hybridize MAL aptamers (methylene blue-labeled, MB-Apt) to form double-stranded DNA structures on an electrode. The presence of MAL induces the removal of aptamers, and hDNA re-forms hairpin structures, causing a decrease in the oxidation current of MB (IMB) and an increase in the oxidation current of Fc (IFc). The ratiometric signal of IFc/IMB responds quantitatively to MAL concentrations. To compare analytical performances, a linear single-stranded DNA (ssDNA) is also used to construct the ssDNA-based aptasensor. We demonstrate that hairpin DNA possessing a rigid two-dimensional structure can improve the assembly efficiency of aptamers and the stability of redox probes. The approach combines the advantages of the ratiometric electrochemical method with hairpin DNA-based conformational switching probes, enabling hDNA-based aptasensor with enhanced sensitivity and reliability, offering a linear range of 0.001 to 1.0 ng mL-1. The platform was applied to detect MAL in lettuce, and the statistical analysis indicated that no significant differences were found between the developed platform and HPLC-MS.

Bright Green Light-Emitting Gold Nanoclusters Confined in Insulin as Selective Fluorescent Switch Probes for Sensing and Imaging of Copper Ions and Glutathione

In this study, an on–off–on fluorescence probe is developed for rapid, sensitive, and selective detection of Cu2+ ions and glutathione (GSH) based on green light-emitting insulin-capped gold nanoclusters (Ins/Au-NCs). Ins/Au-NCs with low toxicity and excellent stability were prepared by utilizing a simple and green strategy. Cu2+ ions can selectively decrease the fluorescence intensity of Ins/Au-NCs by an aggregation-caused quenching mechanism, which can be recovered in the presence of GSH. Under the optimized condition, the detection limits for determination of Cu2+ ions and GSH are estimated as 7.5 and 9.2 nM, with linear ranges of 0.05 to 1.7 μM and 0.05 to 1.5 μM, respectively. Chemical modeling was also employed to investigate the interaction of the Ins/Au-NCs probe with Cu2+, Hg2+, glutathione, and cysteine. The calculated molecular orbital energy well confirmed the experimental selective results obtained. Luminescence cellular imaging exhibited a sensitive response of the Ins/Au-NCs probe toward Cu2+ ions in breast cancer cells MCF-7, and thus, it potentially acted as an intracellular GSH probe in MCF-7 compared to the human fibroblast HFF cells. The as-prepared probe was successfully applied to low levels of Cu2+ ions and GSH in water and human serum samples. The designed Ins/Au-NCs-based probe may also provide a biocompatible platform for label-free GSH detection in biological and clinical implications that comprise staining and early prevention of cancer, AIDS, and Alzheimer’s and cardiovascular diseases.

Split-step birefringence simulation method for optical Kerr gates

A split-step birefringence simulation method is proposed to investigate the gating efficiency and intensity distribution of the Kerr signal field considering the evolution of the switch beam and probe beam in their path. Using this simulation method, we investigated the switch-beam power-dependent gating efficiency and conducted an experiment to prove its reliability. Furthermore, we analyzed the optical intensity distribution of the Kerr signal exiting the Kerr medium under different switch-beam powers. This study provides an effective theoretical tool for the design and optimization of optical Kerr gates.

A fluorescent pH switch probe for the ‘turn-on’ dual-channel discriminative detection of magnesium and zinc ions

A coumarin-based fluorescent probe is presented for the multi-channel reversible “ Turn-on ” detection of Mg 2+ ion (at 483 nm) and Zn 2+ ion (at 560 nm) as well as a base (450 nm) at different wavelengths with large Stokes shifts. • A coumarin-based probe HL is utilized for the dual channel ‘turn-on’ detection of Mg 2+ and Zn 2+ ions. • HL detects Mg 2+ and Zn 2+ ions at two different wavelengths with large Stokes shifts. • HL detects both metal ions by the inhibition of C=N bond rotation, PET and ESIPT while promoting CHEF. • Probe HL also functioned as a reversible fluorescent pH switch. • HL was utilized for the detection of Mg 2+ and Zn 2+ ions in human breast cancer cells. • Low-cost detection methods, paper-strips and polymer films, were used for the sensing of Mg 2+ and Zn 2+ ions. A coumarin-based fluorescent probe, HL (( E )-8-((benzo[d]thiazol-2-ylimino)methyl)-7-hydroxy-4-methyl-2H-chromen-2-one), is presented for the dual-channel “ Turn-on ” detection of Mg 2+ (at 483 nm) and Zn 2+ (at 560 nm) ions at two different wavelengths with large Stokes shifts. HL exhibits impressive detection limits and binding constants with both Mg 2+ and Zn 2+ ions. HL detected these ions by the inhibition of -C=N bond rotation and suppression of photoinduced electron transfer (PET) and excited state intramolecular proton transfer (ESIPT) while promoting chelation enhanced fluorescence (CHEF). For the detection of Mg 2+ and Zn 2+ ions, reversibility was achieved by using ATP. HL is not only sensitive and selective for the detection of Mg 2+ and Zn 2+ ions but also showed considerable reversible “ Turn-on-Turn-off ” fluorescent pH switch behavior. The DFT studies assisted in understanding the binding of Mg 2+ and Zn 2+ ions by the probe. HL was utilized to detect Mg 2+ and Zn 2+ ions in the human breast cancer cell line by fluorescence cell imaging studies while several low-cost detection methods were also illustrated.

An aptamer triple helix molecular switch for sensitive electrochemical assay of lipocalin 1 biomarker via dual signal amplifications.

Sensitively monitoring the concentration change of lipocalin 1 (LCN1) can provide data support for accurately diagnosing diabetic retinopathy and efficacy of treatment. Using a new aptamer triplex switch (ATS) probe and catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR) dual signal amplifications, a highly sensitive electrochemical and enzyme-free biosensor for detecting LCN1 is reported. The ATS probes recognize and bind LCN1 to change its structure and release ssDNA sequences, which trigger the capture of methylene blue (MB)-tagged DNA on the sensor electrode via the CHA and HCR reactions. These MB tags are then subjected to electrochemical measurements to obtain highly amplified current outputs to sensitively detect LCN1 from 5 pM to 1 nM with a detection limit of 0.85 pM. This sensor also exhibits high interfering protein discrimination capability and can be employed to monitor low levels of LCN1 in diluted tear samples. Our established sensor significantly outperforms current major LCN1 detection methods based on immunoassays and thus holds promising potential for evaluating the severity of diabetic retinopathy and monitoring treatment response.

Deconvoluting binding sites in amyloid nanofibrils using time-resolved spectroscopy.

Steady-state fluorescence spectroscopy has a central role not only for sensing applications, but also in biophysics and imaging. Light switching probes, such as ruthenium dipyridophenazine complexes, have been used to study complex systems such as DNA, RNA, and amyloid fibrils. Nonetheless, steady-state spectroscopy is limited in the kind of information it can provide. In this paper, we use time-resolved spectroscopy for studying binding interactions between amyloid-β fibrillar structures and photoluminescent ligands. Using time-resolved spectroscopy, we demonstrate that ruthenium complexes with a pyrazino phenanthroline derivative can bind to two distinct binding sites on the surface of fibrillar amyloid-β, in contrast with previous studies using steady-state photoluminescence spectroscopy, which only identified one binding site for similar compounds. The second elusive binding site is revealed when deconvoluting the signals from the time-resolved decay traces, allowing the determination of dissociation constants of 3 and 2.2 μM. Molecular dynamic simulations agree with two binding sites on the surface of amyloid-β fibrils. Time-resolved spectroscopy was also used to monitor the aggregation of amyloid-β in real-time. In addition, we show that common polypyridine complexes can bind to amyloid-β also at two different binding sites. Information on how molecules bind to amyloid proteins is important to understand their toxicity and to design potential drugs that bind and quench their deleterious effects. The additional information contained in time-resolved spectroscopy provides a powerful tool not only for studying excited state dynamics but also for sensing and revealing important information about the system including hidden binding sites.

Fluorescent Probes for Lipid Membranes: From the Cell Surface to Organelles

Biomembranes are ubiquitous lipid structures that delimit the cell surface and organelles and operate as platforms for a multitude of biomolecular processes. The development of chemical tools─fluorescent probes─for the sensing and imaging of biomembranes is a rapidly growing research direction, stimulated by a high demand from cell biologists and biophysicists. This Account focuses on advances in these smart molecules, providing a voyage from the cell frontier─plasma membranes (PM)─toward intracellular membrane compartments─organelles. General classification of the membrane probes can be based on targeting principles, sensing profile, and optical response. Probes for PM and organelle membranes are designed based on multiple targeting principles: conjugation with natural lipids or synthetic targeting ligands and in situ cell labeling by bio-orthogonal chemistry, conjugation to protein tags, and receptor-ligand interactions. Thus, to obtain membrane probes targeting PM with selectivity to one leaflet, we designed membrane anchor ligands based on a charged group and an alkyl chain. According to the sensing profile, we define basic membrane markers with constant emission and probes for biophysical and chemical sensing. The markers are built from classical fluorophores, exemplified by a series of bright cyanines and BODIPY dyes bearing the PM anchors (MemBright). Membrane probes for biophysical sensing are based on environment-sensitive fluorophores: (1) polarity-sensitive solvatochromic dyes; (2) viscosity-sensitive fluorescent molecular rotors; (3) mechanosensitive fluorescent flippers; and (4) voltage-sensitive electrochromic dyes. Our solvatochromic probes based on Nile Red (NR12S, NR12A, NR4A), Laurdan (Pro12A), and 3-hydroxyflavone (F2N12S) through polarity-sensing can visualize liquid ordered and disordered phases of lipid membranes, sense lipid order and its heterogeneity in cell PM, detect apoptosis, etc. Chemically sensitive probes, combining a dye, membrane-targeting ligand, and molecular recognition unit, enable the detection of pH, ions, redox species, lipids, and proteins at the biomembrane surface. In terms of the optical response profile, we can identify (1) fluorogenic (turn-on) probes, allowing background-free imaging; (2) ratiometric probes, e.g., solvatochromic probes, which enable ratiometric imaging by changing their emission/excitation color; (3) fluorescence lifetime-responsive probes, e.g., fluorescence molecular rotors and flippers, suitable for fluorescence lifetime imaging (FLIM); and (4) switchable probes, important for single-molecule localization microscopy. We showed that combining solvatochromic probes with on-off switching through a reversible binding specifically to cell PM enables the mapping of their biophysical properties with superior resolution. While the majority of efforts have been focused on PM, the probes for cellular organelles, such as endoplasmic reticulum, mitochondria, Golgi apparatus, etc., emerge rapidly. Thus, nontargeted solvatochromic probes can distinguish organelles by the emission color. Targeted solvatochromic probes based on Nile Red revealed unique signatures of polarity and lipid order of individual organelles and their different sensitivities to oxidative or mechanical stress. Lipid droplets, which are membraneless lipidic structures, constitute another interesting organelle target for probing the cell stress. Currently, we stand at the beginning of a long route with big challenges ahead, in particular (1) to achieve superior organelle specificity; (2) to label specific biomembrane leaflets, notably the inner leaflet of PM; (3) to detect lipid organization in a proximity of specific proteins; and (4) to probe biomembranes in tissues and animals.

BSA Capped gold Nanoclusters Modulated by Copper ion for Sensitive and Selective Detection of Histidine in Biological Fluid.

This research proposed a sample and environmentally sustainable technique for the synthesis of bovine serum albumin capped gold nanoclusters (BSA-AuNCs) with outstanding fluorescence. The synthesized BSA-AuNCs were investigated using various ways before being combined with Cu2+ to produce a fluorescent switch probe (BSA-AuNCs-Cu2+) for histidine determination. After adding Cu2+, the fluorescence of the BSA-AuNCs was quenched, the fluorescence intensity was enhanced after adding histidine due to good coordination between Cu2+ and histidine. The significant chelation of histidine with Cu2+ demonstrated the viability of developing a selective "switch on" probe for histidine detecting over other amino acids. Unlike existing fluorescent nanomaterial-based approaches for detecting histidine, this study promises good selectivity, high efficiency, and the avoiding of chemical solvents. The designed BSA-AuNCs-Cu2+ fluorescent probe demonstrated an acceptable linear detection range of 0 to 240 µM under optimum circumstances, with a detection limit of 0.9 µM. The BSA-AuNCs-Cu2+ system was investigated in rat serum and human urine, with recoveries ranging from 97.2 to 108.2%, demonstrating its potential applicability for histidine detection with favorable results.

Fluorogenic Dimers as Bright Switchable Probes for Enhanced Super-Resolution Imaging of Cell Membranes.

Super-resolution fluorescence imaging based on single-molecule localization microscopy (SMLM) enables visualizing cellular structures with nanometric precision. However, its spatial and temporal resolution largely relies on the brightness of ON/OFF switchable fluorescent dyes. Moreover, in cell plasma membranes, the single-molecule localization is hampered by the fast lateral diffusion of membrane probes. Here, to address these two fundamental problems, we propose a concept of ON/OFF switchable probes for SMLM (points accumulation for imaging in nanoscale topography, PAINT) based on fluorogenic dimers of bright cyanine dyes. In these probes, the two cyanine units connected with a linker were modified at their extremities with low-affinity membrane anchors. Being self-quenched in water due to intramolecular dye H-aggregation, they displayed light up on reversible binding to lipid membranes. The charged group in the linker further decreased the probe affinity to the lipid membranes, thus accelerating its dynamic reversible ON/OFF switching. The concept was validated on cyanines 3 and 5. SMLM of live cells revealed that the new probes provided higher brightness and ∼10-fold slower diffusion at the cell surface, compared to reference probes Nile Red and DiD, which boosted axial localization precision >3-fold down to 31 nm. The new probe allowed unprecedented observation of nanoscale fibrous protrusions on plasma membranes of live cells with 40 s time resolution, revealing their fast dynamics. Thus, going beyond the brightness limit of single switchable dyes by cooperative dequenching in fluorogenic dimers and slowing down probe diffusion in biomembranes open the route to significant enhancement of super-resolution fluorescence microscopy of live cells.

Fluorine-Nitrogen-Codoped Carbon Dots as Fluorescent Switch Probes for Selective Fe(III) and Ascorbic Acid Sensing in Living Cells.

High-quality fluorescent probes based on carbon dots (CDs) have promising applications in many fields owing to their good stability, low toxicity, high quantum yield, and low raw material price. The fluorine- and nitrogen-doped fluorescent CDs (NFCDs) with blue fluorescence was successfully synthesized using 3-aminophenol and 2,4-difluorobenzoic acid as the raw material by the hydrothermal method. The NFCDs as probe can be used to directly and indirectly detect Fe3+ (detection range: 0.1–150 μM and detection limit: 0.14 μM) and ascorbic acid (AA) (detection range: 10–80 μM and detection limit: 0.11 μM). The NFCDs-based probe shows exceptional selectivity and strong anti-interference for Fe3+ and ascorbic acid (AA). In addition, we examined the response of NFCDs to Fe3+ and AA in living cells, which showed that the timely use of AA can reduce the effects of iron poisoning. This has important biological significance. This means that using NFCDs as fluorescent probes is beneficial for Fe3+ and AA detection and observing their dynamic changes in living cells. Thus, this work may contribute to the study of Fe3+- and AA-related diseases.

Scanning probe microscope probe switching unit with electrical measurement for in situ multifunctional characterization: Design and preliminary application in tribocorrosion investigation

Scanning probe microscope (SPM) is a potent tool in nanotribology research. However, commercial environment control SPMs can install only one probe to perform one function at a time. Accordingly, this study developed a probe switching unit with electrical measurement for in situ multifunctional characterization. The unit mainly comprises a cover, a rotation stage, and a probe holder assembly. Four probes can be installed. One is electrically connected to perform tapping mode and electrical measurement such as Kelvin probe force microscope (0.01 mV resolution), while the other three are to perform contact mode. The rotation stage drives the assembly to switch probes to in situ measure multiple physical quantities in a controlled environment. The unit was preliminarily applied to investigate tantalum tribocorrosion. Based on the changing trends of wear amount and surface potential change, the wear process can be roughly divided into three stages, which may be caused by desorption of the adsorbed air, wear of the oxide film, and wear of the substrate, respectively. Moreover, wear can lead to a surface potential increment, which may partly contribute to the galvanic corrosion between the virgin area and the wear area. The unit may serve as a useful tool for nanotribology research.

Visible-light-driven molecularly imprinted self-powered sensor for atrazine with high sensitivity and selectivity by separating photoanode from recognition element

Atrazine (ATZ) is one of the most widely used and highly toxic triazine herbicides in the world. It is of vital significance to realize ATZ detection with high sensitivity, high selectivity and easy on-site feasibility. Herein, assembled with Ti-Fe-O nanotubes (NTs)/Ni(OH)2 photoanode and molecularly imprinted polymer (MIP) functionalized cathode, a novel molecularly imprinted self-powered sensor (SPS) based on visible-light-driven photo fuel cell (PFC) is developed for ATZ. The MIP cathode serves as the recognition element with advantages of low production cost, high mechanical strength and good stability, while the enzyme-free photoanode has excellent visible light activity and particularly catalytic effects on glucose, leading to spontaneously electron generation and driving the whole cell. By using [Fe(CN)6]3− as the electron transfer switch probe, the SPS can sense ATZ rapidly by the change of output power once ATZ is captured by the cathode. Based on the strategy of using typical photoanode with outstanding oxidative catalytic ability for fuel and placing the recognition element on the cathode separately, the proposed SPS demonstrates excellent power generation performance with a maximum open circuit potential (EOCV) of 0.79 V and a maximum output power density (Pmax) of 13.5 μW·cm−2. It shows a wide linear range of 0.002–21.6 ng·mL−1, a low detection limit of 0.61 pg·mL−1, and a prominent selectivity towards ATZ even in the presence of 100-fold interferents. A proof-of-concept for the integration of molecularly imprinted techniques with PFC and the innovative inspiration for wide used of SPS in complicated environmental system has therefore been provided.

Reuse of waste Myrica rubra for green synthesis of nitrogen-doped carbon dots as an “on-off-on” fluorescent probe for Fe3+ and ascorbic acid detection

As one kind of high nutrition fruits, abandoned Myrica rubra causes great waste due to short storage period. For resource utilization, we herein fabricated the Myrica rubra-based N-doped carbon dots (MN-CDs) by a facile/green hydrothermal method. MN-CDs, fabricated from four regions of China, displayed significant differences in their corresponding fluorescence intensities (FIs). Interestingly, different batches of waxberry samples from the same region (Wenzhou, China) exhibited slight differences in their FIs, and also an excellent anti-photobleaching and anti-salt capacity. Based on Fe3+-triggered quenching effect and fluorescent recovery by redox reaction of AA and Fe3+, MN-CDs were employed to construct an “on-off-on” switch probe for sequential detection of Fe3+ and ascorbic acid (AA). Through Zeta potential, UV spectrum, Stern-Volmer equation, and valence-conduction band theory, the Fe3+-triggered quenching belonged to a static quenching process, which resulted from the synergistic contribution of inner filtering effect and photo-induced electron transfer mechanisms. The linear ranges for Fe3+ and AA detections were 1–1000 and 0.1–1000 mM. The limits of detection were 0.3 μM for Fe3+ in environmental waters, and 0.03 μM for AA in pharmaceutical tablets and fruit juice samples. Under 365-nm UV lamp, the color changes of test papers were easily observed from dark blue and bright blue in the presence of Fe3+ and AA, and thus the MN-CDs-based switch probe could be satisfactorily used for visually qualitative detection of Fe3+ and AA outdoor with our naked eyes. To sum up, MN-CDs not only realize resource reutilization of abandoned Myrica rubra, but also offer an convenient outdoor approach for qualitative detection of Fe3+ and AA in complex matrices.

Modulating Angiogenesis by Proteomimetics of Vascular Endothelial Growth Factor.

Angiogenesis, formation of new blood vessels from the existing vascular network, is a hallmark of cancer cells that leads to tumor vascular proliferation and metastasis. This process is mediated through the binding interaction of VEGF-A with VEGF receptors. However, the balance between pro-angiogenic and anti-angiogenic effect after ligand binding yet remains elusive and is therefore challenging to manipulate. To interrogate this interaction, herein we designed a few sulfono-γ-AA peptide based helical peptidomimetics that could effectively mimic a key binding interface on VEGF (helix-α1) for VEGFR recognition. Intriguingly, although both sulfono-γ-AA peptide sequences V2 and V3 bound to VEGF receptors tightly, in vitro angiogenesis assays demonstrated that V3 potently inhibited angiogenesis, whereas V2 activated angiogenesis effectively instead. Our findings suggested that this distinct modulation of angiogenesis might be due to the result of selective binding of V2 to VEGFR-1 and V3 to VEGFR-2, respectively. These molecules thus provide us a key to switch the angiogenic signaling, a biological process that balances the effects of pro-angiogenic and anti-angiogenic factors, where imbalances lead to several diseases including cancer. In addition, both V2 and V3 exhibited remarkable stability toward proteolytic hydrolysis, suggesting that V2 and V3 are promising therapeutic agents for the intervention of disease conditions arising due to angiogenic imbalances and could also be used as novel molecular switching probes to interrogate the mechanism of VEGFR signaling. The findings also further demonstrated the potential of sulfono-γ-AA peptides to mimic the α-helical domain for protein recognition and modulation of protein-protein interactions.