AI-assisted mass spectrometry imaging with in situ image segmentation for subcellular metabolomics analysis.

Subcellular metabolomics analysis is crucial for understanding intracellular heterogeneity and accurate drug-cell interactions. Unfortunately, the ultra-small size and complex microenvironment inside the cell pose a great challenge to achieving this goal. To address this challenge, we propose an artificial intelligence-assisted subcellular mass spectrometry imaging (AI-SMSI) strategy with in situ image segmentation. Based on the nanometer-resolution MSI technique, the protonated guanine and threonine ions were respectively employed as the nucleus and cytoplasmic markers to complete image segmentation at the subcellular level, avoiding mutual interference of signals from various compartments in the cell. With advanced AI models, the metabolites within the different regions could be further integrated and profiled. Through this method, we decrypted the distinct action mechanism of isomeric drugs, doxorubicin (DOX) and epirubicin (EPI), only with a stereochemical inversion at C-4'. Within the cytoplasmic region, fifteen specific metabolites were discovered as biomarkers for distinguishing the drug action difference between DOX and EPI. Moreover, we identified that the downregulations of glutamate and aspartate in the malate-aspartate shuttle pathway may contribute to the higher paratoxicity of DOX. Our current AI-SMSI approach has promising applications for subcellular metabolomics analysis and thus opens new opportunities to further explore drug-cell specific interactions for the long-term pursuit of precision medicine.

Array electrochemiluminescence device with ultra-high sensitivity and selectivity for rapid visualized monitoring of trace radon in environment.

The World Health Organization has reported radioactive Rn gas as the second leading cause of lung cancer and gives an extreme limit to indoor Radon (Rn) concentration as 100 Bq/m3. To realize rapid and accurate Rn monitoring, we report an efficient visualized electrochemiluminescence (ECL) device for Rn detection with the lowest limit of detection (0.9 Bq/m3/3.6 Bq h m-3) compared to known Rn detection methods and the shortest measurement time (less than 5 h) among non-pump methods. In detail, an efficient Rn probe is prepared by Au nanoparticles, Pb2+ aptamer, as well as NH2-ssDNA co-reactant and then modified on ITO electrodes to obtain Rn detection devices. With tris(2,2'-bipyridyl)ruthenium(II)chloride (Ru(bpy)3Cl2) as an ECL emitter, the devices can exhibit ultra-high sensitivity and selectivity to trace Rn in environment via the ECL quenching caused by 210Pb, the relatively stable decay product of Rn. Furthermore, ECL imaging technology can be applied to realize the visualized Rn detection. An efficient up-response ECL detector was also invented to support this detection device to achieve accurate Rn detection in environment. This work reports noble gas ECL detection for the first time and provides an efficient strategy for rapid and accurate monitoring of trace Rn in environment.

Bipolar Electrode Array for Multiplexed Detection of Prostate Cancer Biomarkers.

Owing to the characteristics of high throughput, high flexibility, and convenient separation of the sensing and reporting reactions, the bipolar electrode (BPE) shows great potential in clinical analysis. However, there are some difficulties in the combination of BPEs and multiplex electrochemiluminescence (ECL) biosensing, such as the need for small sample consumption, multistep operations, and separated sample loading. In this paper, a microfluidic BPE array chip was fabricated toward multiplex detection of cancer biomarkers. With a special channel structure and the difference in flow resistance of channels of different sizes, the direction of liquid flow was successfully controlled. In this way, rapid and automatic multiplex sampling was achieved on the array, which would help improve the sensing efficiency and reduce the reagent consumption. The ECL BPE array chip served as an immunosensor for multiple prostate cancer biomarkers including prostate-specific antigen (PSA), interleukin-6 (IL-6), and prostate-specific membrane antigen (PSMA). The microfluidic BPE chip shows good reproducibility and high sensitivity. The limits of detection for PSA, IL-6, and PSMA are 0.093 ng/mL, 0.061 pg/mL, and 0.059 ng/mL, respectively. It also exhibits excellent performance in real sample analysis. The integrated ECL BPE array shows a good application prospect in clinical sensing of cancer biomarkers, as well as point-of-care testing.

Label-Free Electrochemiluminescence Imaging of Single-Cell Adhesions by Using Bipolar Nanoelectrode Array.

A label-free and fast approach for positive electrochemiluminescence (ECL) imaging of single cells by bipolar nanoelectrode array is proposed. The reduction of oxygen at a platinized gold nanoelectrode array in a closed bipolar electrochemical system is coupled with an oxidative ECL process at the anodic side. For elevating the ECL imaging contrast of single cells, a driving voltage of -2.0 V is applied to in situ generate oxygen confined beneath cells that is subsequently used for ECL imaging at 1.1 V. High oxygen concentration in the confined space resulting from steric hindrance generates prominent oxygen reduction current at the cathodic side and higher ECL intensity at the anodic side, allowing positive ECL imaging of the cells adhesion region with excellent contrast. Cell morphology and adhesion strength can be successfully imaged with high image acquisition rate. This approach opens a new avenue for label-free imaging of single cells.

Ultrasensitive Nucleic Acid Assay Based on AIE-Active Polymer Dots with Excellent Electrochemiluminescence Stability.

Aggregation-induced emission (AIE) active Pdots are attractive nanomaterials applied in electrochemiluminescence (ECL) fields, while the irreversible redox reaction of these Pdots is a prevailing problem, resulting in instability of ECL emission. Herein, we first designed and synthesized an AIE-active Pdot with reversible redox property, which contains a tetraphenylethene derivate and benzothiadiazole (BT) to achieve stable ECL emission. BT has a good rigid structure with excellent electrochemical behaviors, which is beneficial for avoiding the destruction of the conjugated structure as much as possible during the preparation of Pdots, thus maintaining good redox property. The tetraphenylethene derivate, as a typical AIE-active moiety, provides a channel for highly efficient luminescence in the aggregated states. The Pdots exhibited reversible and quasi-reversible electrochemical behaviors during cathodic and anodic scanning, respectively. The stable annihilation, reductive-oxidative, and oxidative-reductive ECL signals were observed. Subsequently, we constructed an ultrasensitive ECL biosensor based on the oxidative-reductive ECL mode for the detection of miRNA-21 with a detection limit of 32 aM. This work provides some inspiration for the future design of ECL materials featuring AIE-active property and stable ECL emission.

Aggregation-Induced Electrochemiluminescence of Conjugated Pdots Containing a Trace Ir(III) Complex: Insights into Structure-Property Relationships.

An approach to the design of iridium(III)-contained polytetraphenylethene Pdots that could exhibit highly efficient electrochemiluminescence (ECL) was proposed. The relationships of ECL performance between the iridium complex-embedded and end-capped aggregation-induced emission (AIE) active Pdots in aqueous media were investigated for the first time. The iridium complexes with cyclometalated ligand 6-phenylphenanthridine (pphent) were incorporated into the copolymers by either embedding (P0, P2-P5) or end-capping (P1) into the backbone via an ancillary 2,2'-bipyridine (bpy) ligand. Subsequently, the corresponding Pdots of P0-P5 encapsulated with poly(styrene-co-maleicanhydride) could be obtained by the nanoprecipitation method. Compared to Pdots0, Pdots2-Pdots5 with (pphent)2Ir(bpy) (M1) complex embedding, as the iridium complex content increases, ECL signals were decreased in the order of Pdots0 > Pdots2 > Pdots3 > Pdots4 > Pdots5; whereas among these Pdots of P0-P5, Pdots1 with M1 complex end-capping exhibited the highest ECL efficiency (relative to a Ru(bpy)32+ system of 18.9%) and 4.7-fold enhancement of the ECL signal compared to the parent Pdots of P0, which was mainly attributed to the good film conductivity of the completely conjugated architectures, thus prompting the intramolecular electron transfer. This work opened new avenues for designing highly efficient ECL emitters.

Quantitative Imaging of pN Intercellular Force and Energetic Costs during Collective Cell Migration in Epithelial Wound Healing.

Collective cell migration plays a key role in tissue repair, metastasis, and development. Cellular tension is a vital mechanical regulator during the force-driven cell movements. However, the contribution and mechanism of cell-cell force interaction and energetic costs during cell migration are yet to be understood. Here, we attempted to unfold the mechanism of collective cell movement through quantification of the intercellular tension and energetic costs. The measurement of pN intercellular force is based on a "spring-like" DNA-probe and a molecular tension fluorescence microscopy. During the process of wound healing, the intercellular force along with the cell monolayer mainly originates from actin polymerization, which is strongly related to the cellular energy metabolism level. Intracellular force at different spatial regions of wound and the energetic costs of leader and follower cells were measured. The maximum force and energy consumption are mainly concentrated at the wound edge and dynamically changed along with different stages of wound healing. These results indicated the domination of leader cells other than follower cells during the collective cell migration.

Fabrication of High-Density and Superuniform Gold Nanoelectrode Arrays for Electrochemical Fluorescence Imaging.

Nanoelectrode arrays have been widely used in electroanalytical applications. The challenge is to develop low-cost and simple approaches to the fabrication of superuniform and ultrasmall nanoelectrode arrays for improving analytical performance and imaging resolution. Here, superuniform and high-density gold nanoelectrode arrays with tunable electrode diameters and interelectrode distances have been fabricated by electrodeposition, followed by a simple mechanical polishing process. The fabricated free-standing arrays have a high density (108 cm-2) of nanoelectrodes (60, 140, and 200 nm in diameter), and can be used as closed bipolar electrode arrays to image electrochemical heterogeneity with micrometer spatial resolution. With the help of a confocal microscope, individual nanoelectrodes can be visualized and resolved from the reflected light. Thus, the nanoelectrode arrays are promising in electrochemical imaging with high spatial resolution.

Gold nanorod-assisted near-infrared light-mediated regulation of membrane ion channels activates apoptotic pathways.

We report a GNR-assisted NIR-activated tool that could open TRPV1 ion channels and regulate apoptotic protein expression, thereby inducing cell apoptosis, which might be an effective approach for cancer therapy.

Highly Efficient Aggregation-Induced Electrochemiluminescence of Polyfluorene Derivative Nanoparticles Containing Tetraphenylethylene.

The aggregation-induced electrochemiluminescence (AIECL) of polyfluorene derivative nanoparticles containing tetraphenylethylene (TPE) in aqueous media is reported in this work. The TPE unit limits the intramolecular free rotation of phenyl rings, as well as the π-π stacking interactions of molecules, which significantly enhances ECL signal of the polyfluorene nanoparticles. With co-reactants of tri-n-propylamine (TPrA) and S2O82-, the copolymer nanoparticles show visualized ECL emissions at both positive and negative potentials. The ECL efficiency of copolymer nanoparticles in solid state is 163% compared with that of standard ECL species, Ru(bpy)32+. And at negative potential, the ECL intensity of copolymer nanoparticles is even stronger with 6.5 times compared with that at positive potential. The ECL generation mechanisms are analyzed detailed by annihilation and co-reactant route transient ECL test (millisecond scale). This work provides a reference for the organic structure design for AIECL and shows promising potential in luminescent device and biological applications.

Recognition of plastic nanoparticles using a single gold nanopore fabricated at the tip of a glass nanopipette.

A single gold nanopore with high surface enhanced Raman spectroscopy (SERS) activity is fabricated on the tip of a glass nanopipette. Polystyrene (PS) nanospheres can be recognized from the SERS spectrum while passing through the single nanopore.

Electrochemiluminescence Energy Resonance Transfer System between RuSi Nanoparticles and Hollow Au Nanocages for Nucleic Acid Detection.

This paper describes an electrochemiluminescence resonance energy transfer (ECL-RET) system using Ru(bpy)32+-doped silica nanoparticles (RuSi NPs) as the ECL donor and hollow Au nanocages as the ECL acceptor. Tetrahedron DNA (TD) was used to construct the biosensing interface and control the distance (4.8 nm) between the ECL donor-acceptor pairs. The surface plasmon resonance (SPR) nanostructures, Au nanocages were assembled via the hairpin based sandwich assay. Due to the well overlap between the plasmon absorption spectrum of Au nanocages (628 nm) and the ECL emission spectrum of RuSi NPs (620 nm), high efficient energy transfer could occur. Subsequent cyclic DNA amplification further increased the binding amount of Au nanocages. Since the ECL inhibition is closely related with the binding amount of Au nanocages, a general "signal-off" ECL bioassay could thus be tailored with high sensitivity. At the optimized conditions, this ECL-RET system performed well with great stability and repeatability for nucleic acid detection in the range from 1.0 fM to 10 pM. This work manifested the great promise of hollow Au nanocages for an ECL-RET biosensor that to the best of our knowledge has not been reported. We believe that it could inspire more interest in the design and development of numerous other SPR nanostructures for advanced ECL-RET biosensors.

Vacuum Ultraviolet Laser Desorption/Ionization Mass Spectrometry Imaging of Single Cells with Submicron Craters.

Mass spectrometry imaging (MSI) is a crucial label-free method to distinguish the localization patterns in single cells. MALDI-TOF MS and ToF-SIMS are now bearing the responsibility. However, MALDI-TOF MS is limited to micron spatial resolution and ToF-SIMS suffers from severe molecular fragmentation. Here, we proposed a new MSI methodology of vacuum ultraviolet laser desorption/ionization (VUVDI) with high spatial resolution, achieving higher ion yields and less fragmentation compared with ToF-SIMS at submicron level. The fluorescence image and mass spectrum of VUVDI were obtained simultaneously. In addition, the adjustable laser fluence acquired selective detection for different molecular and fragmental ions, thus realizing molecular identification. Furthermore, MSIs of single cells with submicron craters were presented. These results suggest VUVDI is a potential mass spectrometry method that provides a soft ionization source and submicron spatial resolution for molecular analysis in life science.

Electrogenerated Chemiluminescence Imaging of Electrocatalysis at a Single Au-Pt Janus Nanoparticle.

Noble metal nanoparticles are promising catalysts in electrochemical reactions, while understanding the relationship between the structure and reactivity of the particles is important to achieve higher efficiency of electrocatalysis, and promote the development of single-molecule electrochemistry. Electrogenerated chemiluminescence (ECL) was employed to image the catalytic oxidation of luminophore at single Au, Pt, and Au-Pt Janus nanoparticles. Compared to the monometal nanoparticles, the Janus particle structure exhibited enhanced ECL intensity and stability, indicating better catalytic efficiency. On the basis of the experimental results and digital simulation, it was concluded that a concentration difference arose at the asymmetric bimetallic interface according to different heterogeneous electron-transfer rate constants at Au and Pt. The fluid slip around the Janus particle enhanced local redox reactions and protected the particle surface from passivation.

A paper-based SERS test strip for quantitative detection of Mucin-1 in whole blood.

A paper-based SERS test strip combining strengths of paper chip and Raman active substrate was demonstrated to overcome challenges in spectroscopic sensing of complicated samples and realize quantitative detection of disease markers in whole blood. The precisely controlled Au NPs were not only capable of generating condensed hot spots on the fibers, but also enhanced the size exclusion effect of paper, resulting in the novel performance on both SERS detection and sample pretreatment. A biosensor for Mucin-1 is developed by equipping the Au NPs with aptamer. Combining all these merits, this small, cheap and portable test strip might find wide application in clinical diagnosis and health evaluation.

Enediol-Ligands-Encapsulated Liposomes Enables Sensitive Immunoassay: A Proof-of-Concept for General Liposomes-Based Photoelectrochemical Bioanalysis.

Sensitive photoelectrochemical (PEC) bioanalysis usually relies on enzyme-assisted signal amplification. This work describes the first proof-of-concept study for liposome-based PEC bioanalysis. Specifically, unilamellar liposomes were prepared and then utilized to carry the enediol-ligands and antibodies within their internal cavities and upon their external surfaces, respectively. On the other hand, the 96-well plate was used for accommodating the sandwich immunocomplexing, and then the confined liposomes were directed to release the encapsulated enediol-ligands into an individual well. The subsequent in situ sensitization of the TiO2 nanoparticles (NPs) electrode was then used to transduce the recognition events. This facile strategy allows for sensitive immunoassay without the involvement of laborious electrode fabrication and enzymatic amplification. Importantly, the protocol can be extended as a general PEC method for numerous other targets of interest. We believe this work could offer a new perspective for the rational implementation of various liposome complexes for novel PEC bioanalysis.

Microfluidic PDMS on paper (POP) devices.

In this paper, we propose a generalized concept of microfluidic polydimethylsiloxane (PDMS) on paper (POP) devices, which combines well the merits of paper chips and PDMS chips. First, we optimized the conditions for accurate PDMS spatial patterning on paper, based on screen printing and a high temperature enabled superfast curing technique, which enables PDMS patterning to an accuracy of tens of microns in less than ten seconds. This, in turn, makes it available for seamless, reversible and reliable integration of the resulting paper layer with other PDMS channel structures. The integrated POP devices allow for both porous paper and smooth channels to be spatially defined on the devices, greatly extending the flexibility for designers to be able to construct powerful functional structures. To demonstrate the versatility of this design, a prototype POP device for the colorimetric analysis of liver function markers, serum protein, alkaline phosphatase (ALP) and aspartate aminotransferase (AST), was constructed. On this POP device, quantitative sample loading, mixing and multiplex analysis have all been realized.

Folding-based photoelectrochemical biosensor: binding-induced conformation change of a quantum dot-tagged DNA probe for mercury(II) detection.

Using CdS QD-tagged mercury-specific oligonucleotides, a novel folding-based photoelectrochemical sensor has been successfully fabricated for reagentless and highly sensitive Hg(2+) detection.

Disposable paper-based bipolar electrode for sensitive electrochemiluminescence detection of a cancer biomarker.

A disposable paper-based bipolar electrode (BPE) was reported for the first time for the sensitive electrochemiluminescence detection of a prostate specific antigen (PSA).

A facile light-emitting-diode induced fluorescence detector coupled to an integrated microfluidic device for microchip electrophoresis.

In this paper, a compact and inexpensive light emitting diode induced fluorescence (LED-IF) detector with simplified optical configuration was developed and assembled in an integrated microfluidic device for microscale electrophoresis. The facile detector mainly consisted of an LED, a focusing pinhole, an emission filter and a photodiode, and was encapsulated in the upper layer of an aluminum alloy device with two layers. At the bottom layer, integrated circuit (IC) was assembled to manipulate the voltage for sample injection and separation, LED emission and signal amplifying. A high-power LED with fan-shaped heat sink was used as excitation source. The excitation light was focused by a 1.1mm diameter pinhole fabricated in a thin piece of silver foil, and the obtained sensitivity was about 3 times as high as that using electrode plate. Other important parameters including LED driven current, fluorescence collection angle and detection distance have also been investigated. Under optimal conditions, considerable high-response of 0.09 fmol and 0.18 fmol mass detection limits at 0.37 nL injection volume for sodium fluorescein (SF) and FITC was achieved, respectively. This device has been successfully employed to separate penicillamine (PA) enantiomers. Due to such significant features as low-cost, integration, miniaturization, and ease of commercialization, the presented microfluidic device may hold great promise for clinical diagnostics and bioanalytical applications.