Search

The commercialized electrochemiluminescence (ECL) immunoassay is carried out by holding luminophore Ru(bpy) 3 2+ at a given potential. Designing an electrochemiluminophore with a narrow triggering potential window is strongly anticipated to decrease the electrochemical cross-talk and improve the flux of the commercialized ECL immunoassay in a potential-resolved way. Herein, L-penicillamine-capped silver nanoclusters (LPA-AgNCs) are facilely synthesized and utilized as tags to perform the ECL immunoassay with a sole and narrow triggering potential window of 0.24 V by employing hydrazine (N 2 H 4 ) as a coreactant. The maximum ECL emission of the LPA-AgNCs/N 2 H 4 system is located ca. +1.27 V. Upon immobilizing LPA-AgNCs onto the electrode surface via forming a sandwich immunocomplex, the ECL of LPA-AgNCs/N 2 H 4 can be utilized to sensitively and selectively determine human carcinoembryonic antigen from 0.5 to 1000 pg/mL with a low limit of detection of 0.1 pg/mL (S/N = 3). This work might open a way to screen electrochemiluminophores for the multiple ECL immunoassay in a potential-resolved way.

Multiplexed gene assay for simultaneously detecting the multi-targets of nucleic acids is strongly anticipated for the accurate diseases diagnosis and prediction, and all commercial available gene assays for IVD are a kind of single-target assay. Herein, a dual-potential encoded and coreactant-free electrochemiluminescence (ECL) strategy is proposed for the multiplexed gene assay, which can be conveniently carried out by directly oxidizing the same luminescent tag of dual-stabilizers-capped CdTe nanocrystals (NCs). The CdTe NCs linked with sulfhydryl-RNA via Cd-S bond merely exhibits one ECL process around 0.32 V with a narrow triggering-potential-window of 0.35 V, while CdTe NCs linked with amino-RNA via amide linkage solely gives off one ECL process around 0.82 V with a narrow triggering-potential-window of 0.30 V. Multiplexing ECL of both sulfhydryl-RNA-functionalized CdTe NCs and amino-RNA-functionalized CdTe NCs can be utilized to simultaneously detect the open reading frame 1ab (ORF1ab) and the nucleoprotein (N) genes without crosstalk, in which ECL of sulfhydryl-RNA-functionalized CdTe NCs can dynamically determine ORF1ab from 200 aM to 10 fM with a limit of detection (LOD) of 100 aM, while ECL of amino-RNA-functionalized CdTe NCs can linearly detect N gene from 5 fM to 1 pM with a LOD of 2 fM. Post-engineering CdTe NCs with RNA in a labeling-bond engineering way would provide a potential-selective and encoded ECL strategy for multiplexed gene assay with one luminophore., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

5-carboxycytosine (5caC) plays a critical role as an intermediate form in DNA methylation and demethylation processes. Its distribution and quantity significantly influence the dynamic equilibrium of these processes, thereby impacting the normal physiological activities of organisms. However, the analysis of 5caC presents a significant challenge due to its low abundance in the genome, making it almost undetectable in most tissues. In response to this challenge, we propose a selective method for 5caC detection using differential pulse voltammetry (DPV) at glassy carbon electrode (GCE), hinging on probe labeling. The probe molecule Biotin LC-Hydrazide was introduced into the target base and the labeled DNA was immobilized onto the electrode surface with the help of T4 polynucleotide kinase (T4 PNK). Leveraging the precise and efficient recognition of streptavidin and biotin, streptavidin-horseradish peroxidase (SA-HRP) on the surface of the electrode catalyzed a redox reaction involving hydroquinone and hydrogen peroxide, resulting in an amplified current signal. This procedure allowed us to quantitatively detect 5caC based on variations in current signals. This method demonstrated good linearity ranging from 0.01 to 100 nM with a detection limit as low as 7.9 pM. We have successfully applied it to evaluate the 5caC levels in complex biological samples. The probe labeling contributes to a high selectivity for 5caC detection, while the sulfhydryl modification via T4 PNK efficiently circumvents the limitation of specific sequences. Encouragingly, no reports have been made about electrochemical methods for detecting 5caC in DNA, suggesting that our method offers a promising alternative for 5caC detection in clinical samples., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In this work, a potential-resolved electrochemiluminescence (ECL) multiplex immunoassay (MIA) was developed using zirconium-based metal-organic framework (MOF) nanoparticles with intense self-ECL as an anodic ECL tag and CdTe nanocrystals (NCs) as a cathodic ECL tag. ECL luminophore 5,5'-(anthracene-9,10-diyl)diisophthalic acid (H 4 ADIP) and coreactant hexamethylenetetramine (HMT) bound to zirconium nodes in the MOF, giving Zr-ADIP-HMT nanoparticles. Benefiting from the intrareticular charge transfer (ICT) between the oxidized ligands of H 4 ADIP and HMT via hydrogen bonds, the intense self-ECL from Zr-ADIP-HMT was applied to the potential-resolved ECL MIA without an exogenous anodic coreactant, which can eliminate detrimental effects of multiplex coreactants and anodic ECL emission from CdTe NCs. The ICT within Zr-ADIP-HMT nanoparticles could shorten the electron transport path and reduce the complexity of radical intermediate transport. The ECL intensity from Zr-ADIP-HMT was 18.6-fold that from the mixture of H 4 ADIP and HMT. In potential-resolved ECL MIA, two lung cancer biomarkers, carcinoembryonic antigen and neuron-specific enolase, were adopted as model analytes, with detection limits of 18 and 5.3 fg·mL -1 , respectively. The dual-ligand Zr-ADIP-HMT nanoparticles provide a proof of concept using ICT-based self-ECL luminophores for potential-resolved ECL MIAs with isolated coreactants.

Coreactant-free electrochemiluminescence (ECL) is promising for removing the exogenous effects of coreactant and simplify the operation procedures and setups of commercialized ECL bioassays. Herein, an electrosterically involved strategy for achieving a low-triggering-potential (+0.21 V vs Ag/AgCl) and coreactant-free ECL from dual-stabilizer-capped CdTe nanocrystals (NCs) is proposed with mercaptopropionic acid (MPA) and hexametaphosphate (HMP) as the capping agents of luminophores. Upon employing the CdTe NCs as the ECL tag for the immunoassay, all the tags in the bioconjugates of the CdTe NCs and the secondary antibody (Ab 2 |CdTe) as well as in the final achieved sandwich-type immunocomplexes can exhibit efficient coreactant-free ECL with an electrosterically involved triggering potential nature. The bioconjugates of Ab 2 |CdTe with Ab 2 no more than 30 kDa, such as the thyroid stimulating hormone (30 kDa) and the recombinant pro-gastrin releasing peptide (ProGRP, 14 kDa), merely exhibit coreactant-free ECL around +0.24 V, while bioconjugates of Ab 2 |CdTe with an Ab 2 beyond 30 kDa only give off coreactant-free ECL around +0.82 V. Due to the further enhanced electrosteric effect in sandwich-type immunocomplexes, only the ECL immunosensor with ProGRP as the target can give off coreactant-free ECL around +0.24 V. The electrosterically involved and coreactant-free ECL of CdTe NCs is consequently utilized to sensitively and selectively determine the molecular protein ProGRP, which demonstrates a wide linearity range from 0.1 to 2000 pg/mL and a low limit of detection at 0.05 pg/mL (S/N = 3). This low-triggering-potential and coreactant-free combined ECL platform indicates that engineering the surface of CdTe NCs with a protein can improve the performance of ECL tags in a protein-weight-involved electrosterical way.

Sensitively determining trace nucleic acid is of great significance for pathogen identification. Herein, a dynamic DNA nanosystem-integrated ratiometric electrochemical biosensor was proposed to determine human immunodeficiency virus-associated DNA fragment (HIV-DNA) with high sensitivity and selectivity. The dynamic DNA nanosystem was composed of a target recycling unit and a multipedal DNA walker unit. Both of them could be driven by a toehold-mediated strand displacement reaction, enabling an enzyme-free and isothermal amplification strategy for nucleic acid determination. The target recycling unit could selectively recognize HIV-DNA and activate the multipedal DNA walker unit to roll on the electrode surface, which would lead to bidirectional signal variation for ratiometric readout with cascade signal amplification. Benefiting from the synergistic effect of the dynamic DNA nanosystem and the ratiometric output mode, the ultrasensitive detection of HIV-DNA was achieved in a wide linear range of 6 orders of magnitude with a limit of detection of 36.71 aM. The actual usability of the proposed sensor was also verified in complex biological samples with acceptable performance. This dynamic DNA nanosystem-integrated ratiometric sensing strategy might be promising in the development of reliable point-of-care diagnostic devices for highly sensitive and selective pathogen identification.

The investigation on electrochemiluminescence (ECL) multiplexing bioassays mainly focuses on simultaneously detecting either proteins or nucleic acids. To overcome the limitation of a short waveband for spectrum-resolved ECL multiplexing bioassays, herein, a highly monochromatic (FWHM <40 nm) and bandgap-engineered ECL luminophore, that is, mercaptopropionic acid-capped and Zn 2+ -mediated aggregation-induced emission (AIE) assembly of Au nanocrystals (NCs) (Zn 2+ -AIE-AuNCs), of strong emission and the maximum emission wavelength at 485 nm is developed. The highly monochromatic and bandgap-engineered ECL (485 nm) of Zn 2+ -AIE-AuNCs can multiplex with the single-waveband and surface-defect-involved ECL (775 nm) of dual-stabilizer-capped CuInS 2 @ZnS NCs (CIS@ZnS-NCs), enabling a spectrum-resolved ECL multiplexing strategy with different NCs luminophores of a similar particle size as tags. This ECL multiplexing strategy can be utilized to simultaneously detect antigen and DNA probe together without any additional signal amplification procedure and obvious spectroscopic cross-talk, in which the highly monochromatic ECL from Zn 2+ -AIE-AuNCs is utilized to dynamically determine human carcinoembryonic antigen from 1 pg/mL to 50 ng/mL with a limit of detection (LOD) of 0.3 pg/mL, while the single-waveband ECL from CIS@ZnS-NCs is employed to linearly detect wild-type p53 from 1 pM to 50 nM with a LOD of 0.5 pM. The ECL immunoassay of the proposed strategy is free from the interference of the synchronously conducted DNA probe assay and vice versa, which would open an avenue to couple the immunoassay and DNA probe assay together for clinical colon and breast cancer identification.

Single-color electrochemiluminescence (ECL) of nanoparticles is normally achieved in a bandgap engineered route via passivating the nanoparticle surface. Herein, when linear mercaptoalkanoic acids are employed as the thiol-capping agent of unary Au nanoclusters (NCs), a single-stabilizer-capped strategy is proposed to achieve surface defect-involved and single-color ECL from the AuNCs with hydrazine (N 2 H 4 ) as the coreactant. The carbon skeleton of the linear mercaptoalkanoic acids exhibits important effects on the ECL of the AuNCs, and efficient oxidative-reductive ECL is achieved with 8-mercaptooctanoic acid (MOA), 11-mercaptoundecanoic acid (MUA), and 12-mercaptododecanoic acid (MDA) capped AuNCs, respectively. The ECL of these AuNCs not only exhibits similar ECL intensity-potential profiles with the same maximum emission potential of ∼1.20 V (vs Ag/AgCl), but also demonstrates almost identical spectral ECL profiles of the same maximum emission wavelength around 713 nm as well as the same fwhm of 64 nm. The ECL of AuNCs/N 2 H 4 is obviously red-shifted to the photoluminescence of AuNCs, which not only provides unambiguous evidence that bandgap-engineered ECL of these AuNCs is quenched but also manifests that the capping agent of linear mercaptoalkanoic acid is promising for the achievement of surface defect-involved and single-color ECL from AuNCs. The MUA capped AuNCs can be utilized as an ECL tag for a sensitive and selective immunoassay, which exhibits a broad linear range from 0.5 mU/mL to 1 U/mL with a low limit of detection of 0.1 mU/mL (S/N = 3) with CA125 as the model analyte. This work provides a promising alternative to the traditional surface-passivating strategy for the achievement of single-color ECL from nanoparticle luminophores.

The electrochemiluminescence (ECL) bioassay is prominently carried out with the involvement of the coreactant. To remove the detrimental effects of the coreactant on the ECL of luminophores, herein, a promising ECL immunoassay strategy with biocompatible nanoparticles as the luminophore is proposed, which involves directly and electrochemically oxidizing the luminophore methionine-capped Au (Met@Au) nanocrystals (NCs) without the participation of any coreactant. Met@Au NCs are a kind of n-type nanoparticles, and they can be electrochemically injected with valence band (VB) holes around +0.80 and +1.10 V (vs Ag/AgCl). The electrochemically injected exogenous VB hole can recombine with the endogenous conduction band electron of Met@Au NCs and eventually bring out two coreactant-free and near-infrared ECL processes around 0.80 V (ECL-1) and 1.10 V (ECL-2). The intensity of coreactant-free ECL is primarily determined by the electrochemical oxidation-induced hole-injection process. ECL-2 is considerably stronger than ECL-1 and can be exploited for determining the carcinoembryonic antigen (CEA) in a sandwich immunoassay procedure with a linear range from 0.1 to 50 pg/mL as well as a limit of detection of 0.03 pg/mL (S/N = 3).

The accurate and sensitive detection of survivin mRNA is of great significance for cancer diagnosis and treatment. However, limited by the low-abundance mRNA in live cells, most strategies of survivin mRNA detection that were one-to-one signal-triggered model (one target triggered one signal) were inapplicable in practice. Here, we reported a binding-induced DNAzyme motor triggered by the survivin mRNA, which was a one-to-more signal-triggered model (one target triggered more signals), amplifying the detection signal and enhancing the sensitivity. The nanomotor is constructed by assembling several DNAzyme motor strands silenced by the blocker strands, and dozens of FAM-labeled substrate strands on a single gold nanoparticle (AuNP), forming three-dimensional DNA tracks. Through building the survivin mRNA bridge between the blocker and the DNAzyme motor strand, the binding-induced DNA nanomotor could be triggered by survivin mRNA. The operation of the DNAzyme motor was self-powered. And each walking step of the DNAzyme motor was fueled by DNAzyme-catalyzed substrate cleavage, along with the cleavage of the fluorescent molecule, resulting in autonomous and progressive walking along the AuNP-based tracks, and the fluorescence increase. The DNAzyme motor exhibited excellent sensitivity and remarkable specificity for survivin mRNA, providing the potential for cell image., (© 2022. Springer-Verlag GmbH Germany, part of Springer Nature.)

The development of a rapid and sensitive detection platform for DNA and DNA methylation in complex biological environments has attracted considerable attention. Herein, we describe a detection platform for p16 and p16 methylation in buffer and serum based on a single polymeric fluorescent microfiber waveguide with sandwich-structured hybridization designs. The target p16 could be captured by oligonucleotides conjugated on the surface of polymeric microfibers and oligonucleotides conjugated with gold nanoparticles, resulting in quenching the out-coupled tip emission of the microfiber waveguide. Then the restriction digestion enzyme HpaII was applied to specifically recognize the unmethylated 5'-CCGG-3' site and cut the formed sandwich structure. The gold nanoparticles could be removed from the surface of chitosan fiber so that the out-coupled tip emission of the polymeric fluorescent microfiber would be partially recovered. It is noteworthy that the proposed polymeric microfiber waveguide platform exhibited selective and sensitive detection of p16 with a low limit of 2 pM and excellent analytical performance of methylation as low as 5% difference. This strategy avoids the use of traditional PCR-based amplification and tedious operative processes, and we envisage that this technique could be extended to various DNA methylation analyses, which is meaningful for early clinical diagnosis of diseases.

Pancreatic cancer (PC), which has a high fatality rate, is a kind of cancer with poor diagnosis and poor prognosis. Development of selective and sensitive detection platform to diagnose and prognostic of PC has attracted considerable attention. The miRNA-198 has been reported a potential prognostic and early diagnostic marker signature of PC. Herein, we report a novel sensitive detection of miRNA-198 in buffer and serum based on one dimensional chitosan/fluorescein isothiocyanate (CS/FITC) fluorescent microfiber waveguide system combined with the catalytic hairpin assembly amplification strategy. By combination with condensing enrichment effect, the proposed detection platform exhibited high specificity and sensitivity to miRNA-198 target, giving a detection limit as low as 2 fM. More importantly, the proposed detection platform can be applied directly to distinguish the expression of miRNA-198 in clinical serum, affording the ability to distinguish pancreatic cancer patients from those of healthy human beings, and quantify the expression variation of miRNA-198 for the pancreatic cancer patients before and after resection, which may pave the way to develop novel clinical diagnostic equipment for cancer diagnosis and therapeutic evaluation., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The intensity of electrochemiluminescence (ECL) usually changes rapidly with the progress of the electrochemical process, making it difficult to determine the ECL spectrum with a conventional photomultiplier in a wavelength scan model. Herein, a band-pass filter (BPF)-involved modulating strategy is proposed to upgrade a conventional ECL analyzer to a highly sensitive ECL spectrometer without changing its hardware. The ECL spectrum can be figured out by rapidly and/or continuously modulating a part of the ECL intensity-time curve with a BPF array of different central wavelengths as well as correcting the ECL intensity at different measurement times by a univariate cubic polynomial model. This strategy not only can determine the spectrum of ultra-weak emission with high sensitivity via merely modulating the emission within a short period, including the weak self-ECL from either Ru(bpy) 3 2+ or tripropylamine (TPA), but also can demonstrate the interaction between the co-existing emitters. It is shown that the ECL from both Ru(bpy) 3 2+ and TPA of the Ru(bpy) 3 2+ /TPA system can be mutually promoted in electrochemical potential and in a concentration-dependent way. The self-ECL of TPA at the potential of 1.24 V can be enhanced from 4.9- to 51-fold with the Ru(bpy) 3 2+ concentration increasing from 0.01 to 0.8 μM. In the presence of 0.04 μM Ru(bpy) 3 2+ , the self-ECL of TPA is enhanced by 94- and 10.2-fold at the potential of 1.01 and 1.76 V, respectively. The portable inexpensive BPF turntable device is also useful in spectrum-resolved multi-analyte determination and ratiometric ECL biosensors.

Electrochemiluminescence (ECL) is conventionally generated in either an annihilation or a coreactant route, and the overwhelming majority of ECL research is conducted in the coreactant route via oxidizing or reducing the coexisting coreactant and luminophore. The coreacant-free ECL generated via merely oxidizing the luminophore would break through the ceiling of coreactant ECL via excluding the detrimental effects of exogenous coreactant and dissolved oxygen. Herein, by exploiting the rich-electron nature of n-type nanocrystals (NCs), coreacant-free ECL is achieved via merely oxidizing 3-mercaptopropionic acid (MPA) and mercaptosuccinic acid (MSA) capped InP/ZnS NCs, i.e., InP/ZnS MPA-MSA . The electron-rich InP/ZnS MPA-MSA can be electrochemically injected with holes via two oxidative processes at around +0.75 and +1.37 V (vs Ag/AgCl), respectively, and the exogenous hole can directly combine the conduction band (CB) electron of InP/ZnS MPA-MSA , resulting in two coreactant-free ECL processes without employing any exogenous coreactant. The deprotonation process for the carboxyl group of the capping agents can provide a negatively charged surface to InP/ZnS MPA-MSA and enhance the coreactant-free ECL. The hole-injecting process at +1.37 is much stronger than that at +0.75 V and eventually enables an ∼2000-fold enhanced ECL at +1.37 V than that at +0.75 V. The ECL at +1.37 V can be utilized for coreactant-free ECL immunoassay with prostate-specific antigen (PSA) as analyte, which exhibits an acceptable linear response from 5 pg·mL -1 to 1 ng·mL -1 with a limit of detection of 0.3 pg·mL -1 . The coreactant-free ECL route would provide an alternative to both annihilation and coreactant routes, simplify the ECL assay procedure and deepening the ECL mechanism investigations.

Near-infrared electrochemiluminescence (NIR ECL) luminophores are strongly anticipated in ECL bioimaging and spectrum-resolved multiplexing assays. Herein, bovine serum albumin-stabilized Ag nanoclusters (BSA-Ag NCs) are demonstrated promising NIR ECL performance, exhibiting strong anodic ECL spectrum peak at 904 nm in aqueous medium. The ECL intensity of BSA-Ag NCs-triethanolamine system was enhanced 3.2 times by adding TiO 2 nanoparticles as co-reactant accelerator. In a spectrum-resolved triplex-color ECL multiplexing immunoassay, CdSe NCs, CdTe NCs and BSA-Ag NCs were used as the ECL tags, carbohydrate antigen 125 (CA125), carbohydrate antigen 19-9 (CA19-9) and cardiac troponin I (cTnI) were chosen as model analytes. The ECL peaks of three antigen-NCs pairs were simultaneously measured via one ECL potential scan. The composite of carbon nanotubes-TiO 2 nanoparticles-chitosan was served as the conductivity and co-reactant accelerators, enhancing the ECL intensity by 16 folds. With the integral intensity over the ECL peaks as the analytical signal to improve further the signal-to-noise ratio, the limits of detection were 0.035 mU mL -1 for CA125, 0.087 mU mL -1 for CA19-9, and 0.016 pg mL -1 for cTnI, respectively., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Screening toxic-element-free and biocompatible electrochemiluminophores was crucial for electrochemiluminescence (ECL) evolution. Herein, l-glutathione (GSH)-capped Ag-Ga-In-S (AGIS) nanocrystals (NCs) were prepared by doping Ag-In-S (AIS) NCs in a doping-in-growth way and utilized as a model for both ECL modulating and developing multinary NC-based electrochemiluminophores with enhanced ECL performance than trinary NCs. AGIS NCs not only primarily preserved the morphology, size, phase structure, and water monodisperse characteristics of AIS NCs with broadened band gap but also demonstrated obviously enhanced oxidative-reduction ECL than AIS NCs. Importantly, ECL of AGIS NCs was located at the near-infrared region with a maximum emission wavelength of 744 nm and could be utilized for an ECL immunoassay with human prostate-specific antigen (PSA) as a model, which exhibited a linearity range from 0.05 pg/mL to 1.0 ng/mL and a low limit of detection of 0.01 pg/mL (S/N = 3). This work provided a promising alternative to the traditional binary NCs for developing toxic-element-free and biocompatible electrochemiluminophores with efficient near-infrared ECL.

The design and development of novel electrochemiluminescence (ECL) systems with near-infrared (NIR) emission beyond 800 nm are promising for ECL evolution, especially for improving the throughput of the spectrum-resolved multiplexing ECL assay and biological imaging. Herein a biocompatible and environmentally friendly luminophore, that is, the methionine-stabilized Au nanoclusters (Met-Au NCs), are proposed to achieve efficient aqueous ECL of ∼835 nm with triethanolamine as coreactant. The Met-Au NCs not only demonstrate a 75 times enhanced ECL compared with the traditional Au NCs with bovine serum albumin as a capping agent but also can be employed as ECL tags to label proteins with a methionine linker and enable a highly sensitive NIR ECL bioassay. A sandwich-type NIR ECL immunosensor is constructed with the Met-Au NCs as tags and α-fetoprotein (AFP) as a model analyte and exhibits a wide linearity range from 3 fg·mL -1 to 0.1 ng·mL -1 with a limit of detection of 1 fg mL -1 (S/N = 3) as well as desired selectivity.

Catalytic hairpin assembly (CHA) is a typical enzyme-free amplification strategy, in which the target can catalyze two hairpin probes to form a duplex and yield multiple outputs signal. However, the non-specific hybridization of two hairpin probes in CHA circuit usually occurred even in the absence of target, causing significant background leakage and impeding its practical applications in trace miRNA analysis. Herein, we proposed a novel heterogeneous CHA (hetero-CHA) design integrating with PDA microtube waveguide system, offering the advantages to enhance the target signal, but suppress the background leakage simultaneously. In hetero-CHA strategy, single-stranded targets are enriched nearby the surface of PDA microtube, facilitating the target-triggered CHA amplification and strand displacement reactions. In contrast, double-stranded DNA complexes formed by uncatalyzed hybridizations are isolated from PDA microtube, impeding the leakage signal. By combination with condensing enrichment effect, the proposed hetero-CHA probe exhibited high selectivity and sensitivity to miRNA target, giving a detection limit as low as 3.3 fM. More importantly, the proposed hetero-CHA probe can be applied directly to distinguish the expression of miRNA-21 in clinical serum of cancer patients (including lung, breast and pancreatic) from those of healthy human beings, favoring the cancer diagnosis and therapeutic evaluation., (Copyright © 2019 Elsevier B.V. All rights reserved.)

MicroRNAs (miRNAs) have emerged as novel biomarkers for human early-phase cancer diagnosis and disease prevention recently. Herein, we reported a novel miRNA-215 targeting biosensor, which was based on single polydiacetylene (PDA) microtube waveguide system integrated with sandwich-type hybridization design and condensing enrichment effect. The target miRNA could be captured by oligonucleotides conjugated on the surface of PDA microtube and Au nanorod (AuNR) respectively, resulting in the out-coupled fluorescence of PDA microtube quenching. In this strategy, the formation of a sandwich structure, as a result of co-hybridization of the target miRNA, enabled simplified preparation process, enhanced reaction efficiency, and increased recyclability and stability of the platform. Based on condensing enrichment effect, the co-hybridization reaction could be enriched on the surface of microtube and the proposed platform could easily achieve highly sensitive detection of miRNA-215 in one step. Remarkably, this platform could be directly applied to discriminate the miRNA-215 expression levels in clinical gastric cancerous, paracancerous and normal tissues samples. This assay offers a simple and convenient method for miRNA quantification in clinical samples, even with the potential for invasive, portable equipment for early clinical diagnosis of diseases., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A dual-wavebands-resolved electrochemiluminescence (ECL) multiplexing immunoassay (MIA) was developed for simultaneously detecting alpha fetoprotein antigen (AFP) in greenish waveband with CdSe550 (λ max = 550 nm) nanocrystals (NCs) and carbohydrate antigen 125 (CA125) in near-infrared waveband with CdTe790 (λ max = 790 nm) NCs via one-pot ECL reaction, in which dichroic mirror works as a key part to reflect ECL from CdSe550 to one photomultiplier-tube (PMT) and transmit ECL from CdTe790 to the other PMT for dual-wavebands-resolved assay. The proposed ECL-MIA strategy was capable of simultaneously determining AFP with linearly response from 5 pg/mL to 5 ng/mL and limit of detection at 1 pg/mL, and CA125 with linearly response from 5 mU/mL to 1 U/mL and limit of detection at 1 mU/mL, with desired specificity and without obvious energy-transfer between ECL tags. The dichroic mirror assistant ECL setup is easy-to-assemble and convenient for the popularization of color-resolved multiplexing ECL assay., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In organisms 5-formyluracil (5fU), which is known as a vital natural nucleobase, is widely present. Despite the recent development of sensor designs for organic fluorescent molecules for selective targeting applications, biocompatible and easily operated probe designs that are based on natural nucleobase modifications have rarely been reported. Here, we introduce the idea of 5fU as a multifunctional building block to facilitate the design and synthetic development of biosensors. The azide group was derived from the sugar of a nucleoside, which can be further used in the selective binding of cells or organelles through click chemistry with alkynyl-modified targeting groups. The aldehyde group of 5fU can react with different chemicals to generate environmentally sensitive nucleobases that have obvious characteristics, which precious reactants cannot achieve for selective fluorogenic switch-on detection of a specific target. We first synthesized 5fU analogues that had aggregation-induced emission properties, and then we used triphenylphosphonium as a mitochondria-targeting group to selectively image mitochondria in cancer cells and mouse embryonic stem cells. Additionally, the reagents exhibit a high selectivity for reaction with 5fU, which means that the method can also be used for the detection of 5fU. Combining the two characteristics, the idea of 5fU as a multifunctional building block in biosensor designs may potentially be applicable in 5fU site-specific microenvironment detection in future research., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The electrochemical-dependent and unstable intensity of electrochemiluminescence (ECL) makes it difficult to identify ECL in a waveband-resolved way on photomultiplier tube (PMT)-based traditional ECL analyzers. Herein, a dual-color ECL strategy is proposed by transferring ECL to two PMTs in a waveband-resolved way via dichroic mirror, simultaneously detecting wild-type p53 (WTp53) in near-infrared wavebands with CdTe (λ max = 782 nm) nanocrystals as tag and mutant p53 (MUp53) in eye-visible wavebands with CdSe (λ max = 554 nm) nanocrystals as tag. The two targets can be color-selectively determined from 10 fM to 100 pM with a limit of detection at 5 fM for MUp53 and from 50 fM to 100 pM with a limit of detection at 10 fM for WTp53, respectively. The dichroic mirror-involved ECL setup is easy to assemble for popularization, which would not only eventually enable PMT-based multiple-color ECL analysis but also make it is possible to directly determine the changed level of tumor suppressors for cancer diagnosis and therapeutic evaluation via one-pot ECL assay.

Copper indium sulfide (CuInS 2 , CIS) nanocrystals (NCs) are a promising solution to the toxic issue of Cd- and Pb-based NCs. Herein, electrochemiluminescence (ECL) of CIS NCs in aqueous medium is investigated for the first time with l-glutathione and sodium citrate-stabilized water-soluble CIS/ZnS NCs as model. The CIS/ZnS NCs can be oxidized to hole-injected states via electrochemically injecting holes into valence band at 0.55 and 0.94 V (vs Ag/AgCl), respectively. The hole-injected state around 0.94 V can bring out efficient oxidative-reduction ECL with a similar color to Ru(bpy) 3 2+ in the presence of tri- n-propylamine (TPrA) and enable CIS/ZnS NCs promising ECL tags with l-glutathione as linker for labeling. The ECL of CIS/ZnS NCs/TPrA can be utilized to determine vascular endothelial growth factor (VEGF) from 0.10 to 1000 pM with the limit of detection at 0.050 pM (S/N = 3). Although the hole-injected state around 0.55 V is generated ahead of oxidation of TPrA and fails to bring out coreactant ECL, annihilation ECL proves that both hole-injected states generated, at 0.55 and 0.94 V, can be involved in electrochemical redox-induced radiative charge transfer by directly stepping CIS/ZnS NCs from electron-injecting potential to hole-injecting potential. CIS/ZnS NCs are promising nontoxic electrochemiluminophores with lowered ECL triggering potential around 0.55 V for less electrochemical interference upon the development of coreactant.

Development of rapid, highly selective and sensitive miRNA detection in a complex biological environment has attracted considerable attention. Herein, we describe a novel two step method to construct gold-nanorod functionalized polydiacetylene (PDA) microtube for miRNA detection. In PDA microtube, with a one-dimensional (1D) waveguide nature, the excitation position and emission out-coupling position are far apart, thus helpful in reducing contribution of auto-fluorescence from biological sample. The use of specially designed toehold-mediated strand displacement reaction enables the reliable and selective discrimination of miRNA sequences with high sequence homology. Based on the condensing enrichment effect, the detection limit of the proposed PDA microtube system is as low as 0.01nM, and it can be applied directly to detect disease-specific miRNA targets in human serum. This PDA microtube waveguide system can be further integrated into the chip for the potential applications in minimally invasive, portable clinical diagnostic equipment., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The development of electrochemiluminescence (ECL) emitters over a broad spectrum of wavelengths is anticipated for the multiplexed ECL sensing and diagnostic application. Herein, a facile dual-stabilizers-capped strategy was developed for synthesizing a series of water-soluble CdSe nanocrystals (NCs) with strong, bandgap engineered and monochromatic ECL emissions in greenish region. The linkage of surface cadmium atoms to the dual stabilizers, mercaptopropionic acid and sodium hexametaphosphate, not only can effectively remove the nonradiative surface state and deep surface trap of CdSe NCs for improved ECL efficiency and monochromaticity, but is also favorable for the electrochemical involved electron and hole injection processes for higher ECL intensity. ECL spectra of dual-stabilizers-capped CdSe NCs are narrow and much close to corresponding photoluminescence spectra, which indicates a series of bandgap engineered and monochromatic ECL emitters. The ECL signal of dual-stabilizers-capped CdSe NCs also shows acceptable accuracy and precision for the detection of dopamine concentration in the practical drug (dopamine hydrochloride injection)., (Copyright © 2013 Elsevier B.V. All rights reserved.)

In this paper, we reported an ultrasensitive ECL spectrometry for determination of DNA using magnetic streptavidin-coated nanobeads MNBs (SA-MNBs) as the carrier of Ru(bpy)(3)(2+)-NHS, where bpy=2,2'-bipyridyl and NHS=N-hydroxysuccinimide ester, to amplify signal. The SA-MNBs were conjugated to the hybrids consisting of capture DNA, target DNA (t-DNA) and probe DNA immobilized on a substrate, followed by releasing the SA-MNBs and binding a huge number of Ru(bpy)(3)(2+)-NHS to the SA-MNBs. The SA-MNBs with Ru(bpy)(3)(2+)-NHS were immobilized on an Au film electrode by means of a magnet. In the presence of tri-n-propylamine, the ECL spectrum of the Ru(bpy)(3)(2+)-NHS at 1.35 V was acquired by using an optical multi-channel analyzer. The maximum emission intensity on the ECL spectrum was used to quantify DNA. Using this method, not only the limit of detection for DNA determination was as low as 1.2 × 10(-15)mol/L, but also the ECL spectrum of Ru(bpy)(3)(2+)-NHS on the surface of the SA-MNBs was obtained. The ultrasensitive ECL spectrometry could be used to measure gene expression level in cells., (Copyright © 2011 Elsevier B.V. All rights reserved.)

An ultrasensitive electrochemical method for determination of DNA is developed based on counting of single magnetic nanobeads (MNBs) corresponding to single DNA sequences combined with a double amplification (DNA amplification and enzyme amplification). In this method, target DNA (t-DNA) is captured on a streptavidin-coated substrate via biotinylated capture DNA. Then, MNBs functionalized with first-probe DNAs (p1-DNA-MNBs) are conjugated to t-DNA sequences with a ratio of 1:1. Subsequently, the p1-DNA-MNBs are released from the substrate via dehybridization. The released p1-DNA-MNBs are labeled with alkaline phosphatase (AP) using biotinylated second-probe DNAs (p2-DNAs) and streptavidin-AP conjugates. The resultant AP-p2-DNA-p1-DNA-MNBs with enzyme substrate disodium phenyl phosphate (DPP) are continuously introduced through a capillary as the microsampler and microreactor at 40 degrees C. AP on the AP-p2-DNA-p1-DNA-MNBs converts a huge number of DPP into its product phenol, and phenol zones are produced around each moving AP-p2-DNA-p1-DNA-MNB. The phenol zones are continuously delivered to the capillary outlet and detected by a carbon fiber disk bundle electrode at 1.05 V. An elution curve with peaks is obtained. Each peak is corresponding to a phenol zone relative to single t-DNA sequence. The peaks on the elution curve are counted for quantification. The number of the peaks is proportional to the concentration of t-DNA in a range of 5.0 x 10(-16) to 1.0 x 10(-13) mol/L.

DNA is the potential target of numerous drugs utilized widely in clinical cancer therapy. Here we employed bleomycin A5, with its deactivated form as contrast, to investigate the interaction between small pharmaceutical and DNA. Electrophoresis mobility shift assay (EMSA) which is a common technique used in studying specific interactions between DNA and proteins is applied in visualizing the binding of bleomycin A5 with DNA intuitively. More accurate association equilibrium constant for native and deactivated bleomycin A5 to DNA achieved on biosensor IAsys AUTO+ is 1.25x10(4) and 1.3x10(3) M(-1), respectively. With combination of EMSA and biosensor, a qualitative and quantitative method is described, which can be extended to studying the binding of most small molecules with targeting DNA and serves as a powerful tool in designing and screening for novel drugs.