Potential-selective electrochemiluminescence of AgInS2/ZnS nanocrystals and its immunoassay application.

Potential-selective electrochemiluminescence (ECL) with tunable maximum-emission-potential ranging from 0.95 to 0.30 V is achieved using AgInS2/ZnS nanocrystals, which is promising in the design of multiplexed bioassay on commercialized ECL setups. The model system AgInS2/ZnS/N2H4 exhibits efficient ECL around 0.30 V and can be exploited for sensitive immunoassays with less electrochemical interference and crosstalk.

Low-Triggering-Potential and Narrow-Potential-Window Electrochemiluminescence of Silver Nanoclusters for Gene Assay.

A low-triggering potential and a narrow-potential window are anticipated to decrease the electrochemical interference and cross talk of electrochemiluminescence (ECL). Herein, by exploiting the low oxidative potential (0.82 V vs Ag/AgCl) of dihydrolipoic acid-capped sliver nanoclusters (DHLA-AgNCs), a coreactant ECL system of DHLA-AgNCs/hydrazine (N2H4) is proposed to achieve efficient and oxidative-reduction ECL with a low-triggering potential of 0.82 V (vs Ag/AgCl) and a narrow-potential window of 0.22 V. The low-triggering-potential and narrow-potential-window nature of ECL can be primarily preserved upon labeling DHLA-AgNCs to probe DNA and immobilizing DHLA-AgNCs onto the Au surface via sandwiched hybridization, which eventually enables a selective ECL strategy for the gene assay at +0.82 V. This gene assay strategy can sensitively determine the gene of human papillomavirus from 10 to 1000 pM with a low limit of detection of 5 pM (S/N = 3) and would open a way to improve the applied ECL bioassay.

The plant-like protein phosphatase PPKL regulates parasite replication and morphology in Toxoplasma gondii.

BACKGROUND: The protozoan parasite Toxoplasma gondii encodes dozens of phosphatases, among which a plant-like phosphatase absent from mammalian genomes named PPKL, which is involved in regulating brassinosteroid signaling in Arabidopsis, was identified in the genome. Among the Apicomplexa parasites, T. gondii is an important and representative pathogen in humans and animals. PPKL was previously identified to modulate the apical integrity and morphology of the ookinetes and parasite motility and transmission in another important parasite, Plasmodium falciparum. However, the exact function of PPKL in the asexual stages of T. gondii remains unknown. METHODS: The plant auxin-inducible degron (AID) system was applied to dissect the phenotypes of PPKL in T. gondii. We first analyzed the phenotypes of the AID parasites at an induction time of 24 h, by staining of different organelles using their corresponding markers. These analyses were further conducted for the parasites grown in auxin for 6 and 12 h using a quantitative approach and for the type II strain ME49 of AID parasites. To further understand the phenotypes, the potential protein interactions were analyzed using a proximity biotin labeling approach. The essential role of PPKL in parasite replication was revealed. RESULTS: PPKL is localized in the apical region and nucleus and partially distributed in the cytoplasm of the parasite. The phenotyping of PPKL showed its essentiality for parasite replication and morphology. Further dissections demonstrate that PPKL is required for the maturation of daughter parasites in the mother cells, resulting in multiple nuclei in a single parasite. The phenotype of the daughter parasites and parasite morphology were observed in another type of T. gondii strain ME49. The substantial defect in parasite replication and morphology could be rescued by genetic complementation, thus supporting its essential function for PPKL in the formation of parasites. The protein interaction analysis showed the potential interaction of PPKL with diverse proteins, thus explaining the importance of PPKL in the parasite. CONCLUSIONS: PPKL plays an important role in the formation of daughter parasites, revealing its subtle involvement in the proper maturation of the daughter parasites during division. Our detailed analysis also demonstrated that depletion of PPKL resulted in elongated tubulin fibers in the parasites. The important roles in the parasites are potentially attributed to the protein interaction mediated by kelch domains on the protein. Taken together, these findings contribute to our understanding of a key phosphatase involved in parasite replication, suggesting the potential of this phosphatase as a pharmaceutic target.

Silver Nanocluster-Tagged Electrochemiluminescence Immunoassay with a Sole and Narrow Triggering Potential Window.

The commercialized electrochemiluminescence (ECL) immunoassay is carried out by holding luminophore Ru(bpy)32+ 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 (N2H4) as a coreactant. The maximum ECL emission of the LPA-AgNCs/N2H4 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/N2H4 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.

Transcriptomic and metabolomic analyses reveal the essential nature of Rab1B in Toxoplasma gondii.

BACKGROUND: The protozoan parasite Toxoplasma gondii encodes a dozen Rab proteins, which are parts of the small GTPase superfamily and regulate intracellular membrane trafficking. Our previous study showed that depletion of Rab1B caused severe defects regarding parasite growth and morphological structure, yet early defects of endocytic trafficking and vesicle sorting to the rhoptry in T. gondii are not expected to have a strong effect. To understand this discrepancy, we performed an integrated analysis at the level of transcriptomics and metabolomics. METHODS: In the study, tetracycline-inducible TATi/Ty-Rab1B parasite line treated with ATc at three different time points (0, 18 and 24 h) was used. We first observed the morphological changes caused by Rab1B depletion via transmission electron technology. Then, high-throughput transcriptome along with non-targeted metabolomics were performed to analyze the RNA expression and metabolite changes in the Rab1B-depleted parasite. The essential nature of Rab1B in the parasite was revealed by the integrated omics approach. RESULTS: Transmission electron micrographs showed a strong disorganization of endo-membranes in the Rab1B-depleted parasites. Our deep analysis of transcriptome and metabolome identified 2181 and 2374 differentially expressed genes (DEGs) and 30 and 83 differentially expressed metabolites (DEMs) at 18 and 24 h of induction in the tetracycline-inducible parasite line, respectively. These DEGs included key genes associated with crucial organelles that contain the rhoptry, microneme, endoplasmic reticulum and Golgi apparatus. The analysis of qRT-PCR verified some of the key DEGs identified by RNA-Seq, supporting that the key vesicular regulator Rab1B was involved in biogenesis of multiple parasite organelles. Functional enrichment analyses revealed pathways related to central carbon metabolisms and lipid metabolisms, such as the TCA cycle, glycerophospholipid metabolism and fatty acid biosynthesis and elongation. Further correlation analysis of the major DEMs and DEGs supported the role of Rab1B in biogenesis of fatty acids (e.g. myrisoleic acid and oleic acid) (R > 0.95 and P < 0.05), which was consistent with the scavenging role in biotin via the endocytic process. CONCLUSIONS: Rab1B played an important role in parasite growth and morphology, which was supported by the replication assay and transmission electron microscopy observation. Our multi-omics analyses provided detailed insights into the overall impact on the parasite upon depletion of the protein. These analyses reinforced the role of Rab1B in the endocytic process, which has an impact on fatty acid biogenesis and the TCA cycle. Taken together, these findings contribute to our understanding of a key vesicular regulator, Rab1B, on parasite metabolism and morphological formation in T. gondii.

Dual-potential encoded electrochemiluminescence for multiplexed gene assay with one luminophore as tag.

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.

Enhanced Photon Emission of Chemiluminescent Luminophore for Ultra-Fast and Semi-Automatic Immunoassay toward Single Molecule Detection.

Optical single molecule detection is normally achieved via amplifying the total emission of photons of luminophores and is strongly anticipated to extend the commercialized application of chemiluminescence (CL). To overcome the limited CL photons of molecule luminophores, herein, a nanocrystal (NC) luminophore self-amplified strategy is proposed to repetitively excite CL luminophores for amplifying the total CL photons per luminophore, which can be exploited to perform CL immunoassays (CLIAs) toward single molecule detection via employing KMnO4 as the CL triggering agent and the dual-stabilizer-capped CdTe NCs as the CL luminophore. KMnO4 can oxidize the S element from each stabilizer of mercaptopropionic acid (MPA) and release enough energy to excite the CdTe core for flash CL. The substantial MPA around each CdTe core enables every CdTe luminophore to be repetitively excited and give off amplified total CL photons in a self-enhanced way. The CL of CdTe NCs/KMnO4 can release all photons rapidly, and the collection of all these photons can be utilized to determine the model analyte of thyroid-stimulating hormone antigen (TSH) with a limit of detection of 5 ag/mL (S/N = 3), which is corresponding to about 2-4 TSH molecules in a 20 µL sample. The whole immunologic operating process can be terminated within 6 min. This strategy of repetitively breaking the CL reaction involving chemical bonds within one luminophore is promising for semi-automatic as well as fully automatic single molecule detection and extends the commercialized application of CL immunodiagnosis.

Luminophore-Surface-Engineering-Enabled Low-Triggering-Potential and Coreactant-Free Electrochemiluminescence for Protein Determination.

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 (Ab2|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 Ab2|CdTe with Ab2 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 Ab2|CdTe with an Ab2 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.

Surface-Defect-Involved and Eye-Visible Electrochemiluminescence of Unary Copper Nanoclusters for Immunoassay.

A single-stabilizer-capped strategy is proposed for achieving highly efficient and surface-defect-involved electrochemiluminescence (ECL) from unary copper nanoclusters (NCs) via employing l-cysteine (Cys) as a capping agent of luminophore. The Cys-capped CuNCs (Cys-CuNCs) can be electrochemically injected with valence band (VB) holes and exhibit eye-touchable ECL processes around +0.95 and +1.15 V upon employing TPrA as a coreactant. Both accumulated ECL spectra and spooling ECL spectra demonstrated that the two ECL processes are of the same single waveband and spectrally identical to each other with the same maximum emission wavelength of 640 nm. Promisingly, ECL of the Cys-CuNCs/TPrA system is obviously red-shifted for ∼150 nm to PL of Cys-CuNCs, indicating that the bandgap-engineered routes for ECLs of Cys-CuNCs are completely blocked. The oxidative-reduction ECL process of the Cys-CuNCs/TPrA system is a kind of highly efficient, eye-visible, and single-color emission in surface-defect-involved route. The capping agent of Cys can enable the CuNCs/TPrA system with a stronger ECL than other thiol capping agents, so that Cys-CuNCs are utilized as ECL tags for sensitive and selective immunoassays, which exhibit a wide linear response range from 0.05 pg/mL to 0.5 ng/mL and a limit of detection of 0.01 pg/mL (S/N = 3) with carcinoembryonic antigen as the analyte. Moreover, both the luminophore Cys-CuNCs and conjugates Ab2-CuNCs can be safely stored in aqueous media without any protector, which is promising for the evolution and clinic application of metal NC ECL in the surface-defect-involved route.

Valence-State-Engineered Electrochemiluminescence from Au Nanoclusters.

To determine the intrinsic effects of body elements on the electrochemiluminescence (ECL) of metal nanoclusters (NCs), herein, a valence-state engineering strategy is developed to adjust the NCs' ECL with bovine serum albumin (BSA)-stabilized AuNCs as a model, in which engineering the valence state of the Au body element, i.e., Au(0) and Au(I), is performed via successively reducing the precursor AuCl4- to Au(I) and Au(0) with BSA. The obtained BSA-AuNCs/N2H4 system leads to three anodic ECL processes at 0.37 (ECL-1), 0.85 (ECL-2), and 1.45 V (ECL-3). ECL-1 is generated from the BSA-Au(0) section of BSA-AuNCs in a surface-defect-involved route and is much stronger and red-shifted compared to ECL-2 and ECL-3, which are generated from the BSA-Au(I) section of BSA-AuNCs in the band-gap-engineered route. Each of the anodic ECL processes can be selectively generated and/or suppressed via adjusting the Au(I)/Au(0) ratio of BSA-AuNCs, tunable ECL generation route, and triggering potential, and the emission intensity and waveband of metal NCs are conveniently achieved in body-element-involved valence-state engineering.

Interparticle Charge-Transport-Enhanced Electrochemiluminescence of Quantum-Dot Aerogels.

Electrochemiluminescence (ECL) represents a widely explored technique to generate light, in which the emission intensity relies critically on the charge-transfer reactions between electrogenerated radicals. Two types of charge-transfer mechanisms have been postulated for ECL generation, but the manipulation and effective probing of these routes remain a fundamental challenge. Here, we demonstrate the design of quantum dot (QD) aerogels as novel ECL luminophores via a versatile water-induced gelation strategy. The strong electronic coupling between adjacent QDs enables efficient charge transport within the aerogel network, leading to the generation of highly efficient ECL based on the selectively improved interparticle charge-transfer route. This mechanism is further verified by designing CdSe-CdTe mixed QD aerogels, where the two mechanistic routes are clearly decoupled for ECL generation. We anticipate our work will advance the fundamental understanding of ECL and prove useful for designing next-generation QD-based devices.

Spectrum-Resolved Electrochemiluminescence to Multiplex the Immunoassay and DNA Probe Assay.

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 Zn2+-mediated aggregation-induced emission (AIE) assembly of Au nanocrystals (NCs) (Zn2+-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 Zn2+-AIE-AuNCs can multiplex with the single-waveband and surface-defect-involved ECL (775 nm) of dual-stabilizer-capped CuInS2@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 Zn2+-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.

Coreactant-free and Near-Infrared Electrochemiluminescence Immunoassay with n-Type Au Nanocrystals as 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).

Downregulation of the Long Noncoding RNA IALNCR Targeting MAPK8/JNK1 Promotes Apoptosis and Antagonizes Bovine Viral Diarrhea Virus Replication in Host Cells.

Bovine viral diarrhea virus (BVDV) is the causative agent of the bovine viral diarrhea-mucosal disease, which is a leading cause of economic losses in the cattle industry worldwide. To date, many underlying mechanisms involved in BVDV-host interactions remain unclear, especially the functions of long noncoding RNAs (lncRNAs). In our previous study, the lncRNA expression profiles of BVDV-infected Madin-Darby bovine kidney (MDBK) cells were obtained by RNA-seq, and a significantly downregulated lncRNA IALNCR targeting MAPK8/JNK1 (a key regulatory factor of apoptosis) was identified through the lncRNA-mRNA coexpression network analysis. In this study, the function of IALNCR in regulating apoptosis to affect BVDV replication was further explored. Our results showed that BVDV infection-induced downregulation of the lncRNA IALNCR in the host cells could suppress the expression of MAPK8/JNK1 at both the mRNA and protein levels, thereby indirectly promoting the activation of caspase-3, leading to cell-autonomous apoptosis to antagonize BVDV replication. This was further confirmed by the small interfering RNA (siRNA)-mediated knockdown of the lncRNA IALNCR. However, the overexpression of the lncRNA IALNCR inhibited apoptosis and promoted BVDV replication. In conclusion, our findings demonstrated that the lncRNA IALNCR plays an important role in regulating host antiviral innate immunity against BVDV infection. IMPORTANCE Bovine viral diarrhea-mucosal disease caused by BVDV is an important viral disease in cattle, causing severe economic losses to the cattle industry worldwide. The molecular mechanisms of BVDV-host interactions are complex. To date, most studies focused only on how BVDV escapes host innate immunity. By contrast, how the host cell regulates anti-BVDV innate immune responses is rarely reported. In this study, a significantly downregulated lncRNA, with a potential function of inhibiting apoptosis (inhibiting apoptosis long noncoding RNA, IALNCR), was obtained from the lncRNA expression profiles of BVDV-infected cells and was experimentally evaluated for its function in regulating apoptosis and affecting BVDV replication. We demonstrated that downregulation of BVDV infection-induced lncRNA IALNCR displayed antiviral function by positively regulating the MAPK8/JNK1 pathway to promote cell apoptosis. Our data provided evidence that host lncRNAs regulate the innate immune response to BVDV infection.

Surface Defect-Involved and Single-Color Electrochemiluminescence of Gold Nanoclusters for Immunoassay.

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 (N2H4) 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/N2H4 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.

A General Route for Chemiluminescence of n-Type Au Nanocrystals.

The photoluminescence, electroluminescence, and electrochemiluminescence from nanocrystals (NCs) have been extensively exploited for both fundamental and applied investigation over two decades, while the understanding of chemiluminescence (CL) from NCs is still far from clear by now. Herein, a general route for triggering CL from NC luminophore is proposed by extensively exploiting the charge transfer between n-type NCs and oxidants. Oxidants, such as K2S2O8, H2O2, KMnO4, and NaClO, can chemically inject the hole onto the valence band (VB) of methionine-capped n-type AuNCs (Met@AuNCs) and enable the occurrence of efficient radiative-charge-recombination between the chemically injected exogenous VB hole and the pre-existed endogenous conduction band (CB) electron, which eventually results in single-color and defect-involved CL with the maximum emission wavelength around 824 nm. The CL of Met@AuNCs/oxidant is qualified for ultrasensitive CL immunoassay in a similar procedure to the biotin-avidin and magnetic separation involved commercial CL immunoassay and exhibits acceptable performance for linearly determining carcinoembryonic antigen from 50 pg/mL to 100 ng/mL with a limit of detection of 10 pg/mL (S/N = 3). This strategy provides a general route to develop nanoparticulate CL luminophores and might eventually enable CL multiplexing assay via extensively exploiting the CL of different wavebands.

Glow and Flash Adjustable Chemiluminescence with Tunable Waveband from the Same CuInS2@ZnS Nanocrystal Luminophore.

All commercial chemiluminescence (CL) assays are conducted with either glow or flash CL of eye-visible waveband from chemical luminophores. Herein, glow and flash, as well as waveband adjustable CL from the same nanoparticle luminophore of thiol-capped CuInS2@ZnS nanocrystals (CIS@ZnS-Thiol), are proposed via extensively exploiting the differed redox nature of CL triggering reagents. Taking thiosalicylic acid (TSA) as the model thiol-capping agent, the electron-injection-initiated charge transfer between CIS@ZnS-TSA and reductant can bring out efficient glow CL while the hole-injection-initiated charge transfer between CIS@ZnS-TSA and oxidant can give off obvious flash CL under optimum conditions. The maximum emission wavelength for CL of CIS@ZnS-TSA is adjustable from 730 nm to 823 nm via employing different triggering agents. Promisingly, the coexistent reductant of N2H4·H2O and oxidant of H2O2 can be employed as dual triggering reagents to trigger eye-visible and highly efficient flash CL from CIS@ZnS-TSA. The maximum emission intensity for flash CL of CIS@ZnS-TSA/N2H4-H2O2 is 101-fold greater than the glow CL of CIS@ZnS-TSA/N2H4 and 22-fold greater than the flash CL of CIS@ZnS-TSA/H2O2, respectively. The flash CL from CIS@ZnS-TSA/N2H4-H2O2 is qualified for highly sensitive and selective CL immunoassay in a commercialized typical procedure with the entire operating process manually terminated within 35 min.

Selectively Lighting Up Singlet Oxygen via Aggregation-Induced Electrochemiluminescence Energy Transfer.

Singlet oxygen (1O2) is an important reactive oxygen species (ROS) that is intensively involved in natural photochemical and photobiological processes. Herein, selectively lighting up 1O2 is achieved in the aggregation-induced emission (AIE) of electrochemiluminescence (ECL) from the Zn2+-mediated AIE assembly of Au nanoclusters (Zn2+-AIE-AuNCs). Zn2+-AIE-AuNCs can exhibit efficient AIE ECL and photoluminescence (PL) along with 1O2 generation in energy and charge transfer routes, respectively. The AIE ECL of the Zn2+-AIE-AuNCs/tripropylamine (TEA) system in carbonate buffer is located around 703 nm with the dimeric aggregate of 1O2 as an emitter because electrochemically oxidizing coexisted Zn2+-AIE-AuNCs and TEA in carbonate buffer would promote the oxygen vacancy (Ov) of Zn2+-AIE-AuNCs, which could selectively enable the generation of emissive singlet oxygen in the energy transfer route by effectively transferring the energy from excited singlet Zn2+-AIE-AuNCs to the triplet ground state of dissolved oxygen (3O2). No emissive 1O2 is detected via electrochemically oxidizing the Zn2+-AIE-AuNCs in the case without either carbonate buffer or TEA, and the Zn2+-AIE-AuNCs/TEA system can only exhibit AIE ECL around 485 nm with Zn2+-AIE-AuNCs as the emitter in carbonate-free buffers. Photoexciting Zn2+-AIE-AuNCs merely brings out band-gap-engineered AIE PL around ∼485 nm with Zn2+-AIE-AuNCs as the emitter, which manifests that the 1O2 generated in the charge transfer route via photoexciting Zn2+-AIE-AuNCs is un-emissive. This work not only proposes an effective strategy for AIE with 1O2 as an emitter but also opens a promising way to selectively light up 1O2.

Coreactant-Free and Direct Electrochemiluminescence from Dual-Stabilizer-Capped InP/ZnS Nanocrystals: A New Route Involving n-Type Luminophore.

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/ZnSMPA-MSA. The electron-rich InP/ZnSMPA-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/ZnSMPA-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/ZnSMPA-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.

Low-Triggering-Potential Electrochemiluminescence from Surface-Confined CuInS2@ZnS Nanocrystals and their Biosensing Applications.

Electrochemiluminescence (ECL) of low triggering potential is strongly anticipated for ECL assays with less inherent electrochemical interference and improved long-term stability of the working electrode. Herein, effects of the thiol capping agents and the states of luminophores, i.e., the thiol-capped CuInS2@ZnS nanocrystals (CuInS2@ZnS-Thiol), on the ECL triggering potential of CuInS2@ZnS-Thiol/N2H4·H2O were explored on the Au working electrode. The thiol capping agent of glutathione (GSH) not only enabled CuInS2@ZnS-Thiol/N2H4·H2O with the stronger oxidative-reduction ECL than other thiol capping agents but also demonstrated the largest shift for the ECL triggering potential of CuInS2@ZnS-Thiol/N2H4·H2O upon changing the luminophores from the monodispersed state to the surface-confined state. CuInS2@ZnS-GSH/N2H4·H2O exhibited an efficient oxidative-reduction ECL around 0.78 V (vs Ag/AgCl) with CuInS2@ZnS-GSH of the monodispersed state. Upon employing CuInS2@ZnS-GSH as the ECL tag and immobilizing them onto the Au working electrode, the oxidative-reduction ECL of CuInS2@ZnS-GSH/N2H4·H2O was lowered to 0.32 V (vs Ag/AgCl), which was about 0.88 V lower than that of traditional Ru(bpy)32+/TPrA (typically ∼1.2 V, vs Ag/AgCl). The ECL of the CuInS2@ZnS-GSH/N2H4·H2O system with the luminophore of both monodispersed and surface-confined states was spectrally identical to each other, indicating that this surface-confining strategy exhibited negligible effect on the excited state for the ECL of CuInS2@ZnS-GSH. A surface-confined ECL sensor around 0.32 V was fabricated with CuInS2@ZnS-GSH as a luminophore, which could sensitively and selectively determine the K-RAS gene from 1 to 500 pM with a limit of detection at 0.5 pmol L-1 (S/N = 3).