A multi-modal biosensing platform based on Ag-ZnIn2S4@Ag-Pt nanosignal probe-sensitized UiO-66 for ultra-sensitive detection of penicillin

We designed a multi-modal biosensing platform for versatile detection of penicillin based on a unique Ag-ZnIn2S4@Ag-Pt signal probe-sensitized UiO-66 metal-organic framework. Firstly, a large number of Ag-ZnIn2S4 quantum dots (AZIS QDs) were attached to Ag-Pt NPs, preparing a new multi-signal probe AZIS QDs@Ag-Pt NPs with excellent photoelectrochemistry (PEC), electrochemiluminescence (ECL), and fluorescence (FL) signals. Moreover, the AZIS QDs@Ag-Pt NPs signal probe can well match the energy level of UiO-66 metal-organic framework (MOF) with good photoelectric property, which can reverse the PEC current of UiO-66 to reduce false positives in detection. When penicillin was present, it bound to its aptamer to release the multifunctional signal probes, which can generate PEC, ECL, and PL signals, thus realizing ultrasensitive detection of penicillin by multi-signals. This work creates a novel three-signal QDs probe, which makes a great contribution to multi-mode photoelectric sensing analysis. The LOD of this work (3.48 fg·mL-1) was much lower than the MRLs (Maximum Residue Levels) established by the EU (4 ng·mL-1). The newly developed multi-mode biosensor has good practical application values in various biological detection, food assay, and early disease diagnosis.

Two Birds with one Stone: Dual-mode immunoassay constructed using a novel emitter ethylene glycol-induced perylene diimide and a multifunctional ANS probe

Perylene diimide (PDI) is a readily reducible electron-deficient dye that exhibits strong photoluminescent properties, providing new opportunities for synthesizing novel electrochemiluminescence (ECL) emitters. In this study, ethylene glycol (EG) was used to induce the self-assembly of PDI supramolecules for the preparation of ultrathin EG-PDI nanosheets characterized by low crystallinity and weak stacking interaction. Notably, EG-PDI integrates luminescent and catalytic functions into one device, accelerating the interfacial electron transfer and the faster charge transfer kinetics of EG-PDI with K2S2O8. Furthermore, the narrow band gap of EG-PDI facilitates its excitation at an ultra-low potential (-0.3 V). To improve the efficiency of tumor marker analysis, multifunctional Au nanostars (ANS) was introduced both as an energy acceptor of the ECL system and a probe for the photothermal system. Dual-mode immunoassay have demonstrated superior analytical performance in detecting alpha-fetoprotein (AFP), meeting the requirements of modern clinical diagnostics in resource-limited environments.

A signal amplification electrochemiluminescence biosensor based on Ru(bpy)32+ and β-cyclodextrin for detection of AFP

By combining two different materials, metal-organic frameworks (MOF) and β-cyclodextrins (β-CD), a signal amplification electrochemical luminescence (ECL) immunosensor was constructed to realize the sensitive detection of AFP. The indium-based metal-organic framework (In-MOF) was used as the carrier of Ru(bpy)32+, and Ru(bpy)32+ was immobilized by In-MOF through suitable pore size and electrostatic interaction. At the same time, using host-guest recognition, β-CD enriched TPA into the hydrophobic cavity for accelerating the electronic excitation of TPA, then, achieving the purpose of signal amplification. The signal amplification immunosensor structure is constructed among the primary antibody Ab1 connected to the Ru(bpy)32+@In-MOF modified electrode, AFP, BSA and the secondary antibody (Ab2) loaded with TPA-β-CD. The immunosensor has a good linearity in the range of 10-5 ng/mL-50 ng/mL, and the low limit of detection (LOD) is 1.1 × 10-6 ng/mL. In addition, the electrochemiluminescence immunosensor that we designed has strong stability, good selectivity and repeatability, which provides a choice for the analysis of AFP.

Tetrahedral DNA nanostructure enhanced toehold-mediated strand displacement for highly sensitive electrochemiluminescence assay of CA125

Cancer antigen 125 (CA125) is a typical tumor marker of ovarian cancer. Here, a multi-amplified electrochemiluminescence (ECL) aptasensor was developed for efficient recognition of CA125 using tetrahedral DNA nanostructure (TDN) enhanced toehold-mediated strand displacement (TMSD) coupled with gold nanoparticles/Ru(bpy)32+/metal-organic framework (AuNPs/Ru/ZIF-MOF) signal probe. AuNPs and Ru(bpy)32+ modified ZIF-MOF acted as initial ECL signal and further used for the immobilization of TDN, the activated DNA templates on the surface of TDN were firstly hybridized with ferrocene labeled DNA probe (S6) and S5, in which, S6 acted as the energy acceptor of ECL signal from Ru(bpy)32+, making the sensor in a "signal-off" state. After the specific recognition of aptamer (AP) with CA125, DNA initiator (S7) was freed to induce the happen of TMSD by using S8 as the helper DNA, accompanying with the release of S6 from the electrode surface and the recovery of Ru(bpy)32+ ECL signal, making the sensor in a "signal-on" state. Then, S7 was recycled for the next TMSD, making the sensor highly sensitive with a detection limit of 6 × 10-3 pg/mL. Moreover, the proposed aptasensor achieved high performance for CA125 detection in human serum samples, illustrating the reliability of the sensor in clinical analysis.

HOF-101-based dual-mode biosensor for photoelectrochemical/electrochemiluminescence detection and imaging of oxytetracycline

A unique hydrogen-bonded organic frameworks (HOF-101)-based photoelectrochemical (PEC) and electrochemiluminescence (ECL) dual-mode biosensor using polydopamine nanoparticles (PDAs) as quencher was constructed for ultrasensitive detection and imaging of oxytetracycline (OXY). In particular, HOF-101 was a superior ECL material and can be observed with the naked eye. Furthermore, it also had outstanding PEC signal, so HOF-101 was a new dual-signal material with excellent performance, thus it was explored to realize dual-mode detection. As the main component of natural melanin, PDAs not only had good biocompatibility, but also contained rich functional groups on the surface. Additionally, PDAs had excellent light absorption ability and poor conductivity, which made it the excellent photoquencher. In this work, PDAs were introduced on the surface of HOF-101 to quench its ECL and PEC signals by using the dual-aptamer sandwich method, achieving ultrasensitive detection of antibiotic OXY. Particularly for ECL detection, HOF-101 was firstly used to visually detect OXY. The detection range can reach 0.1 pM-100 nM, and the limit of detection (LOD) can reach 0.04 pM. This work showed a great contribution to the development of new ECL-PEC materials and ECL visualization analysis, which had outstanding application potential in the fields of food safety and biochemical analysis.

Signal-to-noise ratio to assess magnitude, kinetics and impact on pharmacokinetics of the immune response to an adalimumab biosimilar

Background: The antidrug antibody (ADA) signal-to-noise (S/N) ratio was explored as a novel immunogenicity measure to evaluate the immune response of healthy subjects to a single dose of GP2017, an adalimumab biosimilar. Methodology/results: Bioanalytical methods used for the analysis of ADA S/N ratios and ADA titers were validated for sensitivity, precision and drug interference. ADA S/N ratios strongly correlated with ADA titers. Correlations between ADA area under the curve and ADAmax and pharmacokinetics (PK) were stronger for ADA S/N ratio than for ADA titers. Conclusion: ADA S/N ratio allowed for a more sensitive evaluation of the magnitude and kinetics of the immune response, was better correlated with adalimumab PK and was superior to ADA titers in assessing the impact of the immune response on PK.

Nitrogen-Doped Graphene Quantum Dots as Electrochemiluminescence-Emitting Species for Sensitive Detection of KRAS G12C Mutation via PET-RAFT

The levels of KRAS G12C point mutation is recognized to be closely related to the earlier diagnosis of non-small cell lung cancer (NSCLC). Here, based on nitrogen-doped graphene quantum dots (NGQDs) and photo-induced electron/energy transfer reversible addition-fragment chain transfer (PET-RAFT) signal amplification strategy, we fabricated a novel electrochemiluminescence (ECL) biosensor for the detection of KRAS G12C mutation for the first time. NGQDs as ECL-emitting species with cathodic ECL were prepared by a simple calcination method. Firstly, KRAS G12C mutation DNA, i. e., target DNA (tDNA), was captured by specific identification with hairpin DNA (hDNA). Then, PET-RAFT was initiated by blue light, and large numbers of monomers were successfully polymerized to form controllable polymer chains. Lastly, massive NGQDs was introduced via amidation reaction with N-(3-aminopropyl)methacrylamide hydrochloride (APMA), which significantly amplified the ECL signal intensity. Under optimal conditions, this biosensor achieved a good linear relationship between ECL intensity and logarithm of the levels of KRAS G12C mutation in the range from 10 fM to 10 nM. Moreover, this strategy exhibited high selectivity and excellent applicability for KRAS G12C mutation detection in the serum samples. Therefore, this biosensor has great potential in clinical diagnosis and practical application.

Entropy-driven assisted T7 RNA polymerase amplification-activated CRISPR/Cas13a activity for SARS-CoV-2 detection in human pharyngeal swabs and environment by an electrochemiluminescence biosensor

In this study, we introduce an electrochemiluminescence (ECL) sensing platform based on the "Entropy-driven triggered T7 amplification-CRISPR/Cas13a system" (EDT-Cas). This platform combines a programmable entropy-driven cycling strategy, T7 RNA polymerase, and the CRISPR/Cas13a system to amplify the determination of the SARS-CoV-2 RdRp gene. The Ti₃C₂T_x-compliant ECL signaling molecule offers unique benefits when used with the ECL sensing platform to increase the assay sensitivity and the electrode surface modifiability. To obtain the T7 promoter, the SARS-CoV-2 RdRp gene may first initiate an entropy-driven cyclic amplification response. Then, after recognizing the T7 promoter sequence on the newly created dsDNA, T7 RNA polymerase starts transcription, resulting in the production of many single-stranded RNAs (ssRNAs), which in turn trigger the action of CRISPR/Cas13a. Finally, Cas13a/crRNA identifies the transcribed ssRNA. When it cleaves the ssRNA, many DNA reporter probes carrying -U-U- are cleaved on the electrode surface, increasing the ECL signal and allowing for the rapid and highly sensitive detection of SARS-CoV-2. With a detection limit of 7.39 aM, our method enables us to locate the SARS-CoV-2 RdRp gene in clinical samples. The detection method also demonstrates excellent repeatability and stability. The SARS-CoV-2 RdRp gene was discovered using the "Entropy-driven triggered T7 amplification-CRISPR/Cas13a system" (EDT-Cas). The developed ECL test had excellent recoveries in pharyngeal swabs and environmental samples. It is anticipated to offer an early clinical diagnosis of SARS-CoV-2 and further control the spread of the pandemic.

Unique Electron-Transfer-Mediated Electrochemiluminescence of AuPt Bimetallic Nanoclusters and the Application in Cancer Immunoassay

Noble Metal nanoclusters (NCs) are promising electrochemiluminescence (ECL) emitters due to their amazing optical properties and excellent biocompatibility. They have been widely used in the detection of ions, pollutant molecules, biomolecules, etc. Herein, we found that glutathione-capped AuPt bimetallic NCs (GSH-AuPt NCs) emitted strong anodic ECL signals with triethylamine as co-reactants which had no fluorescence (FL) response. Due to the synergistic effect of bimetallic structures, the ECL signals of AuPt NCs were 6.8 and 94 times higher than those of monometallic Au and Pt NCs, respectively. The electric and optical properties of GSH-AuPt NCs differed from those of Au and Pt NCs completely. An electron-transfer mediated ECL mechanism was proposed. The excited electrons may be neutralized by Pt(II) in GSH-Pt and GSH-AuPt NCs, resulting in the vanished FL. Furthermore, abundant TEA radicals formed on the anode contributed electrons to the highest unoccupied molecular orbital of GSH-Au_2.5Pt NCs and Pt(II), booming intense ECL signals. Because of the ligand effect and ensemble effect, bimetallic AuPt NCs exhibited much stronger ECL than GSH-Au NCs. A sandwich-type immunoassay for alpha fetoprotein (AFP) cancer biomarkers was fabricated with GSH-AuPt NCs as signal tags, which displayed a wide linear range from 0.01 to 1000 ng·mL^-1 and a limit of detection (LOD) down to 1.0 pg·mL^-1 at 3S/N. Compared to previous ECL AFP immunoassays, this method not only had a wider linear range but also a lower LOD. The recoveries of AFP in human serum were around 108%, providing a wonderful strategy for fast, sensitive, and accurate cancer diagnosis.

Ruthenium(II) complex-grafted conductive metal-organic frameworks with conductivity- and confinement-enhanced electrochemiluminescence for ultrasensitive biosensing application

Improving the electrochemiluminescence (ECL) performance of luminophores is an ongoing research hotspot in the ECL realm. Herein, a high-performance metal-organic framework (MOF)-based ECL material (Ru@Ni₃(HITP)₂, HITP = 2,3,6,7,10,11-hexaiminotriphenylene) with conductivity- and confinement-enhanced ECL was successfully constructed by using conductive MOF Ni₃(HITP)₂ as the carrier to graft Ru(bpydc)₃^4- (H₂bpydc = 2,2'-bipyridine-4,4'-dicarboxylic acid) into the channels of Ni₃(HITP)₂. Compared to Ru@Cu₃(HITP)₂ and Ru@Co₃(HITP)₂ with relatively low conductivity, the ECL intensity of Ru@Ni₃(HITP)₂ was prominently increased about 6.76 times and 18.8 times, respectively, which demonstrated that the increase in conductivity induced the ECL enhancement of the MOF-based ECL materials. What's more, the hydrophobic and porous Ni₃(HITP)₂ can not only effectively enrich the lipophilic tripropylamine (TPrA) coreactants in its channels to enhance the electrochemical oxidation efficiency of TPrA, but also provide a conductive reaction micro-environment to boost the ECL reaction between Ru(bpydc)₃^3- intermediates and TPrA^• in confined spaces, thus realizing a remarkable confinement-enhanced ECL. Considering the excellent ECL performance of Ru@Ni₃(HITP)₂, an ultrasensitive ECL biosensor was prepared based on the Ru@Ni₃(HITP)₂ ECL indicator combining an exonuclease I-aided target cycling amplification strategy for thrombin determination. The constructed ECL biosensor showcased a wide linear range from 1 fM to 1 nM with a low detection limit of 0.62 fM. Overall, the conductivity- and confinement-enhanced ECL based on Ru@Ni₃(HITP)₂ provided effective and feasible strategies to enhance ECL performance, which paved a promising avenue for exploring high-efficient MOF-based ECL materials and thus broadened the application scope of conductive MOFs.

Versatile FeMoOv nanozyme bipolar electrode electrochemiluminescence biosensing and imaging platform for detection of H2O2 and PSA

In this work, a unique FeMoOv nanozyme-bipolar electrode (NM-BPE) electrochemiluminescence (ECL) biosensing and imaging platform was proposed for the first time to realize sensitive detection of target hydrogen peroxide (H₂O₂) and prostate specific antigen (PSA). Considering the advantage that the cathode and anode poles of the bipolar electrode (BPE) can be modified respectively, this work was carried out using anode equipped with ECL reagent bipyridine ruthenium (Ru(bpy)₃²⁺), and cathode equipped with the Fe-doped molybdenum oxide/Au nanoparticles (FeMoOv/AuNPs) with excellent peroxidase (POD) and catalase (CAT)-like activity. Because FeMoOv/AuNPs show efficient enzyme catalysis effect and can greatly promote the decomposition of H₂O₂, thus the electron transfer rate in the NM-BPE system would be much accelerated to enhance the ECL signal of Ru(bpy)₃²⁺. Based on this principle, this work not only realized sensitive detection of H₂O₂, but also ingeniously designed an sandwich immunosensor using FeMoOv/AuNPs as recognition probe to mediate the ECL response on the anode, achieving highly sensitive detection of PSA. Furthermore, a unique mobile phone ECL imaging system was developed for assay of PSA at different concentrations, which opened a new portable imaging sensing device for bioassays. This work was the first time to combine nanozymes with bipolar electrodes for ECL analysis and imaging, which not only broadened the applications of nanozymes, but also pioneered the new joint ECL research technique of bipolar electrode and ECL imaging in bioassays, showing great application prospect for multiple detection of proteins, nucleic acids and cancer cells.

Acidic pH and thiol-driven homogeneous cathodic electrochemiluminescence strategy for determining the residue of organophosphorus pesticide in Chinese cabbage

Electrochemiluminescent (ECL) sensors for organophosphorus pesticides (OPs) have received considerable attention, whereas complicated electrode's immobilization, response to single hydrolysate and anodic emission correlated with ECL assays restrict their potential utilization. Herein, we developed a homogeneous dual-response cathodic ECL system for highly sensitive and reliable analysis of OP using CdTe QDs as emitters. CdTe QDs, emitting red light, were fabricated through a hydrothermal reaction and generated anodic and cathodic ECL emission upon stimulation of tripropyl amine and K₂S₂O₈, respectively. Notably, CdTe QDs-K₂S₂O₈ showed a simultaneous response to thiol and acidic pH, and were regarded as a ECL sensor for methidathion with limit of detection of 0.016 ng/mL based on hydrolysis of acetylthiocholine into thiocholine and CH₃COOH by acetylcholinesterase (AChE) and OPs' inhibition on AChE activity. This sensor also exhibited good practicability to detect methidathion in Chinese cabbage. Overall, the sensor will supply more useful information for ensuring OPs-related food safety.

A portable electrochemiluminescence aptasensor for β-lactoglobulin detection

Cow’s milk allergy is one of the most common food allergies in children with a prevalence of around 2.5%. Milk contains several allergens; the main ones are caseins and β-lactoglobulin (β-LG). At regulatory level, β-LG is not explicitly named, but milk is included in the list of substances or products causing allergies or intolerances. Hence, the presence of β-LG can be a useful marker for determining the presence of milk in food. In this work, we present an aptasensor based on electrochemiluminescence (ECL) for the quantification of β-LG in real food matrices displaying integrated advantages consisting of high specificity, good sensitivity, portability, and cost effectiveness. The performance and applicability of this sensor were tested by analyzing a sample of skimmed milk and an oat-based drink proposed as a vegetable substitute for milk of animal origin. We obtained a linear correlation between the intensity of the signal and the concentration of β-LG standard solutions (y = x * 0.00653 + 1.038, R² = 0.99). The limit of detection (LOD) and the limit of quantification (LOQ) were found to be 1.36 and 4.55 μg L⁻¹, respectively.

Gold nanoparticle-based signal amplified electrochemiluminescence for biosensing applications

Since the content levels of biomarkers at the early stage of many diseases are generally lower than the detection threshold concentration, achieving ultrasensitive and accurate detection of these biomarkers is still one of the major goals in bio-analysis. To achieve ultrasensitive and reliable bioassay, it requires developing highly sensitive biosensors. Among all kinds of biosensors, electrogenerated chemiluminescence (ECL) based biosensors have attracted enormous attention due to their excellent properties. In order to improve the performance of ECL biosensors, gold nanoparticles (Au NPs) have been widely utilized as signal amplification tags. The introduction of Au NPs could dramatically enhance the performance of the constructed ECL biosensors via diverse ways such as electrode modification material, efficient energy acceptor in ECL resonant energy transfer (ECL-RET), reaction catalyst, surface plasmon resonance (SPR) enhancer, and as nanocarrier. Herein, we summarize recent developments and progress of ECL biosensors based on Au NPs signal amplification strategies. We will cover ECL applications of Au NPs as a signal amplification tag in the detection of proteins, metal ions, nucleic acids, small molecules, living cells, exosomes, and cell imaging. Finally, brief summary and future outlooks of this field will be presented.

A pH-engineering regenerative DNA tetrahedron ECL biosensor for the assay of SARS-CoV-2 RdRp gene based on CRISPR/Cas12a trans-activity

In this work, we constructed an exonuclease III cleavage reaction-based isothermal amplification of nucleic acids with CRISPR/Cas12a-mediated pH-induced regenerative Electrochemiluminescence (ECL) biosensor for ultrasensitive and specific detection of SARS-CoV-2 nucleic acids for SARS-CoV-2 diagnosis. The triple-stranded nucleic acid in this biosensor has an extreme dependence on pH, which makes our constructed biosensor reproducible. This is essential for effective large-scale screening of SARS-CoV-2 in areas where resources are currently relatively scarce. Using this pH-induced regenerative biosensor, we detected the SARS-CoV-2 RdRp gene with a detection limit of 43.70 aM. In addition, the detection system has good stability and reproducibility, and we expect that this method may provide a potential platform for the diagnosis of COVID-19.

An in situ quenching electrochemiluminescence biosensor amplified with aptamer recognition-induced multi-DNA release for sensitive detection of pathogenic bacteria

An in situ quenching electrochemiluminescence (ECL) biosensor sensitized with the aptamer recognition-induced multi-DNA release was designed for pathogenic bacterial detection. Benefitting from the high binding ability of the aptamer to targets and large enrichment capacity of magnetic bead separation, the proposed sensing system not only exhibited outstanding identification to Staphylococcus aureus (S. aureus) among various bacteria, but also released abundant signal transduction DNAs. One S. aureus initiated the dissociation of four kinds of DNA sequences, achieving a one-to-multiple amplification effect. These multi-DNA strands were further hybridized with capture DNA, which were assembled to an electrode modified with Ru(bpy)₃²⁺-conjugated silica nanoparticles (RuSi NPs). Then, glucose oxidase (GOD) was introduced via the functional conjugation of GOD-multi-DNA, leading to the presence of H₂O₂ by in situ catalysis of GOD on glucose. Relying on the ECL quenching of H₂O₂ in the Ru(bpy)₃²⁺ system, S. aureus was quantified with a linear range from 10 to 10⁷ CFU/mL. In addition, the negative results of non-target bacteria and good recovery efficiency in real samples revealed the system's remarkable selectivity and potential application in infectious food tests.

Hybridization chain reaction circuit-based electrochemiluminescent biosensor for SARS-cov-2 RdRp gene assay

In this work, we designed an ECL ratiometric biosensor with a three-stranded Y-type DNA (Y-DNA) probe and induced a hybridization chain reaction (HCR) for the highly sensitive detection of SARS-CoV-2 nucleic acid. The important component of this system is the self-assembled Y-Shaped probe based on three nucleic acids. Y1, Y2, and Y3 can be linked by complementary base pairing to Hairpin1 (H1), Hairpin2 (H2), and Ru modified DNA (Ru1), respectively. H1 and H2 can trigger the HCR reaction when activated by the SARS-CoV-2 RdRp gene and the 5′ end of Ru1. The 5′ end of Ru1 is modified with the Ru complex, which can produce a strong electrochemiluminescence luminescence signal at 620 nm under an applied voltage. Through the amplification of Y-DNA-induced HCR reaction, Ru1 on the electrode surface gradually increased, the ECL signal at 460 nm was gradually quenched, and the signal at 620 nm was steadily generated. The SARS-CoV-2 RdRp gene can be quantified according to the degree of decrease of ECL signal at 460 nm and the increase of ECL signal at 620 nm. Combining the two signal amplification strategies, this ratiometric ECL biosensor can accurately and efficiently detect the target gene with a detection limit of 59 aM.

A strategy combining 3D-DNA Walker and CRISPR-Cas12a trans-cleavage activity applied to MXene based electrochemiluminescent sensor for SARS-CoV-2 RdRp gene detection

Early diagnosis and timely management of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) are the keys to preventing the spread of the epidemic and controlling new infection clues. Therefore, strengthening the surveillance of the epidemic and timely screening and confirming SARS-CoV-2 infection is the primary task. In this work, we first proposed the idea of activating CRISPR-Cas12a activity using double-stranded DNA amplified by a three-dimensional (3D) DNA walker. We applied it to the design of an electrochemiluminescent (ECL) biosensor to detect the SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) gene. We first activated the cleavage activity of CRISPR-Cas12a by amplifying the target DNA into a segment of double-stranded DNA through the amplification effect of a 3D DNA walker. At the same time, we designed an MXene based ECL material: PEI-Ru@Ti₃C₂@AuNPs, and constructed an ECL biosensor to detect the RdRp gene based on this ECL material as a framework. Activated CRISPR-Cas12a cleaves the single-stranded DNA on the surface of this sensor and causes the ferrocene modified at one end of the DNA to move away from the electrode surface, increasing the ECL signal. The extent of the change in electrochemiluminescence reflects the concentration of the gene to be measured. Using this system, we detected the SARS-CoV-2 RdRp gene with a detection limit of 12.8 aM. This strategy contributes to the rapid and convenient detection of SARS-CoV-2-associated nucleic acids and promotes the clinical application of ECL biosensors based on CRISPR-Cas12a and novel composite materials.

Graphene-PtPd nanocomposite for low-potential-driven electrochemiluminescent determination of carcinoembryonic antigen using Ru(bpy)32

As well known, the electrochemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺) heavily relies on highly positive or negative triggered voltage, prejudicing the detection toward the bio-molecules. In this work, Ru(bpy)₃²⁺ could generate enhanced and stable ECL at a low potential of 0.05 V (vs. Ag/AgCl) on graphene-PtPd hybrid, attributing to its excellent electrocatalysis from the synergistic effect between Pt and Pd. The obtained low-potential-driven ECL could be quenched by MoS₂ nanoflowers. Based on the quenching effect, a sandwich "signal-off" ECL immunosensor was fabricated to sensitively detect carcinoembryonic antigen (CEA). A linear calibration curve from 1 fg mL^-1 to 1 ng mL^-1 was obtained along with a low detection limit of 0.54 fg mL^-1 (S/N = 3) under optimal conditions. The sensor showed satisfactory specificity, stability, and reproducibility and was successfully applied to determine CEA in actual samples. The recoveries ranged from 98.80 to 100.23%, and the relative standard deviation (RSD) was lower than 5%. Above all, this work explored new materials in low-potential-driven ECL system and provided a reliable sensing strategy for clinical applications.

Versatile photoelectrochemical and electrochemiluminescence biosensor based on 3D CdSe QDs-DNA nanonetwork-SnO2 nanoflower coupled with DNA walker amplification for HIV detection

A novel 3D CdSe quantum dots (QDs)-DNA nanonetwork was assembled to sensitize the mesoporous SnO₂ photoelectrochemical (PEC) substrate, which was coupled with a biped-DNA walker multiple amplification technique to design a versatile electrochemiluminescence (ECL) and PEC biosensor for dual detection of HIV. Firstly, the photosensitive CdSe QDs and SnO₂ nanoflowers have well-matched band-edge energy level, thus their complex can promote effective transfer of the photogenerated carriers, and show better PEC and ECL property. Then, a novel 3D CdSe QDs-DNA nanonetwork was assembled and loaded with a large amount of QDs, which was used as multifunctional PEC and ECL probes. Moreover, the target-triggered biped DNA walker-cascade amplification method was introduced to generate a large amount of output DNA, which was used to link numerous 3D CdSe QDs-DNA nanonetwork probes to the electrode, generating greatly amplified signals for sensitive assay of HIV. The highly photosensitive 3D CdSe QDs-DNA reticulated nanomaterials have high stability and controllability, and display significantly improved PEC and ECL signals of the biosensor. This method opened a new photoelectric nanocomposite of QDs-sensitized SnO₂ nanoflower, and developed a versatile biosensing strategy using the 3D CdSe QD_S DNA sensitization probes for ultra-sensitive detection of biomolecules, which is important for the early diagnosis of diseases.

Machine Learning Analysis for Phenolic Compound Monitoring Using a Mobile Phone-Based ECL Sensor

Machine learning (ML) can be an appropriate approach to overcoming common problems associated with sensors for low-cost, point-of-care diagnostics, such as non-linearity, multidimensionality, sensor-to-sensor variations, presence of anomalies, and ambiguity in key features. This study proposes a novel approach based on ML algorithms (neural nets, Gaussian Process Regression, among others) to model the electrochemiluminescence (ECL) quenching mechanism of the [Ru(bpy)₃]²⁺/TPrA system by phenolic compounds, thus allowing their detection and quantification. The relationships between the concentration of phenolic compounds and their effect on the ECL intensity and current data measured using a mobile phone-based ECL sensor is investigated. The ML regression tasks with a tri-layer neural net using minimally processed time series data showed better or comparable detection performance compared to the performance using extracted key features without extra preprocessing. Combined multimodal characteristics produced an 80% more enhanced performance with multilayer neural net algorithms than a single feature based-regression analysis. The results demonstrated that the ML could provide a robust analysis framework for sensor data with noises and variability. It demonstrates that ML strategies can play a crucial role in chemical or biosensor data analysis, providing a robust model by maximizing all the obtained information and integrating nonlinearity and sensor-to-sensor variations.

Quenching Behavior of the Electrochemiluminescence of Ru(bpy)32+ /TPrA System by Phenols on a Smartphone-Based Sensor

Phenolic compounds such as vanillic and p-coumaric acids are pollutants of major concern in the agro-industrial processing, thereby their effective detection in the industrial environment is essential to reduce exposure. Herein, we present the quenching effect of these compounds on the electrochemiluminescence (ECL) of the Ru(bpy)32+ /TPrA (TPrA=tri-n-propylamine) system at a disposable screen-printed carbon electrode. Transient ECL profiles are obtained from multiple video frames following 1.2 V application by a smartphone-based ECL sensor. A wide range of detection was achieved using the sensor with limit of detection of 0.26 μM and 0.68 μM for vanillic and p-coumaric acids, respectively. The estimated quenching constants determined that the quenching efficiency of vanillic acid is at least two-fold that of p-coumaric acid under the current detection conditions. The present ECL quenching approach provided an effective method to detect phenolic compounds using a low-cost, portable smartphone-based ECL sensor.

Rapid, ultrasensitive and non-enzyme electrochemiluminescence detection of hydrogen peroxide in food based on the ssDNA/g-C3N4 nanosheets hybrid

Hydrogen peroxide (H2O2) is usually used as a fungicide in food, it is carcinogenic, accelerates aging or inducing toxic effects such as cardiovascular disease. Herein, to meet the demand for effective and fast detection of H2O2 in food, a novel non-enzymatic electrochemiluminescence (ECL) sensor based on single-stranded DNA (ssDNA)/g-C3N4 nanosheets (NS) was established. The ssDNA/g-C3N4 NS hybrid was prepared by simple mixing g-C3N4 NS and ssDNA solution together. The prepared ssDNA/g-C3N4 NS exhibited improved peroxidase-like activity and was modified on a glassy carbon electrode to catalyze the ECL reaction of luminol-H2O2 to amplify the luminescence signal. Under the optimized conditions, the proposed sensor exhibits high sensitivity with a limit of detection (LOD) as low as 33 aM H2O2, which is much lower than the vast majority of reported methods. This method enables the reliable responding to H2O2 from the milk samples within 1 min.

Relative Quantification of NaV1.1 Protein in Mouse Brains Using a Meso Scale Discovery-Electrochemiluminescence (MSD-ECL) Method

Densitometric analysis is often used to quantify Na_V1.1 protein on immunoblots, although the sensitivity and dilution linearity of the method are usually poor. Here we present a protocol for quantification of Na_V1.1 in mouse brain tissues using a Meso Scale Discovery-Electrochemiluminescence (MSD-ECL) method. MSD-ECL is based on ELISA (enzyme-linked immunosorbent assay) and uses electrochemiluminescence to produce measurable signals. Two different antibodies are used in this assay to capture and detect Na_V1.1 respectively in brain tissue lysate. The specificity of the antibodies is confirmed by Scn1a gene knock-out tissue. The calibration curve standards used in this assay were generated with mouse liver lysate spiked with mouse brain lysate, instead of using a recombinant protein. We showed that this method was qualified and used for quantification of Na_V1.1 in mouse brain tissues with specificity, accuracy and precision.

A synergistic promotion strategy remarkably accelerated electrochemiluminescence of SnO2 QDs for MicroRNA detection using 3D DNA walker amplification

Developing low-cost and efficient methods to enhance the electrochemiluminescence (ECL) intensity of luminophores is highly desirable and challenging. Herein, we develop a synergistic promotion strategy based on three types of co-reaction accelerators to achieve an efficient SnO2 quantum dots (SnO2 QDs)-based ternary ECL system. Specifically, the MnO2 nanoflowers (MnO2 NFs), Ag nanoparticles (Ag NPs) and hemin/G-quadruplex were rationally selected as co-reaction accelerators. Owing to the synergistic effect, the deft integration of three types of co-reaction accelerators enabled better structural stability, more exposed catalytic active sites, and faster charge transfer, thus more effectively facilitating the reduction of co-reactant (S2O82-) compared with that of the single co-reaction accelerator. To demonstrate the practical utility of this principle, an "on-off-super on" ECL biosensor was constructed in combination with a 3D DNA walker, which showed a superior linear range (10 aM-100 pM) and a low detection limit (2.9 aM) for the highly-sensitive miRNA-21 detection. In general, this work firstly reported that three types of co-reaction accelerators were deftly integrated to remarkably amplify the ECL emission of SnO2 QDs, and provided brand-new perspectives for research on the ingenious design of the structure and component of highly efficient co-reaction accelerators.

Sensitive Detection of Caffeic Acid and Rutin via the Enhanced Anodic Electrochemiluminescence Signal of Luminol

The electrooxidation of phenolic groups of caffeic acid and rutin promote anodic electrochemiluminescence (ECL) luminol substantially. A sensitive, and cost-effective ECL method has thus been developed to detect caffeic acid, ranging from 0.1 to 5.0 μM, with a detection limit of 0.1 μM and rutin ranging from 0.2 to 25 μM with a detection limit of 0.12 μM. Contrarily, phenolic compounds quench the weak cathodic ECL of luminol. Both of anodic and cathodic ECL mechanisms of luminol in the presence of phenolic compounds are analyzed. The method based on the boomed anodic ECL of luminol is comparable to those based on Ru(bpy)₃²⁺ and S₂O₈^2-/O₂ systems. A lower onset potential and price than the other ECL reagents would realize its widely applications in the detection of phenolic compounds in food and medicine.

Screen printed bipolar electrode for sensitive electrochemiluminescence detection of aflatoxin B1 in agricultural products

In order to avoid the occurrence of false positives and false negatives caused by improper pretreatment during the detection of aflatoxin B1 by enzyme linked immunosorbent assay (ELISA). In this paper, we developed a screen printed bipolar electrode (BPE) for sensitive electrochemiluminescence (ECL) detection of aflatoxin B1 in agricultural products. The sensor uses a cathode of closed BPE as a functional sensing interface and an anode as a signal collection interface. In this way, the analyte does not need to participate in the ECL reaction of the anode. It avoids direct contact of photoactive molecules with complex reaction systems and greatly broadens the range of applications for ECL. After mixing the test sample with a known fixed concentration of horseradish peroxidase-labeled AFB1 (HRP-AFB1), they compete for binding to monoclonal antibodies. HRP catalyzes the polymerization of aniline to form polyaniline (PANI). Thereby causing a change in the oxidation-reduction potential and the ECL intensity in the electrochemical system, and then achieve the purpose of detecting the AFB1 concentration in the sample. As a result, the sensor has a good analytical performance for AFB1 with a linear range of 0.1-100 ng mL^-1 and a detection limit of 0.033 ng mL^-1. The sensor avoids the direct contact between the reaction system and the signal measurement system. In recovery experiment for six grains, the results demonstrate that the recovery rate and accuracy of this sensor is better than that of ELISA. This method provides a new idea for the detection of other mycotoxins in grains.

Triple-helix molecular switch-based versatile "off-on" electrochemiluminescence and fluorescence biosensing platform for ultrasensitive detection of lipopolysaccharide by multiple-amplification strategy

Herein, a novel biosensing platform for versatile electrochemiluminescence (ECL) "off" and fluorescence (FL) "on" detection of lipopolysaccharide (LPS) with multiple-amplification strategy is proposed. The specific recognition of target to aptamer on the magnetic beads (MB) firstly released abundant DNA sequences of three kinds. The sequences hybridized with multifunctional molecular beacon (MMB) and initiated numerous bidirectional polymerization and shearing reactions, generating a large number of DNA fragments (a1) by multiple cycling amplification. Then a1 was introduced to the triple-helix sensing system, opening the triple-helix structure. In ECL system, the G-rich chains S2 were exposed to form G-quadruplex-hemin complex in the presence of hemin, which could efficiently quench ECL for "off" detection of LPS. In FL system, the fluorophore FAM and quencher BHQ on S1 chain were separated with opening of triple-helix structure, achieving fluorescence "on" signal for LPS assay. So the versatile platform can achieve greatly amplified ECL and FL signal changes for sensitive assay of LPS, showing wide linear ranges (0.1 fg/mL-0.1 ng/mL by ECL and 10 fg/mL^-1-1 μg/mL by FL) and low detection limits (0.012 fg/mL by ECL and 1.269 fg/mL by FL). Therefore, the present ECL "Off" and FL "On" dual-signal detection patterns for LPS displayed many advantages over other reported methods, which provided an outlook for future applications in clinical diagnosis.

Aptamer based electrochemiluminescent determination of bisphenol A by using carboxylated graphitic carbon nitride

An electrochemiluminescence (ECL) based assay is described for the determination of the endocrine disruptor bisphenol A (BPA). The method is based on the use of carboxylated graphitic carbon nitride (C-g-C₃N₄) carrying an immobilized aptamer against BPA. In the presence of BPA, the ECL signal decreases due to ECL energy transfer from excited-state C-g-C₃N₄ to the BPA oxidation product. Under the optimal conditions, ECL intensity increases linearly in the 0.1 pM to 1 nM BPA concentration range. The detection limit is as low as 30 fM. The assay has excellent sensitivity, outstanding stability and high selectivity. It was applied to the determination of BPA in spiked water samples. Graphical abstract Aptamer modified carboxylated graphitic carbon nitride was synthesized and applied in an electrochemiluminescence-based aptasensor for bisphenol A.

Quantifying Weak Glycan-Protein Interactions Using a Biolayer Interferometry Competition Assay: Applications to ECL Lectin and X-31 Influenza Hemagglutinin

This chapter introduces two formats using bio-layer interferometry competition assays to determine the solution K _D values of weak glycan-protein interactions. This approach overcomes the challenge of determining weak interactions while minimizing the amount of reagents required. Accurate solution K _D values aid in understanding the complex relationships between monomeric versus multimeric interactions and affinity versus avidity. The assays have been applied to a well-studied lectin (Erythrina crista-galli lectin) and influenza hemagglutinin (X-31). The solution K _D values determined from this approach are in good agreement with previous reported literature values from isothermal titration calorimetry and NMR. Additionally, this approach appears robust and precise.

Hemin as electrochemically regenerable co-reaction accelerator for construction of an ultrasensitive PTCA-based electrochemiluminescent aptasensor

In this work, hemin was firstly used as electrochemically regenerable co-reaction accelerator for signal amplification to develop an ultrasensitive aptasensor for Aflatoxin M1 (AFM1) detection. Initially, the perylenetetracarboxylic acid (PTCA) was directly employed as luminophore to construct the ECL sensing nano-platform by combining Au nanoparticles (Au NPs) for immobilizing thiol-terminated hairpin probe (H1). Then with the help of hairpin H2, H3, the AFM1-catalyzed hairpin assembly (CHA) was executed to produce the H1-H3 duplex, which could further initiate the hybridization chain reaction (HCR) to generate dendritic DNA polymers consisting of G-rich sequence for capturing large quantities of hemin on the electrode surface. Herein, hemin as electrochemically regenerable co-reaction accelerator could interact with the co-reactant (S₂O₈^2-) to obviously improve the luminous efficiency of the PTCA. Therefore, a strong and stable ECL signal was achieved by the employment of hemin as electrochemically regenerable co-reaction accelerator. The proposed aptasensor determined AFM1 down to 0.09pgmL^-1 within a linear range of 0.4pgmL^-1 to 400ngmL^-1. With excellent sensitivity and stability, the strategy provided an efficient and simple method for the trace detection of biomolecules in clinical analysis.

Development and validation of an electrochemiluminescent ELISA for quantitation of oral insulin tregopil in diabetes mellitus serum

AIM

Tregopil, a novel PEGylated human insulin is in clinical development for oral delivery in diabetes treatment. The aim of the study was to develop and validate a sensitive and specific ELISA method for quantitating Tregopil in diabetes subjects on basal Glargine, since most commercially available insulin kits either do not detect Tregopil or show significant reactivity to Glargine.

METHODS

An electrochemiluminescent ELISA was developed and validated for Tregopil quantitation in diabetes serum.

RESULTS

The method has a LLOQ of 0.25 ng/ml, shows minimum cross-reactivity to Glargine and was successfully tested using a subset of samples from Tregopil-dosed Type 1 diabetes mellitus patients.

CONCLUSION

The ELISA method is sensitive and can be used to support accurate measurement of Tregopil with no cross-reactivity to Glargine and its metabolites in clinical studies.

PAMAM dendrimers: A multifunctional nanomaterial for ECL biosensors

Polyamido amine (PAMAM) dendrimers have been shown to function as electrochemiluminescence (ECL) co-reactant and have the inherent capability of improving immobilization of molecules on surfaces due to their dendritic structure. Here, we investigated the combination of both of these properties as the basis for biosensor development. Dendrimers with 5, 8, 10 and 16 terminal amine groups, respectively, were used. These were covalently coupled to biotin as model recognition site, and tagged with Ru(bpy)₃²⁺ via adsorption. Due to their hydrophilicity, Ru-dendrimers showed significantly improved electrochemical activity in comparison to the standard tripropylamine (TPA) assisted ECL and similar luminescence yields even though 10 fold less dendrimer concentration was required in comparison to TPA. Best signals were obtained for D8 and D10 dendrimers. These Ru-dendrimers were subsequently used for the quantification of streptavidin, as its binding to the biotin-tag caused a proportional decrease in ECL signal with a dynamic range of 5nM to 1μM. These preliminary studies demonstrate that PAMAM dendrimers can function as responsive signal generators in solution-based ECL-bioassays with an assumed even higher impact when being immobilized directly on the electrode-surface.

Electrogenerated chemiluminescence induced by sequential hot electron and hole injection into aqueous electrolyte solution

Hole injection into aqueous electrolyte solution is proposed to occur when oxide-coated aluminum electrode is anodically pulse-polarized by a voltage pulse train containing sufficiently high-voltage anodic pulses. The effects of anodic pulses are studied by using an aromatic Tb(III) chelate as a probe known to produce intensive hot electron-induced electrochemiluminescence (HECL) with plain cathodic pulses and preoxidized electrodes. The presently studied system allows injection of hot electrons and holes successively into aqueous electrolyte solutions and can be utilized in detecting electrochemiluminescent labels in fully aqueous solutions, and actually, the system is suggested to be quite close to a pulse radiolysis system providing hydrated electrons and hydroxyl radicals as the primary radicals in aqueous solution without the problems and hazards of ionizing radiation. The analytical power of the present excitation waveforms are that they allow detection of electrochemiluminescent labels at very low detection limits in bioaffinity assays such as in immunoassays or DNA probe assays. The two important properties of the present waveforms are: (i) they provide in situ oxidation of the electrode surface resulting in the desired oxide film thickness and (ii) they can provide one-electron oxidants for the system by hole injection either via F- and F(+)-center band of the oxide or by direct hole injection to valence band of water at highly anodic pulse amplitudes.

Electrochemiluminescent detection of methamphetamine and amphetamine

Direct detection of amphetamine type stimulants (ATSs) including methylamphetamine (MA) in street samples and biological matrices without the need for pretreatment or extraction is a great challenge for forensic drug analysis. Electrochemical techniques, such as electrochemiluminescence (ECL), are promising tools for this area of analysis. This contribution focuses on the electrochemical and photochemical properties of [Ru(bpy)3](2+) Nafion composite films and their subsequent use for the detection of ATS in particular MA. Under optimised conditions, the response linearly increased with the concentration over the concentration range 50pM≤[MA]≤1mM while an equivalent dynamic range was obtained for amphetamine with a correlation coefficient of 0.9903 and 0.9948 respectively. The ECL signal was monitored at ∼620nm, representing the λmax for the [Ru(bpy)3](2+) Nafion composite films. This wavelength is shifted by approximately 15nm compared to the photoexcited λmax for the same system. The modified films were formed by direct interaction with the electrode surface without the need for surface modification or chain linkers. This is a major advantage for the fabrication of any sensor as it reduces the synthesis times resulting in more economically and cheaper production costs. This technique is simple, rapid, selective and sensitive, and shows potential for the high-throughput quantitation of ATS as well as possibilities for adaptation with other techniques such as FIA or LC systems.

Bi-functionalized aptasensor for ultrasensitive detection of thrombin

A novel bi-functionalized aptasensor for thrombin detection was fabricated by using electrochemiluminescence (ECL) and electrochemical impedance spectroscopy (EIS) techniques. A thiol-terminated aptamer with 15 oligonucleotides was hybridized with its complementary oligonucleotides to form a double-stranded DNA (dsDNA). Then, the thiol-labeled dsDNA was assembled on a Au electrode via Au-S bond; the other distal of the dsDNA labeled with biotin was bound to QDs through a biotin-avidin conjugation. When thrombin is present in the detection solution, the aptamer can combine with thrombin, resulting in loss of CdSe QDs from the electrode surface and thereby decreasing the ECL intensity and increasing the impedance. The decreased ECL and increased EIS signals are logarithmically linear with respect to the concentration of thrombin. The linear range was 10(-10)-10(-3) μg mL(-1) (R=0.9924) for the ECL signal and 10(-10)-10(-1) μg mL(-1) (R=0.9875) for the EIS method with a common detection limit of 10(-10) μg mL(-1) (2.7 aM). In addition, the bi-functionalized aptasensor exhibited excellent selectivity, super sensitivity, a low detection limit and a wide linear range.

Monte Carlo loop refinement and virtual screening of the thyroid-stimulating hormone receptor transmembrane domain

Metropolis Monte Carlo (MMC) loop refinement has been performed on the three extracellular loops (ECLs) of rhodopsin and opsin-based homology models of the thyroid-stimulating hormone receptor transmembrane domain, a class A type G protein-coupled receptor. The Monte Carlo sampling technique, employing torsion angles of amino acid side chains and local moves for the six consecutive backbone torsion angles, has previously reproduced the conformation of several loops with known crystal structures with accuracy consistently less than 2 Å. A grid-based potential map, which includes van der Waals, electrostatics, hydrophobic as well as hydrogen-bond potentials for bulk protein environment and the solvation effect, has been used to significantly reduce the computational cost of energy evaluation. A modified sigmoidal distance-dependent dielectric function has been implemented in conjunction with the desolvation and hydrogen-bonding terms. A long high-temperature simulation with 2 kcal/mol repulsion potential resulted in extensive sampling of the conformational space. The slow annealing leading to the low-energy structures predicted secondary structure by the MMC technique. Molecular docking with the reported agonist reproduced the binding site within 1.5 Å. Virtual screening performed on the three lowest structures showed that the ligand-binding mode in the inter-helical region is dependent on the ECL conformations.

MicroRNA-101 inhibits human hepatocellular carcinoma progression through EZH2 downregulation and increased cytostatic drug sensitivity

BACKGROUND & AIMS

Oncogene polycomb group protein enhancer of zeste homolog 2 (EZH2) has been proposed to be a target gene of putative tumor suppressor microRNA-101 (miR-101). The aim of our study was to investigate the functional role of both miR-101 and EZH2 in human hepatocellular carcinoma (HCC).

METHODS

MiR-101 and EZH2 expressions were evaluated in tumor tissues of 99 HCC patients and 7 liver cancer cell lines by real-time PCR. Luciferase reporter assay was employed to validate whether EZH2 represents a target gene of miR-101. The effect of miR-101 on HCC growth as well as programmed cell death was studied in vitro and in vivo.

RESULTS

MiR-101 expression was significantly downregulated in most of HCC tissues and all cell lines, whereas EZH2 was significantly overexpressed in most of HCC tissues and all cell lines. There was a negative correlation between expression levels of miR-101 and EZH2. Luciferase assay results confirmed EZH2 as a direct target gene of miR-101, which negatively regulates EZH2 expression in HCC. Ectopic overexpression of miR-101 dramatically repressed proliferation, invasion, colony formation as well as cell cycle progression in vitro and suppressed tumorigenicity in vivo. Furthermore, miR-101 inhibited autophagy and synergized with either doxorubicin or fluorouracil to induce apoptosis in tumor cells.

CONCLUSION

Tumor suppressor miR-101 represses HCC progression through directly targeting EZH2 oncogene and sensitizes liver cancer cells to chemotherapeutic treatment. Our findings provide significant insights into molecular mechanisms of hepatocarcinogenesis and may have clinical relevance for the development of novel targeted therapies for HCC.

Combination use of ferulic acid, ligustrazine and tetrahydropalmatine inhibits the growth of ectopic endometrial tissue: a multi-target therapy for endometriosis rats

ETHNOPHARMACOLOGICAL RELEVANCE

Ferulic acid (FA), ligustrazine (LZ) and tetrahydropalmatine (THP) are separately isolated from Chinese Angelica, Szechwan Lovage Rhizome and Rhizoma in the Jiawei-Foshou-San formula, a popular traditional Chinese medicine for irregular menses. It has been reported that the combination use of FA+LZ+THP has similar effect on endometriosis, but the underlying mechanisms are unclear. This study was to investigate the combination effects and mechanisms of FA+LZ+THP on endometriosis rats.

MATERIALS AND METHODS

Fifty endometriosis rats were intragastricly treated with FA+LZ+THP for 4 wk. The volume of ectopic endometrial tissue was measured to evaluate the effects. Then the changes in hypothalamic-pituitary-ovarian axis and ERE pathway were indicated by the levels of E2, GnRH, FSH and LH, and the expressions of ER, HSP90 and COX-2, respectively. In addition, peritoneal macrophages of each rat were cultured in vitro and treated with (FA+LZ+THP)-medicated serum for 24h. The proliferation and phagocytosis abilities, the levels of IL-1β and TNF-α, and the expression of IκBα were then measured for the changes of peritoneal macrophage activities.

RESULTS

Combination use of FA+LZ+THP diminished the volume of the ectopic endometrial tissues (P<0.05 or P<0.01). It also decreased the E2 level, suppressed the expression of GnRH, FSH and LH, and decreased the protein expression of ER, HSP90 and COX-2 (all P<0.05 or P<0.01). The phagocytosis ability of peritoneal macrophage was enhanced by (FA+LZ+THP)-medicated serum (P<0.05) with no change of proliferation (P>0.05). Moreover, IL-1β and TNF-α were downregulated (both P<0.05 or P<0.01) and IκBα was upregulated by the (FA+LZ+THP)-medicated serum (P<0.01).

CONCLUSIONS

The combination use of FA, LZ and THP could inhibit the growth of ectopic endometrial tissue in endometriosis rats. It might be related to the down-regulation of hypothalamic-pituitary-ovarian axis, the amelioration in ERE pathway and the improvement of peritoneal macrophage activities.

Bisphenol A promotes dendritic morphogenesis of hippocampal neurons through estrogen receptor-mediated ERK1/2 signal pathway

Bisphenol A (BPA), an environmental endocrine disruptor, has attracted increasing attention to its adverse effects on brain developmental process. The previous study indicated that BPA rapidly increased motility and density of dendritic filopodia and enhanced the phosphorylation of N-methyl-d-aspartate (NMDA) receptor subunit NR2B in cultured hippocampal neurons within 30min. The purpose of the present study was further to investigate the effects of BPA for 24h on dendritic morphogenesis and the underlying mechanisms. After cultured for 5d in vitro, the hippocampal neurons from 24h-old rat were infected by AdV-EGFP to indicate time-lapse imaging of living neurons. The results demonstrated that the exposure of the cultured hippocampal neurons to BPA (10, 100nM) or 17β-estradiol (17β-E2, 10nM) for 24h significantly promoted dendritic development, as evidenced by the increased total length of dendrite and the enhanced motility and density of dendritic filopodia. However, these changes were suppressed by an ERs antagonist, ICI182,780, a non-competitive NMDA receptor antagonist, MK-801, and a mitogen-activated ERK1/2-activating kinase (MEK1/2) inhibitor, U0126. Meanwhile, the increased F-actin (filamentous actin) induced by BPA (100nM) was also completely eliminated by these blockers. Furthermore, the result of western blot analyses showed that, the exposure of the cultures to BPA or 17β-E2 for 24h promoted the expression of Rac1/Cdc42 but inhibited that of RhoA, suggesting Rac1 (Ras related C3 botulinum toxinsubstrate 1)/Cdc42 (cell divisioncycle 42) and RhoA (Ras homologous A), the Rho family of small GTPases, were involved in BPA- or 17β-E2-induced changes in the dendritic morphogenesis of neurons. These BPA- or 17β-E2-induced effects were completely blocked by ICI182,780, and were partially suppressed by U0126. These results reveal that, similar to 17β-E2, BPA exerts its effects on dendritic morphogenesis by eliciting both nuclear actions and extranuclear-initiated actions that are integrated to influence the development of dendrite in hippocampal neurons.

A new assay for fast, reliable CRIM status determination in infantile-onset Pompe disease

Pompe disease is caused by a deficiency of acid α-glucosidase (GAA; EC, 3.2.1.20), and the infantile-onset form is rapidly fatal if left untreated. However, recombinant human GAA (rhGAA) enzyme replacement therapy (ERT) extends survival for infantile Pompe patients. Although cross-reactive immunologic material (CRIM)-negative patients, who lack detectable endogenous GAA, mount an immune response to rhGAA that renders the therapy ineffective, timely induction of immune tolerance in these patients may improve clinical outcomes. Previously, CRIM status has been determined by Western blot analysis in cultured skin fibroblasts, a process that can take a few weeks. We present a blood-based CRIM assay that can yield results within 48 to 72 h. Results from this assay have been confirmed by GAA Western blot analysis in fibroblasts or by GAA sequencing in a small number of Pompe disease patients. Rapid classification of CRIM status will assist in identifying the most effective treatment course and minimizing treatment delays in patients with infantile-onset Pompe disease.

MiR-7-1 potentiated estrogen receptor agonists for functional neuroprotection in VSC4.1 motoneurons

Protection of motoneurons is an important goal in the treatment of spinal cord injury (SCI). We tested whether neuroprotective microRNAs (miRs) like miR-206, miR-17, miR-21, miR-7-1, and miR-106a could enhance efficacy of estrogen receptor (ER) agonists such as 1,3,5-tris (4-hydroxyphenyl)-4-propyl-1H-pyrazole (PPT, ERα agonist), Way200070 (WAY, ERβ agonist), and estrogen (EST, ERα and ERβ agonist) in preventing apoptosis in the calcium ionophore (CI)-insulted ventral spinal cord 4.1 (VSC4.1) motoneurons. We determined that 200 nM CI induced 70% cell death. Treatment with 50 nM PPT, 100 nM WAY, and 150 nM EST induced overexpression of ERα, ERβ, and both receptors, respectively, at mRNA and protein levels. Treatment with ER agonists significantly upregulated miR-206, miR-17, and miR-7-1 in the CI-insulted VSC4.1 motoneurons. Transfection with miR-206, miR-17, or miR-7-1 mimic potentiated WAY or EST to inhibit apoptosis in the CI-insulted VSC4.1 motoneurons. Overexpression of miR-7-1 maximally increased efficacy of WAY and EST for down regulation of pro-apoptotic Bax and upregulation of anti-apoptotic Bcl-2. A search using microRNA database (miRDB) indicated that miR-7-1 could inhibit the expression of L-type Ca(2+) channel protein alpha 1C (CPα1C). miR-7-1 overexpression and WAY or EST treatment down regulated CPα1C but upregulated p-Akt to trigger cell survival signaling. The same therapeutic strategy increased expression of the Ca(2+)/calmodulin-dependent protein kinase II beta (CaMKIIβ) and the phosphorylated cAMP response element binding protein (p-CREB) so as to promote Bcl-2 transcription. Whole cell membrane potential and mitochondrial membrane potential studies indicated that miR-7-1 highly potentiated EST to preserve functionality in the CI-insulted VSC4.1 motoneurons. In conclusion, our data indicated that miR-7-1 most significantly potentiated efficacy of EST for functional neuroprotection and this therapeutic strategy could be used in the future to attenuate apoptosis of motoneurons in SCI.

Osteoblastic cell secretome: a novel role for progranulin during risedronate treatment

It is well established that osteoblasts, the key cells involved in bone formation during development and in adult life, secrete a number of glycoproteins harboring autocrine and paracrine functions. Thus, investigating the osteoblastic secretome could yield important information for the pathophysiology of bone. In the present study, we characterized for the first time the secretome of human Hobit osteoblastic cells. We discovered that the secretome comprised 89 protein species including the powerful growth factor progranulin. Recombinant human progranulin (6nM) induced phosphorylation of mitogen-activated protein kinase in both Hobit and osteocytic cells and induced cell proliferation and survival. Notably, risedronate, a nitrogen-containing bisphosphonate widely used in the treatment of osteoporosis, induced the expression and secretion of progranulin in the Hobit secretome. In addition, our proteomic study of the Hobit secretome revealed that risedronate induced the expression of ERp57, HSP60 and HSC70, three proteins already shown to be associated with the prevention of bone loss in osteoporosis. Collectively, our findings unveil novel targets of risedronate-evoked biological effects on osteoblast-like cells and further our understanding of the mechanisms of action of this currently used compound.

Effect of methionine sulfoxide reductase B1 (SelR) gene silencing on peroxynitrite-induced F-actin disruption in human lens epithelial cells

F-actin plays a crucial role in fundamental cellular processes, and is extremely susceptible to peroxynitrite attack due to the high abundance of tyrosine in the peptide. Methionine sulfoxide reductase (Msr) B1 is a selenium-dependent enzyme (selenoprotein R) that may act as a reactive oxygen species (ROS) scavenger. However, its function in coping with reactive nitrogen species (RNS)-mediated stress and the physiological significance remain unclear. Thus, the present study was conducted to elucidate the role and mechanism of MsrB1 in protecting human lens epithelial (hLE) cells against peroxynitrite-induced F-actin disruption. While exposure to high concentrations of peroxynitrite and gene silencing of MsrB1 by siRNA alone caused disassembly of F-actin via inactivation of extracellular signal-regulated kinase (ERK) in hLE cells, the latter substantially aggravated the disassembly of F-actin triggered by the former. This aggravation concurred with elevated nitration of F-actin and inactivation of ERK compared with that induced by the peroxynitrite treatment alone. In conclusion, MsrB1 protected hLE cells against the peroxynitrite-induced F-actin disruption, and the protection was mediated by inhibiting the resultant nitration of F-actin and inactivation of ERKs.

Expression of the 78 kD glucose-regulated protein is induced by endoplasmic reticulum stress in the development of hepatopulmonary syndrome

OBJECTIVE

This study is to explore the role of 78 kD glucose-regulated protein (GRP78) in the development of hepatopulmonary syndrome (HPS) in rats.

METHODS

The rat model of liver cirrhosis and HPS were induced with multiple pathogenic factors. Hematoxylin and eosin (H & E) staining was performed to detect the pathological changes of the lung and liver tissues. The levels of alanine transferase (ALT), endotoxin, and tumor necrosis factor-α (TNF-α) in plasma and TNF-α and malondialdehyde (MDA) in lung tissues were detected. RT-PCR and Western blotting were conducted to detect the mRNA and protein expression levels of GRP78 in lungs.

RESULTS

The plasma endotoxin level was gradually increased as HPS developed, and the mRNA and protein expression levels of GRP78 in lungs were also increased as the disease progressed. The levels of ALT and TNF-α in plasma and the contents of TNF-α and MDA in lung tissues were gradually increased along with the disease progression, with a strong positive correlation. Compared with controls, the plasma TNF-α level and the mRNA and protein expression levels of GRP78 in lung tissues were significantly higher in rats with HPS. The levels of endotoxin and ALT in plasma and the level of MDA in lungs were significantly higher in rats with HPS than controls.

CONCLUSIONS

The increased GRP78 expression is indicative of endoplasmic reticulum stress response during HPS, which may play an important role in the disease pathogenesis.

MicroRNA-106b induces mitochondrial dysfunction and insulin resistance in C2C12 myotubes by targeting mitofusin-2

MicroRNA-106b (miR-106b) is reported to correlate closely with skeletal muscle insulin resistance and type 2 diabetes. The aim of this study was to identify an mRNA targeted by miR-106b which regulates skeletal muscle insulin sensitivity. MiR-106b was found to target the 3' untranslated region (3' UTR) of mitofusin-2 (Mfn2) through miR-106b binding sites and to downregulate Mfn2 protein abundance at the post-transcriptional level by luciferase activity assay combined with mutational analysis and immunoblotting. Overexpression of miR-106b resulted in mitochondrial dysfunction and insulin resistance in C2C12 myotubes. MiR-106b was increased in insulin-resistant cultured C2C12 myotubes induced by TNF-α, and accompanied by increasing Mfn2 level, miR-106b loss of function improved mitochondrial function and insulin sensitivity impaired by TNF-α in C2C12 myotubes. In addition, both overexpression and downregulation of miR-106b upregulated peroxisome proliferator-activated receptor gamma coactivator (PGC)-1α and estrogen-related receptor (ERR)-α expression. MiR-106b targeted Mfn2 and regulated skeletal muscle mitochondrial function and insulin sensitivity. Therefor, Inhibition of miR-106b may be a potential new strategy for treating insulin resistance and type 2 diabetes.

A functional link between heme oxygenase-1 and tristetraprolin in the anti-inflammatory effects of nicotine

Nicotine stimulates the cholinergic anti-inflammatory pathway and prevents excessive inflammation by inhibiting the release of inflammatory cytokines from macrophages. We have previously reported that heme oxygenase-1 (HO-1) and tristetraprolin (TTP) are induced by nicotine and mediate the anti-inflammatory function of nicotine in macrophages. However, it was not clear whether the two molecules are functionally linked. In this study, we sought to determine whether HO-1 associates with TTP to mediate the anti-inflammatory effects of nicotine. Inhibition of HO-1 activity or HO-1 expression attenuated the effects of nicotine on STAT3 activation, TTP induction, and TNF-α production in LPS-treated macrophages. Induction of HO-1 expression increased the level of TTP in the absence of nicotine. In an LPS-induced endotoxemia model, HO-1 deficiency blocked the effects of nicotine on the STAT3 phosphorylation, TTP induction, and LPS-induced TNF-α production in the liver. Downregulation of STAT3 by siRNA attenuated the effect of nicotine on TTP expression and TNF-α production but did not affect the nicotine-mediated induction of HO-1. In TTP knockout mice, nicotine treatment enhanced HO-1 expression and STAT3 activation but failed to inhibit LPS-induced TNF-α production. Our results suggest that HO-1 and TTP are functionally linked in mediating the anti-inflammatory effects of nicotine; HO-1 is necessary for the induction of TTP by nicotine. This novel nicotine-HO-1-TTP signaling pathway provides new possibilities for the treatment of inflammatory diseases.

Mechanism of protein decarbonylation

Ligand/receptor stimulation of cells promotes protein carbonylation that is followed by the decarbonylation process, which might involve thiol-dependent reduction (C.M. Wong et al., Circ. Res. 102:301-318; 2008). This study further investigated the properties of this protein decarbonylation mechanism. We found that the thiol-mediated reduction of protein carbonyls is dependent on heat-labile biologic components. Cysteine and glutathione were efficient substrates for decarbonylation. Thiols decreased the protein carbonyl content, as detected by 2,4-dinitrophenylhydrazine, but not the levels of malondialdehyde or 4-hydroxynonenal protein adducts. Mass spectrometry identified proteins that undergo thiol-dependent decarbonylation, which include peroxiredoxins. Peroxiredoxin-2 and -6 were carbonylated and subsequently decarbonylated in response to the ligand/receptor stimulation of cells. siRNA knockdown of glutaredoxin inhibited the decarbonylation of peroxiredoxin. These results strengthen the concept that thiol-dependent decarbonylation defines the kinetics of protein carbonylation signaling.

Alpha-synuclein interferes with cAMP/PKA-dependent upregulation of dopamine β-hydroxylase and is associated with abnormal adaptive responses to immobilization stress

Parkinson's disease (PD) is clinically characterized not only by motor symptoms but also by non-motor symptoms, such as anxiety and mood changes. Based on our previous study showing that overexpression of wild-type or mutant α-synuclein (α-SYN) interferes with cAMP/PKA-dependent transcriptional activation in norepinephrine (NE)-producing cells, the effect of wild-type and mutant α-SYN on cAMP response element (CRE)-mediated regulation of the NE-synthesizing enzyme dopamine β-hydroxylase (DBH) was evaluated in this study. Overexpression of wild-type or mutant α-SYN interfered with CRE-mediated regulation of DBH transcription in NE-producing SK-N-BE(2) cells. Upon entering the nucleus, α-SYN interacted with the DBH promoter region encompassing the CRE, which interfered with forskolin-induced CREB binding to the CRE region. Interestingly, mutant A53T α-SYN showed much higher tendency to nuclear translocation and interaction with the DBH promoter region encompassing the CRE than wild type. In addition, A53T α-SYN expressing transgenic mice exhibited increased anxiety-like behaviors under normal conditions and abnormal regulation of DBH expression in response to immobilization stress with abnormal adaptive responses. These data provide an insight into the physiological function of α-SYN in NErgic neuronal cells, which further indicates that the α-SYN mutation may play a causative role in the generation of non-motor symptoms in PD.

Saikosaponin A of Bupleurum chinense (Chaihu) elevates bone morphogenetic protein 4 (BMP-4) during hepatic stellate cell activation

BACKGROUND

Saikosaponin a (SSa) is a compound extracted from a Chinese herb which has been widely used in treating liver diseases such as liver fibrosis. However, the mechanism of SSa in treatment of liver fibrosis still remain unclear. Our previous study demonstrated that BMP4 stimulated the expression of smooth muscle alpha actin (α-SMA) in the liver. Therefore, the current study investigates the effect of SSa on BMP4 expression during hepatic stellate cell activation in a human hepatic stellate cell line.

METHODS

LX-2 cells were cultured in DMEM/F12 with fetal bovine serum and treated with SSa in different times and concentrations. The expression of BMP4 was examined by both RT-PCR and western blot analysis. WST-1 proliferation reagent was used to evaluate cell proliferation. α-SMA and Bax protein expression was determined by western blot analysis.

RESULTS

Both mRNA and protein levels of BMP-4 were significantly inhibited in LX-2 cells after 5 μM SSa treatment. SSa significantly inhibited LX-2 proliferation at the concentration of 5μM while BMP-4 had no effect on LX-2 proliferation. BMP-4 increased α-SMA expression in LX-2 while SSa reduced α-SMA expression. In addition SSa could neutralize the effect of BMP-4 on α-SMA expression. SSd also inhibited BMP4 expression but not NG. Bax protein expression was induced in these cells by 5 μM SSa.

CONCLUSION

SSa could down-regulate BMP-4 expression and inhibit hepatic stellate cell activation. Therefore, SSa could be used for treatment of liver disease with elevated BMP-4 expression.