Dual Signal Detection Research Articles

Dual signal AA detection based on fluorescence and local surface plasmon resonance absorption technology

The core/shell Au@MnO2 nanoparticles (Au@MnO2 NPs) were prepared and characterized by UV–vis spectrum, transmission electron microscopy (TEM) and X-ray photoelectron spectrum (XPS). It was found that MnO2 in the shell of Au@MnO2 NPs could oxidize thiamine (VB1) into blue fluorescent thiochrome (TC). The reduction of MnO2 in the shell layer could lead to a decrease of Au@MnO2 NPs size along with a blue shift of the localized surface plasmon resonance (LSPR) peak. Once ascorbic acid (AA) was introduced, MnO2 in the shell was rapidly reduced to Mn2+ ions. Accordingly, the oxidation of VB1 was inhibited and the fluorescence of TC was weakened. Based on these phenomena, we have established a dual signal method for AA determination with the help of UV–vis and fluorescence spectrophotometer. Under the optimum conditions, the LSPR absorption peak shift (Δλ) of Au@MnO2 NPs and the decrease in fluorescence of TC correlated well with AA concentration ranging from 0.75 to 17.5 μM. The detection limits of LSPR absorption assay and fluorescence assay were 0.18 and 0.47 μM, respectively. More importantly, this dual-signal detection method has been used for the determination of AA in vitamin C tablets with high accuracy and precision, indicating its promising potential applications.

Polydopamine-coated two-dimensional nanomaterials as high-affinity photothermal signal tag towards dual-signal detection of Salmonella typhimurium by lateral flow immunoassay

Lateral flow immunoassay (LFIA) with gold nanoparticles (AuNPs) as signal reporters has been extensively utilized for the rapid detection of foodborne pathogens. Nevertheless, it’s challenging for LFIA to obtain sensitive detection, because of the inefficient coupling of AuNPs and antibodies and the poor colorimetric signals. To improve on this, we used a two-dimensional nanomaterial (Cu2MoS4) modified with PDA (CMS@PDA) that provides superior bio-affinity and excellent photothermal signal qualities. With the CMS@PDA material, we successfully constructed a portable LFIA device for specific detection of Salmonella typhimurium (S. typhimurium) using a dual-signal probe that combines colorimetric and photothermal signals (CM/PT). The dynamic detection range of the CMS@PDA-LFIA is 103 to 107 cfu mL−1. Notably, the detection limit of 103 cfu mL−1 is 100 times more sensitive compared to AuNPs-based LFIA. Moreover, the assay exhibits satisfactory recovery rates for S. typhimurium detection in food samples. In this research, the coating of PDA solves the problem of low water-solubility of CMS, making the proposed CMS@PDA nanocomposite showcase better performance in the CM/PT mode detection by LFIA. Beyond all doubt, this work offers a novel supplement for applying multifunctional two-dimensional nanomaterials in LFIAs.

Target-Induced AIE Effect Coupled with CRISPR/Cas12a System Dual-Signal Biosensing for the Ultrasensitive Detection of Gliotoxin.

Here, a novel rapid and ultrasensitive aptamer biosensor was designed for target-induced activation of AIE effect and followed by the activation of Crispr Cas12a (LbCpf1)-mediated cleavage to achieve dual-signal detection. The prepared DNA building blocks contain the target aptamer, ssDNA-Fc, and Activator1. In this system, the activation mode was divided into two steps. First, when the target interacts with the aptamers, the DNA building blocks would be disintegrated rapidly, releasing a mass of Ac1, generating ETTC-dsDNA aggregated to produce a fluorescence signal by the AIE effect. Second, with the release of Ac2, LbCpf1-crRNA was activated, which greatly improves the ssDNA-Fc cleavage efficiency to render signal amplification and ultrasensitive detection of the target. Satisfactorily, using this approach to detect gliotoxin, optimal conditions for detection was achieved for reducing the detection time to 55 min, achieving a low detection limit of 2.4 fM and a satisfactory linear in the range of 50 fM to 1 nM, which addressed the shortcoming of a weak electrochemical signal in previous sensors. The water-insoluble AIE material was coupled with DNA to obtain water-soluble ETTC-dsDNA and successfully introduced into the sensor system, with a low detection limit of 5.6 fM. Subsequently, the biosensor combined with handheld electrochemical workstation was successfully applied in the detection of gliotoxin in five actual samples, with a detection range of 32.0 to 2.09 × 108 pM. This strategy not only provides a novel and effective detection platform for mycotoxins in complex food matrices but also opens a promising avenue for various molecules detection in imaging and disease diagnosis.

Dual-signal electrochemical immunosensor based on the water electrolysis signals of (NiFeCo)2P@Au/CeO2 nanocomposites: Application for prostate-specific antigen detection

Sensitive and accurate detection of prostate-specific antigen (PSA) is great importance for the diagnosis and treatment of prostate cancer. However, constructing an electrochemical immunosensor with dual-signal detection can significantly improve the sensitivity and accuracy of PSA detection. Therefore, we prepared an electrolytic water bifunctional catalyst (NiFeCo)2P@Au/CeO2 and used it as an electrocatalytic label to construct a dual-signal electrochemical immunosensor. Based on the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) signals of (NiFeCo)2P@Au/CeO2, the electrochemical immunosensor can achieve dual-signal detection of PSA. Research has shown that the dual-signal electrochemical immunosensor not only has a wide detection linear range (0.0001–100 ng mL−1), but also has extremely low detection limits (HER signal: 116.86 fg mL−1 and OER signal: 39.05 fg mL−1). In addition, it was used for PSA detection in human serum samples with good recovery. This dual-signal electrochemical immunosensor provides a new detection method for PSA and also develops a new dual-signal detection strategy for electrochemical immunosensor.

Colorimetric and electrochemical dual-signal detection of uracil-DNA glycosylase using functionalized pure DNA hydrogel on paper-based analytical devices

The development of simple and accurate detection of uracil-DNA glycosylase (UDG) is of great significance for early clinical diagnosis and biomedical research. Here, we on the first effort introduced the uracil bases into the rolling circle amplification (RCA) reaction to produce the functionalized pure DNA hydrogel (PDH) for UDG detection. During RCA process, methylene blue (MB) molecules as the indicators were encapsulated into PDH. The addition of UDG can remove the uracil bases of PDH to generate abasic sites, which are further cleaved with the assistance of apurinic/apyrimidinic endonuclease (APE), thus resulting in the dissociation of PDH to release blue MB. By combining with the paper analytical devices as the signal readout platform, a colorimetric and electrochemical dual-signal biosensor was constructed for convenient and accurate detection of UDG. The proposed MB@PDH-based dual-signal sensing system exhibited good selectivity and high sensitivity with a detection limit of 6.4 × 10−4 U/mL (electrochemical method). It was also demonstrated that this sensing system showed excellent performance in UDG inhibitor screening, thus providing great potential in UDG-related disease diagnosis and drug discovery.

A multifunctional polyacrylamide/chitosan hydrogel for dyes adsorption and metal ions detection in water

Removing noxious dyes and detecting excessive metal ions in water are both effective means to prevent damage from contaminants and ensure water safety. The emphasis problems were addressed by preparation a polyacrylamide chitosan (PAAM/CS) hydrogel. Polyacrylamide (PAAM) provides overall mechanical strength to carry loads and facilitate circulation, chitosan (CS) provides adsorption positions with high adsorption capacity. Which made that PAMM/CS hydrogel efficiently performed sorption of xylenol orange (XO). As the functional dye, XO binds to PAAM/CS and confers colorimetric properties on PAAM/CS hydrogels. XO sorbed hydrogel realized fluorescence dual-signal detection of Fe3+ and Al3+ in water. The significant swelling and adsorption potency of the hydrogel, combined with the dual-signal detection capability of XO sorbed hydrogel, make this hydrogel a versatile material for environmental applications.

A gold nanoflower based dual mode aptasensor for aflatoxin B1 detection using SERS and fluorescence effect simultaneously

Aflatoxin B1 (AFB1) is usually the major aflatoxin produced by toxigenic strains and has been identified the most potent natural carcinogen. Here, a SERS/fluorescence dual-mode nanosensor has been designed while gold nanoflowers (AuNFs) was used as substrate for the detection of AFB1. AuNFs exhibited excellent SERS enhancement effect as well as the good fluorescence quenching effect which made the dual signal detection possible. First, the surface of AuNFs was modified with AFB1 aptamer via Au-SH group. Then, the complementary sequence functionalized with Cy5 (the signal molecule) was attached to AuNFs based on the base complementary pairing principle. On this case, Cy5 was close to AuNFs, the SERS intensity was greatly enhanced and the fluorescence intensity was quenched. After incubation with AFB1, the aptamer was preferentially combined to its target AFB1. Thus, the complementary sequence detached from AuNFs which caused the SERS intensity of Cy5 decreased while its fluorescence effect recovered. Then, the quantitative detection was realized with two optical properties. The LOD was calculated to be 0.03 ng/mL. It was a convenient and fast detection method which expanded the application of nanomaterials based multi-signal simultaneous detection.

Fe Single-Atom Nanozymes for Real-Time Dual Monitoring of H2O2 Released from Living Cells

Excessive accumulation of hydrogen peroxide (H2O2) in the physiological pool can cause oxidative stress of cells and eventually lead to the occurrence of diseases. Therefore, accurate and real-time detection of H2O2 is of great significance for disease detection and prevention. In this study, an Fe single-atom nanozyme (Fe-SNC) with an Fe-N4 active center was synthesized, which showed excellent peroxidase-like activity in an acidic environment and amazing electrocatalytic activity in H2O2 reduction reaction. Based on this, we proposed a colorimetric and electrochemical dual-signal detection strategy to real-time monitor H2O2 secreted by living cells. Compared with single-signal response mode, double-signal response mode has higher precision and sensitivity. The results show that the detection range of the colorimetric analysis method is 3–1000 μM and the detection limit is 1.3 μM. The detection range of the electrochemical analysis method is 1–8127 μM, and the detection limit is 0.61 μM. We believe that the dual-signal detection strategy based on Fe-SNC not only provides a way for the ultra-sensitive detection of hydrogen peroxide but also has a broad application prospect in clinical diagnosis.

Combining Upconversion Luminescence, Photothermy, and Electrochemistry for Highly Accurate Triple-Signal Detection of Hydrogen Sulfide by Optically Trapping Single Microbeads.

The detection of hydrogen sulfide (H2S), the third gas signaling molecule, is a promising strategy for identifying the occurrence of certain diseases. However, the conventional single- or dual-signal detection can introduce false-positive or false-negative results, which ultimately decreases the diagnostic accuracy. To address this limitation, we developed a luminescent, photothermal, and electrochemical triple-signal detection platform by optically trapping the synthetic highly doped upconversion coupled SiO2 microbeads coated with metal-organic frameworks H-UCNP-SiO2@HKUST-1 (H-USH) to detect the concentration of H2S. The H-USH was first synthesized and proved to have stable structure and excellent luminescent, photothermal, and electrochemical properties. Under 980 nm optical trapping and 808 nm irradiation, H-USH showed great detection linearity, a low limit of detection, and high specificity for H2S quantification via triple-signal detection. Moreover, H-USH was captured by optical tweezers to realize quantitative detection of H2S content in serum of acute pancreatitis and spontaneously hypertensive rats. Finally, by analyzing the receiver operating characteristic (ROC) curve, we concluded that triple-signal detection of H2S was more accurate than single- or dual-signal detection, which overcame the problem of false-negative/positive results in the detection of H2S in actual serum samples.

Novel Dual-Signal SiO2-COOH@MIPs Electrochemical Sensor for Highly Sensitive Detection of Chloramphenicol in Milk.

In view of the great threat of chloramphenicol (CAP) to human health and the fact that a few producers have illegally used CAP in the food production process to seek economic benefits in disregard of laws and regulations and consumer health, we urgently need a detection method with convenient operation, rapid response, and high sensitivity capabilities to detect CAP in food to ensure people's health. Herein, a molecularly imprinted polymer (MIP) electrochemical sensor based on a dual-signal strategy was designed for the highly sensitive analysis of CAP in milk. The NiFe Prussian blue analog (NiFe-PBA) and SnS2 nanoflowers were modified successively on the electrode surface to obtain dual signals from [Fe(CN)6]3-/4- at 0.2 V and NiFe-PBA at 0.5 V. SiO2-COOH@MIPs that could specifically recognize CAP were synthesized via thermal polymerization using carboxylated silica microspheres (SiO2-COOH) as carriers. When the CAP was adsorbed by SiO2-COOH@MIPs, the above two oxidation peak currents decreased at the same time, allowing the double-signal analysis. The SiO2-COOH@MIPs/SnS2/NiFe-PBA/GCE sensor used for determining CAP was successfully prepared. The sensor utilized the interactions of various nanomaterials to achieve high-sensitivity dual-signal detection, which had certain innovative significance. At the same time, the MIPs were synthesized using a surface molecular imprinting technology, which could omit the time of polymerization and elution and met the requirements for rapid detection. After optimizing the experimental conditions, the detection range of the sensor was 10-8 g/L-10-2 g/L and the limit of detection reached 3.3 × 10-9 g/L (S/N = 3). The sensor had satisfactory specificity, reproducibility, and stability, and was successfully applied to the detection of real milk samples.

Trimer structures formed by target-triggered AuNPs self-assembly inducing electromagnetic hot spots for SERS-fluorescence dual-signal detection of intracellular miRNAs

Accurate quantitative, in situ and temporal tracking imaging of tumor-associated miRNAs in living cells could provide a basis for cancer diagnosis and prognosis. In this strategy, a surface-enhanced Raman scattering (SERS)-fluorescence (FL) dual-spectral sensor (DSS) was constructed based on the nanoscale photophysical properties of AuNPs, mediated by functionalized DNA, to achieve rapid imaging of FL and accurate SERS quantification of intracellular miRNAs. The dual-spectrum sensor in the strategy is highly sensitive, specific and reproducibly stable. The LOD values of the dual spectra were 3.58 pM (SERS) as well as 11.8 pM (FL) with RSD values less than 2.69%. The bispectral sensor self-assembled into a trimer by the lapidation of Y-type DNA under the excitation of the target, generating a stable enhanced electric field coupling; and selected adenine located in the enhanced electric field as the reporter molecule, simplifying the labeling process and variables of the Raman reporter molecule, distinguishing it from other traditional methods. This strategy successfully achieved accurate tracking and quantification of miR-21 in cancer cells and showed good stability in the cells. The reported probes are potential tools for reliable monitoring of biomolecular dynamics in living cells.

Dual-binding domain electrochemiluminescence biosensing platform with self-checking function for sensitive detection of synthetic cathinone in e-cigarettes

Current single signal electrochemiluminescence (ECL) sensors are susceptible to false positive or false negative phenomena due to experimental conditions. Therefore, sensors with “self-checking” function are attracting democratic attention. In quick succession, a highly sensitive single-cathode dual ECL signal aptasensor with self-checking function to improve the shortcomings mentioned above was designed. This aptasensor used In-based metal-organic framework (MIL-68) as load and stabilizer to effectively attenuate the aggregation-induced quenching (ACQ) effect of porphyrin derivatives (Sn-TCPP) while improve ECL stability. The introduction of cooperative-binding split-aptamers” (CBSAs) aptamers increased the specificity of the aptasensor and its unique double-binding domains detection accelerated the detection efficiency. When analyzing 3,4-methylenedioxypyrovalerone (MDPV), we could calculate two concentrations based on the strength of ECL 1 and ECL 2. If the concentrations are the same, the result would be obtained; if not, it should be retested. Depending on the above operation, the results achieve self-check. It was found that the designed aptasensor could quantify the concentration of MDPV between 1.0 × 10−12 g/L and 1.0 × 10−6 g/L with the limit of detection (LOD) of 1.4 × 10−13 g/L and 2.0 × 10−13 g/L, respectively (3 σ/slope). This study not only improves the detection technology of MDPV, but also explores the dual-signal detection of porphyrin for the first time and enriches the definition of self-checking sensor.

Sensitive detection of organophosphorus pesticides based on the localized surface plasmon resonance and fluorescence dual-signal readout

In this work, a dual-signal visual biosensor was designed for organophosphorus pesticides (OPs) detection using DNA functionalized Ag/Au bimetallic nanoparticles (Ag/Au NPs) as multifunctional nanoprobe. The dual-signal detection strategy was based on the inhibition of enzyme-induced H2O2 generation by OPs in the detection solution containing acetylcholinesterase (AChE), choline oxidase (CHO), acetylcholine (ACh) and nanoprobe. H2O2 produced by enzyme-catalyzed reaction could trigger the etching of Ag and dissociation of carboxyfluorescein (FAM)-labeled aptamer from the nanoprobe, resulting in significant localized surface plasmon resonance (LPRR) and fluorescence (FL) signal responses. In the presence of OPs, AChE activity was inhibited to disrupt the enzymatic generation of H2O2, which allowed to simultaneous quantitative measure OPs through the LSPR peak shifts and FL intensity variations of the nanoprobe. The LSPR/FL dual-signal biosensor showed great selectivity and sensitivity for OPs detection. In addition, two distinct colour changes were visually observed to match the LSPR/FL spectra signal responses, which was a feasible means for visual analysis of OPs. Consequently, the work provided a dual-signal visual biosensor via the combination of multifunctional nanoprobe, and had significant potential to monitor pesticide residue with high anti-interference capability and detection accuracy.

Dual-mode immunosensor based on Cu-doped Mo2C nanosheets as signal labels

A method for detecting of Carcinoembryonic antigen(CEA) with improved accuracy is urgently needed. In this work, a dual-mode immunosensor for accurate detection of CEA was fabricated, which used a Cu-doped Mo2C co-catalyst as an enhancer. Especially, Cu-doped Mo2C presents a strong different pulse voltammetry (DPV) signal for the electron transfer between Cu2+ and Cu+, without the addition of K3[Fe(CN6)] and other electron transfer mediators, but also shows high electrocatalytic activity towards H2O2 redox reactions. So that detection sensitivity of the chronoamperometry (CA) was enhanced. Furthermore, characterized by excellent conductivity, highly ordered pore distribution and great surface area, Ti3C2 Mxenes can be effective in promoting electron transfer and loading a large number of AuNPs. In the meantime, AuNPs can also immobilize CEA-Ab1 through Au-N bonds. Based on a Cu-Mo2C-Au dual-signal indicator, Ti3C2 Mxene-Au as the matrix, the immunsosensor was developed to achieve dual-signal detection of CEA. Satisfactory detection ranges (1 fg.mL−1 to 40 ng.mL−1) were obtained with limits of detection of 0.33 fg.ml−1 (DPV) and 1.67 fg.ml−1 (CA), respectively. Therefore, the prepared electrochemical immunosensor has good application prospects for the detection of CEA.

Copper Peroxide Nanodots Encapsulated in a Metal-Organic Framework for Self-Supplying Hydrogen Peroxide and Signal Amplification of the Dual-Mode Immunoassay.

The necessary step of directly adding hydrogen peroxide (H2O2) into the detection system in traditional immunoassays hampers their applications as a portable device for point-of-care analysis due to the unstable liquid form of H2O2. Herein, a strategy of self-supplying H2O2 and signal amplification triggering by copper peroxide nanodots encapsulated (CPNs) in metal-organic frameworks (ZIF-8) was proposed in an immunoassay for dual-signal detection of bisphenol A (a typical emerging organic pollutant), which was further fabricated as a lab-in-a-tube device integrated with a smartphone sensing platform. Herein, CPNs@ZIF-8 was modified on the antibody against bisphenol A; after the competitive binding of analytes, coating antigens, and antibodies, the released H2O2 and Cu2+ from encapsulated CPNs under the acidic condition will trigger a Fenton-like reaction to generate ·OH for oxidization of TMB; meanwhile, Cu2+ could quench the fluorescence of GSH-Au NCs, resulting in dual-mode signals for measurements. Most importantly, self-supplying H2O2 with high stability was undertaken by CPNs, and the remarkably increased signal molecule (CPN) loading was ascribed to the excellent capacity of metal-organic frameworks (ZIF-8). In addition, good recoveries were obtained from a colorimetric/fluorescent dual-mode strategy. The constructed device demonstrated great potential as a universal platform for rapid detection of various environmental contaminants using corresponding antibodies relying on its performance of satisfactory stability, sensitivity, and accuracy.

Mn3+/Mn4+ ion-doped carbon dots as fenton-like catalysts for fluorescence dual-signal detection of dopamine.

Carbon dots (CDs), a new zero-dimensional material, have ignited a revolution in the fields of sensing, bioimaging, and biomedicine. However, the difficulty of preparing CDs with Fenton-like catalytic properties has seriously hindered their application in the diagnosis of oxidation/reduction biomolecules or metal ions. Here, an innovative method was successfully established to synthesize Mn3+/Mn4+ ion-doped blue-green fluorescent CDs with Fenton-like catalytic properties using manganese acetate as the manganese source. Specifically, the CDs prepared here were equipped with functional groups of -COOH, NH2, C=O, and Mn-O, offering the possibility to function as a fluorescence sensor. More importantly, the introduction of manganese acetate resulted in the preparation of CDs with Fenton-like catalytic properties, and the dual-signal fluorescence detection of dopamine (DA) was realized with linear ranges of 100–275 nM and 325–525 nM, and the detection limits were 3 and 12 nM, respectively. In addition, due to the Fenton-like catalytic activity of Mn3+/Mn4+ ion-doped CDs, the material has broad application prospects in the detection of oxidation/reduction biomolecules or metal ions related to disease diagnosis and prevention.

An ultrasensitive dual-signal aptasensor based on functionalized Sb@ZIF-67 nanocomposites for simultaneously detect multiple biomarkers

In vitro detection of biomarkers requires ultrahigh sensitivity and accuracy. The use of a dual-signal (electrochemical and fluorescent) strategy has the ability of self-calibration and can overcome interferences seen from experimental and environmental factors influencing the experimental results, showing significant advantages in the detection of biomarkers. Here, we propose an enzyme-free and label-free dual-signal aptasensor based on functionalized Apt@antimonene quantum dot (Sb)@ methylene blue (MB)@ZIF-67/Apt@Sb@3,3′,5,5′-tetramethylbenzidine (TMB) @ZIF-67 material to simultaneously detect multiple tumour biomarkers -oestrogen receptor (ER) and human epidermal growth factor receptor-2 (HER2). The aptamer chain of HER2 and ER is adsorbed to cover the porous structure of ZIF-67 through Sb, which has the characteristics of single-chain adsorption, in which the target protein is desorbed later, further encapsulating its internal MB and TMB with good dual-signal properties. After Apt@Sb@MB@ZIF-67/Apt@Sb@TMB@ZIF-67 targeted HER2 and ER biomarkers, the aptamer chains on the Sb quantum dots were desorbed and transferred into the solution, and the MB and TMB signals were released. Negative pressure is applied to the ITO electrode to adsorb and enrich positively charged MB and TMB organic molecules for electrochemical detection, and the supernatant after centrifugation can be directly subjected to fluorescence detection. Therefore, accurate electrochemical and fluorescent dual-signal detection of HER2 and ER from tissue to serum is achieved. Notably, sensitive detection of HER2-ER biomarkers was achieved in only 30 min, with a detection range of 0–10 pg/mL and detection limits of 3.4 fg/mL and 6.9 fg/mL, respectively.

In situ encapsulation of SQDs by zinc ion-induced ZIF-8 growth strategy for fluorescent and colorimetric dual-signal detection of alkaline phosphatase

Controllable encapsulation of sulfur quantum dots (SQDs) into metal-organic frameworks (ZIF-8) by a surface-bound zinc ion-induced growth strategy, and SQDs@ZIF-8 was successfully prepared for alkaline phosphatase (ALP) detection. The new synthesis procedure involves first binding Zn2+ to the surface of SQDs to form SQDs/Zn, and then via zinc ion-induced in situ ZIF-8 growth to obtain SQDs@ZIF-8, which greatly improved the luminous efficiency of SQDs. The specific process of detecting ALP using pH-triggered fluorescence quenching of SQDs@ZIF-8: firstly ALP hydrolyzes 2-phosphate-l-ascorbic acid trisodium salt (AAP) to ascorbic acid (AA), and then the leakage of SQDs in the SQDs@ZIF-8 leads to a decrease in fluorescence intensity based on the destruction of ZIF-8 skeleton by H+ released by AA. A linear relationship was obtained between the fluorescence intensity and the ALP concentration in the range of 0.15–50 U/L, and the detection limit was 0.044 U/L. Moreover, it was found that free SQDs can be complexed with Fe2+ to produce wine red complexes, and the obtained UV absorbance and ALP concentration have a linear relationship in the range of 10–200 U/L. The detection range of ALP is significantly broadened based on the combination of the above two detection methods. Furthermore, SQDs@ZIF-8 exhibited excellent stability in water and was successfully applied to the fluorescence and colorimetric detection of ALP in human serum.

Dual-Mode Immunosensor for Electrochemiluminescence Resonance Energy Transfer and Electrochemical Detection of Rabies Virus Glycoprotein Based on Ru(bpy)32+-Loaded Dendritic Mesoporous Silica Nanoparticles.

Rabies is a serious zoonotic disease in almost all warm-blooded animals and causes fatal encephalitis. The detection of rabies virus (RABV) is critical and remains a significant challenge. Herein, an electrochemiluminescence resonance energy transfer (ECL-RET) and electrochemical (EC) dual-mode immunosensor was developed for highly sensitive detection of RABV glycoprotein. Dendritic mesoporous silica nanoparticles (DMSNs) were employed to load Ru(bpy)32+ and to obtain ECL probes (Ru@DMSNs). Ru@DMSNs were decorated on the electrode surface, followed by the modification of the RABV antibody (Ab1). RABV was specifically recognized and captured by Ab1, causing the decline of the ECL signal due to the obstruction of electron transfer. Additionally, manganese oxide nanoparticles (MnOx) modified with Ab2 can further quench the ECL signal of Ru@DMSNs via the RET between Ru@DMSNs and MnOx. Meanwhile, MnOx can catalyze the oxidation of o-phenylenediamine (o-PD), generating a significant differential pulse voltammetry (DPV) signal as a second signal to monitor RABV glycoprotein concentration. Consequently, an immunosensor was developed to achieve dual-signal detection of RABV and improve reliability. Under the optimal conditions, detection ranges of 0.10 pg·mL-1 to 10 ng·mL-1 for ECL (with an 88 fg·mL-1 detection limit) and 1 pg·mL-1 to 2 ng·mL-1 for EC (with a 0.1 pg·mL-1 detection limit) were obtained for RABV detection. The reliability of this immunoassay was validated by eight brain tissue samples. The results were found to be compatible with the results of the real-time reverse transcription-polymerase chain reaction (RT-PCR) assay, indicating the potential applicability of this method for RABV diagnosis.

Anodic Stripping Voltammetric Analysis of Trace Arsenic(III) on a Au-Stained Au Nanoparticles/Pyridine/Carboxylated Multiwalled Carbon Nanotubes/Glassy Carbon Electrode.

A Au-stained Au nanoparticle (Aus)/pyridine (Py)/carboxylated multiwalled carbon nanotubes (C-MWCNTs)/glassy carbon electrode (GCE) was prepared for the sensitive analysis of As(III) by cast-coating of C-MWCNTs on a GCE, electroreduction of 4-cyanopyridine (cPy) to Py, adsorption of gold nanoparticles (AuNPs), and gold staining. The Py/C-MWCNTs/GCE can provide abundant active surface sites for the stable loading of AuNPs and then the AuNPs-initiated Au staining in HAuCl4 + NH2OH solution, giving a large surface area of Au on the Aus/Py/C-MWCNTs/GCE for the linear sweep anodic stripping voltammetry (LSASV) analysis of As(III). At a high potential-sweep rate of 5 V s−1, sharp two-step oxidation peaks of As(0) to As(III) and As(III) to As(V) were obtained to realize the sensitive dual-signal detection of As(III). Under optimal conditions, the ASLSV peak currents for oxidation of As(0) to As(III) and of As(III) to As(V) are linear with a concentration of As(III) from 0.01 to 8 μM with a sensitivity of 0.741 mA μM−1 and a limit of detection (LOD) of 3.3 nM (0.25 ppb) (S/N = 3), and from 0.01 to 8.0 μM with a sensitivity of 0.175 mA μM−1 and an LOD of 16.7 nM (1.20 ppb) (S/N = 3), respectively. Determination of As(III) in real water samples yielded satisfactory results.