Electrochemiluminescence immunoassay for the carcinoembryonic antigen using CdSe:Eu nanocrystals

Hemin-graphene oxide-gold nanoflower-assisted enhanced electrochemiluminescence immunosensor for determination of prostate-specific antigen

An ultrasensitive luminol electrochemiluminescence (ECL) immunosensor was constructed for the detection of prostate specific antigen (PSA) using glucose oxidase-decorated hemin-graphene oxide-gold nanoflowers ternary nanocomposites as probes. Graphene oxide was first modified with hemin and then with gold nanoflowers through an in situ growth method, which has significantly boosted the catalytic activity of this graphene oxide-based peroxidase mimetics. The biocatalytical activity of this ECL immunosensor was thoroughly investigated to achieve selective recognition of the analyte molecules (PSA) by specific binding between antigens and antibodies. The limit of detection was calculated to be 0.32 pg mL^-1 with a signal-to-noise ratio of 3. A broad linear range from 7.5 × 10^-4 to 2.5 ng mL^-1 was obtained. Such step-by-step assembled biosensor showed controlled nanostructure and exhibited promising application in analysis of human serum samples with a recovery range of 90.6-111.8% and a RSD range of 3.9-5.5%.

Ratiometric electrochemical aptasensor for the sensitive detection of carcinoembryonic antigen based on a hairpin DNA probe and exonuclease I-assisted target recycling

A novel ratiometric electrochemical aptasensor was constructed for the detection of carcinoembryonic antigen (CEA) based on a hairpin DNA (hpDNA) probe and exonuclease Ⅰ (Exo Ⅰ)-assisted target recycling amplification strategy. A thiolated methylene blue (MB)-labeled hpDNA as the internal control element was fixed on the surface of the gold nanoparticles (AuNPs)-modified gold electrode (AuE) through Au-S bonds. A ferrocene (Fc)-modified aptamer DNA (Fc-Apt) was partially hybridized with hpDNA to form a Fc-Apt/hpDNA duplex. Due to the specific recognition of Fc-Apt to CEA, the presence of CEA caused dissociation of Fc-Apt from the duplex, and further triggered the degradation process of Exo Ⅰ and recycling of CEA. Hence, the Fc tags were released from the electrode surface and the oxidation peak current of Fc (I_Fc) decreased while that of MB (I_MB) remained stable owing to the distance between MB tags and the electrode unchanged. A linear relationship was observed between I_Fc/I_MB and the logarithm of CEA concentration from 10 pg mL^-1 to 100 ng mL^-1 with a detection limit of 1.9 pg mL^-1. Moreover, the developed aptasensor had been applied to detect CEA in diluted human serum with satisfactory results, indicating its great potential in practical applications.

Electrodeposition immobilized molybdenum disulfide quantum dots and their electrochemiluminescence application in the detection of melamine residues in milk powder

In this paper, one-step hydrothermal and electrodeposition methods were used to prepare a MoS2 quantum dot (QD) solid-phase electrochemiluminescent (ECL) electrode for the detection of melamine residues in milk powder. With the assistance of chitosan, MoS2 QDs fixed by the one-step electrodeposition method show better ECL performance than those by traditional deposition methods due to better dispersibility and stability. Based on the quenching of the MoS2 QDs ECL signal by melamine, quantitative detection of melamine in the sample was performed. The structure and morphology of a MoS2-CHIT/indium tin oxide (ITO) solid-phase ECL electrode were characterized by TEM and XPS, and melamine was detected by the ECL method using a three-electrode system. The proposed sensor exhibited good linearity in the range of 1.00 × 10-11 to 1.00 × 10-7 mol L-1 (ΔI = 12 100.62 + 1009.93 lg c (mol L-1), R2 = 0.997), and the method shows the advantages of simplicity and sensitivity compared to traditional detection methods. The interference of common ions in milk powder on the modified electrode was within 5%, and the recovery rate of real sample detection was within 97-98%. As a result, the proposed method is suitable for detecting melamine residues in milk powder.

Synthesis of europium(iii)-doped copper nanoclusters for electrochemiluminescence bioanalysis

We reported an electrochemiluminescence biosensing platform based on europium(iii)-doped copper nanoclusters that exhibited excellent analytical performances of high stability and enhanced intensity.

Electrochemiluminescence Quenching Sensor of a Carboxylic Carbon Nanotubes Modified Glassy Carbon Electrode for Detecting Crystal Violet Based on Nitrogen-doped Graphene Quantum Dots@Peroxydisulfate System

In this work, the electrochemiluminscence system of nitrogen-doped graphene quantum dots (N-GQDs) and K₂S₂O₈ was built for the determination of crystal violet (CV). Meanwhile, a carboxylic carbon nanotubes modified glassy carbon electrode (CCNTs/GCE) was used as an ECL sensor. Thanks to the excellent electron transfer ability and large surface area of CCNTs, the ECL signal of N-GQDs@S₂O₈^2- was remarkablely amplified. With the presence of a low concentration of CV, a distinct decrease of the ECL signal was observed due to a quenching effect of CV on the ECL emission. Moreover, the quenched ECL intensity responded linearly to the logarithm of CV concentration within the range of 0.05 - 5 μmol/L, with a LOD of 45 nmol/L (S/N = 3). The proposed ECL system exhibited high sensitivity and specificity to CV, which was successfully applied in the practical detection of CV in real water samples from a local fishpond farm.

Electrochemiluminescent biosensor with DNA link for selective detection of human IgG based on steric hindrance

A highly selective DNA-based electrochemiluminescence (ECL) based biosensor is described for the detection of human IgG. It is exploiting the effect of steric hindrance that affects the strength of the ECL signal in the presence of IgG. Digoxin-linked signaling DNA was specifically bound to IgG, and this causes steric hindrance which limits the ability of DNA to hybridize with capturing DNA attached to a gold electrode. Europium (II) doped CdSe quantum dots were covalently linked to the DNA in order to generate the ECL signal. Using this steric hindrance hybridization method, the ECL signal of the biosensor were proportional to the concentration of IgG with a wide linear range and a 14 pM detection limit. Conceivably, the method can be expanded to the detection of a wide range of proteins for which homologous recognition elements are available.

A cascade amplification strategy of catalytic hairpin assembly and hybridization chain reaction for the sensitive fluorescent assay of the model protein carcinoembryonic antigen

A cascade nucleic acid amplification strategy is presented for fluorometric aptamer based determination of the model protein carcinoembryonic antigen (CEA). Amplification is accomplished by combining catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR). In this assay, a specially designed single-stranded DNA containing the aptamer sequence (AS) specific for CEA is hybridized with an inhibitor strand (IS) to form a double-stranded DNA (IS@AS). In the presence of CEA, it will recognize and bind to the AS strand which causes the release of IS. By introducing two DNA hairpins (H1 and H2; these containing complementary sequences) CHA will be activated via the hybridization reactions of H1 and H2. This is accompanying by the formation of a double-stranded DNA (H1-H2) and the release of CEA@AS. The liberated CEA@AS further drives successive recycling of the CHA, thereby generating further copies of H1-H2. The resultant H1-H2 hybrids act as primers and trigger HCR with the help of other two DNA hairpins (H3 and H4) containing G-rich toehold at the 5'-terminus and 3'-terminus of H3 and H4, respectively. The fluorescent probe N-methyl mesoporphyrin IX (NMM) is finally intercalated into the G-rich domains of the long DNA nanostructures due to formation of G-quadruplex structures. This generates a fluorescent signal (best measured at excitation/emission wavelengths of 399/610 nm) that increases with the concentration of target (CEA). This aptamer-based fluorescence assay is highly sensitive and has a linear range that covers the 1 pg·mL^-1 to 2 ng·mL^-1 CEA concentration range, with a 0.3 pg·mL^-1 detection limit. Graphical abstract By integrating catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR) for effective signal enhancement, a novel cascade amplification strategy is presented to develop a sensitive and selective fluorescent method for the assay of the model protein carcinoembryonic antigen (CEA).