Porous platinum nanotubes labeled with hemin/G-quadruplex based electrochemical aptasensor for sensitive thrombin analysis via the cascade signal amplification.

For the first time, a sensitive electrochemical aptasensor for thrombin (TB) was developed by using porous platinum nanotubes (PtNTs) labeled with hemin/G-quadruplex and glucose dehydrogenase (GDH) as labels. Porous PtNTs with large surface area exhibited the peroxidase-like activity. Coupling with GDH and hemin/G-quadruplex as NADH oxidase and HRP-mimicking DNAzyme, the cascade signal amplification was achieved by the following ways: in the presence of glucose and NAD(+) in the working buffer, GDH electrocatalyzed the oxidation of glucose with the production of NADH. Then, hemin/G-quadruplex as NADH oxidase catalyzed the oxidation of NADH to in situ generate H2O2. Based on the corporate electrocatalysis of PtNTs and hemin/G-quadruplex toward H2O2, the electrochemical signal was significantly amplified, allowing the detection limit of TB down to 0.15 pM level. Moreover, the proposed strategy was simple because the intercalated hemin offered the readout signal, avoiding the adding of additional redox mediator as signal donator. Such an electrochemical aptasensor is highly promising for sensitive detection of other proteins in clinical diagnostics.

Sun A ，Qi Q ，Wang X ，Bie P ... -  《-》

A pseudo triple-enzyme cascade amplified aptasensor for thrombin detection based on hemin/G-quadruplex as signal label.

In this work, a pseudo triple-enzyme cascade amplified electrochemical aptasensor based on hemin/G-quadruplex as signal label for thrombin (TB) was constructed and the amplified electrochemical signal was achieved by the corporate catalysis of alcohol dehydrogenase-graphene sheets (ADH-GSs) bionanocomposite and hemin/G-quadruplex, which simultaneously acted as NADH oxidase and HRP-mimicking DNAzyme. Through "sandwich" reaction, hemin/G-quadruplex labeled gold nanoparticles-ADH-GSs bionanocomposite (AuNPs-ADH-GSs) was captured on electrode surface and thus obtained the electrochemical signal. After the addition of ethanol into the electrolytic cell, ADH availably catalyzed the oxidation of ethanol with the reduction of NAD(+) to NADH. Then, hemin/G-quadruplex as NADH oxidase catalyzed the oxidization of NADH, accompanying with the production of H2O2. Simultaneously, hemin/G-quadruplex as HRP-mimicking DNAzyme catalyzed the reduction of the generated H2O2. Such a catalysis strategy greatly promoted the electron transfer of hemin and resulted in the specific enhancement of electrochemical signal. The proposed TB aptasensor achieved a linear range of 1 pM-50 nM with a detection limit of 0.3 pM (defined as S/N=3). In addition, it showed satisfying stability and reproducibility, good specificity and sensitivity, indicating promising application for the detection of various proteins in clinical analysis.

Yi H ，Xu W ，Yuan Y ，Bai L ，Wu Y ，Chai Y ，Yuan R ... -  《-》

A pseudo triple-enzyme electrochemical aptasensor based on the amplification of Pt-Pd nanowires and hemin/G-quadruplex.

Our present work aimed at developing a pseudo triple-enzyme cascade electrocatalytic electrochemical aptasensor for determination of thrombin with the amplification of alcohol dehydrogenase (ADH)-Pt-Pd nanowires bionanocomposite and hemin/G-quadruplex structure that simultaneously acted as NADH oxidase and HRP-mimicking DNAzyme. With the addition of ethanol to the electrolyte, the ADH immobilized on the Pt-Pd nanowires catalyzed ethanol to acetaldehyde accompanied by NAD(+) being converted to NADH. Then the hemin/G-quadruplex firstly served as NADH oxidase, converting the produced NADH to NAD(+) with the concomitant local formation of high concentration of H2O2. Subsequently, the hemin/G-quadruplex acted as HRP-mimicking DNAzyme, bioelectrocatalyzing the produced H2O2. At the same time, the Pt-Pd nanowires employed in our strategy not only provided a large surface area for immobilizing thrombin binding aptamer (TBA) and ADH, but also served as HRP-mimicking DNAzyme which rapidly bioelectrocatalyzed the reduction of the produced H2O2. Thus, such a pseudo triple-enzyme cascade electrochemical aptasensor could greatly promote the electron transfer of hemin and resulted in the dramatic enhancement of electrochemical signal. As a result, a wide dynamic concentration linear range from 0.2 pM to 20 nM with a low detection limit of 0.067 pM for thrombin (TB) determination was obtained. The excellent performance indicated that our strategy was a promising way for ultrasensitive assays in electrochemical aptasensors.

Zheng Y ，Chai Y ，Yuan Y ，Yuan R ... -  《-》

An ultrasensitive electrochemical aptasensor for thrombin based on the triplex-amplification of hemin/G-quadruplex horseradish peroxidase-mimicking DNAzyme and horseradish peroxidase decorated FeTe nanorods.

Jiang L ，Yuan R ，Chai Y ，Yuan Y ，Bai L ，Wang Y ... -  《-》

Highly sensitive electrochemical thrombin aptasensor based on peptide-enhanced electrocatalysis of hemin/G-quadruplex and nanocomposite as nanocarrier.

In this work, we first conjugated a short peptide to thrombin binding aptamer (TBA) and bond hemin to the hybrid, effectively rendering hemin/G4-peptide more active over the original hemin/G4, so that a highly sensitive electrochemical thrombin (TB) aptasensor was developed based on it and PtNTs@rGO nanocomposite. It was the first report on the application of hemin/G4-peptide in electrochemical aptasensor. PtNTs@rGO with large surface area served as excellent nanocarrier for high loading of hemin/G4-peptide hybrids, resulting in the formation of hemin/G4-peptide-PtNTs@rGO bioconjugate as the secondary aptamer and further signal enhancement. The specific affinity of aptamer for target TB made the secondary aptamer go into the sensing interface, and then a noticeable current signal was obtained from hemin without additional redox mediators. Due to the collaborative electrocatalysis of hemin/G4-peptide and PtNTs toward H2O2, which was formed in situ during the process of hemin/G4-peptide-catalyzed oxidation of NADH with dissolved O2, the current intensity increased dramatically. Such an electrochemical aptasensing system could be used to detect TB with a linear range of 0.05 pM-60nM and very lower detection limit of 15fM. Notably, this method exhibited a higher sensitivity than that of many hemin/G4-based electrochemical strategies for TB detection due to the improvement of the catalytic activity of hemin/G4-peptide. The present works opened a new way for expanding the application of hemin/G4 in biological detection. With the mediator-free, proteinous enzyme-free yet high-sensitivity advantages, this electrochemical aptasensor held great promise for other biomarker detections in clinical diagnostics.

Wu Y ，Zou L ，Lei S ，Yu Q ，Ye B ... -  《-》