A new electrochemically active-inactive switching aptamer molecular beacon to detect thrombin directly in solution.

A new electrochemical aptamer molecular beacon (MB) was designed by the carminic acid (CA) covalently linking at the each end of a special single-stranded stem-loop shaped oligonucleotide and named as CAs-MB. CA is an electrochemically active molecule and two CA molecules at the ends of molecular beacon stem were closed enough to associate each other to be as CA dimer. The dimer was electrochemically inactive. It separated into two CA monomers and produced the electrochemical signal while CAs-MB combined with target. In this protocol, the detection strategy of CAs-MB for thrombin is based on electrochemical active-inactive switching between monomer and dimer forms of CA. In order to enhance the electrochemical signal, magnetic nanobeads (MNB) was applied by connecting CAs-MB with MNB through a duplex of DNA. With the magnetic enrichment, the detection limit for thrombin reached to 42.4 pM. The experiment results showed that this type of electrochemical active-inactive switching aptamer molecular beacon allowed the direct detection of target proteins in the solution with no requirement of removing uncombined CAs-MB. Besides, CAs-MB/MNB can be easily regenerated by using 2M NaCl solution to cleave the thrombin from the aptasensor.

Cheng G ，Shen B ，Zhang F ，Wu J ，Xu Y ，He P ，Fang Y ... -  《-》

A novel electrochemical detection method for aptamer biosensors.

Bang GS ，Cho S ，Kim BG 《BIOSENSORS & BIOELECTRONICS》

A signal-on electrochemical probe-label-free aptasensor using gold-platinum alloy and stearic acid as enhancers.

In the present study, a new electrochemical probe-label-free aptasensor for thrombin (TB) based on the amplification of gold-platinum alloy nanoparticles (Au-PtNPs) and stearic acid was reported. Nafion@multiwalled carbon nanotubes (MWCNTs) coated electrode was firstly modified with electrochemical probe of methylene blue (MB). Then, Au-PtNPs were electrodeposited onto the electrode surface for the immobilization of aptamer and further hybridization of stearic acid labeled thrombin aptamer (TBA). In the presence of TB, the TBA bound with TB and released from the self-assembled duplex on the electrode into solution, decreasing the steric hindrance of the aptasensor and facilitating catalytic efficiency of Au-PtNPs in the presence of MB toward H2O2 with an enhanced electrochemical signal. With the enhanced effect of Au-PtNPs/MB modified electrode and stearic acid, a detection limit as low as 3pM for TB was achieved. The aptasensor also exhibited good selectivity and reproducibility.

Yuan Y ，Yuan R ，Chai Y ，Zhuo Y ，Bai L ，Liao Y ... -  《-》

A solid-state electrochemiluminescence biosensing switch for detection of thrombin based on ferrocene-labeled molecular beacon aptamer.

Wang X ，Dong P ，Yun W ，Xu Y ，He P ，Fang Y ... -  《-》

Ultrasensitive electrochemical aptasensor for thrombin based on the amplification of aptamer-AuNPs-HRP conjugates.

Successful development of an ultrasensitive and highly specific electrochemical aptasensor for thrombin based on amplification of aptamer-gold nanoparticles-horseradish peroxidase (aptamer-AuNPs-HRP) conjugates was reported. In this electrochemical protocol, aptamer1 (Apt1) was immobilized on core/shell Fe(3)O(4)/Au magnetic nanoparticles (AuMNPs) and served as capture probe. Aptamer2 (Apt2) was dual labeled with AuNPs and HRP and used as detection probe. In the presence of thrombin, the sandwich format of AuMNPs-Apt1/thrombin/Apt2-AuNPs-HRP was fabricated. Remarkable signal amplification was realized by taking the advantage of AuNPs and catalytic reactions of HRP. Other proteins, such as human serum albumin, lysozyme, fibrinogen, and IgG did not show significant interference with the assay for thrombin. Linear response to thrombin concentration in the range of 0.1-60 pM and lower detection limit down to 30 fM (S/N=3) was obtained with the proposed method. This electrochemical aptasensor is simple, rapid (the whole detection period for a thrombin sample is less than 35 min), sensitive and highly specific, it shows promising potential in protein detection and disease diagnosis.

Zhao J ，Zhang Y ，Li H ，Wen Y ，Fan X ，Lin F ，Tan L ，Yao S ... -  《-》