Electrochemical Aptasensor For Ultrasensitive Detection Research Articles

Label free electrochemical aptasensor for ultrasensitive detection of ractopamine

A label free electrochemical (EC) aptasensor for ultrasensitive detection of ractopamine (RAC) was developed. A special immobilization media consisting of gold nanoparticles/poly dimethyl diallyl ammonium chloride-graphene composite (AuNPs/PDDA-GN) was utilized to improve conductivity and performance of the biosensor. The RAC aptamer was attached on AuNPs of the composite membrane via Au-S bond. The fabrication process of the EC aptasensor was characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The peak currents obtained by differential pulse voltammetry decreased linearly with the increasing of RAC concentrations and the sensor responds approximately logarithmically over a wide dynamic range of RAC concentration from 1.0 × 10(-12)mol/L to 1.0 × 10(-8)mol/L. The linear correlation coefficient of the developed aptasensor was 0.998, the limit of detection was 5.0 × 10(-13)mol/L. The proposed EC aptasensor displayed good stability, reproducibility and robust operation in animal urine. Particularly, the generality of the fabrication approach of electrochemical aptasensor is highlighted with a further example for illegal drugs detection via the aptamer identification.

A novel electrochemical aptasensor for ultrasensitive detection of kanamycin based on MWCNTs-HMIMPF6 and nanoporous PtTi alloy.

A novel aptasensor based on a novel composite film consisting of multi-walled carbon nanotubes (MWCNTs), ionic liquid (IL) of 1-hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF6), and nanoporous PtTi (NP-PtTi) alloy was constructed for ultrasensitive detection of kanamycin. The NP-PtTi alloy was successfully fabricated by a simple dealloying of PtTiAl source alloy in HCl solution. The NP-PtTi alloy has uniform interconnected network structure with specific surface area and was used to immobilize aptamer. After modified with the composite material, current signal was amplified obviously, which attributed to the larger specific surface area and excellent electrical conductivity of NP-PtTi and MWCNTs. A number of factors affecting the activity of the aptasensor have been discussed and optimized. Under the optimized conditions, the proposed aptasensor provided a linear range of 0.05-100 ng mL(-1) with a low detection limit of 3.7 pg mL(-1). This aptasensor displayed high sensitivity, stability and reproducibility. In addition, the as-prepared aptasensor was successfully used for the determination of kanamycin in a real sample.

Target-aptamer binding triggered quadratic recycling amplification for highly specific and ultrasensitive detection of antibiotics at the attomole level.

A novel electrochemical aptasensor for ultrasensitive detection of antibiotics by combining polymerase-assisted target recycling amplification with strand displacement amplification with the help of polymerase and nicking endonuclease has been reported. This work is the first time that target-aptamer binding triggered quadratic recycling amplification has been utilized for electrochemical detection of antibiotics.

A signal-on electrochemical aptasensor for ultrasensitive detection of endotoxin using three-way DNA junction-aided enzymatic recycling and graphene nanohybrid for amplification

Endotoxin, also known as lipopolysaccharide (LPS), is able to induce a strong immune response on its internalization into mammalian cells. To date, aptamer-based biosensors for LPS detection have been rarely reported. This work describes a new signal-on electrochemical aptasensor for the ultrasensitive detection of LPS by combining the three-way DNA hybridization process and nanotechnology-based amplification. With the help of DNA1 (associated with the concentration of target LPS), the capture probe hybridizes with DNA1 and the assistant probe to open its hairpin structure and form a ternary "Y" junction structure. The DNA1 can be released from the structure in the presence of nicking endonuclease to initiate the next hybridization process. Then a great deal of cleaved capture probe produced in the cyclic process can bind with DNA2-nanocomposite, which contains the electroactive toluidine blue (Tb) with the amplification materials graphene (Gra) and gold nanoparticles (AuNPs). Thus, an enhanced electrochemical signal can be easily read out. With the cascade signal amplification, this newly designed protocol provides an ultrasensitive electrochemical detection of LPS down to the femtogram level (8.7 fg mL(-1)) with a linear range of 6 orders of magnitude (from 10 fg mL(-1) to 50 ng mL(-1)). Moreover, the high sensitivity and specificity make this method versatile for the detection of other biomolecules by changing the corresponding sequences of the capture probe and the assistant probe.

Ultrasensitive aptasensor based on graphene-3,4,9,10-perylenetetracarboxylic dianhydride as platform and functionalized hollow PtCo nanochains as enhancers

A novel electrochemical aptasensor for ultrasensitive detection of thrombin is described that uses the conductive graphene-3,4,9,10-perylenetetracarboxylic dianhydride nanocomposites (GPA) as desirable sensor platform and hollow PtCo nanochains–thionine–Pt–HRP labeled secondary thrombin aptamer (HPtCoNCs–Thi–Pt–HRP–TBA, aptamer II) for signal amplification. With the surface area enhanced by GPA nanocomposites, the amount of immobilized primary thrombin aptamer can be improved. More importantly, the synthesized HPtCoNCs also yielded large surface area, which provide substantial binding sites for thionine–Pt–HRP–TBA. The thionine acts as a mediator of electron transfer between HRP and electrode surface. Enhanced sensitivity was achieved by introducing the multibioconjugates of aptamer II onto the electrode surface through “sandwich” reactions. With amplifying factors mentioned above, a wider linear range from 10−15 to 10−9M was acquired with an ultralow detection limit of 6.5×10−16M for thrombin. This amplification strategy showed acceptable stability and reproducibility, high sensitivity, and good precision, which could provide a promising potential for clinical screening and point-of-care diagnostics.

Direct electrochemistry and electrocatalysis of a glucose oxidase-functionalized bioconjugate as a trace label for ultrasensitive detection of thrombin

For the first time, a glucose oxidase-functionalized bioconjugate was prepared and served as a new trace label through its direct electrochemistry and electrocatalysis in a sandwich-type electrochemical aptasensor for ultrasensitive detection of thrombin.