Enhanced catalytic amplification of mesoporous bismuth-gold nano-electrocatalyst triggering efficient capture of tumor marker.

A new sandwich-type electrochemical immunosensor for the sensitive detection of carcinoembryonic antigen (CEA) was originally developed using a unique bismuth (Bi)-gold (Au) nano-electrocatalyst triggering efficient capture of tumor marker, where the nano-electrocatalyst was obtained by implanting Au nanoparticles (Au NPs) inside the mesoporous NBiOF nanospheres (Au@NBOF NSs) for the purpose to marker secondary antibody (Ab2) and amplify the response signal through electrochemically catalyzing the reduction of hydrogen peroxide. The synergistic interaction between NBOF NSs and Au NPs endowed the as-received Au@NBOF nano-electrocatalyst with large electrocatalytic active surface area and powerful signal amplification function as upper sandwich layer to conjugate Ab2. The multi-walled carbon nanotubes sparkled with Au nanostars served as the lower sandwich layer to capture the primary antibody (Ab1), which enhanced the interfacial electron transport and the load capacity of Ab1 as a result of increasing the sensing response of the designed immunosensor based on the sandwich-type Ab1-CEA-Ab2 interaction. Such immunosensor proposed on the above double signal amplification strategy efficiently detected the target CEA in a wide concentration range from 100 fg mL-1 to 200 ng mL-1. The detection limit was as low as 9.57 fg mL-1 with excellent specificity and reproducibility. The satisfactory results in analyzing human serum samples indicate the potential application of this new immunosensor in early clinical diagnosis of cancer and the evaluation of treatment efficiency.

Rapid electrochemical detection of MiRNA-21 facilitated by the excellent catalytic ability of Pt@CeO2 nanospheres.

Pt@CeO2 nanospheres (NSs) were first synthesized by simply mixing Ce(NO3)3 and K2PtCl4 under the protection of pure argon at 70 °C for 1 h, which exhibited excellent catalytic ability toward hydrogen peroxide (H2O2). An electrochemical biosensor was successfully developed using Pt@CeO2 NSs as a capture probe for the ultra-sensitive and fast detection of miRNA-21, a new type of biomarker for disease diagnostics, especially for cancer. During the step-by-step construction process of the RNA sensor, Pt@CeO2 NSs were functionalized with streptavidin (SA) to obtain SA-Pt@CeO2 NSs through amide bonds. Gold nanoparticles (Au NPs) were electrodeposited on the surface of the glassy carbon electrode to improve the transmission capacity of electrons and provided Au atoms for fixing the thiolated capture probe (SH-CP) with a hairpin structure on the electrode via forming Au-S bonds. The target miRNA-21 specifically hybridized with SH-CP and opened the hairpin structure to form a rigid duplex so as to activate the biotin at the end of the capture probe. SA-Pt@CeO2 NSs were thus specially attached to the electrode surface through the biotin-streptavidin affinity interaction, finally leading to the significant signal amplification. The ultra-sensitive and rapid detection of miRNA-21 was finally realized as expected benefiting from the excellent catalytic ability of Pt@CeO2 NSs toward H2O2 in a wide linear concentration range from 10 fM to 1 nM with the detection limit as low as 1.41 fM. The results achieved with this new RNA sensor were quite satisfactory during the blood sample analysis.

A frogspawn-like Ag@C core-shell structure for an ultrasensitive label-free electrochemical immunosensing of carcinoembryonic antigen in blood plasma.

A three-dimensional (3D) frogspawn-like structure was achieved by simply coating nano-carbon outside silver nanospheres (Ag@C NFS) and used as a probe to capture the anti-carcinoembryonic antigen for the electrochemical immunosensing of carcinoembryonic antigen (CEA), a typical biomarker of several diseases such as gastric cancer, intestinal cancer and colon cancer. Moreover, Ag@C nanocables (Ag@C NCs) were aslo synthesized. By comparison, the globular 3D frogspawn-like structure endowed Ag@C NFS with a larger surface area, which is preferred to improve the capability of loading antibodies, higher water solubility, better biocompatibility and improved electrical conductivity, which was likely attributed to the synergistic effects of Ag and crystalline graphite carbon and the different structure with more hydroxyl groups exposed. Therefore, the resultant Ag@C NFS was used as an electrochemical immunosensing platform to fabricate a label-free immunosensor for the analysis of CEA, which showed an excellent immunosensing performance with a wide linear CEA detection range from 0.0001 ng mL-1 to 100 ng mL-1 and a low detection limit of 5.12 pg mL-1. In particular, the good reproducibility, high stability and specificity of the proposed immunosensor ensured the successful application in the quantitative determination of CEA in cancerous human serum samples, providing a promising alternative to detect other biomarkers.