An evaporation induced self-assembly approach to prepare polymorphic carbon dot fluorescent nanoprobes for protein labelling

Herein, we report a novel route to prepare polymorphic carbon dot fluorescent probes via the evaporation-induced self-assembly of glutaraldehyde and carbon dots, which first usually form carbon nanoclusters which then could self-assemble to form carbon nanocrystals, nanospheres or nanofibers in different ionic strength solutions at room temperature.

Sensitive and low-background electrochemical assay of corin activity via supramolecular recognition and rolling circle amplification

Corin is an important member of type II transmembrane serine proteases that is involved in a variety of cardiovascular and pregnancy-related diseases. Herein, a sensitive and low-background electrochemical method is proposed to assay the activity of corin. In principle, a peptide comprising both the substrate motif of corin and binding site of cucurbit[8]uril (CB[8]) is first designed and immobilized on the electrode surface. Thereafter, via CB[8]-mediated supramolecular recognition, a DNA-primer is recruited, subsequently triggering the rolling circle amplification (RCA) reaction. In this way, a succeeding propagation of DNA strands is achieved on the electrode surface, which would produce remarkable repelling effect against the electrochemical species [Fe(CN)6](3-/4-), and thereby yield a highly minimized background signal. However, in the presence of activated corin, the peptide is specifically recognized and cleaved, breaching the recruitment of DNA primer as well as the RCA reaction, which decreases the repulsion to [Fe(CN)6](3-/4-), leading to a remarkable electrochemical response. As a result, the proposed assay method can sensitively determine the activity of corin with a detection limit of 0.92 pM, and can further be directly used in maternal plasma samples. Therefore, this method may provide a promising tool for pathological research and clinical diagnosis of corin-related diseases.

Grafting of a peptide probe for Prostate-Specific Antigen detection using diazonium electroreduction and click chemistry

The main objective of this work was to validate a label-free electrochemical method of protein detection using peptides as capture probes. As a proof-of-concept, we used a 7 amino acids sequence (HSSKLQL) specific for Prostate Specific Antigen. We investigated various electrografting conditions of two anilines (2-[(4-aminophenyl)sulfanyl]-8-hydroxy-1,4-naphthoquinone and 4-azidoaniline) further converted in situ into their corresponding diazonium salts on glassy carbon electrodes. It was demonstrated that the best method to obtain a mixed layer is the simultaneous electroreduction of the two diazonium salts. 4-azidoaniline was used to covalently immobilize the ethynyl-functionalized peptide probe by click coupling, and the hydroxynaphthoquinone derivative plays the role of electrochemical transducer of the peptide-protein recognition. The proteolytic activity of PSA towards a small peptide substrate carrying streptavidin at its distal end was also investigated to design an original sensing architecture leading to a reagentless, label free, and "signal-on" PSA sensor. Without optimization, the limit of quantification can be estimated in the nM to pM range.

Electrochemical Peptide Biosensor Based on in Situ Silver Deposition for Detection of Prostate Specific Antigen

In this work, we have demonstrated a novel electrochemical method based on target-induced cleavage of a specific peptide for sensitive analysis of prostate specific antigen (PSA) by using silver enhancement. First, multiwalled carbon nanotubes/poly(amidoamine) dendrimers (MWCNTs-PAMAM) nanohybrids were assembled on the electrode to bind the peptide. Subsequently, dithiobis(succinimidylpropionate) (DSP)@Au@SiO2 was prepared as a tracing tag and covalent bond with the peptides via the inherent interaction between DSP and the amino of peptide. In the presence of PSA, the peptide was specifically recognized and cleaved, resulting in the loss of the tracing tag in electrode surface. Thereafter, silver enhancement was performed on the left DSP@Au@SiO2 nanohybrids. The electrochemical stripping signal of the deposited silver was used to monitor this process. Under optimal conditions, the proposed biosensor achieved a wide line from 0.001 to 30 ng mL(-1) with a detection limit of 0.7 pg mL(-1). This work demonstrated the combination of the direct transduction of peptide cleavage events with the highly sensitive silver enhancement method, providing a promising effective strategy for PSA detection.

An electrochemical peptide cleavage-based biosensor for prostate specific antigen detection via host–guest interaction between ferrocene and β-cyclodextrin

Here we have developed a “signal-on” peptide cleavage-based assay for sensitive and specific detection of prostate specific antigen (PSA) by coupling the host–guest interaction between ferrocene (Fc) and β-cyclodextrin (β-CD).

Rational design of Au nanorods assemblies for highly sensitive and selective SERS detection of prostate specific antigen

A simple SERS immunosensor based on AuNRs assembly was developed for rapid detection of specific antigen in early diagnostics.