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A turn-on fluorescence aptasensing approach for the highly sensitive and selective determination of 5-HT was proposed via target-induced knot displacement. 5-HT can be determined in a range from 0.5 nM to 100 nM with a limit of detection as low as 0.1 nM and a low dissociation constant of 2.3 nM. [ABSTRACT FROM AUTHOR]

A highly sensitive and selective electrogenerated chemiluminescence (ECL) biosensor was developed for the determination of matrix metalloproteinase 3 (MMP-3) in serum via the target-induced cleavage of an oligopeptide. One ECL probe (named as Ir-peptide) was synthesized by covalently linking a new cyclometalated iridium(III) complex ([(3-pba)2Ir(bpy-COOH)](PF6)) (3-pba = 3-(2-pyridyl) benzaldehyde, bpy-COOH = 4′-methyl-2,2′-bipyridine-4-carboxylic acid) with an oligopeptide (CGVPLSLTMGKGGK). An ECL biosensor was fabricated by firstly casting Nafion and gold nanoparticles (AuNPs) on a glassy carbon electrode and then self-assembling both of the ECL probes, 6-mercapto-1-hexanol and zwitterionic peptide, on the electrode surface, from which the AuNPs could be used to amplify the ECL signal and Ir-peptide could serve as an ECL probe to detect the MMP-3. Thanks to the MMP-3-induced cleavage of the oligopeptide contributing to the decrease in ECL intensity and the amplification of the ECL signal using AuNPs, the ECL biosensor could selectively and sensitively quantify MMP-3 in the concentration range of 10–150 ng·mL−1 and with both a limit of quantification (26.7 ng·mL−1) and a limit of detection (8.0 ng·mL−1) via one-step recognition. In addition, the developed ECL biosensor showed good performance in the quantization of MMP-3 in serum samples, with a recovery of 92.6% ± 2.8%–105.6% ± 5.0%. An increased level of MMP-3 was found in the serum of rheumatoid arthritis patients compared with that of healthy people. This work provides a sensitive and selective biosensing method for the detection of MMP-3 in human serum, which is promising in the identification of patients with rheumatoid arthritis. [ABSTRACT FROM AUTHOR]

A novel point-of-care testing (POCT) method for the determination of proteases was developed for the first time using a designed disposable capillary-fill device based on the cleavage of electrogenerated chemiluminescence (ECL)-label-tagged peptide probes and enabling elimination of the light-shielding from the magnetic beads (MBs). As a proof-of-principle, prostate-specific antigen (PSA) was taken as a model analyte, and streptavidin-coated magnetic beads bound with ruthenium-complex-tagged specific peptide (biotin-HSSKLQK) were utilized as MB ECL probes. The capillary-fill device was designed to be divided into a reaction zone and detection zone. In the reaction zone, the bio-cleavage reaction between the PSA analyte with the peptide on the surface of the MB ECL probes occurred, while in the detection zone, ECL emission was produced by a screen-printed carbon electrode, Ag/AgCl reference electrode and carbon counter electrode. When the analyte PSA was introduced into the suspension of MB ECL probes in the reaction zone of the device, biocleavage of the peptide occurred, and the cleaved Ru1 part was released from the surface of the MB ECL probes. The capillary-filled device was tilted 90°, and with the aid of gravity, the solution containing the released Ru1 part flowed to the surface of the working electrode in the detection region of the device, while the MB ECL probes were fixed in the reaction zone by an external magnet. PSA can be determined by the ECL emission from the released Ru1 part in the presence of the co-reactant tri-n-propylamine at the detection zone. Under the optimal conditions, the developed ECL method showed a low detection limit of 0.12 ng mL−1 for PSA. This work demonstrates that the developed ECL biosensing approach can eliminate the MB light-shielding effect and quantify proteases with high sensitivity and selectivity, which could be easily extended to POCT-based ECL biosensing for other proteases. [ABSTRACT FROM AUTHOR]

Electrogenerated chemiluminescence (ECL) involves the generation of species at electrode surfaces that then undergo electron-transfer reactions to form excited states that emit light. The ECL method is becoming an increasingly promising method in the life sciences, environmental analysis, and clinical analysis, owing to its good selectivity, high sensitivity, wide dynamic concentration response range, and potential and spatial controllability. Here, we give a mini-review on the advances of the ECL peptide-based bioassay using peptide as the molecular recognition element. First, a general history of ECL development is presented. Then, the general strategies of the ECL peptide-based bioassay are reviewed. Particular attention is paid to the related progress in the last 5 years. Finally, we conclude with the future challenges and prospects in the development of the ECL peptide-based bioassay.

We report the rational design of the matrix‐free carbon dots (C‐dots) with long wavelength and wavelength‐tunable room‐temperature phosphorescence (RTP). Taking advantage of microwave‐assisted heating treatment, three RTP C‐dots in boric acid (BA) composites are synthesized by using diethylenetriaminepentakis (methylphosphonic acid) as a multiple‐sites crosslink agent, a moderately acid catalyst and P source; phenylenediamines (either o‐PD, m‐PD, or p‐PD, respectively) as building block while BA as a carbonization‐retardant matrix. After the water‐soluble BA matrix is removed by dialysis, three matrix‐free C‐dots are obtained with RTP emission at 540, 550 and 570 nm under an excitation wavelength of 365 nm. Alterations of RTP emission of three matrix‐free C‐dots are ascribed to the difference in their particle size and band gap from n‐π* transition. Furthermore, the application of three matrix‐free C‐dots are successfully performed in information encryption and decryption. [ABSTRACT FROM AUTHOR]