Peptide and carbon nanotubes assisted detection of apoptosis by square wave voltammetry

Programmable DNA Circuit-Facilitated Determination of Circulating Extracellular Vesicle PD-L1 for Lung Cancer Diagnosis and Immunotherapy Response Prediction

Circulating extracellular vesicle (EV) PD-L1 is correlated with the occurrence and progression of lung cancer and has great potential as a valuable diagnostic and immunotherapy predictive biomarker. In this work, we propose a fluorescent biosensing method for the sensitive and accurate determination of circulating EV PD-L1. Specifically, after the phosphatidylserine-targeting peptide-assisted magnetic enrichment, a programmable DNA circuit is designed to translate the presence of PD-L1 to the appearance of numerous duplex DNA probes on the circulating EV surface. Upon fructose treatment, these newly formed duplex DNA probes are released from the EV surface to activate the trans-cleavage activity of CRISPR/Cas12a system, which finally produces a significant fluorescence signal. Experimental results reveal that the method not only enables sensitive determination of EV PD-L1 with a detection limit of 67 particles/mL but also demonstrates the potential use in the diagnosis and immunotherapy response prediction of lung cancer in a principle-of-proof study. Therefore, the method may provide a useful tool for EV PD-L1 determination, which may provide valuable information for the precise diagnosis and personalized treatment of lung cancer patients.

A Versatile Design-Enabled Analysis of Circulating Extracellular Vesicles in Disease Diagnosis

Circulating extracellular vesicles (EVs) are considered as potential biomarkers for treatment and diagnosis of many diseases. Most of the existing methods for the EV analysis only have a single function and thus reveal limited information carried by EVs. Herein, a phosphatidylserine-targeting peptide-facilitated design that enables the versatile analysis of circulating EVs for varying requirement is proposed. In the design, DNA probes are inserted into the EV membrane through hydrophobic interactions, and accelerate the removal of protective shielding from DNA-gated metal-organic framework, thereby releasing a large number of methylene blue molecules to amplify the electrochemical signal. Electrochemical results demonstrate equally high sensitivities toward the quantification of EVs derived from different cell sources using an indiscriminative DNA probe. More importantly, the probe can be endowed with extended function for more accurate classification of cell-specific features through the identification of specific EV biomarkers, and demonstrates the potential use in the diagnosis of cardiovascular in a principle-of-proof study for clinical application. Therefore, the method provides a versatile design for the identification of EV features, and may address the needs of clinical diagnosis in the future.

Multiwalled carbon nanotube nanofiller-polyindole polymer matrix-based efficient biosensor for the rapid detection of swine flu

Pictorial representation of the synthesis of the electrode material, fabrication and electrochemical response of the biosensing platform for swine flu detection.

Peptide self-assembly assisted signal labeling for an electrochemical assay of protease activity

Peptide self-assembly holds tremendous promise for a range of applications in chemistry and biology. In the work reported here, we explored the potential functions of peptide self-assembly in electrochemical bioanalysis by developing a peptide self-assembly assisted signal labeling strategy for assaying protease activity. The fundamental principle of this assay is that target-protease-catalyzed specific proteolytic cleavage blocks self-assembly between the probe peptide and signal peptide, thus preventing the signal labeling of electroactive silver nanoparticles on the electrode surface, which in turn causes the electrochemical signal to decrease. Using trypsin as an example protease target, the linear range of this assay was found to be 1 ng mL^-1 to 100 mg mL^-1, and its detection limit was 0.032 ng mL^-1, which are better than the corresponding parameters for previously reported assays. Further experiments also highlighted the good selectivity of the assay method and demonstrated its usability when applied to serum samples. Therefore, this report not only introduces a valuable tool for assaying protease activity, but it also promotes the utilization of peptide self-assembly in electrochemical bioanalysis, as this approach has great potential for practical use in the future.

Quantum dots-based fluorescence resonance energy transfer biosensor for monitoring cell apoptosis

The development of advanced methods for accurately monitoring cell apoptosis has extensive significance in the diagnostic and pharmaceutical fields. In this study, we developed a rapid, sensitive and selective approach for the detection of cell apoptosis by combining the site-specific recognition and cleavage of the DEVD-peptide with quantum dots (QDs)-based fluorescence resonance energy transfer (FRET). Firstly, biotin-peptide was conjugated on the surface of AuNPs to form AuNPs-pep through the formation of an Au-S bond. Then, AuNPs-pep-QDs nanoprobe was obtained through the connection between AuNPs-pep and QDs. FRET is on and the fluorescence of QDs is quenched at this point. The evidence of UV-vis spectra, transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy revealed that the connection was successful. Upon the addition of apoptosis cell lysis solution, peptide was cleaved by caspase-3, and AuNPs was dissociated from the QDs. At this time, FRET is off, and thus the QDs fluorescence was recovered. The experimental conditions were optimized in terms of ratio of peptide to AuNPs, buffer solution, and the temperature of conjugation and enzyme reaction. The biosensor was successfully applied to distinguishing apoptosis cells and normal cells within 2 h. This study demonstrated that the biosensor could be utilized to evaluate anticancer drugs.