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Abstract Competitive host-guest recognition has been utilized to determine small molecules using macrocyclic supramolecular host, while less studies focused on the specific recognition and sensing of protein. In the present work, we are the first time to report a label-free fluorescent assay for insulin determination based on the supramolecular recognition between cationic pillar[6]arene (CP6) and insulin. The approach is based on fluorescence resonance energy transfer (FRET) through competitive recognition between CP6 functionalized reduced graphene oxide (CP6@rGO) and probe/insulin molecules. Probe molecule (RhB) has strong fluorescent signal, and its fluorescent is quenched by rGO based on FRET. When target protein molecule (insulin) is added to CP6@rGO, the probe is displaced by insulin and a host-guest complex CP6@rGO/insulin is formed, resulting in a "turn-on" fluorescence signal. The fluorescence intensity of complex increased linearly with the increase of insulin concentration ranging 0.01–0.50 and 1.0–16.0 μM, respectively with a detection limit of 3 nM. The sensor was successfully utilized to determine insulin in artificial serum. The molecular docking result showed that the N-terminal Phe of insulin's B chain was included in the CP6 cavity through electrostatic interaction and formed a stable host-guest complex. Graphical abstract Fluorescent approach for insulin sensing using pillar[6]arene functionalized graphene. fx1 Highlights • A novel fluorescent sensing platform for insulin detection was presented. • Cationic pillar[6]arene functionalized reduced graphene oxide was used as a receptor. • Insulin was included in the pillar[6]arene cavity and formed a stable complex. [ABSTRACT FROM AUTHOR]

Norovirus (NoV) is a major foodborne pathogen responsible for acute gastroenteritis epidemics, and establishing a robust detection method for the timely identification and monitoring of NoV contamination is of great significance. In this study, a peptide-target-aptamer sandwich electrochemical biosensor for NoV was fabricated using Au@BP@Ti 3 C 2 -MXene and magnetic Au@ZnFe 2 O 4 @COF nanocomposites. The response currents of the electrochemical biosensor were proportional to the NoV concentrations ranging from 0.01–105 copies/mL with a detection limit (LOD) of 0.003 copies/mL (S/N = 3). To our best knowledge, this LOD was the lowest among published assays to date, due to the specific recognition of the affinity peptide and aptamer for NoV and the outstanding catalytic activity of nanomaterials. Furthermore, the biosensor showed excellent selectivity, anti-interference performance, and satisfactory stability. The NoV concentrations in simulative food matrixes were successfully detected using the constructed biosensor. Meanwhile, NoV in stool samples was also successfully quantified without complex pretreatment. The designed biosensor had the potential to detect NoV (even at a low level) in foods, clinical samples, and environmental samples, providing a new method for NoV detection in food safety and diagnosing foodborne pathogens. [Display omitted] • An NoV sensor was constructed based on BP@Ti 3 C 2 -Mxene and magnetic COF. • The sensor showed the lowest detection limit of 0.003 copies/mL of NoV. • The sensor had high sensitivity, satisfactory selectivity, and good stability. • The NoV was successfully detected using the designed sensor. [ABSTRACT FROM AUTHOR]

This work describes a novel affinity peptide–antibody sandwich electrochemical strategy for the ultrasensitive detection of prostate-specific antigen (PSA). Herein, polydopamine-coated boron-doped carbon nitride (Au@PDA@BCN) was synthesized and used as a sensing platform to anchor gold nanoparticles and immobilize primary antibody. Meanwhile, AuPt metallic nanoparticle and manganese dioxide (MnO 2)-functionalized covalent organic frameworks (AuPt@MnO 2 @COF) was facilely synthesized to serve as a nanocatalyst and ordered nanopore for the enrichment and amplification of signal molecules (methylene blue, MB). PSA affinity peptide was bound to AuPt@MnO 2 @COF to form Pep/MB/AuPt@MnO 2 @COF nanocomposites (probe). The peptide–PSA–antibody sandwich biosensor was constructed, and the redox signal of MB was measured with the existence of PSA. The fabricated sensor exhibited a linear response (0.00005–10 ng mL−1) with a low detection limit of 16.7 fg mL−1 under the optimum condition. Additionally, the sensor showed an excellent selectivity, ideal repeatability, and good stability for PSA detection in real samples. Furthermore, the porous structure of COF can enrich more MB molecules and increase the sensitivity of the biosensor. This study provides an efficient and ultrasensitive strategy for PSA detection and broadens the use of organic/inorganic porous nanocomposite in biosensing. [Display omitted] • An affinity peptide-antibody sandwich electrochemical biosensor for PSA was developed. • The biosensor was based on AuPt/covalent organic frameworks nanocomposite. • The detection limit of the biosensor was 16.7 fg mL−1. • The biosensor was successfully adopted to PSA determination in real sample. • The biosensor showed high sensitivity, excellent stability, and ideal reproducibility. [ABSTRACT FROM AUTHOR]