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Immunoassay has shown great potential in the detection of various disease protein biomarkers because of its high specificity. However, the sensitivity of conventional immunoassay is relatively limited due to its insufficient colorimetric signal transduction. Herein, we report a novel dynamic light scattering (DLS) immunosensing strategy for ultrasensitive detection of protein markers based on the covalent organic framework-gold nanoparticle (COF@AuNP) heterostructures combined with the gold growth. By taking advantage of the unique acid response characteristics of imine-linked COF, the COF@AuNP is designed as a signal amplifier to boost the release of AuNPs, and then the released AuNPs are enlarged by gold growth to amplify the DLS signal transduction and thus remarkably improve the sensitivity. Combined with the double antibody sandwich magnetic immunoassay, the COF@AuNP-amplified DLS immunosensor successfully achieve the highly sensitive quantitative detection of N-terminal brain-type natriuretic peptide. The limit of detection reaches up to 14 fg mL−1 with the total assay time less than 2 h. The linear detection range was from 0.32 to 1000 pg mL−1, and the coefficient of variation was below 12.5%. Briefly, this immunosensor is demonstrated with high selectivity, accuracy, reproducibility, and reliability in spiked and actual whole blood samples. The COF@AuNP-amplified DLS immunosensing strategy holds high promise as an alternative for detecting disease biomarkers. [Display omitted] • COF@AuNP heterostructures were synthesized as a signal-amplification light-scattering probe. • The obtained imine-linked COF@AuNP exhibited unique acid response property. • A novel COF@AuNP amplified-DLS immunosensor was developed for ultrasensitive detection of NT-proBNP with an LOD of 14 fg mL−1. • Selectivity, accuracy, reproducibility, and reliability of this method were well characterized. [ABSTRACT FROM AUTHOR]

Abstract: Multiplexed electrochemical immunosensor was developed for ultrasensitive detection of interleukin-6 (IL-6) and interleukin-17 (IL-17) using electrochemical tag incorporated polystyrene sphere (PS) as label. The electrochemical tag contained in the PS, cadmium ion (Cd2+) or ferrocene (Fc), could be effectively detected by square wave voltammetry (SWV) after dissolving the PS with organic solvent to release the electrochemical tags onto electrode surface. With the immobilization of two different antibodies onto the PS surface, respectively, the position and intensity of the current peaks due to the two electrochemical tags could reflect the identity and level of the corresponding protein biomarkers. The significant amount of electrochemical tags incorporated into PS greatly enhanced the detection sensitivity. The proposed immunoassay exhibited high sensitivity and good selectivity for the detection of IL-6 and IL-17. The response current was linear to the logarithm concentrations of IL-6 and IL-17 in the range from 1pg/mL to1ng/mL and 2pg/mL to 1ng/mL, respectively. The detection limits of IL-6 and IL-17 were 0.5 and 1pg/mL (S/N=3). These results suggested that this electrochemical immunosensor would be widely applied for clinical screening of protein biomarkers. [Copyright &y& Elsevier]

Abstract: Sensitive electrochemical immunosensor for the detection of interleukin-17 (IL-17) was prepared using cadmium (Cd2+) ion incorporated polystyrene sphere (PS, PS–Cd2+) as label. With the linking of the detection anti-IL-17 antibody (Ab2) onto PS (PS–Cd2+–Ab2), the modified PS can be captured onto the electrode surface through immuno-reaction. Tetrahydrofuran (THF) was then dropped onto the electrode surface to dissolve the PS and release the contained Cd2+ ions onto electrode surface for the following stripping voltammetric detection. Compared to the electrochemical label based on quantum dots (QD), this method for the detection of Cd2+ ion is much simpler and straightforward. With the immobilization of primary anti-IL-17 antibody (Ab1) onto graphene surface, the resulting immunosensor displays high sensitivity, which can be ascribed to the significant number of Cd2+ ions incorporated into PS and a large number of Ab2 linked onto PS surface. The response current was linear to the logarithm of IL-17 concentration in the range from 0.1pg to 1ng/mL with a detection limit of 50fg/mL. The immunosensor results were validated through the detection of IL-17 in serum samples with satisfactory results. [Copyright &y& Elsevier]

[Display omitted] • A ratiometric fluorescent probe was designed for detecting ciprofloxacin (CIP). • The mechanism was based on Al3+-enhanced fluorescence of gold nanoclusters. • The probe displayed outstanding detection stability due to ratiometric response. • The probe also possessed the features of fast response and excellent sensitivity. • The probe was successfully applied to the determination of CIP in human urine. Fluoroquinolone antibiotics, especially ciprofloxacin (CIP), are commonly used in clinical practice as the antibacterial drugs. It is necessary to analyze CIP in biological media for studying its pharmacokinetics, further guiding correct medication. This paper reported Al3+ and gold nanoclusters (AuNCs) templated with glutathione for quantifying CIP with ratio-fluorescence analysis. Al3+ caused the aggregation of AuNCs that had the property of aggregation-induced emission, so the orange fluorescence of AuNCs was observed to sharply increase with Al3+ exposure. With adding CIP to coordinate with Al3+, AuNCs displayed decreased orange fluorescence due to the disaggregation, and the instinct blue fluorescence of CIP was also observed. The probe exhibited outstanding detection stability because of the ratiometric response, and could avoid the analyte-independent interference. It also displayed rapid response and excellent sensitivity during the detection of CIP. The response allowed to be completed within 1 min, and CIP even as low as 1.4 nM could be detected. Moreover, the application in urine revealed that the spiked recoveries of the probe were between 91.2 % and 103.6 %. Overall, this paper exploits a fluorescent probe for highly stable, rapid and sensitive determination of CIP through Al3+-enhanced fluorescence of AuNCs. [ABSTRACT FROM AUTHOR]

• Stimulus-responsive MOF@AuNP was designed as a low-background scattering signal probe. • Seed-mediated gold in situ growth strategy was used to amplify the scatting signal. • The proposed DLS immunosensor exhibited a high sensitivity for AFP detection with a LOD of 0.36 pg/mL. • The AuNP@MOF combined metal growth amplification showed a great potential for enhancing DLS signal. The ultrasensitive detection of disease-related biomarkers is critical to improving the early diagnosis, monitoring, and treatment of diseases. Herein, we reported a dynamic light scattering (DLS)-based immunosensor for the high-sensitivity detection of alpha-fetoprotein (AFP), an important biomarker in the early diagnosis of primary liver cancer. A metal–organic framework and gold nanoparticle composite (MOF@AuNP) was designed as a low-background scattering signal probe. After its structure was decomposed in a weak alkaline solution, the numerous small-sized AuNPs (∼4 nm) were released from the MOF structure. Controllable gold in situ growth strategy without self-nucleation was then executed to increase the AuNP size. Owing to the double signal amplification of the burst release of numerous small-sized AuNPs from MOFs and the gold in situ growth for an enhanced AuNP size, the proposed DLS immunosensor was successfully applied for the ultrasensitive detection of AFP with the detection limit of 0.36 pg mL−1. The reliability of the proposed method was evaluated by analyzing 22 actual clinic serum samples, and the results were further verified by the chemiluminescence immunosensor. This work features MOF@AuNP and the gold in situ growth amplified modulation of DLS-based signal transduction, which demonstrates the great potential as a novel bioanalytical platform for a myriad of purposes. [ABSTRACT FROM AUTHOR]

• A fluorescent probe was rationally designed for inorganic phosphate detection. • The mechanism was based on uranine release from uranine@ZIF-8 composite. • The probe possessed facial synthesis, fast response and excellent sensitivity. • The probe was successfully applied to analyzing inorganic phosphate in urine. A fluorescent probe for inorganic phosphate (Pi) was rationally designed. The probe was constructed by loading uranine in zeolitic imidazolate framework-8 (ZIF-8), during which aggregation-caused quenching occurred. In the presence of Pi, uranine was released owing to the decomposition of ZIF-8, thus leading to fluorescence enhancement. The probe was facilely prepared by a one-step method at room temperature, and possessed a fast response of 3 min and a low detection limit of 0.2 μM. It was further applied to the detection of Pi in urine, and satisfactory recoveries were obtained (93.5–96.0%). This work not only develops an effective tool for Pi detection but also proposes a new strategy to design fluorescent probes for Pi. [ABSTRACT FROM AUTHOR]