Search

A novel microfluidic paper-based colorimetric sensor for the detection of bisphenol A (BPA) was developed based on the intrinsic peroxidase activity of ZnFe 2 O 4 magnetic nanoparticles (ZnFe 2 O 4 MNPs) and the adsorption capacity of molecularly imprinted polymer (MIP) membranes. In the process, ZnFe 2 O 4 MNPs and cellulose fibers in paper were wrapped by MIP membranes (ZnFe 2 O 4 @MIP membranes) successfully. Novel MIP membranes for the recognition of BPA were prepared in polar solvent using acrylamide as the functional monomer and BPA as the template by bulk polymerization, which resulted in a new type of BPA imprinted polymer membranes. Adsorption isotherms model of MIP membranes was employed to describe the isotherms, and maximum adsorption capacity was evaluated. In the presence of 3,3′,5,5′-tetramethylbenzidine (TMB), the as-prepared ZnFe 2 O 4 MNPs peroxidase mimetics was used to catalyze chromogenic reactions and showed the color with respective intensity. Under optimized conditions, the grey intensity was found to be proportional to the BPA concentrations in the range of 10 nM–1000 nM (R 2 = 0.9945) with a detection limit of 6.18 nM. With the advantages of highly reproducible response, good selectivity and excellent regeneration, the colorimetric sensor holds great potential for portable detection of targets in environmental monitoring, security inspection and complicated matrices. [ABSTRACT FROM AUTHOR]

A chemiluminescent (CL) excited photoelectrochemical (PEC) immunosensor for detection of carcinoembryonic antigen (CEA) was introduced into microfluidic paper-based analytical devices (μ-PADs) integrated with a paper supercapacitor (PS) amplifier, and a terminal digital multi-meter (DMM) detector, based on CdS/TiO 2 hybrid modified porous Au-paper electrode. The effective matching of energy levels between the conduction bands of CdS and TiO 2 allowed for fast electron injection from excited CdS to TiO 2 upon irradiation, which inhibited the recombination process of electron–hole pairs and prompted PEC performance. Using CEA/ABEI-AuNPs-GOx bioconjugates as signal labels which featured CEA, N-(aminobutyl)-N-(ethylisoluminol) (ABEI) and glucose oxidase (GOx) linked to Au nanoparticles for signal amplification could greatly enhance the sensitivity. GOx could catalyze glucose to produce H 2 O 2 , which acted as a co-reactant in the ABEI-AuNPs-H 2 O 2 - p -iodophenol (PIP) CL system as well as sacrificial electron donor to scavenge the photogenerated holes in the valence band of CdS QDs, further causing an enhanced photocurrent. The quantification mechanism of this strategy is based on the charging of this PS by the photocurrent. The generated photocurrent could be stored by the PS and released instantaneously through a low cost, portable, and simple DMM to obtain an amplified current for the quantification of CEA. Under the optimal conditions, this analytical platform could detect CEA at concentrations at picomole level. This work offers a new route to highly selective and sensitive detection of biologically important small molecules. [ABSTRACT FROM AUTHOR]

• Exciton-plasmon interactions gated self-checking functional PEC system was developed. • A BiVO 4 -BP p-n heterojunction was explored. • Exciton-plasmon interactions triggered energy transfer between BiVO 4 -BP and Au NPs. • Dual-signal output guarantees accuracy. Current photoelectrochemical (PEC) sensing system usually suffers from false-positive readout caused by the environmental factor. Herein, a PEC sensing platform with wide spectrum responsive based on exciton-plasmon interactions gated energy transfer between photoelectrode and Au NPs was designed for ultrasensitive detection of adenosine by coupling with self-checking function. Specifically, 2D black phosphorus (BP) nanosheets sensitized nanoporous BiVO 4 (BiVO 4 -BP) acted as photoelectrode could harness light from ultraviolet to near infrared and accelerate charge separation, thus obviously promoted PEC performance. The detection mechanism was designed by controlling exciton-plasmon interaction on the influence of energy transfer between photoelectrode and dispersed Au NPs. Taking advantage of the disaggregation of Au NPs aggregates upon the addition of adenosine, which leads to a shift in the plasmonic band of the Au NPs accompanied by a color change of the solution from blue to purplish red enables a naked-eye readout semiquantitation of the adenosine. Meanwhile, the plasmonic shift gates the photocurrent response of photoelectrode for accurate quantitation of the adenosine exposure ranged from 0.1 nM to 1 μM with acceptable reliability. Enabled by the unique mechanism, this approach provides a new horizon for designing multi-functional PEC sensing platform. [ABSTRACT FROM AUTHOR]

Herein, a CRISPR/Cas12a-mediated photoelectrochemical (PEC) biosensor based on entropy-driven catalysis (EDC) cycle amplification technology was presented for identification of miRNA-21. On the one hand, sensitizer methylene blue (MB) was introduced by double-strand DNA (H1-H2) on the electrode modified by ZnIn 2 S 4 nanoflowers and CdS quantum dots (QDs), which further optimized initial photocurrent. On the other hand, compared with traditional work, the two single strands generated by EDC cycle triggered by miRNA-21 were fully utilized, the problem of low utilization of EDC cycle products was cleverly solved and the multiple signal amplification with simpler operation was realized by combining with CRISPR/Cas12a. A signal strand S1 generated by EDC cycle made the MB-labeled single strand (H2-MB) bend into a hairpin structure to approach electrode, maximizing the PEC signal. Another signal strand S2 formed a ternary complex with CRISPR/Cas12a to activate the trans-cleavage characteristics, the MB-labeled hairpin structure was cut randomly, which made MB left electrode to significantly reduce the signal, realizing sensitive identification of miRNA-21. The designed PEC biosensor presented a satisfactory linear relationship within the scope of 10 fM-100 nM, and detection line as low as 1.5 fM, supplying a new idea in biomarkers assay and disease diagnosis. • The ZnIn 2 S 4 /CdS QDs composites nanomaterial provided strong photocurrent signal. • Entropy-driven catalysis cycle products were sufficiently utilized to amplify the signal. • CRISPR/Cas12a system improved the selectivity and sensitivity of the PEC biosensor. [ABSTRACT FROM AUTHOR]

The hybrids, N -aminobutyl- N -ethylisoluminol (ABEI), horseradish peroxidase (HRP) and cancer antigen 125 s antibody (Ab2) immobilized graphene oxide (GO), were prepared, which exhibited excellent chemiluminescence (CL) activity. The zinc oxide nanorods (ZNRs) grew on reduced graphene oxide (RGO) modified paper working electrode (ZNRs-RGO/PWE) via an in situ growth method. The deposition of CdS quantum dots (QDs) on ZNRs/RGO-PWE resulted in an enhanced excitation and photo-to-electric conversion efficiency. The ABEI-GO@HRP/Ab2CL system was employed as an internal excited light source. A photoelectrochemical (PEC) immunosensor based on CdS-sensitized ZNRs anchored RGO as the photoactive matrix and ABEI-GO@HRP/Ab2 as the CL labels was established for sensitive detection of cancer antigen 125 (CA 125). As a model, sandwich CA 125-antibody was taken as molecular reorganization elements on this sensor for the sensitive determination of CA 125 in the linear range from 5.0 × 10 −4 U/mL to 500 U/mL with a detection limit of 2.0 × 10 −4 U/mL. The specificity, reproducibility, and stability of this sensor were also investigated. This proposed method might be attractive for clinical and biomedical applications. [ABSTRACT FROM AUTHOR]

• A dual-mode lab-on-paper device for ultrasensitive electrochemical/visual sensing of miRNA-155. • Synthesis of Cu/Co double-doped CeO 2 nanospheres with abundant oxygen vacancies as signal probes. • DNA-functionalized nanomaterial complexes were used as electrochemical probes for amplification strategies. • The device has high sensitivity, stability and selectivity. In this work, an ultrasensitive lab-on-paper device via Cu/Co double-doped CeO 2 (CuCo-CeO 2) nanospheres as signal amplifiers, being acquiescent to quantitative assay with the dual mode signal readout of electrochemical and visual screening, was constructed for ultrasensitive sensing of miRNA-155. To improve the performance of biosensor, an Au-modified paper-based working electrode was manufactured by a secondary in-situ growth method, thereby enhancing its conductivity and facilitating the modification of hairpin probe with miRNA-155 through Au-S bonds. For constructing the lab-on-paper device, CuCo-CeO 2 nanospheres were introduced as signal amplifiers, which exhibited remarkable enhanced performance in catalyzing H 2 O 2 to generate ·OH to achieve electrochemical signal amplification compared with CeO 2 , and further improved the sensitivity of the lab-on-paper device. By combining hybridization chain reaction and classic competitive recognition interaction mechanism between aptamers and targets, ultrasensitive detection of miRNA-155 based on the lab-on-paper device was achieved. Meanwhile, color reaction could be realized on account of the oxidation of 3,3′5,5′-tetramethylbenzidine in the presence of H 2 O 2 with the help of CuCo-CeO 2 , thereby achieving dual mode signal output. Under optimal conditions, a low detection limit of 0.05 fM with a linear range of 0.1 fM–10 nM for sensing miRNA-155 was reached by electrochemical method. And the low detection limit of 4.89 fM was obtained by visual method with a linear range of 10 fM–10 nM. The proposed lab-on-paper device was also successfully applied in serum samples to detect miRNA-155. [ABSTRACT FROM AUTHOR]