Polyhedral-AuPd nanoparticles-based dual-mode cytosensor with turn on enable signal for highly sensitive cell evalution on lab-on-paper device

Ultrasensitive Microfluidic Paper-Based Electrochemical Biosensor Based on Molecularly Imprinted Film and Boronate Affinity Sandwich Assay for Glycoprotein Detection

In this work, we proposed a strategy that combined molecularly imprinted polymers (MIPs) and hybridization chain reaction into microfluidic paper-based analytical devices for ultrasensitive detection of target glycoprotein ovalbumin (OVA). During the fabrication, Au nanorods with a large surface area and superior conductibility were grown on paper cellulosic fiber as a matrix to introduce a boronate affinity sandwich assay. The composite of MIPs including 4-mercaptophenylboronic acid (MPBA) was able to capture target glycoprotein OVA. SiO₂@Au nanocomposites labeled MPBA and cerium dioxide (CeO₂)-modified nicked DNA double-strand polymers (SiO₂@Au/dsDNA/CeO₂) as a signal tag were captured into the surface of the electrode in the presence of OVA. An electrochemical signal was generated by using nanoceria as redox-active catalytic amplifiers in the presence of 1-naphthol in electrochemical assays. As a result, the electrochemical assay was fabricated and could be applied in the detection of OVA in the wide linear range of 1 pg/mL to 1000 ng/mL with a relatively low detection limit of 0.87 pg/mL (S/N = 3). The results indicated that the proposed platform possessed potential applications in clinical diagnosis and other related fields.

Visual distance readout to display the level of energy generation in paper-based biofuel cells: application to enzymatic sensing of glucose

Biofuel cells (BFCs) based on anodic oxidation and cathodic oxygen reduction represent an attractive alternative to self-powered devices. A glucose/oxygen BFC is described for monitoring glucose. It is making use of a piece of paper carrying a glucose oxidase (GOx) based bioanode, and a bilirubin oxidase (BilOx) based biocathode. The performance of the BFC is affected by the generation of H₂O₂, a byproduct of enzymatic glucose oxidation. Therefore, the removal of H₂O₂ is a crucial step in terms of BFC performance and stability. In addition, direct, unambiguous visual read-out is an ideal way to provide quantitative information. The colorimetric readout system described here is based on the consumption of undesired H₂O₂ and to convert the extent of energy generation into recognizable variations in color. As the H₂O₂ travels along the hydrophilic channel by capillary action, the formation of red gold nanoparticles from AuCl₄^- leads to the appearance of a red bar that provides distance-based information that can be read visually. The multiply readable information (maximum power density of BFC or visible distance) provides further choices for quantification. It also enhances reliability. The self-powered system based on the BFC exhibits excellent performance. Glucose can be determined by this method in the 1 to 50 mM concentration range. Graphical abstract Schematic presentation of a paper-supported biofuel cell equipped with a visual distance readout to display the level of energy generation in biofuel cells, and its application in sensing of glucose.

A novel ultrasensitive electrochemiluminescence biosensor for glutathione detection based on poly-L-lysine as co-reactant and graphene-based poly(luminol/aniline) as nanoprobes

In this work, an ultrasensitive electrochemiluminescence (ECL) biosensor was constructed using poly-L-lysine (PLL) as a novel co-reactant of luminol and poly(luminol/aniline) nanorods loaded reduced graphene oxide (PLA@rGO) as nanoprobe, which enable highly sensitivity detection of glutathione (GSH). To the best of our knowledge, it is the first time that PLL was used for the co-reactant of luminol. Notably, about a 5-fold enhancement was obtained compared with the individual PLA@rGO using GCE. Due to the remarkable quenching effect between the excited state of PLL and the reduced form of GSH in the ECL system of luminol/PLL, the ECL sensing platform exhibited wide linear ranges of 1.0 × 10^-9-1.0 × 10^-4 M and 1.0 × 10^-4-1.0 × 10^-2 M and a low detection limit of 7.7 × 10^-10 M. Simultaneously, the biosensor was also successfully applied to detect GSH in human serum sample with high recoveries. Hence, this work would open a new platform for the wide application of PLL in immunoassay and various sensors.

Sensitivity enhancement of cloth-based closed bipolar electrochemiluminescence glucose sensor via electrode decoration with chitosan/multi-walled carbon nanotubes/graphene quantum dots-gold nanoparticles

In this work, a novel facile closed bipolar electrochemiluminescence (C-BP-ECL) sensor has been developed for highly sensitive detection of glucose based on the integration of chitosan (CS), poly(diallyldimethylammonium chloride)-functioned multi-walled carbon nanotubes (PDDA-MWCNTs) and graphene quantum dots-gold nanoparticles (GQDs-AuNPs) on the wax/carbon ink-screen-printed cloth-based device. When CS, PDDA-MWCNTs and GQDs-AuNPs are successively decorated onto the cathode of closed bipolar electrode (C-BPE), the C-BPE anode can emit much stronger C-BP-ECL signals. Moreover, the cathodic decoration of the C-BPE can generate a stronger ECL signal in comparison with its anodic decoration. Under optimized conditions, glucose can be detected in the range of 0.1-5000 μM, and the limit of detection is estimated to be 64 nM, which is about three orders of magnitude lower than that in case of the bare C-BPE cathode (31 μM). It has been shown that the proposed sensor has high detection sensitivity, wide dynamic range, and as well acceptable reproducibility, selectivity and stability. Finally, the applicability and validity of the C-BP-ECL sensor are demonstrated for the detection of glucose in human serum samples. We believe that this novel highly-sensitive sensor will have potential applications in various areas such as clinical diagnosis, food analysis and environmental monitoring.

A dual-aptamer-based biosensor for specific detection of breast cancer biomarker HER2 via flower-like nanozymes and DNA nanostructures

A dual-aptamer electrochemical biosensor based on flower-like nanozymes and DNA nanostructures was fabricated for detection of breast cancer biomarker HER2.

A facile DNA strand displacement reaction sensing strategy of electrochemical biosensor based on N-carboxymethyl chitosan/molybdenum carbide nanocomposite for microRNA-21 detection

Herein, we report a facile enzyme-free microRNA (miRNA) target-triggered strand displacement reaction (SDR) amplification strategy with ferrocene (Fc) as a signal molecule to fabricate a two-dimensional electroactive molybdenum carbide (Mo₂C)-based biosensor. In the presence of miRNA-21, SDR was initiated and many hairpin DNA1 (HDNA1) and hairpin DNA2 (HDNA2) duplexes, which could be captured by probe DNA leading the Fc-modified HDNA2 close to the electrode surface, were produced continuously. MiRNA-21 could be detected by monitoring the redox signal of Fc. The prepared N-carboxymethyl chitosan/Mo₂C nanocomposite featured excellent conductivity, great dispersion, and multiple functional groups (amine groups). When the nanocomposite was introduced to a miRNA biosensor electrode interface to ensure its strong connection to the DNA probe, the developed miRNA-21 biosensor demonstrated a reliable linear range of 1.0 fM to 1.0 nM with a detection limit of 0.34 fM and showed good selectivity, reproducibility, and stability. The biosensor was employed to detect miRNA-21 in human serum samples, and it showed great potential in the early clinical diagnosis of various genetic diseases.

A chemiluminescence aptasensor for thrombin detection based on aptamer-conjugated and hemin/G-quadruplex DNAzyme signal-amplified carbon fiber composite

In this work, a highly sensitive and selective chemiluminescence (CL) aptasensor was prepared for thrombin (THR) detection based on aptamer-conjugated and hemin/G-quadruplex DNAzyme signal-amplified carbon fiber composite (HG-DNAzyme/T-Apt/SiO₂@GO@CF). Initially, SiO₂@GO@CF was successfully prepared and characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). Thrombin aptamer (T-Apt) as an identification element and simulated enzyme - hemin/G-quadruplex DNAzyme (HG-DNAzyme) as a signal-amplified material, were applied in the CL aptasensor. Then, the immobilization properties of SiO₂@GO@CF and adsorption properties of T-Apt/SiO₂@GO@CF were studied. Lastly, HG-DNAzyme/T-Apt/SiO₂@GO@CF was applied in construction of the CL aptasensor. When THR existed, HG-DNAzyme was desorbed from the surface of T-Apt/SiO₂@GO@CF and catalyzed the CL system of luminol-H₂O₂. Under optimized CL conditions, THR was measured with the linear concentration range of 1.5 × 10^-14 to 2.5 × 10^-11 moL/L and the detection limit of 6.3 × 10^-15 moL/L (3δ). The proposed CL aptasensor was used to the determination of THR in human serum samples and recoveries ranged from 99.0% to 102.4%. Those satisfactory results illustrated the CL aptasensor could achieve highly sensitive and selective detection of THR and revealed potential application in practical samples.

Double signal amplification based on palladium nanoclusters and nucleic acid cycles on a μPAD for dual-model detection of microRNAs

Dual-model signal outputs and double signal amplification on the platform of μPAD for the sensitive detection of miRNAs.