Cuisong Zhou

Development of a Fast and Sensitive Glucose Biosensor Using Iridium Complex-Doped Electrospun Optical Fibrous Membrane

Polystyrene electrospun optical fibrous membrane (EOF) was fabricated using a one-step electrospinning technique, functionalized with glucose oxidases (GOD/EOF), and used as a quick and highly sensitive optical biosensor. Because of the doped iridium complex, the fibrous membrane emitted yellow luminescence (562 nm) when excited at 405 nm. Its luminescence was significantly enhanced with the presence of extremely low concentration glucose. The detection limit was of 1.0 × 10(-10) M (S/N = 3), superior to that of reported glucose biosensor with 1.2 × 10(-10) M. A linear range between the relative intensity increase and the logarithm of glucose concentration was exhibited from 3.0 × 10(-10) M to 1.3 × 10(-4) M, which was much wider than reported results. Notably, the response time was less than 1 s. These high sensitivity and fast response were attributed to the high surface-area-to-volume of the porous fibrous membrane, the efficient GOD biocatalyst reaction on the fibers surface, as well as the fast electron or energy transfer between dissolved oxygen and the optical fibrous membrane.

Target-catalyzed autonomous assembly of dendrimer-like DNA nanostructures for enzyme-free and signal amplified colorimetric nucleic acids detection.

Self-assembly of DNA nanostructures is of great importance in nanomedicine, nanotechnology and biosensing. Herein, a novel target-catalyzed autonomous assembly pathway for the formation of dendrimer-like DNA nanostructures that only employing target DNA and three hairpin DNA probes was proposed. We use the sticky-ended Y shape DNA (Y-DNA) as the assembly monomer and it was synthesized by the catalyzed hairpin assembly (CHA) instead of the DNA strand annealing method. The formed Y-DNA was equipped with three ssDNA sticky ends and two of them were predesigned to be complementary to the third one, then the dendrimer-like DNA nanostructures can be obtained via an autonomous assembly among these sticky-ended Y-DNAs. The resulting nanostructure has been successfully applied to develop an enzyme-free and signal amplified gold nanoparticle (AuNP)-based colorimetric nucleic acids assay.

Ultrasensitive Visual Detection of HIV DNA Biomarkers via a Multi-amplification Nanoplatform

Methodologies to detect disease biomarkers at ultralow concentrations can potentially improve the standard of living. A facile and label-free multi-amplification strategy is proposed for the ultrasensitive visual detection of HIV DNA biomarkers in real physiological media. This multi-amplification strategy not only exhibits a signficantly low detection limit down to 4.8 pM but also provides a label-free, cost-effective and facile technique for visualizing a few molecules of nucleic acid analyte with the naked eye. Importantly, the biosensor is capable of discriminating single-based mismatch lower than 5.0 nM in human serum samples. Moreover, the visual sensing platform exhibits excellent specificity, acceptable reusability and a long-term stability. All these advantages could be attributed to the nanofibrous sensing platform that 1) has a high surface-area-to-volume provided by electrospun nanofibrous membrane, and 2) combines glucose oxidase (GOx) biocatalysis, DNAzyme-catalyzed colorimetric reaction and catalytic hairpin assembly (CHA) recycling amplification together. This multi-amplification nanoplatform promises label-free and visual single-based mismatch DNA monitoring with high sensitivity and specificity, suggesting wide applications that range from virus detection to genetic disease diagnosis.

Target-triggered autonomous assembly of DNA polymer chains and its application in colorimetric nucleic acid detection

A novel target-triggered DNA autonomous assembly pathway for the formation of one-dimensional DNA polymer chains was proposed based on the catalyzed hairpin assembly and sticky end self-assembly, which led to an enzyme-free and signal amplified gold nanoparticle (AuNP) based colorimetric nucleic acid assay with picomolar sensitivity and specificity.

An enhanced chemiluminescence bioplatform by confining glucose oxidase in hollow calcium carbonate particles

A chemiluminescence (CL) amplification platform based on HCC/Lucigenin&GOx (HLG) film was developed. Hollow structural calcium carbonate (HCC) particles were used as alternative materials for carrying both enzyme and CL reagent. The model enzyme (GOx), immobilized in confined space of HCC particles, exhibited an improved biocatalysis. The Michaelis constant (Km) and the enzymatic rate constant (kcat) were determined to be 0.209 μM and 2.21 s−1, respectively, which are much better than those of either free GOx in aqueous solution or the GOx immobilized on common nanomaterials. Based on the HLG platform, CL signal was effectively amplified and visualized after adding trace glucose, which could be attributed to the HCC particles’ high biocompatibility, large specific surface area, attractive interfacial properties and efficient interaction with analyses. The visual CL bioplatform showed an excellent performance with high selectivity, wide linear range and low detection limit for sensing trace glucose. Because it eliminates the need of complicated assembly procedure and enables visualization by the naked eye, the sensitive and selective CL bioplatform would provide wide potential applications in disease diagnosis and food safety.

An electrochemiluminescence amplification strategy: a synergistic effect of electrospun Ru(bpy)32+/CNT/ionic liquid composite nanofibers

Electrospun Ru(bpy)32+/carbon nanotube (CNT)/room temperature ionic liquid (IL: 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6)) composite polyacrylonitrile (PAN) nanofibers (CNT/IL/PAN) were successfully fabricated by a one-step electrospinning technique. Utilizing high binding capacity of both carboxylic acid functionalized multiwalled CNTs and large structure anion PF6− (derived from BMIMPF6) to Ru(bpy)32+, the composite nanofibers can serve as an excellent Ru(bpy)32+ immobilization nanomatrix for electrochemiluminescence (ECL) sensing. Using electrochemistry and fluorescence techniques, the composite nanofibers demonstrated superior electron transfer capability and ECL significant amplification. These results might be attributed to a synergistic effect between CNTs and ILs which both have unique electronic and catalytic properties. The ECL intensity from the composite nanofibers was 23.4-fold larger than that of PAN nanofibers, 1.7-fold greater than CNT/PAN nanofibers, and 2.4-fold greater than IL/PAN nanofibers. Furthermore, the composite nanofibers exhibited the largest ECL quenching efficiency, 8.2 times more than that of the PAN nanofibers in the presence of the same phenol concentration (20 μM). Moreover, a nanofiber-based ECL sensor has great selectivity, stability and reusability. In a word, an ECL sensor based on the CNT/IL/PAN nanofibers was developed to sensitively detect phenolic compounds with a low detection limit of 1.0 nM for phenols. A novel ECL amplification strategy based on the synergistic effect between doped CNTs and doped ILs within nanofibers was demonstrated and developed to a promising ECL sensing nanoplatform for ultrasensitive and fast detection.

Self-assembly of DNA nanoparticles through multiple catalyzed hairpin assembly for enzyme-free nucleic acid amplified detection

It is known that DNA molecules can be used to build a various of complicated geometrical DNA nanostructures with programmable sequence design, and these DNA nanomaterials show a promising application in biotechnology and biomedicine. However, the construction of large-sized three dimensional DNA-based nanomaterials still remains a challenge. In this work, we propose a new strategy that only employs one target DNA to trigger multiple catalyzed hairpin assembly (CHA) reactions and sticky ends self-assembly to prepare hundreds of nanometer-sized DNA nanoparticles. Moreover, the obtained DNA nanoparticles can be served as efficient biosensors for sensitive colorimetric nucleic acids detection with a detection limit of 7.7pM.

Facile and fast fabrication of polyaniline nanorods on acidized titanium foils with a synergistic effect for electrochemical sensing

A facile method to quickly construct polyaniline nanorods (PANI-NR) on acidized titanium (Ti) foils was reported. In this strategy, the acidized Ti foils (Ti-ac) can act as nucleation sites for controllable growth of PANI-NR. Attributed to the synergistic effect of the PANI-NR, doped CNTs and Ti-ac, the PANI-NR/CNT/Ti-ac composite exhibited decreased redox potential and improved electron transport capability. PANI-NR/CNT/Ti-ac was used as an excellent platform for electrochemically sensing ascorbic acid (AA). At a low AA concentration range from 0.4 μM to 125 μM (R2 = 0.998), a high sensitivity of 281 μA mM-1 cm-2 was obtained. The detection limit of AA was 80 nM at a signal-to-noise ratio of 3, which was better than that of reported PANI microtubes (280 nM), PANI nanoparticles (8.3 μM) and PANI film/PAA/MWCNTs (250 nM). A strategy for fabricating the PANI-NR/CNT composite on Ti-ac was provided and the improved electrochemical performance suggests promising application of PANI-NR/CNT/Ti-ac as a sensing platform.

Insight into How Telomeric G-Quadruplexes Enhance the Peroxidase Activity of Cellular Hemin

The toxic oxidative damage of G-quadruplexes (G4), linked to neurodegenerative diseases, may arise from their ability to bind and oxidatively activate cellular hemin. However, there have been no precise studies on how telomeric G4 enhances the low intrinsic peroxidase activity of hemin. Herein, a label-free and nanopore-based strategy was developed to explore the enhancement mechanism of peroxidase activity of hemin induced by telomeric G4 (d(TTAGGG)n ). The nanopore-based strategy demonstrated that there were simultaneously two different binding modes of telomere G4 to hemin. At the single-molecule level, it was found that the hybrid structural telomeric G4 directly binds to hemin (the affinity constant (Ka )≈106  m-1 ) to form a tight complex, and some of them underwent a topological change to a parallel structure with an enhancement of Ka to approximately 107  m-1 . Through detailed analysis of the topology and peroxidase activity and molecular modeling investigations, the parallel telomere G4/hemin DNAzyme structure was proven to be preferable for high peroxidase activity. Upon strong π-π stacking, the parallel structural telomere G4 supplied a key axial ligand to the hemin iron, which accelerated the intermediate compound formation with H2 O2 in the catalytic cycle. Our studies developed a label-free and single-molecule strategy to fundamentally understand the catalytic activity and mechanism of telomeric DNAzyme, which provides some support for utilizing the toxic, oxidative-damage property in cellular oxidative disease and anticancer therapeutics.

Simultaneous Discrimination of Single-Base Mismatch and Full Match Using a Label-Free Single-Molecule Strategy

Identification of single-base mismatches has found wide applications in disease diagnosis, pharmacogenetics, and population genetics. However, there is still a great challenge in the simultaneous discrimination of single-base mismatch and full match. Combined with a nanopore electrochemical sensor, a shared-stem structure of molecular beacon was designed that did not need the labeling, but achieved an enhanced signal-to-background ratio of ∼104, high thermodynamic stability to bind with target sequences, and a fast hybridization rate. Fully matched and single-base mismatched sequences were simultaneously discriminated at the single-molecule level, which is expected to have potential applications ranging from the quick detection, early clinical diagnostics to point-of-care research.