Zhaoxia Wang

Enhanced Charge Transfer by Gold Nanoparticle at DNA Modified Electrode and Its Application to Label-Free DNA Detection

Rational utilization of nanomaterials to construct electrochemical nucleic acid sensors has attracted large attention in recent years. In this work, we systematically interrogate the interaction between gold nanoparticles (GNPs) and single-strand DNA (ssDNA) immobilized on an electrode surface and then take advantage of the ultrahigh charge-transfer efficiency of GNPs to develop a novel DNA sensing method. Specifically, ssDNA modified gold electrode can adsorb GNPs because of the interaction between gold and nitrogen-containing bases; thus, the negative electrochemical species [Fe(CN)6](3-/4-) may transfer electrons to electrode through adsorbed GNPs. In the presence of target DNA, the formed double-strand DNA (dsDNA) cannot capture GNPs onto the electrode surface and the dsDNA may result in a large charge-transfer resistance owing to the negatively charged phosphate backbones of DNA. So a simple but sensitive method for the detection of target DNA can be developed by using GNPs without any requirement of modification. Experimental results demonstrate that the electrochemical method we have proposed in this work can detect as low as 1 pM breast cancer gene BRCA1 in a 10 μL sample volume without any signal amplification process or the involvement of other synthesized complex, which may provide an alternative for cancer DNA detection. This method may also be generalized for detecting a spectrum of targets using functional DNA (aptamer, metal-specific oligonucleotide, or DNAzyme) in the future.

Assembly of Selective Biomimetic Surface on an Electrode Surface: A Design of Nano–Bio Interface for Biosensing

In nature, cellular molecule sensing is usually achieved at the environment/membrane interface. In the meantime, rapid growth of nanotechnology is increasingly pushing engineered nanomaterials to interact with biological surfaces. Herein, inspired by trans-membrane signal transduction, a nano-bio interface has been constructed in this work for biosensing application. The interface is formed between a selective biomembrane mimetic surface (SBMMS) and a function-oriented 2D nanohybrid. Based on the design, target recognition can be performed in a biologically favorable environment, and the nano-bio interaction can be transduced into amplified electrochemical readouts. Furthermore, this sensing platform can be used to analyze various kinds of targets, including proteins, nucleic acids, and small molecules, just by changing the biorecognition element. Low detection limits and wide detection ranges can also be obtained. So, this nano-bio interface may provide a new platform for bioanalytical research in the future.

Lignin binding to pancreatic lipase and its influence on enzymatic activity

In this paper, we find that the effect of lignin on pancreatic lipase (PL) is dependent on reaction medium and substrate used. Experimental results reveal that lignin can gradually bind to PL to form a PL-lignin complex, resulting in an increased activity of the enzyme. The binding process is spontaneous and the PL-lignin complex formation is an endothermic reaction induced by hydrophobic and electrostatic interaction. There is a non-radiation energy transfer from PL to lignin during the binding process, and the binding of lignin to PL conforms to a secondary exponential decay function. Moreover, the α-helix content of the enzyme will be changed and the rigidity of its side chain will be enhanced due to the formation of lignin-PL complex. This study has not only provided the activation effect of lignin on PL, but also given an insight into the interaction between lignin and the enzyme, which would benefit the application of lignin in the pharmacy and food industry, as well as other fields.

An array-based approach to determine different subtype and differentiation of non-small cell lung cancer.

Simple and accurate methods of discriminating subtype or differentiation of human tumor are critical for designing treatment strategies and predicting disease prognosis, and the currently used method to determine the two important factors mainly depends on histological examination by microscopy observation, which is laborious, highly trained operator required, and prone to be disruptive due to individual-to-individual judgment. Here we report a novel array-based method based on the interaction of graphene oxide (GO) and single-strand DNA modified gold nanoparticles (ssDNA-AuNPs) to distinguish between different subtypes and grades of tumors through their overall intracellular proteome signatures. Strategically, we first select eight proteins at 0.5 nM concentration in buffer or 10 nM in human serum to verify the discriminant ability of our method, then choose adenocarcinoma and squamous-cell carcinoma that account for 90% non-small cell lung cancer, as well as their respective three tumor grades as model system to provide a realistic testing ground for clinical cancer analysis. Consequently, total differentiation between different subtype and grade of tumor tissues has been achieved with as little as 100 ng of intracellular protein, suggesting the high sensitivity and selectivity of this sensor array. Overall, this array-based approach may provide the possibility for unbiased and simplified personalized tumor classification diagnostics in the future.

Detection of Tumor Invasive Biomarker using a Peptamer of Signal Conversion and Signal Amplification

Inspired by the structural and functional features of proteins in cell signaling, a switchable peptide is designed in this work. This switchable peptide is named a peptamer, and it can react to ligand binding with conformational change and activation/deactivation of catalytic ability. The peptamer is constructed by elaborately integrating several different peptide motifs with targeting and catalytic abilities. Thus, targeted binding of the peptamer to an integrin can be regulated by a synthetic ligand. Moreover, the conformational rearrangement of the peptamer induced by both integrin and the synthetic ligand can resolve in altered affinity of the peptamer for a catalytic cofactor, cupric ion. This leads to greatly contrasted efficiency of catalysis in the presence/absence of integrin. This distinct switching on/off of catalytic activity also enables a bioassay of tissue integrin expression in clinical samples of thyroid carcinoma. Experimental results reveal that the detected integrin level parallels the state of lymph node metastasis. Therefore, this simple peptide model may help to understand the structural reconfiguration of proteins involved in cellular signal transduction, as well as to provide a new means to assess protein activity under pathological conditions such as cancer.

Integration of chemoselective ligation with enzymespecific catalysis: Saccharic colorimetric analysis using aminooxy/hydrazine-functionalized gold nanoparticles

Here we developed a saccharic colorimetric method based on the combination of chemoselective ligation and enzyme-specific catalysis using aminooxy/hydrazine-functionalized gold nanoparticles (AO/AuNPs or H/AuNPs). In the detection of galactose (Gal), galactohexodialdose (GHDA), the galactose oxidase (GalOx)-catalyzed product, has an aldehyde group, which allows it to chemoselectively react with an aminooxy or hydrazine group at the outer layer of AO/AuNPs or H/AuNPs by oxime/hydrazone click chemistry to form oxime or hydrozone. Consequently, through the specific recognition of 1,4-phenylenediboronic acid (PDBA) on cis-diols, GHDA, which contains two pairs of hydroxyls in the cis form, can bind not only with AO/AuNPs or H/AuNPs, but also with PDBA to form boronate diester, thereby triggering the aggregation of AuNPs and causing the corresponding color change. As GalOx catalyzed specific substrates, the amount of Gal correlated with the production of GHDA and the extent of AuNPs aggregation, thus allowing a simple and easily operatable colorimetric method for Gal detection to be developed. Under the optimized experimental conditions, the ratios of absorbance at a wavelength of 617 nm to that at 536 nm vary linearly with the logarithmic values of Gal concentrations within a wide range of 500 nM to 5 mM. Moreover, this colorimetric method shows anti-interference capability and high sensitivity with a detection limit of 21 nM. Thus, a universal platform for accurate and specific colorimetric analysis can be established through the integration of chemoselective ligation with enzyme specific catalysis.

Investigation of MTH1 activity via mismatch-based DNA chain elongation

Accumulation and misincorporation of oxidative damaged 8-oxo-7,8-dihydroguanine triphosphates (8-oxo-dGTP) in genomic DNA may cause serious cellular function disorders. MutT Homolog 1 (MTH1), a protein enzyme that can help to prevent 8-oxo-dGTP misincorporation, plays critical roles in oxidative stress neutralization, oncogene-associated tumor malignancy, and anticancer therapies. So, in this work, a simple and function-oriented method is developed for the assay of MTH1 activity. Specifically, a mismatch-based (8-oxoG: A mismatch) DNA chain elongation strategy (MB-DCE) is firstly proposed to reveal the misincorporation efficiency of 8-oxo-dGTP. Then, further coupled with the inherent activity of MTH1 to prevent 8-oxo-dGTP misincorporation, a relationship can be established to reveal the activity of MTH1 through MB-DCE. As the method is designed directly towards the cellular function of MTH1, activity of MTH1 in different breast cancer cell lines has been detected, implying the potential application of this assay method for biomedical research and clinical diagnose in the future.

Colorimetric determination of islet amyloid polypeptide fibrils and their inhibitors using resveratrol functionalized gold nanoparticles

AbstractThe article describes the preparation of gold nanoparticles functionalized with resveratrol (Res-AuNPs) in a single step and by integrating synthesis and modification. By using Res-AuNPs, we have established a colorimetric method for the determination of fibrillar islet amyloid polypeptides (IAPP) and its inhibitors. It is based on the specific recognition of resveratrol by IAPP fibrils. This results in a decrease in the concentration of Res-AuNPs in the supernatant and a corresponding reduction in absorbance at 537xa0nm. This finding was exploited to design a simple and sensitive colorimetric assay for IAPP fibrils. The analytical range extends from 30 to 400xa0μM, and the limit of detection is as low as 1.2xa0μM. In addition,xa0the inhibitory effects of caffeic acid and caffein on the formation of fibrillar IAPP were evaluated. The method is simple and effective, and therefore is perceived to represent a promising scheme for determination of fibrillar IAPPs and their inhibitors.n Graphical AbstractSchematic of the colorimetric determination of islet amyloid polypeptides (IAPP) fibrils based on the interaction between resveratrol-modified gold nanoparticles (Res-AuNPs) and IAPP.

Electrochemical biosensor for the nuclear factor kappa B using a gold nanoparticle-assisted dual signal amplification method

AbstractNuclear factor kappa B (NF-κB) is a transcription factor that plays a central role in the signaling pathway and network of gene regulation. The dysregulation of NF-κB signaling has been implicated in the pathogenesis of a number of diseases. We report on a dual amplification strategy for the highly sensitive electrochemical sensing of NF-κB by means of a nicking endonuclease-assisted amplification reaction (NEAR). The quantity of the DNA obtained is subsequently determined by applying a gold nanoparticle-assisted electrochemical amplification step. This represents the first example of a combination of NEAR and a dual amplification strategy for the detection of a transcription factor. Experimental results show that the electrochemical signal generated by the redox probe (the ruthenium(III) hexammine complex) can be related to the concentration of NF-κB. The response of the electrode is linearly related to the concentration of NF-κB in the 100xa0pM to 10xa0nM range, with a detection limit as low as 80xa0pM.n FigureAn electrochemical biosensor for NF-κB with dual signal amplification is achieved. It was based on nicking endonuclease-assisted amplification reaction (NEAR) and gold nanoparticle-assisted electrochemical amplification (AuNP-EA). The method can be extended for the detection of universal DNA-binding proteins.

Amperometric low potential aptasensor for the fucosylated Golgi protein 73, a marker for hepatocellular carcinoma

AbstractThe fucosylated Golgi protein 73 (fuc-GP73) has been used as a criterion to distinguish hepatocellular carcinoma (HCC) from other chronic liver diseases. We describe an amperometric aptasensor for ultrasensitive detection of fuc-GP73 that uses a thiolated aptamer against GP73 as the capture probe, and gold nanoparticles (AuNPs) modified with Avidinlens culinaris agglutinin (A-LCA) as the detection probe. The AuNPs on the surface of a gold electrode provide a large surface for immobilization of A-LCA, so that they can be heavily loaded with biotinylated horse radish peroxidase (B-HRP) via avidin-biotin interactions. This results in enhanced analytical sensitivity. Under optimized conditions and a typical working potential as low as 48xa0mV (vs. SCE), the dynamic response of the electrode covers the 10xa0pg·mL−1 to 25xa0ng·mL−1 fuc-GP73 concentation range, with a 7xa0pg·mL−1 detection limit (for an S/N ratio of 3). The assay is precise, selective and reproducible. It was applied to the determination of fuc-GP73 in serum.n Graphical abstractSchematic of an electrochemical aptasensor for the determination of fucosylated golgi protein 73 (fuc-gp73) based on the avidin-Lens culinaris agglutinin (A-LCA) and biotinylated horse radish peroxidase (B-HRP). It was applied to serum analysis with good sensitivity, selectivity and reproducibility.