Xiuzhong Wang

Layered Double Hydroxide Functionalized Textile for Effective Oil/Water Separation and Selective Oil Adsorption

The removal of oil and organic pollutants from water is highly desired due to frequent oil spill accidents, as well as the increase of industrial oily wastewater. Here, superhydrophobic and superoleophilic textile has been successfully prepared for the application of effective oil/water separation and selective oil adsorption. This textile was fabricated by functionalizing the commercial textile with layered double hydroxide (LDH) microcrystals and low surface energy molecules. The LDH microcrystals were immobilized on the microfibers of the textile through an in situ growth method, and they formed a nestlike microstructure. The combination of the hierarchical structure and the low surface energy molecules made the textile superhydrophobic and superoleophilic. Further experiments demonstrated that the as-prepared textile not only can be applied as effective membrane materials for the separation of oil and water mixtures with high separation efficiency (>97%), but also can be used as a bag for the selective oil adsorption from water. Thus, such superhydrophobic and superoleophilic textile is a very promising material for the application of oil spill cleanup and industrial oily wastewater treatment.

Enzyme-free and label-free fluorescence aptasensing strategy for highly sensitive detection of protein based on target-triggered hybridization chain reaction amplification.

Proteins are of great importance in medical and biological fields. In this paper, a novel fluorescent aptasensing strategy for protein assay has been developed based on target-triggered hybridization chain reaction (HCR) and graphene oxide (GO)-based selective fluorescence quenching. Three DNA probes, a helper DNA probe (HP), hairpin probe 1 (H1) and hairpin probe 2 (H2) are ingeniously designed. In the presence of the target, the aptamer sequences in HP recognize the target to form a target-aptamer complex, which causes the HP conformation change, and then triggers the chain-like assembly of H1 and H2 through the hybridization chain reaction, generating a long chain of HP leading complex of H1 and H2. At last the fluorescence indicator SYBR Green I (SG) binds with the long double strands of the HCR product through both intercalation and minor groove binding. When GO was added into the solutions after HCR, the free H1, H2 and SG would be closely adsorbed onto GO surface via π-π stacking. However, the HCR product cannot be adsorbed on GO surface, thereby the SG bound to HCR product gives a strong fluorescence signal dependent on the concentration of the target. With the use of platelet-derived growth factor BB (PDGF-BB) as the model analyte, this newly designed protocol provides a highly sensitive fluorescence detection of PDGF-BB with a limit of detection down to 1.25 pM, and also exhibit good selectivity and applicability in complex matrixes. Therefore, the proposed aptasensing strategy based on target-triggered hybridization chain reaction amplification should have wide applications in the diagnosis of genetic diseases due to its simplicity, low cost, and high sensitivity at extremely low target concentrations.

Highly sensitive homogeneous electrochemical aptasensor for antibiotic residues detection based on dual recycling amplification strategy.

The ubiquitous presence of antibiotic residues in foodstuff have serious health consequences for consumers from allergic reactions to the evolution of antibiotic-resistant bacteria. To address this problem, a novel homogeneous electrochemical aptasensor with high sensitivity and specificity is designed for antibiotic residues detection based on target-induced and T7 exonuclease-assisted dual recycling signal amplification strategy. It was realized by the remarkable diffusivity difference between hairpin probe and the mononucleotides towards the negatively charged indium tin oxide electrode. For the proof-of-concept experiment, ampicillin, was employed as a model analyte to examine the desirable properties of this assay. A low detection limit of 4.0pM toward ampicillin with an excellent selectivity could be achieved, which has been successfully applied to assay antibiotic in milk. Whats more, compared with the immobilization-based electrochemical means, the proposed sensing system avoids the tedious and time-consuming steps of electrode modification, making the experimental processes much simpler and more convenient. With the advantages of high sensitivity, excellent selectivity and simple operation, it is believed that this strategy possesses great potential for the simple, easy and convenient detection of antibiotic residues in food safety field.

Autonomous Exonuclease III-Assisted Isothermal Cycling Signal Amplification: A Facile and Highly Sensitive Fluorescence DNA Glycosylase Activity Assay

One common form of DNA damage is the oxidation of guanine to 8-oxo-7,8-dihydroguanine (8-oxoG), which can be carcinogenic. Human 8-oxoguanine DNA glycosylase (hOGG1) is a key base excision repair (BER) enzyme that repairs 8-oxoG, and the expression level of hOGG1 is closely related to many types of human cancers. Herein, a novel and highly sensitive fluorescence biosensing platform for hOGG1 activity detection has been constructed based on autonomous exonuclease III (Exo III)-assisted signal amplification. Two hairpin probes (HP1 and HP2) are ingeniously designed. In the presence of hOGG1, HP1 is cleaved at the 8-oxoG site, and the stem is subsequently digested by Exo III, releasing the trigger DNA fragment (tDNA1). Successively, tDNA1 partially hybridizes with HP2 to initiate the Exo III-assisted cycling cleavage to release another trigger DNA fragment (tDNA2), which in turn triggers the cycling cleavage of DNA fluorescence probe (FP). Therefore, large amount of fluorophore fragments are released, leading to a significantly amplified fluorescence signal toward hOGG1 activity detection. A directly measured detection limit down to 0.001 U/mL is obtained, which is much lower than that of the approaches reported in literature. In addition to high sensitivity and good selectivity, the as-proposed strategy also exhibits the advantages of isothermal experimental condition, simplicity, and convenience. Furthermore, the Exo III-assisted autonomous cycling cleavage approach we proposed here is a universal sensing strategy and has great potential in assays of many other biological analytes.

Label-free colorimetric detection of coralyne utilizing peroxidase-like split G-quadruplex DNAzyme

A simple design of a label-free colorimetric sensor for coralyne was demonstrated, which is based on the coralyne-modulated peroxidase-like split G-quadruplex (split G4) DNAzyme via A2–coralyne–A2 coordination. In the present work, two specific oligonucleotide strands were used. Upon addition of coralyne, it could specifically bind to A18 sequences with an apparent binding constant of 1.05 × 105 M−1, which induced the formation of an anti-parallel homo-adenine duplex, accompanied by the proximity of two G-rich sequences responsible for the formation of split G4. In the presence of hemin, this split G4 was able to catalyze the H2O2-mediated oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic-acid) diammonium salt (ABTS–H2O2 system), resulting in a maximal absorbance at approximately 420 nm. A linear response from 0.06 to 10 μM was obtained for coralyne, with a linear correlation coefficient of 0.9987. The detection limit was estimated to be 19 nM based on a S/N of 3.

Selective and colorimetric detection of pyruvic acid using conformational switch of i-motif DNA and unmodified gold nanoparticles

A novel, highly selective and colorimetric strategy for pyruvic acid (PA) detection is proposed based on the conformational change of i-motif DNA and the salt-induced aggregation effects of unmodified gold nanoparticles. The addition of PA can induce the C-rich DNA to fold into a rigid close-packed i-motif DNA, which accordingly loses its ability to effectively protect and stabilize AuNPs from salt-induced aggregation. In the presence of pyruvate decarboxylase (PDC), PA can be efficiently converted to acetaldehyde and CO2 through nonoxidative decarboxylation, causing the solution pH to change from acidic to neutral. Thus, the C-rich DNA can still maintain its extended single strand status and can effectively stabilize the AuNPs from salt-induced aggregation. The absorbance difference before and after the addition of PDC depends on the concentration of PA and can be used for the quantitative determination of PA. The developed colorimetric sensor can achieve PA detection with a linear range from 5.6 × 10−6 M to 1.68 × 10−4 M and a detection limit of 3.0 μM. The as-established colorimetric strategy opens a new avenue for the specific detection of DNA conformation-responsive small biomolecules.

Fluorescent and colorimetric dual-mode aptasensor for thrombin detection based on target-induced conjunction of split aptamer fragments

Since the lack of detection diversity of the single-signal readout strategy, it is urgent to develop fast and multisignal assay strategies. A highly selective and sensitive assay method with colorimetric and fluorometric dual signals readouts is presented in this paper. It is based on the principle that the target induced conjunction of split aptamer fragments assembled on the surface of Au nanoparticles (AuNPs). In the presence of targets, the color of solution changed from wine red to blue and can be measured both visual inspection and spectrophotometry because of the aggregation of AuNPs. At the same time, the report probes which are original hybrid with the anchoring aptamer fragments on the AuNPs surface can be released and recovers the fluorescence. By use of this detection strategy, the limit of detection for thrombin (TMB), as a model of analyte, were 0.45 and 0.16nM, respectively. Furthermore, this protocol can discriminate TMB from other analogue with high selectivity and can be used to detect TMB in human serum samples. The results came from the two signals were well consistent with each other, which demonstrated that it has application potential for detection of TMB in complex matrix.