A double-conducting polymer nanowire-based electrochemical aptasensor for highly sensitive and low fouling detection of cortisol in saliva.

A cortisol biosensor was developed based on double-conducting polymer nanowires, which exhibits excellent conductivity, resistance to biological contamination, and outstanding sensing performance. The biosensor employs dual-mode electrochemical techniques, namely, differential pulse voltammetry (DPV) and chronoamperometry (CA), for the sensitive and low fouling detection of the glucocorticoid hormone cortisol. Experimental results demonstrated that the linear detection range of the biosensor in DPV mode was 1.0 × 10-14-1.0 × 10-8 M, with a detection limit of 0.131 × 10-14 M. In CA mode, the biosensor exhibited a detection range of 1.0 × 10-13-1.0 × 10-7 M and a detection limit of 0.313 × 10-13 M. The biosensor was successfully utilized for the rapid detection of cortisol in human saliva. The combination of a high-specificity cortisol aptamer and functionalized double-conducting polymer nanowires ensured the exceptional specificity and sensitivity of the biosensor in detecting real biological samples.

Electrochemical determination of acetamiprid using PEDOT sensing coating functionalized with carbon quantum dots and Prussian blue nanoparticles.

A dual-mode electrochemical biosensor for acetamiprid detection was proposed for the first time based on carbon quantum dots/Prussian blue (CQDs/PB)-functionalized poly(3,4-ethylenedioxythiphene) (PEDOT) nanocomposite. The nanocomposite with spherical stacking nanostructure showed high surface area, excellent catalytic ability, and cycling stability. The biosensor can be effortlessly constructed after the immobilization of acetamiprid aptamer. The concentration of acetamiprid can be determined by differential pulse voltammetry (DPV) based on its signal change deduced from the pristine PB. With the capture of acetamiprid, the response current (I-T) signal generated by hydrogen peroxide catalysis from the biosensor can also been used to establish the method for monitoring acetamiprid. The dual-mode biosensor showed a wide linear range from 10-12 g mL-1 to 10-6 g mL-1, low detection limits of 6.84 × 10-13 g mL-1 and 4.99 × 10-13 g mL-1, and ultrafast detection time of 25 s and 5 s through DPV and I-T mode, respectively. The biosensor possessed excellent selectivity and stability. More importantly, the biosensor was successfully applied to detect acetamiprid residues in vegetables, proving a promising approach for routine detection of pesticide in real samples. The biosensor based on PEDOT/CQDs/PB for acetamiprid can be effortlessly constructed through both the increase of differential pulse voltammetry (DPV) signal change deduced by the pristine PB and the decrease of the response current (I-T) signal of the reduction of hydrogen peroxide catalyzed by PEDOT/CQDs/PB.

Electrochemical assay of acetamiprid in vegetables based on nitrogen-doped graphene/polypyrrole nanocomposites.

Dual-mode electrochemical aptasensor based on nitrogen-doped graphene (NG) doped with the conducting polymer polypyrrole (PPy) nanocomposite is proposed for the determination of acetamiprid. NG/PPy was electrodeposited onto the glassy carbon electrode (GCE) using cyclic voltammetry technique. NG/PPy/GCE showed outstanding electrocatalytic activity for the oxidation of nitrite due to "active region" induced by the charge redistribution of carbon atoms. The ultrasensitive dual-mode biosensor for acetamiprid could be easily developed by coupling acetamiprid aptamers with the NG/PPy hybrid. The specific binding between acetamiprid and the aptamers resulted in the increase of differential pulse voltammetry (DPV) signal change and the decrease of chronoamperometry (CA) signal, and the concentration of acetamiprid could be measured. The working potentials of DPV and CA were - 0.2 ~ 0.4 V and - 0.4 ~ 0.4 V (vs. SCE), respectively. The dual-mode acetamiprid biosensor showed a wide linear range from 10-12 to 10-7 g mL-1, with low detection limits of 1.15 × 10-13 g mL-1 and 7.32 × 10-13 g mL-1 through DPV and CA modes, respectively. Moreover, owing to high active area and superior conductivity, as well as good electrocatalytic ability, the dual-sensing platform based on NG/PPy nanocomposite supported the quantification of acetamiprid in complex samples. A dual-mode electrochemical aptasensor based on NG/PPy nanocomposite for acetamiprid detection was proposed through both the increase of differential pulse voltammetry (DPV) signal change and the decrease of chronoamperometry (CA) signal of the nitrite oxidation electrocatalyzed by NG/PPyn in sensors and biosensors.

Highly selective and antifouling electrochemical biosensors for sensitive MicroRNA assaying based on conducting polymer polyaniline functionalized with zwitterionic peptide.

Ultrasensitive and low-fouling microRNA electrochemical biosensors were successfully constructed by introducing thiol-terminated antifouling molecules (peptide sequence, polyethylene glycol, or mercapto alcohol) onto the surface of polyaniline-modified electrodes. For the three kinds of antifouling materials investigated, the newly designed and synthesized peptide exhibited superior antifouling ability to others, and it could effectively reduce the nonspecific adsorption of proteins and even prevent the fouling effect of serum. Compared with microRNA biosensors without antifouling capability, or those modified with polyethylene glycol or mercapto alcohol, the biosensor modified with the designed zwitterionic peptide showed the highest specificity for single-base mismatch, three-base mismatch, and completely complementary microRNAs. Most interestingly, the experimental results indicated that the introduction of antifouling molecules to the sensing interfaces did not significantly change the sensitivity of the biosensor. The strategy of constructing antifouling biosensors based on newly synthesized zwitterionic peptides and conducting polymers can be promisingly extended to the development of other electrochemical sensors and biosensors without encountering biofouling. Graphical abstract Ultrasensitive and low-fouling microRNA electrochemical biosensors were constructed by introducing thiol-terminated antifouling molecules (peptide sequence, polyethylene glycol, or mercapto alcohol) onto the surface of polyaniline-modified electrodes. The biosensor modified with the designed zwitterionic peptide showed the highest specificity amongst four kinds of biosensors.

A sensitive and label-free electrochemical microRNA biosensor based on Polyamidoamine Dendrimer functionalized Polypyrrole nanowires hybrid.

The potential of functionalized polypyrrole nanowires (PPyNWs) are demonstrated as a platform for lable-free miRNA detection using electrochemical impedance spectroscopy (EIS). MicroRNAs (miRNAs) detection methods and sensors are mainly challenged by very low concentrations in physiological samples and high similarity among family members. Herein, a sensitive and selective miRNA biosensor was constructed based on electrochemically synthesized PPyNWs, which were functionalized with polyamidoamine dendrimer (PAMAM) by an electro-oxidation method. The prepared PPyNWs/PAMAM hybrid combines the excellent electrical conductivity of conducting polymer PPyNWs with high surface to volume ratio of PAMAM. DNA probes were immobilized onto the PPyNWs/PAMAM hybrid for the construction of the miRNA biosensor. Using the sensitive EIS technique to monitor DNA/miRNA hybridization, the developed biosensor demonstrated excellent sensing performances, such as wide linear range (10-14 M-10-8 M) and low detection limit (0.34 × 10-14 M). Even more encouraging, the response sensitivity of the biosensor was 3.12 times higher than that of the bulk PPy-modified sensor, which proved that the microstructure of the PPy nanowires array can greatly improve the performance of the biosensor. An ultrasensitive and selective miRNA biosensor was constructed based on electrochemically synthesized polypyrrole nanowires array (PPyNWs), which were functionalized with polyamidoamine dendrimer (PAMAM) by an electro-oxidation method.

Electrochemical sensor based on Prussian blue/multi-walled carbon nanotubes functionalized polypyrrole nanowire arrays for hydrogen peroxide and microRNA detection.

A dual-sensing platform is proposed based on multi-walled carbon nanotubes/Prussian blue-functionalized polypyrrole nanowire array (PPY/MWCNTs/PB). Highly aligned PPY nanowire arrays were electrochemically prepared on the surface of glassy carbon electrodes, which were doped with MWCNTs/PB nanocomposites. The nanomaterial combines the characteristics of the PPY nanowires (high conductivity and large specific surface area) and MWCNTs/PB (excellent catalytic performance and intrinsic redox activity). Owing to the nanowire microstructure and outstanding electrical properties, the PPY/MWCNTs/PB nanowire arrays show excellent electrocatalysis of the reduction of hydrogen peroxide and facilitate the construction of a high-performance biosensing platform for microRNA (miRNA). A linear relationship between analytical signal and concentration of hydrogen peroxide and miRNA was obtained in the range 5 to 503 µM (1.4-5.1 mM) and 0.1 pM to 1 nM, and detection limits of 1.7 µM and 33.4 fM, respectively. This new supersensitive sensing platform has broad application prospects of biomolecule and other analyte determination in drug, biomedical, plant protection, and environmental analysis. Prussian blue/multi-walled carbon nanotubes functionalized polypyrrole nanowire arrays (PPY/MWCNTs/PB) were prepared by a facile one-step electrochemical method. PPY/MWCNTs/PB nanowire arrays show excellent electrocatalysis of the reduction of H2O2 and facilitate the construction of a high-performance biosensing platform for microRNA.

Highly Thermally Stable, Green Solvent Disintegrable, and Recyclable Polymer Substrates for Flexible Electronics.

Flexible electronics require its substrate to have adequate thermal stability, but current thermally stable polymer substrates are difficult to be disintegrated and recycled; hence, generate enormous electronic solid waste. Here, a thermally stable and green solvent-disintegrable polymer substrate is developed for flexible electronics to promote their recyclability and reduce solid waste generation. Thanks to the proper design of rigid backbones and rational adjustments of polar and bulky side groups, the polymer substrate exhibits excellent thermal and mechanical properties with thermal decomposition temperature (Td,5% ) of 430 °C, upper operating temperature of over 300 °C, coefficient of thermal expansion of 48 ppm K-1 , tensile strength of 103 MPa, and elastic modulus of 2.49 GPa. Furthermore, the substrate illustrates outstanding optical and dielectric properties with high transmittance of 91% and a low dielectric constant of 2.30. Additionally, it demonstrates remarkable chemical and flame resistance. A proof-of-concept flexible printed circuit device is fabricated with this substrate, which demonstrates outstanding mechanical-electrical stability. Most importantly, the substrate can be quickly disintegrated and recycled with alcohol. With outstanding thermally stable properties, accompanied by excellent recyclability, the substrate is particularly attractive for a wide range of electronics to reduce solid waste generation, and head toward flexible and "green" electronics.

A dual-mode electrochemical biosensor based on GO-Fe3O4 doped PEDOT nanocomposite for the ultrasensitive assay of microRNA.

MicroRNA, as a distinctive biomarker, plays a crucial role in the early prognosis and diagnosis of numerous severe diseases. However, due to its inherent properties such as low abundance, small size, and high sequence similarity, the sensitive and accurate detection of microRNA remains a major challenge. Herein, a dual-mode electrochemical biosensing platform was developed for microRNA detection, based on poly(3,4-ethylenedioxythiophene) (PEDOT) doped with graphene oxide-Fe3O4 (GO-Fe3O4) nanocomposite. The GO-Fe3O4/PEDOT composite demonstrated a porous microstructure, outstanding conductivity, and robust catalytic activity towards nitrite. It was electrodeposited onto the electrode surface in a one-step process using the cyclic voltammetry method (CV). The microRNA biosensor was obtained by anchoring DNA with amino groups to the GO-Fe3O4/PEDOT layer through the formation of amide bonds. The designed dual-mode microRNA biosensor demonstrated a broad linear range spanning from 10-15 M to 10-6 M, with low detection limits of 5.18 × 10-15 M and 7.36 × 10-15 M when using chronocoulometry (CC) and amperometric i-t curve (i-t) modes, respectively. Furthermore, a dual-mode electrochemical biosensor has been successfully developed and utilized for the detection of microRNA in human serum, demonstrating its potential for precise and sensitive microRNA detection and its practical application value in clinical medicine.

A low fouling electrochemical biosensor based on the zwitterionic polypeptide doped conducting polymer PEDOT for breast cancer marker BRCA1 detection.

The application of polypeptides in bio-interfaces and biosensors is of great interest because polypeptides are biocompatible and easy to design. A novel polymer nanocomposite was prepared by the electropolymerization of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) with a newly designed polypeptide. The nanocomposite polypeptide doped PEDOT (PEDOT/PEP), with a 3D microporous network structure, large surface area and excellent antifouling ability, was utilized for the attachment of BRCA1 complementary oligonucleotides to construct a DNA biosensor. The fabricated DNA biosensor showed favorable selectivity (with a detection limit of 0.0034 pM) and high sensitivity. The biosensor was also capable of detecting the target DNA (BRCA1) in 1% (V/V) human serum samples. The combination of a conducting polymer PEDOT with an antifouling and biocompatible polypeptide demonstrates a new method for preparing electrochemical sensors, that are capable of detecting targets in complex biological samples without strong nonspecific protein adsorption.

Zwitterionic poly(carboxybetaine) functionalized conducting polymer polyaniline nanowires for the electrochemical detection of carcinoembryonic antigen in undiluted blood serum.

Biocompatible materials, such as zwitterionic poly(carboxybetaine methacrylate) (polyCBMA), are of extraordinary importance in growth of bioelectronics and biosensors, because they not only greatly suppress nonspecific protein adsorption, but also have rich functional groups to facilitate the fixation of biological molecules. A novel nanocomposite was synthesized herein through modification polyCBMA onto conducting polymer polyaniline (PANI) nanowire surface. The prepared polyCBMA/PANI composite, integrating the good conductivity of PANI nanowires with the excellent antifouling capability of polyCBMA, provided a wonderful matrix for the growth of ultrasensitive and low fouling biosensor. Carcinoembryonic antigen (CEA), an important biomarker for a variety of cancers, was utilized as a model test. Furthermore its antibody was fixed onto polyCBMA/PANI for the preparation of CEA biosensor. DPV was applied as a sensing principle with information at which peak potential and current the signals were recorded. The peak currents were in inverse proportion to the logarithm of CEA concentration in the range from 1.0×10-14gmL-1 to 1.0×10-10gmL-1, with a detect limit of 3.05fgmL-1. Furthermore, this low fouling, label-free biosensor has been utilized for assaying in undiluted human serum samples with resisting serious nonspecific protein adsorption, demonstrating its feasible potential application in clinical analysis of CEA.

Mechanism of formation of intravertebral clefts in osteoporotic vertebral compression fractures: An in vitro biomechanical study.

BACKGROUND CONTEXT: Intravertebral clefts (IVCs) are vacuum-like cavities commonly associated with osteoporotic vertebral compression fractures (OVCFs). IVCs promote cement leakage during kyphoplasty, suggesting a physical link with the basivertebral foramen, although this is uncertain. PURPOSE: The present study aims to create IVCs in mechanical experiments on cadaveric spines in order to clarify their pathogenesis, structure, and links with the basivertebral foramen. STUDY DESIGN AND METHODS: In total, 15 three-vertebra lumbar specimens from five cadavers aged 68 to 71 years were subjected to axial compressive overload followed by cyclic loading in flexion and extension to create an OVCF together with an IVC. Computed tomography scans and radiographs were used to confirm structural changes and micro-CT was used to measure trabecular bone properties in five specimens. Unipedicular vertebroplasty was then performed on 10 damaged specimens until fluoroscopy revealed extravasation of cement. RESULTS: In every specimen, loading created an OVCF with an IVC. Dissection and imaging showed that the IVC was always connected with the basivertebral foramen. The central vertebral region, including the IVC, had the lowest connectivity density, trabecular number, and bone volume fraction, and the highest trabecular separation. Vertebroplasty caused cement leakage through the basivertebral foramen in nine specimens and into an adjacent disc in one specimen. CONCLUSION: Cyclic loading in flexion and extension applied to a fractured osteoporotic vertebra can create an IVC, which then allows cement leakage via the basivertebral foramen.

A simple multi-well stretching device to induce inflammatory responses of vascular endothelial cells.

We herein introduce a novel multi-well stretching device that is made of three polydimethylsiloxane layers, consisting of a top hole-punched layer, middle thin membrane, and bottom patterned layer. It is the first time that such a simple device has been used to supply axisymmetric and nonuniform strains to cells cultured on well bottoms that are stretchable. These mechanical stimuli can somewhat mimic the stretching at the bending sites of blood vessels, where the strains are complicated. In this device, nonuniform strain is given to cells through the deformation of a membrane from a flat surface to a spherical cap during the injection of a certain volume of water into the chamber between the middle membrane and bottom layer. EA.hy926 cells (a human umbilical vein endothelial cell line) were seeded on the well bottoms and exposed to axisymmetric strain under a 5, 10, 15, and 20% degree of deformation of the membrane. The cellular responses were characterized in terms of cell morphology, cell viability, and expression of inflammatory mRNAs and proteins. With increasing the degree of deformation, the cells exhibited an inclination toward detachment and apoptosis; meanwhile the expression of inflammatory mRNAs and proteins, such as MCP-1, IL-8, IL-6 and ICAM-1, showed a significant increment. The obtained results demonstrate that the inflammatory responses of EA.hy926 cells can be induced by increasing the magnitude of the strain. This simple device provides a useful tool for in vitro investigation of the inflammatory mechanisms related to vascular diseases.

Facile synthesis of ultrasmall monodisperse "raisin-bun"-type MoO3/SiO2 nanocomposites with enhanced catalytic properties.

We report the preparation of ultrasmall monodisperse MoO3/SiO2 nanocomposites in reverse microemulsions formed by Brij-58/cyclohexane/water. The nanocomposites are of "raisin-bun"-type with 1.0 ± 0.2 nm MoO3 homogeneously dispersed in 23 ± 2 nm silica spheres. Characterization is carried out based on transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrometry (EDS), X-ray powder diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES), N2 sorption measurement, and NH3 temperature-programmed desorption (NH3-TPD). The as-prepared MoO3/SiO2 nanocomposites are microporous and exhibit enhanced catalytic activities for acetalization of benzaldehyde with ethylene glycol and can be repeatedly used 5 times without obvious deactivation. The catalytic performance improvement is attributed to the unique structure and ultrasmall size of the nanocomposites.

Exposure to secondhand smoke outside of a bar and a restaurant and tobacco exposure biomarkers in nonsmokers.

BACKGROUND: With an increase in indoor smoking bans, many smokers smoke outside establishments and near their entrances, which has become a public health concern. OBJECTIVES: We characterized the exposure of nonsmokers to secondhand smoke (SHS) outside a restaurant and bar in Athens, Georgia, where indoor smoking is banned, using salivary cotinine and urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). METHODS: In a crossover study, we assigned 28 participants to outdoor patios of a restaurant and a bar and an open-air site with no smokers on three weekend days; participants visited each site once and stayed for 3 hr. We collected saliva and urine samples immediately before and after the visits (postexposure) and on the following morning and analyzed samples for cotinine and total NNAL, respectively. Regression models were fitted and changes in biomarkers were contrasted between locations. RESULTS: Postexposure and preexposure geometric mean salivary cotinine concentrations differed by 0.115 ng/mL [95% confidence interval (CI): 0.105, 0.126)] and by 0.030 ng/mL (95% CI: 0.028, 0.031) for bar and restaurant visits, respectively. There were no significant post- and preexposure differences in cotinine levels after control site visits, and changes after bar and restaurant site visits were significantly different from changes after control site visits (p < 0.001). Results comparing next-day and preexposure salivary cotinine levels were similar. Next-day creatinine-corrected urinary NNAL concentrations also were higher than preexposure levels following bar and restaurant visits [1.858 pg/mg creatinine higher (95% CI: 0.897, 3.758) and 0.615 pg/mg creatinine higher (95% CI: 0.210, 1.761), respectively], and were significantly different from changes after the control visits (p = 0.005). CONCLUSION: Salivary cotinine and urinary NNAL increased significantly in nonsmokers after outdoor SHS exposure. Our findings indicate that such exposures may increase risks of health effects associated with tobacco carcinogens.