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.

Improved antifouling properties of photobioreactors by surface grafted sulfobetaine polymers.

To improve the antifouling (AF) properties of photobioreactors (PBR) for microalgal cultivation, using trihydroxymethyl aminomethane (tris) as the linking agent, a series of polyethylene (PE) films grafted with sulfobetaine (PE-SBMA) with grafting density ranging from 23.11 to 112 µg cm-2 were prepared through surface-initiated atom transfer radical polymerization (SI-ATRP). It was found that the contact angle of PE-SBMA films decreased with the increase in the grafting density. When the grafting density was 101.33 µg cm-2, it reached 67.27°. Compared with the PE film, the adsorption of protein on the PE-SBMA film decreased by 79.84% and the total weight of solid and absorbed microalgae decreased by 54.58 and 81.69%, respectively. Moreover, the transmittance of PE-SBMA film recovered to 86.03% of the initial value after cleaning, while that of the PE film recovered to only 47.27%. The results demonstrate that the AF properties of PE films were greatly improved on polySBMA-grafted surfaces.

Microparticle entrapment for drug release from porous-surfaced bone implants.

Metallic bone implants face interfacial concerns, such as infection and insufficient bone formation. Combination of drug-loaded microparticles with the implant surface is a promising approach to reducing the concerns. The present study reports a simple method for this purpose. Drug-loaded chitosan and alginate microparticles were separately prepared by emulsion methods. Dry microparticles were introduced into porous titanium (Ti) coatings on Ti discs, and induced to agglomerate in pores by wetting with water. Agglomerates were stably entrapped in the pores: 77-82% retained in the coating after immersion in a water bath for 7 d. Discs carrying drug-loaded microparticles showed a rapid release within 6 h and a subsequent slow release up to 1 d. After coculture with Staphylococcus epidermidis for 24 h, the discs formed inhibition zones, confirming antibacterial properties. These suggest that the microparticle entrapment-based method is a promising method for reducing some of the bone-implant interfacial concerns.

Facile fabrication of cellulose-based hydrophobic paper via Michael addition reaction.

The inherent highly hydrophilic feature of cellulose-based paper hinders its application in many fields. Herein, a cellulose-based hydrophobic paper was fabricated based on surface chemical modification. Firstly, the hydrophobic acrylate components were bonded to the cellulose acetoacetate (CAA) fibers to obtain CAA graft acrylate (CAA-X) fibers through Michael addition reaction. Subsequently, CAA-X fibers were processed into paper via wet papermaking technology. The resulting paper exhibited good hydrophobic performance (water contact angle was up to 135°) with an air permeability of 24.8 µm/Pa·s. The hydrophobicity of paper was very stable and remained even after treating with different solvents. Moreover, the hydrophobic properties of this paper could be adjusted by changing the type of acrylate component. It should be noted that the surface modification strategy has no obvious effects on the whiteness (79.8%), writing, and printing properties of the cellulose fibers. Thus, it is a simple, benign, and efficient strategy for the construction of cellulose-based hydrophobic paper, which has great potential to be used in paper tableware, oil-water separation, watercolor protection, and food packaging fields.

Engineering of stepwise-targeting chitosan oligosaccharide conjugate for the treatment of acute kidney injury.

Acute kidney injury (AKI) is a common and serious clinical syndrome of acute renal dysfunction in a short period. One of therapeutic interventions for AKI is to reduce ROS massively generated in the mitochondria and then ameliorate cell damage and apoptosis induced by oxidative stress. In this study, stepwise-targeting chitosan oligosaccharide, triphenyl phosphine-low molecular weight chitosan-curcumin (TPP-LMWC-CUR, TLC), was constructed for sepsis-induced AKI via removing excessive ROS in renal tubular epithelial cells. Benefiting from good water solubility and low molecular weight, TLC was rapidly and preferentially distributed in the renal tissues and then specifically internalized by tubular epithelium cells via interaction between Megalin receptor and LMWC. The intracellular TLC could further delivery CUR to mitochondria due to high buffering capacity of LMWC and delocalized positive charges of TPP. Both in vitro and in vivo pharmacodynamic results demonstrated the enhanced therapeutic effect of TLC in the treatment of AKI.

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.

Biguanide-Derived Polymeric Nanoparticles Kill MRSA Biofilm and Suppress Infection In Vivo.

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of drug-resistant infections. Its propensity to develop biofilms makes it especially resistant to conventional antibiotics. We present a novel nanoparticle (NP) system made from biocompatible F-127 surfactant, tannic acid (TA), and biguanide-based polymetformin (PMET) (termed FTP NPs), which can kill MRSA biofilm bacteria effectively in vitro and in vivo and which has excellent biocompatibility. FTP NPs exhibit biofilm bactericidal activity-ability to kill bacteria both inside and outside biofilm-significantly better than many antimicrobial peptides or polymers. At low concentrations (8-32 µg/mL) in vitro, FTP NPs outperformed PMET with ∼100-fold (∼2 log10) greater reduction of MRSA USA300 biofilm bacterial cell counts, which we attribute to the antifouling property of the hydrophilic poly(ethylene glycol) contributed by F-127. Further, in an in vivo murine excisional wound model, FTP NPs achieved 1.8 log10 reduction of biofilm-associated MRSA USA300 bacteria, which significantly outperformed vancomycin (0.8 log10 reduction). Moreover, in vitro cytotoxicity tests showed that FTP NPs have less toxicity than PMET toward mammalian cells, and in vivo intravenous injection of FTP NPs at 10 mg/kg showed no acute toxicity to mice with negligible body weight loss and no significant perturbation of blood biomarkers. These biguanide-based FTP NPs are a promising approach to therapy of MRSA infections.

Three new species, one new genus and subfamily of Dorylaimida (de Man, 1876) Pearse, 1942, and revisions on the families Tylencholaimellidae Jairajpuri, 1964 and Mydonomidae Thorne, 1964 (Nematoda: Dorylaimida).

Three new species of the order Dorylaimida (de Man, 1876) Pearse, 1942 were identified and described. Paratylencholaimus sanshaensis gen. nov. sp. nov. from Hainan is proposed as a new member of the family Tylencholaimellidae Jairajpuri, 1964. Paratylencholaimus gen. nov. is close to Phellonema Thorne, 1964 and Goferus Jairajpuri & Ahmad, 1992 but can be differentiated mainly by having basal part of odontophore rod-like and without knobs, and basal part of pharynx expanded gradually. Tylencholaimus zhongshanensis sp. nov. from Guangdong and Dorylaimoides shapotouensis sp. nov. from the Ningxia Hui Autonomous Region are also described herein. Phylogenetic analyses based on the 18S rDNA and the D2-D3 region of the 28S rDNA support that the three new species are valid. The classifications of the families Tylencholaimellidae and Mydonomidae Thorne, 1964 are revised mainly based on the analysis of the morphology of odontostyle and odontophore. After these revisions, Paratylencholaiminae subfam. nov. including Paratylencholaimus gen. nov. and Goferus is proposed. Athernema and Agmodorus of Tylencholaimellidae are transferred into Mydonomidae, and the subfamily Athernematinae of Tylencholaimellidae is dismissed. The main characteristics of the family Mydonomidae and Tylencholaimellidae are revised. Keys to the genera of Mydomonidae and Tylencholaimellidae are included.

A new species of the genus Eudorylaimus Andrássy, 1959 (Nematoda: (Dorylaimida: Qudsianematidae) associated with Picea crassifolia in China.

A new species, Eudorylaimus piceae n. sp., extracted from rhizosphere soil of Picea crassifolia from Inner Mongolia, China was identified. The new species is characterized by these combined characters: body length of 1.03-1.27 mm; lip region distinctly offset; odontostyle 20-22 µm and 1.1-1.4 times the lip region diameter in length; odontophore 1.1-1.2 times the odontostyle length; basal expansion of pharynx occupying 42%-50.5% of the total neck length; genital system didelphic-amphidelphic; vulva transverse; vagina extending inwards 32%-43%; V value averaging more than 60; pars refringens vaginae with two trapezoidal sclerotizations and pars distalis vaginae weakly sclerotized; prerectum 72-107 µm long, 2.3-3.3 times the anal body diameter, and rectum 1-1.6 times the anal body diameter in length; tail conoid and bent ventrally, c' value 1.5-1.8 and males unknown. Phylogenetic analyses based on sequences of 18S small subunit rDNA and the D2-D3 expansion region of 28S rDNA are presented.

[Stress analysis of the mandible by 3D FEA in normal human being under three loading conditions].

PURPOSE: The condition and character of stress distribution in the mandibular in normal human being during centric, protrusive, laterotrusive occlusion were analysed. METHODS: The three-dimensional finite element model of the mandibular was developed by helica CT scanning and CAD/CAM software, and three-dimensional finite element stress analysis was done by ANSYS software. RESULT: Three-dimensional finite element model of the mandibular was generated. Under these three occlusal conditions, the stress of various regions in the mandible were distributed unequally, and the stress feature was different;while the stress of corresponding region in bilateral mandibular was in symmetric distribution. The stress value of condyle neck, the posterior surface of coronoid process and mandibular angle were high. CONCLUSION: The material properties of mandible were closely correlated to the value of stress. Stress distribution were similar according to the three different loading patterns, but had different effects on TMJ joint. The concentrated areas of stress were in the condyle neck, the posterior surface of coronoid process and mandibular angle.