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A novel, enhanced photoelectrochemical aptasensing platform was developed through integrating the sensitization effect of CdTe@CdS core–shell quantum dots (QDs) coupled with exonuclease-I (Exo-I) assisted target recycling for significant signal amplification. Carcinoembryonic antigen (CEA) was selected as the target analyte to exhibit the analytical performance of this platform. Specifically, nitrogen-doped mesoporous TiO2 (mTiO2:N) was firstly synthesized through an evaporation-induced self-assembly (EISA) method. Then, an mTiO2:N/Au hybrid structure was prepared through depositing Au nanoparticles on the surface of the mTiO2:N film and this acted as the photoelectrochemical matrix to immobilize the complementary DNA (cDNA) of the CEA aptamer probe (pDNA). CdTe@CdS core–shell QDs as sensitization agents were covalently bound at the front-end of pDNA. After pDNA was hybridized with cDNA, the labels of the CdTe@CdS core–shell QDs were very close to the mTiO2:N/Au electrode surface, resulting in an evidently enhanced photocurrent intensity due to the generation of the sensitization effect. When the aptasensor was incubated with CEA and Exo-I simultaneously, CdTe@CdS QD labeled pDNA (denoted QD–pDNA) became specifically bound with CEA and meanwhile was separated from the electrode surface, leading to an obviously weakened sensitization effect and a decreased photocurrent intensity. Moreover, as Exo-I could digest the single strand form of pDNA, the previously bound CEA was released and continuously interacted with the rest of the pDNA on the electrode surface, causing further decreased photocurrent intensity. The well-designed photoelectrochemical aptasensor exhibited a low detection limit of 0.12 pg mL−1 and a wide linear range from 0.5 pg mL−1 to 10 ng mL−1 for CEA detection, and it also showed good selectivity, reproducibility and stability. The proposed signal amplification strategy provides a promising universal photoelectrochemical platform for sensitively detecting various biomolecules at low levels. [ABSTRACT FROM AUTHOR]

A novel multifunctional nanoplatform was designed based on the combination of silver nanoparticles (AgNPs) with nucleolin-targeted and doxorubicin (Dox)-loaded manganese dioxide (MnO2) nanosheets to induce enhanced cancer cell apoptosis. MnO2 nanosheets fabricated on the surface of AgNPs served as efficient fluorescence quenchers of Dox. After being internalized into cancer cells, the fluorescence of Dox could be turned on gradually by intracellular glutathione (GSH) which reduces MnO2 into Mn2+ to release Dox. The synergetic effects of AgNP-induced apoptosis and subsequent Dox delivery resulted in enhanced cancer cell apoptosis. Annexin V-FITC/PI double staining, mitochondrial membrane potential (MMP) detection and reactive oxygen species (ROS) detection demonstrated the specific enhanced apoptosis of cancer cells. In this way, the novel nanoprobes can be used as promising theranostic agents for specific cancer therapy. [ABSTRACT FROM AUTHOR]

Smart nanocarriers with switchable surfaces consisting of thermo-sensitive polymers and aptamers have been developed, through which the cellular uptake and photothermal therapy in five different cells could be spatial-temporally controlled on command, which is beneficial in maximizing therapy efficacy and minimizing side effects. [ABSTRACT FROM AUTHOR]

A novel luminescence probe based on mono-6-amino-β-cyclodextrin (NH2-β-CD) functionalised gold nanoclusters (β-CD-AuNC) was designed for dopamine (DA) detection. The NH2-β-CD molecules were conjugated onto the surface of 11-mercaptoundecanoic acid capped AuNCs (11-MUA-AuNC) via a carbodiimide coupling reaction. The integrity of the β-CD cavities was preserved on the surface of AuNCs and they retained their capability for molecular DA host–guest recognition. DA could be captured by the β-CD cavities to form an inclusion complex in which the oxidised DA could quench the fluorescence of the β-CD-AuNC probe by electron transfer. The probe could be used to quantify DA in the range of 5–1000 nM with a detection limit of 2 nM. This sensitivity was 1–2 orders of magnitude higher than that in previously reported methods. Interference by both ascorbic acid (AA) and uric acid (UA) was not observed. Therefore, the β-CD-AuNC probe could be directly used to determine the DA content in biological samples without further separation. This strategy was successfully applied to a DA assay in spiked human serum samples and it exhibited remarkable accuracy, sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

The expression of microRNAs (miRNAs) is related to some cancer diseases. Recently, miRNAs have emerged as new candidate diagnostic and prognostic biomarkers for detecting a wide variety of cancers. Due to low levels, short sequences and high sequence homology among family members, the quantitative miRNA analysis is still a challenge. A novel electrochemical biosensor with triple signal amplification for the ultrasensitive detection of miRNA was developed based on phosphatase, redox-cycling amplification, a bimetallic Pd–Pt supported graphene functionalized screen-printed gold electrode, and two stem-loop structured DNAs as target capturers. The proposed biosensor is highly sensitive due to the enhanced electrochemical signal of Pd–Pt supported graphene and sufficiently selective to discriminate the target miRNA from homologous miRNAs in the presence of loop-stem structure probes with T4 DNA ligase. Therefore, this strategy provided a new and ultrasensitive platform for amplified detection and subsequent analysis of miRNA in biomedical research and clinical diagnosis. [ABSTRACT FROM AUTHOR]

Cellulose was extracted from sugarcane bagasse by alkaline extraction with sodium hydroxide followed by delignification/bleaching using sodium chlorite/hexamethylenetetramine system. Factors affecting extraction process, including sodium hydroxide concentration, hexamethylenetetramine concentration and temperature were studied and optimum conditions for alkaline extraction were found to be boiling finely ground bagasse under reflux in 1 N sodium hydroxide solution and then carrying out the delignification/bleaching treatment at 95 °C using 5 g/l sodium chlorite together with 0.02 g/l hexamethylenetetramine. The extracted cellulose was used in the preparation of hydroxyethyl cellulose through reaction with ethylene oxide in alkaline medium. Factors affecting the hydroxyethylation reaction, like sodium hydroxide concentration during the alkali formation step, ethylene oxide concentration, reaction temperature and reaction duration were studied. Optimum conditions for hydroxyethylation reaction were using 20% NaOH solution and 200% ethylene oxide (based on weight of cellulose), carrying out the reaction at 100 °C for 60 min. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene) (PEDOT) nanowhiskers were fabricated in a [bmim][BF4] ionic liquid. The minimal size of the nanowhiskers is only 0.2 nm, and the size matches the thickness of a PEDOT single-molecular chain. They were successfully used as the electron transfer channels between the active center of hemoglobin (Hb) and an underlying electrode. The direct electron transfer process between Hb and the underlying electrode was realized without any electron mediator. Compared to that of a gold nanoparticle (AuNP)–Hb composite electrode, the catalytic current of a PEDOT nanowhiskers–AuNPs–Hb composite electrode for detecting H2O2 is increased 7 fold. A novel model of a H2O2 biosensor based on the PEDOT nanowhiskers–AuNPs–Hb composites was fabricated. The detection limit was estimated to be 0.6 μM at a signal/noise (S/N) ratio of 3, and the linear range of H2O2 concentration was from 1 μM to 1100 μM. Three constructed models of the biosensors showed a good stability, and all of them retained nearly 90% of their initial signals for 1 mM H2O2 when they were stored at 4 °C after 60 days. H2O2 concentration in contact lens nursing liquid was measured by the biosensor, and the results were in good agreement with the values provided by the supplier. It is shown that the PEDOT nanowhiskers can provide a new opportunity for the design of sensitive biosensors with long-term stability. [ABSTRACT FROM AUTHOR]

Strong natural bast fibers, especially flax fibers, can be used to replace glass fibers in reinforced composites. The properties of natural fibers depend largely on maturity, retting and processing. Two chemical treatments were applied to retted and semiretted flax fibers to create better fiber to resin bonding and to show the effect of retting degree and successive purification processes on the mechanical properties of natural composite materials. Retted and semiretted flax fibers have been scoured and bleached with the objective of removing surface impurities and developing finer structure. To investigate the effect of adhesion promoter on the mechanical properties of natural fiber composite, a composite sample was prepared from bleached retted flax pretreated with adhesion promoter Isostearoyltitanate (ISTT). After treatments the fibers got cleaner and the measurements showed that the fiber fineness as well as the surface free energy increased. The treatments were accompanied by decrease in the fiber tenacity but it has been found not to be reflected to the final mechanical properties of the composite. No improvement was remarked by using Isostearoyltitanate for surface modification. [ABSTRACT FROM AUTHOR]

Bifunctional starch composites were prepared by γ-induced grafting of acrylamide (Aam) and acrylic acid (AA) onto maize starch. The prepared composites were characterized by FTIR spectroscopy and scanning electron microscope (SEM). The feasibility of these composites to remove anionic dyes, direct blue 21 (D. Blue 21) and direct brown 2 (D. Brown 2) and a cationic dye, methylene blue (MB) were examined. Factors affecting adsorption of anionic and cationic dyes onto these starch composites were studied. These factors were radiation dose, agitation time, adsorbent and adsorbate concentrations. Prepared composites were effectively used in adsorption of D. Blue 2, D. Brown 2 and MB from aqueous solutions. The Adsorption data of both D. Blue 21 and D. Brown 2 complied with the Langmuir and Freundlich isotherms. [ABSTRACT FROM AUTHOR]

A new adsorbent was prepared from wood pulp (WP) after reaction with epichlorohydrin and dimethylamine in the presence of pyridine and N,N-dimethylformamide (DMF). The adsorption of Cr (VI) from aqueous solutions by the so-prepared wood pulp adsorbent (WP-A) was investigated. Various factors affecting adsorption, such as pH, adsorbent concentration (1–5 g/L), agitation time (5–60 min), and Cr (VI) concentration (50–700), were taken into consideration. The adsorption of Cr (VI) onto (WP-A) was found to be pH-dependent and maximum adsorption was obtained at pH 3. The adsorption data obeyed Langmuir and Freundlich adsorption isotherms. The Langmuir adsorption capacity (Q max ) was found to be 588.24 mg/g. Freundlich constants, K F and n, were found to be 55.03 and 2.835, respectively. [ABSTRACT FROM AUTHOR]

A novel electrochemical biosensing platform for nicotinamide adenine dinucleotide (NAD+)-dependent dehydrogenase catalysis was designed using the nitrogen-doped graphene (NG), which had properties similar to NADH dehydrogenase (CoI). NG mimicked flavin mononucleotide (FMN) in CoI and efficiently catalyzed NADH oxidation. NG also acted as an electron transport "bridge" from NADH to the electrode due to its excellent conductivity. In comparison with a bare gold electrode, an 800mV decrease in the overpotential for NADH oxidation and CoI-like behavior were observed at NG-modified electrode, which is the largest decrease in overpotential for NADH oxidation reported to date. The catalytic rate constant (k) for the CoI-like behavior of NG was estimated to be 2.3×105M−1s−1, which is much higher than that of other previously reported FMN analogs. The Michaelis-Menten constant (Km) of NG was 26μM, which is comparable to the Km of CoI (10μM). Electrodes modified with NG and NG/gold nanoparticals/formate dehydrogenase (NG/AuNPs/FDH) showed excellent analytical performance for the detection of NADH and formate. This electrode fabrication strategy could be used to create a universal biosensing platform for developing NAD+-dependent dehydrogenase biosensors and biofuel cells. [ABSTRACT FROM AUTHOR]