Procedia Technology最新文献

The current trend towards flexible and light-weight portable electronic devices has raised the profile of the emerging field of printed electronics. Printable organic electronic devices provide a high-throughput and cost-effective approach for the fabrication of distributed healthcare devices, which will meet new market needs. Here, we present an innovative modular approach for the design and fabrication of printable biosensors. A “LEGO” style approach comprising various colloidal building blocks, such as conducting polymer-based microparticles and biopolymer-based microparticles (e.g. enzymes and antibodies) with well-defined and tunable nano-scale morphology, electrochemical behaviours and catalytic functions, were fabricated for the development of printable biosensors. Assembly of the printable biosensors can be performed simply by mixing various microparticles delivering the desired conductivity, capacitance, catalytic and affinity functions, followed by solvent-free printing of the microparticle mixture onto a substrate. The conductivity, capacitance and signal response of the printable biosensors were characterised. This modular approach allows high flexibility for the design for biosensors, as well as better integration between conducting polymers and biomolecules for the development of biosensors. As a proof-of-concept, a mediated glucose biosensor based on printable microparticles was developed and showed a high sensitivity of 2 mA (M cm²)^-1.

The miniaturization of processes in Analytical Chemistry is a basic trend that has become quite relevant during the last years as well as low-cost methodologies. They offer advantageous characteristics for both, developed and developing countries, with special application to remote sensing, where untrained personnel and power facilities are scarce. Paper-devices have demonstrated their potentiality for this aim with disposable and inexpensive platforms. However, selectivity and sensitivity have to be ensured. In this context, a separation technique (electrophoresis) and a sensitive principle of detection (electrochemistry) are combined. Here we develop a folded paper-based device with integrated electrophoretic separation and electrochemical detection. The platform has different layers with hydrophobic wax barriers that delimit channels for performing both functions. Detection and separation has been demonstrated with epinephrine and hydroquinone analytes.

In this communication we report the synthesis, characterization and applications of TeNTs decorated with PtNPs readily prepared by two simple steps to make a GC modified electrode suitable to be used as anode/cathode in fuel cells. In the 1^th step the large scale of Te nanotubes synthesis was obtained via a vapor deposition method; then in the 2^nd step TeNTs dispersed in methanol react with PtCl₂ to make TeNTs/PtNPs. Modified electrodes TeNTs/PtNPs/GC were then made by casting 20 μL of TeNTs/PtNPs/ethanol suspension onto GC surface and left to evaporate at room temperature. The as synthesized hybrid nanostructures, fully characterized by XRD, TEM and XPS analysis, were composed of Te nanotubes decorated with Pt nanoparticles. The electrochemical characterization of TeNTs/PtNPs composite material, performed by cyclic voltammetry (CV), showed exceptional electrocatalytic activity towards methanol oxidations and oxygen reduction.

In this study, a new biosensor was developed based on a bacterial laccase immobilizing on Escherichia coli surface and direct glassy-carbon electrode adsorption of live cells. Expression and surface localization of laccases in target cells were confirmed by assays of Western blot, immunofluorescence microscopy and flow cytometry. The engineered cells served as a highly active whole cell laccase-catalytic system with an enzyme activity of 32.7 U/mL cells. Under optimized pH condition, electrochemical response of the biosensor was linear within concentration ranges of 5.0 μM to 500.0 μM for several phenolics (catechol, caffeic acid, dopamine, gallic acid, and 2-amino phenol) with a detection limit of 1.0 μM to 5.0 μM, which was comparable to those based on chemically-modified purified laccases. The system exhibited good stability and reproducibility. It also offered considerable level of accuracy for determination of the phenolic compound contents of wed wine, pharmaceutical and wastewater samples.

We demonstrate synthesis of Multiwalled carbon nanotubes (MWCNTs) embedded highly oriented Zinc Oxide (ZnO) nanowires targeted towards development of ultrasensitive electrochemical nanobiosensors using electrospinning method. The synthesized composite nanowires combines advantages of ZnO such as biocompatibility, electrostatic affinity towards biomolecules with the excellent conductivity and surface functionalization capabilities of MWCNTs. Calcination temperature is optimized so as to ensure MWCNTs are present in their original form and at the same time highly crystalline ZnO is obtained. The key advantage of this process is that there is no separate functionalization process is required to create functional groups on MWCNTs. Furthermore, the electrochemical activity of MWCNTs embedded ZnO nanowires is much higher as compared to pure ZnO nanowires. We have demonstrated the performance of electrochemical nanobiosensor using Biotin-streptavidin interaction as model system. The sensor exhibits excellent sensitivity in the range 10 μgmL^-1 - 0.5 fgmL^-1 of streptavidin with 0.5fgmL^-1 limit of detection.

In this study, a shear horizontal surface acoustic wave (SHSAW) was used for Escherichia coli (E. coli) detection. E. coli O157:H7 serotype, a dangerous strain among 225 E. coli unique serotypes was chosen as test sample. A few cells of this bacterium are able to cause young children to be most vulnerable to serious complications. Presence of higher than 1 cfu E. coli O157:H7 in 25 g of food has been considered as a dangerous level. The SHSAW biosensor was fabricated on 64⁰ YX LiNbO₃ substrate. Five different interdigital transducers (IDT) parameters (Fig. 1(a)-1(e)) SHSAW were fabricated to compare the mass loading sensitivity before advancing to the bio sensing application: four of them were 32 μm pitch size (with the average of synchronous frequency, f₀ = 144.303 MHz) and one was 12 μm pitch size (with f₀ = 384.948 MHz). All of the four 32 μm pitch sizes were with different combination of delay line length (3.904 mm and 7.296 mm) and aperture size (1.376 mm and 2.464 mm). As for the 12 μm pitch size device, it was with 2.1 mm delay line length and 0.72 mm aperture size. Eventually, 12 μm pitch size device was selected for oligonucleotides detection and its mass loading sensitivity was 1558.04 MHz/ (mg/mm²), 4.8-fold higher than the most sensitivity one in 32 μm pitch size).

Its sensitivity was enhanced by depositing 130 nm thin layer of SiO2 nanostructures with particle size less than 70 nm (Fig. 1(f)-1(g)). The nanostructures act both as a waveguide as well as the surface physical modification of the sensor prior to biomolecule immobilization. For this work, a specific DNA sequence from E. coli O157:H7 having 22 mers as an amine-terminated probe ssDNA was immobilized on the thin film sensing area through chemical functionalization [(CHO-(CH2)3-CHO) and (APTES; NH2-(CH2)3-Si(OC2H5)3]. The high-performance of sensor was shown with the oligonucleotide target and attained the sensitivity of 0.6439 nM/ 0.1 kHz and detection limit was down to 1.8 femtomolar (1.8 x 10^-15 M). Further evidence was provided by specificity analysis using single mismatched and complementary oligonucleotide sequences.

Bioluminescence of isolated enzymes is a perspective phenomenon for biosensors development due to simplicity of registration of a physiological parameter - light intensity. Enzyme-based bioluminescent assay is widely used to evaluate a decrease in biochemical toxicities. Also the enzyme-based assay is used for the direct biochemical monitoring of oxidative toxicity. This work considers antioxidant properties of fullerenols, water-soluble polyhydroxylated derivatives of fullerenes and perspective pharmaceutical agents, in solutions of model inorganic and organic toxicants of oxidative type – K₃[Fe(CN)₆] and 1,4-benzoquinone. Two fullerenol preparations were used: C₆₀O_2-4(OH)_20-24 and mixture of two types of fullerenols C₆₀O_2-4(OH)_20-24+C₇₀O_2-4(OH)_20-24. The enzyme-based assays showed the peculiarities of the detoxification processes: ultralow concentrations of fullerenols were active (ca 10^-17-10^-5g/L); no monotonic dependence of detoxification efficiency on fullerenol concentrations was observed, and detoxification of organic oxidizer solutions was more effective than that of the inorganic oxidizer. The antioxidant effects of highly diluted fullerenol solutions were attributed to hormesis phenomenon; the detoxification was concerned with stimulation of adaptive cellular response under low-dose exposures.

We have developed a lithographically patterned flexible paper-based microfluidic device using photo polydimethylsiloxane (PDMS). Normal PDMS is converted into photosensitive PDMS with the desired photoinitiator. Further paper is lithographically patterned by photo PDMS to form hydrophobic region, where the flow of aqueous solution are restricted and a hydrophilic region, where fluids can flow by capillary action without any need of an external pump. The fabricated device can attain three-dimensional structured network flow on a single paper by repeated crease, without stacking multiple layers of individual paper.