Procedia Technology最新文献

An electrochemical immunosensor for the simultaneous determination of ghrelin (GHRL) and peptide YY (PYY) using dual screen-printed carbon electrodes modified with reduced graphene oxide (rGO) is presented. Diazonium salt of 4-aminobenzoic acid (4-ABA) was electrochemically grafted on the modified electrodes allowing covalent immobilization of antibodies. After competitive immunoassays using alkaline phosphatase labelled antigens, the affinity reactions were monitored by DPV upon addition of 1-naphthyl phosphate. Calibration plots showed linear current vs. log [hormone] ranges from 10^-3 to 100 ng/mL GHRL, and 10^-4 to10 ng/mL PYY. The usefulness of dual immunosensor was demonstrated by analysis of spiked human serum and saliva.

Stilbenes have not been widely regarded as fluorophore labels due to their difficulty in conjugation. Quenched fluorescence of maleimide functionalized stilbene is found to be restored after thiol binding, enabling separation-free fluorophore labelling.

Herein, we report a scalable synthesis of multifunctional conducting polyacrylic acid (PAA) hydrogel (MFH) integrated with reduced grapheme oxide (rGO), vinyl substituted polyaniline (VS-PANI) and lutetium phthalocyanine (LuPc₂) as three dimensional robust matrix for glucose oxidase (GOx) immobilization (PAA-rGO/VS-PANI/LuPc₂/GOx-MFH). We have integrated the multicomponents such as PAA with rGO, VS-PANI through free radical polymerization using methylene bis-acrylamide, ammonium persulphate as the cross linker and initiator. The LuPc₂ was then doped to form multifunctional hydrogel (PAA-rGO/VS-PANI/LuPc₂-MFH). Finally, biosensor was fabricated by immobilizing GOx into PAA-rGO/VS-PANI/LuPc₂-MFH and subsequently used for electrochemical detection of glucose.

A hybrid graphene-polypyrrole (PPy) composite-based platform was elaborated by using nanosphere lithography structuration. This platform was further used for the antibody anti-acetaminophen immobilization in order to obtain an immunosensor for selective detection of paracetamol (acetaminophen) by using electrochemical methods. After patterning of the composite layer, the five-fold improvement of electrochemical signal was observed, suggesting that a higher amount of antibody was immobilized. This strategy permitted the ease and controlled immobilization of bioreceptors on the composite graphene-PPy platform and enhanced the sensitivity for paracetamol detection.

Two different graphene/β-cyclodextrin (CD)-based biosensors were elaborated for dopamine (DA) determination starting from glassy carbon electrode (GCE). First one was obtained by modifying GCE with reduced graphene oxide (RGO), CD and tyrosinase (Tyr) immobilized with a polyethylenimine film. The second biosensor was obtained after the incorporation of RGO functionalized with a new synthesized pyrrole-β-CD derivative and Tyr in an electropolimerized poly-amphiphilic pyrrole film. These two new approaches have resulted in selective and sensitive determination of DA in pharmaceuticals and real human samples.

We theoretically study a three-layer continuum model of a surface acoustic wave sensor where the two overlayers are allowed to be viscoelastic. This case is particularly important in biosensing, where soft materials submerged in fluids are commonplace. From the general dispersion equation, we calculate the phase velocity shift and the wave attenuation. We show that there is a viscoelastic coupling between the overlayers which results in unintuitive behavior, e.g., the addition of viscous loading to a soft-film sensor can reduce the attenuation.

The conventional microfluidic electrophoresis chip must be applied higher voltage, which limited the microminiaturization and integration. According to the principle of electrophoresis chip, a helix channel electrophoresis chip drove by low voltage was proposed. Some key techniques were researched, which include the bubble issue, optimization of the chip structure, low cost hydrophilic surface modification for the chip, design of miniaturized control and detection system. Test results shown the helix channel chip has better separation than the cross channel chip, and the sample can be successfully separated below 100 V voltage.

The objective of the present invention is to develop an ultrasensitive technique for the electro analysis of rape drug. A paper chip (EμPADs) was developed using nanocrystals (Nanocrys) of graphene-oxide and zeolites (Zeo-GO). Nanocrys modified EμPAD showed wide linear range 0.001 - 5 nM/ml and low detection limit of 0.00002 nM/ml. The developed sensor was tested in real time samples like alcoholic and non-alcoholic drinks and found good correlation (99%). Extensive development can be made for industrial translation of this fabricated device.

Commonly immunoassay using magnetic nanoparticles (MNP) are performed under the control of permanent magnet close to the micro-tube of reaction¹. Using a magnet gives a powerful method for driving MNP but remains unreliable or insufficient, for a fully integrated immunoassay on lab-on-chip. The aim of this study is to develop a novel lab-on-chip (Figure 1.B) for high efficient immunoassays to detect pathogenic bacteria with microcoils employed for trapping MNP during the biofunctionalization steps. Studies on bacteria are mainly based on E. Coly^2,3 which is a non-pathogenic bacteria and can be find everywhere. In our case we use ovalbumin which is defined as a biodefense model protein. The objectives are essentially to optimize their efficiency for biological recognition, by assuring a better bioactivity (antibodies-ovalbumin), and detect small concentrations of the targeted protein (∼10 pg/mL).

The fluidic microsystem is made of PDMS, which is micro-molded in SU8, it had channels with 50 μm height and 500 μm width. Microfluidic conditions permit a faster biofonctionnalisation step than in test tube and allow capture and detection of biological elements integrated in lab-on-chip.

Microcoils are electrodeposited on silicon using cupper. They are microfabricated with cupper wire of 10 μm height, 10 μm width, 10 μm space between wire and 45 spires. Microcoils are encapsulated in microfluidic chip by covering them with a spin-coated thin layers of PDMS. Microcoils give a local and efficient trapping of MNP and a fully integrated device.

Biological activity is studied respecting ELISA protocol with ovalbumin as protein of interest. To graft the primary antibody and protect the free area of MNP we used carboxylic as terminal group for grafting antibodies and BSA (Bovine Serum Albumin) for passivation (Figure 1.A). We characterize this method by measuring the intensity of the antibody of detection using FITC (Fluorescein isothiocynathe). Intensity is detected by fluorescent microscope connected to the microfluidic plateform and images are processed using a home-made script.

First we studied the response of immunoassays complex function of MNP size (200 nm, 300 nm and 500 nm), we confirmed that with a lower diameter we increase the intensity detected, following specific surface formula (1), (2), (3).

Regarding the magnetic force needed (depending of several parameters including magnetic field and parameters of the particle) and the intensity detected we selected 300 nm size of NPM.

We studied the response of immunoassays complex function of ovalbumin concentration. We realized different immunoassays by controlling MNP (Figure 1.C&D) in test tube and in microfluidic device using a magnet. The comparison between these two experiments allow us to show an improved limit of detection (L.O.D. = I₀ – 3 × σ_D