Potential Applications In Bioanalysis Research Articles

Determination of Glucose on Free Enzyme-based Poly(dimethylsiloxane) Microchip

Abstract Microfluidic enzyme-based reactor could be used to detect biomolecules with high sensitivity and selectivity. Based on the electrophoretic-mediated microanalysis (EMMA) method, a novel free enzyme-based microchip was developed to detect glucose. Online catalysis reaction of glucose by glucose oxidase was carried out on the chip. The product H 2 O 2 was detected using amperometric method. The working electrode, single carbon fibre cylindrical electrode, was held at a constant potential of +1.4 V versus Ag/AgCl electrode. The results indicated that the peak current had a good linear relationship with glucose concentration in the range of 0.1–20 mM ( R = 0.997) with good reproducibility (RSD = 2.02%, n = 10). The detection limit of glucose was 19.8 μM ( S/N = 3). This free enzyme-based reactor was easy to fabricate and operate, which showed great potential application in bioanalysis.

Controlled Radical Synthesis of Fluorene-Based Blue-Light-Emitting Copolymer Nanospheres with Core−Shell Structure via Self-Assembly

We prepared a series of well-defined polyfluorene-based copolymers by using polyfluorene (PF) macroinitiators to initiate atom transfer radical polymerization (ATRP) of γ-methacryloxypropyltrimethoxysilane (MPS). The chemical structures of hydroxy-functionalized PF (PFOH), PF macroinitiators (PFBr), and polyfluorene-b-poly(γ-methacryloxypropyltrimethoxysilane) (PF-b-PMPS) block copolymers were confirmed by 1H NMR. In THF/aqueous solution, amphiphilic PF-b-PMPS block copolymers can self-assemble into core−shell micelles with PMPS as the core and PF as the shell. Base-catalyzed sol−gel process inside the PMPS core results in PF-encapsulated silica core−shell nanospheres. Transmission electron microscopy (TEM) studies reveal the dense grafting of PF on the surface of silica core. The effect of PF-b-PMPS core−shell structures on the optical and electrochemical properties was also investigated. This novel kind of luminescent nanosphere has potential applications in bioanalysis, biomedical, and light-emitting devices.

Selective immobilization of tris(2,2′-bipyridyl)ruthenium (II) onto array electrode for solid-state electrochemiluminescene sensor fabrication

An effective method for selective immobilization of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)32+) onto one target electrode surface based on the electrodeposition of RuDS NPs (Ru(bpy)32+ doped silica nanoparticles)/chitosan composite film is presented in this paper. Ru(bpy)32+ was selectively deposited onto four individual electrodes in an Au electrode array. The results demonstrate the possibility of selective immobilization of Ru(bpy)32+ onto array electrodes and selective immobilization of different ECL composite. Therefore have potential applications in bioanalysis, capillary electrophoresis and drug screening.RuDS NPs and the resulting composite film were characterized by UV–vis spectroscopy, transmission electron microscopy (TEM) and Field emission-scanning electron microscope (FE-SEM). The electrochemiluminescence (ECL) sensor based on the composite film modified electrode exhibited excellent reproducibility, stability and sensitivity for the detection of tri-n-propylamine (TPA). The linear range was from 1×10−10 to 1×10−6M (R2=0.9954) with the detection limit of 5×10−11M.

Interactions between protein and porphyrin-containing cyclodextrin supramolecular system: a fluorescent sensing approach for albumin

The interactions of meso-tetraphenylporphyrin (TPP), meso-tetraphenylporphyrin cobalt(ii) (CoTPP) and protein in the presence of a cyclodextrin derivative, heptakis(2,6-di-O-n-octyl)-beta-cyclodextrin (Oc-beta-CD), have been investigated. In the presence of Oc-beta-CD, significant increase of TPP fluorescence was realized, but the increased fluorescence was quenched by CoTPP. To further investigate the fluorescence-quenched system and explore its potential application in bioanalysis, a strategy has been devised to restore the quenching fluorescence of TPP upon interacting with protein. The restoration of TPP fluorescence in the present system is fast and accomplished upon interaction with bovine serum albumin (BSA) or human serum albumin (HSA). On the basis of the spectroscopic measurement and excited state fluorescence lifetime, the mechanism of TPP fluorescence quenching is attributed to formation of a ground-state complex of TPP and CoTPP, and the fluorescence restoration is attributed to the binding of CoTPP with the protein molecule which destroys the aggregate, releasing the free base porphyrin. With optimized conditions, the calibration equations are linear from 0.80 to 75.4 microg mL(-1) BSA and from 3.20 to 93.2 microg mL(-1) HSA. The corresponding detection limits are 0.32 microg mL(-1) for BSA and 1.06 microg mL(-1) for HSA, respectively. The method was used for the direct assay of HSA content in human serum. The result is comparable to that obtained by another method. The recovery from BSA in synthetic sample is also satisfactory.

Development of an electrochemical assay for 2,6-dinitrotoluene, based on a screen-printed carbon electrode, and its potential application in bioanalysis, occupational and public health

Screen-printed carbon electrodes (SPCEs) have been successfully exploited as disposable sensors for the measurement of 2,6-dinitrotoluene (2,6-DNT) using a stripping voltammetric method. Initial investigations were undertaken using cyclic voltammetry (CV) to characterise the redox behaviour at the SPCEs. Further studies were then performed to deduce the optimum applied potential and accumulation time for the stripping voltammetric procedure. In addition, a study was carried out to ascertain whether small volumes of samples could be reliably used for analysis. From these studies it was shown that a 100 μl aliquot of sample could be analysed and the calibration plot was linear from 161 ng ml −1 to 137 μg ml −1 (R 2=0.9991), the former concentration being the detection limit. The effects of the major components of human saliva at concentrations normally present were investigated. Of the individual components tested, only Cl − and albumen were found to interfere. The presence of the latter could be easily overcome by the addition of (NH 4) 2SO 4. An interference study was also carried out on some inorganic and organic species that may be present in water samples. The sensors were evaluated by carrying out 2,6-DNT determinations on spiked and unspiked human saliva, dust wipe and potable water samples. Mean recoveries of 47.5, 73.4 and 102.4% were obtained; coefficients of variation of 7.88, 6.63 and 6.42% were calculated for a concentration of 9.1 μg ml −1 in water, 10.6 μg ml −1 saliva samples, and 141.1 ng cm −2 for dust wipe samples, respectively. The performance characteristics show that the method holds promise and reliable data may be obtained for 2,6-DNT in bioanalysis and public health.

Novel Interaction between Glutamate and the Cu2+/DMABN/β-CD Complex

A new fluorescence-quenched ternary complex, Cu2+/DMABN/β-CD, has been synthesized using β-cyclodextrin (β-CD), copper ions (Cu2+), and 4-(dimethylamino) benzonitrile (DMABN). The significant quenching of DMABN fluorescence is realized through a photoinduced electron-transfer process between DMABN and Cu2+. On the basis of the photochemical properties of the ternary complex, we have proposed a Cu2+/DMABN/β-CD complex structure with a 2:2:2 molar ratio. To further investigate the ternary complex and explore its potential applications in bioanalysis, we have adopted a novel strategy to restore the quenched fluorescence of DMABN when the complex interacts with an important neurotransmitter, glutamate. The restoration of DMABN fluorescence in the ternary complex is complete and fast upon glutamate interaction. The new complex synthesis and the restoration of the quenched fluorescence processes enable a better understanding of cyclodextrin-based chemistry and also the exploration of novel bioanalysis techniques for neurotransmitters and amino acids. GABA and NMDA have also been used to interact with the ternary complex to restore its fluorescence. Different binding capabilities with the complex show that there are significant differences in binding affinity with different ligand molecules. The new complex and the restoration process will be further explored for bioassays for amino acids and neurotransmitters.