Applications of Nanomaterials in Electrogenerated Chemiluminescence Biosensors

Electrogenerated chemiluminescence (also called electrochemiluminescence and abbreviated ECL) involves the generation of species at electrode surfaces that then undergo electron-transfer reactions to form excited states that emit light. ECL biosensor, combining advantages offered by the selectivity of the biological recognition elements and the sensitivity of ECL technique, is a powerful device for ultrasensitive biomolecule detection and quantification. Nanomaterials are of considerable interest in the biosensor field owing to their unique physical and chemical properties, which have led to novel biosensors that have exhibited high sensitivity and stability. Nanomaterials including nanoparticles and nanotubes, prepared from metals, semiconductor, carbon or polymeric species, have been widely investigated for their ability to enhance the efficiencies of ECL biosensors, such as taking as modification electrode materials, or as carrier of ECL labels and ECL-emitting species. Particularly useful application of nanomaterials in ECL biosensors with emphasis on the years 2004-2008 is reviewed. Remarks on application of nanomaterials in ECL biosensors are also surveyed

Editorial: Nanotechnological Advances in Biosensors

A biosensor is a physicochemical or hybrid physical-chemical-biological device that detects a biological molecule, organism, or process. Because of the nature of their targets, biosensors need to be faster, smaller, more sensitive, and more specific than nearly all of their physicochemical counterparts or the traditional methods that they are designed to replace. Speed is of the essence in medical diagnosis as it permits for rapid, accurate treatment and does not allow patients to be lost to follow-up. Small size and greater sensitivity mean less-invasive sampling and detection of molecules such as neurotransmitters or hormones at biologically-relevant levels. Greater specificity allows assays to be performed in complex fluids such as blood or urine without false negative or false positive results. [...

Applications of Nanomaterials in Electrochemical Enzyme Biosensors

A biosensor is defined as a kind of analytical device incorporating a biological material, a biologically derived material or a biomimic intimately associated with or integrated within a physicochemical transducer or transducing microsystem. Electrochemical biosensors incorporating enzymes with nanomaterials, which combine the recognition and catalytic properties of enzymes with the electronic properties of various nanomaterials, are new materials with synergistic properties originating from the components of the hybrid composites. Therefore, these systems have excellent prospects for interfacing biological recognition events through electronic signal transduction so as to design a new generation of bioelectronic devices with high sensitivity and stability. In this review, we describe approaches that involve nanomaterials in direct electrochemistry of redox proteins, especially our work on biosensor design immobilizing glucose oxidase (GOD), horseradish peroxidase (HRP), cytochrome P450 (CYP2B6), hemoglobin (Hb), glutamate dehydrogenase (GDH) and lactate dehydrogenase (LDH). The topics of the present review are the different functions of nanomaterials based on modification of electrode materials, as well as applications of electrochemical enzyme biosensors

Towards Multiplexed Electrogenerated Chemiluminescent Detection

The main objective of this dissertation is to understand and study the principle of electrogenerated chemiluminescence (ECL) and its applications to detect biomolecules simultaneously. Four aspects of ECL were studied. In order to carry out multiplexed ECL detection, both classical and several novel ECL systems have been investigated. In the first aspect, significant effect of chloride ions on the ECL behavior of the tris(2,2′-bipyridyl) ruthenium(II) (Ru(bpy)3 2+)/tri-n-propylamine (TPrA) system at Au electrode was investigated. At low concentrations (e.g., [Cl-] \u3c 5 mM), the ECL was enhanced; at relatively high concentrations, however, the ECL intensity decreased with the increase of the [Cl-]. At [Cl-] = 90 mM, ~ 50% and 100% ECL inhibition was observed for the first and the second ECL wave, respectively. The electrogenerated chloroaurate anions (AuCl2 - and AuCl4 -) which were verified using an electrochemical quartz-crystal microbalance (EQCM) method were found to be responsible for the ECL inhibition. This study suggests that care must be taken when Au working electrode is used for ECL studies in chloride-containing buffer solutions (widely used in DNA probes) and/or with the commonly used chloride-containing reference electrodes since in these cases the ECL behavior may significantly disagree with that obtained using other electrodes and reaction media. In the second aspect, the electrochemical behavior of a trinuclear ruthenium(II)- containing complex, [((phen)2Ru(dpp))2RhCl2]5+ (where phen = 1,10-phenanthroline, dpp = 2,3-bis-2-pyridylpyrazine), was studied in acetonitrile (MeCN) and aqueous solutions. In MeCN containing 0.10 M tetra-n-butylammonium perchlorate (TBAP), the complex displayed a reversible, overlapping RuII/III redox process with E1/2 = +1.21 V vs Ag/Ag+ (10 mM), an irreversible reduction of RhIII/I at -0.73 V vs Ag/Ag+, and two quasireversible dpp/dpp- couples with E1/2 = -1.11 V and -1.36 V vs Ag/Ag+ at a Pt electrode with a scan rate of 50 mV s-1. In 0.20 M Tris buffer solution (pH 7.4), an irreversible, overlapping RuII/III oxidation at +1.48 V vs Ag/AgCl (3 M KCl), and an irreversible reduction of RhIII/II at -0.78 V vs Ag/AgCl were observed at a glassy carbon electrode with a scan rate of 50 mV/s. Investigations on the ECL of the complex revealed that 2-(dibutylamino) ethanol (DBAE) was superior to TPrA as an ECL coreactant within their entire concentration range of 10-100 mM in MeCN, and in aqueous media, as low as 1.0 nM of the complex could be detected using TPrA coreactant ECL. A maximum ECL emission of 640 nm, which is about 55 nm blue-shifted with respect to its fluorescence peak, was observed in MeCN with DBAE as a coreactant. Interactions of the complex with calf thymus DNA (ctDNA) were conducted with a flow-cell based QCM, and a binding constant of 2.5×105 M-1 was calculated on the basis of the Langmuir isotherm equation. In the third aspect, ECL behavior of core/shell semiconductor CdSe/ZnS nanocrystals coated with a carboxyl polymer layer (quantum dot, Qdot, or QDs) was studied in aqueous solutions using TPrA and DBAE as ECL coreactant. Upon the anodic potential scanning, strong ECL emissions were observed at glassy carbon (GC) electrode within the potential range of ~0.75 to 1.5 V vs Ag/AgCl (3.0 M KCl) when DBAE was used as the coreactant. The ECL behavior of the Qdot was found to be strongly dependent on the types and concentrations of ECL coreactants as well as the nature of the working electrode. The ECL emission measured with the Qdot/DBAE/GC electrode system has a peak value of ~625 nm, which matched well with its fluorescence. The Qdot as a label for ECL-based C-reactive protein (CRP) immunoassays was realized by covalent binding of avidin on its surface, which allowed biotinalyted antibodies to be attached and interacted with antigens and the antibodies linked to micro-sized magnetic beads. The newly formed sandwich type aggregates were separated magnetically from the solution matrix, followed by the ECL generation in the presence of the coreactant DBAE. ECL experiments were carried out with a potential scan from 0 to 1.5 V vs Ag/AgCl at partially transparent Au/CD electrodes, and the integrated ECL intensity was found to be linearly proportional to the CRP concentration over the range of 1.0-10.0 μg/mL. In the fourth aspect, the ECL behavior of Ru(bpy)3 2+, 9,10-diphenylanthracene DPA), and rubrene (RUB) with DBAE or TPrA as the coreactant was studied in acetonitrile solution. The ECL emission spectra of the mixed solution including the above three ECL labels were investigated. The ECL maximum emissions at ~440 nm for DPA, ~560 nm for RUB, and ~630 nm for Ru(bpy)3 2+ were linearly proportional to the concentration of each individual ECL labels in mixed solutions, suggesting that multiplexing detection and quantification of biomolecules with ECL technology is feasible

Recent advancement in sensitive detection of carcinoembryonic antigen using nanomaterials based immunosensors

Carcinoembryonic antigen (CEA) is a prominent cancer biomarker that allows for early diagnosis of various cancers. Present immunoassays techniques help quantify such target molecules in test samples via anti-antibody reaction. Despite their rapid usage, conventional immunoassay techniques demonstrate several limitations that can be easily overcome by employing nanomaterials in sensing assays. Thus, nanomaterial-based immunosensors have gained steady attention from the scientific community owing to their high specificity and low detection limit. Various nanomaterials like platinum, gold, silver and carbon exhibit exceptional properties have allowed promising results in the detection and diagnostics of CEA. Thus, the present review aims to explore the significance and the recent developments of nanomaterial-based biosensors for detecting CEA biomarkers with high sensitivity, selectivity, and specificity. After a brief introduction, we discussed the fundamentals of immunosensors immobilization strategies and common nanomaterials. In the next section, we highlighted the recent advances in the common immunosensors detection approaches for CEA alone and simultaneous detection of CEA with other biomarkers detection. Finally, we concluded the review by discussing the future perspectives of this promising field of biomarkers detection

Three dimensional atom probe tomography of nanoscale thin films, interfaces and particles

This dissertation demonstrates our research effort dedicating to extend the application of 3DAPT technique to various new materials including nanoscale monolayers, thin films, interfaces and particles for the first time. Novel sample designs and preparation methods are developed in order to broaden the application of the technique into fundamentally new areas such as monolayers, organic/biomaterials, polymers and nanoparticles analysis. Samples including surface oxide layers, ionic monolayers, alkanethiol monolayers, electrodeposited polymers, nanoparticles and metal-metal interfaces were successfully analyzed for the first time. A new sample configuration is proposed as using electrodeposited polymers to encapsulate nanoscale analytes and to coat conventional atom probe tips. This design enables the technique to image varieties of new materials which can not be analyzed before. Using this approach gold nanoparticles about 1.4 ~ 2 nm were observed in the three dimensional reconstruction images. The results demonstrate the ability of modern APT technique in the new areas and inspire the future discoveries

Surface-stress-based microcantilever aptasensor

This thesis presents the design, modelling, fabrication, and biological evaluation of a microcantilever-based aptasensor. It is the first reported work on aptasensors with aptamer immobilized on a bare SU-8 surface. Aptasensor surface funtionalisation was achieved using gas plasma treatment. Label-free detection of thrombin molecules using the aptasensor was successfully demonstrated