A biosensor device is defined by its biological, or bioinspired receptor unit with unique specificities towards corresponding analytes. These analytes are often of biological origin like DNAs or proteins from the immune system (antibodies, antigens) of diseases or infections. Such analytes can also be simple molecules like glucose or pollutants when a biological receptor unit with particular specificity is available. One of many other challenges in biosensor development is the efficient signal capture of the biological recognition event (transduction). Such transducers translate the interaction of the analyte with the biological element into electrochemical, electrochemiluminescent, magnetic, gravimetric, or optical signals. In order to increase sensitivities and to lower detection limits down to even individual molecules, nanomaterials are promising candidates due to the possibility to immobilize an enhanced quantity of bioreceptor units at reduced volumes and even to act itself as transduction element. Among such nanomaterials, gold nanoparticles, semi-conductor quantum dots, polymer nanoparticles, carbon nanotubes, nanodiamonds, and graphene are intensively studied. Due to the vast evolution of this research field, this review summarizes in a non-exhaustive way the advantages of nanomaterials by focusing on nano-objects which provide further beneficial properties than “just” an enhanced surface area.

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Nanomaterials for biosensing applications: a review

Immunosensors--principles and applications to clinical chemistry.

Bioanalytical methods have experienced unprecedented growth in recent years, driven in large part by the need for faster, more sensitive, more portable (“point of care”) systems to detect protein biomarkers for clinical diagnosis. Electrochemical detection strategies, used in conjunction with immunosensors, offer advantages because they are fast, simple, and low cost. Recent developments in electrochemical immunosensors have significantly improved the sensitivity needed to detect low concentrations of biomarkers present in early stages of cancer. Moreover, the coupling of electrochemical devices with nanomaterials, such as gold nanoparticles, carbon nanotubes, magnetic particles, and quantum dots, offers multiplexing capability for simultaneous measurements of multiple cancer biomarkers. This review will discuss recent advances in the development of electrochemical immunosensors for the next generation of cancer diagnostics, with an emphasis on opportunities for further improvement in cancer diagnostics a...

Electrochemical Immunosensors for Detection of Cancer Protein Biomarkers

Interest in the development of surface plasmon resonance (SPR) based immunosensors for detection and monitoring of low-molecular-weight analytes of biomedical, food and environmental fields has been rapidly increasing over the last 10 years. By combining the advantages of the specific antigen–antibody immunoreaction and the high sensitivity and reliability of SPR signal transduction, SPR immunoassays offer exceptional performance capabilities with respect to sensitivity, specificity, speed and multianalyte detection in complex analytical matrices. Advancements in the technology of antibody production and the signal transduction provide a promising scope for SPR immunosensors to lead in the next generation biosensors. This review highlights the current state-of-the-art in SPR immunosensors and outlines briefly the important issues with regard to the development of SPR immmunosensors, such as preparation of the biomolecules, sensor fabrication, non-specific adsorption, surface regeneration and detection principles. Particular emphasis is given to the indirect competitive immunoassay principle which is compatible and highly promising for detection of small analytes with enhanced sensitivity. In addition, recent advancements and trends in the application of SPR immunosensors in biomedical, environmental and food-related analyses are discussed.

Recent advancements in surface plasmon resonance immunosensors for detection of small molecules of biomedical, food and environmental interest

The invention is directed to devices that allow for simultaneous multiple biochip analysis. In particular, the devices are configured to hold multiple cartridges comprising biochips comprising arrays such as nucleic acid arrays, and allow for high throughput analysis of samples.

Devices and methods for biochip multiplexing

The biosensor field has grown enormously since the first demonstration of the biosensor concept by Leland C. Clark, Jr. in 1962. Today's biosensor market is dominated by glucose biosensors, mass-produced enzyme electrodes for the rapid self-diagnosis of blood glucose levels by diabetes sufferers. Here we take a historical look at the inception, growth, and development of the enzyme biosensor field from a commercial viewpoint. The current status of the technology is evaluated and future trends in this dynamic and fastmoving field are also anticipated.

Enzymatic biosensors

Screen-printed three-electrode amperometric sensors incorporating L- and/or D-amino acid oxidase for the general purpose measurement of L- or D-amino acids is described. The working electrode incorporates rhodinised carbon, to facilitate hydrogen peroxide oxidation at a decreased operating potential, and immobilised enzyme. The devices responded to all 20 common L-amino acids and all of the D-amino acids examined, the exceptions being L- and D-proline. Linear response profiles were observed for L-leucine, L-glycine and L-phenylalanine with limits of detection of 0.47, 0.15 and 0.20 mM respectively. The devices were reproducible and exhibited stability over a 56 d test period. The biosensor compares favourably with a standard photometric amino acid test and was used to monitor milk ageing effects. The assay is cheap, simple to perform and rapid, requiring only buffer–electrolyte and a small sample volume.

Screen-printed amperometric biosensors for the rapid measurement of L- and D-amino acids

A backing sheet (101) is provided with a pattern of pathways (131, 132, 133) of e.g. silica or cellulose by a printing process (e.g., screen printing). There may be multiple pathways leading from an eluant application region (117) to a detection zone (116) and thence to a waste reservoir (118). Different pathways may have different fluid traversal times because they differ in length and/or material (e.g., nitrocellulose for slow traversal and fibrous cellulose for rapid traversal by an aqueous liquid). Thus analyte and reagents deposited at depots (112, 113) on different pathways are sequentially delivered to the detection zone. Reagents may be applied by printing. The detection zone may have an electrode assembly (105), also applied by printing, for detecting the effects of analyte.

Printed fluid transport devices

The invention described in this document relates to
methods and apparatus used to perform diagnostic assays in
which the means of detection is based on electrochemical
methods. The detection of specific analytes is facilitated by
the use of labeled materials that are capable of generating
electrical signals under a given set of assay conditions.
The preferred labels are enzymatic in nature and operate by
generating or consuming electrochemically active species in
the assay environment. The assay is performed in a suitable flow cell or
flowing liquid system device, incorporating a solid phase
material located such that it is in intimate contact with
the liquid being passed through the flow cell or flowing
liquid system and also in close proximity to a working
electrode. This electrode is poised at an appropriate
potential against a reference electrode and is able to
detect electrochemically active substances in the
surrounding liquid. Normally the flow cell or flowing
liquid system will also house a reference electrode and, if
required, a counter electrode. In a typical embodiment, a sample suspected of
containing the analyte to be detected is mixed with a
molecular species having specific binding affinity for this
analyte. This molecular species is conjugated to an enzyme
label. The labeled specific binding molecule- analyte
complex is then immobilized onto the solid phase material,
located in the vicinity of the working electrode. The flow
cell or flowing liquid system is then rinsed with a 
solution prior to the addition of substrate solution for
the enzyme label. The enzyme label serves to convert the
substrate to a product, the extent of the reaction being
related to the amount of bound analyte present. The
depletion/production of electro-active material is
monitored at the working electrode. The methods and devices described by this invention
are particularly suited for samples containing species that
cause interference in conventional assays. The flow cell
or flowing liquid system design allows removal of such
species prior to measurement.

Detection of analytes using electrochemistry

The development of a simple electrochemical immunoassay procedure for the field-based quantification of the herbicide 2,4-D in methanolic soil extracts is presented. The sensor utilizes a competitive immunoassay format incorporating an immobilized antigen complex at the surface of a disposable screen-printed working electrode element. The extent of glucose oxidase-labeled antibody binding to the antigen−electrode is determined amperometrically and is related to sample analyte concentration. The performance of the sensor is assessed in buffer, 30% methanol, and methanolic soil extracts. The device is capable of quantifying 2,4-D in all three matrixes at the low ppm level with coefficient of variation values of 6.2−33.6%. The causes of the variation observed in the sensor response in different soil matrixes are examined and improvements proposed. The sensor, tested in parallel with a commercial 2,4-D immunoassay test kit, yields comparable quantitative data and detection limits while exhibiting greater assa...

Steven Setford

Papers

Enzymatic biosensors

Screen-printed amperometric biosensors for the rapid measurement of L- and D-amino acids

Printed fluid transport devices

Detection of analytes using electrochemistry

Immunosensor for 2,4-dichlorophenoxyacetic acid in aqueous/organic solvent soil extracts.