Multianalyte Sensors Research Articles

Potentiometric ion-selective silicon sensors for the on-line monitoring of blood electrolytes

A non-invasive on-line monitoring system for blood electrolytes has been developed on the basis of potentiometric ion-selective silicon sensors. The microsensors were fabricated in the patented containment technology owned by ICB. Additionally, multianalyte sensors with two and three containment sensor elements integrated on chip were realized. The new polysiloxane membrane functionalized with trifluoropropyl groups with improved adhesion on the silicon oxide surface were used as matrix membrane for all prepared solid state microsensors. The following containment sensors have been developed: potassium, calcium, sodium, and pH. They were characterized in physiological test solutions. The excellent reliability of the potassium sensors has been demonstrated successfully in clinical trials with real circulating whole blood samples and on extracorporal animal blood circulation. First simultaneous measurements of potassium, sodium and pH have also been performed in vitro using human blood samples.

Capture of a single molecule in a nanocavity.

We describe a heptameric protein pore that has been engineered to accommodate two different cyclodextrin adapters simultaneously within the lumen of a transmembrane beta barrel. The volume between the adapters is a cavity of approximately 4400 cubic angstroms. Analysis of single-channel recordings reveals that individual charged organic molecules can be pulled into the cavity by an electrical potential. Once trapped, an organic molecule shuttles back and forth between the adapters for hundreds of milliseconds. Such self-assembling nanostructures are of interest for the fabrication of multianalyte sensors and could provide a means to control chemical reactions.

Towards multianalyte molecule-based sensors: reactivity and photophysical behaviour of hemilabile ligand-containing Ru(II) bipyridyl complexes

The concept of using hemilabile ligand-containing complexes as the basis for multianalyte sensors is introduced: the preparation of two such ruthenium complexes (1 and 2) and their reactivity towards a series of donor molecules is reported; differential photoluminescence and absorption responses are observed.

Antibodies for immunosensors a review

Immunosensors (ISs) are miniaturized measuring devices, which selectively detect their targets by means of antibodies (Abs) and provide concentration-dependent signals. Ab binding leads to a variation in optical properties, electric charge, mass, or heat, which can be detected directly or indirectly by a variety of transducers. The quality of ISs primarily depends upon the selectivity and affinity of the Abs used in the receptor unit. Since sensitivity is directly related to the affinity of the ligand binding, reversibility excludes high sensitivity. Consequently, detection units for single-use and quasi-continuous measuring devices are presently preferred. An important future development is seen in the field of multianalyte sensors. The most attractive application is based on Abs with sufficiently different cross-reactivities. The response pattern provides information on the presence and concentration of structurally similar analytes, as they are found for instance in pesticide groups such as the s-triazines. It is obvious that this development will be significantly accelerated by applying recombinant techniques for Ab production. The next step is directed toward the generation of recombinant Ab libraries, which will provide a huge repertoire, generated at the DNA level, for new Ab types.

Microelectronic and nanoelectronic interfacing techniques for biological systems

A variety of electronic and opto-electronic interfacing techniques for the transduction of biological signals is available which utilise technology normally accessed for microelectronic and nanoelectronic semiconductor device fabrication. Correct interfacing of electronics to biological systems leads to the possibility of creating a range of devices which are capable of being used as biosensors or as monitoring units for individual biological cells. This can be thought of as 'bioelectronic interfacing'. Fabrication of these devices at the microelectronic scale leads to the creation of multi-analyte sensors or electrode arrays 'on chip'. There are many application areas for these devices, ranging from disposable multi-analyte sensors for use in the general practitioner's office to novel research tools allowing the monitoring of networks of neural cells in vitro. The Bioelectronics Research Group at the University of Glasgow has fabricated and tested multi-microelectrode devices for monitoring biological cells in culture. Electrical signals have been recorded extracellularly from individual neural and cardiac cells in vitro; the adhesion and movement of individual cells have been monitored on microelectrodes via electrical impedance techniques. The devices can be adapted as multi-analyte biosensors by immobilising a range of biological molecules on the electrode array. It is possible to further utilise micro- and nano-fabrication techniques to provide patterned molecular arrays for sensors, cell guidance or molecular electronic applications on planar surfaces. One important future application of this might be in nerve repair where guidance cues could be provided for nerve regrowth on surfaces and some examples of this will be shown. At the smallest scale, we are now trying to image and interact with biological molecules on these surfaces using scanning tunnelling microscopy. Possible benefits of this might be better fabrication and immobilisation of molecules for biosensors and the optimisation of surface biocompatibility treatment.

A fibre-optic chemical sensor with discrete sensing sites

A LONG-standing goal of clinical medicine has been the continuous, in situ measurement of solute concentrations (such as pH, pCO2and pO2), particularly in blood. Blood monitoring is accomplished at present by analysing discrete samples at a centralized, remote clinical laboratory, causing delays between sampling and analysis. Most multi-analyte sensors developed for 'bedside' in situ monitoring1 consist of several sensors fabricated into a sensor array or bundle2,3. This approach is not ideal where sensor size is an important factor. Here we describe a technique that enables the development of a compact, multi-analyte fibre-optic chemical sensor. The technique is based on localized photopolymerization of appropriate dye indicators on the face of an imaging fibre. The sensing sites fluoresce to a degree controlled by analyte concentration, intensities being monitored simultaneously with an enhanced charge-coupled device (CCD) video camera. We present results from a sensor that contains three individual pH-sensitive areas, and indicate how multi-analyte sensitivity may be achieved.