Biosensing device

To use the OFRR as a biosensing device, the optical resonant mode is excited and the resonant frequency is measured continuously in real time. The conceptual measurement setup is illustrated in Fig. 14.3. Laser light from a distributed feedback (DFB) laser is delivered to the OFRR using fiber optic cable. One method that has been used to excite the resonant modes is to place a tapered fiber optic cable with a diameter less than 4 pm in contact with the OFRR. The evanescent field of the tapered fiber overlaps with the evanescent field outside of the capillary wall, which enables mode coupling between the two media24. 

The utility of Av-GEB platform was demonstrated for the determination of the mecA DNA sequence related with methicillin-resistant S. aureus (MRSA) [67] in a simpler and specific manner with respect to previous DNA biosensing devices [58,65,66]. 

However, electrochemically based transduction devices are more robust, easy to use, portable, and inexpensive analytical systems [45]. Furthermore, electrochemical biosensors can operate in turbid media and offer comparable instrumental sensitivity. Many electrochemical sensing and biosensing devices were reported [46-48]. 

A recent application of a tetracianoquinodimethane (TCNQ)-modi-fied SPE for the development of a biosensing device for chlorpyrifos methyl was also reported. This method was demonstrated to detect the active molecule both in standard solution and in commercial products (Reldan 22) with comparable sensitivity. The analytical protocol was then applied to grapes and vine leaf samples in order to improve safety in wine-making process [27]. 

This volume of the series focuses on the photochemistry and photophysics of metal-containing polymers. Metals imbedded within macromolecular protein matrices form the basis for the photosynthesis of plants. Metal-polymer complexes form the basis for many revolutionary advances occurring now. The contributors to many of these advances are authors of chapters in this volume. Application areas covered in this volume include nonlinear optical materials, solar cells, light-emitting diodes, photovoltaic cells, field-effect transistors, chemosensing devices, and biosensing devices. At the heart of each of these applications are metal atoms that allow the assembly to function as required. The use of boron-containing polymers in various electronic applications was described in Volume 8 of this series. 

Optical sensors are interesting analytical tools capable of performing a variety of different measurements [19]. Most of the work has been done on measuring pH, 02 and C02 but biosensing devices were also developed and marketed [19-22]. 

The biosensing devices focus mainly on affinity principles such as antibody -antigen reactions and are based on surface plasmon resonance [25], grating couplers[26] or interferometers [27]. It seems possible to get stable and highly sensitive devices based on these principles [28], and further investigations can lead to miniaturized sensor modules with reduced cost, size and complexity. 

Despite their potential importance, there are few analytical models of whole cell biosensing devices—particularly when compared to the plethora of models describing enzyme based biosensors [62]. Although aspects of cellular biochemistry are similar to those of isolated enzymes [63], problems arise in modelling the physicochemistry of whole cells due to their complex nature they are large (typically 0.2-10 jxm) they may contain a variety of biological structures (membranes, organelles, etc.) they incorporate a diversity of biochemical pathways and they may contain many types of active site. 

Localized surface plasmon (LSP) The surface plasmon (SP) cannot propagate on the surface of metallic nanoparticles and therefore, is localized and hence known as localized surface plasmon (LSP). The LSP resonance of gold and silver NPs occurs in the visible range of the spectrum, which makes these two metals particularly useful for a number of applications ranging from ultrasensitive diagnostic tools to biosensing devices. 

In any case, both biosensors and biosensing devices have been coupled to microdialysis and are considered among the non-separation-based methods [83]. The drawback of biosensing approaches is that they are usually able to measure just one analyte at a time, in contrast with separation-based methods such as chromatography and electrophoresis, which allow the detection of several analytes. However, if the primary interest is not the identification of unknown compounds, but, for example, the monitoring of variations in a single metabolite or drug, the optimization of therapeutic responses, or the control of a bioprocess via a marker analyte, the use of a specific sensor, which can be employed in a continuous manner, can provide useful information, and can also help to avoid the analysis of hundreds of samples or to reduce the number of animals necessary for a study. 

The previously mentioned drawback of biosensing devices, i.e., the possibility to measure just one metabolite at a time, is nowadays partially overcome through the recent advances in miniaturization and the development of arrays of sensors. Each of the sensors constituting the array can consist in a different biosensor, allowing multi-analyte determinations. In some cases, if the array is located in a flow cell, it can be coupled to microdialysis sampling. Examples have been presented by several authors, even if the proposed... 

Functionalization of CNTs by covalent chemistry. Covalent functionalization of CNTs has attracted a great interest for biosensors development. This t5T)e of functionalization is expected to play a crucial role in tailoring the properties of materials and the engineering of CNT biosensing devices. The first step in a covalent functionalization process involves a chemical treatment of CNTs under oxidizing conditions, such as sonication in a mixture of sulfuric and nitric acids or treatment with piranha... 

Nagel M, Forst M, Kurz H (2006) THz biosensing devices fundamental and technology. J Phys Condens Matter 18 S601-S618... 

The aim of our study is to fabricate an extremely high-performance ion and biosensing device. In onr work, we have studied the fabrication of FET-based ion and biosensor using self-assembled monolayers (SAMs) [5-9]. Onr concept and details of device architectnre are described in the following lines. 

Niwa D, Yamada Y, Homma T, Osaka T (2004) Formation of molecular templates for fabricating on-chip biosensing devices. J Phys Chem B 108 3240-3245... 

There have been two main approaches taken toward developing such biosensing devices, and the current state of each will be described below. 

Nowadays, the construction of electrochemical biosensors based on the use of gold nanoparticles constitutes an intensive research area because of the unique advantages that this nanomaterial lends to biosensing devices. So, gold nanoparticles provide a stable surface for immobilization of biomolecules with no loss of their biological activity. Moreover, they facilitate direct electron transfer between redox proteins and electrode materials, and constitute useful interfaces for the electrocatalysis of redox processes of molecules such as H202 or NADH involved in many biochemical reactions (1, 2). 

---