Surface Plasmon Resonance Biosensor Technique

Very recently, a so-called surface plasmon resonance (SPR) biosensor technique has been developed that allows the differentiation and prediction of the degree of 

POPC/GM1 POPC b) Sensor Chip L1 and attachment of liposomes 

probably because of the deeper partitioning of the drugs into this stationary phase. 

I AM column chromatography has also been used to predict the transdermal transport of drugs [42], The retention time, log kw (capacity factor extrapolated to 100% aqueous phase at pH 5.5, IAM column) and log Poet. were compared for the studied drugs (Tables 4.11 and 4.12). The coefficients of permeability through human skin, Kp, were not correlated with either log fcw or log Poet.. The authors had, however, pre- 

This relationship was used to calculate log kw and the difference from the observed log kw values was used to describe the skin permeability, Kp (Alog kwand log Poet. were not significantly intercorrelated, r = 0.61). 

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P. M. Fratamico, T. P. Strohaugh, M. B. Medina, and A. G. Gehring, "Detection of Escherichia coli 0157 H7 Using a Surface Plasmon Resonance Biosensor," Biotechnology Techniques 12, 571-576 (1998). 

Surface plasmon resonance (SPR) technique had become popular in interaction studies between biological molecules (1). It is an optical biosensor, and the interactions can be detected by SPR angle shift or reflection light intensity. In typical SPR measurement, one of pair interacting biomolecules was immobilized on a gold chip, and another was flowed over the chip as its solution. There are two major advantages in SPR assay (a) real time evaluations on kinetics studies and (b) label-free measurements. 

Biosensors offer a unique solution to vitamin B12 analysis in terms of specificity and time-saving commercial biosensors are available in several forms such as autoanalysers, manual laboratory instruments and portable (handheld) devices. One biosensor system, Biacore Q, is based on optical detection— the surface plasmon resonance (SPR) technique for vitamin Bi2 analysis. 

Apart from the classification based on sensing mechanisms, biosensors are classified into three categories considering the transduction mechanism used. They are optical, electrochenfical, or electrical. The optical transduction mechanism includes fluorescence, chemilununescence, interferometry, and surface plasmon resonance. These techniques involve either the production of light from chemical reactions or the change in refractive index at the interface of biosensing materials. 

The results summarized above were obtained by using fluorescence based assays employing phospholipid vesicles and fluorescent labeled lipopeptides. Recently, surface plasmon resonance (SPR) was developed as new a technique for the study of membrane association of lipidated peptides. Thus, artificial membranes on the surface of biosensors offered new tools for the study of lipopeptides. In SPR (surface plasmon resonance) systemsI713bl changes of the refractive index (RI) in the proximity of the sensor layer are monitored. In a commercial BIAcore system1341 the resonance signal is proportional to the mass of macromolecules bound to the membrane and allows analysis with a time resolution of seconds. Vesicles of defined size distribution were prepared from mixtures of lipids and biotinylated lipopeptides by extruder technique and fused with a alkane thiol surface of a hydrophobic SPR sensor. 

Immunosensors have been developed commercially mostly for medical purposes but would appear to have considerable potential for food analysis. The Pharmacia company has developed an optical biosensor, which is a fully automated continuous-flow system which exploits the phenomenon of surface plasmon resonance (SPR) to detect and measure biomolecular interactions. The technique has been validated for determination of folic acid and biotin in fortified foods (Indyk, 2000 Bostrom and Lindeberg, 2000), and more recently for vitamin Bi2. This type of technique has great potential for application to a wide range of food additives but its advance will be linked to the availability of specific antibodies or other receptors for the various additives. It should be possible to analyse a whole range of additives by multi-channel continuous flow systems with further miniaturisation. 

Very few immunosensors are commercially available. The commercial immunosensors are either the detector or bioanalyzer types. The PZ 106 immunosensor from Universal Sensors Inc. (New Orleans, LA) has been used as a detector to measure antibody-antigen reaction. Ohmicron (Newtown, PA) developed a series of pesticide immuno-bioanalyzers that have been used in field tests. Pharmacia Biosensor USA (Piscataway, NJ) recently introduced BIAcore immunodetection system. A combination of a unique flow injection device and surface plasmon resonance (SPR) detection technique provides a real time analysis. A carboxylmethyldextran layer added to plasmon generating gold film is a hydrophobic, activatable, and flexible polymer that provides high antibody and low non-specific bindings. System demonstration at the Institute of Food Technologists (IFT) 1994 meeting in Atlanta drew attention of food scientists. It should easily be adapted for food protein characterization. 

While it is safe to say that SPR is a mature technique from the historical perspective, new driving forces appear to challenge traditional SPR for various needs that traditional SPR sensors fail to satisfy. In particular, a novel SPR biosensor that attempts to capitalize on the nanotechnology, by which to localize surface plasmons (SPs), has emerged and thus has been appropriately called a localized surface plasmon resonance (LSPR) biosensor. In this chapter, 1 focus on the LSPR biosensor by reviewing its operating principles and properties in a systematic way and venture into future directions along which LSPR biosensors evolve. 

Fiber-optic biosensors are analytical devices in which a fiber optic device serves as a transduction element. The usual aim of fiber-optic biosensors is to produce a signal proportional to the concentration of target analyte to which the biological element reacts. Fiber-optic biosensors are based on the transmission of light along silica glass fiber, or POF to the site of analysis. They can be used in combination with different types of spectroscopic technique, e.g. absorption, fluorescence, phosphorescence, or surface plasmon resonance (SPR) (14). 

The reaction between the analjrte and the bioreceptor produces a physical or chemical output signal normally relayed to a transducer, which then generally converts it into an electrical signal, providing quantitative information of analytical interest. The transducers can be classified based on the technique utilized for measurement, being optical (absorption, luminescence, surface plasmon resonance), electrochemical, calorimetric, or mass sensitive measurements (microbalance, surface acoustic wave), etc. If the molecular recognition system and the physicochemical transducer are in direct spatial contact, the system can be defined as a biosensor [76]. A number of books have been published on this subject and they provide details concerning definitions, properties, and construction of these devices [77-82]. 

Most optical detection methods for biosensors are based on ultra-violet (UV) absorption spectrometry, emission spectroscopic measurement of fluorescence and luminescence, and Raman spectroscopy. However, surface plasmon resonance (SPR) has quickly been widely adopted as a nonlabeling technique that provides attractive advantages. Fueled by numerous new nanomateiials, their unique, SPR-based or related detection techniques are increasingly being investigated [28-31]. 

Liedberg B. and Johansen K., Affinity biosensing based on surface plasmon resonance detection, in Biosensors Techniques and Protocols, ed. K. Rogers and A. Mulchandani (Totowa, NJ Humana Press 1998) Meth. BiotechnoL, 1, 31-54, 1998. 

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