SPR biosensors

Danelian, E., Karlen, A., Karlsson, R., Winiwarter, S., Hansson, A., Lofas, S., Lennernas, H., Hamalainen, D. SPR biosensor studies of the direct interaction between 27 drugs and a liposome surface correlations with fraction absorbed in humans./. Med. Chem. 2000, 43, 2083-2086. 

New developments in immobilization surfaces have lead to the use of SPR biosensors to monitor protein interactions with lipid surfaces and membrane-associated proteins. Commercially available (BIACORE) hydrophobic and lipophilic sensor surfaces have been designed to create stable membrane surfaces. It has been shown that the hydrophobic sensor surface can be used to form a lipid monolayer (Evans and MacKenzie, 1999). This monolayer surface can be used to monitor protein-lipid interactions. For example, a biosensor was used to examine binding of Src homology 2 domain to phosphoinositides within phospholipid bilayers (Surdo et al., 1999). In addition, a lipophilic sensor surface can be used to capture liposomes and form a lipid bilayer resembling a biological membrane. 

Williams, C., and Addona, T. A. (2000). The integration of SPR biosensors with mass spectrometry possible applications for proteome analysis. Trends Biotechnol. 18, 45-48. 

SURFACE PLASMON RESONANCE (SPR) BIOSENSORS AND THEIR APPLICATIONS IN FOOD SAFETY AND SECURITY... 

Abstract Surface plasmon resonance (SPR) biosensors show vast potential for detection... 

SPR biosensors are label-free detection devices - binding between the biomolecular recognition element and analyte can be observed directly without the use of radioactive or fluorescent labels. In addition, the binding event can be observed in real-time. SPR affinity biosensors can, in principle, detect any analyte for which an appropriate biomolecular recognition element is available. Moreover, analyte molecules do not have to exhibit any special properties such as fluorescence or characteristic absorption or scattering bands. 

An SPR biosensor consists of two key elements - an optical system for excitation and interrogation of surface plasmons and a biospecific coating incorporating biomolecular recognition elements which interact with target molecules in a sample. 

SPR BIOSENSORS FOR DETECTION OF ANALYTES IMPLICATED IN FOOD SAFETY... 

SPR affinity biosensors have been developed to detect an analyte in a variety of formats. The choice of detection format for a particular application depends on the size of target analyte molecules, binding characteristics of available biomolecular recognition element, and range of concentrations of analyte to be measured. The main detection formats used in SPR biosensors include direct detection (Fig. 11), sandwich assay (Fig. 12) and inhibition assay (Fig. 13). 

SPR biosensor-based detection of food contaminants, food-borne pathogens and toxins... 

Major chemical contaminants implicated in food safety include pesticides, herbicides, myeotoxins and antibiotics. These analytes have been targeted by numerous groups developing SPR biosensors. As these analytes are rather small (typical molecular weight < 1,000), inhibition assay has been a preferred detection format. Examples of chemical contaminants detected by SPR biosensors include pesticides atrazine and simazine (detection limits 0.05 ng/ml and 0.1 ng/ml respectively), mycotoxin Fumonisin B1 (detection limit 50 ng/ml ), and antibiotics Sulphamethazine, Sulphadiazine (detection limits 1 ng/ml and 20 ng/ml respectively). 

Molecular weight of the main bacterial toxins ranges from 28,000 to 150,000, which makes it possible for most sensitive SPR biosensors to measure their concentrations directly or using a sandwich assay. Examples of food safety-related toxins detected by SPR biosensors include Botulinum toxin (detection limit 2.5 pg/ml " ), . coli enterotoxin (detection limit 6 pg/ml " ) and Staphylococcal enterotoxin B (detection limit 5 ng/ml and 0.5 ng/ml for direct detection and sandwich assay, respectively" ). 

Figure 15. Detection of Staphylococcal enterotoxin B using an SPR biosensor. Sensor response as a function of SEB concentration.

Bacterial pathogens are relatively large targets (> 1pm) and therefore, their presence can be detected directly with an optional amplification by secondary antibodies (sandwich assay). Examples of foodbome bacterial pathogens detected by SPR biosensors include Escherichia coli (detection limit 5x10 cfii/ml " " ), Listeria monocytogenes (detection limit 1 O cfii/ml " ) and Salmonella enteritidis (detection limit lO cfii/ml" ). 

The performance of the inhibition immunoassay enables the SPR biosensor to monitor the immunoreaction between the hapten immobilized... 

On the other hand, limited advances have been made with regard to the development of biosensors toward the detection of this group of compounds. Marchesini et al. [92], reported on an SPR biosensor based on the thyroxine (T4) transport disrupting activity to screen chemicals (including PBDEs) that may interfere with the thyroid system [92]. 

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