Biacore surface

Gershon P.D., Khilko S., Stable chelating linkage for reversible immobilization of oligohistidine tagged proteins in the BIAcore surface plasmon resonance detector, J Immun Methods 1995 183 65-76. 

O Shannessy, D.J., Brigham-Burke, M., Peck, K. (1992). bnmobilization chemistries suitable for use in the BIAcore surface plasmon resonance detector. Analytical Biochemistry, 205, 132-136. 

Other assays typically employed in the course of a drug design project include physicochemical binding assays (based on, for example, NMR or Biacore surface plasmon resonance methodologies), mode-of-action cell assays (e.g., employing a specific antibody-based biomarker readout of the target or a downstream target), and phenotypic assays (e.g., cell proliferation assays). 

Figure 7.9. Schematic diagram of a surface plasmon resonance biosensor. One of the binding partners is immobilized on the sensor surface. With the BIACORE instrument, the soluble molecule is allowed to flow over the immobilized molecule. Binding of the soluble molecule results in a change in the refractive index of the solvent near the surface of the sensor chip. The magnitude of the shift in refractive index is related quantitatively to the amount of the soluble molecule that is bound.

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. 

SPR chips coated with a carboxymethyl dextran matrix are supplied commercially by Biacore, a leading manufacturer of SPR instruments. Similar technique can be used for preparation of carboxymethyl dextran matrix on Me(Si)Ox surfaces on which -OH groups are generated by reaction with 3-glycidoxypropyltrimethoxysilane13. 

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. 

Screening in early work sought to identify high affinity of the antibody for the TSA, using a process known as ELISA. This search can now be performed more quantitatively by BIAcore analysis, based on surface plasmon resonance methodology (Lof s and Johnsson, 1990). A subsequent development is the catELISA assay (Tawfik et al., 1993), which searches for product formation and hence the identification of abzymes that can generate product. 

Incubahon with sAV led to the creation of the sAV monolayer. This surface was used exclusively with the BlAcore system (Biacore International... 

Pharmacia Biosensor AB, Uppsala, Sweden BIAcore Immunologic surface plasmon resonance Biomoiecular interactions... 

Jongerius-Gortemaker, B. G. M., Goverde, R. L. J., van Knapen, F., and Bergwerff, A. A. (2002). Surface plasmon resonance (BIACORE) detection of serum antibodies against Salmonella enteritidis and Salmonella typhimurium. J. Immunol. Methods 266,33-44. 

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. 

SPR method is currently well established and used in analysis of affinity interactions. The commercial instruments produced by Biacore AB or Texas Instruments are available in the market. Substantial progress in SPR instrumentation is connected also with the possibility to detect simultaneously the affinity interaction from several surfaces [72], This approach has been proved equally effective for detection of thrombin-DNA aptamer interactions [36]. 

The avidin-biotin interaction has also been used to immobilize antibodies and proteins, especially in commercial systems based on surface plasmon resonance (SPR) measurements (e.g., the BIAcore). The extraordinary affinity (Kl 10-15 M) of avidin (or its bacterial relative, streptavidin) for the vitamin biotin is the basis of this immobilization procedure. A solid support (e.g., glass beads, sensor chip, optical fiber) covered with avidin can be used as an activated carrier for a very sturdy immobilization of previously biotinylated antibodies. In spite of the many methods for biotinylating proteins described in the literature, the use of biotinyl N-hydroxysuccinimide ester (BNHS) and similar derivatives, remains the most useful [65]. 

---