Background
Biosensors are biochemical analysis instruments combining a biochemical recognition element with a physical measurement device. The use of biosensors is well established within biochemical and medical research, drug development, food quality assessment, homeland security, and environmental technology [1, 2]. Most commercial biosensor systems utilize some kind of optical measurement principle.
Surface Plasmon Resonance (SPR) is the physical principle utilized in most optical biosensors [3, 4]. SPR is widely used in biomolecular analysis, and is especially advantageous for measuring reaction kinetics, affinity, and concentration in real time. Although the use of SPR for biomolecular interaction analysis is well established, the technology still suffers from a number of technical limitations [5, 6]:
- Limited sensitivity: The sensitivity does not compare favourably with other highly sensitive methodologies such as fluorescence. Also, the detection limit is adversely affected by different sources of noise, such as temperature, pressure, and bulk concentration variations.
- Limited specificity: SPR is a non-specific detection method, i.e. any substance that adsorbs onto the sensor surface is detected. Non-specific adsorption is a very common problem.
Signal enhancement technology
The signal enhancement technology from Episentec is based on proprietary dye labelling reagents, methods, and software, and offers a simple and elegant solution to these problems:
- Enhanced sensitivity: The signal-to-noise ratio is increased 100-fold on a mass basis. This is due to the strong signal from the dye entity as well as to a reduction of several kinds of noise.
- Enhanced specificity: The measurement is fully specific with respect to the dye label. This means that only the dye entity as such is detected, while non-specifically adsorbed uncoloured substances are not.
Users can benefit from the signal enhancement technology without making any changes to the standard SPR instrument hardware. Furthermore, the setup allows conventional, universal SPR detection to be performed simultaneously and in parallel with enhanced detection, effectively converting the instrument into a multimodal reader. This gives the user full flexibility in terms of running label-free and labelled assay formats.
Enhanced sensitivity
The enhanced sensitivity is highly advantageous when working with low sample concentrations and with small molecules, and allows the user to monitor weaker and slower molecular interactions than is possible with conventional SPR. In addition, lower levels of immobilization can be used, which reduces crowding and undesirable cooperative binding effects, and minimises mass transport problems. The enhanced sensitivity also reduces the consumption of scarce reagents and expensive consumables, ultimately saving the end-user time and money.
Enhanced specificity
The enhanced specificity reduces the problem of non-specific adsorption of sample compounds, which is highly advantageous when working with complex biochemical samples. Furthermore, the extra information obtained when running enhanced dye-labelled SPR and conventional SPR in parallel turns SPR into a significantly more information-rich technique.
Summary
In summary, Episentec offers SPR users significantly improved performance and the ability to develop new kinds of applications, while in many cases increasing the flexibility, simplifying the workflow, increasing the information content, and lowering the cost.
References
- R. L. Rich, D. G. Myszka “Grading the Commercial Optical Biosensor Literature – Class of 2008: The Mighty Binders” J. Mol. Recognit. 2010, 23, 1-64.
- M. A. Cooper (Ed.) “Label-Free Biosensors: Techniques and Applications” Cambridge University Press, Cambridge, 2009.
- J. Homola (Ed.) “Surface Plasmon Resonance Based Sensors” Springer Verlag, Berlin, 2006.
- R. B. M. Schasfoort, A. J. Tudos (Eds.) “Handbook of Surface Plasmon Resonance” RSC Publishing, Cambridge, 2008.
- J. Homola “Surface Plasmon Resonance Sensors for Detection of Chemical and Biological Species” Chem. Rev. 2008, 108, 462-493.
- M. Piliarik, J. Homola “Surface Plasmon Resonance (SPR) Sensors: Approaching their Limits?” Opt. Express 2009, 17, 16505-16517.