Written by: Sam Taylor. Revised by: Maria Ines Berrojo Romeyro Mascarenhas
It’s all well and good having influenza attached to its antigen floating around in our biosensor, but how do we actually detect it? Transducers are the solution by developing a method to take the influenza-antibody binding, into a real, detectable signal. Depending on the binding reaction, this could be a temperature change, a pH change, fluorescent, etc. The most investigated and commercial biosensors use changes in the optical and electrochemical properties to obtain a signal proportional to the concentration of influenza virus and outlined below is a brief introduction of some common techniques.
Surface plasmonic resonance (SPR)
The resonant oscillation of electrons in a metal (such as a gold surface) is stimulated by incoming light at a particular angle. The resonating electrons introduce an electromagnetic surface wave that propagates along the boundary of the metal and non-metal interface. This resonant angle of the incoming light is dependent on the conduction electrons, which in turn are dependent on any attached material to the metal surface. This can be utilized by attaching an immobilized partner (the blue cross) which attaches to, for example, a specific antibody.
The attached antigen to the immobilised partner will be detected by a shift in the resonant angle of the incoming light as shown above.
Localised surface plasmonic resonance (LSPR)
Taking advantage of the phenomena above, the technique can be minimised using gold nanoparticles instead of the gold surface. This reduces the amount of required gold, allows the nanoparticles to float around in the solution and localises the electromagnetic field to the nanoparticle surface (increasing the techniques specificity). This techniques and variations of it have already been used to detect the influenza virus.
For further reading on this technique, please follow the links below.
Videos:
- 1-hour long explanation of SPR
- 10-minute comparison of SPR and LSPR
- 1-hour long in-depth SPR (lecture style)
- SPR animation
Papers
- SPR slow for influenza
- Nanoparticles: Many shapes
- Review of LSPR
- LSPR detection of HIV-1 (with schematics)
- LSPR Influenza detection
- Plasmonic Biosensing Schemes for Virus Detection
- Best paper one LSPR and future
- LSPR Advances and approaches
- LSPR Influenza
- LSPR example in Respiratory
- LSPR NS1
- LSPR quantum dots: Influenza (2017)
- LSPR Quantum dots: Influenza (2020)
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