detection of single molecules
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Real time detection of bio-nanoparticle using localised surface plasmon
Presented by:Amit Kumar Tagore
M.Tech. 1st year(1411NT02) Nanoscience & Technology
IIT Patna
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OutlineWhy single molecule detection needed.
Detection with labels and its disadvantages.
Label free detection.
Localized Surface Plasmon Resonance of Gold Nanoparticles.
Different illumination techniques.
Conclusion.
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Why single molecule detection needed?
• Virus detection is dead easy.
• Early stage detection of cancer.
• All dangerous disease can be detected at very early stage.
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Detection with labels
Single molecule is fluroscence labeled
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Contd…
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• Fluorescent labels are necessary (destructive technique)
• Not a real time detection (not useful in doctor’s office)
• Extraction of virus information is impossible
• Selective virus detection is difficult
• Multi-virus detection is difficult
Drawback of detection with labels
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Label free detection technique
• This technique monitor inherent properties of the molecules such as mass, optical and dielectric properties.
• Unlike label-based detection methods, these techniques avoid any tagging of the query molecules thereby preventing changes in structure and function.
• They do not involve laborious procedures but have their own pitfalls such as sensitivity and specificity issues.
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• Fibre-optic biosensors
• Fabry-Perot interferometers
• Interferometric biosensors
• Localized surface plasmonic biosensors
• Surface Plasmon biosensors
• Optical resonance of a microresonator
Optical
Plasmonic
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• Surface Plasmon resonance (SPR) is the resonant oscillation of conduction electrons at the interface between a negative and positive permittivity material stimulated by incident light.
• The resonance condition is established when the frequency of incident photons matches the natural frequency of surface electrons oscillating against the restoring force of positive nuclei.
• A Localized Surface Plasmon (LSP) is the result of the confinement of a surface Plasmon in a nanoparticle of size comparable to or smaller than the wavelength of light used to excite the Plasmon.
• The Plasmon resonant frequency is highly sensitive to the refractive index of the environment; a change in refractive index results in a shift in the resonant frequency.
Localized Surface Plasmon Resonance
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Nanosphere
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Contd…
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Nanoellipsoidal
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Localized Surface Plasmon Resonance of Gold Nanorod
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Wavelength shift
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Single Unlabeled Protein Detection on Individual PlasmonicNanoparticles
Irene Ament,† Janak Prasad,†,‡ Andreas Henkel,† Sebastian Schmachtel,† and Carsten Sonnichsen*,††Institute for Physical Chemistry, University of Mainz, D-55128 Mainz, Germany‡Graduate School Materials Science in Mainz, Staudingerweg 9, D-55128 Mainz, Germany
Label free detection of single protein molecules using a single plasmonic particle
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Conclusion
• we can detect single molecule using label free biosensors.
• Nanoparticle based sensors provide a useful biophysical tool for the interrogation of single binding events.
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