detection of single molecules

Real time detection of bio-nanoparticle using localised surface plasmon

Presented by:Amit Kumar Tagore

M.Tech. 1st year(1411NT02) Nanoscience & Technology

IIT Patna

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.

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.

Detection with labels

Single molecule is fluroscence labeled

Contd…

• 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

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.

• Fibre-optic biosensors

• Fabry-Perot interferometers

• Interferometric biosensors

• Localized surface plasmonic biosensors

• Surface Plasmon biosensors

• Optical resonance of a microresonator

Optical

Plasmonic

• 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

Nanosphere

Contd…

Nanoellipsoidal

Localized Surface Plasmon Resonance of Gold Nanorod

Wavelength shift

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

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.