This document discusses single molecule detection using localized surface plasmon resonance of gold nanoparticles. It notes that single molecule detection is needed for early disease detection but current labeling techniques are destructive, not real-time, and don't allow virus information extraction. Label-free detection monitors inherent optical and dielectric properties but has sensitivity and specificity issues. Localized surface plasmon resonance exploits the resonant oscillation of conduction electrons in gold nanoparticles stimulated by light, producing a shift in resonant frequency when the refractive index changes due to molecule binding. This enables label-free single molecule protein detection using a single plasmonic nanoparticle sensor.

1. Real time detection of bio-nanoparticle using
localised surface plasmon
Presented by:
Amit Kumar Tagore
M.Tech. 1st year(1411NT02) Nanoscience & Technology
IIT Patna

2. Outline
Why single molecule detection needed.
 Detection with labels and its disadvantages.
 Label free detection.
 Localized Surface Plasmon Resonance of Gold Nanoparticles.
 Different illumination techniques.
 Conclusion.

3. 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.

4. Detection with labels
Single molecule is
fluroscence labeled

5. Contd…

6. Drawback of detection with labels
• 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

7. 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.

8. • Fibre-optic biosensors
• Fabry-Perot interferometers
• Interferometric biosensors
• Optical resonance of a microresonator
• Localized surface plasmonic biosensors
• Surface Plasmon biosensors
Optical
Plasmonic

9. Localized Surface Plasmon Resonance
• 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.

10. Nanosphere

11. Contd…

12. Nanoellipsoidal

13. Localized Surface Plasmon Resonance of Gold Nanorod

14. Wavelength shift

16. Single Unlabeled Protein Detection on Individual Plasmonic
Nanoparticles
Irene Ament,† Janak Prasad,†,‡ Andreas Henkel,† Sebastian Schmachtel,†
and Carsten Sönnichsen*,†
†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

17. 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.