From Butterflies to Bees: Naturally Inspired Metal

From Butterflies to Bees: Naturally
Inspired Metal-Enhanced Biophotonics
by Natalie Garrett
n.l.garrett@exeter.ac.uk
Biomedical Physics Group, School
of Physics, University of Exeter
Presentation Summary
™Background:
™Biophotonics
™Raman scattering
™Metal enhancement
™Butterfly Experiment
™Future work
™Summary
™Conclusion
Background
Butterfly Experiment
Future work
Summary
Conclusion
What is Biophotonics?
10μm
Biophotonics is the general term for techniques that use light to image,
manipulate and characterise biological samples.
Laser eye surgery, white light microscopy and spectroscopy are all
common examples.
Spectroscopy is what I’m interested in, specifically Raman spectroscopy.
Background
Butterfly Experiment
Future work
Summary
Conclusion
Raman Spectroscopy
10μm
Every colour of light has a different
wavelength.
We perceive objects as having colour
because they preferentially reflect some
wavelengths of light and absorb others.
Most reflected light is scattered elastically
– it doesn’t lose any energy to the
material.
A small proportion of light will gain or lose energy in this interaction. This changes
the light’s colour and is dependent on the material’s chemical composition.
Image courtesy of:
http://commons.wikimedia.org/wiki/File:Light_dispersion_conceptual_waves.gif
Background
Butterfly Experiment
Future work
Summary
Conclusion
Raman Spectroscopy
This inelastic scattering process is named “Raman scattering”…
10μm
™Raman spectra have peaks that are unique for every chemical bond,
which give information about the chemical environment (e.g. pH,
temperature etc.)
Laser beam
Filter
http://www.mesophotonics.com/
™Since only 1 in every 107 photons scatters this way, the signal is weak.
™Increasing the laser power and scan times give a stronger signal, but
can damage biological samples.
Background
Butterfly Experiment
Future work
Summary
Conclusion
Metal Enhancement
Small, regular patterns of silver and gold can cause a 1014 x enhancement of
Raman signals (called Surface Enhanced Raman Scattering, or SERS).
Lithographically produced SERS substrates are expensive, single-use and
require liquid samples to be dried on.
Butterfly wings have been found to have nano-scale arrays of the structural
protein chitin – this gives rise to colour and iridescence.
Would they work as SERS substrates for protein binding experiments?
Aim – investigate butterfly wings for use as
SERS substrates in protein binding assays
Background
Butterfly Experiment
Future work
Summary
Conclusion
Butterfly Wings as SERS substrates
5μm
10μm
100μm
Background
Butterfly Experiment
Future work
Summary
Conclusion
Avidin/Biotin SERS Assay
™Protein binding assays are used a lot! Pregnancy tests, blood analysis, urine
screening etc.
™For a model protein binding system, we need a well-characterised protein that
binds strongly to a smaller molecule.
™Avidin (protein from hen egg white) and Biotin (binds very strongly to Avidin) were
chosen.
Background
Butterfly Experiment
Future work
Summary
Avidin/Biotin SERS Assay
Conclusion
Background
Butterfly Experiment
Future work
Summary
Conclusion
Avidin/Biotin SERS Assay
5μm
Gold (90 nm) enhancement factor:
1.9 x 106 +/- 5.8 x 104
Silver (70 nm) enhancement factor:
1.4 x 107+/- 1.7 x 105
Background
Butterfly Experiment
Future work
Summary
Conclusion
Avidin/Biotin SERS Assay
OH
O
C
OH
O
CH2
C
O
CH2
C
CH2
CH2
CH2
CH2
S
S
S
Background
Butterfly Experiment
Future work
Summary
Avidin/Biotin SERS Assay
Conclusion
Background
Butterfly Experiment
Future work
Summary
Conclusion
Results
™The ratios of the two peaks
were plotted as a function of
biotin concentration.
™The peak ratio was found to be
logarithmically dependant upon
the concentration of biotin over
several orders of magnitude.
™This assay was performed with
wet substrates – a real
breakthrough for biological SERS
assaying.
Background
Butterfly Experiment
Future work
Summary
Conclusion
Further reading…
10μm
Spectroscopy on the wing: Naturally inspired SERS
substrates for biochemical analysis
Natalie L. Garrett , Peter Vukusic, Feodor Ogrin, Evgeny Sirotkin,
C. Peter Winlove, Julian Moger
Volume 2 Issue 3, Pages 157 - 166
Background
Butterfly Experiment
Future work
Summary
Conclusion
Bees and Beyond: CCD
The protein assaying capabilities of the wing substrates
have been proven.
10μm
The system needs to be tested for a real-world problem.
Global bee populations are dramatically declining as a result of Colony
Collapse Disorder (CCD).
CCD is possibly caused by a number of interacting factors
(disease, pests, insecticides etc.)
Faster, more accurate screening methods would
help reduce the risk of CCD spreading unchecked.
I will use the wing assay system to screen for
Deformed Wing Virus (DWV).
Background
Butterfly Experiment
Future work
Summary
Conclusion
To Summarise…
10μm
™Graphium weiskei butterfly wings can be used as highly sensitive, biocompatible
SERS substrates when coated with a thin film of gold.
™The excellent biocompatibility of the wings is unparalleled by other lithographically
produced substrates.
™This could pave the way for widespread application of ultrasensitive SERS-based
bioassays. I will demonstrate this by screening bees for DWV.
Background
Butterfly Experiment
Future work
Summary
Conclusion
In Conclusion…
10μm
Naturally inspired platforms for surface-enhanced spectroscopy have
the potential to revolutionise the way we screen for diseases! Watch
this space…
Thank you for your attention!
Acknowledgements:
Thanks to EPSRC for funding the project, the National Bee Unit for the
supply of deceased bees, and a big thank you to everyone in the School of
Physics who gave advice/support/butterflies/cake.