SERS-based BiosensorsJames Krier, Lalitha Muthusubramaniam

Kevin Wang, Douglas Detert

Final PresentationEE235: Nanofabrication

May 12, 2009

Overview• Technology Landscape: Optical techniques for biosensing

• Surfaced-enhanced Raman scattering (SERS)

• Technical background

• SERS-based biosensors

• Financial and market considerations of SERS

Vast Technology Landscape

Diverse Applications

Total internal reflectance fluorescence (TIRF) biosensor

TIR Evanescent wave

http://www.microscopyu.com/articles/fluorescence/tirf/tirfintro.html

Typical TIRF Sensogram

http://www.tirftechnologies.com/principles.php

TIRF

Epifluorescence

AdvantagesHigh Signal to noise ratio (very little secondary emission from bulk solution)Highly robust, low cost, portableDrawbacksNeed for labelsHigh cross-reactivity (hence not easy to multiplex)

Molecularly Imprinted Polymers as Optical Sensors

Chemical Reviews, Chem. Rev.,100 2495 (2000)

Distribution of binding affinities in MIP vs. Ab

Schematic representation of molecular imprinting

3 methods to monitor binding in MIPs

Polymer International, Vol 56( (4), pp. 482-488

• Direct monitoring of analyte in solution; Incorporation of spectroscopically responsive monomers into the matrix;Competition assays using labeled ligands

Reflectometric interference spectroscopy (RIFS)

• The reflected beams superimpose and change optical thickness of the transducer by binding events onto the surface. Shift in characteristic interference spectrum is transformed into a signal curve.

J. Immunological Methods Vol 292, Issues 1-2, September 2004, pp.35-42

Reflectometric interference spectroscopy

(RIFS)Protein concentration determined spectrophotometrically and active antibody concentration determined by biosensor and ELISA for 9 sequentially eluted fractions.

J. Immunological Methods Vol 292, Issues 1-2, September 2004, pp.35-42

The SERS Solution

Adsorption Excitation Detection

Raman Spectroscopy

http://www.kamat.com/database/content/pen_ink_portraits/c_v_raman.htmAdapted from

http://upload.wikimedia.org/wikipedia/commons/8/87/Raman_energy_levels.jpg

C.V. Raman

Raman Spectroscopy

adenine

cytosine

guanine

thymine

uracil

• Selection rules

Based on symmetry elements of polarizability tensor

• Vibrational fingerprint

Comprised of narrow spectral features

• Robust mechanism

Not subject to photobleaching

• Weak Signal

Compared to Rayleigh scattering / fluorescence

Gelder, et al., J. Raman Spectrosc., 38 1133 (2007)A. Campion et al., Chem. Soc. Rev., 27 241 (1998)

Provides rich info. about structural data!

Surface-Enhanced Raman Scattering

1928 C.V. Raman discovers “Raman Effect” of inelastic scattering

1974 Discovery of enhanced Raman signals (105-106) from molecules adsorbed on roughed Ag surfaces.Mechanism is attributed to enhanced surface area for adsorption.

1977 Debate begins over the exact mechanism of signal enhancement.

M. Fleischmann, et al., Chem. Phys. Lett., 26 163 (1974)

D.L. Jeanmaire, R.P. Van Duyne, J. Electroanal. Chem., 84 1 (1977)

M.G. Albrecht, J. A. Creighton, J. Am. Chem. Soc., 99 15 (1977)

S. Schultz, et al., Surface Science, 104 419 (1981) M. Moskovits, , Reviews of Modern Physics, 57 3

(1985)K. Kneipp, et al., Chem. Rev., 99 2957 (1999)

SERS Enhancement

A.J. Haes, et al., Anal. Bioannal. Chem., 379 920 (2004) S. A. Maier, et al., Adv. Mater., 13 1501 (2001)

Tunable resonances: Shape- and Size-effects

• Chemical Enhancement

Based on metal-molecule charge-transfer effects

• Electromagnetic enhancement

Coupled to surface plasmon excitation of metal nanostructuresAway from plasmon

resonanceAt plasmon resonance

SERS Enhancement

10-250 nm

K. Kneipp, et al., Chem. Rev., 99 2957 (1999)J. Aizpurua, et al., Phys. Rev. Lett., 90 057401-1 (2003)

Enhancing SERS substrates• Plasmon resonance leads to local field

enhancement near the surface

Adsorbed molecules see increased field

• Raman signal enhancement (up to 1015)

Depends on local geometry of adsorption site

The SERS Advantage

S.M. Nie, et al., Science, 275 1102 (1997)http://www.oxonica.com/diagnostics/diagnostics_sers_imaging_applications.php

• Molecular fingerprinting

Unique vibrational spectra distinguishes molecules

• Tagless biosensing

Fluorescent dyes are not needed

• Multiplexed sensing

Plasmon resonances allow for sensor tunability

• In vivo applicability

Near-IR excitation and biocompatability allow

• Femtomolar and beyond

Single molecule spectroscopy is possible

1500 cm-1 1532cm-1

1600cm-1 1635cm-1

Single Molecule Detection

PRL 78, 1667 (1997)

TERS

nanowerk.com

TERS

Faraday Discuss., 132, 9 (2006)

TOPOGRAPHY + SPECTROSCOPY

PRL 100, 236101 (2008)

In-vivo glucose sensing

Faraday Discuss., 132, 9 (2006)

Other Options

PRL 62, 2535 (1989).

More Moerner et al.

Nature 402, 491 (2000).

stanford.edu/group/moerner/sms_movies.html

NSOM

JPC 100, 13103 (1996)

SERS Market

• Consumables

$50 to $750 per analysis

$1 million market annually

• Instrumentation

$10,000 - $180,000

Image source: http://senseable.mit.edu/nyte/visuals.html (New York Talk Exchange)Numbers: http://www.thefreelibrary.com/Market+profile:+SERS-a0137966471

SERS Companies• Bruker Optics

• D3 Technologies (Mesophotonics)

• Oxonica

• Renishaw

• Real Time Analyzers

http://www.brukeroptics.com/raman.html

SERS Vials

• Real Time Analyzers

• Sol-gel of Au or Ag nanoparticles

• 106 signal enhancement

www.rta.biz

Portable Raman

• Real Time Analyzers RamanID

• DeltaNu Inspector Raman

Diesel Fuel Spectrum

SPR Companies

• Biacore (GE)

• Biosensing Instrument

• FujiFilms

• GWC Technologies

• Ibis

• Sensiq

SPR Analyzer• Biosensing Instrument BI-

2000

• Cost: $39k

• Liquid/Gas Detection

• 10-4 degree sensitivity

Cost Comparison

Method Equipment Consumables

SERS

Spectrometer, $10kHe/Ne Laser,

$760Optics, $100Microflow Cell, $300Total = $11.1k

Au Nanoparticles ($3/mL)

TERS (AFM+ SERS)AFM ($90k - $150k)Total

= $111k - $161kAFM tips ($10)

SPR Full Setup, $39k - $60kAu Nanoparticles

($3/mL)

NSOMFull Setup, $100k -

$250kNSOM tip ($100)

Conclusion: SERS• Even simple (diatomic) molecules can have complex

and reproducible vibrational fingerprints

• The most practical option for sensing near the single-molecule level for a variety of analytes in solution or air, lending to an array of applications ranging from trace gas detection to automated protein identification

• Easy to couple with other supplementary techniques (e.g., AFM)

• Provides an economically feasible sensing mechanism for portable devices in atmospheric conditions