Optical Biosensing Technology based on Surface Plasmon Resonance

Transcription

1 Department of Electronic Engineering Optical Biosensing Technology based on Surface Plasmon Resonance Aaron H.P. Ho CIOEC 2011, 7-8 September 2011

2 Outline of Presentation!! Introduction: Plasmonics and Surface Plasmon Resonance (SPR)!! Topic 1: Phase-sensitive SPR Biosensors!! Topic 2: White-light Phase-sensitive SPR Biosensors!! Topic 3: Focusing of surface plasmon polaritons!! Topic 4: Lab-on-a-disc

3 Surface Plasmons in Metallic Nano-sized Objects Enhanced signal from target molecule EM Radiation LOCALIZED and ENORMOUS E-field on surface! Possibility of highly sensitive, fluorescence-free, real-time biosensing applications

4 Surface Plasmon in Metal Thin Films & Nano-structures Metal thin film Periodic structures Extremely strong & localized EM field (>10 6~7 E inc ) near surface Dielectric (D2) Metal (M) Dielectric (D1) "E(z)"

5 The Power of Plasmonics!! Light absorption and scattering: over fold higher than conventional fluorescent dyes!! No photobleaching!! Resonant plasmon wavelengths tunable from visible to NIR!! Color changes induced by surrounding molecules/environments!! Computational design of plasmonic structures! Ideal platform for viewing, detecting and manipulating biological molecules and components with light.

6 Recent Report on Plasmonic Biosensing NATURE Vol. 462, (26 November 2009) Plasmonics biosensing promises ultra-high sensitivity! Next step: Plasmonic Biochip Low-cost! plasmonic detection (30 atto M) # fluorescence detection (20 atto M) Expensive!

7 Topic 1: Phase-sensitive SPR Biosensors

8 Surface Plasmon Resonance Oscillation of electron density in metal surface with enhanced intensity SPP

9 Surface Plasmon Resonance Biosensing Real-time + label-free

10 a)! b)! Excitation of surface plasmon waves Total internal reflection TM-polarization c) k sp = k x 2$ k x = sin" i %! #! metal! k sp = k o! +! ) inc metal 1/ 2 glass sample sample & ' $ 1 ( metal( = sin 1 $ % n glass ( metal + ( sample sample #!! " (a) Otto configuration (b) Kretschmann configuration

11 SPR biosensor! Molecule binding occurs on the metal ==> shift of absorption dip!linear relationship between the amount of binding shift of SPR angle!spr also affects PHASE and SPECTRAL characteristics of the system Biomolecules" Reference channel" Sample channel" New Resonance Angle" Dip Angle (degree)

12 ! Angular SPR! Mostly single analyte systems! Proven technology, widely adopted by the market! Expensive, particularly Biacore systems (~US$150K) Important issues: Remarks Several companies started within the past 5 years. Commercialization opportunity already in existence! Cost, sensitivity, speed, assay simplicity in comparison to existing florescence or absorbance techniques

13 SPR Phase vs Angle/Intensity More sensitive SPR devices INTENSITY based: 1.7x 10-7 RIU (Spreeta) Conditions : Prism - BK7 glass Sample - water Metal layer - gold Thickness - 47nm Light source - HeNe Steep phase change PHASE based: 50 deg phase jump for %n = RIU, assuming 0.01 o phase resolution! sensitivity factor 8 x10-8 RIU Phase Vs RIU Phase Vs Angle Conditions : Prism - BK7 glass Metal layer - gold Thickness - 45nm Light source - HeNe Incident angle - 75 $ A. V. Kabashin and P. I. Nikitin, Opt. Comm. 150 (1998), 5-8 H.P. Ho et al, Rev. Sci. Instru. 73 (2002),

14 Differential phase surface plasmon resonance biosensor S.Y. Wu, H.P. Ho et al., Optics Letters, 29(2004),

15 Differential phase SPR set-up

16 Phase Shift vs Refractive Index Glycerin Concentration (% by weight) with respect to water 5.48 x 10-8 RIU (0.01 o resolution)

17 DNA-DNA Interaction Normalized phase change (degree) Probe 1 Buffer Probe 2 Buffer Digoxigenin (DIG) Synthetic Probe 2 Synthetic Probe 1 PolyA linker to avoid overcrowding Target DNA Biotin Avidin Buffer Probe Time (second) Hybridization Human Herpes Virus DNA (Target DNA) SPR surface ~4 o phase change Buffer

18 Michelson vs Mach-Zehnder Michelson Interferometer BSA (Bovine Serum Albumin) - anti-bsa Ab binding Michelson (double-pass) Mach-Zehnder X2 phase change Mach-Zehnder (single-pass) H.P Ho et al, IEEE Sensors Journal, 7(2007), 70-73

19 Multi-pass (Fabry-Perot) Interferometer Net output =! " n=1 R ( n) #( n) Mode (1): (transmission) Mode (2): (reflection) 3 2 R (2n 1) (2n 1) p! p p! =# " $ $ # + # p + = % p $! p n= 1 r..exp[ i ] r.. R.exp[ i3 ]... r R exp[ i(2n 1) ] R =# " (2 n) (2 n) p #! p + p #! p + = $ p! p n= 1 r.. R.exp[ i2 ] r.. R.exp[ i4 ]... r R exp[ i(2 n) ] rp n n! p r p! p R! R n relative amplitude net SPR phase change when the beam has undergone n th pass amplitude reflection coefficient of the sensor surface for p polarization phase change induced by dielectric amplitude reflectivity coefficient of Beam Splitter amplitude transmission coefficient of Beam splitter

20 Experimental Results from Protein-DNA Binding Comparison between single, double and multi-pass configurations Multi-pass: %&=17.6deg, 7.8ng/ml, 2.26 times improvement Double pass: %&=15.7deg, 8.8ng/ml, 2 times improvement Single pass: %&=7.8deg, 17.7ng/ml Cytochrome: 34kD Aptamer: 23kD, 600nM H.P. Ho et al, Optics Communications, 276(2007),

21 Single-beam SPR phase interferometer based on liquid crystal modulator (LCM) Phase stepping done by LCM Sensitivity limit: 1.9 x 10-8 RIU U.S. patent pending

22 Experimental resolution Phase shift of 32 => RI change of 6 x 10-5 RIU (0%->0.05%) Sensitivity limit: 1.9 x 10-8 RIU based on 0.01 resolution

23 Achieving WIDE DYNAMIC RANGE : LSPR + capture both angular/spectral and phase data U.S. patent pending

24 Simulated results: Phase change at different incident angles versus a wide range of refractive indices Incident angle ( )! RI range: RIU! Incident angle range: ! 18 detector elements are used over the range

25 pspr prototype

26 pspr prototype

27 pspr prototype

28 Response curve of pspr prototype Sensitivity limit: 10E -8 RIU Measurement range: 3.5% RIU Wt. % of glycerol and water mixture 4% 3% 2% 5% 6% 7% 8% 1% water

29 2-D SPR Sensor Array In-flow Out-flow Illumination CCD imaging

30 SPR Biosensor Imaging Results (a) 9-element SPR biosensor array for detection BSA antigenantibody binding reaction with various concentrations and EDC/NHS ratios Experiment 1 BSA/anti-BSA detection C. L. Wong, H.P. Ho et al, Biosensors and Bioelectronics, 24(2008), (b) Real-time SPR phase measurement showing gradual increase of SPR phase caused by binding reaction, larger phase change with higher concentration of BSA antigen (c) Effect of using various EDC/NHS ratio showing that a ratio of at least 1:10 should be used in order to obtain reliable results

31 Protein array (0.02 ( mg/ml) mg/ml) Tumor antigen (0 mg/ml) (1 mg/ml) Control BSA antigen Control

32 Topic 2: White-light Phasesensitive SPR biosensor

33 Review SPR Sensing Schemes! Angle shift commercial systems (Biacore, SPREETA )! Intensity change at fixed angle easy to setup particularly for imaging SPR, highly non-linear response! Spectral shift simple instrumentation, WIDE DYNAMIC RANGE, but LOW RESOLUTION! Phase change very high sensitivity, but limited dynamic range! NO PERFECT SOLUTION YET! 33

34 Combining phase and spectral SPR!! Overcome RESOLUTION and DYNAMIC RANGE problems Use white light (poly-chromatic) source in a Michelson interferometer 40W White LED source Dispersion compensation reference prism U.S. patent pending Ho et al, Optics Letters (submitted), Biosensors & Bioelectronics (submitted)

35 White-light phase-sensitive SPR system

36 Fringe formation in spectral domain! Effectively we are operating a large number of interferometers at different wavelengths simultaneously! Spectral fringes of p- and s-polarization with distilled water as sample

37 Differential Phase versus Wavelength

38 Phase change versus analyte concentration! Sharpe phase change across SPR observed for entire range of concentration Sensitivity limit: 2 ' 10-7 RIU Possibly no limit on dynamic range as long as SPR dip happens within the range of spectrometer

39 Biosensing of BSA protein binding!! Sensitivity limit: 0.5 ng ml -1 Dynamic range: No observable saturation up to 20 ng ml -1 Maximum SPR phase shift occurs at 632nm

40 Summary of Topics!! Introduction: Plasmonics and Surface Plasmon Resonance (SPR)!! Topic 1: Phase-sensitive SPR Biosensors!! Topic 2: White-light Phase-sensitive SPR Biosensors

41 Acknowledgement & Collaborators Funding support: Research Grants Council, Innovation & Technology Commission, Research studentship, CUHK Research students: W. Yuan, T. Yang, Q.L. Chen, T.T. Yu, H.X. Zhang Center for Photonics, Lasers and Biophotonics, State University of New York at Buffalo: P.N. Prasad, W.C. Law, K.T. Yong CityU: S.P.Ng, Lawrence C.M. Wu EEE Department, Nangyang Technological University, Singapore: Chinlon Lin, C.L. Wong, P. Shum Department of Biochemistry, CUHK: S.K. Kong School of Medical Sciences, CUHK: Y.W. Kwan Faculty of Medicine, CUHK: Margaret Ng, Patrick Kwan, John Leung, Paul Cheung, Philip Chiu Department of Physics, CUHK: Daniel H.C. Ong, J.F. Wang Department of Chemistry, CUHK: Ken Leung