Alexandre François Jonathan Boehm Megan Penno Peter Hoffmann Tanya M. Monro

1. A novel optical-fiber based Surface Plasmon Resonance sensing architecture and its application to gastric cancer diagnostics Alexandre François Jonathan Boehm Megan Penno Peter Hoffmann Tanya M. Monro

2. Outline Outline New SPR fiber sensor architecture – Surface plasmon scattering SPR fiber sensor fabrication & characterization Application for cancer diagnostic

3. Traditional SPR systems – Kretschmann configuration Kretschmann prism configuration (angular interrogation) Reflectivity measured as function of incidence angle Sequence measurements require precise temperature control High quality sensor chip (gold coated quartz slides, high precision required for the gold coating) http://ultrabio.ed.kyushu-u.ac.jp/A9912/katudo/smelldog-e/SPR3-e.jpg

4. Alternative Optical fibers SPR systems Coupling between the incoming light and the plasmonic wave following the same mechanism as described by Krestchmann. Spectral interrogation rather than angular (broadband source for excitation) SPR characterisation performed by transmission/optical losses measurements Same restriction concerning the metallic coating Jorgenson, R. C., and Yee, S. S., “A fiber-optic chemical sensor based on surface plasmon resonance”, Sensors and Actuators B, 12, 213-220 (1993)

5. Novel optical fiber SPR systems Similar coupling mechanism between incoming light and surface plasmon wave as standard SPR optical fibers Point detection of the re-emitted light from the plasmonic wave by surface scattering at the sensing region Enables multiple sensing regions for both dynamic self referencing and multiplexed sensing Allow to perform both SPR and fluorescence sensing

6. Novel optical fiber SPR systems from concept to fabrication

7. SPR sensor fabrication Surface roughness = Key element for SPR scattering Silver deposited using modified Tollens reaction Silver nitrate solution (Transparent solution) Silver oxide (Brown precipitate) Reduction of silver ammonia to silver metal (1) 2 AgNO3 + 2 KOH → Ag2O (s) + 2 KNO3 + H2O Ag2O (s) + 4 NH3 + 2 KNO3 +H2O (l) → 2 Ag(NH3)2NO3 + 2 KOH CH2OH(CHOH)4CHO + 2Ag(NH3)2+ + 3OH–→ 2Ag(s) + CH2OH(CHOH)4CO2- + 4NH3 + H2O Silver ammonia complex (Transparent solution) • Simple Ag electroless plating process • Ag film thickness depends on temperature, reaction time, concentration of the reagents (2) (3) (1) (2) (3) Kretschmann, E., “The angular dependence and the polarisation of light emitted by surface plasmons resonance on metals due to roughness”, Optics Communications, 5, 331-336 (1972) Raether, H., “Surface plasmons on smooth and rough surfaces and on gratings”, Berlin, New York, Springer-Verlag (1988) Boehm, J., François, A., Ebendorff-Heidepriem, H., and Monro, T. M., “Chemical Deposition of Silver for the Fabrication of Surface Plasmon Microstructured Optical Fibre Sensor”, Plasmonics, 6, 133-136 (2011)

8. Silver deposition characterization Tollens reaction • Similar SPR response obtained from sputtered glass slide and Tollens coated glass slides. • Surface roughness ~ 5nm for a 60nm thick Ag film with Tollens reaction, ~ 2nm with sputtering. Sputtering reaction Boehm, J., François, A., Ebendorff-Heidepriem, H., and Monro, T. M., “Chemical Deposition of Silver for the Fabrication of Surface Plasmon Microstructured Optical Fibre Sensor”, Plasmonics, 6, 133-136 (2011)

9. Evanescent field capture mode vs transmission Transmission measurements Evanescent light measurements • Same information obtained from transmission & evanescent field measurements. • Higher Signal to Noise ratio in the evanescent field measurements François, A., Boehm, J., Oh, S. Y., Kok T. and Monro T. M., “Collection mode surface plasmon fibre sensors: A new biosensing platform”, Biosensors and Bioelectronics, 26, 3154-3159 (2011) White, I., M. and Fan, X., “On the performance quantification of resonant refractive index sensors”, Optics Express, 16, 1020-1028 (2008)

10. SPR signal as function of the silver coating thickness Transmission measurements Evanescent light measurements 22nm • No dependency of the SPR signal measured using the evanescent field mode as function of the thickness of the metallic coating • Ease the sensor fabrication & reduced cost 40nm Increasing silver coating thickness 55nm 65nm 132nm François, A., Boehm, J., Oh, S. Y., Kok T. and Monro T. M., “Collection mode surface plasmon fibre sensors: A new biosensing platform”, Biosensors and Bioelectronics, 26, 3154-3159 (2011)

11. Refractive index sensitivity Evanescent light measurements for 1.33<n<1,47 • Dl/Dn = 7.9×10-4 RIU for 1.33<n<1.47 • Comparable to previous published SPR fiber sensors (2.5×10-4 - 7.5×10-5 RIU) Jorgenson, R. C., and Yee, S. S., “A fiber-optic chemical sensor based on surface plasmon resonance”, Sensors and Actuators B, 12, 213-220 (1993)

12. Sensor performances • Reduction of the amplitude noise by 10dB • Reduction of the thermal noise by dynamic self referencing • Spectral noise remains constant • Higher resolution = lower detection limit • currently about 1.8×10-3 RIU for 1nm resolution of the SPR peak position (FWHM=50nm) • Sensitivity: 7.9×10-4 RIU • Detection limit (D) = Resolution (R)/ Sensitivity (S) • Resolution = • Amplitude noise contribution = • Thermal noise contribution = 0.002 RIU/◦C (reduced to 0 with self referencing) • Spectral noise = Resolution of the peak position, limited by the detection system and the FWHM (about 50nm) François, A., Boehm, J., Oh, S. Y., Kok T. and Monro T. M., “Collection mode surface plasmon fibre sensors: A new biosensing platform”, Biosensors and Bioelectronics, 26, 3154-3159 (2011) White, I., M. and Fan, X., “On the performance quantification of resonant refractive index sensors”, Optics Express, 16, 1020-1028 (2008) Rheims, J., Köser J. and Wriedt, T., “Refractive-index measurements in the near-IR using an Abbe refractometer”, Meas. Sci. Technol., 8, 601–605 (1997)

13. Application example: Cancer biomarker sensing • Cancer is one of the leading cause of mortality worldwide • Early cancer diagnostic may improve survival rate significantly and reduce the economic burden of long treatment • Cancer biomarker can be proteins with a large range of molecular weight. • The detection of a well know ovarian cancer marker (CA125) is shown as a proof of concept

14. Sensor preparation & Results PAH PSS PAH PSS PAH Silver 1st step Polyelectrolyte coating of silver SPR surface with poly(allylamine hydrochloride) and poly(sodium 4 styrenesulfonate) 2nd step Immobilization of antibody using amine coupling (NHS/EDC chemistry) 3rd step Blocking non-specific binding sites using a passivation agent 4th step Immobilization of CA125 (antigen)

15. Results Assuming a molecular weight of 150 kDa, 60 kDa and 120 kDa for the antibody, the BSA and the protein.

16. Conclusion future work • New SPR fibre sensor architecture based on surface scattering of plasmonic wave established • Easy to manufacture & low cost • Enables dynamic self referencing and higher SNR for lower detection limit • Proof of concept of protein sensing using SPR for cancer diagnostic Future work • Improving the sensor performance by specific fibre design (core Ø, dielectric function of the fiber & metallic coating • Assessment of the detection limit as function of the target’s molecular weight • Multiplexed detection of different biomarkers

17. Acknowledgments • This work was supported by the ARC, DSTO, the SA State Government and The University of Adelaide • Tanya Monro acknowledges the support of an ARC Federation Fellowship • The authors acknowledge Mr Roger Moore for the fibre fabrication and Mr Anthony Scoble for the sensor preparation