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Dr. Joseph Irudayaraj - Center for Food Safety Engineering - Purdue ...

Dr. Joseph Irudayaraj - Center for Food Safety Engineering - Purdue ...

11/24/2009 Surface

11/24/2009 Surface Enhanced Raman Spectroscopy using Silver Nanospheres SERS fingerprinting of bacteria using novel AgNSs a) b) A B a c) d) 1.6 1.4 a b In ntensity b c d e Int tensity c b a 1.2 1.0 f Absorbance 0.8 0.6 0.4 200 400 600 800 1000 1200 1400 1600 1800 2000 200 400 600 800 1000 1200 1400 1600 1800 2000 Raman Shift (cm -1 ) Raman Shift (cm -1 ) 0.2 0.0 300 400 500 600 700 800 900 Wavelength (nm) Wang and Irudayaraj. 2009. Ultrasensitive SERS fingerprinting and detection of bacteria using silver nanospheres. (In Review) A) SERS spectra of S. aureus on the as-prepared AgNSs with different concentrations from a, 10 6 ; b, 10 5 ; c, 10 4 ; d, 10 3 ; e, 10 2 and f, 10 cfu/mL; B) Comparation of SERS spectra of E. Coli O157:H7#5.2262 (a), S. Typhimurium (b), and S. aureus (c) at 785 nm excitation [10 2 cfu/ml] CVA for species and strain level differentiation Basic optical properties of nanoparticles The red axis represents that of spherical gold nanoparticles. The Localized Plasmon Resonance peak appears at about 520 – 530 nm. Au spheres Gold nanoparticles Au nanorods Gold nanorods The green axis represents rod shaped gold nanoparticles Has a transverse absorbance similar to Spherical particles and longitudinal absorbance (> 600 nm) depends on aspect ratio. Gold nanosensors detects multiple pathogens UV-Vis and Raman Spectroscopy integrated biosensors for multiple pathogen detection 13 nm 70 nm 55 nm 75 nm bacteria Sensing Method #1 Gold Nanoparticles Ag-Au Core-shell Nanoparticles (Tunable bands) 1. Dual Platform: UV-Visible & Raman spectroscopic techniques for detection 2. Dual Particle Probes: Gold nanoparticles & Ag-Au Core-Shell nanoparticles 3. Cross-Platform: Antibody/Aptamer for capturing specific pathogens 4. High Sensitivity: As few as 100 CFU/ml. 5. Rapid & Accurate: Assay takes less than 30 minutes. - Detection byUV-vis used Localized Surface Plasmon Resonance properties of gold nanoparticles: (i) absorption peak around 520 – 530 nm, (ii) peak red-shifts upon attachment of targets - Detection by Raman uses Raman labels Biofunctionalized probes to detect multiple pathogens Millex® Syringe Filter Unit Sensing Method #2 Micro-filtration to remove non-specific probes UV-Vis Measurements Raman Measurements Ravindranath et al. 2009. Multiplex detection methodologies and cross platform techniques in pathogen sensor development. (Manuscript in Preparation) --------------- POSTER 2

11/24/2009 Sensor 1: UV-Vis based Multiplex Detection Incorporating a separation step: Multifunctional nanoprobes for separation and detection 13 nm 70 nm 55 nm 75 nm 13 nm 70 nm 55 nm Gold Nanoparticles 75 nm Ag/Au Coreshell Nanoparticles 4- Biofunctionalized probes before and after interaction with pathogens Shift in the peak of biofunctionalized gold nanoparticles upon interaction with specific pathogens Multiple pathogens detection, separation and photothermal ablation Sensor 2: Raman based Multiplex Detection S. typhimurium E. coli O157:H7 S. aureus UV‐vis absorbance spectra after addition of a mixture of E. coli and S. typhimurium to anti‐ E. coli and S. typhimurium antibody‐conjugated amine modified gold nanorods of aspect ratios 2.0 and 3.2, respectively. The concentrations of E. coli and S. typhimurium were 1‐10 to 10 6 cfu/mL. L. monocytogenes Wang, C. and Irudayaraj, J. 2009. Multifunctional nanoprobes for separation, detection, and photothermal ablation of foodborne pathogens. Small. (In Press) Research Summary Phase I Sensor 1: Mid-IR Spectroscopic Biosensor • Fingerprints of pathogens using Raman and FTIR • Enhanced fingerprint using Silver spheres –LOD of 10 cfu/ml • Multiplex detection using LSPR properties of gold nanoparticles –LOD of 10 cfu/ml Irudayaraj and coworkers (2005, 2004) GOLD COATED SILICON WAFERS (10nM) • Multiplex detection with a separation step 3

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