OSA's Digital Library

Virtual Journal for Biomedical Optics

Virtual Journal for Biomedical Optics

| EXPLORING THE INTERFACE OF LIGHT AND BIOMEDICINE

  • Editor: Gregory W. Faris
  • Vol. 2, Iss. 5 — May. 17, 2007
« Show journal navigation

Highly sensitive spectroscopic detection of heme-protein submonolayer films by channel integrated optical waveguide

Ismail Emre Araci, Sergio B. Mendes, Nasuhi Yurt, Seppo Honkanen, and N. Peyghambarian  »View Author Affiliations


Optics Express, Vol. 15, Issue 9, pp. 5595-5603 (2007)
http://dx.doi.org/10.1364/OE.15.005595


View Full Text Article

Acrobat PDF (246 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

A highly sensitive technique based on optical absorption using a single-mode, channel integrated optical waveguide is described for broad spectral band detection and analysis of heme-containing protein films at a glass/water interface. Fabrication steps and device characteristics of optical waveguides suitable for operation in the wavelength range of 400 – 650 nm are described. Experimental results reported here show a limit of detection smaller than 100 pg/cm2 for a submonolayer of ferricytochrome c by probing the Soret transition band with a 406-nm semiconductor diode laser propagating in a single-mode, ion-exchanged channel waveguide. By taking advantage of the exceptionally low limit of detection, we examined the adsorption isotherm of cytochrome c on a glass surface with unprecedented detail. Unlike other surface-specific techniques (e.g. SPR, integrated optic Mach-Zehnder interferometer) that probe local refractive-index changes and therefore are very susceptible to temperature fluctuations, the integrated optical waveguide absorption technique probes molecular-specific transition bands and is expected to be less vulnerable to environmental perturbations.

© 2007 Optical Society of America

1. Introduction

Binding characteristics of proteins at various interfaces are critical for a wide range of biotechnological fields and play a key role in the development/screening of novel pharmaceutical drugs [1

1. J. D. Swalen, D. L. Allara, J. D. Andrade, E. A. Chandross, S. Garoff, J. Israelachvili, T. J. McCarthy, R. Murray, R. F. Pease, J. F. Rabolt, K. J. Wynne, and H. Yu, “Molecular Monolayers and Films,” Langmuir 3, 932–950 (1987). [CrossRef]

]. Over the past decade, highly sensitive optical techniques for investigating biological films has been widely used for real-time monitoring of molecular interactions at bio-interfaces; most prevalent among these techniques has been surface plasmon resonance (SPR) [2–4

2. J. Homola, S. S. Yee, and G. Gauglitz, “Surface plasmon resonance sensors: review,” Sens. Actuators B 54, 3–15, (1999). [CrossRef]

]. In the SPR technique, molecular adsorption at the probing interface creates a local change in the refractive index inside the evanescent-field region of the plasmon mode that translates into a shift of the resonant angle. An angular shift of approximately 1×10-4 of a degree corresponds typically to the adsorption of a protein film of approximately 100 pg/cm2 [3

3. W. D. Wilson, “Analyzing biomolecular interactions,” Science 295, 2103–2105, (2002). [CrossRef] [PubMed]

, 4]. Besides the high angular resolution needed by the SPR technique, an exceptional temperature/mechanical control is also required to prevent refractive-index perturbations from the bulk phase into the surface plasmon mode.

Transduction in protein films by broadband or multi-wavelength optical absorption using planar integrated optical waveguides can potentially simplify analyte detection and identification, due to its spectral specificity and robustness against environmental changes. A chromophore located within the evanescent region interacts with the guided electromagnetic radiation and thus attenuates its optical intensity; such an approach using planar slab single-mode waveguides have been used for investigations of physical/chemical properties of surface-adsorbed proteins in the middle of the visible spectral region [5

5. A. F. Runge, N. C. Rasmussen, S. S. Saavedra, and S. B. Mendes, “Determination of anisotropic optical constants and surface coverage of molecular films using polarized visible ATR spectroscopy. Application to adsorbed cytochrome c films,” J. Phys. Chem. B 109, 424–431 (2005). [CrossRef]

, 6

6. S. B. Mendes, L. F. Li, J. J. Burke, J. E. Lee, D. R. Dunphy, and S. S. Saavedra, “Broad-band attenuated total reflection spectroscopy of a hydrated protein film on a single mode planar waveguide,” Langmuir 12, 3374–3376 (1996). [CrossRef]

]. However, to take full advantage of the higher extinction coefficient at the Soret band in heme-proteins and reach a limit of detection (LOD) at least comparable or superior to SPR, single-mode channel waveguides operating in the 400-nm range with low loss are needed. In that perspective, a slab waveguide spectrometer that transmitted light down to 400 nm was demonstrated previously [7

7. J. T. Bradshaw, S. B. Mendes, and S. S. Saavedra, “A Simplified Broadband Coupling Approach Applied to Chemically Robust Sol-Gel, Planar Integrated Optical Waveguides,” Anal. Chem.. 74, 1751–1759 (2002). [CrossRef] [PubMed]

]. However, light intensity in the 400-nm region was only marginal, and thus stray light and low signal-to-noise ratio (SNR) were crucial factors that hampered the limit of detection in that work. In addition, there has been great interest in using the Soret transition band as a sensing probe for both protein and chemical measurements as described in many works such as polymer-film based fluoride sensor [8

8. I. H. A. Badr and M. E. Meyerhoff, “Fluoride-selective optical sensor based on Aluminum (III)-octaethylporphyrin in thin polymeric film: further characterization & practical application,” Anal. Chem. 77, 6719–6728 (2005). [CrossRef] [PubMed]

], glass-slide optical waveguide acidity sensor [9

9. T. Umemura, H. Hotta, T. Abe, Y. Takahashi, H. Takiguchi, M. Uehara, T. Odake, and K. Tsunoda, “Slab optical waveguide high-acidity sensor based on an absorbance change of protoporphyrin IX,” Anal. Chem. 78, 7511–7516 (2006). [CrossRef] [PubMed]

], gas phase HCl sensor based on sol-gel film [10

10. Y. Itagaki, K. Deki, S. I. Nakashima, and Y. Sadaoka, “Development of porphyrin dispersed sol-gel films as HCl sensitive optochemical gas sensor,” Sens. Actuators B 117, 302–307 (2006). [CrossRef]

], and detection of protein adsorption by attenuated total reflection [11

11. Y. Y. Cheng, S. H. Lin, H. C. Chang, and M. C. Su, “Probing adsorption, orientation and conformational changes of cytochrome c on fused silica surfaces with the soret band,” J. Phys. Chem. A 107, 10687–10694 (2003) [CrossRef]

].

By using a silver-film ion-exchange process, we developed here highly confined, single-mode, integrated optical waveguides that exhibit sufficiently low propagation loss in the short wavelength range and provide high detection sensitivity; in addition this work employs channel waveguides which is a superior configuration to interface the probing device with fiber coupled sources and detectors when compared to slab waveguides. These glass waveguides, which provide low optical losses and are fairly inexpensive, can potentially enable the fabrication of miniature disposable integrated optical biosensors. To demonstrate the strong optical response and much improved LOD in our waveguides, a submonolayer film of the protein ferricytochrome c (cyt c) was utilized. Due to the superior SNR in our setup, the adsorption isotherm of cyt-c molecules on a glass/aqueous interface was examined with unprecedented detail, and LOD results were determined from the measured SNR and absorbance values.

2. Preliminary considerations

It is well known that attenuation of guided modes due to the presence of chromophores in the evanescent region strongly depends on the waveguide geometry and that a single-mode configuration provides the maximum sensitivity. The evanescent field absorption in optical waveguides follows a pseudo Lambert-Beer relationship and, for chromophores bound to the waveguide surface, the absorbance A is given by [12

12. S. B. Mendes and S. S. Saavedra, “Comparative Analysis of Absorbance Calculations for Integrated Optical Waveguide Configurations by use of the Ray Optics Model and the Electromagnetic Wave Theory,” Appl. Opt. 39, 612–621 (2000). [CrossRef]

]:

A=(εΓl)×κh
(1)

where ϵ is the molecular extinction coefficient, Γ is the molecular surface density (surface coverage), l is the optical interaction length, k is the fraction of the normalized waveguide mode profile occupied by the adsorbed molecular film, and h is the thickness of the adsorbed film. Fig. 1(a) shows the schematic of the absorption-based sensing with a single-mode planar optical waveguide.

Glass integrated optic represents a viable approach for the development of inexpensive and robust passive biosensor devices. Binary ion-exchange, in turn, is one of the most widespread technologies for the fabrication of optical waveguides in glass substrates. Ag+-Na+ ion-exchange glass waveguides have been used for fabrication of passive optical devices for telecommunication applications in the 1.3–1.5 μm region exhibiting low propagation loss and fiber-to-waveguide coupling loss [13

13. A. Tervonen, P. Poyhonen, S. Honkanen, M. Tahkokorpi, and S. Tammela, “Examination Of 2-Step Fabrication Methods For Single-Mode Fiber Compatible Ion-Exchanged Glass Wave-Guides,” Appl. Opt. 30, 338–343 (1991). [CrossRef] [PubMed]

]. However, low-cost fabrication of single-mode waveguides at wavelengths lower than 450 nm has been a challenge due to increased waveguide losses and smaller dimensions required at lower wavelengths. Another challenge to efficiently take advantage of ion-exchange waveguides for optical sensing has been the need of a high contrast refractive-index profile for increased mode confinement and thus higher sensitivity [14

14. W. Lukosz, “Integrated Optical Chemical and Direct Biochemical Sensors,” Sens. Actuators B 29, 37–50 (1995). [CrossRef]

]. Based on these considerations, we have chosen a silver film technique for fabrication of the ion-exchanged waveguides [15

15. S. Honkanen, “Silver-Film Iob-Exchange Technique,” in Introduction to Glass Integrated Optics, S. I. Najafi, ed., (Artech House, Boston-London, 1992).

, 16

16. R. W. Chuang and C. C. Lee, “Low-loss deep glass waveguides produced with dry silver electromigration process,” J. Lightwave Technol. 20, 1590–1597 (2002). [CrossRef]

].

Fig. 1. (a). The schematic of the waveguide sensing platform. The fundamental mode of Ag ion exchange waveguide interacts with the surface adsorbed cyt c molecules for a pathlength of l = 1.6 cm. Interaction strength, k, is determined by h and evanescent tail of the mode as shown. (b) Near field images of the waveguide output. Only the fundamental mode was excited at 532 nm. Superposition of two lateral modes can be seen for 406 nm.

The cyt c protein was used as a biomolecular film in our model tests [5

5. A. F. Runge, N. C. Rasmussen, S. S. Saavedra, and S. B. Mendes, “Determination of anisotropic optical constants and surface coverage of molecular films using polarized visible ATR spectroscopy. Application to adsorbed cytochrome c films,” J. Phys. Chem. B 109, 424–431 (2005). [CrossRef]

, 6

6. S. B. Mendes, L. F. Li, J. J. Burke, J. E. Lee, D. R. Dunphy, and S. S. Saavedra, “Broad-band attenuated total reflection spectroscopy of a hydrated protein film on a single mode planar waveguide,” Langmuir 12, 3374–3376 (1996). [CrossRef]

, 11

11. Y. Y. Cheng, S. H. Lin, H. C. Chang, and M. C. Su, “Probing adsorption, orientation and conformational changes of cytochrome c on fused silica surfaces with the soret band,” J. Phys. Chem. A 107, 10687–10694 (2003) [CrossRef]

, 17

17. R. A. Scott and A. G. Mauk, in Cytochrome c: A Multidisciplinary Approach, (University Science Books, Sausalito, CA, 1996).

, 18

18. E. Margoliash and N. Frohwirt, “Spectrum of Horse-Heart cytochrome c,” Biochem. J. 71, 570–572 (1959).

]. Cyt c is a small stable protein that can reversibly withstand rather extreme conditions and has been used in several studies of protein mechanisms [17

17. R. A. Scott and A. G. Mauk, in Cytochrome c: A Multidisciplinary Approach, (University Science Books, Sausalito, CA, 1996).

]. The prosthetic heme group in cyt c is a useful spectroscopic probe as it strongly absorbs in the UV and visible regions. As previously reported [18

18. E. Margoliash and N. Frohwirt, “Spectrum of Horse-Heart cytochrome c,” Biochem. J. 71, 570–572 (1959).

], oxidized cyt c has a strong optical absorption at the Soret band centered at 410 nm, and a weaker and broader absorption band located at 528 nm. The detection enhancements that were made possible by improvements on the fabricated waveguides were demonstrated by utilizing two different wavelengths (406 nm and 532 nm) to probe the binding of cyt c molecules to the glass waveguide surface, while a 633-nm wavelength which is outside the protein transition bands was used to monitor device stability. Waveguide sensitivity is strongly dependent on polarization when the film thicknesses are close to the waveguide cutoff range [14

14. W. Lukosz, “Integrated Optical Chemical and Direct Biochemical Sensors,” Sens. Actuators B 29, 37–50 (1995). [CrossRef]

]. However, we operated significantly away from cut-off conditions for both polarizations and modeling results indicated that the effects of polarization were not significant in our case.

3. Waveguide fabrication and characterization

4. Surface preparation.

5. Results and discussion

5.1 Simulation results

We have used an in-house software for calculation of mode intensity overlap and waveguide optical response [13

13. A. Tervonen, P. Poyhonen, S. Honkanen, M. Tahkokorpi, and S. Tammela, “Examination Of 2-Step Fabrication Methods For Single-Mode Fiber Compatible Ion-Exchanged Glass Wave-Guides,” Appl. Opt. 30, 338–343 (1991). [CrossRef] [PubMed]

]. The simulations were realized for TE polarized light with a cladding index of nclad = 1.33 (for a typical aqueous solution) and the perturbation of the adsorbed film on the mode shape was assumed negligible [12

12. S. B. Mendes and S. S. Saavedra, “Comparative Analysis of Absorbance Calculations for Integrated Optical Waveguide Configurations by use of the Ray Optics Model and the Electromagnetic Wave Theory,” Appl. Opt. 39, 612–621 (2000). [CrossRef]

]. For the given fabrication parameters, we have considered Δnmax = nsubs - nsurface = 0.05 in our modeling [21

21. S. Honkanen and A. Tervonen, “Experimental-analysis Of Ag+-Na+ Exchange in Glass with Ag Film Ion Sources for Planar Optical Wave-Guide Fabrication,” J. Appl. Physics 63, 634–639 (1988). [CrossRef]

]. Figure 2 shows the silver ion concentration and the fundamental mode field intensity profile at 406 nm for the fabrication parameters given in waveguide fabrication section.

Fig. 2. The silver ion concentration and fundamental mode intensity profile (the solid contour lines are for normalized concentrations of 0.3 0.6 and 0.9 and colors from blue to yellow are for increasing intensity).

At the 532-nm and 633-nm wavelengths, the numerical calculations showed a single-mode operation for both the vertical and lateral confinements, while at 406 nm the structure supports a single-mode structure in the vertical direction and two modes in the lateral direction. In addition, our simulations showed negligible difference in the optical response of different lateral modes at the wavelengths of interest. The step-index profile is clearly seen for ion concentrations shown in Fig. 2 and the effective thickness of the waveguide is less than 1μm. Intensity profile in Fig. 2 is in visual agreement with experimental data shown in Fig. 1(b). The fraction of the normalized fundamental waveguide mode in the cladding was calculated for 406 nm and found to be 0.63%, and the fraction of this mode overlapping with an adsorbed molecular film of thickness h = 3 nm (typical size of cyt c), k was calculated to be 0.032%. This overlap can be directly translated into device response by using the absorbance equation given as Eq. (1). The extinction coefficient of oxidized cyt c is ϵ = 95 ×103 and 11×103 [M×cm]-1 at 406 and 532 nm, respectively [18

18. E. Margoliash and N. Frohwirt, “Spectrum of Horse-Heart cytochrome c,” Biochem. J. 71, 570–572 (1959).

]. The resulting absorbance values are A = 2.25 and 0.29 at 406 and 532 nm, respectively for an interaction length of l = 1.6 cm and for a saturated surface concentration of Γ= 140 ng/cm2.

5.2 Experimental results

Fig. 3. Experimental data showing the response of the sensor to about one half of a monolayer of cyt c. The inset shows the normalized sensor response (A/(ϵ k)) with respect to the probing path length at 406 nm (dashed line) and at 532 nm (solid line). The SNR is measured to be ~1500 for 406 nm laser source.

The inset in Fig. 3 shows the normalized sensor response with respect to pathlength for the two wavelengths (406 and 532 nm). The normalized sensor response is defined as A/(ϵ k). The lines are the best linear fits to the experimental data points. The normalized response is very similar at the two wavelengths and there is no significant deviation from a linear dependence as the pathlength increases, thus indicating that stray light did not degrade the measurements and spectroscopic response was achieved as expected.

To investigate the adsorption isotherm of cyt c onto the glass waveguide surface we prepared solutions with different concentrations and measured the optical absorbance near the Soret band (406 nm). Figure 4 shows the adsorption isotherm of cyt c onto the glass waveguide surface from phosphate buffer solutions at pH-7. The x-axis shows the bulk concentration of cyt c in the sensing region, and y-axis shows the optical absorbance on the left and the corresponding surface concentration on the right. After injection of cyt c we waited for 10 minutes for stabilization before taking these measurements. The experiment was repeated three times to measure the optical absorbance and determine the surface concentration for a given volume concentration. Between each measurement, the probing surface was prepared as described in the surface preparation section to provide exactly the same physical/chemical environment. However, it is well-known that the physical/chemical environment near the surface (i.e. temperature, pH) can affect the temporal behavior of the adsorption process, the final amount of surface-adsorbed molecules, and also the Soret absorption band for cyt c molecules [11

11. Y. Y. Cheng, S. H. Lin, H. C. Chang, and M. C. Su, “Probing adsorption, orientation and conformational changes of cytochrome c on fused silica surfaces with the soret band,” J. Phys. Chem. A 107, 10687–10694 (2003) [CrossRef]

, 22

22. M. Leone, A. Cupane, V. Militello, and L. Cordone, “Thermal broadening of the Soret band in heme complexes and in heme proteins: role of the iron dynamics,” Eur. Biophys. J. 23, 349–352 (1994). [CrossRef] [PubMed]

]. The variability on the final concentration of surface-adsorbed molecules was quantified by the error bars in Fig. 4. These error bars are the standard deviation of three independent measurements and they quantify our ability (or lack of) to reproduce the same surface concentration of adsorbed molecules with identical optical properties; it is a consequence of the variations on the surface environment.

Fig. 4. Adsorption isotherm of cyt c on the glass surface at pH-7, measured at 406 nm. The dashed curve is the best fit of the experimental data to a Langmuir adsorption model with Ka = 2.4 × 106 M-1. The error bars are showing the surface concentration variance of independent three measurements.

As shown in Fig. 4, the surface coverage gradually levels off as the bulk concentration increases above 3 μM. The dashed line is the best fit of the experimental data to a Langmuir adsorption isotherm

Θ=KaCb1+KaCb
(2)

where Θ is the ratio of the number of occupied adsorption sites to the total number of sites at saturation and Ka is the adsorption equilibrium constant. This constant is strongly dependent on the surface chemistry of the substrate [11

11. Y. Y. Cheng, S. H. Lin, H. C. Chang, and M. C. Su, “Probing adsorption, orientation and conformational changes of cytochrome c on fused silica surfaces with the soret band,” J. Phys. Chem. A 107, 10687–10694 (2003) [CrossRef]

]. The observation of a saturation regime as in Fig. 4 is another indication that the detected signals originated from surface-bound proteins rather than free protein molecules dissolved in the aqueous solution [11

11. Y. Y. Cheng, S. H. Lin, H. C. Chang, and M. C. Su, “Probing adsorption, orientation and conformational changes of cytochrome c on fused silica surfaces with the soret band,” J. Phys. Chem. A 107, 10687–10694 (2003) [CrossRef]

]. The equilibrium constant for Corning 0211 glass surface was found to be Ka = 2.4 × 106 M-1 and this value is almost equal to the equilibrium constant, Ka = 2.5 × 106 M-1, that was determined by using the cyt c adsorption data given in Table 1 of Ref. [23

23. A. F. Runge and S. S. Saavedra, “Comparison of microcontact-printed and solution-adsorbed cytochrome c films on indium tin oxide electrodes,” Langmuir 19, 9418–9424 (2003). [CrossRef]

] for indium tin oxide surfaces.

Fig. 5. Response of the sensor to 1 nM of cyt c solution. This corresponds to about 270 pg/cm2 surface coverage. The signal change is Io - If ≈ 0.01, which in absorbance units corresponds to A = -log (0.99) ≈ 4×10-3, well above than the ALoD = 8.69×10-4.

Figure 5 shows the normalized device response to 1 nM of cyt c solution at 406 nm. The calculated root-mean square (RMS) noise value from the figure is σ ≈ 6.7×10-4, in the time scale of one minute. The SNR of our measurements was calculated to be (Io/ σ) = 1.5×103, where Io is the time average of the normalized waveguide output before cyt c is introduced to the surface. The LOD can be calculated from the RMS noise value by using the standard assumption in analytical measurements that one can detect changes that are three times larger than the noise level (3σ = 2 × 10-3, in our case). In absorbance units a change of 3σ corresponds to ALOd = -log (ILod / I0) = -log (1–3σ) = 8.69×10-4. This value is an order of magnitude better compared to previously reported values [7

7. J. T. Bradshaw, S. B. Mendes, and S. S. Saavedra, “A Simplified Broadband Coupling Approach Applied to Chemically Robust Sol-Gel, Planar Integrated Optical Waveguides,” Anal. Chem.. 74, 1751–1759 (2002). [CrossRef] [PubMed]

]. When we consider that a surface coverage of 140 ng/cm2 causes an optical absorbance of 2.1 as determined in Figs. 3 and 4, our detection limit can be calculated to be about 59 pg/cm2. This LOD is below the range typically quoted for state-of-the-art SPR equipment and besides that these SPR data can only be obtained through extremely high experimental precision and environmental control. In Fig. 5, the 1 nM of cyt c solution causes an absorbance of about A = -log (If/Io) = 4×10-3, which corresponds to a protein surface coverage of 270 pg/cm2.

6. Conclusion

In conclusion, we have presented a simple and robust integrated optic sensing platform based on silver film ion-exchange waveguides; those waveguides exhibit high sensitivity and sufficiently low losses to operate in the single-mode regime in the wavelength range of 400–650 nm. By taking advantage of the extremely high extinction coefficient at the Soret band present in heme proteins, we probed surface adsorption of protein films at glass/water interfaces. We presented the adsorption isotherm of oxidized cyt c protein films on the waveguide borosilicate glass surface and reported a value smaller than 100 pg/cm2 for the limit of detection. The highly sensitive and spectroscopic selective detection of protein films described here can potentially become an important bioanalytical tool for monitoring protein binding at several biomimetic surfaces in technologies such as high-throughput screening of novel pharmaceutical drugs and immuno-assay biosensors.

Acknowledgments

The authors would like to acknowledge support from National Science Foundation grant numbers DMR-0099862 (to NP) and DBI 0352449 (to SBM), and also the state of Arizona TRIF program.

References and links

1.

J. D. Swalen, D. L. Allara, J. D. Andrade, E. A. Chandross, S. Garoff, J. Israelachvili, T. J. McCarthy, R. Murray, R. F. Pease, J. F. Rabolt, K. J. Wynne, and H. Yu, “Molecular Monolayers and Films,” Langmuir 3, 932–950 (1987). [CrossRef]

2.

J. Homola, S. S. Yee, and G. Gauglitz, “Surface plasmon resonance sensors: review,” Sens. Actuators B 54, 3–15, (1999). [CrossRef]

3.

W. D. Wilson, “Analyzing biomolecular interactions,” Science 295, 2103–2105, (2002). [CrossRef] [PubMed]

4.

Biocore Product Brochure, “Biacore 3000,” (2007). http://www.biacore.com/lifesciences/products/systems_overview/3000/system_information/index.html

5.

A. F. Runge, N. C. Rasmussen, S. S. Saavedra, and S. B. Mendes, “Determination of anisotropic optical constants and surface coverage of molecular films using polarized visible ATR spectroscopy. Application to adsorbed cytochrome c films,” J. Phys. Chem. B 109, 424–431 (2005). [CrossRef]

6.

S. B. Mendes, L. F. Li, J. J. Burke, J. E. Lee, D. R. Dunphy, and S. S. Saavedra, “Broad-band attenuated total reflection spectroscopy of a hydrated protein film on a single mode planar waveguide,” Langmuir 12, 3374–3376 (1996). [CrossRef]

7.

J. T. Bradshaw, S. B. Mendes, and S. S. Saavedra, “A Simplified Broadband Coupling Approach Applied to Chemically Robust Sol-Gel, Planar Integrated Optical Waveguides,” Anal. Chem.. 74, 1751–1759 (2002). [CrossRef] [PubMed]

8.

I. H. A. Badr and M. E. Meyerhoff, “Fluoride-selective optical sensor based on Aluminum (III)-octaethylporphyrin in thin polymeric film: further characterization & practical application,” Anal. Chem. 77, 6719–6728 (2005). [CrossRef] [PubMed]

9.

T. Umemura, H. Hotta, T. Abe, Y. Takahashi, H. Takiguchi, M. Uehara, T. Odake, and K. Tsunoda, “Slab optical waveguide high-acidity sensor based on an absorbance change of protoporphyrin IX,” Anal. Chem. 78, 7511–7516 (2006). [CrossRef] [PubMed]

10.

Y. Itagaki, K. Deki, S. I. Nakashima, and Y. Sadaoka, “Development of porphyrin dispersed sol-gel films as HCl sensitive optochemical gas sensor,” Sens. Actuators B 117, 302–307 (2006). [CrossRef]

11.

Y. Y. Cheng, S. H. Lin, H. C. Chang, and M. C. Su, “Probing adsorption, orientation and conformational changes of cytochrome c on fused silica surfaces with the soret band,” J. Phys. Chem. A 107, 10687–10694 (2003) [CrossRef]

12.

S. B. Mendes and S. S. Saavedra, “Comparative Analysis of Absorbance Calculations for Integrated Optical Waveguide Configurations by use of the Ray Optics Model and the Electromagnetic Wave Theory,” Appl. Opt. 39, 612–621 (2000). [CrossRef]

13.

A. Tervonen, P. Poyhonen, S. Honkanen, M. Tahkokorpi, and S. Tammela, “Examination Of 2-Step Fabrication Methods For Single-Mode Fiber Compatible Ion-Exchanged Glass Wave-Guides,” Appl. Opt. 30, 338–343 (1991). [CrossRef] [PubMed]

14.

W. Lukosz, “Integrated Optical Chemical and Direct Biochemical Sensors,” Sens. Actuators B 29, 37–50 (1995). [CrossRef]

15.

S. Honkanen, “Silver-Film Iob-Exchange Technique,” in Introduction to Glass Integrated Optics, S. I. Najafi, ed., (Artech House, Boston-London, 1992).

16.

R. W. Chuang and C. C. Lee, “Low-loss deep glass waveguides produced with dry silver electromigration process,” J. Lightwave Technol. 20, 1590–1597 (2002). [CrossRef]

17.

R. A. Scott and A. G. Mauk, in Cytochrome c: A Multidisciplinary Approach, (University Science Books, Sausalito, CA, 1996).

18.

E. Margoliash and N. Frohwirt, “Spectrum of Horse-Heart cytochrome c,” Biochem. J. 71, 570–572 (1959).

19.

P. Poyhonen, S. Honkanen, A. Tervonen, M. Tahkokorpi, and J. Albert, “Planar 1/8 Splitter in Glass by Photoresist Masked Silver Film Ion-Exchange,” Elect. Lett. 27, 1319–1320 (1991). [CrossRef]

20.

J. Viljanen and M. Leppihalme, “Analysis of Loss in Ion-Exchanged Glass Waveguides,” Proc. European Conf. Integrated Optics, (Institution of Electrical Engineers, London, 1981), pp.18–21.

21.

S. Honkanen and A. Tervonen, “Experimental-analysis Of Ag+-Na+ Exchange in Glass with Ag Film Ion Sources for Planar Optical Wave-Guide Fabrication,” J. Appl. Physics 63, 634–639 (1988). [CrossRef]

22.

M. Leone, A. Cupane, V. Militello, and L. Cordone, “Thermal broadening of the Soret band in heme complexes and in heme proteins: role of the iron dynamics,” Eur. Biophys. J. 23, 349–352 (1994). [CrossRef] [PubMed]

23.

A. F. Runge and S. S. Saavedra, “Comparison of microcontact-printed and solution-adsorbed cytochrome c films on indium tin oxide electrodes,” Langmuir 19, 9418–9424 (2003). [CrossRef]

OCIS Codes
(130.2790) Integrated optics : Guided waves
(130.6010) Integrated optics : Sensors
(230.7380) Optical devices : Waveguides, channeled

ToC Category:
Integrated Optics

History
Original Manuscript: March 9, 2007
Revised Manuscript: April 9, 2007
Manuscript Accepted: April 17, 2007
Published: April 24, 2007

Virtual Issues
Vol. 2, Iss. 5 Virtual Journal for Biomedical Optics

Citation
Ismail E. Araci, Sergio B. Mendes, Nasuhi Yurt, Seppo Honkanen, and N. Peyghambarian, "Highly sensitive spectroscopic detection of heme-protein submonolayer films by channel integrated optical waveguide," Opt. Express 15, 5595-5603 (2007)
http://www.opticsinfobase.org/vjbo/abstract.cfm?URI=oe-15-9-5595


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. J. D. Swalen, D. L. Allara, J. D. Andrade, E. A. Chandross, S. Garoff, J. Israelachvili, T. J. McCarthy, R. Murray, R. F. Pease, J. F. Rabolt, K. J. Wynne, and H. Yu, "Molecular Monolayers and Films," Langmuir 3, 932-950 (1987). [CrossRef]
  2. J. Homola, S. S. Yee, and G. Gauglitz, "Surface plasmon resonance sensors: review," Sens. Actuators B 54, 3-15, (1999). [CrossRef]
  3. W. D. Wilson, "Analyzing biomolecular interactions," Science 295, 2103-2105, (2002). [CrossRef] [PubMed]
  4. Biocore Product Brochure, "Biacore 3000," (2007). http://www.biacore.com/lifesciences/products/systems_overview/3000/system_information/index.html>
  5. A. F. Runge, N. C. Rasmussen, S. S. Saavedra, and S. B. Mendes, "Determination of anisotropic optical constants and surface coverage of molecular films using polarized visible ATR spectroscopy. Application to adsorbed cytochrome c films," J. Phys. Chem. B 109, 424-431 (2005). [CrossRef]
  6. S. B. Mendes, L. F. Li, J. J. Burke, J. E. Lee, D. R. Dunphy, S. S. Saavedra, "Broad-band attenuated total reflection spectroscopy of a hydrated protein film on a single mode planar waveguide," Langmuir 12, 3374-3376 (1996). [CrossRef]
  7. J. T. Bradshaw, S. B. Mendes, and S. S. Saavedra, "A simplified broadband coupling approach applied to chemically robust sol-gel, planar integrated optical waveguides," Anal. Chem. 74,1751 - 1759 (2002). [CrossRef] [PubMed]
  8. I. H. A. Badr and M. E. Meyerhoff, "Fluoride-selective optical sensor based on Aluminum (III)-octaethylporphyrin in thin polymeric film: further characterization and practical application," Anal. Chem. 77, 6719-6728 (2005). [CrossRef] [PubMed]
  9. T. Umemura, H. Hotta, T. Abe, Y. Takahashi, H. Takiguchi, M. Uehara, T. Odake, K. Tsunoda, "Slab optical waveguide high-acidity sensor based on an absorbance change of protoporphyrin IX," Anal. Chem. 78, 7511-7516 (2006). [CrossRef] [PubMed]
  10. Y. Itagaki, K. Deki, S. I. Nakashima, Y. Sadaoka, "Development of porphyrin dispersed sol-gel films as HCl sensitive optochemical gas sensor," Sens. Actuators B 117, 302-307 (2006). [CrossRef]
  11. Y. Y. Cheng, S. H. Lin, H. C. Chang, M. C. Su, "Probing adsorption, orientation and conformational changes of cytochrome c on fused silica surfaces with the soret band," J. Phys. Chem. A 107, 10687-10694 (2003) [CrossRef]
  12. S. B. Mendes and S. S. Saavedra, "Comparative analysis of absorbance calculations for integrated optical waveguide configurations by use of the Ray Optics Model and the Electromagnetic Wave Theory," Appl. Opt. 39, 612-621 (2000). [CrossRef]
  13. A. Tervonen, P. Poyhonen, S. Honkanen, M. Tahkokorpi, S. Tammela, "Examination Of 2-Step Fabrication Methods For Single-Mode Fiber Compatible Ion-Exchanged Glass Wave-Guides," Appl. Opt. 30, 338-343 (1991). [CrossRef] [PubMed]
  14. W. Lukosz, "Integrated Optical Chemical and Direct Biochemical Sensors," Sens. Actuators B 29, 37-50 (1995). [CrossRef]
  15. S. Honkanen, "Silver-Film Iob-Exchange Technique," in Introduction to Glass Integrated Optics, S. I. Najafi, ed., (Artech House, Boston-London, 1992).
  16. R. W. Chuang and C. C. Lee, "Low-loss deep glass waveguides produced with dry silver electromigration process," J. Lightwave Technol. 20, 1590-1597 (2002). [CrossRef]
  17. R. A. Scott and A. G. Mauk, in Cytochrome c: A Multidisciplinary Approach, (University Science Books, Sausalito, CA, 1996).
  18. E. Margoliash and N. Frohwirt, "Spectrum of Horse-Heart cytochrome c," Biochem. J. 71, 570-572 (1959).
  19. P. Poyhonen, S. Honkanen, A. Tervonen, M. Tahkokorpi, and J. Albert, "Planar 1/8 Splitter in Glass by Photoresist Masked Silver Film Ion-Exchange," Electron. Lett. 27, 1319-1320 (1991). [CrossRef]
  20. J. Viljanen and M. Leppihalme, "Analysis of Loss in Ion-Exchanged Glass Waveguides," Proc. European Conf. Integrated Optics, (Institution of Electrical Engineers, London, 1981), pp.18-21.
  21. S. Honkanen and A. Tervonen, "Experimental-analysis Of Ag+-Na+ Exchange in Glass with Ag Film Ion Sources for Planar Optical Wave-Guide Fabrication," J. Appl. Physics 63, 634-639 (1988). [CrossRef]
  22. M. Leone, A. Cupane, V. Militello, and L. Cordone, "Thermal broadening of the Soret band in heme complexes and in heme proteins: role of the iron dynamics," Eur. Biophys. J. 23, 349-352 (1994). [CrossRef] [PubMed]
  23. A. F. Runge and S. S. Saavedra, "Comparison of microcontact-printed and solution-adsorbed cytochrome c films on indium tin oxide electrodes," Langmuir 19, 9418-9424 (2003). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited