Optical Fiber Ring Cavity Sensor for Label-Free DNA ... - IEEE Xplore

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IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 18, NO. 3, MAY/JUNE 2012

Optical Fiber Ring Cavity Sensor for Label-Free DNA Detection Alessandro Candiani, Michele Sozzi, Annamaria Cucinotta, Member, IEEE, Stefano Selleri, Senior Member, IEEE, Rosanna Veneziano, Roberto Corradini, Rosangela Marchelli, Paul Childs, and Stavros Pissadakis

Abstract—An outcladding sensitized label-free DNA biosensor is developed based on tilted fiber Bragg gratings. The biosensor, functionalized with peptide nucleic acid (PNA) probes, is based on a double tilted fiber Bragg grating that forms a modified Fabry–Perot core-cladding closed-loop cavity. Interference is set up between an injected guided mode and the reflected core mode and cladding modes created by the light scattered by the tilted gratings, leading to the generation of interference fringes within both these spectral notches. When the DNA binds to the PNA probes attached onto the fiber cladding, a refractive index change occurs at the cladding– PNA interface and the fringe visibility changes accordingly. Realtime spectral measurement results are reported, showing that a 10nM DNA solution induces a 10% modulation of the corresponding fringes visibility. Cycling tests are performed for measuring and checking the repeatability of the sensor. Index Terms—Biosensors, DNA detection, optical fiber sensors, tilted fiber Bragg grating (TFBG).

I. INTRODUCTION IOSENSOR technology has attracted considerable academic and industrial interest during the last three decades, playing a significant analytical role in different applications. In particular, the market trend shows how the biosensor industry is expanding particularly in certain areas: medical, environmental, food, quarantine control, safety, and security, as well as defense [1]. Medical-infection control represents the dominant player for pathogen-detecting biosensors; involving applications from diagnostic tests for common diseases to hospital tests for contagious bacterium. In the environmental sector, biosensors are capable of monitoring environmental quality parameters and detecting pathogen elements to avoid large-scale contaminations. In the security/defense sector, focusing on terrorist organizations and bacteriological war, there is an increasing need

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Manuscript received May 15, 2011; revised July 18, 2011; accepted August 3, 2011. Date of publication August 30, 2011; date of current version June 1, 2012. This work was supported by EUROBIOTECH—European Biotechnology project. The work of S. Pissadakis and P. Childs was supported by the EU Project SP4-Capacities “IASIS” under Contract 232479. A. Candiani, M. Sozzi, A. Cucinotta, and S. Selleri are with the Department of Information Engineering, University of Parma, Parma 43100, Italy (e-mail: [email protected]; [email protected]; [email protected]; [email protected]). R. Veneziano, R. Corradini, and R. Marchelli are with the Department of Organic and Industrial Chemistry, University of Parma, Parma 43100, Italy (e-mail: [email protected]; [email protected]; [email protected]). P. Childs and S. Pissadakis are with the Foundation for Research and Technology-Hellas, Institute of Electronic Structure and Laser, Heraklion 70013, Greece (e-mail: [email protected]; [email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/JSTQE.2011.2166110

for rapid detection of biological agents with high sensitivity and specificity. But probably the area where biosensor technology will be exploited more in the near future is the food industry [2]. This sector has taken a very conservative approach to the introduction of biosensors but would benefit from improvements in quality control, safety, and traceability that this approach can offer, for the characterization of raw materials, and recognizing specific contaminants, as well as pathogens. Another fundamental aspect of such a technology as a commercial tool is due to the fact that a biosensor can be considered as an autonomous testing laboratory, producing results quickly and at reduced costs. A biosensor is an analytical device that couples an immobilized biospecific recognition element to the surface of a transducer, which converts a molecular recognition event into a measurable signal. Different principles of detection have been studied [2], including electrochemical, mechanical, optical, and calorimetric measurements. Optical-based biosensors are reported to be one of the most widely used transduction methods. Among the optical-based systems, fiber-optic biosensors offer the main advantage to have a small, flexible shape able to be placed in small vessels and in tissues, connecting a remote light source to a small in situ sensing element; furthermore, they are able to give rapid and sensitive detection of the target in real time. There are two detection protocols that can be implemented in optical fiber biosensing: fluorescence-based detection and label-free detection [3]. In the former, the analytes are labeled with fluorescent tags, such as dyes, and the intensity of the fluorescence indicates the presence of the target molecule and interaction strength between analyte and biospecific recognition element. In label-free detection, the target molecules are not labeled or altered, and they can be detected by attachment on a suitably functionalized substrate, inducing surface-localized refractive-index changes, optical absorption loss or scattering, while being detected using optical phase-sensitive measurements or even Raman spectroscopy [4], [5]. In the literature, several optical designs have been widely reported that utilize one of these two approaches to implement biosensors. By using a suspended core photonic crystal fiber, it is possible to infiltrate the microcapillaries with nanolitre quantities of fluorescent analyte solutions and to detect their presence through the corresponding fluorescence signal [6], [7]. Other groups have used a fiber optic long period grating (LPG) as core-cladding mode couplers to detect the interaction between the recognition element on the functionalized fiber surface and the cladding modes [8], [9]. A different approach uses tilted fiber Bragg gratings (TFBGs) previously functionalized as a

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CANDIANI et al.: OPTICAL FIBER RING CAVITY SENSOR FOR LABEL-FREE DNA DETECTION

Fig. 1. Structure of the DTFBG sensor showing the core/cladding coupling due to the blazed gratings and the standard core-to-core mode Bragg scattering [12].

transducer for biosensing [10]. The coupling between the forward-propagating core mode and the counter-propagating cladding mode occurs, and the molecular recognition event is measured through the spectral transmission response of the TFBG modified by the external refractive-index changes. The possibility of using plasmon resonances in a gold-coated TFBG has also been investigated to detect DNA [11]. In this study, a new approach is presented to implement a DNA label-free sensor. Such technology is based on an optical fiber ring cavity sensor, utilizing a double TFBG (DTFBG) as a detector element. A specific functionalization of the external surface of the fiber has been performed, and a liquid handling system composed of Teflon tubing has been implemented for the packaging and functionalization of the fiber sensor. Significant spectral modulations in the visibility of the fringes have been measured after harmonic analysis and repeatability has been proved by making several tests. The experimental results are reported, demonstrating the feasibility of a DNA sensor based on a DTFBG for a variety of specific molarities exhibiting a wide dynamic range. II. DOUBLE TILTED FIBER BRAGG GRATING The DTFBG sensor [12] consists of two identical blazed fiber gratings separated by a distance d, see Fig. 1, forming a Fabry–Perot structure that creates two interferences. At the Bragg wavelength, the light incident on the grating is reflected back into the core, creating a Fabry–Perot interference. At lower wavelengths, there is a ring resonance of reflections from the core mode to the cladding modes and, then, back into the original core mode. Interference in a spectral mode can be modeled as T (λ) = E (λ) [1 + V cos (2πσλ + ϕ)]

(1)

where T(λ) is the transmission spectrum of the sensor, E(λ) is the envelope spectrum of the mode, V is the visibility of fringes, σ is the frequency of the interference, and ϕ is a phase offset. Measurement of the refractive index of the medium surrounding the fiber can be achieved by using the resonant cavity structure, where the level of interference between the two blazed gratings will change according to how much light is lost from the counter-propagating cladding modes. When the refractive index surrounding the fiber next is lower than that of the effective refractive index of the cladding modes ncl , it is weakly guided and can recouple back into the core mode, as shown in Fig. 1. On the other hand, when the refractive index of the medium surrounding the fiber is quite close to that of the silica glass, guidance is broken and the cladding modes will leach out

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of the fiber, preventing the formation of interference and causing V to approach zero. DTFBG sensors have already been used successfully as a standard refractive index sensor [12], as well as a magnetic field sensor [13], when used in conjunction with a ferromagnetic colloid. The working principle of this type of sensors relies on the measurement of the T spectrum visibility due to a variation of the medium surrounding the fiber cladding. By applying the Fourier transform to (1), it is possible to calculate the visibility as will be explained in detail in Section IV. A highly resonant collection of cladding modes, commonly called the ghost mode [14], [15], stands out in particular from the cladding mode spectrum. When the tilt angle is approximately 4–5◦ a similar amount of coupling to both the Bragg and ghost modes can be seen. The ghost mode peak, rather than individual cladding modes, is used for the analysis due to the following advantages. 1) Stability: The cladding mode structure disappears as the surrounding refractive index approaches that of cladding, making it increasingly difficult to identify the location of particular cladding modes. The envelope of the ghost mode peak, however, remains the same. 2) Simplicity: The ghost mode has a very clean Fourier spectrum, consisting solely of the Fourier transform of the ghost mode envelope separated from the two sidebands at the frequency of the interference. The cladding mode spectrum is modulated both by the ring interference, as well as the mode structure, which is heavily chirped. This causes broadening, overlap, and mixing of frequency components in the Fourier domain that make it complicated to distinguish just the ring interference component. 3) Sensitivity: Generally higher order cladding modes are considered more sensitive; however, in terms of the visibility, which goes to zero at the critical point of next = ncl , these “more sensitive” modes begin to respond earlier, further away from this critical point, giving them a greater dynamic range but less differential response near next = ncl than what is the case for the lower order modes that comprise the ghost mode. The main advantage in using such a device in biosensing applications is the relative insensitivity to temperature and strain changes. Excepting the thermo-optic changes to the surrounding liquid, these effects only cause a shift in the wavelength spectrum thus only altering the phase, not the magnitude, of the Fourier spectrum. This is particularly advantageous compared to LPG sensors [16], which are highly sensitive to temperature changes. If temperature measurements are desired, then the Bragg mode that is localized to the core can be exploited for this purpose. A software package [17] was designed to perform the required Fourier analysis and is used in this study to automate the processing of the DTFBG sensor. III. FUNCTIONALIZATION AND HYBRIDIZATION PROCESS In order to show that specific recognition of a biological analyte could be determined by the DTFBG sensor, a

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Fig. 3. Scheme of the external fiber surface after the functionalization procedure.

Fig. 2. Scheme of the sealed cell setup used. Once the fiber is fixed into the teflon cell, all the functionalization and hybridization process including the measurements are done by infiltration of liquids without touching the fiber.

well-established model of selective capture of a DNA strand by complementary peptide nucleic acid (PNA) probes has been used. PNA molecules are well known to bind in a very effective way and have a high specificity to complementary DNA strands [18], and they are considered to be one of the best types of probes for DNA recognition, being able to discriminate very efficiently between DNA sequences differing for a single-base mismatch [19]. PNA is not able to be strongly adsorbed to the fiber surface, but strategies for covalent linking of the PNA to the inner or outer surfaces of structured optical fibers have been developed. In our previous work, the internal surfaces of the holes of a suspended core optical fiber were functionalized with PNA molecules and labeled DNA hybridization was demonstrated with fluorescence measurements [20]. In this study, the same procedure has been applied to the external part of the optical fiber surrounding the region, where the DTFBG has been inscribed. According to the literature, a silanization procedure [21], [22] is considered as one of the most stable for silica glass. The functionalization protocol is the one described in [20]; anyway, a summarized description of the procedure is reported as follows in order to underline the differences with the previous protocol used. 1) Cleaning and activation of the external surface of the optical fiber immersing the fiber with the gratings in a bath of the solution for 30 min and, then, rinsed with distilled water three times and dried with nitrogen. 2) Silanization: Immersing the fiber in a bath of the reagent and, subsequently, washed with ethanol twice and dried with nitrogen. 3) Reaction of the amino groups: The reaction is performed by passing the reagents through a teflon tubing system, where the part of the fiber with the gratings has been sealed. The reagents are loaded into a glass syringe and injected into the system at a fixed flow rate of 0.16 μL/min by means of a syringe pump (KD Scientific 100 series). Following the reaction, the fiber is rinsed with N,N-dimethylformamide (DMF) for 2 h at a flow rate of 4 μL/min. In Fig. 2, a scheme of the system is represented.

TABLE I PNA AND DNA SEQUENCES USED IN THIS STUDY

4) Activation of the carboxylic function, at a flow rate of 0.16 μL/min. The fiber is, subsequently, rinsed with DMF dry for 2 h at a flow rate of 4 μL/min. 5) PNA binding to the carboxylic functional groups by the reaction of the activated ester to the PNA probe terminal amino group, at a flow rate of 0.16 μL/min. 6) Quenching of the excessive activated esters for 4 h at a flow rate of 1 μL/min. In Fig. 3, the fiber surface after functionalization is represented. After the functionalization of the fiber, hybridization was performed with different concentrations of DNA solutions: 10 nM, 100 nM, and 1 μM diluted in a buffer solution. The system used to perform the hybridization is the same as that used for the surface modification. The DNA solutions flowed through the system for about 1 h at a rate of 1 μL/min. The DNA used for the experiments were commercially available oligonucleotides provided by Thermo Fisher Scientific, Waltham, MA. The sequences of PNA and DNA used are reported in Table I. The strand of the DNA used was composed of 35 bases and coded for a sequence containing a single-nucleotide polymorphism (SNP) relevant for the analysis of tomato varieties. Measurement using mismatched DNA strands, containing the SNP, has been made to prove that this device is able to recognize a DNA sequence with just one SNP. This could be very interesting in order to discriminate between different vegetables varieties. The PNA sequence that has been used is composed of 13 bases and has been designed and synthesized containing the part of the sequence, where the SNP is present, thus enabling it to selectively recognize the target variety.


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Fig. 4. Transmission spectrum, resolution = 10 pm, of the DTFBG after functionalization and encapsulation in the Teflon tubing system. The interference fringes appear in the Bragg, ghost, and cladding modes.

Fig. 5. Scheme of the setup implemented: PNA-functionalized and nonfunctionalized fibers were monitored together in real-time, every 5 minutes recording both transmission spectra using OSAs. Both fibers were sealed as shown Fig. 2.

IV. RESULTS AND DISCUSSION A. Experimental Setup Two identical 4-mm long blazed gratings with a separation of 30 mm and a tilt angle of 3.2◦ were inscribed in photosensitive fiber (GF1B, Thorlabs) using 193 nm ultraviolet laser radiation and a phase mask. Fig. 4 shows the transmission spectrum of the fiber after the functionalization process. The measurements were made in a clean room environment with a temperature control system. An amplified stimulated emission (ASE) source (ASE 1600 from NTT Electronics, Saddle Brook, NJ) was used as a broadband light source and an optical spectrum analyzer (OSA) (Ando AQ-6315 A) as the receiver. The hybridization procedure was performed on two different fibers, the first one that has been functionalized with the PNA as described earlier and the second one nonfunctionalized that has been taken as a reference. The light was delivered to both fibers through a 50/50 fiber coupler and collected to the OSA with a single-mode fiber patchcord for both fibers, interchanging the input connector between the two fibers used. Transmission spectra of both fibers have been recorded every 5 min over the entire duration of the hybridization phase. The data were subsequently postprocessed evaluating the visibility only in the ghost-mode region (1553.9–1554.6 nm). In Fig. 5, the experimental setup is represented. Both fibers are inserted in the reagent cell setup shown in Fig. 2.

Fig. 6. Visibility of fringes response versus time for the reference fiber (lower graph) and the functionalized fiber (upper graph) for two different concentrations of the DNA solution. Between the two experiments, the system was infiltrated with PBS to clean the fiber surface, see the break in the x-axis. The different offset of the two fibers used is due to small differences in the fabrication process.

B. Experimental Results After the functionalization process a phosphate buffer saline (PBS) solution was infiltrated in the liquid handling system in order to evaluate the stability of the system. Then, a 10-nM DNA solution was passed through in the system for 1 h. The results presented in Fig. 6 show the behavior of the two different fibers during this experiment. In the lower graph, the fringe visibility of the nonfunctionalized fiber, which was used as a reference, is reported, while in the upper graph, the functionalized fiber shows a clear decrease of the visibility of fringes during the first 60 min. The amount of light that is lost from the cladding modes at the interface with the external surface of the fiber can be affected only by the optical coefficients, primarily the refractive index as there is not enough evanescent field for the attenuation to be significant, just beyond this surface. When the DNA binds to the PNA, it replaces buffer solution molecules within a few nanometers from the surface of the fiber, resulting in a refractive-index change near the sensor surface. This change can be detected optically as the sensing transduction signal. Surface plasmon resonance (SPR), photonic crystal, and optical ring resonator sensors use similar sensing strategies to implement biosensors [3]. We postulate that in our experiment, the binding corresponds to an increase in the refractive index of the medium surrounding the fiber corresponding to the hybridization process. Other

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Fig. 7. Details of the transmission spectra in the inverse wavelength domain for the initial (black line) and final (red line) spectra of the experiment done with the 10-nM DNA solution.

studies, see [5], suggested that the DNA attachment layer has a refractive index similar to that of silica, justifying the increase of the surrounding refractive index and high yield of sensitivity obtained herein, as well as the judicious choice of the DTFBG sensor design. For the first 50 min, the modulation of the fringe visibility showed a net decrease in the modulation. As reported in Section II, the fringe visibility is stable with respect to temperature. Moreover, the consistency of the fiber reference fringes is a further confirmation that the change of fringe visibility of the functionalized fiber is mainly due to a refractive index change on the fiber surface and not due to other phenomena, such as density changes in the outcladding or a specific absorption of DNA onto the fibers. The change in visibility is slightly above 10% compared to the initial value. In order to evaluate the visibility changes, the data were analyzed with harmonic analysis as already mentioned in Section II. From (1), we have ˆ (s) ∗ δ (s) + V ei s/σ [δ (s − σ) + δ (s + σ)] F (T ) {s} = E 2 (2) where F(T){s} is the Fourier transform of the transmission specˆ (s) is the Fourier transform of the envelope spectrum trum, E E(λ), s is the inverse variable of the Fourier transform dual to λ, and ∗ is the convolution operator. A spectrum wide harmonic approximation to the visibility of the fringes can be defined in the Fourier domain by dividing the average alternating component, at s = σ, by the average slowly varying component, at s = 0: +σ 2 |F (T ) {s}| σ1 σs=σ σ 1−σ 2 (3) V = σ2 s=0 |F (T ) {s}| where σ 1 and σ 2 are half-widths of the triangles in the Fourier domain, given by the Fourier transform of the interference, to allow full windowing of the respective dc and first interference peaks without overlapping each other, see Fig. 7. In (3), good stability of the Fourier spectrum requires no discontinuity at the edges of the spectral range selected, else ripples due to the Gibbs phenomenon will appear and obscure

Fig. 8. Fiber has been rehybridized twice after being washed for more than 24 h with the PBS solution. The trend of the fringe visibility modulation is similar for both experiments.

the analysis of the interference peak. As such the spectrum is normalized prior to the Fourier processing. In Fig. 7, the details of the inverse wavelength domain of the transmission spectra at the beginning (black line) and at the end (red line) of the experiment are reported, with the change of the Fourier transforms clearly visible. In the graph, the definition of visibility used for the analysis and defined in Section II appears more clearly. Visibility is the ratio between the average alternating component, caused by the ring cavity interference, and the average slowly varying component, which describes essentially the dc component of the spectrum. After this first experiment, other measurements were carried out using the same functionalized fiber in order to evaluate the saturation point. Solutions with higher DNA concentrations were infiltrated in the system to check if the range of the fringe visibility would increase. Washing with PBS for 20 min induced partial recovery increase of the fringe visibility, whereas rehybridization with a 100-nM DNA solution, see Fig. 6 (right), induced a second decrease reaching almost the same final value, thus suggesting that saturation of the fiber was already reached. A second washing followed by infiltration with a 1-μM DNA solution gave similar results (data not shown). In all cases, the reference fiber did not show any significant change under the same treatment. In light of these results, we used the 10-nM solution to verify the reproducibility of a single measurement. The recovery of the fringe visibility was improved by washing the fiber with PBS for a longer time, more than 24 h. The rehybridization process was implemented using the same conditions described earlier. Though the initial value of visibility was lower, a similar shift as that of Fig. 6 was observed, as shown in Fig. 8. A third washing with PBS followed by hybridization showed responsiveness of the fiber, with a smaller modulation, but showing the same trend. The different initial value of visibility can be caused by a memory effect of the device, given by several factors. First, a different number of active sites occupied by


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measurements were analyzed using the same parameters of the previous experiments. Two different tests done on the same fiber showed that the change in visibility for this additional test was of the same extent of the reference fiber, as shown in Fig. 10, proving the high sensor selectivity. V. CONCLUSION

Fig. 9. Same fiber has been used four times after being washed for more than 24 h with the PBS solution. The graph shows more than one order of magnitude of difference in visibility modulation with respect to the reference fiber.

This study shows for the first time the application of DTFBG fibers for the direct label-free DNA detection. The system was shown to give a specific response only when the fiber was functionalized, with good sensitivity for a solution with a very low concentration of 10 nM, and lack of interference. Moreover, tests made using mismatched DNA strands showed that the sensor can discriminate an SNP of the DNA strand. This approach can be extended to other recognition elements and to other target analytes, such as proteins or contaminants, and can eventually be used in extremely narrow contexts, where large and less flexible platforms cannot easily operate. REFERENCES

Fig. 10. Graph shows the average change in visibility for the functionalized fiber with full-match DNA, with mismatch DNA, and the reference fiber.

DNA molecules after the washing process, washing reverses the hybridization process but not completely. Second, the high local sensitivity of such a device, which presents an optical response that is strongly dependent on the location of binding sites on the fiber surface. These parameters can be improved through optimization of the washing step in order to reduce time and to obtain the same initial conditions. However, the experimental data suggest that the specific effect of the DNA on the fiber can still be visible for several hybridization steps. Analyzing the distribution of different experiments made on the same fibers using the 10-nM DNA solution, we can observe a clear difference in terms of visibility change between the tests made with the functionalized fiber and reference fiber, as shown in Fig. 9. Considering the starting and ending points of each test, the functionalized fiber presents an average change of visibility μ = 0.006 with standard deviation σ = 0.001, which is more than one order of magnitude bigger with respect to the nonfunctionalized fiber, having μ = 0.0004 and σ = 0.0002. An additional control experiment was done using mismatched DNA strands, containing the SNP, to prove that this device is able to recognize a DNA sequence with just one SNP. Using the same procedure described earlier, a 10-nM mismatch DNA solution was infiltrated into the liquid handling system and spectral

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Alessandro Candiani received the B.S. and M.S. degrees from the University of Parma, Parma, Italy, in 2005 and 2009, respectively, where he is currently working toward the Ph.D. degree in the Department of Information Engineering, working on optical fiber sensors. He was a Visiting Student for 1 year in the Universidad de Las Palmas de Gran Canaria, Spain, and 1 year at the Foundation for Research and TechnologyHellas (FORTH), Greece, working on sensor development using photonic crystal fibers. He was in the FORTH group working on ferrofluid infiltrated microstructured optical fiber photonic devices for 1 year.

Stefano Selleri (SM’08) was born in Bologna, Italy, in 1966. He received the Laurea degree (cum laude) in electronic engineering from Bologna University, Bologna, Italy, in 1991, and the Ph.D. degree from the University of Parma, Parma, Italy, in 1995. Since 1997, he has been a Researcher in the Department of Information Engineering, University of Parma, where he became an Associate Professor in March 2002. His current research interests include numerical methods for modal and propagation analysis of electromagnetic fields in conventional, photonic crystal, and holey fibers, as well as conventional and photonic crystal integrated optics waveguides, optical amplification, fiber-based amplifiers and lasers, and optical sensing.

Rosanna Veneziano was born in Calitri (AV), Italy, in 1983. She received the Food Technologies degree in “food technologies” from the University of Basilicata, Potenza, Italy, in 2007, with the experimental thesis “Pre-refrigeration system in pressure on single pallet.” She received the Laurea degree in “food science and technologies” from the Faculty of Agriculture, University of Parma, Parma, Italy, in 2011.

Roberto Corradini was born in Reggio Emilia, Italy, in 1963. He received the Laurea degree (cum laude) in chemistry and the Ph.D. degree in chemical sciences from Parma University, Parma, Italy, in 1987 and 1992, respectively. During 1995 to 2000, he was a Researcher in the Department of Organic and Industrial Chemistry, University of Parma, where he has been an Associate Professor since April 2000. His current research interests include development of synthetic systems able to perform molecular and chiral recognition, synthesis of modified PNAs and their use in biomolecular recognition of nucleic acids, and development of new drugs targeting DNA and diagnostic tools for detection of DNA of interest in biomedical and food diagnostics.

Michele Sozzi was born in Parma, Italy, in 1982. He received the Laurea degree in telecommunication engineering from the University of Parma, Parma, Italy, in 2008, where he is currently working toward the Ph.D. degree in the Department of Information Engineering. His current research interests include near-field optical microscopy, photonic crystal fibers, and optical fiber sensors.

Annamaria Cucinotta (M’08) was born in Parma, Italy, in 1969. She received the Laurea degree (cum laude) in physics and the Ph.D. degree in information technology from the University of Parma, Parma, in 1995 and 1999, respectively. From February 2000 to December 2003, she was a Contract Researcher in the Department of Information Engineering, University of Parma, where she has been an Assistant Professor in the Faculty of Engineering since December 2003. Her current research interests include fiber laser sources, photonic crystal fibers, optical fiber amplifiers, sensing, and numerical methods for electromagnetic field analysis.

Rosangela Marchelli received the Graduate degree in chemistry from the University of Pavia, Pavia, Italy, in 1965. From 1967 to 1969, she was a Postdoctoral Fellow at the National Research Council of Canada, Halifax, Canada. Since 1970, she has been with the University of Parma, Parma, Italy, where she became a Full Professor of organic chemistry in 1986 and has been the Dean of the Faculty of Agriculture since 1993. She is delegate of the Italian Chemical Society in the Division of Food Chemistry of European Chemical and Molecular Sciences (EuCheMS). She is also a member of the Nutrition, Dietetics and Food Allergy (NDA) Panel of European Food Safety Authority (EFSA). She was involved in the chemistry of natural products, biosynthesis of mould metabolites, amino acids, peptides, and myco toxins. She was also engaged in the study of the mechanisms of chiral discrimination and the development of new methods for chiral separations. Her current research interests include the study of chiral PNAs, as a mean to perform molecular recognition of DNA.


Paul Childs was born in Sydney, NSW, Australia, in 1980. He received the B.Sc. degree in physics, the M.Sc.Tech. degree in photonics, and the Ph.D. degree in electrical engineering) from the University of New South Wales (UNSW), Sydney, Australia, in 2000, 2002 and 2007 respectively. From 2000 to 2002 he was with JDS Uniphase, Sydney, Australia, from 2006 to 2007 with the University of New South Wales, Sydney, Australia, as a Research Assistant and from 2008 to 2009 with Tsinghua University, Beijing, China, as a Postdoctoral Fellow. He is currently with the Foundation for Research and Technology-Hellas, Heraklion, Greece, as a Postdoctoral Fellow. His research interests include fiber grating sensors and optical signal processing.

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Stavros Pissadakis was born in Chania, Greece, in 1972. He received the Ptichion degree in physics from the University of Crete, Greece, in 1994, and the Ph.D. degree from the Optoelectronics Research Centre (ORC), University of Southampton, Southampton, U.K., in 2000. He wasa Research Fellow in the ORC in 2000, a Visiting Lecturer in the Department of Computer and Electronic Engineering, Technical University of Crete, Greece, in 2002, and a Visiting Assistant Professor in the Department of Physics, University of Crete, in 2005–2006. Since January 2003, he has been with the Foundation for Research and Technology-Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), Greece, as an Associate Researcher and was elected to Researcher Grade D later being promoted to the Principal Researcher (Reader level) in 2009. He has been involved in the activities European Technological Platform Photonics21, while he coordinates a similar Platform for Photonics in Greece (PhotonicsG R ). His current scientific interests include development of optical fiber devices for switching and sensing applications, microstructured and photonic crystal fiber devices, laser nanoprocessing and study of photosensitivity of optical materials.