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This PDF file contains the front matter associated with SPIE Proceedings Volume 11361 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.
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An highly efficient plasmonic/photonic devices requires precise nanoscale structural control which becomes critically essential for variety of application requirements. Advancements in lithography and deposition methods provided precise sub-nm structure with complex processing steps at high cost. Self-ssembly technique involving M13 bacteriophage (phage) provides us an alternative option with easy fabrication, high selectivity/sensitivity, and altogether with low-cost methodology. With such merits, we demonstrate two kinds of applications: A highly efficient dynamic actuator and dynamic plasmonic device. From our phage-based device it is possible to precisely control thickness in 0.2 nm step or in a broader range resulting in realization of highly efficient dynamic actuator device. Thickness modification is cross-checked using localized surface plasmon resonance (LSPR) measurements. On the other-side, variety of interesting complex plasmonic characteristics are extensively studied and an efficient plasmonic device is realized with precise sub-nm dynamic phage thickness modification. Critically, problems involving plasmonic devices which are extremely sensitive to sub-nm scale changes (≤ 1nm) can be solved utilizing dynamic M13 phage property. To strengthen dynamic plasmonic device characteristics, we introduce the metal-coated M13 phage-based nanostructures based on a simple and straight-forward drop-casting technique. Nanowires and island/NP structures are formed with precise control and reproducibilty. Nanowires with diameter range of ~ 6.6 nm – 150 nm and islands with diameter range of ~ 100 nm – 1200 nm are fabricated. By varying the humidity, highly efficient plasmonic characteristics are realized with the help of LSPR experiments. Our home-made built-in humidity chamber equipped with atomic force microscopy measurements revealed the sub-nm thickness variation of M13 phage, which agreed well with LSPR and optical simulation results. We hope our approach utilizing M13 bacteriophage as a supporting platform will open attractive applications in field of plasmonic devices, understanding complex plasmonic modes, sensors, actuators, energy devices and few other to name.
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Point-of-care tests (POCT) are important for detecting illnesses and monitoring patients without the need of a medical laboratory. To be useful, POCT must be sensitive, specific, integrated, and affordable. Since the early 2000s, integrated photonics have offered a possible solution for this problem. In particular, silicon micro-ring resonators represent a compact and sensitive choice known in the industry. This paper details the design, fabrication, and characterization of two methods for improving the performance of ring resonators by engineering their cross section. More precisely, improving devices made out of silicon nitride in an industrial environment to work in the infrared (around 1.31 µm).
The first approach is to selectively excite the first order mode of the ring resonator’s waveguide. The first order mode, with its greater exposure to the sensing liquid than the fundamental mode, results in a higher device sensitivity. The second method consists in coupling a dielectric mode with a surface plasmon polariton (SPP) forming a hybrid plasmonic waveguide. Hybrid plasmonic waveguides combine the low losses of the dielectric mode with the high sensitivity of the SPP, which increases the sensitivity in comparison to conventional dielectric ring resonators. Furthermore, hybrid plasmonic micro-ring resonators make possible a stable and easy differential functionalization.
Through the optical characterization of the devices, this study shows an experimental sensitivity of first order ring resonators of over 200 nm/RIU* and of hybrid plasmonic devices of 300 nm/RIU*. This demonstrates improvement with respect to the reference silicon nitride dielectric ring (120 nm/RIU*). Characterizations were performed using a PolyDiMethylSiloxane (PDMS) fluidic system to prove the compatibility of the substrate to POCT applications.
This paper shows two alternative approaches to integrated nano-photonic sensing for point of care testing. The proposed structures, demonstrate not only a higher sensitivity, but consider selectivity and manufacturing issues, which are fundamental for POCT development.
*RIU = Refractive Index Unit
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Enabling Technologies for Instrumentation and Lab-on-a-Chip I
MicroAnalytical Systems (µAS) adapted to Point-of-Care Testing are expected to provide simple chemical, molecular or cellular analysis to be used directly on the field. Different formats of µAS are already classically used, from pregnancy tests to glycemia for diabetic people. Increasing µAS analytical performances involves for instance improving limits of detection, reduce time of analysis, or increase the amount of information provided per test. These improvements may be reached by using more refined technology, involving integrated technologies such as biosample processing, enzymatic reactions, fluidic circuitry and/or biosensors. However being able to fabricate and produce cheap µAS relying on miniaturized components is still a challenging goal, particularly when dealing with low concentrated species. For example, on the one hand it may be interesting to use miniaturize nanotransducers in biosensors (e.g. photonic transducer enabling both SPR and SERS thanks to nanostructuration) ; but on the other hand the transducers size reduction may prevent the targets to reach the biosensor’s active zone in a short time, because of mass transfer phenomena. Futhermore, when the sensing area is small by comparison with the other µAS zones, it targets are likely to get adsorbed on undesired surfaces. These targets are therefore lost and cannot contribute to the final, useful signal of the µAS. In these conditions the effectivity of the µAS can be questionned.
Different ways are being explored to overcome such challenges, and may enable µAS for detection of low concentration targets. For instance, it is possible to perform selective chemical modifications of surfaces bearing different materials, in order to bind molecular probes only on the transducing zone, while repelling molecular targets from other material surfaces. We will show how it is possible to perform such orthogonal surfaces modifications with a submicronic spatial resolution, relying on self-assembly phenomena.
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Optical fiber sensors are of growing interest in biomedical applications, especially for early diagnosis and in situ assays. Their intrinsic properties bring numerous assets for the detection of low concentrations of analytes, such as easy light injection and the possibility to obtain remote and real-time interrogation of very low amounts of analytes. Among the different optical fiber configurations, tilted fiber Bragg gratings (TFBGs) manufactured in the core of telecommunication-grade optical fibers are known to be highly-sensitive and temperature-compensated refractometers, as they couple light to the surrounding medium. In our work, we have used different strategies to turn them into labelfree (plasmonic) immunosensors. Bare and gold-sputtered configurations were biofunctionalized with antibodies and aptamers, aiming at the detection of cancer biomarkers. In this paper, we review the biofunctionalization processes that can be used in these different cases and discuss the obtained performances. For the most sensitive configuration, we report an experimental limit of detection of 10−12 g/mL in laboratory settings.
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Liquid biopsies represent a minimally invasive tool for the precocious diagnosis of widespread diseases as well as for routinely patients monitoring by tracking selective biomarkers. Optical detection techniques based on surface enhanced Raman spectroscopy (SERS) are capable of providing information on the molecular content of analyzed samples thus representing one of the most promising analytical method in clinical research, as alternative to traditional bioassays. With the attempt to realize point-of-impact diagnostic devices, in the present study 3D printing and soft-lithography processes were combined with plasmonic nanoparticles (NPs) synthesis for the development of multifunctional lab-onchips (LOCs) integrating SERS sensors for liquid probing. As a matter of fact, LOCs enable to easily handle small volumes of samples as well as to perform multifunctional analyses. This is crucial for pathologies whose diagnosis relies on the ratio of more than one biomarker. To this end, being based on a 3D printing process, the overall design of the devices was rapidly prototyped to integrate channels and detection chambers aligned with optical fibers and portable Raman probes for signal delivering and collection. SERS functionality was achieved by immobilization of gold NPs whose chemistry was modified to enhance NPs deposition and stability. Finally, we are exploring direct laser writing for the integration of mechanical and optical microcomponents needed for liquids control and signal delivering and collection, respectively. The final devices collecting multiple functions and detection configurations will provide high sensitivity, speed of analysis, low sample and reagent consumption, measurement automation and standardization on a highly integrated dynamic platform that will revolutionize liquid biopsy making it costless, on-chip, handy and easy to use.
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Enabling Technologies for Instrumentation and Lab-on-a-Chip II
We designed a new non-contact photoplethysmographic (PPG) measurement system by adopting an imaging-PPG (iPPG) method which used specific wavelengths detection and signal processing algorithms. PPG signals can be used to obtain information about blood oxygen saturation and provide diagnostic data on cardiovascular condition and atrial fibrillation (AFib). Most traditional PPG detection methods requires contacting sensors to the measuring surface. In our study, we developed a non-contact iPPG system with its high-potential performance to reduce the processing time. The selective narrow-band filter and incorporated an active illumination lighting array are used to designed according to the blood absorption spectrum. After collecting a series of iPPG images of a preset duration, the iPPG signals were remotely analyzed using traditional methods and using our deep learning (DL) algorithms. The DL algorithm based on a long short-term memory (LSTM) model was developed to fulfill waveform improvement. An InGaAs camera and a monochrome Si camera, both set at a 50fps frame rate, were used for field image detection. The measurement data collected at 550nm wavelength are shown in the discussion. Several indicators such as heart rhythm, peak-to-peak interval error, similarity, and root mean squared errors (RMSE) were adopted to compare the DL detection iPPG signal with the ECG and PPG signals. Our newly developed iPPG system has a high potential application for personnel health monitoring.
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Enabling Technologies for Instrumentation and Lab-on-a-Chip III
Surface plasmon resonance imaging (SPRI) biosensors allow sensitive, real-time and label-free detection of biological species in fluids when they bound to the sensing surface. However, their sensitivity is now close to the theoretical limit. In particular, at ultra-low target concentration, the main limit is the diffusion of the biological target (protein, DNA, bacteria…) to the gold film surface. To locally increase the target concentration on the sensitive surface and overcome such diffusion limit, active mass transport of analytes can be induced by non-uniform electric fields using dielectrophoresis (DEP) and alternative-current electroosmosis (ACEO) flow. Depending on the frequency of the electric field applied and the conductivity of the suspension medium, DEP and ACEO can concentrate biological objects on electrodes. This work focuses on the trapping and the detection of bacteria. The gold film used for SPR imaging is also used as electrode for particle collection, after photolithography and wet etching. To obtain the most efficient electrode design, numerical simulations were performed to estimate the trapping force applied on bacteria in the fluidic chamber volume depending on the geometry of the electrodes. SPR biochips obtained were mounted in the Kretschmann configuration. Then, a DI water solution containing E.coli bacteria was injected in the fluidic chamber of the chip. AC voltage (10Vpp, 1 kHz) was applied. The arrival of bacteria on the sensing zone is monitored by a strong jump of the SPR signal when no signal was observed without mass transport. The easy integration of such DEP/ACEO-assisted SPR chips on commercial SPR benches makes them suitable fur ultralow detection of a wide range of biological species, from biomolecules to pathogens.
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This work presents current investigations to integrate photonic biosensor into a SiGe BiCMOS technology. We employ an electronic-photonic integrated circuit (EPIC) platform to combine electronic devices with optical biosensors in a single chip. This gives perspective to a fully packaged, cost-effective photonic sensor system. This technology is intended to create a large scale effect, because it enables the development of numerous applications in health-care, food analysis as well as environmental monitoring.
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Due to circumstances beyond the presenter's control, and audio recording was not possible for this presentation.
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Harmful Algal Blooms (HABs) are increasingly recognized as having profound effects upon the ecology of coastal waters and upon the economics of fisheries and aquaculture. HABs by contaminating shellfish with biotoxins affect human health and require effective surveillance and management programs to protect human consumers of seafood. Blooms of Pseudo-nitzschia producing a neurotoxin known as Domoic Acid (DA) are of increasing concern as their frequency and intensity increase rapidly. Although these toxic algal blooms represent a serious public health and economic problems, no cost-effective device, allowing the detection of dissolved DA in seawater is not yet available on the market. Surface Plasmon Resonance (SPR) biosensors have demonstrated their ability to detect small molecules at very low concentrations in real-time. We recently reported a rapid SPR biosensor inhibition assay to measure dissolved DA in the seawater matrix in-field deployment. Based on antibodies recognition, this system can detect DA at concentration over a range of 0.1–2 ng.mL−1. However, this first prototype suffered from certain limitations. Multiplexing the assay increasing of the detection range, reproducibility and sample replicates are now required. Thus, a new biosensor based on SPR imaging (SPRi) technique was developed. The prototype was designed to meet high sensitivity, compactness and cost efficiency requirements. The performances of this sensor were first studied in laboratory conditions, then it was deployed mesocosm facility. The new automated SPRi sensor showed promise for in situ detection of DA.
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The detection of DNA from a biological target is becoming a powerful tool for several applications. In particular, the development of approaches for fast and sensitive identification of genomic footprints in open-field or POCT contexts would have a tremendous impact on the identification of fraudulent or pathogenic contaminations.
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The detection of circulating tumor cells (CTCs) represents an important goal in oncological diagnosis and treatment, as CTCs are responsible for metastasis in several forms of cancer and are present at very low concentration. Their detection should occur at around 1-10 cells/mL of blood for diagnosis purpose. In this work, we propose an all-fiber plasmonic aptasensor featuring multiple narrowband resonances in the near-infrared wavelength range to detect metastatic breast cancer cells. To this aim, specific aptamers against mammaglobin-A proteins were selected and immobilized as bioreceptors on the optical fiber surface. In vitro assays confirm that label-free and real-time detection of cancer cells (LOD of 49 cells/mL) occurs within 5 minutes, while the additional use of functionalized gold nanoparticles allows a two-fold amplification of the biosensor response. Differential measurements on selected optical resonances were used to process the sensor response and results were confirmed by microscopy analysis. The detection of only 10 cancer cells/mL was performed with relevant specificity against non-target cells with comparable sizes and shapes.
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Lateral flow immunoassays (LFAs) have received much attention in recent years for detecting THC (a psychoactive ingredient of the cannabis plant) in oral fluids for point-of-care (POC) diagnostics. Specific advantages of screening oral fluids for THC include ease of sample collection in public and correlation of presence of THC in oral fluid with recent use of cannabis. However, despite their popularity, the detection limit of LFA is normally limited to greater than 25 ng/ml of THC in oral fluid which impedes the implementation of per se regulations in many jurisdictions (i.e., 1-5 ng/ml). To address this shortcoming, several LFA reader technologies have been developed in recent years but none of them have satisfied the required performance criteria of <80% sensitivity, specificity, and accuracy at per se limit, set by Driving Under the Influence of Drugs, Alcohol, and Medicines (DRUID). In this work, we explore Lock-In thermography (LIT) method for detecting THC in saliva-based LFA strips, utilizing thermal signatures of gold nanoparticles (GNPs) for interpretation of LFAs. Our results suggest that LIT enhances the limit of detection of the commercially available LFA by over an order of magnitude and promises an affordable solution that allows for proper enforcement of per se regulations worldwide.
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The effective detection of low-concentrated molecules in small volumes represents a significant challenge in many sectors such as biomedicine, safety, and pollution. Here, we show an easy way to dispense liquid droplets from few μl volume (0.2-0.5 μl) of a mother drop, used as reservoir, by using a pyro-electrohydro-dynamic jetting (p-jet) dispenser. This system is proposed for multi-purpose applications such as printing viscous fluids and as a biosensor system. The p-jet system is based on the pyroelectric effect of polar dielectric crystals such as lithium niobate (LN). The electric field generated by the pyroelectric effect acts electro-hydrodynamically on the sample of liquid, allowing the deposition of small volumes. The p-jet approach allows to obtain the dispensing of drops of very small volumes (up to tenths of a picoliter) avoiding the use of syringes and nozzles generally used in standard technologies. The reliability of the technique as a biosensor is demonstrated both in the case of oligonucleotides and in a sample of clinical interest, namely gliadin. The results show the possibility of detecting these biomolecules even when they are low abundant, i.e. down to attomolar. The results show a marked improvement in the detection limit (LOD) when compared with the conventional technique (ELISA). Moreover, it has been presented the possibility of using the p-jet as a useful tool in the detection of biomarkers, present in the blood but currently not detectable with conventional techniques and related to neurodegenerative diseases such as Alzheimer.
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The POCT technology involving low cost Lab-On-Chip label-free biosensing opens up an opportunity to drastically reduce the total cost of plant health and disease monitoring tools. The main requirement for a POCT tool is that it should involve relatively inexpensive equipment ensuring a sufficiently high accuracy of the plant disease early diagnostic. The principal objective of the presented work was to develop of a cost effective tool for biosensing assay, easy to use even for unskilled user. The label-free biosensing involving an optical near-field resonance phenomenon, such as Surface Plasmon Resonance (SPR) or localized surface plasmon resonance (LSPR), appears to be an appropriate approach for the above requirements. In this paper, we present a concept of multichannel biosensing platform dedicated to POCT, as well as the first proof-of-concept experimental investigations, demonstrating its practical feasibility. The instrumental platform investigated by our research group includes both disposable multichannel biochip and spectroscopic optical readout device. The proposed approach gives access to two plasmonic detection formats on the same lab-on-chip device: SPR and LSPR biosensing. In order to implement the LSPR sensing approach, our team has developed an original microfabrication method involving gold nanoparticles (Au_NPs) synthesis by pulsed laser writing. The biochip includes both microfluidic and biosensor structures formed into a single plastic slab.
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Sepsis, defined as the systemic inflammatory response to a confirmed or suspected source of infection, is the most severe infection-related condition and its identification can be particularly difficult in the initial stages. The importance of having a POCT platform capable of measuring sepsis biomarkers for a secure early-stage diagnosis is evident since traditional methods of pathogen determination delay treatment and also increase the recovery period for the patient. The biggest advantage of optical probes is the ability to detect low quantities of target molecules without direct contact to the sample. Nanophotonics-based sensing promises to build on the advantages of optical sensing, while overcoming its limitations by providing a high sensitivity, specificity, dynamic range, as well as the possibility for easy integration into simple and affordable devices. The project FASPEC (Fiber-based planar antennas for biosensing and diagnostics) aims at developing and prototyping a high-performance fluorescence-based molecular assay for in-vitro diagnostics that integrates lab-on-a-chip and optical readout functionalities within a single, fully automated platform. The key biophotonics innovation of the project is the replacement of the bulk optics used for collecting the fluorescence signal with a suitably designed optofluidic chip. The latter shall function as an optical antenna to direct fluorescence towards the sensor head, hence enhancing the sensitivity of the fluorescence-based assay by orders of magnitude. Application-specific lab-on-a-chip systems equipped with our high-throughput and ultrasensitive detection scheme have been envisioned.
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Optical ring micro-resonators (OMR) can be integrated onto chips to obtain sensitive, robust, low cost and portable sensor systems. They are used for in-situ real time detection of specific molecules by specialized or non- specialized persons. Target analytes, homogeneously spread in the cladding layer, induces a complex refractive index variation Δncl of the OMR waveguides upper cladding.
In this study, we propose an optimized analytical approach to OMR designs in terms of bulk sensitivity.
Those type of sensors are based on the evanescent field sensing. Interaction between the evanescent field and the analytes induces resonance wavelengths modifications. The main sensing strategy is based on resonant wavelength shift measurement. However, contrast variation, due to the absorption coefficient linked to analytes concentration, can also be measured. Colorimetric reactions, used to obtain a specific sensor, change significantly the light intensity in a specific peak of the transmission spectrum. This is due to the complex formation between a specific ligand and a heavy metal, such as hexavalent chromium and 1,5 diphenylcarbazide.
From the well-known ring resonator’s transmission expression, we can establish an analytical model of sensitivity’s dependence on geometric dimensions. Sensitivity in influenced by the round-trip attenuation coefficient a, the auto-coupling coefficient τ, the optical path and the ratio of guided power into the cladding Γcl. We validated our approach with FDTD simulation of OMR’s response for a 15 μm radius. This analytical approach makes it possible, from the waveguide propagation structure and propagation losses, to obtain both the optimal ring radius and the resonator gap in order to obtain maximum sensitivity.
Based on optical characterization of OMR, measured variations of 1% power drop at resonance should allow variation measurement on the extinction coefficient of ∆ni = 10−6.
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Lasers based on semiconductor whispering gallery mode (WGM) resonators represent a perfect platform for active small footprint high-sensitive devices for biodetection. Biochemical samples typically require aqueous solution, and the resonator should be placed into a cuvette with water or in a microfluidic chip. The characteristics of modern semiconductor WGM lasers with an active region based on InAs/InGaAs quantum dots (QDs) make them promising for creating compact highly sensitive devices for biodetection. Deep localization of carriers in InAs/InGaAs QDs and suppressed lateral migration helps us to obtain room-temperature lasing in microdisk lasers immersed in an aqueous medium. In this work, we studied the sensitivity of the microdisk laser resonance spectral position to the refractive index of the surrounding material by changing the salinity of the water solution. We also successfully detected model proteins (secondary antibodies attached to the microdisk surface) via measurement of the lasing threshold power. The proteinprotein interaction on the microdisk surface manifests itself by an increase in the laser threshold power. Thus, in this work we demonstrated, for the first time, the possibility of using QD semiconductor microdisk lasers for detection of proteins in a microfluidic device.
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The target of the present research is the design, implementation and characterization of a portable device based on an all-optical technology capable to perform simultaneously esophageal manometry, pH-metry and bilimetry by means of a single or combined catheter (OPTIMO project). It will provide physicians a compact and reliable tool to perform exhaustive diagnosis in gastroesophageal reflux pathologies. It would be definitely an innovative product in the gastroesophageal diagnostic scenario with high potential for worldwide market penetration and application developments. In particular, pressure measurement along the esophagus is performed with an array of optical fiber gratings, which ensures the monitoring along a length of about 30 cm with high spatial resolution. The sensors for the measurement of pH and bile are based on the change in absorption caused by the parameter under investigation. In the case of pH, an acid-base indicator that changes its absorption as a function of pH is immobilized on controlled pore glasses suitable coupled to plastic optical fibers. As for bile detection, the measurement is based on the direct absorption of bilirubin, the main biliary pigment, and a bundle of plastic optical fibers carries the signal. With a planned clinical assessment of the realized device, the achievement of this main objective implies the accomplishment of the following sub-tasks: i) development of optical fiber sensor for the measurement of pH; ii) development of the optical fiber sensor for bile detection; iii) development of the optical fiber manometer; iv) integration of the optical fiber sensors within a single catheter; v) realization of the portable interrogation unit for all the three parameters; vi) clinical assessment of the final device on both volunteers and patients.
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The well-known enhancement effect of surface-enhanced Raman spectroscopy (SERS) is associated with the presence of metallic nanostructures at the substrate surface. Different bottom-up and top-down processes have been proposed to impart the substrate with such a nanostructured layer. The former approaches are low cost but may suffer from reusability and stability. The latter strategies are expensive, time consuming and require special equipment that complicate the fabrication process.
Here, we present the possibility to obtain stable and reusable SERS substrates by a low-cost silver-sodium ion-exchange process in soda-lime glass microrods. The microrods were obtained by cutting the tip of the ion-exchanged soda-lime fiber, resulting in disks of about few millimeters in length and one hundred microns in diameter. A thermal annealing post-process was applied to trigger the reduction of Ag+ ions into nanoparticles (AgNPs) within the ion-exchanged glass microrods. Afterwards, ion-exchange and thermal treatments were carefully tuned to assure the presence of silver NPs exposed on the surface of the microrods, without using any chemical etching. An AFM analysis confirmed the presence of AgNPs with size of tens of nm on the surface of the fiber probe.
A SERS affinity bioassay was developed on the probe with the final aim of detecting microRNA fragments acting as biomarkers of different diseases. Specifically a DNA hybridization assay was built up by anchoring a molecular beacon containing a Raman tag on the Ag surface via thiol chemistry. Initial SERS experiments confirmed the presence of the beacon on the NPs embedded on the microrods surface, as monitored by detecting main spectral bands ascribed to the oligonucleotide chain. Finally, the ability of the platform to interact with the target microRNA sequence was assessed. The analysis was repeated on a number of miRNA sequences differing from the target to evaluate the specificity of the proposed assay.
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The paper presents a photonic smart-probe, based on a fluorescent fiber, dedicated for the point-of-care periodontal examination. Globally, periodontal diseases are prevalent both in developing and developed countries and affect about 20-50% of global population. The handpiece of the pressure sensitive periodontal probe should provide the accurately measurement of the depth of a pyorrhea pocket in a human or animal gum. Clinical attachment level (CAL) is the new gold standard for the diagnosis and monitoring of the periodontal disease. CAL has stimulated the recent introduction of novel periodontal probes. For point-of-care, a general dental practitioner usually uses low-cost first- or secondgeneration probes. They would require a low-cost smart-device (at least third-generation level), for accurate quick test results, light weight and easy to use, to avoid the wrong measurements. The proposed device is based on fluorescent linear optical fiber position sensor, adapted to the second-generation probe system. A modified surgical caliper with periodontal probe attachments, transforms the unit depth (mm-scale) of the probe into the cm-scale (according with the excitation length of the fluorescent fiber). The end of the fluorescent fiber is placed on the caliper scale and a SMD blue led attached to the caliper mobile arm is slid over the fluorescent fiber. The movable arm range is proportional with the mm depth of the periodontal probe into the gum. The T-Flame OceanOptics mini-spectrometer is used for signal processing. Lateral coupling of the excitation led light into the fluorescent fiber at different positions produces the emission spectral shift. Thus, the result of the energy transfer process changes for different lengths of the led excitation of the fluorescent fiber (at cm scale), as an overlap of the emission and absorption spectra of the PMMA co-doped fiber.
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The paper is mainly focused on assessing the local effects of climate change on biodiversity, especially within the conservation of native plant species, by using a wearable plant demonstrator for chlorophyll and growth rate monitoring. The wearable proof-of-concept is implemented with: a) blue fluorescent fiber and light diffusion fiber configuration, for chlorophyll monitoring and b) optical fiber bending measurements, proportional with growing rate of the leaf. The blue fluorescent fiber from the Industrial Optical Fiber-USA is used to monitor chlorophyll fluorescence (spectral analysis) under stimulated conditions produced with light diffusion fiber. Stimulated light is induced by the light coupled to the surface of the leaf to be analyzed, using the Corning Fibrance (LDF) light diffusion fiber. The blue fluorescent fiber-BFF (peak 460 nm) is lateral sensitive and the chlorophyll fluorescence spectrum is coupled to the fiber core. The LDF is placed on the leaf, near BFF. The chlorophyll fluorescence emission spectrum falls outside the absorption spectrum of the blue fluorophore of the doped fiber core BFF. The chlorophyll fluorescence will propagate along the fiber, adding a specific spectral response corresponding to the analyzed scenario. The spectral response reflects the change with the physiological state of the photosynthetic system.
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