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906 KiB

Open AccessArticle

An Optical Biosensor from Green Fluorescent Escherichia coli for the Evaluation of Single and Combined Heavy Metal Toxicities

by Dedi Futra, Lee Yook Heng, Asmat Ahmad, Salmijah Surif and Tan Ling Ling

Sensors 2015, 15(6), 12668-12681; https://doi.org/10.3390/s150612668 - 28 May 2015

Cited by 19 | Viewed by 6580

Abstract

A fluorescence-based fiber optic toxicity biosensor based on genetically modified Escherichia coli (E. coli) with green fluorescent protein (GFP) was developed for the evaluation of the toxicity of several hazardous heavy metal ions. The toxic metals include Cu(II), Cd(II), Pb(II), Zn(II), [...] Read more.

A fluorescence-based fiber optic toxicity biosensor based on genetically modified Escherichia coli (E. coli) with green fluorescent protein (GFP) was developed for the evaluation of the toxicity of several hazardous heavy metal ions. The toxic metals include Cu(II), Cd(II), Pb(II), Zn(II), Cr(VI), Co(II), Ni(II), Ag(I) and Fe(III). The optimum fluorescence excitation and emission wavelengths of the optical biosensor were 400 ± 2 nm and 485 ± 2 nm, respectively. Based on the toxicity observed under optimal conditions, the detection limits of Cu(II), Cd(II), Pb(II), Zn(II), Cr(VI), Co(II), Ni(II), Ag(I) and Fe(III) that can be detected using the toxicity biosensor were at 0.04, 0.32, 0.46, 2.80, 100, 250, 400, 720 and 2600 μg/L, respectively. The repeatability and reproducibility of the proposed biosensor were 3.5%–4.8% RSD (relative standard deviation) and 3.6%–5.1% RSD (n = 8), respectively. The biosensor response was stable for at least five weeks, and demonstrated higher sensitivity towards metal toxicity evaluation when compared to a conventional Microtox assay. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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2063 KiB

Open AccessArticle

Stand-Off Biodetection with Free-Space Coupled Asymmetric Microsphere Cavities

by Zachary Ballard, Martin D. Baaske and Frank Vollmer

Sensors 2015, 15(4), 8968-8980; https://doi.org/10.3390/s150408968 - 16 Apr 2015

Cited by 29 | Viewed by 7093

Abstract

Asymmetric microsphere resonant cavities (ARCs) allow for free-space coupling to high quality (Q) whispering gallery modes (WGMs) while exhibiting highly directional light emission, enabling WGM resonance measurements in the far-field. These remarkable characteristics make “stand-off” biodetection in which no coupling device is required [...] Read more.

Asymmetric microsphere resonant cavities (ARCs) allow for free-space coupling to high quality (Q) whispering gallery modes (WGMs) while exhibiting highly directional light emission, enabling WGM resonance measurements in the far-field. These remarkable characteristics make “stand-off” biodetection in which no coupling device is required in near-field contact with the resonator possible. Here we show asymmetric microsphere resonators fabricated from optical fibers which support dynamical tunneling to excite high-Q WGMs, and demonstrate free-space coupling to modes in an aqueous environment. We characterize the directional emission by fluorescence imaging, demonstrate coupled mode effects due to free space coupling by dynamical tunneling, and detect adsorption kinetics of a protein in aqueous solution. Based on our approach, new, more robust WGM biodetection schemes involving microfluidics and in-vivo measurements can be designed. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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1045 KiB

Open AccessArticle

Portable and Reusable Optofluidics-Based Biosensing Platform for Ultrasensitive Detection of Sulfadimidine in Dairy Products

by Xiu-Juan Hao, Xiao-Hong Zhou, Yan Zhang, Feng Long, Lei Song and Han-Chang Shi

Sensors 2015, 15(4), 8302-8313; https://doi.org/10.3390/s150408302 - 9 Apr 2015

Cited by 20 | Viewed by 6162

Abstract

Sulfadimidine (SM₂) is a highly toxic and ubiquitous pollutant which requires rapid, sensitive and portable detection method for environmental and food monitoring. Herein, the use for the detection of SM₂ of a portable optofluidics-based biosensing platform, which was used for [...] Read more.

Sulfadimidine (SM₂) is a highly toxic and ubiquitous pollutant which requires rapid, sensitive and portable detection method for environmental and food monitoring. Herein, the use for the detection of SM₂ of a portable optofluidics-based biosensing platform, which was used for the accurate detection of bisphenol A, atrazine and melamine, is reported for the first time. The proposed compact biosensing system combines the advantages of an evanescent wave immunosensor and microfluidic technology. Through the indirect competitive immunoassay, the detection limit of the proposed optofluidics-based biosensing platform for SM₂ reaches 0.05 μg·L⁻¹ at the concentration of Cy5.5-labeled antibody of 0.1 μg·mL⁻¹. Linearity is obtained over a dynamic range from 0.17 μg·L⁻¹ to 10.73 μg·L⁻¹. The surface of the fiber probe can be regenerated more than 300 times by means of 0.5% sodium dodecyl sulfate solution (pH = 1.9) washes without losing sensitivity. This method, featuring high sensitivity, portability and acceptable reproducibility shows potential in the detection of SM₂ in real milk and other dairy products. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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1870 KiB

Open AccessArticle

Label-Free, Single Molecule Resonant Cavity Detection: A Double-Blind Experimental Study

by Maria V. Chistiakova, Ce Shi and Andrea M. Armani

Sensors 2015, 15(3), 6324-6341; https://doi.org/10.3390/s150306324 - 16 Mar 2015

Cited by 5 | Viewed by 7298

Abstract

Optical resonant cavity sensors are gaining increasing interest as a potential diagnostic method for a range of applications, including medical prognostics and environmental monitoring. However, the majority of detection demonstrations to date have involved identifying a “known” analyte, and the more rigorous double-blind [...] Read more.

Optical resonant cavity sensors are gaining increasing interest as a potential diagnostic method for a range of applications, including medical prognostics and environmental monitoring. However, the majority of detection demonstrations to date have involved identifying a “known” analyte, and the more rigorous double-blind experiment, in which the experimenter must identify unknown solutions, has yet to be performed. This scenario is more representative of a real-world situation. Therefore, before these devices can truly transition, it is necessary to demonstrate this level of robustness. By combining a recently developed surface chemistry with integrated silica optical sensors, we have performed a double-blind experiment to identify four unknown solutions. The four unknown solutions represented a subset or complete set of four known solutions; as such, there were 256 possible combinations. Based on the single molecule detection signal, we correctly identified all solutions. In addition, as part of this work, we developed noise reduction algorithms. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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1814 KiB

Open AccessArticle

Role of Edge Inclination in an Optical Microdisk Resonator for Label-Free Sensing

by Davide Gandolfi, Fernando Ramiro-Manzano, Francisco Javier Aparicio Rebollo, Mher Ghulinyan, Georg Pucker and Lorenzo Pavesi

Sensors 2015, 15(3), 4796-4809; https://doi.org/10.3390/s150304796 - 26 Feb 2015

Cited by 20 | Viewed by 7392

Abstract

In this paper, we report on the measurement and modeling of enhanced optical refractometric sensors based on whispering gallery modes. The devices under test are optical microresonators made of silicon nitride on silicon oxide, which differ in their sidewall inclination angle. In our [...] Read more.

In this paper, we report on the measurement and modeling of enhanced optical refractometric sensors based on whispering gallery modes. The devices under test are optical microresonators made of silicon nitride on silicon oxide, which differ in their sidewall inclination angle. In our approach, these microresonators are vertically coupled to a buried waveguide with the aim of creating integrated and cost-effective devices. Device modeling shows that the optimization of the device is a delicate balance of the resonance quality factor and evanescent field overlap with the surrounding environment to analyze. By numerical simulations, we show that the microdisk thickness is critical to yield a high figure of merit for the sensor and that edge inclination should be kept as high as possible. We also show that bulk-sensing figures of merit as high as 1600 RIU^-1 (refractive index unit) are feasible. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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1219 KiB

Open AccessArticle

Ionizing Radiation Detectors Based on Ge-Doped Optical Fibers Inserted in Resonant Cavities

by Saverio Avino, Vittoria D'Avino, Antonio Giorgini, Roberto Pacelli, Raffaele Liuzzi, Laura Cella, Paolo De Natale and Gianluca Gagliardi

Sensors 2015, 15(2), 4242-4252; https://doi.org/10.3390/s150204242 - 12 Feb 2015

Cited by 9 | Viewed by 7743

Abstract

The measurement of ionizing radiation (IR) is a crucial issue in different areas of interest, from environmental safety and industrial monitoring to aerospace and medicine. Optical fiber sensors have recently proven good candidates as radiation dosimeters. Here we investigate the effect of IR [...] Read more.

The measurement of ionizing radiation (IR) is a crucial issue in different areas of interest, from environmental safety and industrial monitoring to aerospace and medicine. Optical fiber sensors have recently proven good candidates as radiation dosimeters. Here we investigate the effect of IR on germanosilicate optical fibers. A piece of Ge-doped fiber enclosed between two fiber Bragg gratings (FBGs) is irradiated with gamma radiation generated by a 6 MV medical linear accelerator. With respect to other FBG-based IR dosimeters, here the sensor is only the bare fiber without any special internal structure. A near infrared laser is frequency locked to the cavity modes for high resolution measurement of radiation induced effects on the fiber optical parameters. In particular, we observe a variation of the fiber thermo-optic response with the radiation dose delivered, as expected from the interaction with Ge defect centers, and demonstrate a detection limit of 360 mGy. This method can have an impact in those contexts where low radiation doses have to be measured both in small volumes or over large areas, such as radiation therapy and radiation protection, while bare optical fibers are cheap and disposable. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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928 KiB

Open AccessCommunication

Amplification of the Signal Intensity of Fluorescence-Based Fiber-Optic Biosensors Using a Fabry-Perot Resonator Structure

by Meng-Chang Hsieh, Yi-Hsin Chiu, Sheng-Fu Lin, Jenq-Yang Chang, Chia-Ou Chang and Huihua Kenny Chiang

Sensors 2015, 15(2), 3565-3574; https://doi.org/10.3390/s150203565 - 4 Feb 2015

Cited by 13 | Viewed by 7439

Abstract

Fluorescent biosensors have been widely used in biomedical applications. To amplify the intensity of fluorescence signals, this study developed a novel structure for an evanescent wave fiber-optic biosensor by using a Fabry-Perot resonator structure. An excitation light was coupled into the optical fiber [...] Read more.

Fluorescent biosensors have been widely used in biomedical applications. To amplify the intensity of fluorescence signals, this study developed a novel structure for an evanescent wave fiber-optic biosensor by using a Fabry-Perot resonator structure. An excitation light was coupled into the optical fiber through a laser-drilled hole on the proximal end of the resonator. After entering the resonator, the excitation light was reflected back and forth inside the resonator, thereby amplifying the intensity of the light in the fiber. Subsequently, the light was used to excite the fluorescent molecules in the reactive region of the sensor. The experimental results showed that the biosensor signal was amplified eight-fold when the resonator reflector was formed using a 92% reflective coating. Furthermore, in a simulation, the biosensor signal could be amplified 20-fold by using a 99% reflector. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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1232 KiB

Open AccessArticle

Optical Microsystem for Analysis of Diffuse Reflectance and Fluorescence Signals Applied to Early Gastrointestinal Cancer Detection

by Sara Pimenta, Elisabete M. S. Castanheira and Graça Minas

Sensors 2015, 15(2), 3138-3153; https://doi.org/10.3390/s150203138 - 30 Jan 2015

Cited by 8 | Viewed by 5609

Abstract

The detection of cancer at its earliest stage is crucial in order to increase the probability of a successful treatment. Optical techniques, specifically diffuse reflectance and fluorescence, may considerably improve the ability to detect pre-cancerous lesions. These techniques have high sensitivity to some [...] Read more.

The detection of cancer at its earliest stage is crucial in order to increase the probability of a successful treatment. Optical techniques, specifically diffuse reflectance and fluorescence, may considerably improve the ability to detect pre-cancerous lesions. These techniques have high sensitivity to some biomarkers present on the tissues, providing morphological and biochemical information of normal and diseased tissue. The development of a chip sized spectroscopy microsystem, based on these techniques, will greatly improve the early diagnosis of gastrointestinal cancers. The main innovation is the detection of the spectroscopic signals using only few, but representative, spectral bands allowing for miniaturization. This paper presents the mathematical models, its validation and analysis for retrieving data of the measured spectroscopic signals. These models were applied to a set of phantoms clearly representative of gastrointestinal tissues, leading to a more accurate diagnostic by a pathologist. Moreover, it was demonstrated that the models can use the reconstructed spectroscopic signals based only on its extraction on those specific spectral bands. As a result, the viability of the spectroscopy microsystem implementation was proved. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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2599 KiB

Open AccessArticle

A Fiber-Tip Label-Free Biological Sensing Platform: A Practical Approach toward In-Vivo Sensing

by Alexandre François, Tess Reynolds and Tanya M. Monro

Sensors 2015, 15(1), 1168-1181; https://doi.org/10.3390/s150101168 - 9 Jan 2015

Cited by 40 | Viewed by 6750

Abstract

The platform presented here was devised to address the unmet need for real time label-free in vivo sensing by bringing together a refractive index transduction mechanism based on Whispering Gallery Modes (WGM) in dye doped microspheres and Microstructured Optical Fibers. In addition to [...] Read more.

The platform presented here was devised to address the unmet need for real time label-free in vivo sensing by bringing together a refractive index transduction mechanism based on Whispering Gallery Modes (WGM) in dye doped microspheres and Microstructured Optical Fibers. In addition to providing remote excitation and collection of the WGM signal, the fiber provides significant practical advantages such as an easy manipulation of the microresonator and the use of this sensor in a dip sensing architecture, alleviating the need for a complex microfluidic interface. Here, we present the first demonstration of the use of this approach for biological sensing and evaluate its limitation in a sensing configuration deprived of liquid flow which is most likely to occur in an in vivo setting. We also demonstrate the ability of this sensing platform to be operated above its lasing threshold, enabling enhanced device performance. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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1302 KiB

Open AccessArticle

Accelerated Detection of Viral Particles by Combining AC Electric Field Effects and Micro-Raman Spectroscopy

by Matthew Robert Tomkins, David Shiqi Liao and Aristides Docoslis

Sensors 2015, 15(1), 1047-1059; https://doi.org/10.3390/s150101047 - 8 Jan 2015

Cited by 9 | Viewed by 5672

Abstract

A detection method that combines electric field-assisted virus capture on antibody-decorated surfaces with the “fingerprinting” capabilities of micro-Raman spectroscopy is demonstrated for the case of M13 virus in water. The proof-of-principle surface mapping of model bioparticles (protein coated polystyrene spheres) captured by an [...] Read more.

A detection method that combines electric field-assisted virus capture on antibody-decorated surfaces with the “fingerprinting” capabilities of micro-Raman spectroscopy is demonstrated for the case of M13 virus in water. The proof-of-principle surface mapping of model bioparticles (protein coated polystyrene spheres) captured by an AC electric field between planar microelectrodes is presented with a methodology for analyzing the resulting spectra by comparing relative peak intensities. The same principle is applied to dielectrophoretically captured M13 phage particles whose presence is indirectly confirmed with micro-Raman spectroscopy using NeutrAvidin-Cy3 as a labeling molecule. It is concluded that the combination of electrokinetically driven virus sampling and micro-Raman based signal transduction provides a promising approach for time-efficient and in situ detection of viruses. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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2326 KiB

Open AccessArticle

Real-Time, Label-Free Detection of Biomolecular Interactions in Sandwich Assays by the Oblique-Incidence Reflectivity Difference Technique

by Yung-Shin Sun and Xiangdong Zhu

Sensors 2014, 14(12), 23307-23320; https://doi.org/10.3390/s141223307 - 5 Dec 2014

Cited by 5 | Viewed by 6346

Abstract

One of the most important goals in proteomics is to detect the real-time kinetics of diverse biomolecular interactions. Fluorescence, which requires extrinsic tags, is a commonly and widely used method because of its high convenience and sensitivity. However, in order to maintain the [...] Read more.

One of the most important goals in proteomics is to detect the real-time kinetics of diverse biomolecular interactions. Fluorescence, which requires extrinsic tags, is a commonly and widely used method because of its high convenience and sensitivity. However, in order to maintain the conformational and functional integrality of biomolecules, label-free detection methods are highly under demand. We have developed the oblique-incidence reflectivity difference (OI-RD) technique for label-free, kinetic measurements of protein-biomolecule interactions. Incorporating the total internal refection geometry into the OI-RD technique, we are able to detect as low as 0.1% of a protein monolayer, and this sensitivity is comparable with other label-free techniques such as surface plasmon resonance (SPR). The unique advantage of OI-RD over SPR is no need for dielectric layers. Moreover, using a photodiode array as the detector enables multi-channel detection and also eliminates the over-time signal drift. In this paper, we demonstrate the applicability and feasibility of the OI-RD technique by measuring the kinetics of protein-protein and protein-small molecule interactions in sandwich assays. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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846 KiB

Open AccessArticle

Microencapsulated Aliivibrio fischeri in Alginate Microspheres for Monitoring Heavy Metal Toxicity in Environmental Waters

by Dedi Futra, Lee Yook Heng, Salmijah Surif, Asmat Ahmad and Tan Ling Ling

Sensors 2014, 14(12), 23248-23268; https://doi.org/10.3390/s141223248 - 5 Dec 2014

Cited by 27 | Viewed by 7067

Abstract

In this article a luminescence fiber optic biosensor for the microdetection of heavy metal toxicity in waters based on the marine bacterium Aliivibrio fischeri (A. fischeri) encapsulated in alginate microspheres is described. Cu(II), Cd(II), Pb(II), Zn(II), Cr(VI), Co(II), Ni(II), Ag(I) and [...] Read more.

In this article a luminescence fiber optic biosensor for the microdetection of heavy metal toxicity in waters based on the marine bacterium Aliivibrio fischeri (A. fischeri) encapsulated in alginate microspheres is described. Cu(II), Cd(II), Pb(II), Zn(II), Cr(VI), Co(II), Ni(II), Ag(I) and Fe(II) were selected as sample toxic heavy metal ions for evaluation of the performance of this toxicity microbiosensor. The loss of bioluminescence response from immobilized A. fischeri bacterial cells corresponds to changes in the toxicity levels. The inhibition of the luminescent biosensor response collected at excitation and emission wavelengths of 287 ± 2 nm and 487 ± 2 nm, respectively, was found to be reproducible and repeatable within the relative standard deviation (RSD) range of 2.4–5.7% (n = 8). The toxicity biosensor based on alginate micropsheres exhibited a lower limit of detection (LOD) for Cu(II) (6.40 μg/L), Cd(II) (1.56 μg/L), Pb(II) (47 μg/L), Ag(I) (18 μg/L) than Zn(II) (320 μg/L), Cr(VI) (1,000 μg/L), Co(II) (1700 μg/L), Ni(II) (2800 μg/L), and Fe(III) (3100 μg/L). Such LOD values are lower when compared with other previous reported whole cell toxicity biosensors using agar gel, agarose gel and cellulose membrane biomatrices used for the immobilization of bacterial cells. The A. fischeri bacteria microencapsulated in alginate biopolymer could maintain their metabolic activity for a prolonged period of up to six weeks without any noticeable changes in the bioluminescence response. The bioluminescent biosensor could also be used for the determination of antagonistic toxicity levels for toxicant mixtures. A comparison of the results obtained by atomic absorption spectroscopy (AAS) and using the proposed luminescent A. fischeri-based biosensor suggests that the optical toxicity biosensor can be used for quantitative microdetermination of heavy metal toxicity in environmental water samples. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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341 KiB

Open AccessArticle

A Coumarin-Based Fluorescent Probe as a Central Nervous System Disease Biomarker

by Ann-Chee Yap, Ummi Affah Mahamad, Shen-Yang Lim, Hae-Jo Kim and Yeun-Mun Choo

Sensors 2014, 14(11), 21140-21150; https://doi.org/10.3390/s141121140 - 10 Nov 2014

Cited by 3 | Viewed by 6029

Abstract

Homocysteine and methylmalonic acid are important biomarkers for diseases associated with an impaired central nervous system (CNS). A new chemoassay utilizing coumarin-based fluorescent probe 1 to detect the levels of homocysteine is successfully implemented using Parkinson’s disease (PD) patients’ blood serum. In addition, [...] Read more.

Homocysteine and methylmalonic acid are important biomarkers for diseases associated with an impaired central nervous system (CNS). A new chemoassay utilizing coumarin-based fluorescent probe 1 to detect the levels of homocysteine is successfully implemented using Parkinson’s disease (PD) patients’ blood serum. In addition, a rapid identification of homocysteine and methylmalonic acid levels in blood serum of PD patients was also performed using the liquid chromatography-mass spectrometry (LC-MS). The results obtained from both analyses were in agreement. The new chemoassay utilizing coumarin-based fluorescent probe 1 offers a cost- and time-effective method to identify the biomarkers in CNS patients. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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1893 KiB

Open AccessArticle

Modeling and Analysis of a Microresonating Biosensor for Detection of Salmonella Bacteria in Human Blood

by Mahdi Bahadoran, Ahmad Fakhrurrazi Ahmad Noorden, Kashif Chaudhary, Faeze Sadat Mohajer, Muhammad Safwan Aziz, Shahrin Hashim, Jalil Ali and Preecha Yupapin

Sensors 2014, 14(7), 12885-12899; https://doi.org/10.3390/s140712885 - 18 Jul 2014

Cited by 40 | Viewed by 9973

Abstract

A new photonics biosensor configuration comprising a Double-side Ring Add-drop Filter microring resonator (DR-ADF) made from SiO₂-TiO₂ material is proposed for the detection of Salmonella bacteria (SB) in blood. The scattering matrix method using inductive calculation is used to determine [...] Read more.

A new photonics biosensor configuration comprising a Double-side Ring Add-drop Filter microring resonator (DR-ADF) made from SiO₂-TiO₂ material is proposed for the detection of Salmonella bacteria (SB) in blood. The scattering matrix method using inductive calculation is used to determine the output signal’s intensities in the blood with and without presence of Salmonella. The change in refractive index due to the reaction of Salmonella bacteria with its applied antibody on the flagellin layer loaded on the sensing and detecting microresonator causes the increase in through and dropper port’s intensities of the output signal which leads to the detection of SB in blood. A shift in the output signal wavelength is observed with resolution of 0.01 nm. The change in intensity and shift in wavelength is analyzed with respect to the change in the refractive index which contributes toward achieving an ultra-high sensitivity of 95,500 nm/RIU which is almost two orders higher than that of reported from single ring sensors and the limit of detection is in the order of 1 × 10⁻⁸ RIU. In applications, such a system can be employed for a high sensitive and fast detection of bacteria. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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Review

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2621 KiB

Open AccessReview

Enhanced Vibrational Spectroscopies as Tools for Small Molecule Biosensing

by Souhir Boujday, Marc Lamy de la Chapelle, Johannes Srajer and Wolfgang Knoll

Sensors 2015, 15(9), 21239-21264; https://doi.org/10.3390/s150921239 - 28 Aug 2015

Cited by 28 | Viewed by 9401

Abstract

In this short summary we summarize some of the latest developments in vibrational spectroscopic tools applied for the sensing of (small) molecules and biomolecules in a label-free mode of operation. We first introduce various concepts for the enhancement of InfraRed spectroscopic techniques, including [...] Read more.

In this short summary we summarize some of the latest developments in vibrational spectroscopic tools applied for the sensing of (small) molecules and biomolecules in a label-free mode of operation. We first introduce various concepts for the enhancement of InfraRed spectroscopic techniques, including the principles of Attenuated Total Reflection InfraRed (ATR-IR), (phase-modulated) InfraRed Reflection Absorption Spectroscopy (IRRAS/PM-IRRAS), and Surface Enhanced Infrared Reflection Absorption Spectroscopy (SEIRAS). Particular attention is put on the use of novel nanostructured substrates that allow for the excitation of propagating and localized surface plasmon modes aimed at operating additional enhancement mechanisms. This is then be complemented by the description of the latest development in Surface- and Tip-Enhanced Raman Spectroscopies, again with an emphasis on the detection of small molecules or bioanalytes. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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3300 KiB

Open AccessReview

Interferometric Reflectance Imaging Sensor (IRIS)—A Platform Technology for Multiplexed Diagnostics and Digital Detection

by Oguzhan Avci, Nese Lortlar Ünlü, Ayça Yalçın Özkumur and M. Selim Ünlü

Sensors 2015, 15(7), 17649-17665; https://doi.org/10.3390/s150717649 - 20 Jul 2015

Cited by 85 | Viewed by 14639

Abstract

Over the last decade, the growing need in disease diagnostics has stimulated rapid development of new technologies with unprecedented capabilities. Recent emerging infectious diseases and epidemics have revealed the shortcomings of existing diagnostics tools, and the necessity for further improvements. Optical biosensors can [...] Read more.

Over the last decade, the growing need in disease diagnostics has stimulated rapid development of new technologies with unprecedented capabilities. Recent emerging infectious diseases and epidemics have revealed the shortcomings of existing diagnostics tools, and the necessity for further improvements. Optical biosensors can lay the foundations for future generation diagnostics by providing means to detect biomarkers in a highly sensitive, specific, quantitative and multiplexed fashion. Here, we review an optical sensing technology, Interferometric Reflectance Imaging Sensor (IRIS), and the relevant features of this multifunctional platform for quantitative, label-free and dynamic detection. We discuss two distinct modalities for IRIS: (i) low-magnification (ensemble biomolecular mass measurements) and (ii) high-magnification (digital detection of individual nanoparticles) along with their applications, including label-free detection of multiplexed protein chips, measurement of single nucleotide polymorphism, quantification of transcription factor DNA binding, and high sensitivity digital sensing and characterization of nanoparticles and viruses. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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2014 KiB

Open AccessReview

Optical Nano Antennas: State of the Art, Scope and Challenges as a Biosensor Along with Human Exposure to Nano-Toxicology

by Abu Sulaiman Mohammad Zahid Kausar, Ahmed Wasif Reza, Tarik Abdul Latef, Mohammad Habib Ullah and Mohammad Ershadul Karim

Sensors 2015, 15(4), 8787-8831; https://doi.org/10.3390/s150408787 - 15 Apr 2015

Cited by 27 | Viewed by 11732

Abstract

The concept of optical antennas in physical optics is still evolving. Like the antennas used in the radio frequency (RF) regime, the aspiration of optical antennas is to localize the free propagating radiation energy, and vice versa. For this purpose, optical antennas [...] Read more.

The concept of optical antennas in physical optics is still evolving. Like the antennas used in the radio frequency (RF) regime, the aspiration of optical antennas is to localize the free propagating radiation energy, and vice versa. For this purpose, optical antennas utilize the distinctive properties of metal nanostructures, which are strong plasmonic coupling elements at the optical regime. The concept of optical antennas is being advanced technologically and they are projected to be substitute devices for detection in the millimeter, infrared, and visible regimes. At present, their potential benefits in light detection, which include polarization dependency, tunability, and quick response times have been successfully demonstrated. Optical antennas also can be seen as directionally responsive elements for point detectors. This review provides an overview of the historical background of the topic, along with the basic concepts and parameters of optical antennas. One of the major parts of this review covers the use of optical antennas in biosensing, presenting biosensing applications with a broad description using different types of data. We have also mentioned the basic challenges in the path of the universal use of optical biosensors, where we have also discussed some legal matters. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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1720 KiB

Open AccessReview

Algal Biomass Analysis by Laser-Based Analytical Techniques—A Review

by Pavel Pořízka, Petra Prochazková, David Prochazka, Lucia Sládková, Jan Novotný, Michal Petrilak, Michal Brada, Ota Samek, Zdeněk Pilát, Pavel Zemánek, Vojtěch Adam, René Kizek, Karel Novotný and Jozef Kaiser

Sensors 2014, 14(9), 17725-17752; https://doi.org/10.3390/s140917725 - 23 Sep 2014

Cited by 55 | Viewed by 12453

Abstract

Algal biomass that is represented mainly by commercially grown algal strains has recently found many potential applications in various fields of interest. Its utilization has been found advantageous in the fields of bioremediation, biofuel production and the food industry. This paper reviews recent [...] Read more.

Algal biomass that is represented mainly by commercially grown algal strains has recently found many potential applications in various fields of interest. Its utilization has been found advantageous in the fields of bioremediation, biofuel production and the food industry. This paper reviews recent developments in the analysis of algal biomass with the main focus on the Laser-Induced Breakdown Spectroscopy, Raman spectroscopy, and partly Laser-Ablation Inductively Coupled Plasma techniques. The advantages of the selected laser-based analytical techniques are revealed and their fields of use are discussed in detail. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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