Controlling Optical Absorption of Graphene in Near-infrared Region by Surface Plasmons

Nowadays, graphene has many applications in optical instruments, biosensors, gas sensors, photovoltaic cells, and so on. In this study, we aimed at investigating the optical properties of graphene under the influence of plasmons created in one-dimensional photonic crystal structure by making use of the absorption spectrum. We put the gold photonic crystal in adjacent to graphene and placed an antireflection layer on top of it. Then, we studied the behavior of graphene absorption peaks in a near-infrared region. By analyzing the graphene behavior in this region, we observed that graphene absorption was increased up to 40% and graphene absorption value in absorption peak, absorption peak wavelength, absorption spectra width, and also its absorption spectra in a wide wavelength range from 1000 to 2500 nm, could be controlled by making use of different factors such as the substance of antireflection layer and photonic crystal geometric dimensions. This structure can make many applications possible for graphene such as using it to build biosensors to identify uric acid and some of the lipids that have specific significances in detecting atherosclerotic lesions as well as diagnosing the states of disease.     

High-performance Opening-up Dual-core Photonic Crystal Fiber Sensors Based on Surface Plasmon Resonance

Plasmonics - Nowadays, plasmonic sensors based on photonic crystal fiber (PCF) attracted a great deal of attention in the field of optical sensing. Opening-up dual-core photonic crystal fibers...     

Silicon photonic crystal nanocavity-coupled waveguides for error-corrected optical biosensing

A photonic crystal (PhC) waveguide based optical biosensor capable of label-free and error-corrected sensing was investigated in this study. The detection principle of the biosensor involved shifts in the resonant mode wavelength of nanocavities coupled to the silicon PhC waveguide due to changes in ambient refractive index. The optical characteristics of the nanocavity structure were predicted by FDTD theoretical methods. The device was fabricated using standard nanolithography and reactive-ion-etching techniques. Experimental results showed that the structure had a refractive index sensitivity of 10(-2) RIU. The biosensing capability of the nanocavity sensor was tested by detecting human IgG molecules. The device sensitivity was found to be 2.3±0.24×10(5) nm/M with an achievable lowest detection limit of 1.5 fg for human IgG molecules. Additionally, experimental results demonstrated that the PhC devices were specific in IgG detection and provided concentration-dependent responses consistent with Langmuir behavior. The PhC devices manifest outstanding potential as microscale label-free error-correcting sensors, and may have future utility as ultrasensitive multiplex devices.     

Magnetically assisted DNA assays: high selectivity using conjugated polymers for amplified fluorescent transduction

We report a strategy for conjugated polymer (CP)-based optical DNA detection with improved selectivity. The high sensitivity of CP-based biosensors arises from light harvesting by the CP and the related amplified fluorescent signal transduction. We demonstrate that the use of magnetic microparticles significantly improves the selectivity of this class of DNA sensors. Compared with previously reported DNA sensors with CP amplification, this novel sensing strategy displays excellent discrimination against non-cognate DNA in the presence of a protein mixture or even human serum. We also demonstrate that the magnetically assisted DNA sensor can conveniently identify even a single-nucleotide mismatch in the target sequence.     

Nanostructured material-based optical and electrochemical detection of amoxicillin antibiotic

The penicillin derivative amoxicillin (AMX) plays an important role in treating various types of infections caused by bacteria. However, excessive use of AMX may have negative health effects. Therefore, it is of utmost importance to detect and quantify the AMX in pharmaceutical drugs, biological fluids, and environmental samples with high sensitivity. Therefore, this review article provides valuable and up-to-date information on nanostructured material-based optical and electrochemical sensors to detect AMX in various biological and chemical samples. The role of using different nanostructured materials on the performance of important optical sensors such as colorimetric sensors, fluorescence sensors, surface-enhanced Raman scattering sensors, chemiluminescence/electroluminescence sensors, optical immunosensors, optical fibre-based sensors, and several important electrochemical sensors based on different electrode types have been discussed. Moreover, nanocomposites, polymer, and MXenes-based electrochemical sensors have also been discussed, in which such materials are being used to further enhance the sensitivity of these sensors. Furthermore, nanocomposite-based photo-electrochemical sensors and the market availability of biosensors including AMX have also been discussed briefly. Finally, the conclusion, challenges, and future perspectives of the above-mentioned sensing techniques for AMX detection are presented.     

New highly sensitive and selective catalytic DNA biosensors for metal ions

While remarkable progress has been made in developing sensors for metal ions such as Ca(II) and Zn(II), designing and synthesizing sensitive and selective metal ion sensors remains a significant challenge. Perhaps the biggest challenge is the design and synthesis of a sensor capable of specific and strong metal binding. Since our knowledge about the construction of metal-binding sites in general is limited, searching for sensors in a combinatorial way is of significant value. Therefore, we have been able to use a combinatorial method called in vitro selection to obtain catalytic DNA that can bind a metal ion of choice strongly and specifically. The metal ion selectivity of the catalytic DNA was further improved using a 'negative selection' strategy where catalytic DNA that are selective for competing metal ions are discarded in the in vitro selection processes. By labeling the resulting catalytic DNA with a fluorophore/quencher pair, we have made a new class of metal ion fluorescent sensors that are the first examples of catalytic DNA biosensors for metal ions. The sensors combine the high selectivity of catalytic DNA with the high sensitivity of fluorescent detection, and can be applied to the quantitative detection of metal ions over a wide concentration range and with high selectivity. The use of DNA sensors in detection and quantification of lead ions in environmental samples such as water from Lake Michigan has been demonstrated. DNA is stable, cost-effective, environmentally benign, and easily adaptable to optical fiber and microarray technology for device manufacture. Thus, the DNA sensors explained here hold great promise for on-site and real-time monitoring of metal ions in the fields of environmental monitoring, developmental biology, clinical toxicology, wastewater treatment, and industrial process monitoring.     

Use of Pseudomonas and Achromobacter species bacteria--degraders of surface-active agents--for detection and destruction of polycyclic aromatic hydrocarbons

The developed biosensor models were based on the use of immobilized Pseudomonas and Achromobacter cells for polycyclic aromatic hydrocarbons and surfactants detection. The responses of biosensors based on bacteria-degraders of anionic surfactants for organic substrates, which related to different classes of surfactants, aromatic and policyclic aromatic hydrocarbons (PAH) were investigated. The sensor showed the highest sensitivity to anionic surfactants and PAH. The lower limit of sodium dodecyl sulfate detection is within a range of 0.25-0.5 mg/l (0.86-1.73 microM). The sensors showed the highest sensitivity to naphthalene (1-6 mM) and anthracene, fluorene, phenanthrene. All strains that have been investigated may be used as a receptor element of biosensors for detection of PAH and surfactants.     

Recent progress on performances and mechanisms of carbon dots for gas sensing

Carbon dots (CDs), as an attractive zero-dimensional carbon nanomaterial with unique photoluminescent merits, have recently exhibited significant application potential in gas sensing as a result of their excellent optical/electronic characteristics, high chemical/thermal stability, and tunable surface states. CDs exhibit strong light absorption in the ultraviolet range and tunable photoluminescence characteristics in the visible range, which makes CDs an effective tool for optical sensing applications. Optical gas sensor based on CDs have been investigated, which generally responds to the target gas by corresponding changes in optical absorption or fluorescence. Moreover, electrical gas sensor and quartz crystal microbalance sensor whose sensing layer involves CDs have also been designed. Electrical gas sensor exhibits an increase or a decrease in electrical current, capacitance, or conductance once exposed to the target gas. Quartz crystal microbalance sensor responds to the target gas with a frequency shift. CDs greatly promote the absorption of the target gas and improve the sensitivity of both sensors. In this review, we aim to summarize different types of gas sensors involving CDs, and sensing performances of these sensors for monitoring diverse gases or vapors, as well as the mechanisms of CDs in different types of sensors. Moreover, this review provides the prospect of the potential development of CDs based gas sensors.     

A biomimetic olfactory-based biosensor with high efficiency immobilization of molecular detectors

The immobilization efficiency of molecular detectors is of great importance with regard to the performances of biosensors such as the sensitivity, stability, and reproducibility. This paper presents a biomimetic olfactory receptor-based biosensor with better performances by improving the immobilization efficiency of molecular detectors for odorant sensing. A mixed self-assembled monolayers (SAMs) functionalized with specific olfactory receptors (ODR-10) was constructed on the sensitive area of surface acoustic wave (SAW) chip. The immobilization of ODR-10 was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The responses of this biosensor to various odorants were recorded by monitoring the resonance frequency shifts of SAW, which is correlated to the mass loading on its sensitive area. All the results demonstrate this biosensor can specifically respond to the natural ligand of ODR-10, diacetyl, with high sensitivity and stability. The sensitivity is 4 kHz/ng, which is 2× higher than that of previous work. The detection limit is 1.2×10(-11) mM. The major advances on immobilization efficiency of molecular detectors presented in this work could substantially promote and accelerate the researches and applications of olfactory receptor-based biosensors with different transducers, such as quartz crystal microbalance (QCM), surface plasma resonance (SPR), and field effect transistors (FET).     

Multiplexed DNA quantification by spectroscopic shift of two microsphere cavities

We have developed a novel, spectroscopic technique for high-sensitivity, label-free DNA quantification. We demonstrate that an optical resonance (whispering gallery mode) excited in a micron-sized silica sphere can be used to detect and measure nucleic acids. The surface of the silica sphere is chemically modified with oligonucleotides. We show that hybridization to the target DNA leads to a red shift of the optical resonance wavelength. The sensitivity of this resonant technique is measured as 6 pg/mm(2) mass loading, higher as compared to most optical single-pass devices such as surface plasmon resonance biosensors. Furthermore, we show that each microsphere can be identified by its unique resonance wavelength. Specific, multiplexed DNA detection is demonstrated by using two microspheres. The multiplexed signal from two microspheres allows us to discriminate a single nucleotide mismatch in an 11-mer oligonucleotide with a high signal-to-noise ratio of 54. This all-photonic whispering gallery mode biosensor can be integrated on a semiconductor chip that makes it an easy to manufacture, analytic component for a portable, robust lab-on-a-chip device.     

D-Shaped Photonic Crystal Fiber–Based Surface Plasmon Resonance Biosensors with Spatially Distributed Bimetallic Layers

This paper deals with the development and analysis of D-Shaped photonic crystal fiber (PCF) biosensors using surface plasmon resonance (SPR). A thin metal layer is deposited on the outer flat surface of the PCF that behaves as the plasmonic material. Analyte is filled in the outermost peripheral region of metal layer. Finite element method (FEM) with perfectly matched layer (PML) is applied to analyze the proposed sensors. Mode analysis is performed on the proposed structures to evaluate various parameters of SPR-based PCF sensors. Three D-shaped PCF structures have been proposed with silver (Ag), gold (Au) and two-half layers of both (Ag-Au) on its flat surface. The first two structures are analyzed to the range of wavelength where the SPR will occur to facilitate understanding of the third structure. It is observed that the structures with one metal have only one sensitive plasmonic peak whereas the structure with two metal layers has two sensitive plasmonic peaks, making it suitable candidate for two-molecule sensing present in a sample analyte. Good sensitivities and resolutions are achieved for both plasmonic peaks.

     

Fibre-optic bacterial biosensors and their application for the analysis of bioavailable Hg and As in soils and sediments from Aznalcollar mining area in Spain

Fibre-optic biosensors for Hg and As were developed by attaching alginate-immobilised recombinant luminescent Hg- and As-sensor bacteria onto optical fibres. The optimised biosensors (consisting of seven layers of fibre-attached bacteria pre-grown till mid-logarithmic growth phase) enabled quantification of environmentally relevant concentrations of the target analytes: 2.6 microg l-1 of Hg(II) and 141 microg l-1 of As(V) or 18 microg l-1 of As(III). The highest viability and sensitivity for target analyte was obtained when fibre tips were stored in CaCl2 solution at -80 degrees C. Applicability of the fibre-optic biosensors in parallel to the respective non-immobilised sensors was assessed on 10 natural soil and sediment samples from Aznalcollar mining area (Spain). On the average 0.2% of the total Hg and 0.87% of the total As proved bioavailable to fibre-attached bacteria. Interestingly, about 20-fold more Hg and 4-fold more As was available to non-immobilised sensor bacteria indicating the importance of direct cell contact (possible only for non-immobilised cells) for enhanced bioavailability of these metals in solid samples.     

DNA based biosensors

Compared to advances in enzyme sensors, immunosensors, and microbial biosensors, relatively little work exists on DNA based biosensors. Here we review the DNA based biosensors that rely on nucleic acid hybridization. Major types DNA biosensors--electrochemical, optical, acoustic, and piezoelectric--are introduced and compared. The specificity and response characteristics of DNA biosensors are discussed. Overall, a promising future is foreseen for the DNA based sensor technology.     

核酸适配体光学生物传感器在卡那霉素检测中的研究进展

卡那霉素是一种氨基糖苷类抗生素,由于其效果好、价格低等优点,是我国常用兽药之一。但如果剂量过大就会大量残留在动物体内,进而通过食物链富集进入人体,引发耳毒性、肾毒性等毒副作用,严重时会导致人死亡,因此对其含量的检测十分重要。近几年,大量基于核酸适配体检测卡那霉素的光学方法被开发,以满足人们对其检测的需求。首先明确了核酸适配体与光学生物传感器等相关概念;再根据其反应机制不同,对光学方法介导的生物传感器进行了分类综述,阐述了各类传感器的基本原理及其检测范围;最后对这几类传感器的优缺点和发展前景进行了总结和展望,对这些方法的进一步探索将为食品安全检测提供新的技术支撑。     

Protein biosensors based on the principle of fluorescence resonance energy transfer for monitoring cellular dynamics

Genetically-coded, fluorescence resonance energy transfer (FRET) biosensors are widely used to study molecular events from single cells to whole organisms. They are unique among biosensors because of their spontaneous fluorescence and targeting specificity to both organelles and tissues. In this review, we discuss the theoretical basis of FRET with a focus on key parameters responsible for designing FRET biosensors that have the highest sensitivity. Next, we discuss recent applications that are grouped into four common biosensor design patterns—intermolecular FRET, intramolecular FRET, FRET from substrate cleavage and FRET using multiple colour fluorescent proteins. Lastly, we discuss recent progress in creating fluorescent proteins suitable for FRET purposes. Together these advances in the development of FRET biosensors are beginning to unravel the interconnected and intricate signalling processes as they are occurring in living cells and organisms.     

Ultrathin hydrogel films for rapid optical biosensing

Novel biosensors have been designed by reporting an analyte-induced (de)swelling of a stimuli-responsive hydrogel (usually in a form of thin film) with a suitable optical transducer. These simple, inexpensive hydrogel biosensors are highly desirable, however, their practical applications have been hindered, largely because of their slow response. Here we show that quick response hydrogel sensors can be designed from ultrathin hydrogel films. By the adoption of layer-by-layer assembly, a simple but versatile approach, glucose-sensitive hydrogel films with thickness on submicrometer or micrometer scale, which is 2 orders of magnitude thinner than films used in ordinary hydrogel sensors, can be facilely fabricated. The hydrogel films can not only respond to the variation in glucose concentration, but also report the event via the shift of Fabry-Perot fringes using the thin film itself as Fabry-Perot cavity. The response is linear and reversible. More importantly, the response is quite fast, making it possible to be used for continuous glucose monitoring.     

Evaluation of permselective membranes for optimization of intracerebral amperometric glutamate biosensors

Monitoring of extracellular brain glutamate concentrations by intracerebral biosensors is a promising approach to further investigate the role of this important neurotransmitter. However, amperometric biosensors are typically hampered by Faradaic interference caused by the presence of other electroactive species in the brain, such as ascorbic acid, dopamine, and uric acid. Various permselective membranes are often used on biosensors to prevent this. In this study we evaluated the most commonly used membranes, i.e. nafion, polyphenylenediamine, polypyrrole, polyaniline, and polynaphthol using a novel silica-based platinum electrode. First we selected the membranes with the highest sensitivity for hydrogen peroxide in vitro and an optimal selectivity against electrochemical interferents. Then we evaluated the performances of these membranes in a short lasting (3-4h) in vivo experiment. We found that best in vitro performance was accomplished with biosensors that were protected by a poly(m-phenylenediamine) membrane deposited onto the platinum electrode by cyclic voltammetry. However, post-implantation evaluation of these membranes showed poor selectivity against dopamine. Combination with a previously applied nafion layer did not protect the sensors against acute biofouling; indeed it was even counter effective. Finally, we investigated the ability of our biosensors to monitor the effect of glutamate transport blocker DL-TBOA on modulating glutamate concentrations in the prefrontal cortex of anaesthetized rats. The optimized biosensors recorded a rapid 35-fold increase in extracellular glutamate, and are considered suitable for further exploration in vivo.     

Surface‐enhanced Raman scattering‐active photonic crystal fiber probe: Towards next generation liquid biopsy sensor with ultra high sensitivity

The tremendous enhancement factors that surface‐enhanced Raman scattering (SERS) possesses coupled with the flexibility of photonic crystal fibers (PCFs) pave the way to a new generation of ultrasensitive biosensors. Thanks to the unique structure of PCFs, which allows direct incorporation of an analyte into the axially aligned air channels, interaction between the analyte and excitation light could be increased many folds leading to flexible, reliable and sensitive probes that can be used in preclinical or clinical biosensing. SERS‐active PCF probes provide unique opportunity to develop an opto‐fluidic liquid biopsy needle sensor that enables one‐step integrated sample collection and testing for disease diagnosis. Specificity being a key parameter to biosensors, the PCF inside the biopsy needle could be functionalized with targeting moieties to detect specific biomarkers. In this review article, we present some of the most promising recent biosensors based on PCFs including hollow‐core PCFs, suspended‐core PCFs and side‐channel PCFs. We provide a wide range of applications of such platform using Raman spectroscopy, label free SERS or labeled SERS detection and analyze some of the main challenges to be addressed for translating it to a clinically viable next generation sensitive biopsy needle sensing probe.     

Synergetic effect for NADH oxidation of ferrocene and zeolite in modified carbon paste electrodes. New approach for dehydrogenase based biosensors

The development of electrochemical biosensors using dehydrogenases associated with the corresponding cofactor is strongly related to the better understanding of NADH oxidation at the electrode surface. The aim is to lower the necessary overvoltage and consequently to escape interferences and electrode fouling. In this paper, we show that carbon paste electrode (CPE) modified with NaY zeolite fulfils this requirements thanks to its hydrophilic surface. Oxidation of NADH at ferrocene (FcH) modified carbon paste electrode exhibits a rather slow electrocatalytic effect. We demonstrated the existence of synergetic effect on the electrocatalytic oxidation of NADH when the CPE is doped with zeolite (NaY) and FcH mediator or with the zeolite exchanged beforehand with the mediator (Y-Ferricinium, YFcH). This cumulative effect permits to reach high sensitivity for NADH detection and offers new way for the development of enzymatic biosensors using dehydrogenases depending on NADH as cofactor.     

Front Cover: Surface‐enhanced Raman scattering‐active photonic crystal fiber probe: Towards next generation liquid biopsy sensor with ultra high sensitivity (J. Biophotonics 11/2019)

The tremendous enhancement factors possessed by surfaceenhanced Raman scattering (SERS), coupled with the flexibility of photonic crystal fibers (PCFs), pave the way to a new generation of ultrasensitive biosensors. This review article aims to provide the latest advancement in SERS‐based PCF sensors for various biochemical applications. Such a sensitive biosensor could be translated for the detection of biomarkers in body fluids for early diagnosis of diseases. Further details can be found in the article by U. S Dinish, Flavien Beffara, Georges Humbert, Jean‐Louis Auguste, and Malini Olivo ( e201900027 ).