Optical Biosensor Research Articles

Optical fiber LSPR sensor for SARS-CoV-2 N gene detection based on AuNRs

A novel SARS-CoV-2 N gene optical fiber biosensor based on ASO-coated gold nanorods is proposed in this work. A fiber probe prepared by AuNRs self-assembly was used to detect N gene by complementary base pairing method. The detected material was processed into AuNRs-ASO2-N gene coupler by cross-linking, and the pairing of N gene with ASO1 connected to AuNRs on the surface of the optical fiber formed the hydrogen bonding. The coupling of AuNRs resulted in a left shift of the peak position and a decrease in absorbance in the LSPR spectrum. In this manuscript, it is verified for the first time by simulation and experimental characterization that the coupling mode of AuNRs on the surface of the optical fiber is side by side, which leads to a left shift of the peak position of the LSPR absorption peak on the optical fiber. It is also proved that sandwich method is superior to the traditional method of changing the refractive index. The response time of the sensor is 10 min, and the detection limit is 1 pM, and the results show that the optical fiber sensor based on ASO-coated AuNRs has excellent RNA detection performance in artificial body fluids and is very suitable for RNA detection.

A new colorimetric lactate biosensor based on CUPRAC reagent using binary enzyme (lactate-pyruvate oxidases)-immobilized silanized magnetite nanoparticles

A novel optical lactate biosensor is presented that utilizes a colorimetric interaction between H2O2 liberated by a binary enzymatic reaction and bis(neocuproine)copper(II) complex ([Cu(Nc)2]2+) known as CUPRAC (cupric reducing antioxidant capacity) reagent. In the first step, lactate oxidase (LOx) and pyruvate oxidase (POx) were separately immobilized on silanized magnetite nanoparticles (SiO2@Fe3O4 NPs), and thus, 2 mol of H2O2 was released per 1 mol of the substrate due to a sequential enzymatic reaction of the mixture of LOx-SiO2@Fe3O4 and POx-SiO2@Fe3O4 NPs with lactate and pyruvate, respectively. In the second step, the absorbance at 450 nm of the yellow-orange [Cu(Nc)2]+ complex formed through the color reaction of enzymatically produced H2O2 with [Cu(Nc)2]2+ was recorded. The results indicate that the developed colorimetric binary enzymatic biosensor exhibits a broad linear range of response between 0.5 and 50.0 µM for lactate under optimal conditions with a detection limit of 0.17 µM. The fabricated biosensor did not respond to other saccharides, while the positive interferences of certain reducing compounds such as dopamine, ascorbic acid, and uric acid were minimized through their oxidative removal with a pre-oxidant (NaBiO3) before enzymatic and colorimetric reactions. The fabricated optical biosensor was applied to various samples such as artificial blood, artificial/real sweat, and cow milk. The high recovery values (close to 100%) achieved for lactate-spiked samples indicate an acceptable accuracy of this colorimetric biosensor in the determination of lactate in real samples. Due to the increase in H2O2 production with the bienzymatic lactate sensor, the proposed method displays double-fold sensitivity relative to monoenzymatic biosensors and involves a neat color reaction with cupric-neocuproine having a clear stoichiometry as opposed to the rather indefinite stoichiometry of analogous redox dye methods.Graphical

Celebrating biomimicry: bioinspired layers in optical biosensors

Optical sensors have seamlessly integrated the progress of materials science, giving rise to a novel class of devices. These cutting-edge sensors incorporate bioinspired sensing layers, coatings, and mechanisms, tailor-made for various specialized applications in fields like medicine, industry, and technology. This advancement paves the way for groundbreaking improvements in biosensor technology, offering enhanced capabilities for detecting and analyzing various substances in diverse settings. In this brief report the recent and future challenges in biosensors applying bioinspired sensing layers, as well as advances in science and technology to meet them, are presented.

Four-core fiber-based multi-tapered WaveFlex biosensor for rapid detection of Vibrio parahaemolyticus using nanoparticles-enhanced probes

Infections caused by Vibrio parahaemolyticus (V. parahaemolyticus) can be highly fatal, making rapid and sensitive detection of them is essential. A new optical fiber biosensor based on localized surface plasmon resonance (LSPR) phenomenon is developed in this paper. A tapered-in-tapered fiber structure based on MFM is constructed by using four-core fiber (FCF) and multi-mode fiber (MMF) to qualitatively detect different concentrations of V. parahaemolyticus. The sensor successfully excites the LSPR phenomenon and increases the attachment point of biomolecules on the probe surface by fixing gold nanoparticles (AuNPs), molybdenum disulfide nanoparticles (MoS2-NPs) and cerium dioxide nanorods (CeO2-NRs). The functionalization of polyclonal antibodies on the probe surface can improve the specificity of the sensor. The linear detection range of the developed sensor was 1 × 100-1 × 107 CFU/mL, the sensitivity was 1.61 nm/[CFU/mL], and the detection limit was 0.14 CFU/mL. In addition, the reusability, reproducibility, stability, and selectivity of the sensor probe are also tested, which shows that the sensor has great application prospects.

Analysis of Tapered Fibre Optic Surface Plasmon Resonance Bio-Sensor Chip With Highly Perturbed Taper Profiles.

A numerical model based on the Transfer matrix method (TMM) is proposed for the first time to study the gold coated tapered fibre optic surface plasmon resonance (SPR) with eight different types of taper profiles namely linear, exponential-linear, Gaussian, quadratic, sinusoidal, error function type and highly perturbed taper profile so-called chirp type of profile. The performance in terms of sensitivity, full width at half maximum (FWHM), detection accuracy (D.A.), amplitude dip, and half power points are estimated with respect to tapering ratio and choices of taper profile. It is found that sensitivity increased almost linearly with the taper ratio of each taper choice for the account of the reduction of detection accuracy. It has been found that sensitivity is highest for the case of chirp taper profile and lowest for the case of quadratic taper profile at low taper ratio. In this study, the aqueous solution is considered for sensor development which is adulterated by biomolecules species like DNA, blood samples, etc.

Optimization of Optical Biosensor Based on 1D Photonic Crystals with Metaheuristic Algorithms for Measuring Glucose Concentration

We aim to simulate an optimal optical biosensor based on one-dimensional crystal photonics, for measuring blood and urine glucose concentration. By optimizing the sensor structure through metaheuristic optimization algorithms, sensitivity was increased. To measure blood and urine glucose concentration, these materials are used as a defect layer in one-dimensional crystal photonics, consisting of three materials: magnesium fluoride (MgF2), borosilicate glass (BK7), and orphan iodide (LiI) with refractive indices of 37/1, 1/5, and 1/99. By changing the concentration of glucose, the refractive index of the defect layer changes, changing the optical properties of the defect layer in the photonic crystal and the spectrum of transmitted and reflected light. According to the amount of light absorption by glucose, a wavelength range of 900–2200 nm (near infrared) was used as the input light. The transfer matrix method was used to calculate multi-layer systems. This method is based on the definition of two matrices, the boundary matrix and the diffusion matrix, which can be used to directly apply the boundary conditions. By plotting the spectrum passing through the crystal using the transfer matrix method and determining the location of the peak in the spectrum, the sensitivity of the sensor was calculated for different concentrations of glucose in blood and urine. The sensitivity obtained before optimization was 530 nm RIU−1, while after optimization it reached 842 nm RIU−1.

An Optofluidic Young Interferometer for Electrokinetic Transport-Coupled Biosensing.

Label-free optical biosensors, such as interferometers, can provide a comparable limit of detection to widely used enzyme-linked immunosorbent assays while minimizing the number of steps and reducing false positives/negatives. In 2020, the authors reported on a novel optofluidic Young interferometer (YI) that could provide real-time spatial information on refractive index changes occurring along the length of the sensor and reference channels. Herein, we exploit these features of the YI to study interactions of biomolecules with recognition elements immobilized in selected regions of agarose gel in the sensor channel. We show that the YI is well suited for the biosensing of an exemplar biomolecule, streptavidin, in the absence and presence of the bovine serum albumin interferent. Equally, we couple the YI with electrokinetic transport to reduce the time needed for biosensing.

Phenomena Behind Optical Biosensors: A Review

The paper provides fundamentals of a sensor and its parameters. It explains the basic phenomena behind optical biosensors qualitatively. It also includes recent advancements in the field of optical biosensors giving emphasis on the plasmon enhanced electric field phenomenon. It creates interest to develop new sensing schemes based on fluorescence and SERS devices.

A surface plasmon resonance biosensor for bacteria and virus detection: A Comsol Multiphysics simulation

This study provides a comprehensive simulation-based investigation into the design and performance optimization of a surface plasmon resonance (SPR) biosensor. The main goal of this study is to improve sensitivity and accuracy by combining optical and colorimetric biosensing techniques. The biosensor is studied, examined, and simulated using Comsol Multiphysics. Sensing medium, black phosphorus, tungsten diselenide (WSe2), gold (Au), magnetite (Fe3O4), and N-BK7 glass as prism are the layers that make up the structure of the proposed sensor. The study evaluates various parameters such as electric potential distribution, surface temperatures, conductive heat flux, eigenfrequency, electric field norm, and temperature gradients. The use of WSe2 aims for a higher sensitivity for detecting biomolecules. This paper proves the effect of using Fe3O4 and WSe2 among the six layers of the sensor in increasing the selectivity and sensitivity of the SPR biosensor. The findings reveal intricate interactions between the biosensor layers, which influence its thermal and electromagnetic behavior. The findings of this study contribute to the advancement of SPR biosensor technology, which has the potential for a variety of applications in the biomedical field.

Enhancing optical biosensing: Comparing two physical treatments for GPTES chemical functionalization of Cyclo-Olefin Copolymer foil

Cyclo-olefin-copolymer (COC) transparent films are currently the best choice for micro-fluidic bio-sensors for point-of-care diagnostic applications using optical signal detection. However, while the optical and mechanical properties of this polymer are extremely good, the adhesion of the bio-probes on this surface is not optimal, due to its chemical structure, that presents only saturated carbon bonds. The deposition of organo-silane molecules on the COC surface is one of the most effective ways to overcome this problem. But, for the surface functionalization, a surface physical treatment is necessary before the chemical modification of the COC surface. In this paper a comparison of the effectiveness of two different physical treatments, oxygen plasma and UV-ozone, is reported. In particular, the exposure time of the UV-Ozone treatment has been selected to avoid the problem of auto-fluorescence of the modified COC surface, that was observed also for relatively short UV exposure (around 10 min). An investigation of the reactive radicals created on the surface after the physical treatments and the following chemical modification with the organo-silane molecule (GPTES) has been performed using X-ray photoemission spectroscopy. The surface energy and morphology of the films have been also measured by contact angle and optical profilometry. Finally, the bio-probes adhesion performances of the COC surfaces obtained with the two physical treatments and the chemical modification were tested in a fluorescence-based assay, using an organic light emission diode to excite the fluorescence. We observed that the UV-ozone treatment allows to obtain a siloxane network with some reactive epoxy radicals on the COC surface, however, their quantity and distribution are less important and homogeneous than in the oxygen plasma treated surfaces.

Corrosive Pseudomonas aeruginosa detection by measuring pyocyanin with a lab-on-fiber optical surface plasmon resonance biosensor in aquatic environments

Oceanic facilities and equipment corrosion present considerable economic and safety concerns, predominantly due to microbial corrosion. Early detection of corrosive microbes is pivotal for effective monitoring and prevention. Yet, traditional detection methods often lack specificity, require extensive processing time, and yield inaccurate results. Hence, the need for an efficient real-time corrosive microbe monitoring technology is evident. Pseudomonas aeruginosa, a widely distributed microorganism in aquatic environments, utilizes its production of quinone-like compounds, specifically pyocyanin (PYO), to corrode metals. Here, we report a novel fiber optic surface plasmon resonance (SPR) sensor modified by the C-terminal of BrlR protein (BrlR-C), which is a specific receptor of PYO molecule, to detect P. aeruginosa in aquatic environments. The results showed that the sensor had a good ability to recognize PYO in the concentration range of 0–1 μg/mL, and showed excellent sensing performance in real-time monitoring the growth status of P. aeruginosa. With a strong selectivity of PYO, the sensor could clearly detect P. aeruginosa against other bacteria in seawater environment, and exhibited excellent anti-interference ability against variations in pH, temperature and pressure and other interfering substances. This study provides a useful tool for monitoring corrosive P. aeruginosa biofilm in aquatic environments, which is a first of its kind example that serves as a laboratory model for the application of fiber optic technology in real-world scenarios to monitoring biofilms in microbial corrosion and biofouling.

A unique wheel-shaped exposed core LSPR-PCF sensor for dual-peak sensing: Applications in the optical communication bands, M-IR region and biosensing

Photonic Crystal Fibers (PCF) effectiveness in practice decreases if the fabrication of the sensor becomes too complex. Keeping this in mind, we propose a one-of-a-kind wheel shaped PCF sensor with an exposed core containing only three air holes with exceptional sensing features. The sensor is equipped with dual plasmonic layers, Indium Tin Oxide (ITO, 10 % wt) and silver (Ag) with a coating of TiO2 to enhance the sensing capabilities and provide protection against oxidation. The sensor's distinctive configuration enables it to exhibit two distinct peaks within a range of refractive index from 1.32 to 1.38 for y-polarization and from 1.35 to 1.38 for x-polarization. The sensor specifications have been optimized to achieve the maximum levels of wavelength sensitivity (WS) and double peak shift sensitivity (DPSS). The sensor portrays a WS of 50,652 nm/RIU and the highest DPSS ever recorded, measuring 50,000 nm/RIU. Additionally, the sensor exhibits a significantly high scale of amplitude sensitivity (AS) of 1668.34 RIU−1 which is a very remarkable value considering silver as plasmonic material along with an outstanding figure of merit (FOM) of 1017.11 RIU−1. In addition, our sensor is able to manifest resolutions in the order of 10−6, demonstrating a resolution of 5.94 × 10−6 RIU with the deployment of amplitude interrogation method and 1.97 × 10−6 RIU with the wavelength interrogation method. The design spans an extensive spectrum, covering ultraviolet to mid-infrared wavelengths, enabling detection of biomolecules and biochemicals, along with operation in the optical communication band.

A “turn-on” nano-biosensor based on the Ti3C2(OH)2 MXene nanosheets and DNA-silver nanoclusters for miRNA detection

This study presents a new and efficient method for detecting miRNA-191 by utilizing Ti3C2(OH)2 MXene Nanosheets. MicroRNAs have been established as important indicators of various types of cancer and other medical conditions, highlighting the need for dependable miRNA identification techniques. The proposed approach in this study revolves around the development of an enzyme-free, simple, quick, and label-free fluorescence probe. The combination of ssDNA-modified silver nanoclusters and Ti3C2(OH)2 MXene nanosheets generates a turn-on platform for detecting miRNAs. The utilization of MXenes, a novel two-dimensional material, has generated significant interest among researchers due to their exceptional properties, including sensitivity enhancement, stability, and reproducibility in biological fluids. The study revealed that ssDNA-AgNCs interact with the MXene surface using π-π stacking, resulting in the adsorption and quenching of fluorescence in AgNCs. The presence of the target molecule (miRNA-191) leads to the formation of a probe/target complex, which the releases ssDNA-AgNCs and restores their fluorescence. This fluorescence recovery is utilized to measure the concentration of miRNA-191. The designed platform exhibited excellent analytical performance with a linear range of 0.1–100 nM and a limit of detection (LOD) of ∼65 pM. The developed bioassay offers several advantages, such as ease of operation, cost-effectiveness, rapid results, and good stability and specificity. Notably, the optical biosensor based on Ti3C2(OH)2 MXene represents the first instance of such technology being applied to detect miRNAs. Additionally, the bioassay displayed satisfactory performance when assessed with real samples.

Specific Detection of Uropathogenic Escherichia coli via Fourier Transform Infrared Spectroscopy Using an Optical Biosensor.

Urinary tract infections (UTIs) are caused mainly by uropathogenic Escherichia coli (UPEC), accounting for both uncomplicated (75%) and complicated (65%) UTIs. Detecting UPEC in a specific, rapid, and timely manner is essential for eradication, and optical biosensors may be useful tools for detecting UPEC. Recently, biosensors have been developed for the selective detection of antigen-antibody-specific interactions. In this study, a methodology based on the principle of an optical biosensor was developed to identify specific biomolecules, such as the PapG protein, which is located at the tip of P fimbriae and promotes the interaction of UPEC with the uroepithelium of the human kidney during a UTI. For biosensor construction, recombinant PapG protein was generated and polyclonal anti-PapG antibodies were obtained. The biosensor was fabricated in silicon supports because its surface and anchor biomolecules can be modified through its various properties. The fabrication process was carried out using self-assembled monolayers (SAMs) and an immobilized bioreceptor (anti-PapG) to detect the PapG protein. Each stage of biosensor development was evaluated by Fourier transform infrared (FTIR) spectroscopy. The infrared spectra showed bands corresponding to the C-H, C=O, and amide II bonds, revealing the presence of the PapG protein. Then, the spectra of the second derivative were obtained from 1600 to 1700 cm-1 to specifically determine the interactions that occur in the secondary structures between the biological recognition element (anti-PapG antibodies) and the analyte (PapG protein) complex. The analyzed secondary structure showed β-sheets and β-turns during the detection of the PapG protein. Our data suggest that the PapG protein can be detected through an optical biosensor and that the biosensor exhibited high specificity for the detection of UPEC strains. Furthermore, these studies provide initial support for the development of more specific biosensors that can be applied in the future for the detection of clinical UPEC samples associated with ITUs.

Effectively detecting cardiac myoglobin by use of bound states in the continuum in silicon nitride gratings

Optical biosensors with their sensitivity, compact design, and reliability stand out as versatile tools capable of detecting a wide range of analytes. Recently, nanophotonic structures supporting bound states in the continuum (BIC) modes have been actively studied, which is especially interesting for biosensing applications due to their high quality (Q) factor and strongly localized electric field, achieving favorable interaction between field and nanometer scale analyte on the sensing surface. Herein, we demonstrate an optical label-free sensing by accidental or Friedrich–Wintgen (FW) BIC supported on silicon nitride gratings. We compared the sensing performance in terms of bulk, and surface sensitivity, and figure of merit with FW-BIC in the leaky regime and with a symmetry-protected (SP) BIC, which are also supported by the studied platform. We exploit the fact that for FW-BIC a high-Q factor up to 498 comparable to that of SP-BIC (up to 425) retains for a much larger set of interrogation angles, providing excellent interrogation stability. We observed that FW-BIC has slightly higher bulk sensitivity than SP-BIC [186 and 158 nm/RIU (refractive index unit), respectively], but at the same time similar characteristics in terms of surface sensitivity and figure of merit. In addition, we show that both BIC resonances are significantly superior in all respects to the leaky regime due to better field confinement. Finally, the surface of sensing device was also functionalized to detect a cardiac biomarker, myoglobin, exhibiting the limit of detection of 49 ng/ml with clinically relevant level.

Recent Developments on Optical Aptasensors for the Detection of Pro‐Inflammatory Cytokines with Advanced Nanostructures

AbstractIn the realm of immune response, pro‐inflammatory cytokines play a crucial role in regulating various physiological functions. Accurate measurement of these low‐molecular‐weight proteins is essential for understanding immune function, predicting diseases, and monitoring treatment effects. Optical aptasensors with advanced nanostructures, which utilize aptamers as bio‐probes, have emerged as a promising technology for cytokine detection, offering advantages over traditional antibody‐based nanobiosensors. Aptamers, single‐stranded nucleic acids with high specificity and affinity, enable cost‐effective mass production and consistent quality. Optical biosensors incorporating aptamers exhibit stability, resistance to environmental factors, and prolonged functionality. This review explores the current methodologies and advancements in optical aptasensors for cytokine detection, highlighting their potential as robust tools in diagnostics and therapeutics. Specifically, the applications of surface plasmon resonance and fluorescence techniques in aptasensors are discussed, focusing on the innovative approaches used to enhance sensitivity and specificity in cytokine detection. Notable examples of aptasensor designs utilizing nanoparticles, Förster resonance energy transfer, and amplification strategies are presented. These designs demonstrate high affinity, specificity, and improved sensitivity in detecting pro‐inflammatory cytokines such as interferon gamma. Overall, optical aptasensors show great promise in advancing the understanding of cytokine‐related disorders and enabling effective interventions.

Synergizing Nanomaterials and Artificial Intelligence in Advanced Optical Biosensors for Precision Antimicrobial Resistance Diagnosis.

Antimicrobial resistance (AMR) poses a critical global One Health concern, ensuing from unintentional and continuous exposure to antibiotics, as well as challenges in accurate contagion diagnostics. Addressing AMR requires a strategic approach that emphasizes early stage prevention through screening in clinical, environmental, farming, and livestock settings to identify nonvulnerable antimicrobial agents and the associated genes. Conventional AMR diagnostics, like antibiotic susceptibility testing, possess drawbacks, including high costs, time-consuming processes, and significant manpower requirements, underscoring the need for intelligent, prompt, and on-site diagnostic techniques. Nanoenabled artificial intelligence (AI)-supported smart optical biosensors present a potential solution by facilitating rapid point-of-care AMR detection with real-time, sensitive, and portable capabilities. This Review comprehensively explores various types of optical nanobiosensors, such as surface plasmon resonance sensors, whispering-gallery mode sensors, optical coherence tomography, interference reflection imaging sensors, surface-enhanced Raman spectroscopy, fluorescence spectroscopy, microring resonance sensors, and optical tweezer biosensors, for AMR diagnostics. By harnessing the unique advantages of these nanoenabled smart biosensors, a revolutionary paradigm shift in AMR diagnostics can be achieved, characterized by rapid results, high sensitivity, portability, and integration with Internet-of-Things (IoT) technologies. Moreover, nanoenabled optical biosensors enable personalized monitoring and on-site detection, significantly reducing turnaround time and eliminating the human resources needed for sample preservation and transportation. Their potential for holistic environmental surveillance further enhances monitoring capabilities in diverse settings, leading to improved modern-age healthcare practices and more effective management of antimicrobial treatments. Embracing these advanced diagnostic tools promises to bolster global healthcare capacity to combat AMR and safeguard One Health.

High-quality quasi-bound state in the continuum enabled single-nanoparticle virus detection.

Bound states in the continuum (BICs) have emerged as a powerful platform for boosting light-matter interactions because they provide an alternative way of realizing optical resonances with ultrahigh quality(Q-) factors, accompanied by extreme field confinement. In this work, we realized an optical biosensor by introducing a quasi-BIC (qBIC) supported by an elaborated all-dielectric dimer grating. Thanks to the excellent field confinement within the air gap of grating enabled by such a high-Q qBIC, the figure of merit (FOM) of a biosensor is up to 18,908.7 RIU-1. Furthermore, we demonstrated that such a high-Q grating can help push the limit of optical biosensing to the single-particle level. Our results may find exciting applications in extreme biochemical sensing like COVID-19 with ultralow concentration.

3D printed microfluidic chip integrated with nanointerferometer for multiplex detection of foodborne pathogens

The current foodborne pathogen detection methods, such as culture-based methods, polymerase chain reaction, and optical and electrochemical biosensors with nucleic acid, have high sensitivity and selectivity. However, they are slow, expensive, and require well-trained operators. In this study, we utilized a 3D printer to develop a novel chip with an aptamer-based nanointerferometer capable of identifying four distinct foodborne pathogens: Listeria monocytogenes, Escherichia coli, Salmonella typhimurium, and Staphylococcus aureus. The aptamer sensor on the chip achieved a limit-of-detection of 10 colony forming unit (CFU)/ml. With its high sensitivity and specificity, this chip offers a cost-effective platform for distinguishing and screening different foodborne pathogens.

34‐4: A 270fps Large‐Area Organic Optical Biosensor Array for Digital Physiology and Vein Biometrics

This paper presents an optical biosensor system including a TFT (thin‐film transistor) sensor array and silicon IC to capture vein images, record PPG (photoplethysmography) signals and generate blood perfusion images. The sensing area is 1200 mm2 including 21168 pixels and SNR (signal‐to‐noise ratio) is 56 dB when FPS (frames per second) is 270.