Ultrasensitive detection of endocrine disruptors via superfine plasmonic spectral combs

Sandwich Layer-Modified Ω-Shaped Fiber-Optic LSPR Enables the Development of an Aptasensor for a Cytosensing-Photothermal Therapy Circuit

The metastasis of cancer cells is a principal cause of morbidity and mortality in cancer. The combination of a cytosensor and photothermal therapy (PTT) cannot completely eliminate cancer cells at one time. Hence, this study aimed to design a localized surface plasmonic resonance (LSPR)-based aptasensor for a circuit of cytosensing-PTT (COCP). This was achieved by coating a novel sandwich layer of polydopamine/gold nanoparticles/polydopamine (PDA/AuNPs/PDA) around the Ω-shaped fiber-optic (Ω-FO). The short-wavelength peak of the sandwich layer with strong resonance exhibited a high refractive index sensitivity (RIS). The modification with the T-shaped aptamer endowed FO-LSPR with unique characteristics of time-dependent sensitivity enhancement behavior for a sensitive cytosensor with the lowest limit of detection (LOD) of 13 cells/mL. The long-wavelength resonance peak in the sandwich layer appears in the near-infrared region. Hence, the rate of increased localized temperature of FO-LSPR was 160 and 30-fold higher than that of the bare and PDA-coated FO, indicating strong photothermal conversion efficiency. After considering the localized temperature distribution around the FO under the flow environment, the FO-LSPR-enabled aptasensor killed 77.6% of cancer cells in simulated blood circulation after five cycles of COCP. The FO-LSPR-enabled aptasensor improved the efficiency of the cytosensor and PTT to effectively kill cancer cells, showing significant potential for application in inhibiting cancer metastasis.

Ferroelectric Bi2O2Te-Based Plasmonic Biosensor for Ultrasensitive Biomolecular Detection

Ultrasensitive detection of biomarkers, particularly proteins, and microRNA, is critical for disease early diagnosis. Although surface plasmon resonance biosensors offer label-free, real-time detection, it is challenging to detect biomolecules at low concentrations that only induce a minor mass or refractive index change on the analyte molecules. Here an ultrasensitive plasmonic biosensor strategy is reported by utilizing the ferroelectric properties of Bi2O2Te as a sensitive-layer material. The polarization alteration of ferroelectric Bi2O2Te produces a significant plasmonic biosensing response, enabling the detection of charged biomolecules even at ultralow concentrations. An extraordinary ultralow detection limit of 1 fm is achieved for protein molecules and an unprecedented 0.1 fm for miRNA molecules, demonstrating exceptional specificity. The finding opens a promising avenue for the integration of 2D ferroelectric materials into plasmonic biosensors, with potential applications spanning a wide range.

Nano-Photonic Crystal D-Shaped Fiber Devices for Label-Free Biosensing at the Attomolar Limit of Detection

Maintaining both high sensitivity and large figure of merit (FoM) is crucial in regard to the performance of optical devices, particularly when they are intended for use as biosensors with extremely low limit of detection (LoD). Here, a stack of nano-assembled layers in the form of 1D photonic crystal, deposited on D-shaped single-mode fibers, is created to meet these criteria, resulting in the generation of Bloch surface wave resonances. The increase in the contrast between high and low refractive index (RI) nano-layers, along with the reduction of losses, enables not only to achieve high sensitivity, but also a narrowed resonance bandwidth, leading to a significant enhancement in the FoM. Preliminary testing for bulk RI sensitivity is carried out, and the effect of an additional nano-layer that mimics a biological layer where binding interactions occur is also considered. Finally, the biosensing capability is assessed by detecting immunoglobulin G in serum at very low concentrations, and a record LoD of 70 aM is achieved. An optical fiber biosensor that is capable of attaining extraordinarily low LoD in the attomolar range is not only a remarkable technical outcome, but can also be envisaged as a powerful tool for early diagnosis of diseases.

Estrogenic compounds in drinking water: A systematic review and risk analysis

Estrogenic compounds are the endocrine disruptors that receive major attention because of their ability to imitate the natural female hormone, 17β-estradiol and cause adverse effects on the reproductive system of animals. The presence of estrogenic compounds in drinking water is a warning to assess the risks to which human beings are exposed. The present work has the objectives of carrying out a systematic review of studies that investigated estrogenic compounds in drinking water around the world and estimate the human health and estrogenic activity risks, based on the concentrations of each compound reported. The systematic review returned 505 scientific papers from the Web of Science®, SCOPUS® and PubMED® databases and after careful analysis, 45 papers were accepted. Sixteen estrogenic compounds were identified in drinking water, from the classes of hormones, pharmaceutical drugs and personal care products, plasticizers, corrosion inhibitors, pesticides and surfactants. Di-(2-ethylhexyl) phthalate (DEHP) was the compound found at the highest concentration, reaching a value of 1.43 mg/L. Non-carcinogenic human health risk was classified as high for 17α-ethynilestradiol and DEHP, medium for dibutyl phthalate, and low for bisphenol A. The estrogenic activity risks were negligible for all the compounds, except DEHP, with a low risk. None of the estrogenic compounds presented an unacceptable carcinogenic risk, due to estrogenic activity. However, the risk assessment did not evaluate the interactions between compounds, that occurs in drinking water and can increase the risks and adverse effects to human health. Nonetheless, this study demonstrates the need for improvement of drinking water treatment plants, with more efficient technologies for micropollutant removal.

Ultrasensitive and Multiple Biomarker Discrimination for Alzheimer's Disease via Plasmonic & Microfluidic Sensing Technologies

As the population ages, the worldwide prevalence of Alzheimer's disease (AD) as the most common dementia in the elderly is increasing dramatically. However, a long-term challenge is to achieve rapid and accurate early diagnosis of AD by detecting hallmarks such as amyloid beta (Aβ42). Here, a multi-channel microfluidic-based plasmonic fiber-optic biosensing platform is established for simultaneous detection and differentiation of multiple AD biomarkers. The platform is based on a gold-coated, highly-tilted fiber Bragg grating (TFBG) and a custom-developed microfluidics. TFBG excites a high-density, narrow-cladding-mode spectral comb that overlaps with the broad absorption of surface plasmons for high-precision interrogation, enabling ultrasensitive monitoring of analytes. In situ detection and in-parallel discrimination of different forms of Aβ42 in cerebrospinal fluid (CSF) are successfully demonstrated with a detection of limit in the range of ≈30-170 pg mL-1, which is one order of magnitude below the clinical cut-off level in AD onset, providing high detection sensitivity for early diagnosis of AD. The integration of the TFBG sensor with multi-channel microfluidics enables simultaneous detection of multiple biomarkers using sub-µL sample volumes, as well as combining initial binding rate and real-time response time to differentiate between multiple biomarkers in terms of binding kinetics. With the advantages of multi-parameter, low consumption, and highly sensitive detection, the sensor represents an urgently needed potentials for large-scale diagnosis of diseases at early stage.

A group-targeting biosensor for sensitive and rapid detection of quinolones in water samples

BACKGROUND

Quinolones (QNs) widely exist in the environment due to their wide range of applications and poor metabolic properties, resulting in the generation and spread of resistance genes, posing a potential threat to human health. Traditional analytical methods cannot detect all broad ranges of QNs simultaneously. The development of facile, efficient and reliable method for quantification and assessment of the total QNs is a long-lasting challenge.

RESULTS

We hereby provide a simple, sensitive and instantaneous group-targeting biosensor for the detection of total QNs in environmental water samples. The biosensor is based on a group-specific antibodies with high affinity against QNs. Fluorescent labeled antibodies bound to the coated antigen modified on the surface of the transducer, and excited by the evanescent waves. The detected fluorescent signal is inversely proportional to the QNs concentration. This biosensor exhibited excellent performance with detection limits lower than 0.15 μg L-1 for all five QNs variants, and even lower than 0.075 μg L-1 for ciprofloxacin (CIP) and ofloxacin (OFL). Environmental water samples can be detected after simple pretreatment, and all detection steps can be completed in 10 min. The transducer has a high regenerative capacity and shows no significant signal degradation after two hundred detection cycles. The recoveries of QNs in a variety of wastewater range from 105 to 119%, confirming its application potential in the measurement of total QNs in reality.

SIGNIFICANCE

The biosensor can realize rapid and sensitive detection of total QNs in water samples by simple pretreatment, which overcomes the disadvantage of the traditional methods that require complex pretreatment and time-consuming, and pave the groundwork for expansive development centered around this technology.

Advancements in Battery Monitoring: Harnessing Fiber Grating Sensors for Enhanced Performance and Reliability

Batteries play a crucial role as energy storage devices across various industries. However, achieving high performance often comes at the cost of safety. Continuous monitoring is essential to ensure the safety and reliability of batteries. This paper investigates the advancements in battery monitoring technology, focusing on fiber Bragg gratings (FBGs). By examining the factors contributing to battery degradation and the principles of FBGs, this study discusses key aspects of FBG sensing, including mounting locations, monitoring targets, and their correlation with optical signals. While current FBG battery sensing can achieve high measurement accuracies for temperature (0.1 °C), strain (0.1 με), pressure (0.14 bar), and refractive index (6 × 10-5 RIU), with corresponding sensitivities of 40 pm/°C, 2.2 pm/με, -0.3 pm/bar, and -18 nm/RIU, respectively, accurately assessing battery health in real time remains a challenge. Traditional methods struggle to provide real-time and precise evaluations by analyzing the microstructure of battery materials or physical phenomena during chemical reactions. Therefore, by summarizing the current state of FBG battery sensing research, it is evident that monitoring battery material properties (e.g., refractive index and gas properties) through FBGs offers a promising solution for real-time and accurate battery health assessment. This paper also delves into the obstacles of battery monitoring, such as standardizing the FBG encapsulation process, decoupling multiple parameters, and controlling costs. Ultimately, the paper highlights the potential of FBG monitoring technology in driving advancements in battery development.

All-fiber label-free optical fiber biosensors: from modern technologies to current applications [Invited]

Biosensors are established as promising analytical tools for detecting various analytes important in biomedicine and environmental monitoring. Using fiber optic technology as a sensing element in biosensors offers low cost, high sensitivity, chemical inertness, and immunity to electromagnetic interference. Optical fiber sensors can be used in in vivo applications and multiplexed to detect several targets simultaneously. Certain configurations of optical fiber technology allow the detection of analytes in a label-free manner. This review aims to discuss recent advances in label-free optical fiber biosensors from a technological and application standpoint. First, modern technologies used to build label-free optical fiber-based sensors will be discussed. Then, current applications where these technologies are applied are elucidated. Namely, examples of detecting soluble cancer biomarkers, hormones, viruses, bacteria, and cells are presented.

In situ surface turbidity sensor based on localized light scattering from tilted fiber Bragg gratings

We propose a compact fiber-optic sensor for in situ and continuous turbidity monitoring, based on surface optical scattering of polarized evanescent waves from targeted particles. The sensor is composed of a tilted fiber Bragg grating (TFBG) packaged inside a microfluidic capillary. The transmission spectrum of the TFBG provides a fine comb of narrow cladding resonances that are highly sensitive to the turbidity due to the localized light scattering of polarized evanescent waves from the microparticles near the fiber surface (as opposed to traditional bulk/volumetric turbidity measurement). We also propose a transmission spectral area interrogation method and quantify the repeatable correlation between the surface turbidity and the optical spectral area response. We show that the maximum sensitive turbidity response is achieved when the wavelength of the sensing cladding resonance matches the size of surrounding solid particles.

Recent Advances in Real-Time Label-Free Detection of Small Molecules

The detection and analysis of small molecules, typically defined as molecules under 1000 Da, is of growing interest ranging from the development of small-molecule drugs and inhibitors to the sensing of toxins and biomarkers. However, due to challenges such as their small size and low mass, many biosensing technologies struggle to have the sensitivity and selectivity for the detection of small molecules. Notably, their small size limits the usage of labeled techniques that can change the properties of small-molecule analytes. Furthermore, the capability of real-time detection is highly desired for small-molecule biosensors' application in diagnostics or screening. This review highlights recent advances in label-free real-time biosensing technologies utilizing different types of transducers to meet the growing demand for small-molecule detection.

Operando monitoring of dendrite formation in lithium metal batteries via ultrasensitive tilted fiber Bragg grating sensors

Lithium (Li) dendrite growth significantly deteriorates the performance and shortens the operation life of lithium metal batteries. Capturing the intricate dynamics of surface localized and rapid mass transport at the electrolyte-electrode interface of lithium metal is essential for the understanding of the dendrite growth process, and the evaluation of the solutions mitigating the dendrite growth issue. Here we demonstrate an approach based on an ultrasensitive tilted fiber Bragg grating (TFBG) sensor which is inserted close to the electrode surface in a working lithium metal battery, without disturbing its operation. Thanks to the superfine optical resonances of the TFBG, in situ and rapid monitoring of mass transport kinetics and lithium dendrite growth at the nanoscale interface of lithium anodes have been achieved. Reliable correlations between the performance of different natural/artificial solid electrolyte interphases (SEIs) and the time-resolved optical responses have been observed and quantified, enabling us to link the nanoscale ion and SEI behavior with the macroscopic battery performance. This new operando tool will provide additional capabilities for parametrization of the batteries' electrochemistry and help identify the optimal interphases of lithium metal batteries to enhance battery performance and its safety.

Rapid ultra-sensitive nucleic acid detection using plasmonic fiber-optic spectral combs and gold nanoparticle-tagged targets

Nucleic acid (NA) is a widely-used biomarker for viruses. Accurate quantification of NA can provide a reliable basis for point-of-care diagnosis and treatment. Here, we propose a tilted fiber Bragg grating (TFBG)-based plasmonic fiber-optic spectral comb for fast response and ultralow limit NA detection. The TFBG is coated with a gold film which enables excitation of surface plasmon resonance (SPR), and single-stranded probe NAs with known base sequences are assembled on the gold film. To enhance sensitivity of refractive index (RI) for sensing a chosen combination of probe and target NAs around the TFBG surface, gold nanoparticles (AuNPs) are bonded to the target NA molecules as "RI-labels". The NA combination-induced aggregation of AuNPs induces significant spectral responses in the TFBG that would be below the detection threshold for the NAs in the absence of the AuNPs. The proposed TFBG-SPR NA sensor shows a fast response time of 30 s and an ultra-wide NA detection range from 1 × 10-18 mol/L to 1 × 10-7 mol/L. In the NA concentration range of 1 × 10-12 mol/L (1 pM) to 105 pM, an ultra-high sensitivity of 1.534 dB/lg(pM) is obtained. The sensor achieves an ultra-low limit of detection down to 1.0 × 10-18 mol/L (1 aM), which is more than an order of magnitude lower than the previous reports. The proposed sensor not only shows potentials in practical applications of NA detection, but also provides a new way for TFBG-SPR biochemical sensors to achieve higher RI sensitivity.

Surface plasmonic biosensors: principles, designs and applications

Recently, surface plasmon resonance (SPR) biosensors have been widely used in environmental monitoring, food contamination detection and diagnosing medical conditions due to their superior sensitivity, label-free detection and rapid analysis speed. This paper briefly elaborates on the development history of SPR technology and introduces SPR signal sensing principles. A summary of recent applications of SPR sensors in different fields is highlighted, including their figures of merit and limitations. Finally, the personal perspectives and future development trends about sensor preparation and design are discussed in detail, which may be critical for improving the performance of SPR sensors.

An Ultrasensitive SPR biosensor for RNA detection based on robust GeP5 nanosheets

Ultrasensitive and rapid detection of biomarkers is among the upmost priorities in promoting healthcare advancements. Improved sensitivity of photonic sensors based on two-dimensional (2D) materials have brought exciting prospects for achieving real-time and label-free biosensing at dilute target concentrations. Here, we report a high-sensitivity surface plasmon resonance (SPR) RNA sensor using metallic 2D GeP5 nanosheets as the sensing material. Theoretical evaluations revealed that the presence of GeP5 nanosheets can greatly enhance the plasmonic electric field of the Au film thereby boosting sensing sensitivity, and that optimal sensitivity (146° RIU-1) can be achieved with 3-nm-thick GeP5. By functionalizing GeP5 nanosheets with specific cDNA probes, detection of SARS-CoV-2 RNA sequences were achieved using the GeP5-based SPR sensor, with high sensitivity down to a detection limit of 10 aM and excellent selectivity. This work demonstrates the immense potential of GeP5-based SPR sensors for advanced biosensing applications and paves the way for utilizing GeP5 nanosheets in novel sensor devices.

NY-ESO-1 antigen-antibody interaction process based on an TFBG plasmonic sensor

Autoantibodies against New York esophageal squamous cell cancer 1 (NY-ESO-1) play a crucial role in the diagnosis of esophageal cancer. In this work, a surface plasmonic tilted fiber Bragg grating (TFBG) biosensor is proposed for the detection of NY-ESO-1 antibody, as well as the investigation of the hook effect (which refers to the false negative result in some immunoassays when the concentration of antibodies in the sample is very high) during biomolecular binding between NY-ESO-1 antigen and antibody. The biosensor is made by an 18° TFBG coated with a 50-nm-thick gold film over the fiber surface together with NY-ESO-1 antigens attached to the metallic surface serving as bio-receptors. This biosensor can provide a limit of detection at a concentration of 2 × 10-7 µg/ml with a good linearity in the range from 2 × 10-7 to 2 × 10-5 µg/ml. For a concentration higher than 2 × 10-3 µg/ml, the performance of the sensor probe is reduced owing to the hook effect. Furthermore, experimental results have also demonstrated the repeatability of the proposed biosensor. This proposed biosensor features label-free, compactness, and fast response, which could be potentially applied in the diagnosis of esophageal cancer.

Effect-Targeted Mapping of Potential Estrogenic Agonists and Antagonists in Wastewater via a Conformation-Specific Reporter-Mediated Biosensor

Wastewater treatment plants (WWTPs) are regarded as the main sources of estrogens that reach the aquatic environment. Hence, continuous monitoring of potential estrogenic-active compounds by a biosensor is an appealing approach. However, existing biosensors cannot simultaneously distinguish and quantify estrogenic agonists and antagonists. To overcome the challenge, we developed an estrogen receptor-based biosensor that selectively screened estrogenic agonists and antagonists by introducing rationally designed agonist/antagonist conformation-specific reporters. The double functional conformation-specific reporters consist of a Cy5.5-labeled streptavidin moiety and a peptide moiety, serving as signal recognition and signal transduction elements. In addition, the conformation recognition mechanism was further validated at the molecular level through molecular docking. Based on the two-step "turn-off" strategy, the biosensor exhibited remarkable sensitivity, detecting 17β-estradiol-binding activity equivalent (E2-BAE) at 7 ng/L and 4-hydroxytamoxifen-binding activity equivalent (4-OHT-BAE) at 91 ng/L. To validate its practicality, the biosensor was employed in a case study involving wastewater samples from two full-scale WWTPs across different treatment stages to map their estrogenic agonist and antagonist binding activities. Comparison with the yeast two-hybrid bioassay showed a strong liner relationship (r2 = 0.991, p < 0.0001), indicating the excellent accuracy and reliability of this technology in real applications.

Highly sensitive, modification-free, and dynamic real-time stereo-optical immuno-sensor

Modification-free biosensing with high specificity and sensitivity is essential for miniaturized, online, integrated, and rapid, or even real-time molecular analyses. However, most optical biosensors are based on surface pre-modification or fluorescent labeling, and have either low sensitivity or low quality factor (Q). To address these difficulties, in this study, an optical sensor prototype was developed with a microbubble optofluidic channel integrated inside a Fabry-Pérot cavity to three-dimensionally tailor the intra-cavity light field via the intra-cavity lensing (microbubble) configuration. A high Q-factor (∼105), small mode volume, and high light energy density were experimentally achieved with this "stereo-sensor" while maintaining an ultrahigh refractive index (RI) sensitivity (679 nm/RIU) and ultra-small RI resolution (∼10-7 RIU at 950 nm). Moreover, specific detection of very low concentration of biomolecules (5 fg/mL for human IgG and 0.5 pg/mL for human serum albumin (HSA)) and wide range of protein concentrations (e.g., fg/mL-ng/mL for human IgG and pg/mL-ng/mL for HSA) without probe pre-modification were achieved owing to the RI change specifically associated with the probe-target binding and the corresponding bio-macromolecular conformation change. This modification-free stereosensing scenario is applicable to continuous, real-time, and multiplexed operations, thus showing potential for online, integrated, dynamic, biomolecular analyses in vitro or in vivo, such as the dynamic metabolic analysis of single cells or organoids and point-of-care tests.

Hot-Electron Dynamics Mediated Medical Diagnosis and Therapy

Surface plasmon resonance excitation significantly enhances the absorption of light and increases the generation of "hot" electrons, i.e., conducting electrons that are raised from their steady states to excited states. These excited electrons rapidly decay and equilibrate via radiative and nonradiative damping over several hundred femtoseconds. During the hot-electron dynamics, from their generation to the ultimate nonradiative decay, the electromagnetic field enhancement, hot electron density increase, and local heating effect are sequentially induced. Over the past decade, these physical phenomena have attracted considerable attention in the biomedical field, e.g., the rapid and accurate identification of biomolecules, precise synthesis and release of drugs, and elimination of tumors. This review highlights the recent developments in the application of hot-electron dynamics in medical diagnosis and therapy, particularly fully integrated device techniques with good application prospects. In addition, we discuss the latest experimental and theoretical studies of underlying mechanisms. From a practical standpoint, the pioneering modeling analyses and quantitative measurements in the extreme near field are summarized to illustrate the quantification of hot-electron dynamics. Finally, the prospects and remaining challenges associated with biomedical engineering based on hot-electron dynamics are presented.

Rapid and sensitive detection of aqueous ammonia harnessing nanocomposite functionalized tilted fiber Bragg grating

A high sensitive aqueous ammonia sensor based on tilted fiber Bragg grating (TFBG) had been reported. The sensors were fabricated by a 10 ° TFBG coated by a membrane receptor named as Polyaniline/Graphene oxide on the surface of the fiber. The correlative concentrations of aqueous ammonia were demodulated by global monitoring of the envelope area of cladding modes in the transmitted spectrum of the TFBG. Tests have shown that the proposed sensor can provide a linear and rapid response of aqueous ammonia within 22 seconds, in a concentration range from 1-12 ppm. Moreover, the limit of detection can even reach 0.08 ppm, through the theoretical analysis of our experimental results. The proposed sensor has good performance, is easy to manufacture and of small size, making it a good choice for real-time, in-situ, label-free detection of aqueous ammonia in the future.

Spatially Modulated Fiber Speckle for High-Sensitivity Refractive Index Sensing

A fiber speckle sensor (FSS) based on a tapered multimode fiber (TMMF) has been developed to measure liquid analyte refractive index (RI) in this work. By the lateral and axial offset of input light into TMMF, several high-order modes are excited in TMMF, and the speckle pattern is spatially modulated, which affects an asymmetrical speckle pattern with a random intensity distribution at the output of TMMF. When the TMMF is immersed in the liquid analyte with RI variation, it influences the guided modes, as well as the mode interference, in TMMF. A digital image correlations method with zero-mean normalized cross-correlation coefficient is explored to digitize the speckle image differences, analyzing the RI variation. It is found that the lateral- and axial-offsets-induced speckle sensor can enhance the RI sensitivity from 6.41 to 19.52 RIU-1 compared to the one without offset. The developed TMMF speckle sensor shows an RI resolution of 5.84 × 10-5 over a linear response range of 1.3164 to 1.3588 at 1550 nm. The experimental results indicate the FSS provides a simple, efficient, and economic approach to RI sensing, which exhibits an enormous potential in the image-based ocean-sensing application.

Early and Sensitive Detection of Pathogens for Public Health and Biosafety: An Example of Surveillance and Genotyping of SARS-CoV-2 in Sewage Water by Cas12a-Facilitated Portable Plasmonic Biosensor

Infectious diseases severely threaten public health and global biosafety. In addition to transmission through the air, pathogenic microorganisms have also been detected in environmental liquid samples, such as sewage water. Conventional biochemical detection methodologies are time-consuming and cost-ineffective, and their detection limits hinder early diagnosis. In the present study, ultrafine plasmonic fiber probes with a diameter of 125 μm are fabricated for clustered regularly interspaced short palindromic repeats/CRISPR-associated protein (CRISPR/Cas)-12a-mediated sensing of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Single-stranded DNA exposed on the fiber surface is trans-cleaved by the Cas12a enzyme to release gold nanoparticles that are immobilized onto the fiber surface, causing a sharp reduction in the surface plasmon resonance (SPR) wavelength. The proposed fiber probe is virus-specific with the limit of detection of ~2,300 copies/ml, and genomic copy numbers can be reflected as shifts in wavelengths. A total of 21 sewage water samples have been examined, and the data obtained are consistent with those of quantitative polymerase chain reaction (qPCR). In addition, the Omicron variant and its mutation sites have been fast detected using S gene-specific Cas12a. This study provides an accurate and convenient approach for the real-time surveillance of microbial contamination in sewage water.

Ultra-sensitive specific detection of nucleic acids in pathogenic infections by Ta2C-MXene sensitization-based ultrafine plasmon spectroscopy combs

Accurate and rapid population-scale screening techniques based on SARS-CoV-2 RNA are essential in preventing and controlling the COVID-19 epidemic. However, the sensitivity and specificity of the assay signal are challenged by the problems of target dilution and sample contamination inherent in high-volume pooled testing. Here, we reported a collaborative system of high-loaded hybrid probes targeting N and OFR1a coupling with the novel Ta₂C-M/Au/TFBG biosensor, providing high-intensity vector signals for detecting SARS-CoV-2. The method relies on a segmental modification approach to saturable modify multiple activation sites of SARS-CoV-2 on the high-performance Ta₂C-M surface. The coupling of multi-site synergy with composite excited TFBG results in excellent signal transduction, detection limits (0.2 pg/mL), and hybridization efficiency. Without relying on amplification, the collaborative system achieved specific differentiation of 30 clinical samples in an average diagnostic time of 1.8 min. In addition, for the first time, a kinetic determination of dilution mixed samples was achieved and showed a high-intensity carrier signal and fantastic stability. Therefore, it can be used as a collaborative, integrated tool to play a massive role in the screening, prevention, and control of COVID-19 and other epidemics.

Ultrasensitive and Specific Clustered Regularly Interspaced Short Palindromic Repeats Empowered a Plasmonic Fiber Tip System for Amplification-Free Monkeypox Virus Detection and Genotyping

The urgent necessity for highly sensitive diagnostic tools has been accentuated by the ongoing mpox (monkeypox) virus pandemic due to the complexity in identifying asymptomatic and presymptomatic carriers. Traditional polymerase chain reaction-based tests, despite their effectiveness, are hampered by limited specificity, expensive and bulky equipment, labor-intensive operations, and time-consuming procedures. In this study, we present a clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a-based diagnostic platform with a surface plasmon resonance-based fiber tip (CRISPR-SPR-FT) biosensor. The compact CRISPR-SPR-FT biosensor, with a 125 μm diameter, offers high stability and portability, enabling exceptional specificity for mpox diagnosis and precise identification of samples with a fatal mutation site (L108F) in the F8L gene. The CRISPR-SPR-FT system can analyze viral double-stranded DNA from mpox virus without amplification in under 1.5 h with a limit of detection below 5 aM in plasmids and about 59.5 copies/μL when in pseudovirus-spiked blood samples. Our CRISPR-SPR-FT biosensor thus offers fast, sensitive, portable, and accurate target nucleic acid sequence detection.

Polarization-independent tilted fiber Bragg grating surface plasmon resonance sensor based on spectrum optimization

We experimentally demonstrated polarization multiplexing schemes in a tilted fiber grating (TFBG) to achieve polarization-independent fiber-optic surface plasmon resonance (SPR) sensors. The first used two orthogonal polarized lights separated by a polarization beam splitter (PBS) that are p-polarized in polarization-maintaining fiber (PMF) and precisely aligned with the tilted grating plane, so as to achieve the transmission of p-polarized light in two opposite directions of the Au-coated TFBG to excite SPR. Alternatively, polarization multiplexing was also achieved by exploring two polarization components to achieve the SPR effect through a Faraday rotator mirror (FRM). The SPR reflection spectra are polarization-independent of the light source and any perturbations to fibers, which are explained by the superposition of p- and s-polarized transmission spectra in equal proportions. The spectrum optimization is presented to reduce the proportion of the s-polarization component. A polarization-independent TFBG-based SPR refractive index (RI) sensor with a wavelength sensitivity of 555.14 nm/RIU and an amplitude sensitivity of 1724.92 dB/RIU for small changes is obtained, exhibiting unique advantages of minimizing the polarization alterations by mechanical perturbations.

Fiber Bragg gratings inscribed in nanobore fibers

The nanobore fiber (NBF) is a promising nanoscale optofluidic platform due to its long nanochannel and unique optical properties. However, so far, the applications of NBF have been based only on its original fiber geometry without any extra functionalities, in contrast with various telecom fiber devices, which may limit its wide applications. Here, we provide the first, to the best of our knowledge, demonstration of NBF-based fiber Bragg gratings (FBGs) introduced by either the femtosecond (fs) laser direct writing technique or the ultraviolet (UV) laser phase mask technique. Moreover, the FBG fabricated via the UV laser was optimized, achieving a high reflectivity of 96.89% and simultaneously preserving the open nanochannel. The NBF-based FBGs were characterized in terms of temperature variation and the infiltration of different liquids, and they showed high potential for nanofluidic applications.

Two-dimensional material-enhanced surface plasmon resonance for antibiotic sensing

Two-dimensional (2D) materials attract attention from the academic community due to their excellent properties, and their wide application in sensing is expected to revolutionize environmental monitoring, medical diagnostics, and food safety. In this work, we systematically evaluate the effects of 2D materials on the Au chip surface plasmon resonance (SPR) sensor. The results reveal that 2D materials cannot improve the sensitivity of intensity-modulated SPR sensors. However, there exists an optimal real part of RI of 3.5-4.0 and optimal thickness when choosing nanomaterials for sensitivity enhancement of SPR sensors in angular modulation. In addition, the smaller the imaginary part of the nanomaterial RI, the higher the sensitivity of the proposed Au SPR sensor. The 2D material's thickness needed for the highest sensitivity decreases with increasing real part and imaginary part of the RI. As a case study, we developed a 5 nm-thickness MoS₂-enhanced SPR biosensor, which exhibited a low sulfonamides (SAs) detection limit of 0.05 μg/L based on a group-targeting indirect competitive immunoassay, nearly 12-fold lower than that of the bare Au SPR system. The proposed criteria help to shed light on the 2D material-Au surface interaction, which has greatly promoted the development of novel SPR biosensing with outstanding sensitivity.

Distributed optical fiber biosensor based on optical frequency domain reflectometry

In situ acquisition of spatial distribution of biochemical substances is important in cell analysis, cancer detection and other fields. Optical fiber biosensors can achieve label-free, fast and accurate measurements. However, current optical fiber biosensors only acquire single-point of biochemical substance content. In this paper, we present a distributed optical fiber biosensor based on tapered fiber in optical frequency domain reflectometry (OFDR) for the first time. To enhance evanescent field at a relative long sensing range, we fabricate a tapered fiber with a taper waist diameter of 6 μm and a total stretching length of 140 mm. Then the human IgG layer is coated on the entire tapered region by polydopamine (PDA) -assisted immobilization as the sensing element to achieve to sense anti-human IgG. We measure shifts of the local Rayleigh backscattering spectra (RBS) caused by the refractive index (RI) change of an external medium surrounding a tapered fiber after immunoaffinity interactions by using OFDR. The measurable concentration of anti-human IgG and RBS shift has an excellent linearity in a range from 0 ng/ml to 14 ng/ml with an effective sensing range of 50 mm. The concentration measurement limit of the proposed distributed biosensor is 2 ng/ml for anti-human IgG. Distributed biosensing based on OFDR can locate a concentration change of anti-human IgG with an ultra-high sensing spatial resolution of 680 μm. The proposed sensor has a potential to realize a micron-level localization of biochemical substances such as cancer cells, which will open a door to transform single-point biosensor to distributed biosensor.

Ultra-sensitive and specific detection of pathogenic nucleic acids using composite-excited hyperfine plasma spectroscopy combs sensitized by Au nanoarrays functionalized with 2D Ta2C-MXene

Accurate and rapid screening techniques on a population scale are crucial for preventing and managing epidemics like COVID-19. The standard gold test for nucleic acids in pathogenic infections is primarily the reverse transcription polymerase chain reaction (RT-PCR). However, this method is not suitable for widespread screening due to its reliance on large-scale equipment and time-consuming extraction and amplification processes. Here, we developed a collaborative system that combines high-load hybridization probes targeting N and OFR1a with Au NPs@Ta₂C-M modified gold-coated tilted fiber Bragg grating (TFBG) sensors to enable direct nucleic acid detection. Multiple activation sites of SARS-CoV-2 were saturable modified on the surface of a homogeneous arrayed AuNPs@Ta₂C-M/Au structure based on a segmental modification approach. The combination of hybrid probe synergy and composite polarisation response in the excitation structure results in highly specific hybridization analysis and excellent signal transduction of trace target sequences. The system demonstrates excellent trace specificity, with a limit of detection of 0.2 pg/mL, and achieves a rapid response time of 1.5 min for clinical samples without amplification. The results showed high agreement with the RT-PCR test (Kappa index = 1). And the gradient-based detection of 10-in-1 mixed samples exhibits high-intensity interference immunity and excellent trace identification. Therefore, the proposed synergistic detection platform has a good tendency to curb the global spread of epidemics such as COVID-19.

Estradiol Detection for Aquaculture Exploiting Plasmonic Spoon-Shaped Biosensors

In this work, a surface plasmon resonance (SPR) biosensor based on a spoon-shaped waveguide combined with an estrogen receptor (ERα) was developed and characterized for the detection and the quantification of estradiol in real water samples. The fabrication process for realizing the SPR platform required a single step consisting of metal deposition on the surface of a polystyrene spoon-shaped waveguide featuring a built-in measuring cell. The biosensor was achieved by functionalizing the bowl sensitive surface with a specific estrogen receptor (ERα) that was able to bind the estradiol. In a first phase, the biosensor tests were performed in a phosphate buffer solution obtaining a limit of detection (LOD) equal to 0.1 pM. Then, in order to evaluate the biosensor's response in different real matrices related to aquaculture, its performances were examined in seawater and freshwater. The experimental results support the possibility of using the ERα-based biosensor for the screening of estradiol in both matrices.

Optical Biosensors and Their Applications for the Detection of Water Pollutants

The correct detection and quantification of pollutants in water is key to regulating their presence in the environment. Biosensors offer several advantages, such as minimal sample preparation, short measurement times, high specificity and sensibility and low detection limits. The purpose of this review is to explore the different types of optical biosensors, focusing on their biological elements and their principle of operation, as well as recent applications in the detection of pollutants in water. According to our literature review, 33% of the publications used fluorescence-based biosensors, followed by surface plasmon resonance (SPR) with 28%. So far, SPR biosensors have achieved the best results in terms of detection limits. Although less common (22%), interferometers and resonators (4%) are also highly promising due to the low detection limits that can be reached using these techniques. In terms of biological recognition elements, 43% of the published works focused on antibodies due to their high affinity and stability, although they could be replaced with molecularly imprinted polymers. This review offers a unique compilation of the most recent work in the specific area of optical biosensing for water monitoring, focusing on both the biological element and the transducer used, as well as the type of target contaminant. Recent technological advances are discussed.

Group-targeting sulfonamides via an evanescent-wave biosensor based on rational designed coating antigen

In order to effectively monitor a wide variety of sulfonamides residues in the environment, group-targeting immunoassay based on the group-specific antibodies has attracted great attentions, which can realize the detection of a group of contaminants in environment as many as possible even the unrecognized ones. Indirect competitive immunoassay is generally adopted for small molecule detection however the rational design of immobilized coating antigen for improved recognition capability on the solid surface is far from enough. To cover the research gap, we proposed the design criteria of coating antigen for surface-based indirect competitive immunoassay based on the molecular docking. Taking the group-specific antibodies against sulfonamides (SA) as a proof-of-concept, a hapten with a linking arm with 3 methyl groups was selected to synthesize the coating antigen. Through surface immobilization of coating antigen, a portable biosensor for group-targeting immunoassay of sulfonamides was developed and demonstrated excellent performance with detection limits lower than 0.6 μg/L for four SA variants, and the cross-reactivities of 148-215 % relative to sulfadiazine. The recovery rates of SAs in liquid milk ranges from 87 to 97 %, which confirmed the application potential of this method in the determination of SAs. Its capability to measure total SAs in a simple and low-cost way would pave the way for a variety of application fields.

Plasmonic Biosensors with Nanostructure for Healthcare Monitoring and Diseases Diagnosis

Nanophotonics has been widely utilized in enhanced molecularspectroscopy or mediated chemical reaction, which has major applications in the field of enhancing sensing and enables opportunities in developing healthcare monitoring. This review presents an updated overview of the recent exciting advances of plasmonic biosensors in the healthcare area. Manufacturing, enhancements and applications of plasmonic biosensors are discussed, with particular focus on nanolisted main preparation methods of various nanostructures, such as chemical synthesis, lithography, nanosphere lithography, nanoimprint lithography, etc., and describing their respective advances and challenges from practical applications of plasmon biosensors. Based on these sensing structures, different types of plasmonic biosensors are summarized regarding detecting cancer biomarkers, body fluid, temperature, gas and COVID-19. Last, the existing challenges and prospects of plasmonic biosensors combined with machine learning, mega data analysis and prediction are surveyed.

Screening of Endocrine Disrupting Potential of Surface Waters via an Affinity-Based Biosensor in a Rural Community in the Yellow River Basin, China

Overcoming the limitations of traditional analytical methods and developing technologies to continuously monitor environments and produce a comprehensive picture of potential endocrine-disrupting chemicals (EDCs) has been an ongoing challenge. Herein, we developed a portable nuclear receptor (NR)-based biosensor within 90 min to perform highly sensitive analyses of a broad range of EDCs in environmental water samples. Based on the specific binding of the fluorescence-labeled NRs with their ligands, the receptors were attached to the EDC-functionalized fiber surface by competing with EDCs in the samples. The biosensor emitted fluorescence due to the evanescent wave excitation, thereby resulting in a turn-off sensing mode. The biosensor showed a detection limit of 5 ng/L E₂-binding activity equivalent (E₂-BAE) and 93 ng/L T₃-BAE. As a case study, the biosensor was used to map the estrogenic binding activities of surface waters obtained from a rural community in the Yellow River basin in China. When the results obtained were compared with those from the traditional yeast two-hybrid bioassay, a high correlation was observed. It is anticipated that the good universality and versatility exhibited by this biosensor for various EDCs, which is achieved by using different NRs, will significantly promote the continuous assessment of global EDCs.

Fluorescence switchable sensor enabled by a calix[4]arene-Cu(II) complex system for selective determination of itraconazole in human serum and aqueous solution

A switchable fluorescence sensor based on a calix (Monapathi et al., 2021) [4]arene:Cu²⁺ complex (FLCX/Cu) has been developed for the detection of itraconazole (ITZ) with high sensitivity and specificity. For the development of the sensor, the selective complexation of a fluorescent calix (Monapathi et al., 2021) [4]arene derivative (FL-CX) with the Cu²⁺ ion causing fluorescence quenching was utilized. In addition, the sensor properties of the FLCX/Cu prepared were investigated. For this purpose, various substances (selected anions, cations, and drugs) with which ITZ can be found together were studied in an aqueous solution. Limit of detection (LOD) and limit of quantification (LOQ) values were determined in the range of 1.00-60.0 μg/L as 3.34 μg/L and 11.1 μg/L for ITZ, respectively. Moreover, the real sample analyses were performed in human serum and tablet form. Furthermore, the effect of some possible serum contents on sensor performance was also studied. All these studies confirmed the development of a simple, precise, accurate, reproducible, highly sensitive, and very stable fluorescence sensor.

Fiber SPR two-dimensional micro displacement sensor based on the coaxial double waveguide with a conical structure

Fiber SPR micro displacement sensor cannot be used for two-dimensional displacement sensing at present. In this paper, we proposed and demonstrated a fiber SPR two-dimensional micro displacement sensor based on the coaxial double waveguide with a conical structure. The coaxial double waveguide is fused into a cone as the light injection fiber, and two different forms of outgoing light fields can be obtained through two cores of the fiber. The horn shaped light field emitted by the ring core of the coaxial double waveguide can cooperate with the sensing fiber to realize the micro displacement sensing in the x-axis direction. And the straight beam emitted by the middle core of the coaxial double waveguide can cooperate with the sensing fiber to realize the micro displacement sensing in the y-axis direction. Through simulation analysis and experimental test, its average wavelength sensitivity and light intensity sensitivity of the x-axis displacement are 0.0537nm/µm and 0.000124a.u./µm, respectively. And that of the y-axis displacement are 0.315nm/µm and 0.00277a.u./µm, respectively. The proposed fiber sensor realizes the two-dimensional displacement sensing based on SPR, which can be widely used in the fields of two-dimensional micro displacement measurement and two-dimensional position precision positioning.

Thermal-mechanical-photo-activation effect on silica micro/nanofiber surfaces: origination, reparation and utilization

The exploration relevant to the surface changes on optical micro- and nanofibers (MNFs) is still in infancy, and the reported original mechanisms remain long-standing puzzles. Here, by recognizing the combined interactions between fiber heating, mechanically tapering, and high-power pulsed laser guiding processes in MNFs, we establish a general thermal-mechanical-photo-activation mechanism that can explain the surface changes on MNFs. Our proposed activation mechanism can be well supported by the systematical experimental results using high-intensity nanosecond/femtosecond pulsed lasers. Especially we find large bump-like nanoscale cavities on the fracture ends of thin MNFs. Theoretically, on the basis of greatly increased bond energy activated by the fiber heating and mechanically tapering processes, the energy needed to break the silicon-oxygen bond into dangling bonds is significantly reduced from its intrinsic bandgap of ∼9 eV to as low as ∼4.0 eV, thus high-power pulsed lasers with much smaller photon energy can induce obvious surface changes on MNFs via multi-photon absorption. Finally, we demonstrate that using surfactants can repair the MNF surfaces and exploit them in promising applications ranging from sensing and optoelectronics to nonlinear optics. Our results pave the way for future preventing the performances from degradation and enabling the practical MNF-based device applications.

Simultaneous Electrochemical Determination of Chlorzoxazone and Diclofenac on an Efficient Modified Glassy Carbon Electrode by Lanthanum Oxide@ Copper(I) Sulfide Composite

This study synthesized a La2O3@snowflake-like Cu2S composite to fabricate an electrochemical sensor for sensitively simultaneous detection of diclofenac and chlorzoxazone exploiting an easy hydrothermal approach, followed by analysis with XRD, FE-SEM, and EDX methods. According to voltammetric studies, the electrocatalytic diclofenac and chlorzoxazone oxidations on the electrode modified with La2O3@SF-L Cu2S composites were increased, with greater oxidation currents, as well as the oxidation potential was significantly decreased due to synergetic impact of La2O3@SF-L Cu2S composites when compared with the pure SF-L Cu2S NS-modified electrode. The differential pulse voltammetry findings showed wide straight lines (0.01–900.0 μM) for La2O3 NP@SF-L Cu2S NS-modified electrode with a limit of detection (LOD) of 1.7 and 2.3 nM for the detection of diclofenac and chlorzoxazone, respectively. In addition, the limit of quantification was calculated to be 5.7 and 7.6 nM for diclofenac and chlorzoxazone, respectively. The diffusion coefficient was calculated to be 1.16 × 10−5and 8.4 × 10−6 cm2/s for diclofenac and chlorzoxazone oxidation on the modified electrode, respectively. Our proposed electrode was examined for applicability by detecting diclofenac and chlorzoxazone in real specimens.

Electrochemical monitoring sensors of water pollution systems

Analytical techniques as strong, precise, and expensive are necessary for monitoring food and water safety for contaminants, microorganisms, and allergies that might be harmful if used. Sudan dyes are commonly utilized as an ingredient in food dye substances and a variety of industrial items. These colors are classified as three carcinogens and are linked to liver and bladder cancers. They are not authorized for human consumption by the International Agency for Research on Cancer (IARC) and are not permitted to be used by the Food Standards Agency or the European Union. This article describes electrochemical dye analysis beside the numerous electrochemical sensors utilized to identify these dyes as a food colorant and water. As a result, the qualities, chemistry, and toxicity of dyes as food colorants and industrial goods in Sudan have been investigated in this study. Sudan dyes have been thoroughly studied, and many electrochemical sensors have been developed to define and monitor these dyes in food colorants. As a result, current electrochemical sensors have been found to be neither mass-production nor cost-effective. Mostly, the synthesis of high-performance materials needs high knowledge, and the production of electrode surfaces is remained difficult due to labor-intensive and time-consuming activities.

Shedding light on biology and healthcare-preface to the special issue on Biomedical Optics

This special issue collects 20 excellent papers, spanning NIR II imaging, high-speed imaging, adaptive wavefront shaping, label-free imaging, ultrasensitive detection, polarization optics, photodynamic therapy, and preclinical applications. [Image: see text]

B24N24 nanocage as an electronic sensor for metronidazole drug: density functional theory studies

This paper implemented the density functional theory (DFT) to evaluate a nano-structured sensor of the metronidazole (ML) drug based on the interaction between pristine B₂₄N₂₄ nanocage and the drug. Chemisorption (adsorption energy = - 13.77 to - 15.11 kcal/mol) and physisorption (= - 1.48 to - 4.97 kcal/mol) were estimated to be potential mechanisms of adsorption. The substantial rise in the electrical conductivity of B₂₄N₂₄ suggested that the nanocage was capable of generating electronic noise in interaction with the drug. In addition, the adsorption of the drug significantly influenced the work function, Fermi level, and complexes (chemisorption) of the highest stability. This suggests that one can detect ML through the Φ-type nano-sensing efficiency of B₂₄N₂₄. The recovery process takes nearly 0.005 s, and it was observed that bare B₂₄N₂₄ nanocages could be employed without costly manipulations of the structure for sensitivity improvement. The UV-Vis results indicated that ML adsorption upshifted the transmission wavelength at 391.07 nm. Thus, the close distance of the drug molecule from the nanocage led to the redshift. It was concluded that B₂₄N₂₄ nanocages could be an effective and efficient nanosensor for the detection of ML in light of their structural characteristics and electronic properties.

Opportunities and challenges of using high-sensitivity nanobiosensors to detect long noncoding RNAs: A preliminary review

The two types ofncRNAs, including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), are responsible for several biological processes within cells, such as the immune responses, cell growth and invasion, and regulation of the cell cycle. Rapidly expanding class of ncRNAs, lncRNAsinteract with other molecules to form chromatin-remodeling complexes. These potential hallmarks of diseases contribute to transcriptional and post-transcriptional regulation of several genes, possibly via cross-talk with other RNAs. Aberrant expression of lncRNAshas drawn increasing attention to the pathophysiology of different diseases, includingcancer and cardiovasculardiseases. Unfortunately, circulating lncRNAs are presented in the bloodstream at very low levels, making sensitive detection difficult. Currently, there are few methods for detecting these ncRNAs from which quantitative real-time-polymerase chain reaction (qRT-PCR) is the most routinely used technique. These techniqueslack sensitivity for intracellular detection of lncRNAs. Moreover, they are tedious and require a large sample size. Currently, nanotechnology has taken over the diagnostic field because of the tunable properties and modification opportunities. Furthermore, these conventional techniques can be merged with nanotechnology to improve detection sensitivity.This review highlights some of the most recent findings on nanotechnology-based methods and possible obstacles intheir application for moreaccurate sensing of lncRNAs.

Plasmonic Biosensors: Review

Biosensors have globally been considered as biomedical diagnostic tools required in abundant areas including the development of diseases, detection of viruses, diagnosing ecological pollution, food monitoring, and a wide range of other diagnostic and therapeutic biomedical research. Recently, the broadly emerging and promising technique of plasmonic resonance has proven to provide label-free and highly sensitive real-time analysis when used in biosensing applications. In this review, a thorough discussion regarding the most recent techniques used in the design, fabrication, and characterization of plasmonic biosensors is conducted in addition to a comparison between those techniques with regard to their advantages and possible drawbacks when applied in different fields.

Fiber-integrated WGM optofluidic chip enhanced by microwave photonic analyzer for cardiac biomarker detection with ultra-high resolution

Cardiac troponin I (cTnI) plays an important role in emergency diagnosis of cardiovascular diseases, which exists predominately in the form of cardiac troponin I-C (cTnI-C) complex. We proposed a fiber-integrated optofluidic chip immunosensor with time-delay-dispersion based microwave photonic analyzer (MPA) for cTnI-C detection. The whispering gallery mode (WGM) fiber probe was fabricated by embedding a polydopamine functionalized hollow glass microsphere (HGMS) into the etched capillary-fiber structure, and the WGMs could be excited through the efficient coupling between the thin-wall capillary and the HGMS. The reflective WGM optofluidic chip functioned as a wavelength tuner to construct fiber ring laser cavity, whose laser output wavelength was cTnI-C concentration-dependent. The tiny wavelength variation of sensing laser was converted into a radio-frequency (RF) response, which was retrieved by measuring the change of RF-domain free spectrum range (FSR) in time-delay-dispersion based MPA, and the quantitative detection of cTnI-C complex can be achieved with high resolution. Experimental results show that this immunosensor had a limit of detection (LOD) of 0.59 ng/mL, and a detection resolution of 1.2 fg/mL. The relative resolving power was 10²-10⁴-fold higher than that of others optical fiber cTnI biosensors. The proposed fiber-integrated optofluidic chip provides an innovative lab-on-chip diagnostic tool for myocardial damage.

Directivity-Enhanced Detection of a Single Nanoparticle Using a Plasmonic Slot Antenna

In situ refractive index sensors integrated with nanoaperture-based optical tweezers possess stable and sensitive responsivity to single nanoparticles. In most existing works, detection events are only identified using the total light intensity with directivity information ignored, leading to a low signal-to-noise ratio. Here, we propose to detect an optically trapped 20 nm silica particle by monitoring directivity of a plasmonic antenna. The main and secondary radiation lobes of the antenna reverse upon trapping because the particle-induced perturbation negates the relative phase between two antenna elements, leading to a significant change of the antenna front-to-back ratio. As a result, we obtain a signal-to-noise ratio of 20, with an order-of-magnitude improvement as compared to the intensity-only detection scheme.

Biowaste- and nature-derived (nano)materials: Biosynthesis, stability and environmental applications

Due to the environmental pollution issues and the supply of drinking/clean water, removal of both inorganic and organic (particularly dyes, nitroarenes, and heavy metals) to non-dangerous products and useful compounds are very important transformations. The deployment of sustainable and eco-friendly nanomaterials with exceptional structural and unique features such as high efficiency and stability/recyclability, high surface/volume ratio, low-cost production routes has become a priority; nonetheless, numerous significant challenges/restrictions still remained unresolved. The immobilization of green synthesized metal nanoparticles (NPs) on the natural materials and biowaste generated templates have been analyzed widely as a greener approach due to their environmentally friendly preparation methods, earth-abundance, cost-effectiveness with low energy consumption, biocompatibility, as well as adjustability in various cases of biomolecules as bioreducing agents. Natural and biowaste materials are widely considered as important sources to fabricate greener and biosynthesized types of metal, metal oxide, and metal sulfide nanomaterials using plant extracts. Integrating green synthesized nanoparticles with various biotemplates offers new practical composites for mitigating environmental challenges. In this review, degradation of dyes, reduction of toxic nitrophenols, absorption of heavy metals, and other hazardous/toxic environmental pollutants from contaminated water bodies using biowaste- and nature-derived nanomaterials are highlighted.

A DNA Biosensor Based on a Raspberry-like Hierarchical Nano-structure for the Determination of the Anticancer Drug Nilotinib

It is crucial to design fast, sensitive and affordable deoxyribonucleic acid (DNA) recognition instruments, and elucidate changes in DNA structure, for studying the interaction between DNA and chemotherapy drugs. Therefore, a DNA biosensor, based on a carbon paste electrode (CPE), modified with raspberry-like indium(III)/nickel oxide hierarchical nano-structures (In3+ /NiO RLHNSs) was constructed. An electrochemical readout should then give information on the interactions between anticancer drugs and double-stranded (ds)-DNA. The morphology as well as the electrochemical description of this new biosensor is described. Based on experimentally determined optimal conditions, ds-DNA modified with In3+ /NiO RLHNSs/CPE was used to evaluate the binding interaction of nilotinib, as an anti-cancer drug, with DNA through differential pulse voltammetry (DPV), UV-Vis spectroscopy, viscosity measurements and a computational docking process. The analyses indicated the linearity of the guanine oxidation signal at nilotinib concentration is given between 0.01 and 50.0 μm, with the limit of detection (LOD) equal to 0.62 nm. Additionally, the equilibrium constant (K) for the binding was determined to 1.5×104  m-1 . Through the quantitative measurement of nilotinib in serum samples with a high recovery rate of 101.3-98.0 %, the applicability of this approach was demonstrated. As a whole, this DNA biosensor may be promising for various bio-interactions.