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Optical biosensors have a significant impact on various aspects of our lives. In many applications of optical biosensors, fluidic chambers play a crucial role in facilitating controlled fluid delivery. It is essential to achieve complete liquid replacement in order to obtain accurate and reliable results. However, the configurations of fluidic chambers vary across different optical biosensors, resulting in diverse fluidic volumes and flow rates, and there are no standardized guidelines for liquid replacement. In this paper, we utilize COMSOL Multiphysics, a finite element analysis software, to investigate the optimal fluid volume required for two types of fluidic chambers in the context of the oblique-incidence reflectivity difference (OI-RD) biosensor. We found that the depth of the fluidic chamber is the most crucial factor influencing the required liquid volume, with the volume being a quadratic function of the depth. Additionally, the required fluid volume is also influenced by the positions on the substrate surface bearing samples, while the flow rate has no impact on the fluid volume.

This paper introduces an innovative optical biosensor designed for multimode refractive index (MMRI) detection, employing split ring resonator (SRR) technology for enhanced sensitivity in cancer cell analysis. The proposed biosensor comprises two concentric SRRs, one resembling a cube and the other a cylinder, each incorporating an air gap. Rigorous analysis and optimization of dimensional parameters were conducted using the finite difference time domain (FDTD) numerical solution method. The simulation results demonstrated that the biosensor achieves exceptional sensitivity and an optimal figure of merit (FOM). Specifically, the first mode of the biosensor exhibited a sensitivity exceeding 80 nm/RIU and an FOM surpassing 20 RIU⁻1, while the second mode demonstrated a sensitivity of 570 nm/RIU and an FOM exceeding 4 RIU⁻1. These results indicate that the first mode benefits from a higher FOM, enhancing precision and accuracy, while the second mode benefits from high sensitivity, enabling the detection of minute refractive index changes. With a primary focus on early cancer cell detection and timely treatment initiation to address the global cancer mortality burden, the biosensor's high-quality factor (Q-factor) and FOM promise significant advancements in cancer diagnostics and therapeutic interventions. [ABSTRACT FROM AUTHOR]

As concern raised by the World Health Organization (WHO) of antibiotic‐resistant and bio‐defensive bacteria, a metal–organic framework (MOF) based optical biosensor came into consideration for precise, quick, and sensitive detection of Escherichia coli (E. coli) (ATCC 10799) using bacteriophage as a bio‐recognition element. In the present study, amine‐functionalized Fe‐based MOF, i.e., NH2‐MIL‐101(Fe), was synthesized by the solvothermal method (approx. 531–1106 nm in size and 20 mV zeta potentials by DLS) and further characterized by SEM, XRD, ATR‐FTIR, UV–VIS, and photoluminescent (PL) spectroscopy. The lytic bacteriophage was isolated from a sewage sample, purified, and concentrated using the ultra‐centrifugation method and achieved a high titer of 7.3 × 1012 PFU/ml. The concentration, stability, and accessible receptor binding domains (RBDs) of the biorecognition element for binding with their analytes play an important role in developing sensitive and specific biosensor systems. To fulfill the mentioned criteria, optimized glutaraldehyde concentration was estimated at 0.25%, at 30 °C for conjugating maximum bacteriophage titer of 8.6 × 105 PFU/ml for each 1 mg amine functionalized iron‐based MOF. The synthesized detection probe has shown excellent photoluminescence and antibacterial activity and achieved a detection limit of 652 CFU/ml over a bacterial detection concentration range from 5.78 × 101 to 5.78 × 106 CFU/ml for E. coli with 10–12 min of response time, high specificity, and long‐term stability even at room temperature. Therefore, it can be inferred that this MOF‐based strategy can be helpful in the specific and sensitive detection of various bacterial pathogens using bacteriophage as a bio‐recognition element. [ABSTRACT FROM AUTHOR]

This study examined applications of polarized evanescent guided wave surface-enhanced Raman spectroscopy to determine the binding and orientation of small molecules and ligand-modified nanoparticles, and the relevance of this technique to lab-on-a-chip, surface plasmon polariton and other types of field enhancement techniques relevant to Raman biosensing. A simplified tutorial on guided-wave Raman spectroscopy is provided that introduces the notion of plasmonic nanoparticle field enhancements to magnify the otherwise weak TE- and TM-polarized evanescent fields for Raman scattering on a simple plasmonic nanoparticle slab waveguide substrate. The waveguide construct is called an optical chemical bench (OCB) to emphasize its adaptability to different kinds of surface chemistries that can be envisaged to prepare optical biosensors. The OCB forms a complete spectroscopy platform when integrated into a custom-built Raman spectrograph. Plasmonic enhancement of the evanescent field is achieved by attaching porous carpets of Au@Ag core shell nanoparticles to the surface of a multi-mode glass waveguide substrate. We calibrated the OCB by establishing the dependence of SER spectra of adsorbed 4-mercaptopyridine and 4-aminobenzoic acid on the TE/TM polarization state of the evanescent field. We contrasted the OCB construct with more elaborate photonic chip devices that also benefit from enhanced evanescent fields, but without the use of plasmonics. We assemble hierarchies of matter to show that the OCB can resolve the binding of Fe2+ ions from water at the nanoscale interface of the OCB by following the changes in the SER spectra of 4MPy as it coordinates the cation. A brief introduction to magnetoplasmonics sets the stage for a study that resolves the 4ABA ligand interface between guest magnetite nanoparticles adsorbed onto host plasmonic Au@Ag nanoparticles bound to the OCB. In some cases, the evanescent wave TM polarization was strongly attenuated, most likely due to damping by inertial charge carriers that favor optical loss for this polarization state in the presence of dense assemblies of plasmonic nanoparticles. The OCB offers an approach that provides vibrational and orientational information for (bio)sensing at interfaces that may supplement the information content of evanescent wave methods that rely on perturbations in the refractive index in the region of the evanescent wave. [ABSTRACT FROM AUTHOR]

DNA is fundamental for storing and transmitting genetic information. Analyzing DNA or RNA base sequences enables the identification of genetic disorders, monitoring gene expression, and detecting pathogens. Traditional detection techniques like polymerase chain reaction (PCR) and next-generation sequencing (NGS) have limitations, including complexity, high cost, and the need for advanced computational skills. Therefore, there is a significant demand for enzyme-free and amplification-free strategies for rapid, low-cost, and sensitive DNA detection. DNA biosensors, especially those utilizing plasmonic nanomaterials, offer a promising solution. This study introduces a novel DNA-functionalized waveguide-enhanced nanoplasmonic optofluidic biosensor using a nanogold-linked sorbent assay for enzyme-free and amplification-free DNA detection. Integrating plasmonic gold nanoparticles (AuNPs) with a glass planar waveguide (WG) and a microfluidic channel, fabricated through cost-effective, vacuum-free methods, the biosensor achieves specific detection of complementary target DNA sequences. Utilizing a sandwich architecture, AuNPs labeled with detection DNA probes enhance sensitivity by altering evanescent wave distribution and inducing plasmon resonance modes. The biosensor demonstrated exceptional performance in DNA detection, achieving a limit of detection (LOD) of 33.1 fg/mL (4.36 fM) with a rapid response time of approximately 8 min. This ultrasensitive, rapid, and cost-effective biosensor exhibits minimal background nonspecific adsorption, making it highly suitable for clinical applications and early disease diagnosis. The innovative design and fabrication processes offer significant advantages for mass production, presenting a viable tool for precise disease diagnostics and improved clinical outcomes. [ABSTRACT FROM AUTHOR]

Helicobacter pylori (H. pylori) is a common pathogen with a high prevalence of infection in human populations. The diagnosis of H. pylori infection is critical for its treatment, eradication, and prognosis. Biosensors have been demonstrated to be powerful for the rapid onsite detection of pathogens, particularly for point-of-care test (POCT) scenarios. In this work, we propose a novel optical biosensor, based on nanomaterial porous silicon (PSi) and photonic surface state Tamm Plasmon Polariton (TPP), for the detection of cytotoxin-associated antigen A (CagA) of H. pylori bacterium. We fabricated the PSi TPP biosensor, analyzed its optical characteristics, and demonstrated through experiments, with the sensing of the CagA antigen, that the TPP biosensor has a sensitivity of 100 pm/(ng/mL), a limit of detection of 0.05 ng/mL, and specificity in terms of positive-to-negative ratio that is greater than six. From these performance factors, it can be concluded that the TPP biosensor can serve as an effective tool for the diagnosis of H. pylori infection, either in analytical labs or in POCT applications. [ABSTRACT FROM AUTHOR]

The demand for accurate and efficient immunoassays calls for the development of precise, high-throughput analysis methods. This paper introduces a novel approach utilizing a weak measurement interface sensor for immunoassays, offering a solution for high throughput analysis. Weak measurement is a precise quantum measurement method that amplifies the weak value of a system in the weak interaction through appropriate pre- and post-selection states. To facilitate the simultaneous analysis of multiple samples, we have developed a chip with six flow channels capable of conducting six immunoassays concurrently. We can perform real-time immunoassay to determine the binding characteristics of spike protein and antibody through real-time analysis of the flow channel images and calculating the relative intensity. The proposed method boasts a simple structure, eliminating the need for intricate nano processes. The spike protein concentration and relative intensity curve were fitted using the Log-Log fitting regression equation, and R2 was 0.91. Utilizing a pre-transformation approach to account for slight variations in detection sensitivity across different flow channels, the present method achieves an impressive limit of detection(LOD) of 0.85 ng/mL for the SARS-CoV-2 the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein, with a system standard deviation of 5.61. Furthermore, this method has been successfully verified for monitoring molecular-specific binding processes and differentiating binding capacities. [ABSTRACT FROM AUTHOR]

Low‐cost, reliable, and efficient biosensors are crucial in detecting residual heavy metal ions (HMIs) in food products. At present, based on distance‐induced localized surface plasmon resonance of noble metal nanoparticles, enzyme‐mimetic reaction of nanozymes, and chelation reaction of metal chelators, the constructed optical sensors have attracted wide attention in HMIs detection. Besides, based on the enrichment and signal amplification strategy of nanomaterials on HMIs and the construction of electrochemical aptamer sensing platforms, the developed electrochemical biosensors have overcome the plague of low sensitivity, poor selectivity, and the inability of multiplexed detection in the optical strategy. Moreover, along with an in‐depth discussion of these different types of biosensors, a detailed overview of the design and application of innovative devices based on these sensing principles was provided, including microfluidic systems, hydrogel‐based platforms, and test strip technologies. Finally, the challenges that hinder commercial application have also been mentioned. Overall, this review aims to establish a theoretical foundation for developing accurate and reliable sensing technologies and devices for HMIs, thereby promoting the widespread application of biosensors in the detection of HMIs in food. [ABSTRACT FROM AUTHOR]

This paper presents a biosensor based on the resonant optical tunneling effect (ROTE) for detecting a carcinoembryonic antigen (CEA). In this design, sensing is accomplished through the interaction of the evanescent wave with the CEA immobilized on the sensor's surface. When CEA binds to the anti-CEA, it alters the effective refractive index (RI) on the sensor's surface, leading to shifts in wavelength. This shift can be identified through the cascade coupling of the FP cavity and ROTE cavity in the same mode. Experimental results further show that the shift in resonance wavelength increases with the concentration of CEA. The biosensor responded linearly to CEA concentrations ranging from 1 to 5 ng/mL with a limit of detection (LOD) of 0.5 ng/mL and a total Q factor of 9500. This research introduces a new avenue for identifying biomolecules and cancer biomarkers, which are crucial for early cancer detection. [ABSTRACT FROM AUTHOR]

Abstract Gold and silver nanoparticles have witnessed increased scientific interest due to their colourful colloidal solutions and exceptional applications. Comparing the localized surface plasmon resonance (LSPR) of gold and silver nanoparticles is crucial for understanding and optimizing their optical properties. This comparison informs the design of highly sensitive plasmonic sensors, aids in selecting the most suitable nanoparticles for applications like surface-enhanced infrared spectroscopy (SEIRA) and biomedical imaging, and guides the choice between gold and silver nanoparticles based on their catalytic and photothermal properties. Ultimately, the study of LSPR facilitates the tailored use of these nanoparticles in diverse scientific and technological applications. Two SEIRA methods combined with partial least squares regression (PLSR) chemometric tools were developed. This development is based on the synthesis of homogeneous, high-dense deposited metal nanoparticle islands over the surface of glass substrates to be used as lab-on-chip SEIRA sensors for the determination of bisacodyl (BIS) and its active metabolite in plasma. SEM micrographs revealed the formation of metallic islands of colloidal citrate-capped gold and silver nanoparticles of average sizes of 29.7 and 15 nm, respectively. BIS and its active metabolite were placed on the nanoparticles’ coated substrates to be directly measured, then PLSR chemometric modelling was used for the quantitative determinations. Plasmonic citrate-capped gold nanoparticle substrates showed better performance than those prepared using citrate-capped silver nanoparticles in terms of preparation time, enhancement factor, PLSR model prediction, and quantitative results. This study offers a way to determine BIS and its active metabolite in the concentration range 15–240 ng/mL in human plasma using inexpensive disposable glass-coated substrates that can be prepared in 1 h to get results in seconds with good recovery between 98.77 and 100.64%. The sensors provided fast, simple, selective, molecular-specific and inexpensive procedures to determine molecules in their pure form and biological fluid.

Gold and silver nanoparticles have witnessed increased scientific interest due to their colourful colloidal solutions and exceptional applications. Comparing the localized surface plasmon resonance (LSPR) of gold and silver nanoparticles is crucial for understanding and optimizing their optical properties. This comparison informs the design of highly sensitive plasmonic sensors, aids in selecting the most suitable nanoparticles for applications like surface-enhanced infrared spectroscopy (SEIRA) and biomedical imaging, and guides the choice between gold and silver nanoparticles based on their catalytic and photothermal properties. Ultimately, the study of LSPR facilitates the tailored use of these nanoparticles in diverse scientific and technological applications. Two SEIRA methods combined with partial least squares regression (PLSR) chemometric tools were developed. This development is based on the synthesis of homogeneous, high-dense deposited metal nanoparticle islands over the surface of glass substrates to be used as lab-on-chip SEIRA sensors for the determination of bisacodyl (BIS) and its active metabolite in plasma. SEM micrographs revealed the formation of metallic islands of colloidal citrate-capped gold and silver nanoparticles of average sizes of 29.7 and 15 nm, respectively. BIS and its active metabolite were placed on the nanoparticles' coated substrates to be directly measured, then PLSR chemometric modelling was used for the quantitative determinations. Plasmonic citrate-capped gold nanoparticle substrates showed better performance than those prepared using citrate-capped silver nanoparticles in terms of preparation time, enhancement factor, PLSR model prediction, and quantitative results. This study offers a way to determine BIS and its active metabolite in the concentration range 15–240 ng/mL in human plasma using inexpensive disposable glass-coated substrates that can be prepared in 1 h to get results in seconds with good recovery between 98.77 and 100.64%. The sensors provided fast, simple, selective, molecular-specific and inexpensive procedures to determine molecules in their pure form and biological fluid. [ABSTRACT FROM AUTHOR]

A new highly accurate optical biomedical sensor is proposed for cancer detection characterized by high sensitivity, small footprint, low cost, and low limit of detection. The sensor is based on double-ring resonators made of silicon on insulator. The type of the waveguide is critical in determining the sensor performance. To compromise the advantages and disadvantages of strip and slot waveguides, a mixed design of both has been introduced in literature at the expense of increased footprint compared to traditional sensors. Indeed, almost 27-fold footprint increase is required to improve the sensitivity by only one third of that of slot waveguide's sensitivity. In this paper, we introduce a new design that keeps the same footprint of traditional sensors, while achieving high sensitivity. This sensitivity depends on the resonance wavelength shift due to different refractive indices of the biosample. It has the value 109.8 nm/RIU compared to 55.57 nm/RIU and 129.621 nm/RIU for strip and slot waveguides, respectively. The hybrid waveguide quality factor is 537.7 while the quality factors of the strip and the slot waveguides are 627.99 and 380.76, respectively. In addition, the new design achieves the minimum limit of detection (0.0255) when compared to that of traditional designs. Furthermore, a new method of detection is proposed with the same design, providing a higher sensitivity over both traditional waveguide types with a value of 15.3, compared to 13.2 and 11.5 for strip and slot waveguides, respectively. In this method, the sensitivity relies on various values of output transmitted light at the same wavelength due to altering the biocell refractive index. The biosensor output equation is developed. In addition, the relationship between the supermodes and the sensitivity is determined at variance conditions. It is found that there is an inverse relation between them. [ABSTRACT FROM AUTHOR]

The coronavirus disease pandemic has led to an urgent need for rapid and accurate viral diagnosis. Therefore, rapid biosensors, not only for viruses but also for the detection of bacteria, disease diagnosis, and environmental monitoring, have been actively researched. Biosensors analyze the binding of biomolecules and target substances mainly based on electrochemical, electrical, or optical methods. To achieve precise and rapid diagnosis, it is crucial to reduce the time required for biomolecule–target substance binding. Typically, biomolecules reach the target substances through random diffusion, and to overcome the limitations associated herewith, biosensors have been integrated with alternating current (AC) electrokinetics (ACEK) technology. ACEK, through the application of alternating voltages, converts electrical energy into fluid motion, inducing pumping, mixing, concentration, and separation of the fluid. Its low power consumption makes it highly promising as a point-of-care diagnostic device. In this paper, we review the advancements in three ACEK technologies: AC electrothermal flow, AC electro-osmosis, and AC di-electrophoresis, to discuss the development of rapid biosensor fabrication methods based on electrical potential applications. [ABSTRACT FROM AUTHOR]

Heavy metal pollution has toxic repercussions on humans as well as on the environment, and these metals when retained in the environment significantly alter the biological and ecological cycles. The need of the hour is to design an approach for targeted sensing of heavy metal ions present in water bodies. The unique plasmonic and optical properties of gold nanoparticles serve as a foundation for the development of sensitive, selective, and analytical AuNP-based biosensing instruments. Modification/functionalization of AuNPs with different biomolecules such as DNA/DNAzymes, oligonucleotides, aptamers, and peptides serves as linking and capping agents for AuNPs. Functionalization with biomolecules offers biocompatibility, stability, enhanced catalytic activity, low toxicity, and selective binding and sensing to AuNPs. These biomolecules demonstrate distinct recognition skills and unique binding affinities with AuNPs. Bio-functionalized AuNP-based sensors have lately intrigued a significant research interest since they offer a practical use in environmental remediation through the sensing of harmful metal ions along with other pollutants. This review focuses on the new advancements in the development of nano-biosensors based on bio-based surface-functionalized AuNPs as probes, employed in heavy metal ions sensing. The mechanism of functionalization of AuNPs and the development of various optical sensors using bio-functionalized AuNPs have been discussed in depth. Finally, we have discussed the research priorities in this field that will help researchers for further investigations to develop promising future tools serving as "lab-on-chip" sensing devices. [ABSTRACT FROM AUTHOR]

IgM is the major circulating Ig isotype in teleost fish, showing in Antarctic fish unique features such as an extraordinary long hinge region, which plays a crucial role in antibody structure and function. In this work, we describe the replacement of the hinge region of a murine monoclonal antibody (mAb) with the peculiar hinge from Antarctic fish IgM. We use the CRISPR/Cas9 system as a powerful tool for generating the engineered mAb. Then, we assessed its functionality by using an innovative plasmonic substrate based on bimetallic nanoislands (AgAuNIs). The affinity constant of the modified mAb was 2.5-fold higher than that obtained from wild-type mAb against the specific antigen. Here, we show the suitability of the CRISPR/Cas9 method for modifying a precise region in immunoglobulin gene loci. The overall results could open a frontier in further structural modifications of mAbs for biomedical and diagnostic purposes.

There is a strong and growing need to monitor stress biomarkers in human beings and animals for real-time wellness assessment, which is a key indicator of health. Toward this, we report an optical fiber immunosensor based on laser-induced graphene (LIG) for the potential quantification and monitoring of cortisol hormone. The developed sensors were created using the Fabry-Pérot cavity principle. The cavities were filled with polyimide (PI) and, in some cases, PI mixed with gold nanoparticles. The interferometers were tested for temperature and refractive index, and an increase of two times in the sensitivity to the refractive index was observed due to the addition of the gold nanoparticles. In addition, the PI cavity was partially transformed into LIG using a CO2 20 kHz pulsed laser. The resulting LIG morphology was quite porous and presented a leafy texture. The presence of LIG creates a second cavity within the interferometer, and as a consequence, the spectral response of the interferometers resembled the Vernier effect. The refractive index behavior of the LIG-modified interferometers shows improvements in sensitivity up to 15.3 times due to the creation of the LIG cavity. The interferometers were then functionalized with anti-cortisol to promote an affinity for cortisol. Excellent sensitivities of up to -34.7 ± 0.7 nm/log(ng/mL) were achieved within few ng/mL concentration ranges (within the 0.5 to 3 ng/mL). The results obtained show an increase of up to 50 times in sensitivity when compared with other cortisol sensors. The achieved limit of detection was 0.1 ng/mL for the proposed sensors. The sensors’ responses were also shown to be immune to the interference from substances such as glucose, sucrose, fructose, and ascorbic acid. This study lays the foundation for new cortisol biosensors demonstrating a great potential for detection in a simple and highly sensitive way, opening its path for relevant biomedical and environmental monitoring applications in real samples. As a future outline, selectivity studies employing the detection of cortisol in the presence of interfering agents, both using synthetic and real samples, will be accomplished in order to fully investigate the potential of these sensing tools in real-life scenarios.

DNA is fundamental for storing and transmitting genetic information. Analyzing DNA or RNA base sequences enables the identification of genetic disorders, monitoring gene expression, and detecting pathogens. Traditional detection techniques like polymerase chain reaction (PCR) and next-generation sequencing (NGS) have limitations, including complexity, high cost, and the need for advanced computational skills. Therefore, there is a significant demand for enzyme-free and amplification-free strategies for rapid, low-cost, and sensitive DNA detection. DNA biosensors, especially those utilizing plasmonic nanomaterials, offer a promising solution. This study introduces a novel DNA-functionalized waveguide-enhanced nanoplasmonic optofluidic biosensor using a nanogold-linked sorbent assay for enzyme-free and amplification-free DNA detection. Integrating plasmonic gold nanoparticles (AuNPs) with a glass planar waveguide (WG) and a microfluidic channel, fabricated through cost-effective, vacuum-free methods, the biosensor achieves specific detection of complementary target DNA sequences. Utilizing a sandwich architecture, AuNPs labeled with detection DNA probes enhance sensitivity by altering evanescent wave distribution and inducing plasmon resonance modes. The biosensor demonstrated exceptional performance in DNA detection, achieving a limit of detection (LOD) of 33.1 fg/mL (4.36 fM) with a rapid response time of approximately 8 min. This ultrasensitive, rapid, and cost-effective biosensor exhibits minimal background nonspecific adsorption, making it highly suitable for clinical applications and early disease diagnosis. The innovative design and fabrication processes offer significant advantages for mass production, presenting a viable tool for precise disease diagnostics and improved clinical outcomes.

This study examined applications of polarized evanescent guided wave surface-enhanced Raman spectroscopy to determine the binding and orientation of small molecules and ligand-modified nanoparticles, and the relevance of this technique to lab-on-a-chip, surface plasmon polariton and other types of field enhancement techniques relevant to Raman biosensing. A simplified tutorial on guided-wave Raman spectroscopy is provided that introduces the notion of plasmonic nanoparticle field enhancements to magnify the otherwise weak TE- and TM-polarized evanescent fields for Raman scattering on a simple plasmonic nanoparticle slab waveguide substrate. The waveguide construct is called an optical chemical bench (OCB) to emphasize its adaptability to different kinds of surface chemistries that can be envisaged to prepare optical biosensors. The OCB forms a complete spectroscopy platform when integrated into a custom-built Raman spectrograph. Plasmonic enhancement of the evanescent field is achieved by attaching porous carpets of Au@Ag core shell nanoparticles to the surface of a multi-mode glass waveguide substrate. We calibrated the OCB by establishing the dependence of SER spectra of adsorbed 4-mercaptopyridine and 4-aminobenzoic acid on the TE/TM polarization state of the evanescent field. We contrasted the OCB construct with more elaborate photonic chip devices that also benefit from enhanced evanescent fields, but without the use of plasmonics. We assemble hierarchies of matter to show that the OCB can resolve the binding of Fe2+ ions from water at the nanoscale interface of the OCB by following the changes in the SER spectra of 4MPy as it coordinates the cation. A brief introduction to magnetoplasmonics sets the stage for a study that resolves the 4ABA ligand interface between guest magnetite nanoparticles adsorbed onto host plasmonic Au@Ag nanoparticles bound to the OCB. In some cases, the evanescent wave TM polarization was strongly attenuated, most likely due to damping by inertial charge carriers that favor optical loss for this polarization state in the presence of dense assemblies of plasmonic nanoparticles. The OCB offers an approach that provides vibrational and orientational information for (bio)sensing at interfaces that may supplement the information content of evanescent wave methods that rely on perturbations in the refractive index in the region of the evanescent wave.

Helicobacter pylori (H. pylori) is a common pathogen with a high prevalence of infection in human populations. The diagnosis of H. pylori infection is critical for its treatment, eradication, and prognosis. Biosensors have been demonstrated to be powerful for the rapid onsite detection of pathogens, particularly for point-of-care test (POCT) scenarios. In this work, we propose a novel optical biosensor, based on nanomaterial porous silicon (PSi) and photonic surface state Tamm Plasmon Polariton (TPP), for the detection of cytotoxin-associated antigen A (CagA) of H. pylori bacterium. We fabricated the PSi TPP biosensor, analyzed its optical characteristics, and demonstrated through experiments, with the sensing of the CagA antigen, that the TPP biosensor has a sensitivity of 100 pm/(ng/mL), a limit of detection of 0.05 ng/mL, and specificity in terms of positive-to-negative ratio that is greater than six. From these performance factors, it can be concluded that the TPP biosensor can serve as an effective tool for the diagnosis of H. pylori infection, either in analytical labs or in POCT applications.

Handheld biosensors have attracted substantial attention for numerous applications, including disease diagnosis, drug dosage monitoring, and environmental sensing. This study presents a novel handheld biosensor based on a gradient grating period guided-mode resonance (GGP-GMR) sensor. Unlike conventional GMR sensors, the proposed sensor's grating period varies along the device length; hence, the resonant wavelength varies linearly along the device length. If a GGP-GMR sensor is illuminated with a narrow band of light at normal incidence, the light resonates and reflects at a specific period but transmits at other periods; this can be observed as a dark band by using a complementary metal oxide semiconductor (CMOS) underneath the sensor. The concentration of a target analyte can be determined by monitoring the shift of this dark band. We designed and fabricated a handheld device incorporating a light-emitting diode (LED) light source, the necessary optics, an optofluidic chip with an embedded GGP-GMR sensor, and a CMOS. LEDs with different beam angles and bandpass filters with different full width at half maximum values were investigated to optimize the dark band quality and improve the accuracy of the subsequent image analysis. Substrate materials with different refractive indices and waveguide thicknesses were also investigated to maximize the GGP-GMR sensor's figure of merit. Experiments were performed to validate the proposed handheld biosensor, which achieved a limit of detection (LOD) of 1.09 × 10−3 RIU for bulk solution measurement. The sensor's performance in the multiplexed detection of albumin and creatinine solutions at concentrations of 0–500 μg/mL and 0–10 mg/mL, respectively, was investigated; the corresponding LODs were 0.66 and 0.61 μg/mL. [ABSTRACT FROM AUTHOR]

In this review, the latest progress in Prussian blue (PB)-based nanoparticles (NPs) in biosensor applications is discussed. PB-based NPs are iron-based and have mild synthesis conditions. Their application in biosensors mainly depends on their excellent physical and chemical properties, such as their good peroxidase activity. PB-based NPs have a conjugate structure, which strongly absorbs near-infrared light and converts it into heat energy, thereby enhancing their photothermal performance. As the active center, the iron atom has good electrochemical reversibility and excellent electrocatalytic activity owing to its different valence states. The application of PB-based NPs in biosensing has attracted considerable research attention. In this review, the existing synthesis methods of PB-based NPs are summarized. According to the physical and chemical properties of PB-based NPs, their research status in the fields of optical, photothermal, and electrochemical sensors is reviewed in detail. Finally, the development prospects of PB-based NPs are discussed, providing references for their synthesis and application in biosensors. [ABSTRACT FROM AUTHOR]

Nanostructured noble metal surfaces enhance the photoluminescence emitted by fluorescent molecules, permitting the development of highly sensitive fluorescence immunoassays. To this end, surfaces with silicon nanowires decorated with silver nanoparticles in the form of dendrites or aggregates were evaluated as substrates for the immunochemical detection of two ovarian cancer indicators, carbohydrate antigen 125 (CA125) and human epididymis protein 4 (HE4). The substrates were prepared by metal-enhanced chemical etching of silicon wafers to create, in one step, silicon nanowires and silver nanoparticles on top of them. For both analytes, non-competitive immunoassays were developed using pairs of highly specific monoclonal antibodies, one for analyte capture on the substrate and the other for detection. In order to facilitate the identification of the immunocomplexes through a reaction with streptavidin labeled with Rhodamine Red-X, the detection antibodies were biotinylated. An in-house-developed optical set-up was used for photoluminescence signal measurements after assay completion. The detection limits achieved were 2.5 U/mL and 3.12 pM for CA125 and HE4, respectively, with linear dynamic ranges extending up to 500 U/mL for CA125 and up to 500 pM for HE4, covering the concentration ranges of both healthy and ovarian cancer patients. Thus, the proposed method could be implemented for the early diagnosis and/or prognosis and monitoring of ovarian cancer. [ABSTRACT FROM AUTHOR]

Tamm Plasmon Polariton (TPP) is a nanophotonic phenomenon that has attracted much attention due to its spatial strong field confinement, ease of mode excitation, and polarization independence. TPP has applications in sensing, storage, lasing, perfect absorber, solar cell, nonlinear optics, and many others. In this work, we demonstrate a biosensing platform based on TPP resonant mode. Both theoretical analyses based on the transfer matrix method and experimental validation through nonspecific detection of liquids of different refractive indices and specific detection of SARS-CoV-2 nucleocapsid protein (N-protein) are presented. Results show that the TPP biosensor has high sensitivity and good specificity. For N-protein detection, the sensitivity can be up to 1.5 nm/(µg/mL), and the limit of detection can reach down to 7 ng/mL with a spectrometer of 0.01 nm resolution in wavelength shift. Both nonspecific detection of R.I. liquids and specific detection of N-protein have been simulated and compared with experimental results to demonstrate consistency. This work paves the way for design, optimization, fabrication, characterization, and performance analysis of TPP based biosensors. [ABSTRACT FROM AUTHOR]

Integrating biosensors with smartphones is becoming an increasingly popular method for detecting various biomolecules and could replace expensive laboratory-based instruments. In this work, we demonstrate a novel smartphone-based biosensor system with a gradient grating period guided-mode resonance (GGP-GMR) sensor. The sensor comprises numerous gratings which each correspond to and block the light of a specific resonant wavelength. This results in a dark band, which is observed using a CCD underneath the GGP-GMR sensor. By monitoring the shift in the dark band, the concentration of a molecule in a sample can be determined. The sensor is illuminated by a light-emitting diode, and the light transmitted through the GGP-GMR sensor is directly captured by a smartphone, which then displays the results. Experiments were performed to validate the proposed smartphone biosensor and a limit of detection (LOD) of 1.50 × 10−3 RIU was achieved for sucrose solutions. Additionally, multiplexed detection was demonstrated for albumin and creatinine solutions at concentrations of 0–500 and 0–1 mg/mL, respectively; the corresponding LODs were 1.18 and 20.56 μg/mL. [ABSTRACT FROM AUTHOR]

The threat posed by microbial infections to human health remains very significant, particularly in considering the increasing mechanisms of antibiotic resistance. Pseudomonas aeruginosa is known for its antibiotic resistance and is linked to serious conditions like ventilator-associated pneumonia and cystic fibrosis. Rapid infection elimination relies on identifying harmful bacteria and preventing colonization. Due to the redox-active nature of P. aeruginosa biomarkers metabolites, several electrochemical sensing approaches are being evaluated as diagnostic platforms for the rapid and precise detection of P. aeruginosa with high sensitivity. These sensors must be developed and modified to achieve optimal selectivity, sensitivity, and biocompatibility, enabling dynamic, real-time metabolite detection. This minireview highlights recent advancements in electrochemical and optical biosensors for detecting P. aeruginosa biomarkers, particularly pyocyanin. It highlighted design, analytical performance, biological recognition elements, and personalized wearable electrochemical sensor devices. It concludes with the future suggestions of sensor concepts for clinical diagnostics, environmental monitoring, and food safety.

The demand for accurate and efficient immunoassays calls for the development of precise, high-throughput analysis methods. This paper introduces a novel approach utilizing a weak measurement interface sensor for immunoassays, offering a solution for high throughput analysis. Weak measurement is a precise quantum measurement method that amplifies the weak value of a system in the weak interaction through appropriate pre- and post-selection states. To facilitate the simultaneous analysis of multiple samples, we have developed a chip with six flow channels capable of conducting six immunoassays concurrently. We can perform real-time immunoassay to determine the binding characteristics of spike protein and antibody through real-time analysis of the flow channel images and calculating the relative intensity. The proposed method boasts a simple structure, eliminating the need for intricate nano processes. The spike protein concentration and relative intensity curve were fitted using the Log-Log fitting regression equation, and R2 was 0.91. Utilizing a pre-transformation approach to account for slight variations in detection sensitivity across different flow channels, the present method achieves an impressive limit of detection(LOD) of 0.85 ng/mL for the SARS-CoV-2 the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein, with a system standard deviation of 5.61. Furthermore, this method has been successfully verified for monitoring molecular-specific binding processes and differentiating binding capacities.

The biosensor is an analytical device that targets the macromolecules and small molecules using a biological recognition system and later converts it into a measurable signal using a transducer. These biosensors are broadly used in various domains, enhancing the existing form and making it more specific for several applications. Presently, it is used for quantifying and detecting the biological-based components in the fields of forensics, medicine, food quality, pharmaceutical and environmental tracking, etc. These biosensors are cost-effective and produce safe and assured treatment for patients by examining the contagious disease biomarkers in the early stage without any side effects. This review has discussed the five essential components of biosensors and the upgraded form of these biosensors. Depending on the detection method, biosensors were classified into different types. Amongst various types, electrochemical and optical biosensors have more sensitivity and are widely used, and are briefly discussed here. Nanomaterials play a significant role in modern medical devices due to their excellent selectivity, high surface-to-volume ratio, strong chemical activity, increased specificity, and sensitivity that pave the way for more discoveries. Several nanomaterial-based biosensors are already on the market. This review mainly focuses on the fabrication methods of metal and metal oxide nanoparticles for sensing applications.

Antibody biotinylation is a process of attaching biotin molecules to antibodies by chemically modifying specific functional groups on the antibodies without altering their antigen recognition specificity. Biotin, a small vitamin, forms a strong and specific interaction with the protein streptavidin, resulting in a stable biotin-streptavidin (biotin-STV) complex. This biotin-STV interaction is widely exploited in various biotechnological applications, including biosensors. Biosensors are analytical devices that employ biological recognition elements, such as antibodies, enzymes, or nucleic acids, to detect and quantify target analytes in a sample. Antibodies are commonly used as recognition elements in biosensors due to their high specificity and affinity. In this study, the antibody anti-Bovine Serum Albumin (αBSA) has been biotinylated at different antibody:biotin ratios, and the stability of this labeling over time has been investigated. Furthermore, the sensitivity of the biosensor for detecting the Bovine Serum Albumin (BSA) protein has been compared using the biotinylated antibody and the non-biotinylated form, showing a four-fold improvement in detection. This system was also compared with the Enzyme-Linked ImmunoSorbent Assay (ELISA) technique. The advantages of using biotinylated antibodies in biosensors include increased stability and reproducibility of the biorecognition layer, as well as flexibility in sensor design, as different biotinylated antibodies can be utilized for diverse target analytes without altering the sensor's architecture.

This work presents a compact and sensitive refractive index sensor able to evaluate the concentration of an analyte in a sample. Its working principle leverages on the changes in the optical absorption features introduced by the sample itself on the evanescent waves of a light beam. The device's high compactness is achieved by embedding the sample–light interaction site and the detector in a 1 cm2 glass substrate, thanks to microelectronics technologies. High sensitivity is obtained by employing a low-noise p-i-n hydrogenated amorphous silicon junction, whose manufacture process requires only four UV lithographic steps on a glass substrate, thus ensuring low production costs. The system's capabilities are investigated by sensing the sugar content in three commercial beverages. Sensitivities of 32, 53 and 80 pA/% and limits of detection of 47, 29 and 18 ppm are achieved. The above performance is comparable with state-of-the-art results available in the literature, where more complex optical setups, expensive instrumentation and bulky devices are used. [ABSTRACT FROM AUTHOR]

Interleukin 6 (IL-6) is pleiotropic cytokine with pathological pro-inflammatory effects in various acute, chronic and infectious diseases. It is involved in a variety of biological processes including immune regulation, hematopoiesis, tissue repair, inflammation, oncogenesis, metabolic control, and sleep. Due to its important role as a biomarker of many types of diseases, its detection in small amounts and with high selectivity is of particular importance in medical and biological fields. Laboratory methods including enzyme-linked immunoassays (ELISAs) and chemiluminescent immunoassays (CLIAs) are the most common conventional methods for IL-6 detection. However, these techniques suffer from the complexity of the method, the expensiveness, and the time-consuming process of obtaining the results. In recent years, too many attempts have been conducted to provide simple, rapid, economical, and user-friendly analytical approaches to monitor IL-6. In this regard, biosensors are considered desirable tools for IL-6 detection because of their special features such as high sensitivity, rapid detection time, ease of use, and ease of miniaturization. In this review, current progresses in different types of optical biosensors as the most favorable types of biosensors for the detection of IL-6 are discussed, evaluated, and compared. [ABSTRACT FROM AUTHOR]

Monitoring microbial metabolism is vital for revealing the mechanism of disease related to microbial metabolism and providing guidance for biomanufacturing processes optimization. However, it remains a grand challenge to offer real‐time insights into microbial metabolism owing to the complex and dynamic process. In this paper, the recent advances and prospects of optical biosensors including the organic, genetic coding and inorganic optical biosensors are briefly described for real‐time monitoring of dynamic microbial metabolism. This paper points out that challenges remain in microbial heterogeneity. We believe that this work will inspire the application of developing new methods for single cell real‐time analysis. [ABSTRACT FROM AUTHOR]

With the development of technology, biosensors are increasingly used in the biomedical field. Due to the high sensitivity of optical signals, good stability, high signal‐to‐noise ratio, and different spectral characteristics of different analytes, optical biosensors can achieve direct and real‐time detection of analytes with high specificity compared with traditional analytical techniques. In view of the rapid development of optical biosensors for in vivo applications and their promising future, we have attempted to summarize the working principles and recent advances in application in humans, with the aim of helping readers to gain an in‐depth and detailed understanding of optical biosensors developed in recent years for applications in the biological living body. In this review, we focus on some of the current widely used and promising optical biosensors, including colorimetric biosensors, fluorescence biosensors, and surface‐enhanced‐Raman‐scattering‐based biosensors. The working principles for each type of optical biosensor are concisely described and the application of the biosensor in the living body is summarized by category. We conclude by looking at the prospects of in vivo applications of optical biosensors. [ABSTRACT FROM AUTHOR]

This paper presents a biosensor based on the resonant optical tunneling effect (ROTE) for detecting a carcinoembryonic antigen (CEA). In this design, sensing is accomplished through the interaction of the evanescent wave with the CEA immobilized on the sensor’s surface. When CEA binds to the anti-CEA, it alters the effective refractive index (RI) on the sensor’s surface, leading to shifts in wavelength. This shift can be identified through the cascade coupling of the FP cavity and ROTE cavity in the same mode. Experimental results further show that the shift in resonance wavelength increases with the concentration of CEA. The biosensor responded linearly to CEA concentrations ranging from 1 to 5 ng/mL with a limit of detection (LOD) of 0.5 ng/mL and a total Q factor of 9500. This research introduces a new avenue for identifying biomolecules and cancer biomarkers, which are crucial for early cancer detection.

Optical biosensors have a significant impact on various aspects of our lives. In many applications of optical biosensors, fluidic chambers play a crucial role in facilitating controlled fluid delivery. It is essential to achieve complete liquid replacement in order to obtain accurate and reliable results. However, the configurations of fluidic chambers vary across different optical biosensors, resulting in diverse fluidic volumes and flow rates, and there are no standardized guidelines for liquid replacement. In this paper, we utilize COMSOL Multiphysics, a finite element analysis software, to investigate the optimal fluid volume required for two types of fluidic chambers in the context of the oblique–incidence reflectivity difference (OI-RD) biosensor. We found that the depth of the fluidic chamber is the most crucial factor influencing the required liquid volume, with the volume being a quadratic function of the depth. Additionally, the required fluid volume is also influenced by the positions on the substrate surface bearing samples, while the flow rate has no impact on the fluid volume.

Monitoring the presence of viruses and bacteria in environmental reservoirs such as wastewater, lake water etc. is a very useful tool for early detection and controlling the spread of diseases, while also helping estimate the severity of infections at a community level. While several DNA sensors have been demonstrated for nucleic acid sensing for a variety of applications, most such demonstrations require sophisticated instrumentation or assays that need to be controllably performed in a well-equipped laboratory. In this work, we demonstrate a low-cost, portable device to detect DNA in wastewater and lake water, based on the color change in samples due to the intercalation of DNA with methylene blue (MB) dye. The optical sensor consists of a phase-sensitive detection circuit constructed with low-cost semiconductor ICs, red LED, and a silicon PIN photodiode. The phase-sensitive detection circuit has a resolution of 68μV, and the sensor has a limit of detection of 25.68 nM for DNA sensing. The utility of this sensor is demonstrated through the detection of bacteria (E. coli) and viruses (bacteriophage phi6) from wastewater and lake-water samples, respectively.

Abstract With the development of technology, biosensors are increasingly used in the biomedical field. Due to the high sensitivity of optical signals, good stability, high signal‐to‐noise ratio, and different spectral characteristics of different analytes, optical biosensors can achieve direct and real‐time detection of analytes with high specificity compared with traditional analytical techniques. In view of the rapid development of optical biosensors for in vivo applications and their promising future, we have attempted to summarize the working principles and recent advances in application in humans, with the aim of helping readers to gain an in‐depth and detailed understanding of optical biosensors developed in recent years for applications in the biological living body. In this review, we focus on some of the current widely used and promising optical biosensors, including colorimetric biosensors, fluorescence biosensors, and surface‐enhanced‐Raman‐scattering‐based biosensors. The working principles for each type of optical biosensor are concisely described and the application of the biosensor in the living body is summarized by category. We conclude by looking at the prospects of in vivo applications of optical biosensors.

Surface plasmon resonance (SPR)--based biosensors compete and excel among optical biosensors because of exceptional features such as high sensitivity, label-free, and real-time measurement, allowing the observation of molecular binding kinetics. In SPR biosensors and other biosensor techniques, surface functionalization and bioreceptor attachment are effective strategies to improve sensor performance. The application of an appropriate immobilization matrix for the bioreceptor is an essential step in maximizing the absorption of the bioreceptor on the sensor surface, thereby improving a specific target-sensor interaction. Furthermore, the materials should provide excellent optical properties to enhance the response signal. The high surface-to-volume ratio and high optical absorption of 2D materials qualify these requirements, thus promising advancements for SPR biosensors. This article reviews the recent SPR biosensor study with the use of the 2D materials family to improve the sensor performance, including graphene, transition metal dichalcogenides (TMDCs), MXene, black phosphorus (BP), perovskite, and boron nitride (BN). The materials properties and enhancement mechanisms of different 2D materials are discussed comprehensively. This review was expected to provide a future perspective and design approach for 2D materials-based SPR biosensors. [ABSTRACT FROM AUTHOR]

The development of diagnostic tools remains at the center of the health care system. In recent times optical biosensors have been widely applied in the scientific community, especially for monitoring protein–protein or nucleic acid hybridization interactions. Optical biosensors‐derived surface plasmon resonance (SPR) technology has appeared as a revolutionary technology at the current times. This review focuses on the research work in molecular biomarker evaluation using the technique based on SPR for translational clinical diagnosis. The review has covered both communicable and noncommunicable diseases by using different bio‐fluids of the patient's sample for diagnosis of the diseases. An increasing number of SPR approaches have been developed in healthcare research and fundamental biological studies. The utility of SPR in the area of biosensing basically lies in its noninvasive diagnostic and prognostic feature due to its label‐free high sensitivity and specificity properties. This makes SPR an invaluable tool with precise application in the recognition of different stages of the disease. [ABSTRACT FROM AUTHOR]

In this scientific work, we demonstrate, for the first time, a new biosensing system and procedure to measure specifically the total Tau (T-Tau) protein in serum, one of the most relevant biomarkers of Alzheimer's disease (AD). AD is a progressive brain disorder that produces neuronal and cognitive dysfunction and affects a high percentage of people worldwide. For this reason, diagnosing AD at the earliest possible stage involves improving diagnostic systems. We report on the use of interferometric bio-transducers integrated with 65 microwells forming diagnostic KITs read-out by using the Interferometric Optical Detection Method (IODM). Moreover, biofunctionalized silicon dioxide (SiO2) nanoparticles (NPs) acting as interferometric enhancers of the bio-transducers signal allow for the improvement of both the optical read-out signal and its ability to work with less-invasive biological samples such as serum instead of cerebrospinal fluid (CSF). As a result, in this paper, we describe for the first time a relevant diagnostic alternative to detect Tau protein at demanding concentrations of 10 pg/mL or even better, opening the opportunity to be used for detecting other relevant AD-related biomarkers in serum, such as β-amyloid and phosphorylated Tau (P-Tau), neurofilaments, among others that can be considered relevant for AD. [ABSTRACT FROM AUTHOR]

Noble metal nanostructured substrates enhance photoluminescence emitted from molecules immobilized onto their surface, allowing for the development of highly sensitive immunoassays employing fluorescent labels. In this work, nanostructured silver surfaces were implemented as substrates for the immunochemical detection of two ovarian cancer markers, carbohydrate antigen 125 (CA125) and human epididymis protein 4 (HE4). Biotinylated detection antibodies were used to allow for the detection of immunocomplexes through a reaction with streptavidin conjugated to Rhodamine Red-X. The detection limits achieved were 2.5 U/mL and 0.06 ng/mL for CA125 and HE4, respectively, with linear dynamic ranges, covering the concentration ranges of both healthy and ovarian cancer patients. [ABSTRACT FROM AUTHOR]

This paper proposed a photonic crystal fiber based on the surface plasmon resonance, with rectangular and circular holes. Rectangular air holes reduce confinement losses, and small circular air holes provide better matching of core and plasmonic modes. Noble plasmonic material gold is used to excite the surface plasmon and increases the operating wavelength range (400–950 nm). The analyte is located outside the sensor, which makes it easy to build the sensor. Numerical results display that the suggested sensor displays maximum amplitude sensitivity of 1540 RIU−1, an amplitude resolution of 6.49 × 10−7 RIU, a maximum wavelength sensitivity of 9000 nm/RIU, and a wavelength resolution of 1.11 × 10−5 RIU using the amplitude and wavelength interrogation methods, respectively. In this sensor, because of the presence of gold, chemical stability in the environment is high. In addition, the suggested sensor is very promising for medical and pharmaceutical measurement and diagnostic applications due to its high sensitivity, easy diagnosis, and easy manufacturing. [ABSTRACT FROM AUTHOR]

Cadmium ion (Cd(II)) is a pernicious environmental pollutant that has been shown to contaminate agricultural lands, accumulate through the food chain, and seriously threaten human health. At present, Cd(II) monitoring is dependent on centralized instruments, necessitating the development of rapid and on-site detection platforms. Against this backdrop, the present study reports on the development of a fluorometric aptasensor designed to target Cd(II), which is achieved through the integration of strand displacement amplification (SDA) and CRISPR/Cas12a. In the absence of Cd(II), the aptamer initiates SDA, resulting in the generation of a profusion of ssDNA that activates Cas12a, leading to a substantial increase in fluorescence output. Conversely, the presence of Cd(II) curtails the SDA efficiency, culminating in a significant reduction in fluorescence output. The proposed approach has been demonstrated to enable the selective detection of Cd(II) at concentrations of 60 pM, with the performance of the aptasensor validated in real water and rice samples. The proposed platform based on aptamer-target interaction holds immense promise as a signal-amplified and precise method for the detection of Cd(II) and has the potential to transform current hazard detection practices in food samples. [ABSTRACT FROM AUTHOR]

Liquid crystals (LCs) are reliable signal transducers for biosensors with chemical and biological sensing potentials demonstrated on the basis of their anisotropy. Thanks to the high sensitivity and fast response to analytes, the LC–solid, LC–aqueous and LC droplet interfaces facilitate sensing platforms to be established without the requirement of sophisticated and costly analytical instruments. In this mini-review, we summarise strategies of optical signal amplification to improve the detection limit of biological analytes at the LC–solid interface. Because approaches towards signal amplification for a single target analyte are seldom compared by discussing various LC-based biosensing platforms, this mini-review may provide implications for integrating current technologies to promote the development of multiplex platforms based on the LC–solid interface. [ABSTRACT FROM AUTHOR]

A high percentage of the population suffers from multiple food allergies justifying the importance of reliable diagnostic methods. Single-analyte solutions based on the determination of specific immunoglobulins E (sIgE) are safe and fast but are generally time-consuming and expensive. Thus sustainable microanalytical methods that provide multianalyte profiling information are highly demanded. This work presents the in vitro biosensing of specific IgE levels based on a reversed-phase allergen array. The approach consists of optical biosensing supported by direct multiplex immunoassays and on-disc technology. It identifies 12 sIgE associated with food allergies in a single analysis with a low serum sample volume (25 µL). After processing captured images, specific signals for each target biomarker correlate to their concentration. The assay analytically performs well with 0.3 IU/mL and 0.41 IU/mL as the detection and quantification limits in serum, respectively. This novel method achieves excellent clinical specificity (100%) and high sensitivity (91.1%), considering the diagnosis obtained by clinical history and ImmunoCAP analysis. The results demonstrate that microanalytical systems based on allergen arrays can potentially diagnose multiple food allergies and are easily implemented in primary care laboratory settings. [ABSTRACT FROM AUTHOR]