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Surface plasmon resonance (SPR) is a technique utilized for the label-free detection of cancer cells. In this analysis, we introduce a photonic crystal fiber (PCF) designed with an open D-channel, featuring a layer of gold (Au) and titanium dioxide (TiO 2 ) as the plasmonic material. This effectively reduces the gap between the fiber core and the gold layer, resulting in improved performance. Additionally, incorporating TiO 2 between the gold and the silica substrate enhances their adhesion and contributes to a more robust structure. We conducted a comprehensive numerical analysis of the suggested biosensor utilizing the finite element method (FEM) integrated with perfectly matched layers (PML) within the COMSOL Multiphysics simulation tool. The design of this sensor is specifically intended for the detection of molecules with a refractive index (RI) varying from 1.25 to 1.43, achieving an impressive peak spectral sensitivity of 47,000 nm/RIU. For this purpose, we investigated RI values from 1.36 to 1.401 concerning six different cancer cell types. The highest spectral sensitivity is 5214.285 nm/RIU, while the amplitude sensitivity is -1481.1 RIU − 1 , which has been recorded for MCF-7 and HeLa cells. This proposed sensor shows improved amplitude sensitivity, signal-to-noise ratio (SNR), full width at half maximum (FWHM), figure of merit (FOM), and detection limit (DL) compared to existing biosensors, highlighting its potential for biosensing applications. Additionally, it is significant that according to the results, HeLa cells have a maximum resolution of 1.19 × 10 − 5 RIU and a FOM of 350 RIU − 1 .

MicroRNA exhibits differential expression levels in cancer and can affect cellular transformation, carcinogenesis and metastasis. Although fluorescence techniques using dye molecule labels have been studied, label-free molecular-level quantification of miRNA is extremely challenging. We developed a surface plasmon resonance sensor based on two-dimensional nanomaterial of antimonene for the specific label-free detection of clinically relevant biomarkers such as miRNA-21 and miRNA-155. First-principles energetic calculations reveal that antimonene has substantially stronger interaction with ssDNA than the graphene that has been previously used in DNA molecule sensing, due to thanking for more delocalized 5 s /5 p orbitals in antimonene. The detection limit can reach 10 aM, which is 2.3–10,000 times higher than those of existing miRNA sensors. The combination of not-attempted-before exotic sensing material and SPR architecture represents an approach to unlocking the ultrasensitive detection of miRNA and DNA and provides a promising avenue for the early diagnosis, staging, and monitoring of cancer. Label-free molecular-level quantification of MicroRNA (miRNA) remains challenging. Here, the authors develop a new surface plasmon resonance sensor based on two-dimensional nanomaterial of antimonene for the specific label-free detection of clinically relevant biomarkers such as miRNA-21 and miRNA-155.

Exploration of optoelectronic memristors with the capability to combine sensing and processing functions is required to promote development of efficient neuromorphic vision. In this work, the authors develop a plasmonic optoelectronic memristor that relies on the effects of localized surface plasmon resonance (LSPR) and optical excitation in an Ag–TiO2 nanocomposite film. Fully light‐induced synaptic plasticity (e.g., potentiation and depression) under visible and ultraviolet light stimulations is demonstrated, which enables the functional combination of visual sensing and low‐level image pre‐processing (including contrast enhancement and noise reduction) in a single device. Furthermore, the light‐gated and electrically‐driven synaptic plasticity can be performed in the same device, in which the spike‐timing‐dependent plasticity (STDP) learning functions can be reversibly modulated by visible and ultraviolet light illuminations. Thereby, the high‐level image processing function, i.e., image recognition, can also be performed in this memristor, whose recognition rate and accuracy are obviously enhanced as a result of image pre‐processing and light‐gated STDP enhancement. Experimental analysis shows that the memristive switching mechanism under optical stimulation can be attributed to the oxidation/reduction of Ag nanoparticles due to the effects of LSPR and optical excitation. The authors' work proposes a new type of plasmonic optoelectronic memristor with fully light‐modulated capability that may promote the future development of efficient neuromorphic vision. A novel plasmonic optoelectronic memristor is demonstrated for the first time relying on localized surface plasmon resonance (LSPR) effect. Both fully light‐modulated and light‐gated electrically‐driven synaptic modulation can be implemented in such a single device. Furthermore, combination of visual sensing, low‐level (contrast enhancement and noise reduction), and high‐level image processing (image recognition) promotes the development of efficient neuromorphic vision.

In the last 20 years, surface plasmon resonance (SPR) and its advancement with imaging (SPRi) emerged as a suitable and reliable platform in clinical analysis for label-free, sensitive, and real-time monitoring of biomolecular interactions. Thus, we report in this review the state of the art of clinical target detection with SPR-based biosensors in complex matrices (e.g., serum, saliva, blood, and urine) as well as in standard solution when innovative approaches or advanced instrumentations were employed for improved detection. The principles of SPR-based biosensors are summarized first, focusing on the physical properties of the transducer, on the assays design, on the immobilization chemistry, and on new trends for implementing system analytical performances (e.g., coupling with nanoparticles (NPs). Then we critically review the detection of analytes of interest in molecular diagnostics, such as hormones (relevant also for anti-doping control) and biomarkers of interest in inflammatory, cancer, and heart failure diseases. Antibody detection is reported in relation to immune disorder diagnostics. Subsequently, nucleic acid targets are considered for revealing genetic diseases (e.g., point mutation and single nucleotides polymorphism, SNPs) as well as new emerging clinical markers (microRNA) and for pathogen detection. Finally, examples of pathogen detection by immunosensing were also analyzed. A parallel comparison with the reference methods was duly made, indicating the progress brought about by SPR technologies in clinical routine analysis.

The localized surface plasmon resonance (LSPR) property of metallic nanoparticles is widely exploited for chemical and biological sensing. Selective biosensing of molecules using functionalized nanoparticles has become a major research interdisciplinary area between chemistry, biology and material science. Noble metals, especially gold (Au) and silver (Ag) nanoparticles, exhibit unique and tunable plasmonic properties; the control over these metal nanostructures size and shape allows manipulating their LSPR and their response to the local environment. In this review, we will focus on Ag-based nanoparticles, a metal that has probably played the most important role in the development of the latest plasmonic applications, owing to its unique properties. We will first browse the methods for AgNPs synthesis allowing for controlled size, uniformity and shape. Ag-based biosensing is often performed with coated particles; therefore, in a second part, we will explore various coating strategies (organics, polymers, and inorganics) and their influence on coated-AgNPs properties. The third part will be devoted to the combination of gold and silver for plasmonic biosensing, in particular the use of mixed Ag and AuNPs, i.e., AgAu alloys or Ag-Au core@shell nanoparticles will be outlined. In the last part, selected examples of Ag and AgAu-based plasmonic biosensors will be presented.

Photonic crystal fiber based surface plasmon resonance (PCF-SPR) biosensors are sophisticated optical sensing platforms that enable precise detection of minute refractive index (RI) variations for various applications. This study introduces a highly sensitive, low-loss, and simply designed PCF-SPR biosensor for label-free analyte detection, operating across a broad RI range of 1.31 to 1.42. In addition to conventional methods, machine learning (ML) regression techniques were integrated to predict key optical properties, while explainable AI (XAI) methods, particularly Shapley Additive exPlanations (SHAP), were used to analyze model outputs and identify the most influential design parameters. This hybrid approach significantly accelerates sensor optimization, reduces computational costs, and improves design efficiency compared to conventional methods. The proposed biosensor achieves impressive performance metrics, including a maximum wavelength sensitivity of 125,000 nm/RIU, amplitude sensitivity of −1422.34 RIU ⁻ ¹, resolution of 8 × 10 ⁻ ⁷ RIU, and a figure of merit (FOM) of 2112.15. ML models demonstrated high predictive accuracy for effective index, confinement loss, and amplitude sensitivity. SHAP analysis revealed that wavelength, analyte refractive index, gold thickness, and pitch are the most critical factors influencing sensor performance. The combination of a simple yet efficient design and advanced ML-driven optimization makes this biosensor a promising candidate for high-precision medical diagnostics, particularly cancer cell detection, and chemical sensing applications.

This study reports a five-layer surface plasmon resonance biosensor architecture comprising a BK7 glass substrate, silver plasmonic film, monolayer graphene, black phosphorus dielectric, and analyte region, engineered for high-precision detection of low refractive index media. The graphene–black phosphorus heterostructure synergistically exploits the exceptionally high surface-to-volume ratio of graphene and the anisotropic optical response of black phosphorus, enabling pronounced electromagnetic field confinement at the sensor interface. In particular, the detection procedure is mainly dependent on the emergence of the angular surface plasmon resonance based on the optimum values of the different geometrical and structural parameters. Therefore, the electromagnetic optimization using COMSOL Multiphysics was performed by varying the silver thickness, graphene thickness and black phosphorus thickness over an analyte index range of 1.29–1.38 RIU. The optimized configuration achieved a maximum sensitivity of 300°/RIU at n = 1.35 RIU, with a figure of merit of 45.455 RIU –1 and a detection limit of 0.018 RIU, surpassing previously reported architectures. Furthermore, predictive validation employing K-nearest neighbours regression demonstrated excellent reliability, yielding R² values between 92–100% and mean absolute errors of 0.005–0.012 RIU.

The notion of surface plasmon resonance (SPR) sensor research emerged more than eight decades ago from the first observed phenomena in 1902 until the first introduced principles for gas sensing and biosensing in 1983. The sensing platform has been hand-in-hand with the plethora of sensing technology advancement including nanostructuring, optical technology, fluidic technology, and light source technology, which contribute to substantial progress in SPR sensor evolution. Nevertheless, the commercial products of SPR sensors in the market still require high-cost investment, component, and operation, leading to unaffordability for their implementation in a low-cost point of care (PoC) or laboratories. In this article, we present a comprehensive review of SPR sensor development including the state of the art from a perspective of light source technology trends. Based on our review, the trend of SPR sensor configurations, as well as its methodology and optical designs are strongly influenced by the development of light source technology as a critical component. These simultaneously offer new underlying principles of SPR sensor towards miniaturization, portability, and disposability features. The low-cost solid-state light source technology, such as laser diode, light-emitting diode (LED), organic light emitting diode (OLED) and smartphone display have been reported as proof of concept for the future of low-cost SPR sensor platforms. Finally, this review provides a comprehensive overview, particularly for SPR sensor designers, including emerging engineers or experts in this field.

Different lines of evidence indicate that monitoring the blood levels of therapeutic antibodies, characterized by high inter-individual variability, can help to optimize clinical decision making, improving patient outcomes and reducing costs with these expensive treatments. A surface plasmon resonance (SPR)-based immunoassay has recently been shown to allow highly reliable and robust monitoring of serum concentrations of infliximab, with significant advantages over classical ELISA. The next level of advancement would be the availability of compact and transportable SPR devices suitable for easy, fast and cheap point-of-care analysis. Here we report the data obtained with recently developed, cost-effective, optical-fibre-based SPR sensors (SPR-POF), which allow the construction of a compact miniaturized system for remote sensing. We carried out an extensive characterization of infliximab binding to an anti-infliximab antibody immobilized on the SPR-POF sensor surface. The present proof-of-principle studies demonstrate the feasibility of the proposed SPR-POF platform for the specific detection of infliximab, in both buffer and human serum, and pave the way for further technological improvements.

A novel label-free surface plasmon resonance (SPR) aptasensor has been constructed for the detection of N-gene of SARS-CoV-2 by using thiol-modified niobium carbide MXene quantum dots (Nb 2 C-SH QDs) as the bioplatform for anchoring N-gene-targeted aptamer. In the presence of SARS-CoV-2 N-gene, the immobilized aptamer strands changed their conformation to specifically bind with N-gene. It thus increased the contact area or enlarged the distance between aptamer and the SPR chip, resulting in a change of the SPR signal irradiated by the laser (He-Ne) with the wavelength ( λ ) of 633 nm. Nb 2 C QDs were derived from Nb 2 C MXene nanosheets via a solvothermal method, followed by functionalization with octadecanethiol through a self-assembling method. Subsequently, the gold chip for SPR measurements was modified with Nb 2 C-SH QDs via covalent binding of the Au-S bond also by self-assembling interaction. Nb 2 C-SH QDs not only resulted in high bioaffinity toward aptamer but also enhanced the SPR response. Thus, the Nb 2 C-SH QD-based SPR aptasensor had low limit of detection (LOD) of 4.9 pg mL −1 toward N-gene within the concentration range 0.05 to 100 ng mL −1 . The sensor also showed excellent selectivity in the presence of various respiratory viruses and proteins in human serum and high stability. Moreover, the Nb 2 C-SH QD-based SPR aptasensor displayed a vast practical application for the qualitative analysis of N-gene from different samples, including seawater, seafood, and human serum. Thus, this work can provide a deep insight into the construction of the aptasensor for detecting SARS-CoV-2 in complex environments. Graphical abstract A novel label-free surface plasmon resonance aptasensor has been constructed to detect sensitively and selectively the N-gene of SARS-CoV-2 by using thiol-modified niobium carbide MXene quantum dots as the scaffold to anchor the N-gene-targeted aptamer.