Search Results (3,200)

Background/Objectives: Silver nanoparticles (AgNPs) are highly valuable nanomaterials due to their unique optical and physicochemical properties. AgNPs have a lot of promise as contrast-enhancing and diagnostic agents in image-guided treatment. With a focus on their incorporation into image-guided and theranostic approaches, this narrative review attempts to assess the current function of AgNPs in imaging diagnostics. Methods: Using major scientific databases, such as PubMed, Web of Science, and Scopus, a narrative literature review has been conducted with an emphasis on recent preclinical and experimental research examining AgNP-based systems for diagnostic imaging applications. The design of the NPs, surface functionalization, imaging modality, and diagnostic performance of the evaluated studies were analyzed. Results: Due to their surface plasmon resonance and tunable physicochemical properties, AgNPs show great promise in a variety of imaging techniques, such as optical imaging, computed tomography (CT), and multimodal platforms, according to the reviewed literature. Functionalized AgNPs emerged as agents in image-guided therapy due to their improved target selectivity, enhanced imaging contrast, and signal amplification in tissues. Conclusions: AgNPs are appealing nanoscale platforms for image-guided methods and imaging diagnostics. Despite their encouraging preclinical results, some key issues, such as toxicity, biocompatibility, and clinical translation, remain critical. AgNP-based therapeutic and diagnostic systems will need to overcome these constraints in the future. Full article

NS4A plays a role in forming the flavivirus replication complex, which inhibits apoptosis in host cells by inducing autophagy, thereby promoting viral replication. The host protein ENO1 interacts with NS4A, but the precise mechanism underlying this interaction and its role in viral replication remain unclear. In this study, we identified ZIKV NS4A^1–73 as a key regulator of replication and infection cycles in both temporal and spatial dimensions. Through surface plasmon resonance (SPR) analysis, we demonstrated that ENO1 directly interacts with NS4A^1–73. This critical binding inhibits the enzymatic activity of ENO1 and reduces cellular lactate and ATP production. Our findings suggest that ZIKV NS4A may effectively impede cellular metabolism by targeting the host factor ENO1, thus disrupting the glycolytic process. This insight could open new avenues for targeting ZIKV and similar viruses in therapeutic strategies. Full article

Biosensors have emerged as a rapidly evolving area of research, offering transformative potential across biomedical diagnostics, environmental monitoring, and pharmaceutical applications. Among the diverse range of biosensing technologies, graphene-based surface plasmonic resonance (SPR) biosensors have attracted particular interest due to their exceptional sensitivity, scalability for mass production, and cost-effective fabrication processes. This study explores the operational principles and current design methodologies of graphene-based SPR biosensors, with a special emphasis on the role of electrolyte gating and its impact on sensor performance. Furthermore, the influence of graphene’s quantum capacitance is investigated as a critical parameter for improving the accuracy and reliability of performance predictions in the proposed sensor configuration. Computational analysis of sensitivity and key performance metrics was conducted. Notably, key performance metrics of the sensor improved upon incorporating quantum capacitance effects into the simulation framework. At a β₂-microglobulin concentration of 0.00118 g/L, the sensitivity increased to 174 GHz·g/L, the figure of merit reached 0.55 L/g, the quality factor was 0.01, the signal-to-noise ratio (SNR) rose to 0.008, and the detection accuracy (DA) reached 0.08 L/THz, demonstrating the significant impact of quantum capacitance on the sensor’s performance. These findings highlight the potential of quantum-electrostatic considerations to enhance the precision and efficacy of graphene-based SPR biosensors, paving the way for the development of next-generation biosensing platforms with improved analytical capabilities. Unlike conventional graphene SPR biosensors, which primarily detect refractive index changes near the graphene surface, our model explicitly considers the electrostatic effect of biomolecules on graphene’s Fermi energy. By modelling β2-microglobulin as a charged species, we compute the resulting electric double layer and incorporate quantum capacitance in series. This amplifies the charge-induced modulation of graphene’s optical conductivity, and, combined with a graphene perfect absorber design, leads to enhanced plasmonic resonance shifts. Consequently, our approach achieves higher sensitivity and more precise detection of biomolecular interactions compared to traditional simulations. Full article

Biosensors have evolved significantly since their invention in the mid-twentieth century. From a simple electrochemical device to the current inclusion of AI, these sophisticated tools are capable of label-free, real-time multiplex detection. To make these sensing systems even more powerful, the incorporation of DNA origami has allowed this technology to become extremely precise, recognisable, and programmable to a range of molecules. This paper systematically summarises the incorporation of DNA origami with biosensors such as fluorescence, surface-enhanced Raman spectroscopy (SERS), surface plasmon resonance (SPR), and electrochemical sensors as well as approaches that are used to design DNA origami nanostructures. These tools allow a range of targets to be detected, ranging from small molecules to larger biological species. Collectively, these studies demonstrate that DNA origami-based biosensors provide high sensitivity; precise spatial control; and rapid, modular detection capabilities. Furthermore, their versatility enables applications across a diverse range of sectors. However, key challenges including limited reproducibility, structural instability, photobleaching, and non-specific binding continue to hinder their widespread adoption. This review proposes future directions aimed at overcoming key limitations, including enhancing biocompatibility and structural stability, to support the development of more advanced and clinical point-of-care-applicable biosensors. Full article

This study demonstrates how synthesis conditions and bacterial cellulose (BC) functionalization influence the physicochemical properties and antibacterial performance of BC membranes containing green-synthesized silver nanoparticles (AgNPs). Mint and avocado-seed extracts enabled AgNP formation in aqueous media but differed in composition. UV–Vis screening across pH and temperature revealed inefficient synthesis at acidic pH, whereas higher temperatures produced broader localized surface plasmon resonance (LSPR) bands. Neutral conditions generated the most intense and narrow LSPR signals. Under optimized conditions (pH 7, 23 °C), AgNPs were confirmed by TEM, and their colloidal properties differed between extracts: mint-derived particles exhibited smaller hydrodynamic diameters and lower polydispersity than avocado-derived AgNPs. Two BC functionalization strategies were evaluated: immersion in pre-formed AgNP dispersions and in situ synthesis within the BC matrix. In situ membranes displayed stronger and better-defined LSPR peaks. Agitation released nanoparticles from all BC-AgNP membranes, with smaller species released from in situ systems. Antibacterial assays against E. coli showed greater bactericidal activity for in situ membranes. Avocado-derived in situ BC-AgNPs produced larger inhibition halos and prevented bacterial regrowth in liquid culture. Overall, in situ green synthesis within BC provides an effective route to robust and sustainable antibacterial BC membranes. Full article

This study uses a bismuth ferrite (BiFeO₃) and MXene (Ti₃C₂Tx) to design a surface plasmon resonance (SPR) biosensor for the sensitivity enhancement at a 633 nm wavelength. Here, MXene serves as a biorecognition element (BRE) layer to ensure stable and reliable biomolecule adsorption. The MXene is a family of two-dimensional (2D) materials with metallic-like conductivity, a large surface area that can attach biomolecules, and improve biocompatibility. The addition of a conductive 2D MXene layer and a high-index BiFeO₃ dielectric layer greatly improves light–matter interaction and evanescent field penetration at the sensing interface. Strong plasmonic coupling is indicated by the reflectance analysis, which shows a distinct and consistent shift in the resonance angle as analyte RI increases. This study examined the sensitivity at optimized Ag and BiFeO₃ layer thickness. At an Ag of 39 nm and BiFeO₃ of 3 nm thickness, the maximal sensitivity of 340.68°/RIU with a remarkable figure of merit (FoM) of 47.38/RIU is obtained. The overall detection accuracy (DA) and FoM are significantly improved by the large sensitivity enhancement, despite a slight increase in full width at half maximum (FWHM). Furthermore, the penetration depth (PD) of 198.50 nm (at RI:1.330) and 199.52 nm (at RI:1.335) is attained with the proposed structure. Due to its high sensitivity, reusability, and reproducibility, the SPR biosensor has the potential to be used in biochemical, environmental, and medical detection. Full article

Accurate permittivity characterization at terahertz frequencies is important for material analysis and device design, yet it remains challenging for small-volume samples and compact test structures. In this work, a terahertz permittivity sensor based on a spoof surface plasmon polariton (SSPPs) transmission line coupled to a backside split-ring resonator (SRR) is proposed and numerically studied. The SSPPs line is patterned on the top side of the substrate, while the SRR is etched on the backside, with the sample loaded into the SRR gap. The SSPPs mode penetrates through the substrate and excites the SRR, producing a pronounced transmission notch. Changes in the sample permittivity modulate the effective capacitance of the resonator, resulting in a monotonic shift in the notch center frequency. For relative permittivities from 1 to 8, the notch center frequency decreases from 152.1 GHz to 117.8 GHz, corresponding to a total shift of 34.3 GHz and an average sensitivity of about 4.90 GHz/ε_r. The minimum S₂₁ remains within approximately −23.80 to −21.56 dB, while the Q-factor stays in the range of 94.33–108.23, indicating good spectral readability. Tolerance analysis further shows that the resonance frequency is sensitive to critical structural dimensions and layer alignment, and practical implementation is therefore more suitable for single-device calibrated frequency-shift sensing. These results demonstrate the feasibility of the proposed dual-layer SSPPs–SRR configuration for compact permittivity sensing in the terahertz regime. Full article

Detecting changes in the permittivities of materials has important applications in electronic information, materials science, biomedicine, and many other fields. However, existing detection methods are limited by factors such as sample thickness and resonance intensity, making it difficult to achieve sensitive dielectric constant detection at desired frequency bands. This paper proposes a method for detecting the dielectric constant changes in samples based on destructive interference of spoof surface plasmon polaritons (SSPPs) in a dual-path transmission structure, which forms a characteristic absorption peak at the SSPPs’ cutoff frequency. Specifically, by utilizing the dependence of the SSPPs’ phase on the periodic unit, a constant π phase difference is formed at the cutoff frequency through the periodic unit number difference between the two paths, resulting in a cutoff frequency absorption peak. When the sample is coated on the SSPPs’ dual-path structure, the boundary conditions are altered, leading to a cutoff frequency shift, thereby enabling dielectric constant detection at the specified frequency. Simulation results show that, with proper structural design, the normalized characteristic frequency shift reaches 10.8%/${\epsilon }_S$ and further demonstrates dramatic robustness against initial phase difference, sample thickness and sample loss. In summary, this work provides a novel high-precision and high-robustness method for detecting dielectric constant changes in samples at specified frequencies. Full article

Background/Objectives: Alzheimer’s disease (AD) is characterized by amyloid-beta accumulation and neuroinflammation, yet the molecular target of Ginsenoside Rg1 remains elusive. This study aimed to elucidate the neuroprotective mechanism of Ginsenoside Rg1, specifically investigating its interaction with C-C motif chemokine receptor 3 (CCR3). Methods: We utilized 5xFAD transgenic mice and CCR3-overexpressing BV2 microglial cells. Behavioral assessments, enzyme-linked immunosorbent assays, quantitative real-time polymerase chain reaction, molecular docking, and surface plasmon resonance were employed to evaluate cognitive function and molecular pathways. Results: Ginsenoside Rg1 treatment significantly ameliorated spatial learning and memory deficits. Quantitatively, Rg1 reduced cortical amyloid-beta 1–40 levels (p < 0.05) and bound directly to CCR3 with a dissociation constant of 3.599 × 10⁻⁵ mol/L. This inhibition suppressed neuroinflammation and restored neurotrophic factors, including Brain-derived neurotrophic factor. Conclusions: CCR3 is a novel pharmacological target for Ginsenoside Rg1, providing a precise molecular basis for its neuroprotective effects. Future research should focus on clarifying the pharmacokinetic profile and brain bioavailability of Ginsenoside Rg1 to facilitate clinical translation. Full article

Background: Prostate cancer (PCa) is the leading male urinary malignancy globally. Our previous article demonstrated the anti-PCa activity of Euphorbia humifusa Willd water extract (EHW) and some of its compounds via downregulating AR expression, but the anti-PCa active compounds from Euphorbia humifusa Willd (EH) and their mechanisms of action are yet to be clarified. Thus, the current article studied the in vitro anti-PCa effects of 3,3′-di-O-methylellagic acid (3,3′-di-O-Me-EA) derived from EHW and the related mechanism involved. Methods: 3,3’-di-O-Me-EA was isolated from EHW applying bioassay-guided fractionation. The spectroscopic methods were used to determining the structure of 3,3′-di-O-Me-EA. The drug-likeness and ADMET properties (absorption, distribution, metabolism, excretion, and toxicity) of 3,3′-di-O-Me-EA were analyzed in silico. Molecular docking and real-time surface plasmon resonance (SPR) analysis were performed to measure the interaction of 3,3′-di-O-Me-EA and VDAC1 protein. The viability and apoptosis of 22RV-1 and DU145 PCa cells were determined using MTT and Annexin V-FITC staining assay, respectively. q-PCR and Western blot experiments were used to analyzing the gene and protein expressions of VDAC1. Results: 3,3′-di-O-Me-EA was isolated and purified from EHW with a purity of ≥90.06%, and its structure was identified by HRTOF mass, NMR, and an authentic standard. In silico ADMET analysis indicated its favorable drug-like and pharmacokinetic properties. Molecular docking and SPR results confirmed that 3,3′-di-O-Me-EA could bind with the VDAC1 protein. Moreover, 3,3′-di-O-Me-EA dose- and time-dependently inhibited 22RV-1 and DU145 PCa cell viability, and induced apoptosis in a dose-dependent manner (p < 0.05). RT-qPCR and Western blot results showed that 3,3′-di-O-Me-EA dose-dependently up-regulated VDAC1 gene and protein expression levels in 22RV-1 and DU145 cells (p < 0.05). Meanwhile, in VDAC1-depleted 22RV-1 and DU145 cells, 3,3′-di-O-Me-EA down-regulated VDAC1 gene and protein expression levels, increased cell viability, and inhibited apoptosis compared to 22RV-1 and DU145 cells (p < 0.05). Furthermore, 3,3′-di-O-Me-EA enhanced VDAC1 gene and protein expression levels, inhibited cell viability, and induced apoptosis in VDAC1-overexpressed 22RV-1 and DU145 cells compared with 22RV-1 and DU145 cells (p < 0.05). Overall, EH active compound 3,3′-di-O-Me-EA may inhibit viability and induce apoptosis of 22RV-1 and DU145 PCa cells via up-regulating VDAC1 gene and protein expression levels. Conclusion: The results indicated that the 22RV1 and DU145 PCa cell viability inhibitory effects of 3,3′-di-O-Me-EA isolated from EH may be mediated by induction of apoptosis through up-regulation of VDAC1 gene and protein expression levels. Full article

Realizing high-quality-factor (high-Q) plasmonic resonances in the visible regime is critical for enhancing light-matter interactions and advancing biochemical sensing. However, traditional localized surface plasmon resonances (LSPRs) typically suffer from broad spectral linewidths due to severe radiative damping. In this work, we propose a simple two-dimensional symmetric gold nanohole-array metasurface that supports a symmetry-protected bound state in the continuum (SP-BIC) at normal incidence. By introducing extrinsic symmetry breaking via oblique incidence, this non-radiative dark state is successfully transformed into an observable high-Q quasi-BIC Fano resonance. Cartesian multipole decomposition reveals that this sharp mode ($\lambda \approx 688$ nm) is predominantly driven by a tightly confined Magnetic Dipole (MD) excitation, which drastically suppresses radiative leakage compared to the highly damped Electric Dipole (ED)-dominated LSPR. Consequently, the quasi-BIC mode exhibits an ultra-narrow spectral linewidth ($\mathrm{FWHM}\approx 17.4$ nm). While its bulk sensitivity ($236.9$ nm/RIU) is slightly lower than that of the LSPR mode, the exceptionally sharp resonance yields a remarkably low Limit of Detection (LOD) of $7.35\times {10}^{-3}$ RIU, achieving a nearly five-fold improvement over the traditional LSPR. Furthermore, the quasi-BIC mode maintains an outstanding Figure of Merit (FOM up to ∼19.7 ${\mathrm{RIU}}^{-1}$) across the entire sensing range. By eliminating the need for complex asymmetric nanofabrication, this robust angle-tuned design strategy provides a highly promising platform for the development of high-resolution, low-cost optical biosensors. Full article

This study introduces a switchable and tunable multimodal, multi-peak, perfect terahertz absorber, utilizing a composite structure of graphene and double concentric metal rings. From bottom to top, the absorber consists of a gold substrate, a SiO₂ dielectric layer, a patterned graphene layer, another SiO₂ dielectric layer, and double concentric metal rings on the top. The structure achieves three high-absorption resonance peaks in the far-infrared band: a relatively broad peak with 99.05% absorptance at 38.128 THz, and two extremely narrow peaks with 99.56% and 97.23% absorptance at 47.909 THz and 49.873 THz, respectively. Analysis of the absorption spectra and electric field distributions reveals that the generation mechanism of Peak I is Fabry–Pérot cavity resonance, while Peaks II and III result from the coupling between the high-order localized surface plasmons in the outer ring and the graphene surface plasmon polaritons. Benefiting from graphene’s excellent electrical tunability, the absorption peaks’ positions and intensities can be dynamically tuned by varying the Fermi level. The core innovation of this work lies in the high-level integration of multiple functionalities. By leveraging the sensitive response of Peak III to variations in the Fermi level, a four-input AND logic gate is embedded within the metamaterial absorber in this frequency band. The Fermi levels of four independent graphene regions serve as the binary inputs, while the absorption state of Peak III is defined as the logical output. Additionally, the two narrow peaks display high sensitivity to the surrounding refractive index, with sensitivities of 30.1 THz/RIU and 62.5 THz/RIU, demonstrating significant potential for sensing. This multifunctional integrated device combines tunable absorption, a logic gate, and sensing capabilities, making it promising for terahertz communication systems, intelligent sensing networks, and reconfigurable platforms. Full article

Polyaniline-cadmium sulfide-gold (PANI-CdS-Au) nanocomposites were synthesized with varying Au loadings (0.023, 0.046, 0.092 wt%) to enhance antibacterial performance. Structural (FTIR, XRD) and morphological (FESEM) analyses confirmed successful formation, with nearly homogeneous nanoparticle distribution (27–53 nm) and slight XRD peak shifts indicating interfacial interactions between PANI, CdS, and Au. UV–Vis spectra revealed gold surface plasmon resonance and polaronic transitions consistent with PANI emeraldine base. XRD results showed the expected wurtzite CdS and fcc Au phases. Agar well diffusion tests against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) demonstrated that the 0.092 wt% of Au composite produced the largest inhibition zones at 100 µg mL⁻¹ (E. coli: 36 mm; S. aureus: 24 mm), with the same trend at 25 µg mL⁻¹. The results indicate that PANI–CdS/Au nanocomposites are promising antibacterial materials; however, the presence of CdS necessitates additional cytotoxicity assays to confirm their suitability for medical applications. Full article

Surface plasmon resonance (SPR) is a label-free, real-time biosensing technology with high sensitivity for the detection of biomolecular interactions. This review highlights recent advances in SPR biosensors for the detection of SARS-CoV-2. First, we outline design strategies, especially advanced plasmonic nanostructures and precise surface functionalization, that improve the specificity and binding affinity to viral targets. Next, we cover signal amplification methods, such as nanoparticle conjugation and plasmonic photothermal effects, which enhance the sensitivity for low-abundance viral components. Subsequently, we conducted a comparative analysis of SPR biosensors alongside traditional and emerging detection approaches for SARS-CoV-2, elucidating their individual merits and drawbacks. We also discuss how machine learning improves data interpretation and diagnostic accuracy. Finally, we discuss the current challenges and future development directions, particularly for clinical diagnostics, epidemic monitoring, and public health security. These advances support faster, more reliable, and accessible diagnostics for current and future viral outbreaks. Full article

Noble metal nanostructures provide versatile platforms for light manipulation through localized surface plasmon resonances (LSPRs). Among them, triangular silver nanoplates (AgNPTs) exhibit strong field-enhancement and spectral tunability, yet assembling them reproducibly on solids is challenging. We report a two-step functionalization strategy for constructing ordered AgNPT dimers on silica substrates, combining 3-aminopropyltriethoxysilane (APTES) anchoring with 1,4-butanedithiol bridging. AFM reveals face-to-face dimers with well-defined sub-nanometer gaps. Large-area AFM statistics collected over multiple regions (N = 80 nanoplates per condition) confirm reproducible and selective vertical dimerization. Extinction spectroscopy reveals sequential dielectric and coupling effects: thiol adsorption red-shifts the main resonance from 700 to 780 nm because of increased local refractive index and near-field damping, whereas dimerization partially restores it to ≈750 nm, consistent with plasmon hybridization within rigid ∼0.7 nm molecular gaps, where nonclassical moderation may occur but classical hybridization fully explains the observed shifts. Concomitantly, the extinction intensity doubles, following an exponential growth toward saturation during assembly. Surface-enhanced Raman scattering (SERS) measurements using 4-mercaptobenzoic acid (4-MBA) confirm a fourfold increase in the SERS enhancement factor from monolayer to bilayer, consistent with near-field coupling and hotspot formation at interplate junctions. Quantitative plasmon sensitivity analysis yields comparable results between experiments and finite-difference-time-domain simulations, confirming that the observed spectral shifts arise from near-field coupling and dielectric modulation rather than ensemble effects. This reproducible methodology enables precise tuning of NPT orientation, spacing, and optical response, providing a robust platform for enhanced sensing, SERS, and nanophotonic device engineering. Full article