Search Results (189)

The Isles of Scilly are an archipelago of islands in the far southwest of the UK which contain numerous beds of wild bivalve molluscs which are recreationally harvested for local consumption. However, the islands have never previously been assessed for the presence of harmful algae and their shellfish toxin metabolites which can cause serious human health impacts. This study sought to address these knowledge gaps through the analysis of seawater and shellfish tissues for microalgae and toxins utilizing portable and lab-based microscopy, nanopore sequencing, chemical analysis and immunoassay kits. The study design was affected by the national COVID-19 lockdown which enforced implementation of citizen-led sampling and in-field microscopy. Microscopy and sequencing approaches led to the confirmation of multiple HAB species of concern, including those potentially responsible for production of neurotoxic and diarrhetic shellfish toxins. A portable microscope was successfully utilized in the field for recognition of microalgae and for early warning of potential shellfish toxicity events. Chemical analysis of cockle, clam and mussel samples confirmed the detection of paralytic, diarrhetic and amnesic shellfish toxins, with an unusual okadaic acid group toxin profile reaching a maximum toxicity of approximately half the regulatory limit as defined by EU law. The Sensoreal Alert Lateral Flow Assay was used to screen and highlight samples containing higher concentrations of DSP toxins. Furthermore, Tetrodotoxin was detected for the first time in the UK in cockle and grooved carpet shells. Multiple saxitoxin analogues were also detected in two echinoderm species, with this providing the first ever report of paralytic shellfish toxins in the spiny starfish, Marthasterias glacialis. The toxin profiles in the two species varied significantly with a dominance of GTX4 in Luidia ciliaris as opposed to a dominance of STX in Marthasterias glacialis. Overall, the study showed that a multi-method assessment of a previously unexplored region within the UK territory contained microalgae and toxins of concern to human health, and that a citizen-led programme could be instigated using portable microscopy and rapid toxin testing to assess the early warning for potentially harmful microalgae and toxins in the region, with confirmatory analysis being conducted to establish actual levels of risk for local consumers of seafood. Full article

Adeno-associated viruses (AAVs) are a leading vector for gene therapy, yet their clinical utility is limited by the lack of robust quality control methods to distinguish between empty (AAV_empty), partially loaded (AAV_partial), and fully DNA loaded (AAV_full) capsids. Current analytical techniques provide partial insights but remain limited in sensitivity, throughput, or resolution. Here we present a multimodal plasmonic nanopore sensor that integrates optical trapping with electrical resistive-pulse sensing to characterize AAV9 capsids at the single-particle level in tens of μL sample volumes and fM range concentrations. As a model system, we employed AAV9 capsids not loaded with DNA, capsids loaded with a self-complementary 4.7 kbp DNA (AAV_scDNA), and ones loaded with single-stranded 4.7 kbp DNA (AAV_ssDNA). Ground-truth validation was performed with analytical ultracentrifugation (AUC). Nanosensor data were acquired concurrently for optical step changes (occurring at AAV trapping and un-trapping) both in transmittance and reflectance geometries, and electrical nanopore resistive pulse signatures, making for a total of five data dimensions. The acquired data was then filtered and clustered by Gaussian mixture models (GMMs), accompanied by spectral clustering stability analysis, to successfully separate between AAV species based on their DNA load status (AAV_empty, AAV_partial, AAV_full) and DNA load type (AAV_scDNA versus AAV_ssDNA). The motivation for quantifying the AAV_empty and AAV_partial population fractions is that they reduce treatment efficacy and increase immunogenicity. Likewise, the motivation to identify AAV_scDNA population fractions is that these have much higher transfection rates. Importantly, the results showed that the nanosensor could differentiate between AAV_scDNA and AAV_ssDNA despite their identical masses. In contrast, AUC could not differentiate between AAV_scDNA and AAV_ssDNA. An equimolar mixture of AAV_scDNA, AAV_ssDNA and AAV_empty was also measured with the sensor, and the results showed the expected population fractions, supporting the capacity of the method to differentiate AAV load status in heterogeneous solutions. In addition, less common optical and electrical signal signatures were identified in the acquired data, which were attributed to debris, rapid entry re-entry to the optical trap, or weak optical trap exits, representing critical artifacts to recognize for correct interpretation of the data. Together, these findings establish plasmonic nanopore sensing as a promising platform for quantifying AAV DNA loading status and genome type with the potential to extend ultra-sensitive single-particle characterization beyond the capabilities of existing methods. Full article

Zero-depth nanopores present a promising solution to the challenges associated with ultrathin membranes used in solid-state resistive pulse sensors for DNA sequencing. Most existing fabrication methods are either complex or lack the nanoscale precision required. In this study, we introduce a cost-effective approach that combines PDMS molding at the intersection of silicon micro-blades with an innovative high-resolution nano-positioning technique. These blades are created through photolithography and a two-step KOH wet etching process, allowing for the formation of sub-50 nm 3D rhombic zero-depth nanopores featuring large vertex angles. To address the limitations of SEM imaging—such as dielectric charging and deformation of PDMS membranes under electron beam exposure—we devised a finite element model (FEM) that correlates electrical conductance with pore size and electrolyte concentration. This model aligns closely with experimental data, yielding a mean absolute percentage error of 3.69%, thereby enabling real-time indirect sizing of the nanopores based on the measured conductance. Additionally, we identified a critical channel length beyond which pore resistance becomes negligible, facilitating a linear relationship between conductance and pore diameter. The nanopores produced using this method exhibited a 2.4-fold increase in conductance compared to earlier designs, highlighting their potential for high-precision DNA sequencing applications. Full article

We report the fabrication of nanoscale MoS₂ (nMoS₂) via laser ablation in liquid and its application in electrochemical sensing. The laser ablation process fragments microscale MoS₂ sheets into ~5 nm dots with stable aqueous dispersibility. Electrochemical analysis reveals that nMoS₂ possesses multiple reversible redox states, enabling it to participate in redox cycling reactions that can amplify electrochemical signals. When the nMoS₂ is embedded in an electrochemically inert matrix, a chitosan layer, and subsequently incorporated within a nanostructured Au electrode, the nMoS₂-participating redox cycling reactions are further enhanced by the nanoconfinement effect, leading to synergistic signal amplification. As a model system, this hybrid nMoS₂-in-nanoporous Au electrode demonstrates a 9-fold increase in sensitivity for detecting pyocyanin, a biomarker of Pseudomonas aeruginosa infection, compared with a flat electrode without nMoS₂ loading. This study not only elucidates the redox characteristics of laser-fabricated zero-dimensional transition metal dichalcogenides but also presents a strategy to integrate semiconducting nanomaterials with metallic nanostructures for high-performance electrochemical sensing. Full article

The growing threat of airborne biological agents necessitates rapid, sensitive, and portable detection systems to mitigate risks to public health and national security. We present a comprehensive overview of biosensor technologies developed for airborne biothreat detection, with a focus on aptamer-based electrochemical sensors. These sensors offer key advantages in portability, chemical stability, and adaptability for multiplexed detection in field settings. The urgency for real-time surveillance tools capable of identifying viral, bacterial, and toxin-based agents is discussed, particularly in the context of biodefense. Aerosolized particle capture strategies are reviewed, focusing on microfluidics for micron-sized particles and condensation-based systems for submicron-sized particles, which are preferred for their small-volume operation and seamless integration with biosensors. Key biosensor components are described, including recognition elements—such as aptamers—and transduction mechanisms like electrochemical impedance spectroscopy. EIS is highlighted for its label-free, miniaturizable, and real-time readout capabilities, making it well-suited for portable biosensors. Advances in sensing strategies for both viral and bacterial targets are explored, featuring innovations in nanoporous membrane platforms, nanomaterials, and multiplexed assay formats. Recent developments demonstrate improved sensitivity through nanopore-based signal amplification and enhanced selectivity using engineered aptamer libraries. The review concludes by addressing current limitations, including environmental stability, system integration, and the need for validation with complex real-world samples. Future directions point toward the development of fully integrated, field-deployable biosensing platforms that combine effective aerosol capture with robust and selective biosensing technologies. Full article

Nanoporous gold (NPG), characterized by a bicontinuous network of nanoscale solid ligaments and pore channels, exhibits exceptional physical and chemical properties. However, the limited strength and stiffness of traditional isotropic NPG (INPG) have constrained its engineering applications. To effectively enhance the mechanical properties of NPG, this work proposes an innovative anisotropic NPG (ANPG) architecture featuring unidirectional ligament orientation. By controlling spinodal decomposition parameters, ANPG models with preferentially aligned ligaments and INPG with random ligament orientation are constructed, spanning relative densities from 0.30 to 0.50. The ligament length and diameter of ANPG along the out-of-plane direction are twice those along other directions. Molecular dynamics simulations of tensile tests show that ANPG exhibits superior out-of-plane Young’s modulus and yield strength but reduced fracture strain compared to INPG. Crucially, ANPG maintains toughness comparable to INPG at relative densities below 0.4, offering an optimal strength-toughness balance for practical applications. Scaling law analysis demonstrates INPG follows classical bending-dominated Gibson-Ashby behavior, while ANPG exhibits a hybrid deformation mechanism with significant ligament stretching contribution. Atomic-scale analysis reveals that both structures develop dislocation-mediated plasticity initially, but ANPG transitions to localized ligament necking and fractures more rapidly, explaining its reduced ductility. Strain localization quantification, measured by atomic shear strain standard deviation, confirms the intensifier deformation concentration in ANPG at large plastic strain. These findings suggest anisotropic design as a powerful strategy for developing high-performance NPG for actuators, sensors, and catalytic systems where simultaneous mechanical robustness and functional performance are required. Full article

Single-molecule nanopore sensors have enabled real-time detection of enzymatic cleavage events, yet achieving sensitive and specific analysis of protease activity remains an important challenge for diagnostic applications. We engineered OmpG nanopore constructs incorporating thrombin recognition peptides into loop 6 with varied flexible and negatively charged linkers to optimize accessibility and cleavage. SDS-PAGE gel analysis showed that constructs with the recognition peptide placed after residue D225 and incorporating dual linkers achieved cleavage efficiencies up to 95%, whereas constructs without linkers showed limited cleavage. Single-channel recordings revealed that linker integration modulates pore conductance, with extended loops exhibiting intermediate open-state currents near 18 pA compared to 25 pA in wild-type OmpG. Upon thrombin addition, rapid and irreversible current drops confirmed real-time protease activity detection. These results demonstrate the critical role of linker design, particularly flexibility and charge, in optimizing nanopore protease sensors, providing a versatile platform for biomedical applications. Full article

Nanopores have emerged as powerful tools for single-molecule detection, enabling real-time analysis across diverse applications in genomics and molecular diagnostics. While natural pores laid the foundation for single-molecule detection, their limited diversity has driven advances in protein engineering and, more recently, de novo design to create customizable nanopore sensors. Computational approaches now allow for the design of nanopores with tailored geometries, enhanced stability, and specific molecular recognition functions. Together, these advances are ushering in a new era of programmable nanopore sensors with broad applications in diagnostics and molecular biotechnology. Full article

In this study, we present a cost-effective approach for fabricating nanopores on single-crystal silicon using a silver–alumina–silver (Ag/AAO/Ag) metal–insulator–metal (MIM) structured mask. Self-ordered porous anodic aluminum oxide (AAO) films were prepared via two-step anodization and coated with silver layers on both sides to form the MIM structure. When irradiated with a 532 nm nanosecond laser, the MIM mask excites surface plasmon polaritons (SPPs), resulting in a localized field enhancement that enables the etching of nanopores into the silicon substrate. This method successfully produced nanopores with diameters as small as 50 nm and depths up to 28 nm. The laser-induced SPP-assisted machining significantly enhances the specific surface area of the processed surface, making it promising for applications in catalysis, biosensing, and microcantilever-based devices. For instance, an increased surface area can improve catalytic efficiency by providing more active sites, and enhance sensor sensitivity by amplifying response signals. Compared to conventional lithographic or focused ion beam techniques, this method offers simplicity, low cost, and scalability. The proposed technique demonstrates a practical and efficient route for the large-area subwavelength nanostructuring of silicon surfaces. Full article

NO₂ is a toxic gas mainly generated by combustion processes, such as vehicle emissions and industrial activities. It is a key contributor to smog, acid rain, ground-level ozone, and particulate matter, all of which pose serious risks to human health and the environment. Conventional resistive gas sensors, typically based on metal oxide semiconductors, detect NO₂ by resistance modulation through surface interactions with the gas. However, they often suffer from low responsiveness and poor selectivity. This study investigates NO₂ detection using nanoporous zinc oxide thin films integrated into a resistor structure and floating-gate field-effect transistor (FGFET). Both Silvaco-Atlas simulations and experimental fabrication were employed to evaluate sensor behavior under NO₂ exposure. The results show that FGFET provides higher sensitivity, faster response times, and improved selectivity compared to resistor-based devices. In particular, FGFET achieves a detection limit as low as 89 ppb, with optimal performance around 400 °C, and maintains stability under varying humidity levels. The enhanced performance arises from quantum well effects at the floating-gate Schottky contact, combined with NO₂ adsorption on the ZnO surface. These interactions extend the depletion region and confine charge carriers, amplifying conductivity modulation in the channel. Overall, the findings demonstrate that FGFET is a promising platform for NO₂ sensors, with strong potential for environmental monitoring and industrial safety applications. Full article

Dealloying technique has been used for centuries as an attractive method for producing porous surfaces by removing one or more undesirable elements from the surface. Since early 2000s, the technique has been further developed for understanding the dealloying mechanism and tailoring it to produce chemically homogeneous materials with nanoporous (np) morphology. Dealloying has found numerous applications such as sensors, catalysts, as well as in the biomedical field, which is fairly recent and has attracted great attention on this topic. This review investigates the dealloying technique for preparing nanoporous materials and nanoporous surfaces by using different modification routes on various types of Ti-based alloys for biomedical implant application. There has been significant growth in studying dealloying of crystalline, amorphous, shape memory, and composites-based Ti alloys. This review aims to summarise the findings from literature and discuss the scope of this technique and challenges involved for future aspects. Full article

The anodization of aluminium/aluminium alloys is widely used to produce anodic nanoporous networks for metal layered structures, with applications in energy harvesting technologies and sensor systems. Anodic aluminium oxide (AAO) with thickness of ~10 μm and average pore diameter of 13, 33, and 95 nm is prepared by tuning acids and voltages, being further used for electroless nickel deposition, performed for 10 min using conventional electrolyte with sodium hypophosphite reductor and pH 4.5. The formation of Ni nanotubes or nanorods is found to be strongly dependent on AAO pore size. Ni is detected in the whole pore depth and found to form 5–7 μm long continuous tube-like structures only in AAO with pore diameter of 95 nm, being kept just on the AAO top for smaller pore diameters. Nickel distribution in pores along cross-section of AAO is studied as well revealing continuously decreasing ratio to phosphorus amount. The magnetic properties of the resulting Ni 3D structure of a flat conductive layer and nanotubes perpendicular to it do not show significant differences in parallelly and perpendicularly oriented magnetic fields. These observations are discussed considering possible formation mechanisms for an electroless deposited Ni layer on AAO with different structures. Full article

The detection of trace chemicals at low and ultra-low concentrations is critical for applications in environmental monitoring, medical diagnostics, food safety and other fields. Conventional detection techniques often lack the required sensitivity, specificity, or cost-effectiveness, making real-time, in situ analysis challenging. Surface-enhanced Raman spectroscopy (SERS) is a powerful analytical tool, offering improved sensitivity through the enhancement of Raman scattering by plasmonic nanostructures. While noble metals such as Ag and Au are currently the reference choices for SERS substrates, fabrication methods should balance enhancement efficiency, reproducibility and scalability. In this study, we propose a novel approach for SERS substrate fabrication using reactive Aerosol Jet Printing (r-AJP) as an innovative additive manufacturing technique. The r-AJP process enables in-flight Ag seed reduction and nucleation of Ag nanoparticles (NPs) by mixing silver nitrate and ascorbic acid aerosols before deposition, as suggested by computational fluid dynamics (CFD) simulations. The resulting coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses, revealing the formation of nanoporous crystalline Ag agglomerates partially covered by residual matter. The as-prepared SERS substrates exhibited remarkable SERS activity, demonstrating a high enhancement factor (10⁶) for rhodamine (R6G) detection. Our findings highlight the potential of r-AJP as a scalable and cost-effective fabrication strategy for next-generation SERS sensors, paving the way for the development of a new additive manufacturing tool for noble metal material deposition. Full article

With the evolution of micro/nanotechnology, anodic aluminum oxide (AAO) has received attention for sensor applications due to its regular and high-aspect-ratio nanopore structure with an excellent sensing performance, especially for electrical and optical sensors. Here, we propose the application of these capacitance and porous properties in a facile nanoporous AAO liquid sensor and study an efficient and economical method for preparing AAO substrates for liquid-phase substance sensing. By applying hybrid pulse anodization (HPA), a growth rate of approximately 5.9 μm/h was achieved in AAO fabrication. Compared to traditional low-temperature (0–10 °C) and two-step anodization with a growth rate of 1–3 μm/h, this process is significantly improved. The effect of pore widening on the performance of electrical sensors is also investigated and discussed. After pore widening, the capacitance values of AAO for air as a reference and various liquids, namely deionized water, alcohol, and acetone, are measured as 3.8 nF, 295.3 nF, 243.5 nF, and 210.1 nF, respectively. These results align with the trend in the dielectric constants and demonstrate the ability to clearly distinguish between different substances. The mechanism of AAO capacitive liquid-phase sensors can mainly be explained from two perspectives. First, since an AAO capacitive sensor is a parallel capacitor structure, the dielectric constant of the substance directly influences the capacitance value. In addition, pore widening increases the proportion of liquid filling the structure, enabling the sensor to clearly differentiate between substances. The other is the affinity between the substance and the AAO sensor, which can be determined using a contact angle test. The contact angles are measured as values of 93.2° and 67.7° before and after pore widening, respectively. The better the substance can fully fill the pores, the higher the capacitance value it yields. Full article

Calcium ion sensors are essential in clinical diagnosis, particularly in the management of chronic kidney disease. Multiple approaches have been developed to measure calcium ions, including flame photometry and ion chromatography. However, these devices are bulky and require specialized staff for operation and evaluation. The integration of all-solid-state ion-selective determination allows the design of miniaturized and low-cost sensing that can be used for the continuous monitoring of electrolytes. However, clinical use has been limited due to the low electrochemical stability and selectivity and high noise rate. This manuscript reports for the first time a novel miniaturized Ca²⁺ ion-selective sensor, developed by using a two-layer nanocomposite thin film (5 µm thick). The device consists of functionalized silica nanoparticles embedded in a poly(vinyl chloride) (PVC) film, which was deposited onto a nanoporous zirconium silicate nanoparticle layer that served as the sensing surface. Systematic evaluation revealed that perfluoroalkane-functionalized silica nanoparticles enhanced Ca²⁺ selectivity by minimizing K⁺ diffusion, confirmed by both potentiometric measurements and quartz microbalance studies. The final sensor demonstrated a super-Nernstian sensitivity of 37 mV/Log[Ca²⁺], a low signal drift of 28 µV/s, a limit of detection of 1 µM, and exceptional selectivity against Na⁺, K⁺, and Mg²⁺ ions. Long-term testing showed stable performance over three months of continuous operation. Clinical testing was conducted on patients with chronic kidney disease. An accurate real-time monitoring of electrolyte dynamics in dialysate samples was observed, where final concentrations matched those observed in physiological conditions. Full article