ACS Measurement Science Au最新文献

Main techniques for pathogen detection include molecular or nucleic acid-based methods, such as polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP). Among these, chip-based LAMP provides a particularly promising platform for point-of-care diagnostics. To ensure accurate, reliable, and robust pathogen detection, systematic optimization of the LAMP-chip system is essential. Building on our previously developed LAMP-chip platform, we report a systematically advanced version for the rapid and sensitive detection of Phytophthora infestans. By systematically investigating the effects of primer concentrations, immobilization ratios, and reaction conditions, we identified an optimal configuration involving immobilized forward inner primers (FIP) on the sensor surface and unmodified backward inner primers (BIP) in solution. This approach enabled the detection of P. infestans DNA at concentrations as low as 1 fg/μL, with a transducing optical signal shift of up to 4.33 nm after a 30 min reaction. Further refinement reduced detection time to under 20 min, a 33% reduction of conventional LAMP detection time, without compromising sensitivity. Notably, the use of EDC-NHS chemistry for primer immobilization on the anodic aluminum oxide (AAO) nanopore surface of the LAMP chip effectively minimizes carryover contamination by strictly confining amplification to the chip, representing a major advance over conventional LAMP approaches. This robust, label-free, and user-friendly system offers a promising solution for point-of-care plant pathogen diagnostics, enabling accurate and rapid field-based detection to support timely disease management and improve agricultural outcomes.

Measuring refractive index (RI) changes of liquid samples is central to many sensing applications including flow injection analysis, liquid chromatography, biosensing and photothermal spectroscopy. Commercial refractive index detectors optimized for liquid chromatography suffer from a limited linear range and measurement rate, restricting their use largely to separation sciences. In contrast, microring resonators (MRR) integrated with low-volume microfluidics, offer enhanced performance by minimizing sample dilution during flow-through RI measurements and increased dynamic range. MRRs realized by modern photonic integrated circuitry (PIC) technology also have the potential to be used as transducers in more advanced sensing schemes. Here, we demonstrate a silicon nitride (Si₃N₄) MRR integrated into a low-volume microfluidic system as a compact, chip-scale RI detector capable of real-time operation under dynamic flow conditions. Two interrogation modalities were experimentally compared for flow-through liquid sensing using the same MRR for the first time: resonance wavelength scanning for wide-range refractive index detection, and fixed-wavelength probing on the resonance slope for high-speed measurements. Using glucose solutions as test samples, the device was benchmarked against a commercial RI detector, achieving a sensitivity of 113 nm/RIU and a sLOD of 2.3 × 10^-6 RIU (0.014 g/L glucose). To demonstrate the applicability of the developed RI-sensor for resolving transient RI peaks in realistic chromatographic flow conditions we also report its successful use in an isocratic separation of four sugars (sorbitol, fructose, glucose, and sucrose). These results highlight the potential of integrated Si₃N₄ MRRs as versatile, miniaturized transducers for quantitative, high-speed RI sensing in flow-based analytical systems.

Noninductive magnetometers based on nitrogen-vacancy centers in diamond offer a promising solution for small-volume nuclear magnetic resonance (NMR) detection. A remaining challenge is to operate at a sufficiently high magnetic field to resolve chemical shifts at the part-per-billion level. Here, we demonstrate a Ramsey-M _z protocol that uses Ramsey interferometry to convert an analyte's transverse spin precession into a longitudinal magnetization (M _z ), which is subsequently modulated and detected with a diamond magnetometer. We recorded NMR spectra at B ₀ = 0.32 T with a fractional spectral resolution of ∼350 ppb, limited by the stability of the electromagnet bias field. We resolve the chemical shift structure of ethanol with negligible distortion. Based on the laser illumination volume within the diamond (∼0.9 nL), we calculate an effective analyte detection volume of ∼1 nL. Through simulation, we show that the protocol can be extended to fields up to B ₀ = 3 T, with minimal spectral distortion, by using composite nuclear-spin inversion pulses. For subnanoliter analyte volumes, we estimate a resolution of ∼1 ppb and a concentration sensitivity of ∼40 mM s^1/2 are feasible with improvements to the sensor design. Our results establish diamond magnetometers as high-resolution NMR detectors in the moderate magnetic field regime, with potential applications in metabolomics and pharmaceutical research.

Several reports have been published on the detection of the carbohydrate antigen 125 (CA125) cancer biomarker, where the immunoassay is completed with a molecule tag that is detected via surface-enhanced Raman scattering (SERS); however, it is still challenging to detect protein biomarkers without a Raman reporter. In this study, a SERS substrate based on zinc oxide nanorods (ZnO NRs) decorated with silver nanoparticles was fabricated, functionalized, and bioconjugated to detect CA125. Functionalization was performed by using an MPA self-assembled monolayer, which was subsequently surface-activated with an EDC/NHS solution. This process was optimized by using Raman measurements to determine the surface protonation of the substrate. The effect of the concentration and incubation time of the CA125 antibodies on the bioconjugation of the substrate were evaluated. SERS detection of CA125 was successfully achieved in a concentration range of 15-1000 U/mL, demonstrating performance comparable to the ELISA approach. A vibration mode at 829 cm^-1 associated with proline and tyrosine was identified and exhibited excellent linearity with CA125 concentration. A limit of detection (LoD) of 14 U/mL was estimated. This report confirms the potential of Ag/ZnO NR substrates for developing SERS assays for tumor marker detection using a portable Raman spectrometer.

We present a flexible gear rod-based magnetic field cycling (MFC) system for high-resolution NMR spectrometers. The system enables the transfer of the sample from the NMR B ₀ field of 9.4 T to ∼nT and all fields in between within 1 s. A flexible gear rod was essential for reducing the total height to approximately the height required for filling the NMR with liquid helium. Due to its reduced height, it can be installed in average-size NMR laboratories (the height of the NMR with MFC is only 3.32 m). Only off-the-shelf components and 3D-printed parts were used for the system assembly, lowering the costs for replication. An automated shimming procedure for ultralow fields is presented to achieve homogeneous fields of a few nanotesla. The system utility is exemplified by measuring T ₁ relaxation dispersion of the most common liquid state hyperpolarization tracer[1-¹³C]-pyruvateand magnetic field dependences of signal amplification by reversible exchange, enabling alignment transfer to heteronuclei (SABRE-SHEATH) hyperpolarization of [¹⁵N]-pyridine. Using the system, we uncovered the exact relaxation dispersion of pyruvate for a standard preclinical dDNP sample composition and provided quantitative estimates for the retained polarization after sample transfer. We modified the observation protocol of SABRE-SHEATH polarization, which, with the high reproducibility of the MFC, provided us with a method to measure the chemical exchange rates of hyperpolarized compounds.

Metastatic disease is the most severe complication in oncological patients. The quantification of cellular invasion into the surrounding tissue is crucial for the identification of strategies to suppress this process. Extracellular matrix-embedded 3D cancer models, such as spheroids and organoids, are commonly used to mimic tumor progression under in vitro conditions. However, robust and widely used algorithms to detect and quantify spheroid growth and invasion into the surrounding matrix are still lacking. In this study, we use fluorescently labeled 3D models, as fluorescence images are generally of higher quality than bright-field images. We present a methodology to compute the mask of the spheroid core and to detect and characterize cells outside this mask. We have developed two strategies for mask computation, one for compact spheroids and another for models that lose their boundaries soon after insertion into the extracellular matrix. In both modes, masks can be created for spheroids of various shapes. Cells or their clusters outside the mask are recognized on the basis of filtered local maxima. This method enables the analysis of images with a nonconstant background, which is often found in real fluorescence images. The evaluation is largely automated but allows visual inspection based on the overlay of the objects detected by the algorithm with the original fluorescence signal of the spheroid core and the invading cells. A user-friendly manual adjustment of the parameters for mask fitting and cell detection is implemented.

We present a tutorial to guide users on how to extend the Computational Reverse Engineering Analysis of Scattering Experiments-2D (CREASE-2D) framework to interpret their experimental two-dimensional small-angle scattering (SAS) data from soft materials (e.g., polymers, peptide amphiphiles, biomolecular fibrils). Unlike most traditional SAS analysis approaches, which typically rely on azimuthally averaged one-dimensional (1D) profiles, CREASE-2D utilizes the complete 2D scattering profile to reveal information about anisotropy in the structure. In past applications, CREASE has provided insights into complex structural features, including the cross-sectional shapes of assembled nanostructures and dispersity in these features, which are difficult to discern with existing analytical models. While (1D-) CREASE has been applied to SANS and SAXS data, this tutorial shares the steps for implementing CREASE-2D using an example of a dipeptide solution system, for which we have SAXS data. We present details for these steps involved in using CREASE-2D to interpret SAXS profiles: how to preprocess SAXS data, define relevant structural features, generate three-dimensional real-space structures for specific values of these features, train a machine learning (ML) surrogate model to predict scattering profiles for given structural features, and optimize these features using genetic algorithms (GA). Then, we use these steps to interpret complex 2D-SAXS data collected from dipeptide solutions that, in microscopy images, exhibit nanoscale structures that could be elliptical tubes/flat tapes/cylinders or a combination of these cross sections. Open-source codes, computational hardware, and software requirements, as well as the strengths and limitations of this protocol, are also presented. We expect researchers working with (soft) biomaterials, peptide amphiphiles, amphiphilic polymer solutions, polymer nanocomposites, and blends of particles/polymers will find this CREASE-2D method and this tutorial of use.

A portable electrochemical aptasensor was fabricated using a nanocomposite (Silver Bismuth Sulfide/Carbon Nanosphere, AgBiS₂/CNS) for the targeted detection of the cancer biomarker carcinoembryonic antigen (CEA). The prepared nanocomposite provides a higher specific surface area, electrical conductivity, and tunable functionality, which enable more effective aptamer immobilization compared to conventional electrode materials. The aptamer, known for its chemical stability and robust surface binding, was immobilized on the surface-treated screen-printed carbon electrode (SPCE), thereby enhancing the reproducibility and stability of the sensor platform. The fabricated portable sensor demonstrated the ability to detect CEA in an early stage with high sensitivity and selectivity. Quantification and optimization were performed using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) in 0.05 M phosphate buffer solution (PBS, pH 7.0) with 0.1 M KCl [Fe-(CN)₆]^3-/4- (5 mM) electrolyte system. The lower limit of detection (LOD) for CEA was found to be 7.6 ng mL^-1. Practical applicability was confirmed by evaluating human serum samples, achieving recovery rates in the range of 98.06% to 99.69%.

Hydrogels have emerged as a versatile platform technology for analyte sensing, offering unique advantages in tunable chemistry, for loading with sensors across multiple length scales, and biocompatibility. These smart materials undergo predictable changes in optical properties, conductivity, swelling, and porosity upon analyte interaction, enabling their function as biosensors. While hydrogels can respond to a variety of stimuli, their responses are most effectively quantified through optical and electrical readouts, which enable direct, real-time, and quantitative sensing in complex biological fluids. Optical approaches leverage fluorescence, chemiluminescence, and colorimetry, whereas electrical approaches leverage conductive fillers or redox-active groups. Hybrid platforms integrate multiple readout mechanisms, enhancing sensitivity, robustness, and multiplexing capabilities. Many of these systems were validated in various biological matrices, such as interstitial fluid, sweat, and wound exudates. Beyond technical advances, we discuss translational challenges including selectivity, stability, nonreversibility, signal standardization, device portability, and regulatory approval, as well as emerging opportunities in coupling hydrogel sensors with artificial intelligence for improved data interpretation and clinical integration. Together, these developments position hydrogel-based diagnostics as promising candidates for next-generation, real-time, point-of-care biosensing.

Actinomycin D (ActD), a potent anticancer drug, binds specifically to DNA at GpC-rich sites through intercalation and minor groove interactions. Detecting trace levels of ActD in complex biological fluids, such as human serum, is crucial for clinical, environmental, and pharmaceutical applications. Herein, we report a label-free detection method using an engineered α-hemolysin (α-HL) nanopore. In this assay, ActD binds to a ssDNA probe (GC₂), enriched with GpC sites, forming GC₂-ActD complexes that generate current modulations with distinct signatures from those of GC₂ alone. This sensor achieves high sensitivity, with a detection limit (LOD) of 1.20 nM, and a broad linear range of 2.5-250 nM. The sensor selectivity and the effects of metal ions and salt concentration on its performance were further evaluated. Moreover, this sensor enabled ActD detection in complex human serum samples with high selectivity. Overall, this DNA-based nanopore platform offers a powerful, label-free tool for drug screening and discovery.