Sensors & diagnostics最新文献

A graphical abstract is available for this content

Circulating cell-free DNA (cfDNA) has been established as a minimally invasive liquid biopsy biomarker with utility in the diagnosis of cancer, monitoring of treatment response, and detection of minimal residual disease. The clinical utility of cfDNA is currently constrained by the low abundance of circulating cfDNA fragments, high fragmentation rates, and short half-life, making it technically challenging to detect in a patient sample. Current molecular approaches for cfDNA detection, including ddPCR and NGS, are time-intensive, expensive, and unsuitable for low-resource settings and point-of-care testing. The CRISPR-Cas system offers a novel and operationally simple approach to cfDNA detection by being single nucleotide specific and compatible with isothermal and amplification-free workflows. In this review, we discuss CRISPR-based assays for cfDNA, beginning from Cas9 enrichment-type assays to promising collateral cleavage platforms employing Cas12a and Cas13a that have countered traditional bottlenecks concerning diagnostic testing. We also provide a comparative analysis of the emerging platforms for key cancer mutations with a discussion around translational scope, including implications from CRISPR-based diagnostic patents. The convergence of sensitivity, speed, multiplexing, and microfluidic integration of CRISPR diagnostics will undoubtedly constitute a next-generation approach for cfDNA analysis, presenting a great promise in impacting precision oncology and increasing access to cancer diagnostics across low-resource settings.

Conjugated microporous polymers (CMPs) possess extended π-conjugation combined with microporosity, enabling amplified sensing response even with ultra-trace solution or vapor-phase analytes, and their high sensing response output was demonstrated with several CMPs. However, CMPs exhibiting tandem detection properties, i.e., sequential detection of multiple analytes, are rarely reported and represent the next generation of CMP chemical sensors offering enhanced sensitivity and specificity. Herein, we report the design and synthesis of a salphen-conjugated microporous polymer (pTPE-salphen) for reversible dual-mode (fluorometric/colorimetric) nanomolar detection of Cu²⁺ ions and tandem capture of cysteine (Cys). pTPE-salphen synthesized via Schiff-base condensation between 1,1,2,2-tetrakis(4-hydroxy-3-formylphenyl)ethene and o-phenylenediamine, emits yellow photoluminescence (PL) at λ^max_Em = 537 nm with a PL quantum yield of 5.41%. pTPE-salphen exhibited remarkable thermal stability up to 425 °C and a fused spherical nanoparticle morphology. pTPE-salphen showed strong PL quenching up to 92% when exposed to Cu²⁺ (50 μM), selectively among other metal ions, due to the ground-state complex formation of Cu²⁺@pTPE-salphen. pTPE-salphen was highly sensitive to Cu²⁺ with a detection limit of 5.69 nM and exhibited a high Stern–Volmer constant (K_SV) value of 8.12 × 10⁶ M⁻¹. Notably, the pTPE-salphen-based paper strip sensor showed appreciable sensitivity up to 10⁻¹¹ M Cu²⁺. In addition, strong colorimetric changes from yellow (R/B is 1.9) to black (R/B is 0.53) were also observed upon the formation of Cu²⁺@pTPE-salphen, and the binding of Cu²⁺ was confirmed by XPS analysis. Interestingly, Cu²⁺@pTPE-salphen exposed to cysteine (Cys) exhibited reversible colorimetric response from black to orange (R/B is 1.8) both in dispersion and paper strip sensors due to the formation of Cys–Cu²⁺@pTPE-salphen where Cys binds with Cu²⁺ anchored on the pore surface of pTPE-salphen, and the entire colorimetric process (yellow ⇌ black ⇌ red) is reversible. The binding of Cys to Cu²⁺ and its tandem capture were systematically studied using XPS and NMR. Such sequential detection and capture (tandem process) of Cu²⁺ and Cys using a conjugated microporous polymer sensor is unique and of high significance in environmental and biological applications.

Few point-of-care (POC) molecular methods exist that are as sensitive as polymerase chain reaction (PCR) while maintaining the simplicity, portability, and robustness for detecting specific nucleic acids in complex sample media. Here, we developed an isothermal nonenzymatic amplification cascade, named sequential nonenzymatic amplification (SENA), and its digital assay version (dSENA), for the ultrasensitive detection of cell-free microRNAs (miRNAs) in diluted human serum with a >95% recovery rate. SENA consists of two layers of DNA circuit-based amplifiers, in which the hybridization chain reaction (HCR) and catalyzed hairpin assembly (CHA) were concatenated to amplify the signals by more than 4000-fold. The sensitivity was further improved in dSENA, where a limit of detection (LOD) down to 5 fM was achieved under the optimized conditions. SENA and dSENA together demonstrated a broad detection dynamic range over 6 logs of analyte concentrations (10 fM – 10 nM), and high specificity for discriminating target miRNAs from point mutations and other interference sequences. dSENA was demonstrated to quantify expression levels of miR-21 and miR-92 in colorectal cancer patient serum with accuracy comparable to RT-PCR. Given its simplicity, compactness, and PCR-like performance, SENA holds great potential in POC miRNA or ssDNA analysis.

Developing nanozyme-based sensors enables the upcycling of waste printed circuit boards (WPCBs) into functional sensing materials, offering both environmental sustainability and practical analytical capabilities. However, unlike natural enzymes with inherent target recognition, nanozymes often lack molecular selectivity, limiting their broader sensing applications. Moreover, developing waste-derived nanozymes with target recognition abilities presents considerable obstacles due to their uncontrolled and underexplored surface functionalities. In this study, we developed pyrophosphate (PPi)-responsive carbon nanozymes (CNZs) derived from WPCBs and investigated their intrinsic target-binding behavior. The peroxidase-mimicking CNZs were synthesized via simple carbonization of non-metallic fractions of WPCBs, followed by refluxing in alkaline solutions. Notably, the peroxidase-mimicking activity of CNZs was significantly suppressed by PPi, an important anionic biomarker in physiological processes and disease monitoring. Kinetic studies and comparative assays revealed the inhibition mechanism underlying the unique interaction between PPi and WPCB-derived CNZs. Upon the H₂O₂–CNZ complex formation, PPi subsequently interacts with the active carbonyl sites (CO) on the CNZ surface, resulting in target-responsive inhibition. Built upon this unique binding behavior, the CNZ-based system achieved highly sensitive and selective colorimetric PPi sensing with a detection limit of 8.7 nM, with negligible interference even from structurally similar phosphate analogs. This work not only demonstrates the feasibility of converting waste into functional enzyme mimics, but also highlights a strategy for achieving intrinsic molecular selectivity in nanozyme-based sensors without relying on external recognition elements.

The rate-limiting step in a recently reported glucose sensor strip incorporating a water-soluble quinone mediator with high enzyme reactivity was proposed to be substrate diffusion. This mechanism is expected to lead to sensors requiring smaller mediator amounts but possessing higher sensitivity and a wider measurement range than conventional sensor strips containing mediators with low enzyme reactivity. A general finite element method-based simulation model for mediator-type enzyme electrodes was employed in this study to obtain the concentration distribution profiles of this specific glucose sensor strip and clarify its action mechanism. The obtained profiles showed that the mediator forms a very thin diffusion layer on the electrode surface and that the diffusion layer of the substrate gradually covers the entire solution. The results of this study confirmed that the rate-limiting step of the glucose sensor strip is substrate diffusion.

Co(II) and Cr(III) salicylidene Schiff base-based complexes as novel ionophores were evaluated for the fabrication of bromide-selective electrodes. By incorporating a cation excluder along with various plasticizers (dibutyl phthalate, dioctyl phthalate, 1-chloronapthalene), optimized sensors (CoC7 and CrC7) exhibiting near-Nernstian slopes being 59.4 ± 0.07 and 59.2 ± 0.04 mV decade⁻¹, with a broad linear range (1 × 10⁻² to 6.0 × 10⁻⁷ and 1 × 10⁻² to 8.7 × 10⁻⁷ mol L⁻¹), with low detection limits (5.5 ± 0.13 × 10⁻⁷ and 6.5 ± 0.07 × 10⁻⁷ mol L⁻¹) respectively, were successfully designed. Selectivity coefficient values of order 10⁻¹ or less indicate that the proposed electrodes have superior selectivity for bromide ions over various interfering anions. The developed bromide electrodes demonstrated robust performance within a pH range of 4.0 to 9.0, as well as showing a sufficient shelf life (4 and 5 weeks) with up to 20% (v/v) non-aqueous tolerance and quick response times (12 and 16 s). These electrodes also served as indicator electrodes in the potentiometric titration of bromide ions against AgNO₃ and were used in the determination of bromide ion concentration in water samples.

To address the problems linked with Mycobacterium tuberculosis (MTB) detection, we need an accurate, sensitive, and rapid detection method for efficient epidemiological management of tuberculosis (TB). Nucleic acid-based diagnosis of TB is more sensitive and specific but primarily requires trained workers and costly infrastructure. Isothermal amplification methods have paved the way for efficient and rapid diagnosis of TB due to their negligible infrastructure requirements; however, they sometimes suffer from drawbacks such as false-positive results and challenges in primer design. With progress in clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein (Cas)-integrated nucleic acid detection methods, the above limitations are being overcome in pathogen detection. The combination of CRISPR with any suitable isothermal amplification techniques such as recombinase polymerase amplification (RPA) or loop-mediated isothermal amplification (LAMP) offers several advantages due to its higher sensitivity, specificity, versatility and reproducibility as a point-of-care detection technique. Thus, in this systematic review, we aimed to provide a comprehensive overview of the various isothermal amplification methods coupled with CRISPR-based TB diagnostic studies that are reported in the literature. About 12 articles were included in this review using predefined selection criteria. Data were extracted for detailed review from PubMed, Google Scholar and ScienceDirect, and diagnostic efficiency was evaluated. The data uncovered that most of the studies were conducted in China, with IS6110 and IS6108 as the major target genes employed. The most used detection methods were based on fluorescence and lateral flow. Analytical sensitivity, defined by the limit of detection, ranged between 10 and 20 copies per μL. Diagnostic sensitivity and specificity were consistently high, ranging from 95 to 100%. Taken together, the synergy between isothermal amplification methods and CRISPR-Cas technique could serve as a potential alternative to qPCR, GeneXpert, and conventional acid-fast staining, particularly in low-resource regions for easy and rapid TB diagnosis.

Methotrexate (MTX) is a widely used chemotherapeutic drug with a narrow therapeutic index, making its precise monitoring crucial for effective treatment and minimizing side effects. This study focuses on the development of a clinically applicable NiMn₂O₄/CNT nanocomposite-modified glassy carbon electrode (NiMn₂O₄/CNT-GCE) for the sensitive and selective electrochemical detection of MTX. The NiMn₂O₄ nanomaterial was synthesized via a co-precipitation method followed by calcination, and its composite with CNTs was optimized to enhance electrochemical performance. The sensor demonstrated a detection limit as low as 0.627 nM and a broad linear detection range (0.05–3 μM), attributed to the synergistic effects of NiMn₂O₄ and CNTs that enhance electron transfer and active site availability. Moreover, the NiMn₂O₄/CNT-GCE was successfully applied to detect MTX in spiked serum and urine samples, achieving recovery rates of 96–99% with relative standard deviations below 3.5%. Its minimal interference with common metabolites and excellent stability makes it ideal for therapeutic drug monitoring. This work underscores the potential of NiMn₂O₄/CNT as a promising platform for real-time clinical diagnostics and advanced electrochemical sensing applications.

In recent times, pressure sensors developed from e-textiles have gained tremendous attention due to their flexibility, comfort, real-time detection, and potential for long-term applications when integrated with monitoring devices. The current research focuses on designing a capacitive pressure sensor comprising a porous textile substrate for electrodes and a porous textile-based dielectric layer. A solution processing approach was used to formulate a graphene nanoplatelet/nickel ferrite (GNP–NiFe₂O₄) composite, and the dip-coating technique was utilized to coat the sensing layer on pure cotton and cotton–polyester fabric. The coated fabric was integrated as a dielectric layer above the interdigitated capacitor to observe the capacitance variation under applied pressure. Additionally, the effects of the volume percentage of GNPs in GNP–NiFe₂O₄ and the fabric type on the sensor performance were also considered. The highest sensitivity was obtained for the cotton/polyester textile coated with 10 wt% GNP–NiFe₂O₄. The proposed pressure sensor can reach the linear band in the range from 11 kPa to 100 kPa, making it suitable for pressure sensing in cases of physical impact. Furthermore, a large-area, wireless array of six pressure sensors has been fabricated from the optimized dielectric textile coated with GNP–NiFe₂O₄. The change in the pressure range due to multiple sensors can be monitored on a smartphone, enabling real-time applications in monitoring human body motion, human tactile sensing, or any external pressure in cases of gait or grip.