Search Results (117)

Chronic kidney disease (CKD) is a progressively worsening condition that erodes renal function over time, reduces quality of life, and can ultimately culminate in kidney failure with far-reaching systemic complications. In addition to reduced filtration, worsening kidney function disrupts mineral homeostasis and leads to CKD–mineral and bone disorder (CKD-MBD). Dysregulated calcium handling and maladaptive endocrine responses contribute to bone pathology and increase cardiovascular calcification risk; therefore, serial calcium monitoring remains clinically relevant for longitudinal CKD management. Conventional calcium measurements are typically obtained with centralized analyzers or laboratory assays (e.g., colorimetry and electrode/optical readouts). Despite high accuracy, the required instrumentation, controlled operating conditions, and pretreatment steps complicate rapid point-of-care deployment, especially when only microliter-scale biofluids are available. Accordingly, this study develops a finger-actuated microfluidic colorimetric platform capable of determining calcium ion concentrations in human biofluids, such as whole blood, serum, and urine. The platform integrates a three-dimensional PMMA/paper microchip with a compact reader that maintains stable temperature control while enabling CMOS-based optical detection. With just 6 μL of sample, a brief finger press propels the biofluid across an internal filtration layer, generating serum or cleaned urine that subsequently reacts with a pre-deposited murexide reagent. Under optimized conditions (1.6% reagent, 50 °C, 3 min), the signal follows a strong logarithmic relationship with calcium concentration (Y = 47.273 ln X + 28.890; R² = 0.9905), supporting quantification over 1–40 mg/dL and a detection limit of 0.2 mg/dL. Across 80 clinical CKD specimens spanning serum, whole blood, and urine, results aligned closely with the NM-BAPTA reference assay, with R² values exceeding 0.97. Full article

Sodium hypochlorite (NaClO) is frequently utilized in food processing. More than 90% of Salmonella spp. isolates from poultry supply chains exhibited tolerance to NaClO, with MIC values exceeding 256 mg/L. Exposure to NaClO disinfection may lead to the emergence of bacterial tolerance to chlorine, which is frequently associated with antibiotic cross-resistance. This work employed a resazurin-based assay for rapid evaluation of the NaClO chlorine tolerance of Salmonella. The results were compared to the broth microdilution method for assessing bacterial tolerance. At the initial inoculum of 10⁷ CFU/mL, NaClO tolerance was successfully identified via colorimetry within 2 h. Notably, the fluorescence-based evaluation yielded significant results even sooner, showing a marked increase in intensity within 1 h of resazurin incubation. Even with an inoculum of 10⁵ CFU/mL, the resazurin-based method determines NaClO tolerance in just 6 h. Conversely, traditional broth microdilution requires an overnight culture to manifest sufficient turbidity for optical density monitoring. Furthermore, the broth microdilution method revealed NaClO tolerance (MIC > 256 mg/L) in 1.6% (1/64) of the Salmonella isolates. The modified resazurin assay, by contrast, detected tolerance in 6.3% (4/64) of isolates. The reference that differentiates between resistant and sensitive strains was 3.2 × 10⁵ RFU. When the strains exhibited an MIC value of 256 mg/L, the fluorescence intensity varied from around 1.2 × 10⁵ to 4 × 10⁵ RFU, reflecting inactivation effects at practical chlorine concentrations. This methodology is recognized as a rapid, high-throughput, and quantitative screening approach for assessing bacterial chlorine resistance. Full article

Excessive molybdenum (VI) (Mo (VI)) in water threatens environmental safety and human health, yet rapid on-site methods for Mo (VI) determination remain limited. Here, we propose a rapid method for Mo (VI) determination using phenylfluorone (PF)-modified test strips with dual readouts: visual colorimetry and image-based analysis in the CIELAB (Lab*) color space, and demonstrate its applicability using urban park water samples. Based on visual colorimetry, a standard color card was established, providing a screening range of 0.08 to 0.8 mg L⁻¹ (A blank (0 mg L⁻¹) was used as the baseline reference). Moreover, by the LAB color space, the linear relationship between the color development results of the PF-modified test strip and the A channel conforms to y = 21.08 + 8.82x (R² = 0.992), with a detection range of 0–0.8 mg L⁻¹. The total detection time was reduced to 2.5 min. To evaluate accuracy in real matrices, influent, midstream, and effluent samples from Chengdu Living Water Park were analyzed, with UV-vis spectrophotometry used as the reference method. The test-strip results agreed well with UV-vis spectrophotometry, with relative errors below 5%. Overall, this study provides a portable, rapid, and accurate method for the detection of Mo (VI) in water, and has potential application prospects in the field of water environment detection in the future. Full article

Lupin (Lupinus spp.) is increasingly incorporated into processed foods as a gluten-free ingredient and alternative protein source, but it is also a regulated allergen in the European Union due to cross-reactivity with other legumes, especially peanut. Reliable methods for detecting undeclared lupin traces in complex food matrices are therefore essential for consumer protection. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed for rapid and sensitive detection of lupin DNA. Several nuclear and chloroplast regions were evaluated for primer design, and gene encoding the Lup a 1 allergen was selected as the optimal target. Amplification was monitored by real-time fluorescence, agarose gel electrophoresis, and visual colorimetry. The selected primer set achieved a detection limit of 25 pg of lupin DNA and consistently detected lupin in binary mixtures down to 10 mg/kg, with no cross-reactivity against closely related legumes or tree nuts. Application to processed foods confirmed detection in products declaring lupin and revealed potential undeclared presence in some commercial samples. Colorimetric detection provided reliable results comparable to real-time monitoring, enabling simple readouts without specialized equipment. Overall, the developed LAMP assay represents a rapid, specific, and sensitive alternative to PCR-based methods for allergen monitoring and food safety management. Full article

Chrysanthemum, a traditional medicinal and edible plant, possesses diverse health-promoting properties attributed to its rich profile of bioactive compounds. However, the intrinsic quality, influenced by the composition of fundamental components like starch and lignin, varies significantly across different cultivars and origins. This study establishes a comprehensive phytochemical profile of 12 representative Chinese chrysanthemum cultivars by systematically quantifying their starch and lignin contents. Furthermore, it develops and validates a novel, low-cost rapid detection method for starch utilizing smartphone-based colorimetry. The starch content, determined by a colorimetric anthrone-sulfuric acid assay, ranged from 2.68 to 18.69 g/100 g, while the lignin content, measured via the acetyl bromide digestion followed by UV spectrophotometry at 280 nm, varied from 4.21 to 13.63 g/100 g, revealing substantial inter-cultivar differences. For starch analysis, a low-cost, immediate, general-purpose, and high-throughput (LIGHt) smartphone-based colorimetry was implemented. Standard curves constructed from both absorbance and the LIGHt assay demonstrated excellent linearity (R² > 0.99). The method’s performance was evaluated under different lighting conditions and across various smartphone models. The UV spectrophotometry condenses lignin quantification to a single 30-min digestion–reading cycle, bypassing the two-day Klason protocol and increases efficiency greatly. The work successfully provides a foundational component analysis and validates a portable, high-throughput framework for on-site quality control of plant-based products, demonstrating the strong potential of smartphone-based colorimetry for rapid starch detection and a complementary laboratory-scale lignin assay. Full article

Lapis lazuli is a valued gemstone that displays a wide spectrum of blue hues, yet the quantitative link between its color and internal sulfur speciation remains unresolved. This study integrates colorimetry with electron probe microanalysis and UV-Vis, Raman, and X-ray photoelectron spectroscopy to establish this relationship and build a robust grading framework within the CIE 1976 L*a*b* color space. X-ray diffraction was employed to determine the mineral composition and confirm that the chromogenic elements originated from lazurite. K-means clustering with Fisher’s discriminant validation classifies samples into four grades: Fancy Blue, Fancy Intense Blue, Fancy Deep Blue, and Fancy Dark Blue. Multimodal analyses identify three sulfur species—[S₃]^·−, S²⁻, and ${\mathrm{SO}}_4^{2-}$—and show that higher sulfur content correlates with lower lightness, reduced chroma, and a violetish-blue shift. [S₃]^·− is confirmed as the dominant chromophore, producing the strong 600 nm absorption that defines the blue hue. A weak absorption band observed near 400 nm in some samples can be attributed to S²⁻ and ${\mathrm{SO}}_4^{2-}$ species, but no visually perceptible effect of this band on the overall color was detected. Full article

A polymethacrylate matrix (PMM) is proposed for the solid-phase extraction and determination of tetracycline (TC). The study of the influence of medium acidity, temperature, and contact time on the extraction of tetracycline by PMM showed that tetracycline is extracted by the matrix in the form of a singly charged anion H₂TC⁻, within the pH range of 8.9–9.7, with distribution coefficients reaching (5–6) × 10³ mL/g. Following the extraction process using PMM and PMM-Au⁰, the direct determination of tetracycline in the solid phase is possible without an elution step. This is achieved by using as the analytical signal both the intrinsic absorption and the instrumentally measured peak area of the anionic form of tetracycline, H₂TC⁻, in the matrix, with detection limits of 0.03 and 0.01 mg/L, respectively, and the fluorescence of tetracycline in PMM and PMM-Au⁰, with detection limits of 0.001 and 0.005 mg/L, respectively. The applicability of the digital colorimetry method for the quantitative determination of tetracycline based on its fluorescence in the solid phase is demonstrated. Methodologies for the determination of tetracycline using PMM and PMM-Au⁰ were developed and tested in the analysis of river and bottled water samples, biological fluid, as well as honey and milk samples. Full article

In this study, we developed a rapid method for determining lead(II) by integrating solid-phase extraction with digital image colorimetry to reduce the time and labor required for the analysis of lead(II) in water samples. The solid-phase extraction column was packed with cellulose as a bio-based adsorbent, which facilitated adsorption and enrichment of lead(II) during sample loading. The elution step, which is time-consuming and solvent-intensive, was eliminated from the procedure. An aqueous solution of sodium rhodizonate was added to react with lead(II), forming a red–brown complex. The color intensity was quantified using a smartphone-based digital image colorimetry. The method showed good linearity in the range of 0.01–0.8 mg L⁻¹ with R² > 0.99. In tap, river, and spring water, the recovery was 93.5% to 97.5% with a relative standard deviation of 1.7–4.8%. Five complementary greenness assessment tools confirmed the environmental friendliness of the method. This rapid pretreatment and detection technique can be applied to analyzing lead(II) in aqueous samples. Full article

In recent years, lab-grown diamonds have become more popular in both domestic and international markets for their rich color palette. Research on yellow lab-grown diamonds has primarily focused on spectroscopic and defect characteristics currently, while the study has largely focused on nitrogen content and related color-causing mechanisms, such as NV series defects. However, the relationship between nitrogen content and defects and color is limited. In this study, eight lab-grown diamonds with varying yellow shades were selected as samples to be studied by photoluminescence spectra, infrared spectra, Raman spectra, and colorimetry testing. Based on the colorimetric parameters L*, a*, and b*, the standard formula for the yellowness index, the intensities of the NV⁰ and NV⁻ peaks in the photoluminescence spectra and the absorptivity in the infrared spectra, the hue angle h, the yellowness index YI E313, the concentration ratio of NV⁻ defect in NV color centers R, and the nitrogen content N_C were calculated. Results indicate that characteristic peaks of NV series defects as a specific photoluminescence signature, notably the absence of [Si-V]⁻ defect, demonstrate that the samples are high-temperature, high-pressure diamonds derived from graphite that underwent post-growth irradiation. The specific infrared signature indicates that the type of samples is type Ib, attributed to isolated nitrogen (C aggregate). The intrinsic peak of diamond is detected in Raman spectra, with symmetric stretching vibrations of C and N and the ‘D’ peak of graphite is detected as well. Meanwhile, the yellowness index shows a negative correlation with hue angle, a positive correlation with concentration ratio, and a positive linear correlation with nitrogen content, the equation $y=0.17x+124.40$. The yellowness index is divided into three levels: 70–80, 80–90, and 90–100. The yellow hue of samples is light between 70–80, intense between 80–90, and deep between 90–100. Full article

Most biomarkers exhibit abnormal expression in more than one disease, making conventional single-biomarker detection strategies prone to false-negative results. Detecting multiple biomarkers associated with a single disease can therefore substantially improve diagnostic accuracy. Accordingly, recent research has focused on precise multiplex detection, leading to the development of sensors employing various readout methods, including electrochemical, fluorescence, Raman, and colorimetric approaches. This review focuses on optical sensing applications, such as fluorescence, Raman spectroscopy, and colorimetry, which offer rapid and straightforward detection and are well suited for point-of-care testing (POCT). These optical sensors exploit nanoscale phenomena derived from the intrinsic properties of nanomaterials, including metal-enhanced fluorescence (MEF), Förster resonance energy transfer (FRET), and surface-enhanced Raman scattering (SERS), which can be tailored through modifications in material type and structure. We summarize the types and properties of commonly used nanomaterials, including plasmonic and carbon-based nanoparticles, and provide a comprehensive overview of recent advances in multiplex biomarker detection. Furthermore, we address the potential of these nanosensors for clinical translation and POCT applications, highlighting their relevance for next-generation disease diagnostic platforms. Full article

The presence of hazardous substances in food poses a serious threat to our health. It is important to develop fast, convenient, and inexpensive assays for on-site sensitive analysis of various hazards in food. With the emergence and popularization of aptamers and biosensors, aptasensors have gradually become one of the most important detection techniques for substances such as nucleic acids and small molecules. This paper reviews the recent research progress in the field of aptasensor based on different technologies (such as electrochemistry, fluorescence, colorimetry, among others) for the rapid detection of hazards (such as foodborne pathogens, mycotoxins, pesticides, among others) in food. In addition, the current challenges of different aptasensors are described for the readers, and the future direction of aptasensors is envisioned by comparing the different technologies in order to develop a more suitable aptasensor. This review will not only promote the advancement of aptasensors but also their practical application in daily life to safeguard human health and food safety. Full article

Iodine is an essential element for the synthesis of thyroid hormones. Iodine deficiency leads to a range of health consequences known as iodine deficiency disorders. To assess the iodine nutritional status of a population, urinary iodine (UI) is typically measured. This work introduces a novel and simple analytical method for determining UI using silver triangular nanoplates (AgTNPs) after interfering substances are removed via solid-phase extraction (SPE). The AgTNPs were synthesized and characterized using Transmission Electron Microscopy, UV–vis spectroscopy, and zeta potential measurements. The limit of detection of iodide of the AgTNPs assessed spectrophotometrically was 35.78 µg I⁻/L. However, urine samples interfered with the colorimetric reaction. Thus, an SPE methodology was developed and optimized to eliminate urine interferents that hinder AgTNP performance. A logistic regression analysis was conducted to validate the combined application of SPE and AgTNPs for the qualitative determination of UI. This work demonstrated that the developed SPE methodology eliminates these interferents and extracts iodide from the sample, allowing the accurate determination of UI using AgTNPs. This reliable sample preparation method was then used on actual human urine samples to accurately identify UI deficiency levels. The proposed methodology offers an effective and environmentally friendly approach for monitoring iodine status, without requiring highly complex equipment. Full article

Eutectogels are advanced gel-based systems that integrate deep eutectic solvents (DES) into polymer networks. In this study, we report the first detailed characterization of an enzyme-containing eutectogel, representing a significant step toward advanced biosensing and biocatalytic applications. Specifically, we have incorporated pancreatic lipase, one of the main target enzymes in the treatment of obesity, in eutectogels via UV-induced radical polymerization of suitable precursors in appropriate DESs. Prior to immobilization, the enzyme was solubilized in selected DESs and its activity and conformational stability were evaluated using colorimetry and intrinsic fluorescence. Combinations of choline chloride/glycerol and tetramethylammonium chloride/glycerol were shown to be effective media for preserving and enhancing enzymatic function and conformational stability. The enzyme immersed in eutectogel exhibited high structural integrity and excellent thermal stability, maintaining its activity over several weeks. The ability of this new material to screen enzyme inhibitors was assessed using orlistat, a well-established anti-obesity agent. The results demonstrated clear detection of the drug’s inhibitory effect, even at nanomolar concentrations, highlighting the material’s potential as a screening platform for novel inhibitors with prospective anti-obesity activity. Furthermore, the device proved effective in quantifying drug presence, offering a promising and highly sensitive tool for pharmaceutical quality control applications. Full article

We present a dual-mode optical sensing strategy for selective and sensitive detection of sulfide ions (S²⁻), employing copper-anchored nitrogen-doped graphene quantum dots (Cu@N-GQDs) as bifunctional nanozymes. The Cu@N-GQDs were synthesized via citric acid pyrolysis in the presence of ammonium hydroxide (serving as both nitrogen source and reductant) and copper chloride, leading to uniform incorporation of copper oxide species onto the N-GQD surface. The resulting nanohybrids exhibit two synergistic functionalities: intrinsic fluorescence comparable to pristine N-GQDs, and significantly enhanced peroxidase-like catalytic activity attributed to the anchored copper species. Upon interaction with sulfide ions, the system undergoes a dual-optical response: (i) fluorescence quenching via Cu-S complexation, and (ii) inhibition of peroxidase-like activity due to the deactivation of Cu catalytic centers via the interaction with S²⁻. This dual-signal strategy enables sensitive quantification of S²⁻, achieving detection limits of 0.5 µM (fluorescence) and 3.5 µM (colorimetry). The sensor demonstrates excellent selectivity over competing substances and high reliability and precision in real tap water samples. These findings highlight the potential of Cu@N-GQDs as robust, bifunctional, and field-deployable nanozyme probes for environmental and biomedical sulfide ion monitoring. Full article

pH is a critical parameter requiring precise monitoring across scientific, industrial, and biological domains. Fluorescent pH probes offer a powerful alternative to traditional methods (e.g., electrodes, indicators), overcoming limitations in miniaturization, long-term stability, and electromagnetic interference. By utilizing photophysical mechanisms—including intramolecular charge transfer (ICT), photoinduced electron transfer (PET), and fluorescence resonance energy transfer (FRET)—these probes enable high-sensitivity, reusable, and biocompatible sensing. This review systematically details recent advances, categorizing probes by operational pH range: strongly acidic (0–3), weakly acidic (3–7), strongly alkaline (>12), weakly alkaline (7–11), near-neutral (6–8), and wide-dynamic range. Innovations such as ratiometric detection, organelle-specific targeting (lysosomes, mitochondria), smartphone colorimetry, and dual-analyte response (e.g., pH + Al³⁺/CN⁻) are highlighted. Applications span real-time cellular imaging (HeLa cells, zebrafish, mice), food quality assessment, environmental monitoring, and industrial diagnostics (e.g., concrete pH). Persistent challenges include extreme-pH sensing (notably alkalinity), photobleaching, dye leakage, and environmental resilience. Future research should prioritize broadening functional pH ranges, enhancing probe stability, and developing wide-range sensing strategies to advance deployment in commercial and industrial online monitoring platforms. Full article