Search Results (188)

Hypochlorous acid (HClO) serves as a biological mediator and is widely utilized as a disinfectant in food processing and water treatment. However, excessive HClO residues in food and environmental water raise concerns due to the potential formation of carcinogenic chlorinated byproducts and disinfection byproducts (DBPs). Despite its importance, traditional methods for HClO detection often involve complex sample preparation, sophisticated instrumentation, and skilled operators. Herein, we report an aggregation-induced emission (AIE) small molecule fluorescent probe (NYV) that integrates colorimetric and ratiometric fluorescence responses for the detection of HClO. This probe exhibits high sensitivity, with a detection limit of 0.35 $\mathsf{\mu }$M, a rapid response time of 1 min, and a wide linear range (0–142.5 $\mathsf{\mu }$M), along with anti-interference capabilities, making it suitable for real-time monitoring. Furthermore, we have developed a portable solid-state sensor based on probe NYV for the rapid visual detection of HClO. The potential applications of this probe in real sample analysis and bioimaging experiments are demonstrated. Our findings contribute to the development of innovative fluorescent probes for HClO detection, with broad applications in food safety, environmental monitoring, and biomedical research on oxidative stress and ferroptosis. Full article

Ketones, which are key biomarkers of fat oxidation, are relevant for metabolic health maintenance and disease development, making continuous monitoring essential. In this study, we introduce a novel colorimetric sensor designed for potential continuous acetone detection in biological fluids. The sensor features a polydimethylsiloxane (PDMS) shell that encapsulates a sensitive and specific liquid-core acetone-sensing probe. The microsphere sensors were characterized by evaluating their size, PDMS shell thickness, colorimetric response, and sensitivity under realistic conditions, including 100% relative humidity (RH) and CO₂ interference. The microsphere size and sensor sensitivity can be controlled by modifying the fabrication parameters. Critically, the sensor showed high selectivity for acetone detection, with negligible interference from CO₂ concentrations up to 4%. In addition, the sensor displayed good reproducibility (CV < 5%) and stability under realistic storage conditions (over two weeks at 4 °C). Finally, the accuracy of the microsphere sensor was validated against a gold standard gas chromatography-mass spectrometry (GC-MS) method using simulated and real breath samples from healthy individuals and type 1 diabetes patients. The correlation between the microsphere sensor and GC-MS produced a linear fit with a slope of 0.948 and an adjusted R-squared value of 0.954. Therefore, the liquid-core microsphere-based sensor is a promising platform for acetone body fluid analysis. Full article

The interpretation of intradermal test results may improve if wheal erythema is measured objectively using colorimetry. Our aim was to find the necessary number of erythema colorimetric measurements, taken before and after intradermal injections of histamine 0.01% (H1), histamine 0.001% (H2), histamine 0.0001% (H3) and a negative control (NC). We also aimed to assess whether erythema should be measured at the wheal center or border, and to investigate whether erythema appears beyond histamine wheals (flare), as observed in humans. Duplicate injections of the four solutions were administered on the lateral thorax of seven healthy dogs and erythema was measured by removing and repositioning the colorimeter probe. Colorimetry can differentiate the change in erythema (ΔE) at the center (ΔEc), but not at the border, of the H1 wheals from the ΔE of NC and H3 wheals. Reliable ways to calculate ΔEc were to use the first positive a* axis value of the colorimeter before and after the injection or to obtain the first seven positive a* axis values, excluding the highest and lowest, and calculated the mean of the remaining five. Unlike in humans, intradermal injection of histamine, even at a concentration of 0.01%, did not induce a flare reaction in healthy dogs. Full article

Aptamers refer to a class of oligonucleotide probes that have demonstrated remarkable capabilities beyond mere genetic coding, including the unique ability to recognize and selectively bind to specific molecular targets. Numerous advantages, including accessibility for targeting a diverse array of molecules and compatibility with different signal amplification and transduction elements, underscore the application of aptamers for delivering rapid and accurate diagnostic tests at the point of care. This review provides a comprehensive summary of the recent advances in aptamer-based point-of-care testing, especially highlighting the innovative applications of aptamers in colorimetric sensors, lateral flow assays, fluorescent biosensors, and electrochemical biosensors. Additionally, current challenges in this burgeoning field and forward-looking perspectives for aptamer-based point-of-care testing are discussed. Full article

Certain plant raw materials are rich in antioxidant and antimicrobial compounds, which are highly valued in modern medicine. These include the leaves of various species and cultivars of pears. For our research, we chose the leaves of the common pear (Pyrus communis) and Asian pear (Pyrus pyrifolia). Four different extracts were obtained from all raw materials and were investigated for their antimicrobial and antioxidant activity. The content of total phenolics and flavonoids was measured using colorimetric methods, and antiradical activity was measured using DPPH and ABTS radical probes. The antimicrobial activity of extracts was measured using the disc diffusion method, and the amount of major antimicrobial components (hydroquinone and arbutin) was measured using the HPLC method. The highest amount of general phenols and flavonoids was found in ethyl acetate extracts in all cultivars, and the lowest amount of phenols was found in the remaining aqueous solution. The amount of general phenols positively correlated with the antiradical activity of extracts. The strongest antimicrobial activity against Gram-positive and Gram-negative pathogens corresponded to the highest content of hydroquinone and arbutin in ethyl acetate extracts. Extracts obtained from pear leaves showed an average content of phenolic compounds and average antiradical activity compared to extracts from other raw materials, especially green tea or bergenia leaves. The amount of hydroquinone was moderate, lower than that of arbutin. The antimicrobial activity of the extracts was moderate due to the average amount of hydroquinone, which is the main antimicrobial compound. Full article

The control of elemental impurities is a critical step in the preparation of lanthanum carbonate, with platinum being one such impurity. Residual platinum is typically non-therapeutic and must be strictly controlled to ensure both safety and product quality. This paper describes a colorimetric method for determining platinum (IV) in solutions based on the anti-aggregation of gold nanoparticles modified with 4-methylsulfonylaniline (4-MESA). The presence of Britton–Robinson buffer induces the aggregation of the 4-MESA-AuNPs nanoparticle probe. However, when platinum (IV) is introduced, it disrupts the aggregation of the 4-MESA-AuNPs, causing a color change in the solution. The absorbance at 524 nm showed a strong linear correlation in the concentration range of 1.00 × 10⁻² μM to 5.00 × 10² μM. Under optimal conditions, LOD and LOQ values of 10.00 × 10⁻³ μM and 3.03 × 10⁻² μM, respectively, were observed. This method has been successfully applied to the determination of platinum (IV) in lanthanum carbonate API. Full article

Due to its unique molecular fingerprinting capability and multiplex detection advantages, surface-enhanced Raman scattering (SERS) has shown great application potential in the field of biological analysis. However, the weak signal intensity and large background interference significantly limited the application of SERS in biosensing and bioimaging. Loading a large amount of Raman molecules with signal in the silent region on the hotspots of the electromagnetic field of the SERS substrate can effectively avoid severe background noise signals and significantly improve the signal intensity, making the sensitivity and specificity of SERS detection remarkably improved. To achieve this goal, a new SERS signal-amplification strategy is herein reported for background-free detection of Cu²⁺ by using Raman-silent probes loaded on cabbage-like gold microparticles (AuMPs) with high enhancement capabilities and single-particle detection feasibility. In this work, carboxyl-modified AuMPs were used to enable Cu²⁺ adsorption via electrostatic interactions, followed by ferricyanide coordination with Cu²⁺ to introduce cyano groups, therefore generating a stable SERS signal with nearly zero background signals owing to the Raman-silent fingerprint of cyano at 2137 cm⁻¹. Based on the signal intensity of cyano groups correlated with Cu²⁺ concentration resulting from the specific coordination between Cu²⁺ and cyanide, a novel SERS method for Cu²⁺ detection with high sensitivity and selectivity is proposed. It is noted that benefiting from per ferricyanide possessing six cyano groups, the established method with the advantage of signal amplification can significantly enhance the sensing sensitivity beyond conventional approaches. Experimental results demonstrated this SERS sensor possesses significant merits towards the determination of Cu²⁺ in terms of high selectivity, broad linear range from 1 nM to 1 mM, and low limit of detection (0.1 nM) superior to other reported colorimetric, fluorescence, and electrochemical methods. Moreover, algorithm data processing for optimization of SERS original data was further used to improve the SERS signal reliability. As the proof-of-concept demonstrations, this work paves the way for improving SERS sensing capability through the silent-range fingerprint and signal amplification strategy, and reveals SERS as an effective tool for trace detection in complex biological and environmental matrices. Full article

Heavy and transition metal (HTM) ions have significant harmful effects on the physical environment and play crucial roles in biological systems; hence, it is crucial to accurately identify and quantify any trace pollution. Molecular sensors which are based on organic molecules employed as optical probes play a crucial role in sensing and detecting toxic metal ions in water, food, air, and biological environments. When appropriate combinations of conduction and selective recognition are combined, fluorescent and colorimetric chemosensors are appealing instruments that enable the selective, sensitive, affordable, portable, and real-time investigation of the possible presence of heavy and transition metal ions. This feature article aims to provide readers with a more thorough understanding of the different methods of synthesis and how they work. As noted in the literature, we will highlight colorimetric and fluorometric sensors based on their receptors into multiple categories for heavy metal ion detection, such as Hg²⁺, Ag²⁺, Cd^2+, Pb²⁺, and In³⁺, and simultaneous multiple-ion detection. Full article

Background/Objectives: Some G-quadruplex (G4)-forming nucleic acid sequences bind a hemin cofactor to enhance its peroxidase-like activity. This has been implemented in a variety of bioanalytical assays benefiting from analyte-dependent peroxidation of a chromogenic organic substrate (e.g., ABTS) to produce a color change. Adenine and cytosine nucleotides in the vicinity of the G4 hemin-binding site promote the peroxidation reaction. In this work, the effect of G4 loop and flanking nucleotides on the colorimetric signal of split hybridization probes utilizing hemin-G4 signal reporters was tested. Methods: G4s varying by loop sequences and flanking nucleotides were tested with hemin for ABTS peroxidation (A₄₂₀), and the signal was compared with that produced by the most catalytically efficient complexes reported in the literature using one-way ANOVA and post hoc pairwise comparison with Tukey’s HSD test. The best G4s were used as signal transducers in the split peroxidase deoxyribozyme (sPDz) probes for sensing two model nucleic acid analytes, as well as in a cascade system, where the analyte-dependent assembly of an RNA-cleaving deoxyribozyme 10–23 results in G4 release. Results: Intramolecular G4s (G₃T)₃G₃TC or G₃T₃G₃ATTG₃T₃G₃ were found to be the most efficient hemin PDzs. When splitting intramolecular G4 for the purpose of sPDz probe design, the addition of a flanking d(TC) sequence at one of the G4 halves or d(ATT) in a loop connecting the second and third G-tracts helps boost analyte-dependent signal intensity. However, for the cascade system, the effect of d(TC) or d(ATT) in the released G4 was not fully consistent with the data reported for intramolecular G4-hemin complexes. Conclusions: Our findings offer guidance on the design of split hybridization probes utilizing the peroxidase-like activity of G4-hemin complexes as a signal transducer. Full article

Aptamers have recently become novel probes for biosensors because of their good biocompatibility, strong specificity, and high sensitivity. Biosensors based on peptides or nucleic acid aptamers are used in implantable and wearable devices owing to their ease of synthesis and economic efficiency. Simultaneously, amphoteric ionic peptides are being explored as antifouling layers for biosensors resistant to interference from extraneous proteins in serum. Thus, this paper reviews recently developed aptamer-based biosensors and introduces peptide- and nucleic acid-based biosensors, while focusing on the three primary classes of biosensors: electrochemical sensors, fluorescent or colorimetric biosensors, and electroluminescent sensors. Furthermore, we summarize their general construction strategies, describe specific electrochemical sensors that use peptides as an antipollution layer, and elucidate their advantages. Full article

The precise and fast detection of heparin, the most widely used anticoagulant, remains a significant challenge for assessing its use in a clinical setting. In this work, we adapt a well-established asymmetric cyanine fluorogenic platform for the purpose of ultrasensitive heparin detection in the presence of common interferant chemical species. Three analogous fluorescence probes are synthesized in order to optimize for the number of binding moieties. Their interaction with heparin is studied using steady-state absorption, fluorescence, and circular dichroism spectroscopy. The obtained probes exhibit a highly sensitive “turn-on” fluorescence response to heparin, with a LOD in the 10–25 nM range, well within practical requirement, as well as a visible colorimetric change. The heparin–probe complex is also employed as a sensitive detection platform for protamine, both in the “turn-off” fluorescence and ratiometric detection schemes. Full article

Annually, the Philippines is burdened by a high number of infections and deaths due to Dengue. This disease is caused by the Dengue virus (DENV) and is transmitted from one human host to another by the female Aedes aegypti mosquito. Being a developing country, most of the high-risk areas in the Philippines are resource-limited and cannot afford equipment for detection and monitoring. Moreover, traditional clinical diagnoses of DENV infection are costly and time-consuming and require expertise. Hence, it is important to establish effective vector control and surveillance measures. In this study, we developed a DNA-based nanobiosensor for the colorimetric detection of Dengue virus serotype 2 (DENV-2) synthetic target DNA (stDNA S2) using gold nanoparticles (AuNPs). We successfully functionalized dextrin-capped gold nanoparticles with the designed DENV-2 oligonucleotide probes. The detection of the complementary stDNA S2, indicated by the pink-colored solution, was successfully performed within 15 min using 0.40 M NaCl solution. We were able to detect up to 36.14 ng/μL of stDNA S2 with some cross-reactivity observed with one non-complementary target. We believe that our study offers a basis for developing nanobiosensors for other DENV serotypes. Full article

Human monkeypox (Mpox) is a zoonotic disease caused by the Monkeypox virus (MPXV). As of 14 August 2024, the World Health Organization (WHO) has declared it a global health emergency. For Mpox, this was the second public health emergency of global significance in the past two years. MPXV belongs to the Poxviridae family and is phylogenetically and epidemically divided into two clades: the Congo Basin (Clade-I) and the West African (Clade-II) clades. Clade-I has been associated with more severe disease progression and higher mortality compared to Clade-II, and thus the differentiation between clades can play an important role in predicting disease prognosis. The LAMP technique has the advantages of not requiring thermal cycling and achieving higher amplification in a shorter time compared to qPCR. Different types of LAMP assays were developed in this study to benefit from these advantages. We report the development of LAMP-1 and LAMP-2 assays using the LAMP method to detect MPXV Clade-I and Clade-II, respectively. The LAMP-1 assay includes both fluorescence and visible colorimetric readout tests developed with sensitivities of 10³ and 10⁷ copies, respectively. For the LAMP-2 assay, a probe-based test utilizing the Novel R-Duplex DARQ probe was developed, offering fluorescence detection at a sensitivity of 10³ copies. As a result, we successfully developed three highly specific molecular diagnostic tests that distinctly differentiate between MPXV clades, delivering essential tools for the precise diagnosis and effective control of Mpox. Full article

Compared to natural enzymes, the development of efficient artificial simulated enzymes, such as those based on bimetallic materials with high catalytic activity and good stability, is an important way until now. Herein, we employed ZnCo₂O₄ microspheres as carriers to synthesize Pt-doped composites with different amounts using a one-pot method. The morphology and structure of the synthesized materials were characterized using XRD, SEM, BET, FT-IR, XPS, and Zeta potential techniques. It was found that Pt⁰ adhered well to the surface of ZnCo₂O₄ microspheres, with a 12.5% Pt doped ratio exhibiting abundant oxygen vacancies, excellent substrate affinity, and high peroxidase-like activity. Using fluorescent probes and electrochemical methods, the peroxidase-like catalytic mechanism has been explored that Pt@ZnCo₂O₄ microspheres can accelerate the electron transfer between H₂O₂ and 3,3′,5,5′-tetramethylbenzidine (TMB). Based on the optimal loading ratio of 12.5% of Pt@ZnCo₂O₄, a colorimetric sensor for visual detection of L-cysteine (L-Cys) was constructed, exhibiting a wide linear range of 0.1~50 µM and a low detection limit of 0.0163 µM. The sensor possesses good selectivity, reusability, and usage stability, which can be well applied to the determination of L-Cys in health product capsules with recovery rates of 96.9%~103.7% and RSD of 1.07%~6.50%. This work broadens the application prospects of spinel materials such as ZnCo₂O₄ in the field of biological analysis and also provides inspiration for the development of new artificial simulated enzymes. Full article

A novel rhodamine-6G derivative RdN was synthesized by condensing rhodamine glyoxal and 3-hydroxy-2-naphthoic hydrazide using a microwave irradiation-assisted reaction. Colorimetric and photophysical studies have demonstrated that the molecule produced can selectively sense Pb²⁺ and Cu²⁺ ions in a solution of CH₃CN/H₂O (9:1, v/v). The spirolactam ring of RdN opens upon complexation with the cations, forming a highly fluorescent complex and a visible color change in the solution. The compound RdN was further studied with the help of computational methods such as the Density Functional Theory (DFT) method and time-dependent density theory (TD-DFT) calculations to study the binding interactions and properties of the molecule. DFT calculations and job plot data supported the 2:1 complex formation between RdN and Pb²⁺/Cu²⁺. The limit of detection for Pb²⁺ was determined to be 0.112 µM and 0.130 µM for Cu²⁺. The probe RdN was applied to the image of Pb²⁺ and Cu²⁺ ions in living cells and is safe for biomedical applications. It is used to monitor Pb²⁺ in environmental water samples. Full article