A wearable gloved sensor based on fluorescent Ag nanoparticles and europium complexes for visualized assessment of tetracycline in food samples

Machine learning-assisted ratiometric fluorescence sensor array for recognition of multiple quinolones antibiotics

Developing analytical methods for simultaneous detection of multiple antibiotic residues is crucial for environmental protection and human health. In this study, a dual lanthanide fluorescence probe (GDP-Eu-Tb) based on nucleotides has been designed. The addition of quinolone antibiotics (QNs) quench the Eu3+ fluorescence signal through the inner filter effect (IFE) and exhibit characteristic peaks, enabling ratio fluorescence detection of levofloxacin (LVLX), gatifloxacin (GTLX), and moxifloxacin (MXLX). A ratiometric fluorescence sensor array is constructed using a single sensor element (GDP-Eu-Tb), combined with principal component analysis (PCA) and decision tree (DT) algorithms to model the relationship between fluorescence intensity ratios (I450/I616, I460/I616, I463/I616, I468/I616) and QNs. The performance of the DT model is evaluated using accuracy, precision, recall, and F1 score, with stability and generalizability confirmed by stratified ten-fold cross-validation. This approach demonstrates high sensitivity, selectivity and applicability and provides an effective solution for antibiotic residue detection.

Advancements in silver-based nanocatalysts for organic transformations and other applications: a comprehensive review (2019-2024)

Over time, nanocomposites have revolutionized materials science, offering numerous applications in fields such as catalysis, environmental purification and treatment, biomedicine and various industries. Among these, silver-based nanocomposites are particularly notable for their remarkable stability, reusability, biocompatibility, and multifunctional medicinal properties. Hence, we present a comprehensive summary of recent developments (2019-2024) in silver-based nanomaterials, focusing on their applications across multiple domains, including catalytic organic transformations, biomedical uses, environmental remediation, and industrial sectors such as food packaging, agriculture and textiles. By highlighting recent advancements and emerging trends, we aim to provide a thorough understanding of the role of silver-based nanocomposites in contemporary science and technology, emphasizing their potential to drive innovation across diverse disciplines.

Iridium(III) complex functionalized ZIF-8 as a novel POD-like nanozyme for visual assay of triazine pesticides

Due to the unique advantages of mimicking natural enzymes, nanozymes have received ever-growing interest in a wide range of fields including analytical chemistry in the past two decades. Exploring novel kinds of nanozymes with efficient active sites has always been one of the most important and hot topics in nanozyme-related research so far, especially in portable monitors. Herein, zeolitic imidazolate framework-8 (ZIF-8) incorporated with an organometallic iridium(III) complex as a new active site denoted as Irppy-ZIF-8 obtained via a one-pot coordination reaction between the iridium solvent complex and 2-methylimidazole is reported as an efficient peroxidase (POD)-like nanozyme. Importantly, due to the specific inhibition effects of triazine pesticides on the POD-like activities of this novel nanozyme, a portable acetylcholinesterase (AChE)-free colorimetric sensor via a smartphone apart from a UV-vis spectrometer to detect triazine pesticides in real vegetable sample analysis is further successfully proposed in this work. It should be noted that this work could not only open up a new avenue to explore novel kinds of nanozymes from organometallic complexes as active sites, but also promote the progress in emerging applications of nanozymes in visual and portable sensors in the future.

A sensitized dual-response ratiometric fluorescent sensor integrated smartphone platform for accurate discrimination and detection of tetracycline homologues based on N-CDs‒Eu3+ complex

A sensitized dual-response ratiometric fluorescent sensor integrated smartphone platform for accurate discrimination and detection of tetracycline (TC) homologues was fabricated based on N-CDs-Eu3+ complex. In the sensing system, N-CDs act as a sensitizer of Eu3+ and significantly enhance the fluorescence of TC-Eu3+ complex approximate 40-fold owing to the synergistic effect of antenna effect (AE) and fluorescence resonance energy transfer (FRET). A paper sensor integrated with a smartphone platform is further fabricated for on-site measurement of TC. The proposed sensing platform exhibits an obvious color change from blue to red with limit of detection (LOD) of 1.5 and 63.2 nM for spectrofluorimetry and paper sensor, respectively. In addition, to eliminate the interference from TC homologues, a simple and effective sensor array was constructed by regulating the pH of the system. The different fluorescence responses to four tetracycline homologues used widely (TC, OTC, CTC, and DOX) were examined and dealt with principal component analysis, and accurate differentiation of TC homologues was therefore achieved. This work provides an integrated method for identification and synchronous quantitative detection of TCs, and a potential application for visual and on-site detection of TCs in environmental monitoring and food safety.

Deep learning assisted logic gates for real-time identification of natural tetracycline antibiotics

The overuse and misuse of tetracycline (TCs) antibiotics, including tetracycline (TTC), oxytetracycline (OTC), doxycycline (DC), and chlortetracycline (CTC), pose a serious threat to human health. However, current rapid sensing platforms for tetracyclines can only quantify the total amount of TCs mixture, lacking real-time identification of individual components. To address this challenge, we integrated a deep learning strategy with fluorescence and colorimetry-based multi-mode logic gates in our self-designed smartphone-integrated toolbox for the real-time identification of natural TCs. Our ratiometric fluorescent probe (CD-Au NCs@ZIF-8) encapsulated carbon dots and Au NCs in ZIF-8 to prevent false negative or positive results. Additionally, our independently developed WeChat app enabled linear quantification of the four natural TCs using the fluorescence channels. The colorimetric channels were also utilized as outputs of logic gates to achieve real-time identification of the four individual natural tetracyclines. We anticipate this strategy could provide a new perspective for effective control of antibiotics.

Sensitive and selective detection of tetracycline using fluorescence-enhanced Eu(III)-functionalized silver nanoparticles with homocysteine

Utilizing metal luminescence enhancement to design fluorescent probes is a very sensible strategy. Herein, a fluorescent probe based on europium (III)-functionalized silver nanoparticles-conjugated homocysteine (AgNPs-Hcy-Eu3+) was proposed for the selective and sensitive detection of tetracycline (TC). In this probe, Eu(III) was employed as the detection signal unit for TC, while AgNPs-Hcy was used as the ligand of fluorescence enhancement. When TC exists, it can bind to Eu3+ immobilized in AgNPs-Hcy, leading to an enhanced fluorescence signal from Eu3+ through energy transfer. Under optimal conditions, the fluorescence intensity of AgNPs-Hcy-Eu3+ increased linearly with increasing TC concentration in the range of 0.1-30 μM (R2 = 0.9964). The fluorescent probe own fluorescence enhancement, paving the way for sensitive detection with a low detection limit of 0.083 μM. It also has good selectivity for common antibiotics and anions. This work can be applied to the determination of TC in tap water and milk with recoveries of 94-98.5%. We expect AgNPs-Hcy-Eu3+ to have potential applications in environmental testing and food safety.

Recent progress in lanthanide-based fluorescent nanomaterials for tetracycline detection and removal

Tetracycline (TC) has been widely used in clinical medicine and animal growth promotion due to its broad-spectrum antibacterial properties and affordable prices. Unfortunately, the high toxicity and difficult degradation rate of TC molecules make them easy to accumulate in the environment, which breaks the ecological balance and seriously threatens human health. Rapid and accurate detection of TC residue levels is important for ensuring water quality and food safety. Recently, fluorescence detection technology of TC residues has developed rapidly. Lanthanide nanomaterials, based on the high luminescence properties of lanthanide ions and the high matching with TC energy levels, are favored in the real-time trace detection of TC due to their advantages of high sensitivity, rapidity, and high selectivity. Therefore, they are considered potential substitutes for traditional detection methods. This review summarizes the synthesis strategy, TC response mechanism, removal mechanism, and applications in intelligent sensing. Finally, the development of lanthanide nanomaterials for TC fluorescence detection and removal is reasonably summarized and prospected. This review provides a reference for the establishment of a method for the accurate determination of TC content in complex food matrices.

Kinetically Controlled Self-Assembly of Ag Nanoclusters with Enhanced Luminescence

Constructing self-assembly with definite assembly structure-property correlation is of great significance for expanding the property richness and functional diversity of metal nanoclusters (NCs). Herein, a well-designed liquid reaction strategy was developed through which a highly ordered nanofiber superstructure with enhanced green photoluminescence (PL) was obtained via self-assembly of the individual silver nanoclusters (Ag NCs). By visual monitoring of the kinetic reaction process using time-dependent and in situ spectroscopy measurements, the assembling structure growth and the structure-determined luminescence mechanisms were revealed. The as-prepared nanofibers featured a series of advantages involving a high emission efficiency, large Stokes shift, homogeneous chromophore, excellent photostability, high temperature, and pH sensibility. By virtue of these merits, they were successfully employed in various fields of luminescent inks, encryption and anticounterfeiting platforms, and optoelectronic light-emitting diode (LED) devices.

Deep eutectic solvent-assisted synthesis of La-Ce hybrid nanorods for the colorimetric determination of tetracycline in foods

Tetracycline (TC) as a broad-spectrum antibiotic, is widely used in the prevention and treatment of various bacterial diseases. However, its abuse in the livestock industry may lead to interference in human microecology, thereby causing various side effects. In this study, deep eutectic solvents (DESs) were synthesized using L-(-)-threonine (L-(-)-Thr) and cerium nitrate hexahydrate (Ce(NO3)3·6H2O), and later lanthanum nitrate hexahydrate (La(NO3)3·6H2O) was doped to synthesize La-Ce hybrid nanorods. These nanorods can be used for the determination of TC with high sensitivity and selectivity by the colorimetric method. This approach has a linear response to TC between 0.05 μM and 10 μM, with a detection limit of 0.016 μM. In this system, good dispersion provides the substance with a distinct peroxidase activity, which is used to create a colorimetric sensor for detecting TC. Mechanism studies show that the superoxide radical generated by the La-Ce nanomembrane plays a key role in peroxidase catalysis. Finally, the practicality of the method was verified by the determination of TC in food products (milk, pork and honey), which demonstrated that a good recovery rate can be obtained (91.4-102%).

Construction of a dual-excitation ratiometric fluorescent probe for determining peroxynitrite levels in living cells and zebrafish

Peroxynitrite (ONOO-) is a highly reactive oxygen species that plays a critical role in many physiological and pathological processes of cell function. This study aimed to propose a ratiometric fluorescent probe BDHCA derived from coumarin for determining the ONOO- level. ONOO- could specifically induce oxidative cleavage of the conjugated C = C double bond in probe BDHCA, providing a fluorescent ratiometric output. The response of probe BDHCA to ONOO- was selective, fast, and highly sensitive, with a detection limit of 50.3 nM. Biological imaging experiments suggested that probe BDHCA could be used to image ONOO- in living RAW264.7 cells and zebrafish.

Highly sensitive fluoroprobe for detecting Sudan dyes in paprika utilizing carbon dot-embedded zeolitic imidazolate framework-8

In this manuscript, we synthesized CDs@ZIF-8 through a one-step, in-situ method by integrating green-emitting carbon dots (CDs) with zeolitic imidazolate framework-8 (ZIF-8). The resulting CDs@ZIF-8 was utilized as an ultrasensitive probe for detection, leveraging the inner filter effect. The analysis demonstrated the capability to detect Sudan dyes. Sudan I, for example, could be detected within a concentration range spanning from 0.25 to 70 μM, achieving a remarkable detection limit of 76.56 nM. This established method was effectively employed for detecting Sudan I in paprika. Compared with CDs, CDs@ZIF-8 exhibited a 3.32-fold increase in sensitivity and a wider detection range. This enhanced performance was attributed to the porous ZIF-8, which allowed for the enrichment of targets around CDs and avoided the aggregation of CDs. Additionally, embedding the CDs in ZIF-8 improved their pH stability. Our study provides a new approach for using CDs under limited conditions by leveraging metal-organic frameworks.

Portable luminescent fiber- and glove-based nanosensor for multicolor visual detection of tetracycline in food samples

An intelligent fluorescent nanoprobe (lignite-CDs-Eu) was constructed by an effective and facile method based on lignite-derived carbon dots (CDs) and lanthanide europium ions (Eu3+), which exhibited high sensitivity, low detection limit (13.35 nM) and visual color variation (from blue to red) under ultraviolet light towards tetracycline (TC) detection. Significantly, portable and economical sensors were developed using lignite-CDs-Eu immobilized fiber material of filter paper and wearable glove with the aid of color extracting and image processing application (APP) in the smartphone. Facile, fast and real-time visual detection of TC in food samples was realized. Moreover, logic gate circuit was also designed to achieve intelligent and semi-quantitative inspection of TC. To some extent, this study extended the cross-application of intelligent computer software in food analytical science, and provided a certain reference for the development of small portable detection sensors which were suitable for convenience and non-professional use in daily life.

Carbon dots/Ruthenium(III) nanocomposites for FRET fluorescence detection and removal of mercury (II) via assembling into nanofibers

The determination and removal of mercury(II) (Hg2+) are essential for human health and environmental ecosystems. Herein, an ingenious carbon dots (CDs)-based Förster resonance energy transfer (FRET) system (N, S-CDs/Ru) was fabricated employing CDs and Ru3+ units as energy-transfer doner/acceptor pairs for visual detection and efficient removal of Hg2+. The treatment of Hg2+ induced a remarkable linear enhancement of the ratiometric fluorescence (F613 nm/F478 nm) with a detection limit (LOD) of 95 nM, along with continuous fluorescence color variations from blue to red. Given that the fluorescence color recognition and processing realized the real-time and rapid quantitation of Hg2+ by paper-based smartphone sensing platform. The mechanistic study revealed that the N/S/O-rich surface of the system enabled the Hg2+-triggered self-assembly from dots to nanofibers, combing with the active FRET process. Also, the efficient removal of Hg2+ with a removal efficiency of ∼98 % and an adsorption capacity of ∼372 mg/g was obtained. Furthermore, it was found that N, S-CDs/Ru loaded commercialized SiO2 or SBA-15 could facilitate the removal of Hg2+ with a removal efficiency over 99 % and an adsorption capacity up to ∼562 mg/g. This study provides a potential strategy for environmental monitoring and remediation.

Machine-learning assisted multicolor platform for multiplex detection of antibiotics in environmental water samples

Antibiotic (AB) resistance is one of daunting challenges of our time, attributed to overuse of ABs and usage of AB-contaminated food resources. Due to their detrimental impact on human health, development of visual detection methods for multiplex sensing of ABs is a top priority. In present study, a colorimetric sensor array consisting of two types of gold nanoparticles (AuNPs) were designed for identification and determination of ABs. Design principle of the probe was based on aggregation of AuNPs in the presence of ABs at different buffer conditions. The utilization of machine learning algorithms in this design enables classification and quantification of ABs in various samples. The response profile of the array was analyzed using linear discriminant analysis algorithm for classification of ABs. This colorimetric sensor array is capable of accurate distinguishing between individual ABs and their combinations. Partial least squares regression was also applied for quantitation purposes. The obtained analytical figures of merit demonstrated the potential applicability of the developed sensor array in multiplex detection of ABs. The response profiles of the array were linearly correlated to the concentrations of ABs in a wide range of concentration with limit of detections of 0.05, 0.03, 0.04, 0.01, 0.06, 0.05 and 0.04 μg.mL-1 for azithromycin, amoxicillin, ciprofloxacin, clindamycin, cefixime, doxycycline and metronidazole respectively. The practical applicability of this method was further investigated by analysis of mixture samples of ABs and determination of ABs in river and underground water with successful verification.

Fluorescence determination of the total amount of tetracyclines by a flavonol-based supramolecular sensor

Tetracyclines (TCs) are a group of broad-spectrum antibiotics against multiplying microorganisms yet with several adverse effects on humans. Since all types of TCs have the similar chemical skeleton and mechanism of action, quantification of total amount of TCs in the environment was of particular importance. To date, dozens of fluorescent probes have been reported for TCs detection, but only very few of them enabled detection of total TCs. In this study, we report a novel supramolecular sensor constructed by human serum albumin as the recognition moiety and a flavonol fluorophore as the indicator. Under the 370 nm UV excitation, this sensor exhibits the rapid response (5 s), acceptable sensitivity (limit of detection ∼ 0.58 μM), long dynamic detection range (0-20 μM), prominent specificity, and excellent anti-interference properties for analysis of total TCs. The mechanism was carefully validated using 1H NMR, fluorescence titration experiments, molecular docking, and mass spectrometry. We expect this work can inspire more sensor design for TCs quantification.

Fluorescence switch based on NIR-emitting carbon dots revealing high selectivity in the rapid response and bioimaging of oxytetracycline

The abuse of antibiotics has led to serious environmental pollution and the emergence of drug-resistant bacteria surpassing the replacement rate of antibiotics. Herein, near-infrared fluorescent carbon dots (NIR-CDs) were developed to meet the requirements for oxytetracycline (OTC) detection in food and water samples (milk, honey, and lake water) with a detection limit of 0.112 μM. These NIR-CDs, possessing excellent water-solubility, deep tissue penetration ability, and tunable optical properties, exhibit maximum emission at 790 nm (NIR-I window). Unlike traditional CDs, this novel NIR-CDs nanoprobe provides a dual response in the presence of OTC (quenching and bathochromic shifting), without obvious interference from other existing biomolecules and metal ions. Additionally, these NIR-CDs exhibit excellent photostability and multi-resistance under UV irradiation, exceptional pH stability (pH 6-12), reliable long-time exposure, and durability in ionic (NaCl) environments. Moreover, NIR-CDs and NIR-CDs@OTC are nontoxic and were successfully utilized for cell-imaging applications in normal (NIH3T3) and cancer cells (HeLa).

Magnetic Molecularly Imprinted Chitosan Combined with a Paper-Based Analytical Device for the Smartphone Discrimination of Tryptophan Enantiomers

The separation of enantiomers plays a critical role in pharmaceutical development, ensuring therapeutic efficacy, safety, and patent protection. It enables the production of enantiopure drugs and enhances our understanding of the properties of chiral compounds. In this study, a straightforward and effective chiral detection strategy was developed for distinguishing between tryptophan (TRP) enantiomers. The approach involved the preparation of a magnetic molecularly imprinted chitosan (MMIC) for preparation of the sample, which was combined with a nitrocellulose membrane (a paper-based analytical device, PAD) integrated with D-TRP covalently grafted with polymethacrylic acid (PAD-PMA_D-TRP). Discriminating between the TRP enantiomers was achieved using AuNPs as a colorimetric probe. Indeed, the presence of D-TRP rapidly induced the aggregation of AuNPs due to its strong affinity to PAD-PMA_D-TRP, resulting in a noticeable change in the color of the AuNPs from red to purple. On the other hand, L-TRP did not induce any color changes. The chiral analysis could be easily performed with the naked eye and/or a smartphone. The developed method exhibited a detection limit of 3.3 µM, and it was successfully applied to detect TRP in serum samples, demonstrating good recovery rates. The proposed procedure is characterized by its simplicity, cost-effectiveness, rapidity, and ease of operation.