Agarose Hydrogel Research Articles

Injectable Therapeutic Hydrogel with H2O2 Self-Supplying and GSH Consumption for Synergistic Chemodynamic/Low-Temperature Photothermal Inhibition of Postoperative Tumor Recurrence and Wound Infection.

Postoperative tumor recurrence and wound infection remain significant clinical challenges in surgery, often requiring adjuvant therapies. The combination treatment of photothermal therapy (PTT) and chemodynamic therapy (CDT) has proven to be effective in cancer treatment and wound infection. However, the hyperthermia during PTT increases the risk of normal tissue damage, severely impeding its application. Moreover, the efficacy of CDT is limited by insufficient hydrogen peroxide (H2O2) and excessive glutathione (GSH) levels at tumor or infection sites. Herein, an injectable and multifunctional CuO2@Au hydrogel system (CuO2@Au Gel) is developed for synergistic CDT and low-temperature PTT (LTPTT) to prevent tumor recurrence and bacterial wound infections. CuO2@Au Gel is constructed by embedding therapeutic CuO2@Au into low-melting point agarose hydrogel. In vitro and in vivo experiments confirm that the CuO2@Au in CuO2@Au Gel is capable of self-supplying H2O2 and depleting GSH, exhibiting effective CDT effect in acidic tumor or bacterial infected microenvironment. Additionally, it exhibits favorable photothermal conversion ability, inducing localized temperature elevation and synergistically enhancing CDT efficiency. The prepared CuO2@Au Gel demonstrates efficient tumor ablation capability in post-surgery recurrence mouse models and exhibits promising anti-infective efficiency in bacterial infection wound models, indicating significant potential in adjuvant therapy for post-surgical treatment and recovery.

Functional Agarose Hydrogels Obtained by Employing Homogeneous Synthesis Strategies

Functional Agarose Hydrogels Obtained by Employing Homogeneous Synthesis Strategies

An AIE and ESIPT based ratiometric fluorescent hydrogel sensor for detecting biogenic amines and chicken breast freshness

Meat quality is closely linked to food safety and human health, with freshness being a key indicator. Therefore, it is crucial to explore reliable and effective methods for detecting meat freshness. This study presented a ratiometric fluorescent hydrogel sensor based on aggregation-induced emission (AIE) and excited state intramolecular proton transfer (ESIPT) for this purpose. Tetraphenylene (TPE) and 2-(2′-hydroxyphenyl)-benzothiazole (HBT) fluorophore were intersected to generate TPE-HBT, and then a novel biogenic amines (BAs) detection ratiometric fluorescent probe, TPE-HBTAc, was successfully prepared by hydroxyl acetylation. TPE-HBTAc displayed a large Stokes shift and good photostability. It showed a significant response to the representative biogenic amine trimethylamine (TMA), with a ratiometric fluorescence change and low detection limit (LOD = 65 nM). Furthermore, BAs detection hydrogel sensor was created by mixing the fluorescent probe TPE-HBTAc in an agarose hydrogel with a 3D polymer network. The hydrogel sensor displayed a distinct color change from blue to yellow when exposed to TMA vapor under UV light and had a low detection limit (LOD = 5.88 ppm). The hydrogel sensor was utilized in conjunction with a smartphone RGB analysis system to determine the freshness of chicken breast samples. Consumers can easily observe the chicken breast freshness in real-time and non-destructively through UV flashlight illumination. The results of this work suggest that ratiometric fluorescent hydrogel sensor based on AIE and ESIPT can serve as a promising strategy to monitor food freshness.

Enhanced Enzyme Immobilization Using a Novel Agarose‐binding Tag Leads to Improved Flow Reactor Performance

Continuous enzymatic synthesis has gained increasing prominence, extending its applicability to the chemical industry. A practical approach for integrating enzymes into continuously operated reactors is their entrapment within polymer‐based hydrogels. In this study, we present a novel approach to enhance enzyme retention within agarose hydrogels, employing a carbohydrate‐binding module sourced from the Microbulbifer thermotolerans thermostable β‑agarase I (MtCBM) as a versatile agarose‐binding tag. Among the four tested carbohydrate‐binding modules, MtCBM exhibited superior binding affinity to solid agarose and fusion proteins incorporating MtCBM demonstrated significantly enhanced retention within agarose hydrogels. Employing a newly developed fluidic flat‐bed agarose reactor, we demonstrate that, due to increased retention in agarose hydrogels, a phenacrylate decarboxylase tagged with MtCBM yielded nearly six times more product compared to a similarly sized fusion enzyme lacking the MtCBM‐tag. The higher leaching rate of the unlabeled enzyme could not be compensated even by tripling the hydrogel layer thickness, clearly documenting the effectiveness of MtCBM labeling for retention in the gel matrix. In addition, we performed theoretical modelling of the reactor, which led to a deeper understanding of the retention kinetics. The results suggest that this innovative approach is promising for improving stability and reusability of enzymes in agarose‐based carriers.

Portable hydrogel kit based on Michael addition reaction for (E)-2-hexenal gas detection

Plants exhibit rapid responses to biotic and abiotic stresses by releasing a range of volatile organic compounds (VOCs). Monitoring changes in these VOCs holds the potential for the early detection of plant diseases. This study proposes a method for identifying late blight in potatoes based on the detection of (E)-2-hexenal, one of the major VOC markers released during plant infection by Phytophthora infestans. By combining the Michael addition reaction with cysteine-mediated etching of aggregation-induced emission gold nanoclusters (Au NCs), we have developed a portable hydrogel kit for on-site detection of (E)-2-hexenal. The Michael addition reaction between (E)-2-hexenal and cysteine effectively alleviates the etching of cysteine-mediated Au NCs, leading to a distinct fluorescence color change in the Au NCs, enabling a detection limit of 0.61 ppm. Utilizing the superior loading and diffusion characteristics of the three-dimensional structure of agarose hydrogel, our sensor demonstrated exceptional performance in terms of sensitivity, selectivity, reaction time, and ease of use. Moreover, quantitative measurement of (E)-2-hexenal was made easier by using ImageJ software to transform fluorescent images from the hydrogel kit into digital data. Such method was effectively used for the early detection of potato late blight. This study presents a low-cost, portable fluorescent analytical tool, offering a new avenue for on-site detection of plant diseases.

Electrophoretic Microplate Protein Identification Based on Gold Staining of Molybdenum Disulfide Hydrogels.

Numerous high-performance nanotechnologies have been developed, but their practical applications are largely restricted by the nanomaterials' low stabilities and high operation complexity in aqueous substrates. Herein, we develop a simple and high-reliability hydrogel-based nanotechnology based on the in situ formation of Au nanoparticles in molybdenum disulfide (MoS2)-doped agarose (MoS2/AG) hydrogels for electrophoresis-integrated microplate protein recognition. After the incubation of MoS2/AG hydrogels in HAuCl4 solutions, MoS2 nanosheets spontaneously reduce Au ions, and the hydrogels are remarkably stained with the color of as-synthetic plasmonic Au hybrid nanomaterials (Au staining). Proteins can precisely mediate the morphologies and optical properties of Au/MoS2 heterostructures in the hydrogels. Consequently, Au staining-based protein recognition is exhibited, and hydrogels ensure the comparable stabilities and sensitivities of protein analysis. In comparison to the fluorescence imaging and dye staining, enhanced sensitivity and recognition performances of proteins are implemented by Au staining. In Au staining, exfoliated MoS2 semiconductors directly guide the oriented growth of plasmonic Au nanostructures in the presence of formaldehyde, showing environment-friendly features. The Au-stained hydrogels merge the synthesis and recognition applications of plasmonic Au nanomaterials. Significantly, the one-step incubation of the electrophoretic hydrogels leads to high simplicity of operation, largely challenging those multiple-step Ag staining routes which were performed with high complexity and formaldehyde toxicity. Due to its toxic-free, simple, and sensitive merits, the Au staining integrated with electrophoresis-based separation and microplate-based high-throughput measurements exhibits highly promising and improved practicality of those developing nanotechnologies and largely facilitates in-depth understanding of biological information.

Terahertz time-domain transmission spectroscopy of water and hydrogel thin films: Extraction of optical parameters and application to agarose gel characterization

Terahertz time-domain spectroscopy (THz-TDS) is an emerging optical technique that has potential applications in the characterization of (bio)materials. However, the complicated extraction of optical parameters from multi-layered and optically thin samples is a barrier towards its acceptance by applied scientists. Therefore, the aim of this work is to provide a straightforward approach for the extraction of the THz absorption coefficient and index of refraction profiles of aqueous thin films in a window-sample-window configuration, which is ubiquitous in many laboratories (i.e., sample in a cuvette). A numerical approach-based methodology that accounts for multiple layers, Fabry–Pérot effect, and sample thickness is elaborated which involves an optical interference model based on a tri-layer structure and a simple thickness estimation technique. This method was validated on water samples where a good agreement was found with the THz optical parameters of water reported in the literature, while the use of a commercial software resulted in erroneous optical parameters estimates when used without due regard to its limitations. A case study was then performed to demonstrate the ability of the proposed method to characterize agarose hydrogels with varying degree of sulfation. It was demonstrated that THz-TDS can provide insight into the hydration state of the agarose hydrogels, including the relative number of the hydrogen bonds between the hydroxyl moieties of water and the polysaccharide network which is perturbed by the presence of sulfate. The trend in the index of refraction profiles suggested microstructural differences between the agarose hydrogels, which were confirmed by visualizing the agarose network morphology using cryo-SEM imaging.

Hydrogel-based radio frequency H2S sensor for in situ periodontitis monitoring and antibacterial treatment

Periodontitis, a chronic disease, can result in irreversible tooth loss and diminished quality of life, highlighting the significance of timely periodontitis monitoring and treatment. Meanwhile, hydrogen sulfide (H2S) in saliva, produced by pathogenic bacteria of periodontitis, is an important marker for periodontitis monitoring. However, the easy volatility and chemical instability of the molecule pose challenges to oral H2S sensing. Here, we report a wearable hydrogel-based radio frequency (RF) sensor capable of in situ H2S detection and antibacterial treatment. The RF sensor comprises an agarose hydrogel containing conjugated silver nanoparticles-chlorhexidine (AG-AgNPs-CHL hydrogel) integrated with split-ring resonators. Adhered to a tooth, the hydrogel-based RF sensor enables wireless transmission of sensing signals to a mobile terminal and a concurrent release of the broad-spectrum antibacterial agent chlorhexidine without complex circuits. With the selective binding of the AgNPs to the sulfidion, the RF sensor demonstrates good sensitivity, a wide detection range (2–30 μM), and a low limit of detection (1.2 μM). Compared with standard H2S measurement, the wireless H2S sensor can distinguish periodontitis patients from healthy individuals in saliva sample tests. The hydrogel-based wearable sensor will benefit patients with periodontitis by detecting disease-related biomarkers for practical oral health management.

Investigation of occurrence of aromatic amines in municipal wastewaters using passive sampling

Aromatic amines (AAs) are human-made compounds known for their mutagenic properties, entering surface waters from various sources, often originating as transformation products of dyes or pesticides. Despite their low concentrations in surface waters, AAs can exhibit mutagenicity. Our study focused on evaluating three passive samplers (PSs) for enriching these compounds from influent and effluent of a wastewater treatment plant (WWTP) in Brno, Czech Republic. The PSs tested included variants containing AttractSPE™ SDB-RPS sorbent disk, one with and one without a diffusive agarose hydrogel layer, and a modified Speedisk (Bakerbond Speedisk® H2O-Philic). PSs were deployed in wastewater (WW) for one to four weeks in various overlapping combinations, and the uptake of AAs to PSs was compared to their concentrations in 24-hour composite water samples. A targeted LC/MS analysis covered 42 amines, detecting 11 and 13 AAs in daily composite influent and effluent samples, respectively. In the influent, AAs ranged from 1.5 ng L−1 for 1-anilinonaphthalene to 1.0 μg L−1 for aniline, and the highest concentration among all measured amines was observed for cyclohexylamine at 2.9 μg L−1. In the effluent, concentrations ranged from 0.5 ng L−1 for 1-anilinonaphthalene to 88 ng L−1 for o-anisidine. PSs demonstrated comparable accumulation of amines, with integrative uptake up to 28 days in both influent and effluent and detection of up to 23 and 27 amines in influent and effluent, respectively; altogether 34 compounds were detected in the study. Sampling rates (Rs) were estimated for compounds present in at least 50 % of the samples and showing <40 % aqueous concentration variability, with robustness evaluated by comparing values for compounds in WWTP influent and effluent. Although all devices performed similarly, hydrogel-based PS exhibited superior performance in several criteria, including time integration and robustness of sampling rates, making it a suitable monitoring tool for AAs in WW.

A smartphone-assisted sensing hydrogels based on UCNPs@SiO2-phenol red nanoprobes for detecting the pH of aquatic products

For some aquatic products, pH has been considered a useful index to reflect the changes in materials during the loss of freshness. Based on the inner filter effect (IFE) between deprotonated phenol red (PR) and upconversion nanoparticles (UCNPs), UCNPs coated with PR-doped SiO2 shell were embedded in agarose hydrogel to develop a smartphone-assisted method for pH sensing. With the enhancement of pH response using a phase transfer agent (i.e., tetra butyl ammonium hydroxide, TBAH), the proposed senor realized the colorimetric and fluorescence detection of pH in the range of pH 6.6–8 and pH 6–8, respectively. The sensor also showed satisfied reversibility when switched between pH 6 and 8 for at least 5 cycles. Moreover, this sensor displayed great sensitivity, stability, and portability in analyzing actual fish, shrimp, and shellfish samples, providing a new sight for evaluating the freshness of aquatic products.

Ultrasound enhanced diffusion in hydrogels: An experimental and non-equilibrium molecular dynamics study.

Focused ultrasound has experimentally been found to enhance the diffusion of nanoparticles; our aim with this work is to study this effect closer using both experiments and non-equilibrium molecular dynamics. Measurements from single particle tracking of 40nm polystyrene nanoparticles in an agarose hydrogel with and without focused ultrasound are presented and compared with a previous experimental study using 100nm polystyrene nanoparticles. In both cases, we observed an increase in the mean square displacement during focused ultrasound treatment. We developed a coarse-grained non-equilibrium molecular dynamics model with an implicit solvent to investigate the increase in the mean square displacement and its frequency and amplitude dependencies. This model consists of polymer fibers and two sizes of nanoparticles, and the effect of the focused ultrasound was modeled as an external oscillating force field. A comparison between the simulation and experimental results shows similar mean square displacement trends, suggesting that the particle velocity is a significant contributor to the observed ultrasound-enhanced mean square displacement. The resulting diffusion coefficients from the model are compared to the diffusion equation for a two-time continuous time random walk. The model is found to have the same frequency dependency. At lower particle velocity amplitude values, the model has a quadratic relation with the particle velocity amplitude as described by the two-time continuous time random walk derived diffusion equation, but at higher amplitudes, the model deviates, and its diffusion coefficient reaches the non-hindered diffusion coefficient. This observation suggests that at higher ultrasound intensities in hydrogels, the non-hindered diffusion coefficient can be used.

Powerful Protein Nanoreservoirs Based on Stellate Mesoporous Silica Embedded in Composite Hydrogels: From Burst Release to Retention

AbstractIn the biomaterials field, one major issue with hydrogels (HGs) loaded with active therapeutics is the spontaneous leaking of the cargo occurring rapidly, usually over several hours. However, biological processes involved in regenerative medicine would require to have a sustained drug delivery lasting over weeks/months or be triggered only when a specific biochemical stimulus (enzymatic, cellular, or antimicrobial) is applied. In this work, this challenge is addressed by demonstrating that the spontaneous protein release from an agarose HG (used as model HG) can be partially or totally blocked by the incorporation of stellate mesoporous silica (STMS) nanoparticles (NPs, ≈150 ± 28 nm size, 15 nm pore) within the HG. It is shown here that the porous silica NPs act as sub‐micrometer size reservoirs ensuring precise level retention simply by playing on the amount of STMS embedded in the HG. Further, this effect is shown for various proteins demonstrating the versatility of this concept.

In Situ Imaging of Subcutaneous Drug Delivery Systems Using Microspatially Offset Low-Frequency Raman Spectroscopy.

The noninvasive in situ monitoring of the status of drug retention and implant integrity of subcutaneous implants would allow optimization of therapy and avoid periods of subtherapeutic delivery kinetics. A proof-of principle study was conducted to determine the use of microspatially offset low-frequency Raman spectroscopy (micro-SOLFRS) for nonintrusive in situ analysis of subcutaneous drug delivery systems. Caffeine was used as the model drug, and it was embedded in a circular-shape Soluplus matrix via vacuum compression molding. For the exploratory analysis, prototype implants were positioned underneath skin tissue samples, and various caffeine concentrations (1-50% w/w) and micro-SOLFRS displacement settings (Δz = 0-8 mm) were tested from the pseudo three-dimensional (3D)-imaging perspective. This format allowed the optimization of real-time micro-SOLFRS analysis of implants through skin tissue that was embedded in an agarose hydrogel. Notably, this analytical approach allowed the temporal and spatial erosion of the implant and solid-state transformations of caffeine to be distinguished. The spectrometric results correlated with complementary high-performance liquid chromatography (HPLC) determination of changes in drug concentration, illustrating drug dissipation/diffusion characteristics. The discovered capability of micro-SOLFRS for in situ measurements of drugs and implants makes it attractive for biomedical diagnostics that, ultimately, could result in development of a new point-of-care technology.

Thermosensitive composite based on agarose and chitosan saturated with carbon dioxide. Preliminary study of requirements for production of new CSAG bioink

This study introduces a method for producing printable, thermosensitive bioink formulated from agarose (AG) and carbon dioxide-saturated chitosan (CS) hydrogels. The research identified medium molecular weight chitosan as optimal for bioink production, with a preferred chitosan hydrogel content of 40–60 %. Rheological analysis reveals the bioink's pseudoplastic behavior and a sol-gel phase transition between 27.0 and 31.5 °C. The MMW chitosan-based bioink showed also the most stable extrusion characteristic. The choice of chitosan for the production of bioink was also based on the assessment of the antimicrobial activity of the polymer as a function of its molecular weight and the degree of deacetylation, noting significant cell reduction rates for E. coli and S. aureus of 1.72 and 0.54 for optimal bioink composition, respectively. Cytotoxicity assessments via MTT and LDH tests confirm the bioink's safety for L929, HaCaT, and 46BR.1 N cell lines. Additionally, XTT proliferation assay proved the stimulating effect of the bioink on the proliferation of 46BR.1 N fibroblasts, comparable to that observed with Fetal Bovine Serum (FBS). FTIR spectroscopy confirms the bioink as a physical polymer blend. In conclusion, the CS/AG bioink demonstrates the promising potential for advanced spatial cell cultures in tissue engineering applications including skin regeneration.

Agarose Hydrogel-Boosted One-Tube RPA-CRISPR/Cas12a Assay for Robust Point-of-Care Detection of Zoonotic Nematode Anisakis.

Rapid and accurate detection of the zoonotic nematode Anisakis is poised to control its epidemic. The clustered regularly interspaced short palindromic repeats (CRISPR)/Cas-associated assay shows great potential in the detection of pathogenic microorganisms. The one-tube method integrated the CRISPR system with the recombinase polymerase amplification (RPA) system to avoid the risk of aerosol pollution; however, it suffers from low sensitivity due to the incompatibility of the two systems and additional manual operations. Therefore, in the present study, the agarose hydrogel boosted one-tube RPA-CRISPR/Cas12a assay was constructed by adding the CRISPR system to the agarose hydrogel, which avoided the initially low amplification efficiency of RPA caused by the cleavage of Cas12a and achieved reaction continuity. The sensitivity was 10-fold higher than that of the one-tube RPA-CRISPR/Cas12a system. This method was used for Anisakis detection within 80 min from the sample to result, achieving point-of-care testing (POCT) through a smartphone and a portable device. This study provided a novel toolbox for POCT with significant application value in preventing Anisakis infection.

In-Hydrogel Cell-Free Protein Expression System as Biocompatible and Implantable Biomaterial.

Biomaterials capable of delivering therapeutic proteins are relevant in biomedicine, yet their manufacturing relies on centralized manufacturing chains that pose challenges to their remote implementation at the point of care. This study explores the viability of confined cell-free protein synthesis within porous hydrogels as biomaterials that dynamically produce and deliver proteins to in vitro and in vivo biological microenvironments. These functional biomaterials have the potential to be assembled as implants at the point of care. To this aim, we first entrap cell-free extracts (CFEs) from Escherichia coli containing the transcription-translation machinery, together with plasmid DNA encoding the super folded green fluorescence protein (sGFP) as a model protein, into hydrogels using various preparation methods. Agarose hydrogels result in the most suitable biomaterials to confine the protein synthesis system, demonstrating efficient sGFP production and diffusion from the core to the surface of the hydrogel. Freeze-drying (FD) of agarose hydrogels still allows for the synthesis and diffusion of sGFP, yielding a more attractive biomaterial for its reconstitution and implementation at the point of care. FD-agarose hydrogels are biocompatible in vitro, allowing for the colonization of cell microenvironments along with cell proliferation. Implantation assays of this biomaterial in a preclinical mouse model proved the feasibility of this protein synthesis approach in an in vivo context and indicated that the physical properties of the biomaterials influence their immune responses. This work introduces a promising avenue for biomaterial fabrication, enabling the in vivo synthesis and targeted delivery of proteins and opening new paths for advanced protein therapeutic approaches based on biocompatible biomaterials.

A general strategy for prepared multifunction double-ions agarose hydrogel dressing promotes wound healing

In this study, a new multifunctional double-ions macro-porous agarose hydrogel dressing is proposed, which successfully loaded Ag+ and Li+ simultaneously through the interaction of hydrogen bonds on carboxymethyl agarose (CMA) molecular chains and the interaction of carboxymethyl with metal ions. The macro-porous double-ions hydrogel dressing shows excellent biocompatibility, water-absorbing and water retention capabilities, as well as pH and temperature response characteristics. Moreover, Ag+ ions can be released in the early stage of treatment and Li+ ions can be released steadily and controlled for a long time throughout the treatment, which contributed to effectively antibacterial, and promote tissue regeneration, accelerate wound healing. Significantly, this work provides a general strategy for prepared multifunction double-ions hydrogel dressing with interconnected pores, not limited only to Ag+ and Li+ double-ions, but also Ag+ and Cu2+ double-ions, and Li+ and Cu2+ double-ions, and so on. Thus, the multifunction double-ions hydrogel exhibits a great potential in becoming an effective, efficient and economical wound management dressing. Moreover, this work presents a promising strategy in providing the agarose hydrogel wound dressing to achieve personalized customization ideas.

Effect of Hydrogel Stiffness on Chemoresistance of Breast Cancer Cells in 3D Culture.

Chemotherapy is one of the most common strategies for cancer treatment, whereas drug resistance reduces the efficiency of chemotherapy and leads to treatment failure. The mechanism of emerging chemoresistance is complex and the effect of extracellular matrix (ECM) surrounding cells may contribute to drug resistance. Although it is well known that ECM plays an important role in orchestrating cell functions, it remains exclusive how ECM stiffness affects drug resistance. In this study, we prepared agarose hydrogels of different stiffnesses to investigate the effect of hydrogel stiffness on the chemoresistance of breast cancer cells to doxorubicin (DOX). Agarose hydrogels with a stiffness range of 1.5 kPa to 112.3 kPa were prepared and used to encapsulate breast cancer cells for a three-dimensional culture with different concentrations of DOX. The viability of the cells cultured in the hydrogels was dependent on both DOX concentration and hydrogel stiffness. Cell viability decreased with DOX concentration when the cells were cultured in the same stiffness hydrogels. When DOX concentration was the same, breast cancer cells showed higher viability in high-stiffness hydrogels than they did in low-stiffness hydrogels. Furthermore, the expression of P-glycoprotein mRNA in high-stiffness hydrogels was higher than that in low-stiffness hydrogels. The results suggested that hydrogel stiffness could affect the resistance of breast cancer cells to DOX by regulating the expression of chemoresistance-related genes.

A novel fluorescence probe for ultrafast detection of SO2 derivatives/biogenic amines and its multi-application: Detecting food and fish freshness, fluorescent dye and bioimaging

In this study, we have effectively prepared a novel fluorescent probe named HDXM based on benzopyran derivatives for the ultrafast detection (within 3 s) of SO2 derivatives or biogenic amines. HDXM showed a noticeable color change after the addition of SO2 derivatives (from purple to colorless) or biogenic amines (from purple to blue), indicating that HDXM can identify two analytes with the naked eye. It is worth noting that HDXM can be used to detect SO2 derivatives in actual sugar samples, and to image HSO3−/SO32− in living cells. More importantly, sensing labels (HDXM-loaded filter paper or agarose hydrogel) enable real-time visual monitoring of salmon freshness through colorimetric and fluorescence dual channels. Compared with the Chinese national standard method, the sensing label is an effective tool for evaluating the freshness of fish. Benefiting from its excellent solubility and fluorescence performance, HDXM can be used as a versatile fluorescent material in various applications, including flexible films, glass coatings, impregnating dyes, printing, and fingerprint ink. HDXM is expected to be a promising and valuable multifunctional tool for food safety and fluorescent materials.

UiO-66-NH2 initiated cascade reaction: Constructing a ratiometric fluorescence sensor for ultrasensitive detection of nerve agent simulant

BackgroundHighly toxic organophosphorus nerve agents often exist in the form of gas in the environment and can damage human neuroregulatory system by inhibiting the activity of acetylcholinesterase (AChE). However, fluorescent probes based on small organic molecules bring a secondary burden to environment, and their sensitivity and specificity for sarin simulant diethyl chlorophosphate (DCP) detection are unsatisfactory. Nanozyme cascade systems with signal amplification can be used for highly sensitive identification of analytes, but are rarely used in ratiometric analysis of DCP. Combination of enzyme cascades and ratiometric fluorescence ensures the accuracy and sensitivity of the output signal. ResultsWe prepared a self-assembled nanohybrid (Ag–AuNCs@UiO-66-NH2) by metal-organic framework material and gold nanoclusters. On the one hand, UiO-66-NH2 with enzyme-like activity was used to hydrolyze DCP into diethyl phosphate (DEP) and chloridion (Cl−). Cl− hindered aggregation-induced enhanced emission (AIEE) of AuNCs by binding with Ag+ and decreased the fluorescence of AuNCs. On the other hand, ligand metal charge transfer effect (LMCT) of UiO-66-NH2 was blocked by DCP to enhance the fluorescence of UiO-66-NH2. Combining ratiometric analysis and nanozyme cascade reaction, an ultra-sensitive fluorescence sensor for detecting DCP was constructed, and ensured the accuracy of experimental results. In addition, Ag–AuNCs@UiO-66-NH2 was embedded into the agarose hydrogel substrate, the resulting agarose hydrogel film allowed quantitative assessment of DCP vapor and high sensitivity was demonstrated (detection limit as low as 1.02 ppb). SignificanceA strategy combining enzyme cascade with ratiometric fluorescence was proposed, which improved the accuracy and sensitivity of the analysis results. The soft-solid platform based on agarose hydrogel film was constructed to realize the quantitative monitoring of sarin simulant gas. The LOD value obtained in this work is much lower than the immediately life-threatening or health threatening concentration of sarin.