Controllable detection threshold achieved through the toehold switch system in a mercury ion whole-cell biosensor.

Due to the toxicity of mercury and its harmful effects on human health, it is essential to establish a low-cost, highly sensitive and highly specific monitoring method with a wide detection range, ideally with a simple visual readout. In this study, a whole-cell biosensor with adjustable detection limits was developed for the detection of mercury ions in water samples, allowing controllable threshold detection with an expanded detection range. Gene circuits were constructed by combining the toehold switch system with lactose operon, mercury-ion-specific operon, and inducible red fluorescent protein gene. Using MATLAB for design and selection, a total of eleven dual-input single-output sensing logic circuits were obtained based on the basic logic of gene circuit construction. Then, biosensor DTS-3 was selected based on its fluorescence response at different isopropyl ß-D-Thiogalactoside (IPTG) concentrations, exhibiting the controllable detection threshold. At 5-20 µM IPTG, DTS-3 can achieve variable threshold detection in the range of 0.005-0.0075, 0.06-0.08, 1-2, and 4-6 µM mercury ion concentrations, respectively. Specificity experiments demonstrated that DTS-3 exhibits good specificity, not showing fluorescence response changes compared with other metal ions. Furthermore spiked sample experiments demonstrated its good resistance to interference, allowing it to distinguish mercury ion concentrations as low as 7.5 nM by the naked eye and 5 nM using a microplate reader. This study confirms the feasibility and performance of biosensor with controllable detection threshold, providing a new detection method and new ideas for expanding the detection range of biosensors while ensuring rapid and convenient measurements without compromising sensitivity.

Adsorption of Hg2+/Cr6+ by metal-binding proteins heterologously expressed in Escherichia coli.

BACKGROUND: Removal of heavy metals from water and soil is a pressing challenge in environmental engineering, and biosorption by microorganisms is considered as one of the most cost-effective methods. In this study, the metal-binding proteins MerR and ChrB derived from Cupriavidus metallidurans were separately expressed in Escherichia coli BL21 to construct adsorption strains. To improve the adsorption performance, surface display and codon optimization were carried out. RESULTS: In this study, we constructed 24 adsorption engineering strains for Hg2+ and Cr6+, utilizing different strategies. Among these engineering strains, the M'-002 and B-008 had the strongest heavy metal ion absorption ability. The M'-002 used the flexible linker and INPN to display the merRopt at the surface of the E. coli BL21, whose maximal adsorption capacity reached 658.40 µmol/g cell dry weight under concentrations of 300 µM Hg2+. And the B-008 overexpressed the chrB in the intracellular, its maximal capacity was 46.84 µmol/g cell dry weight under concentrations 500 µM Cr6+. While in the case of mixed ions solution (including Pb2+, Cd2+, Cr6+ and Hg2+), the total amount of ions adsorbed by M'-002 and B-008 showed an increase of up to 1.14- and 4.09-folds, compared to the capacities in the single ion solution. CONCLUSION: The construction and optimization of heavy metal adsorption strains were carried out in this work. A comparison of the adsorption behavior between single bacteria and mixed bacteria systems was investigated in both a single ion and a mixed ion environment. The Hg2+ absorption capacity is reached the highest reported to date with the engineered strain M'-002, which displayed the merRopt at the surface of chassis cell, indicating the strain's potential for its application in practical environments.

Biologically produced and metal-organic framework delivered dual-cut CRISPR/Cas9 system for efficient gene editing and sensitized cancer therapy.

Manipulation of the lactate metabolism is an efficient way for cancer treatment given its involvement in cancer development, metastasis, and immune escape. However, most of the inhibitors of lactate transport carriers suffer from poor specificity. Herein, we use the CRISPR/Cas9 system to precisely downregulate the monocarboxylate carrier 1 (MCT1) expression. To avoid the self-repairing during the gene editing process, a dual-Cas9 ribonucleoproteins (duRNPs) system is generated using the biological fermentation method and delivered into cells by the zeolitic imidazolate framework-8 (ZIF-8) nanoparticles, enabling precise removal of a specific DNA fragment from the genome. For efficient cancer therapy, a specific glucose transporter 1 inhibitor (BAY-876) is co-delivered with the duRNPs, forming BAY/duRNPs@ZIF-8 nanoparticle. ZIF-8 nanoparticles can deliver the duRNPs into cells within 1 h, which efficiently downregulates the MCT1 expression, and prohibits lactate influx. Through simultaneous inhibition of the lactate and glucose influx, BAY/duRNPs@ZIF-8 prohibits ATP generation, arrests cell cycle, inhibits cell proliferation, and finally induces cellular apoptosis both in vitro and in vivo. Consequently, we demonstrate that the biologically produced duRNPs delivered into cells by the nonviral ZIF-8 carrier have expanded the CRISPR/Cas gene editing toolbox and elevated the gene editing efficiency, which will promote biological studies and clinical applications. STATEMENT OF SIGNIFICANCE: The CRISPR/Cas9 system, widely used as an efficient gene editing tool, faces a challenge due to cells' ability to self-repair. To address this issue, a strategy involving dual-cutting of the genome DNA has been designed and implemented. This strategy utilizes biologically produced dual-ribonucleoproteins delivered by a metal-organic framework. The effectiveness of this dual-cut CRISPR-Cas9 system has been demonstrated through a therapeutic approach targeting the simultaneous inhibition of lactate and glucose influx in cancer cells. The utilization of the dual-cut gene editing strategy has provided valuable insights into gene editing and expanded the toolbox of the CRISPR/Cas-based gene editing system. It has the potential to enable more efficient and precise manipulation of specific protein expression in the future.

Melanoidin-like carbohydrate-containing macromolecules from Shanxi aged vinegar exert immunoenhancing effects on macrophage RAW264.7 cells.

Bioactive macromolecule mining is important for the functional chemome analysis of traditional Chinese vinegar. In this study, we isolated and characterized carbohydrate-containing macromolecules from Shanxi aged vinegar (CCMSAV) and evaluated their immunomodulatory activity. The isolation process involved ethanol precipitation, deproteinization, decolorization, and DEAE-650 M column chromatography, resulting in the acquisition of four sub-fractions. All sub-fractions exhibited a molecular weight range of 6.92 to 16.71 kDa and were composed of 10 types of monosaccharides. Comparative analysis of these sub-fractions with two melanoidins exhibited similarities in elemental composition, spectral signature, and pyrolytic characteristics. Immunological assays confirmed the significantly enhanced cell viability, phagocytic activity, and secretion of nitric oxide, tumor necrosis factor (TNF)-α and interleukin (IL)-6 in RAW264.7 cells by all four sub-fractions. Further investigation of the immunomodulatory mechanism revealed that SAV-RP70-X, the most potent purified sub-fraction, enhanced aerobic glycolysis in macrophages and activated Toll-like receptor 2 (TLR2), TLR4, mannose receptor (MR), scavenger receptor (SR), and the dendritic cell-associated C-type lectin-1 receptor (Dectin-1). Furthermore, the activation of macrophages was associated with the MyD88/PI3K/Akt/NF-κB signaling pathway. Methylation analysis revealed that 1,4-Xylp was the most abundant glycosidic linkage in SAV-RP70-X.

Metallopolymer strategy to explore hypoxic active narrow-bandgap photosensitizers for effective cancer photodynamic therapy.

Practical photodynamic therapy calls for high-performance, less O2-dependent, long-wavelength-light-activated photosensitizers to suit the hypoxic tumor microenvironment. Iridium-based photosensitizers exhibit excellent photocatalytic performance, but the in vivo applications are hindered by conventional O2-dependent Type-II photochemistry and poor absorption. Here we show a general metallopolymerization strategy for engineering iridium complexes exhibiting Type-I photochemistry and enhancing absorption intensity in the blue to near-infrared region. Reactive oxygen species generation of metallopolymer Ir-P1, where the iridium atom is covalently coupled to the polymer backbone, is over 80 times higher than that of its mother polymer without iridium under 680 nm irradiation. This strategy also works effectively when the iridium atom is directly included (Ir-P2) in the polymer backbones, exhibiting wide generality. The metallopolymer nanoparticles exhibiting efficient O2•- generation are conjugated with integrin αvß3 binding cRGD to achieve targeted photodynamic therapy.

The Balance Effect of π-π Electronic Coupling on NIR-II Emission and Photodynamic Properties of Highly Hydrophobic Conjugated Photosensitizers.

Deep NIR organic phototheranostic molecules generally have large π-conjugation structures and show highly hydrophobic properties, thus, forming strong π-π stacking in the aqueous medium, which will affect the phototheranostic performance. Herein, an end-group strategy is developed to lift the performance of NIR-II emitting photosensitizers. Extensive characterizations reveal that the hydrogen-bonding interactions of the hydroxyl end group can induce a more intense π-π electronic coupling than the chlorination-mediated intermolecular forces. The results disclose that π-π stacking will lower fluorescence quantum yield but significantly benefit the photodynamic therapy (PDT) efficiency. Accordingly, an asymmetrically substituted derivative (BTIC-δOH-2Cl) is developed, which shows balanced phototheranostic properties with excellent PDT efficiency (14.6 folds of ICG) and high NIR-II fluorescence yield (2.27%). It proves the validity of the end-group strategy on controlling the π-π interactions and rational tuning the performance of NIR-II organic phototheranostic agents.

Comparative Analysis of Six Chloroplast Genomes in Chenopodium and Its Related Genera (Amaranthaceae): New Insights into Phylogenetic Relationships and the Development of Species-Specific Molecular Markers.

Species within the genus Chenopodium hold significant research interest due to their nutritional richness and salt tolerance. However, the morphological similarities among closely related species and a dearth of genomic resources have impeded their comprehensive study and utilization. In the present research, we conduct the sequencing and assembly of chloroplast (cp) genomes from six Chenopodium and related species, five of which were sequenced for the first time. These genomes ranged in length from 151,850 to 152,215 base pairs, showcased typical quadripartite structures, and encoded 85 protein-coding genes (PCGs), 1 pseudogene, 37 tRNA genes, and 8 rRNA genes. Compared with the previously published sequences of related species, these cp genomes are relatively conservative, but there are also some interspecific differences, such as inversion and IR region contraction. We discerned 929 simple sequence repeats (SSRs) and a series of highly variable regions across 16 related species, predominantly situated in the intergenic spacer (IGS) region and introns. The phylogenetic evaluations revealed that Chenopodium is more closely related to genera such as Atriplex, Beta, Dysphania, and Oxybase than to other members of the Amaranthaceae family. These lineages shared a common ancestor approximately 60.80 million years ago, after which they diverged into distinct genera. Based on InDels and SNPs between species, we designed 12 pairs of primers for species identification, and experiments confirmed that they could completely distinguish 10 related species.

Ultra-stable MOF@MOF nanoplatform for photodynamic therapy sensitized by relieved hypoxia due to mitochondrial respiration inhibition.

Metal-organic frameworks (MOFs) with periodically arranged porphyrinic linkers avoiding the self-quenching issue of porphyrins in photodynamic therapy (PDT) have been widely applied. However, the porphyrinic MOFs still face challenges of poor stability under physiological conditions and limited photodynamic efficiency by the hypoxia condition of tumors. Herein, we fabricate the MOF@MOF structure with a protective MOF shell to improve the stability and relieve the hypoxia condition of tumors for sensitized PDT. Under protection of the MOF shell, the MOF@MOF structure can keep intact for 96 h under physiological conditions. Consequently, the tumoral accumulation efficiency is two folds of the MOF core. Furthermore, the MOF shell decomposes under acidic environment, and the loaded inhibitor of mitochondria pyruvate carrier (7-amino carboxycoumarins-2, 7ACC2) will be released. 7ACC2 inhibits the mitochondrial pyruvate influx and simultaneously blocks glucose and lactate from fueling the mitochondrial respiration, thereupon relieving the hypoxia condition of tumors. Under a 5-min laser irradiation, the 7ACC2 carrying MOF@MOF nanoplatforms induced doubled cellular apoptosis and reduced 70% of the tumor growth compared with the cargo-free MOF@MOF. In summary, the design of this stable and hypoxia self-relievable MOF@MOF nanoplatform will enlighten the future development of MOF-based nanomedicines and PDT. STATEMENT OF SIGNIFICANCE: Though widely used for photodynamic therapy (PDT) in previous studies, porphyrinic metal-organic frameworks (MOFs) still face challenges in poor stability under physiological conditions and limited photodynamic efficiency due to the hypoxia condition of tumors. In order to solve these problems, (1) we develop the MOF@MOF strategy to improve the physiological stability; (2) an inhibitor of mitochondria pyruvate carrier, 7-amino carboxycoumarins-2 (7ACC2), is loaded to inhibit the mitochondrial pyruvate influx and simultaneously block glucose and lactate from fueling the mitochondrial respiration, thereupon relieving the hypoxia condition of tumors. In comparison with previous studies, our strategy simultaneously improves stability and overcomes the limited PDT efficiency in the hypoxia tumor tissue, which will enlighten the future development of MOF-based nanomedicines and PDT.

Effect of 3-caffeoylquinic acid on growth performance, nutrient digestibility, and intestinal functions in weaned pigs.

Phenolic acid like with the 3-caffeoylquini acid (3-CQA) is formed by caffeic acid and qunic acid. This study was conducted to explore the effect of 3-CQA on growth performance and intestinal functions in weaned pigs. A total of 180 weaned pigs were randomly allocated into five treatments with 6 replicate pens per treatment (6 pigs per pen). Pigs in the control group (CON) were fed with basal diet (BD), and the others in the experimental groups were fed with BD and supplemented with 12.5, 25, 50, and 100 mg/kg 3-CQA. On day 43, the blood sample-collected pigs in the CON and optimal-dose group (only based on growth performance) were picked, and housed in metabolism cages (a total of 12 pigs, N = 6). 3-CQA increased the feed efficiency from days 21 to 42 of the trial and throughout the trial (P < 0.05). 3-CQA increased the serum concentrations of total protein, albumin, and total cholesterol (P < 0.05). Moreover, 3-CQA supplementation at 25 mg/kg increased the apparent digestibility of DM, energy, and ash (P < 0.05). Interestingly, 3-CQA decreased the crypt depth but increased the ratio of villus height to crypt depth in the jejunum and ileum (P < 0.05). Moreover, 3-CQA also increased the activities of sucrase, lactase, and catalase in the jejunal mucosa, and increased the activities of alkaline phosphatase and superoxide dismutase in the ileal mucosa (P < 0.05). 3-CQA also increased the abundance of secretory immunoglobulin A in the ileal mucosa (P < 0.05). Importantly, 3-CQA not only elevated the expression levels of critical functional genes such as the zonula occludens-1 , occludin, solute carrier family 7 , and nuclear factor erythroid 2-related factor 2 (Nrf2) in the duodenum but also elevated the expression levels of divalent metal transporter-1 and Nrf2 in the jejunum (P < 0.05). These results suggested a positive effect of 3-CQA supplementation on the growth and intestinal functions of weaned pigs. The mechanisms of action may be associated with elevated anti-oxidant capacity and improved intestinal barrier functions.

In last decades, swine producers used antibiotics as growth promoter added into diet. However, the pharmaceutical use of antibiotics is prohibited by the legislation of several countries due to potential health and environmental concerns. Therefore, the development of substitutes for traditionally used antibiotics has attracted considerable research interest worldwide. Natural phnolic acid like with the 3-CQA is an important component of biologically active phenols isolated from various natural plants. This study was carried out to evaluate the effect of 3-CQA on growth performance, nutrient digestibility, and intestinal functions in pigs. Results indicated that dietary 3-CQA supplementation improved the growth performance, nutrients digestibility in weaned pigs. The beneficial effects of 3-CQA supplementation on growth and intestinal functions suggested that it could serve as a natural potent substitute for antibiotics.

Self-Immolative Photosensitizers for Self-Reported Cancer Phototheranostics.

Photosensitizers to precise target and change fluorescence upon light illumination could accurately self-report where and when the photosensitizers work, enabling us to visualize the therapeutic process and precisely regulate treatment outcomes, which is the unremitting pursuit of precision and personalized medicine. Here, we report self-immolative photosensitizers by adopting a strategy of light-manipulated oxidative cleavage of C═C bonds that can generate a burst of reactive oxygen species, to cleave to release self-reported red-emitting products and trigger nonapoptotic cell oncosis. Strong electron-withdrawing groups are found to effectively suppress the C═C bond cleavage and phototoxicity via studying the structure-activity relationship, allowing us to elaborate NG1-NG5 that could temporarily inactivate the photosensitizer and quench the fluorescence by different glutathione (GSH)-responsive groups. Thereinto, NG2 with 2-cyano-4-nitrobenzene-1-sulfonyl group displays excellent GSH responsiveness than the other four. Surprisingly, NG2 shows better reactivity with GSH in weakly acidic condition, which inspires the application in weakly acidic tumor microenvironment where GSH elevates. To this end, we further synthesize NG-cRGD by anchoring integrin αvß3 binding cyclic pentapeptide (cRGD) for tumor targeting. In A549 xenografted tumor mice, NG-cRGD successfully deprotects to restore near-infrared fluorescence because of elevated GSH in tumor site, which is subsequently cleaved upon light irradiation releasing red-emitting products to report photosensitizer working, while effectively ablating tumors via triggered oncosis. The advanced self-immolative organic photosensitizer may accelerate the development of self-reported phototheranostics in future precision oncology.

Divergent Radical Cyclization and Hydroaminoalkylation of N-Arylacrylamides Using Photoredox Catalysis.

The ability to selectively synthesize multiple products from the same sets of substrates is a highly appealing and challenging concept in synthetic chemistry. In this manuscript, we describe the visible-light photoredox intermolecular catalysis of N-arylacrylamides that are α-C-H functionalized with aryl tertiary amines. The photocatalyst acts as a chemical switch to trigger two different reaction pathways and to obtain two different products from the same starting material. Simple adjustments to the reaction conditions enable the divergent synthesis of the oxidative cyclizations or the addition products in good to high yields with excellent atom economy.

Chlorination-Mediated π-π Stacking Enhances the Photodynamic Properties of a NIR-II Emitting Photosensitizer with Extended Conjugation.

NIR-II-emitting photosensitizers (PSs) have attracted great research interest due to their promising clinical applications in imaging-guided photodynamic therapy (PDT). However, it is still challenging to realize highly efficient PDT on NIR-II PSs. In this work, we develop a chlorination-mediated π-π organizing strategy to improve the PDT of a PS with conjugation-extended A-D-A architecture. The significant dipole moment of the carbon-chlorine bond and the strong intermolecular interactions of chlorine atoms bring on compact π-π stacking in the chlorine-substituted PS, which facilitates energy/charge transfer and promotes the photochemical reactions of PDT. Consequently, the resultant NIR-II emitting PS exhibits a leading PDT performance with a yield of reactive oxygen species higher than that of previously reported long-wavelength PSs. These findings will enlighten the future design of NIR-II emitting PSs with enhanced PDT efficiency.

One-Pot Rapid Synthesis of Cu2+-Doped GOD@MOF to Amplify the Antitumor Efficacy of Chemodynamic Therapy.

Chemodynamic therapy (CDT) relies on the transformation of intracellular hydrogen peroxide (H2O2) to hydroxyl radicals (·OH) with higher toxicity under the catalysis of Fenton/Fenton-like reagents, which amplifies the oxidative stress and induces significant cellular apoptosis. However, the CDT efficacy is generally limited by the overexpressed GSH and insufficient endogenous H2O2 in tumors. Co-delivery of Cu2+ and glucose oxidase (GOD) can lead to a Cu2+/Cu+ circulation to realize GSH depletion and amplify the Fenton-like reaction. pH-responsive metal-organic frameworks (MOFs) are the optical choice to deliver Fenton/Fenton-like ions to tumors. However, considering that the aqueous condition is requisite for GOD encapsulation, it is challenging to abundantly dope Cu2+ in ZIF-8 MOF nanoparticles in aqueous conditions due to the ease of precipitation and enlarged crystal size. In this work, a robust one-pot biomimetic mineralization method using excessive ligand precursors in aqueous conditions is developed to synthesize GOD@Cu-ZIF-8. Copper ions abundantly doped to the GOD@Cu-ZIF-8 can eliminate GSH to produce Cu+, which is further proceeded to the Fenton-like reaction in the presence of GOD-catalyzed H2O2. Through breaking the tumor microenvironment homeostasis and producing an enhanced CDT effect, the promising antitumor capability of GOD@Cu-ZIF-8 was evidenced by the experiments both in vitro and in vivo.

NIR-II Luminescent and Multi-Responsive Rare Earth Nanocrystals for Improved Chemodynamic Therapy.

Chemodynamic therapy (CDT) based on the Fe2+-mediated Fenton reaction can amplify intracellular oxidative stress by producing toxic •OH. However, the high-dose need for Fe2+ delivery in tumors and its significant cytotoxicity to normal tissues set a challenge. Therefore, a controllable delivery to activate the Fenton reaction and enhance Fe2+ tumor accumulation has become an approach to solve this conflict. Herein, we report a rare-earth-nanocrystal (RENC)-based Fe2+ delivery system using light-control techniques and DNA nanotechnology to realize programmable Fe2+ delivery. Ferrocenes, the source of Fe2+, are modified on the surface of RENCs through pH-responsive DNAs, which are further shielded by a PEG layer to elongate blood circulation and "turn off" the cytotoxicity of ferrocene. The up-/down-conversion dual-mode emissions of RENCs endow the delivery system with both capabilities of diagnosis and delivery control. The down-conversion NIR-II fluorescence can locate tumors. Consequently, up-conversion UV light spatiotemporally activates the catalytic activity of Fe2+ by shedding off the protective PEG layer. The exposed ferrocene-DNAs not only can "turn on" Fenton catalytic activity but also respond to tumor acidity, driving cross-linking and enhanced Fe2+ enrichment in tumors by 4.5-fold. Accordingly, this novel design concept will be inspiring for developing CDT nanomedicines in the future.

Towards interactive deep-learning for tumour segmentation in head and neck cancer radiotherapy.

Background and purpose: With deep-learning, gross tumour volume (GTV) auto-segmentation has substantially been improved, but still substantial manual corrections are needed. With interactive deep-learning (iDL), manual corrections can be used to update a deep-learning tool while delineating, minimising the input to achieve acceptable segmentations. We present an iDL tool for GTV segmentation that took annotated slices as input and simulated its performance on a head and neck cancer (HNC) dataset. Materials and methods: Multimodal image data of 204 HNC patients with clinical tumour and lymph node GTV delineations were used. A baseline convolutional neural network (CNN) was trained (n = 107 training, n = 22 validation) and tested (n = 24). Subsequently, user input was simulated on initial test set by replacing one or more of predicted slices with ground truth delineation, followed by re-training the CNN. The objective was to optimise re-training parameters and simulate slice selection scenarios while limiting annotations to maximally-five slices. The remaining 51 patients were used as an independent test set, where Dice similarity coefficient (DSC), mean surface distance (MSD), and 95% Hausdorff distance (HD95%) were assessed at baseline and after every update. Results: Median segmentation accuracy at baseline was DSC = 0.65, MSD = 4.3 mm, HD95% = 17.5 mm. Updating CNN using three slices equally sampled from the craniocaudal axis of the GTV in the first round, followed by two rounds of annotating one extra slice, gave the best results. The accuracy improved to DSC = 0.82, MSD = 1.6 mm, HD95% = 4.8 mm. Every CNN update took 30 s. Conclusions: The presented iDL tool achieved substantial segmentation improvement with only five annotated slices.

Photocatalyst-free visible light driven synthesis of gem-dihaloenones from alkynes, tetrahalomethanes and water.

Photocatalytic reactions, in particular, processes without photosensitisers, have attracted increased attention due to their green aspect and high economic value and are considered valuable tools in organic synthesis. A new practical photocatalytic system was investigated in this study, and it can efficiently produce gem-dihaloenones by combining terminal alkynes with tetrahalomethanes (BrCCl3 and CBr4) and water without a photocatalyst, and the yield can reach up to 87%. The catalytic system is straightforward, the raw materials are inexpensive and easy to obtain, and the operation is simple.

The Research Field of Meat Preservation: A Scientometric and Visualization Analysis Based on the Web of Science.

Meat plays a significant role in human diets, providing a rich source of high-quality protein. With advancements in technology, research in the field of meat preservation has been undergoing dynamic evolution. To gain insights into the development of this discipline, the study conducted an analysis and knowledge structure mapping of 1672 papers related to meat preservation research within the Web of Science Core Collection (WOSCC) spanning from 2001 to 2023. And using software tools such as VOSviewer 1.6.18 and CiteSpace 5.8.R3c allowed for the convenient analysis of the literature by strictly following the software operation manuals. Moreover, the knowledge structure of research in the field of meat preservation was synthesized within the framework of "basic research-technological application-integration of technology with fundamental research," aligning with the research content. Co-cited literature analysis indicated that meat preservation research could be further categorized into seven collections, as well as highlighting the prominent role of the antibacterial and antioxidant properties of plant essential oils in ongoing research. Subsequently, the future research direction and focus of the meat preservation field were predicted and prospected. The findings of this study could offer valuable assistance to researchers in swiftly comprehending the discipline's development and identifying prominent research areas, thus providing valuable guidance for shaping research topics.

A pH-responsive T1-T2 dual-modal MRI contrast agent for cancer imaging.

Magnetic resonance imaging (MRI) is a non-invasive imaging technology to diagnose health conditions, showing the weakness of low sensitivity. Herein, we synthesize a contrast agent, SPIO@SiO2@MnO2, which shows decreased T1 and T2 contrast intensity in normal physiological conditions. In the acid environment of tumor or inflamed tissue, the manganese dioxide (MnO2) layer decomposes into magnetically active Mn2+ (T1-weighted), and the T1 and T2 signals are sequentially recovered. In addition, both constrast quenching-activation degrees of T1 and T2 images can be accurately regulated by the silicon dioxide (SiO2) intermediate layer between superparamagnetic iron oxide (SPIO) and MnO2. Through the "dual-contrast enhanced subtraction" imaging processing technique, the contrast sensitivity of this MRI contrast agent is enhanced to a 12.3-time difference between diseased and normal tissue. Consequently, SPIO@SiO2@MnO2 is successfully applied to trace the tiny liver metastases of approximately 0.5 mm and monitor tissue inflammation.

Changes in the Physical-Chemical Properties and Volatile Flavor Components of Dry-Cured Donkey Leg during Processing.

In order to explore the quality variation and flavor formation of dry-cured donkey leg, the changes in physical−chemical composition, lipolytic, free amino acids content and volatile flavor compounds were investigated in this study. Six fresh, trimmed hind legs with average weight of 8.12 ± 0.8 kg were taken from male Dezhou donkeys slaughtered at the age of 24 months with the average live weight of 240 kg. The entire processing time was eight months long including six stages, specifically: cooling, salting, air-drying, fermenting and aging. Samples were collected at 0 d, 10 d, 20 d, 30 d, 65 d, 105 d and 165 d of processing. The results showed that the pH value remained stable in the range of 6.2~6.6. The moisture and water activity significantly decreased (p < 0.05) during processing. The chloride content, ash, total volatile basic nitrogen (TVB-N) and peroxide value (POV) significantly increased (p < 0.05), from 0.45% to 12.39%, from 3% to 17%, from 1.43 mg/kg to 8.98 mg/kg and from 1.39 g/100 g to 5.26 g/100 g, respectively. The thiobarbituric acid (TBARS) value reached its highest value of 0.39 mg MDA/kg at the end of the salting stage and then decreased to 0.34 mg MDA/kg. Eighteen free amino acids and fifteen free fatty acids were detected, and their contents were significantly increased during processing (p < 0.05). Volatile compounds were analyzed using solid-phase microextraction (SPME) and gas chromatography−mass spectrometry (GC−MS). Among 114 volatile compounds detected in dry-cured donkey leg, aldehydes, esters, alkane and alcohols were more abundant in the final products, with relative concentrations of 41.88%, 5.72%, 5.35% and 5.25%, respectively. Processing significantly affected the physical−chemical properties, which could contribute to the formation of flavor substances of dry-cured donkey leg.