Construction of ratiometric fluorescence sensor and test strip with smartphone based on dual-emission carbon dots for the specific detection of chlortetracycline

Concerns about environmental and food contamination caused by chlortetracycline (CTC) residues have prompted people to explore efficient and convenient CTC monitoring platforms. However, the reported fluorescent probes generally fail to selectively detect CTC due to the structural similarity of tetracycline antibiotics. Herein, an intrinsic dual-emission carbon dots (D-CDs) ratiometric fluorescence sensor was prepared for highly sensitive and selective determination of CTC over other tetracyclines by one-step synthesis. The sensor exhibited a significant fluorescence enhancement at 425 nm after introducing CTC. The fluorescence "turn on" of the sensing system is due to aggregation-induced emission (AIE) phenomenon formed by hydrogen bonds and π conjugation promoting the specific recognition of CTC by D-CDs. The linear detection varied from 0.98 to 143.67 ng mL^-1 with a low limit of detection (LOD) of 1.29 ng mL^-1 (R² = 0.998), which was lower than most reported in the literature. The D-CDs sensor was applied to detect CTC in spiked milk, blocked normal human serum, and fish samples with recoveries of 95.5-104.2% and relative standard deviations (RSDs) of 2.6%. Particularly, D-CDs based test papers with a smartphone were prepared for portable and visual detection of CTC by analyzing the various color changes of RGB of fluorescence color, with an LOD of 7.18 ng mL^-1 (R² = 0.9909). The fluorescence sensor designed in this work could be used as a rapid tool with high performance and selectivity for monitoring control in foods.

Label-free fluorescence aptasensor for the detection of patulin using target-induced DNA gates and TCPP/BDC-NH2 mixed ligands functionalized Zr-MOF systems

Patulin (PAT) is an unsaturated lactone mycotoxin primarily produced by Penicillium expansum and Aspergillus clavatus. Given the potential health risks and economic losses associated with PAT, the rapid detection of PAT using fluorescent aptasensors is of significant importance in evaluating food safety. However, it easily increases the cost and complexity caused by signal labeling. We combined TCPP/BDC-NH₂ mixed ligands functionalized Zr metal-organic frameworks (Zr-MOF_mix) and terminated three-stranded DNA gates (ttsDNA gates) to fabricate a label-free fluorescent aptasensor for PAT detection. The Zr-MOF_mix system was synthesized via a one-pot strategy and could be used to address the problem of pore size limitation and increase the loading amounts of dyes. TtsDNA gate was integrated into the Zr-MOF_mix system to control the release of dyes, exhibiting a high signal-to-background ratio. The single-stranded aptamer region in ttsDNA gate situated away from the surface of the Zr-MOF_mix, resulting in a natural release of dyes in the absence of PAT. While binding to PAT resulted in target-induced conformational changes that helped form the hairpin structure of the aptamer. This structure hindered the release of dyes from the pores of Zr-MOF_mix, thus reducing the fluorescence signals intensity. The stimuli-responsive DNA-gated material provides a platform for PAT analysis under conditions of a low limit of detection (0.871 pg/mL). Furthermore, the excellent specificity and anti-interference of the fluorescent aptasensor make the system suitable for the analysis of apple juice samples. This label-free strategy is cheaper and simper compared with labeled detection, especially for the development of multi-target-detection.

Synthesis of silver/Fe3O4@chitosan@polyvinyl alcohol magnetic nanoparticles as an antibacterial agent for accelerating wound healing

Bacterial infection causes wound inflammation and slows wound healing, posing a great threat to human health, which needs to explore more antibacterial nanobiomaterials to promote wound healing. Therefore, this study was conducted to develop low-cost silver/Fe₃O₄@Chitosan@polyvinyl alcohol (Ag/Fe₃O₄@CS@PVA) via a one-pot method to promote healing in bacteria-infected wounds. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM) confirmed that Ag/Fe₃O₄@CS@PVA was successfully prepared. In vitro antibacterial experiments demonstrated strong antibacterial activity of Ag/Fe₃O₄@CS@PVA against Escherichia coli and Staphylococcus aureus. The Ag/Fe₃O₄@CS@PVA destroyed the bacterial cell membrane or internal structure, thus resulting in cell death for antibacterial effects. Cytotoxicity and hemolysis rate tests showed that Ag/Fe₃O₄@CS@PVA posed fine biocompatibility. In addition, in vivo assays confirmed that Ag/Fe₃O₄@CS@PVA not only promoted the healing of wound infection caused by bacteria, but also had no toxic effect on mouse organs. Therefore, the low-cost Ag/Fe₃O₄@CS@PVA nanocomposites have great potential in controlling 'bacterial' pathogen.

Using hyperspectral imaging technology for assessing internal quality parameters of persimmon fruits during the drying process

The crucial features of persimmon are required to detect real-time moisture, water-soluble tannin, and soluble solids contents during the drying process. This study developed a method based on hyperspectral imaging (HSI) to execute online and non-destructive assaying of persimmon features. A total of 144 samples were collected, and 150 bands were scanned. The spectral data were analyzed by partial least squares regression (PLSR), principal component regression (PCR), least squares support vector regression (LS-SVR), and radial basis function neural network (RBFNN) with seven preprocessing methods. LS-SVR provided excellent performance for moisture content prediction, while PLSR was better in the analysis of water-soluble tannin and soluble solids contents. Successive projection algorithm (SPA) was used to select the optimal wavelengths to simplify the models, and about twenty important variables were chosen. Overall, these results indicate that HSI could be considered a valuable technique to quantify chemical constituents in dried persimmon fruits.

Effects of sulfite treatment on the quality of black fungus

In the present study, the color, total sugar, contents of soluble protein, total polyphenols, total flavonoids, and soluble vitamins, and other indicators of black fungus treated with sodium metabisulfite under different conditions were measured to evaluate the sensory and nutritional changes in black fungus after sulfite treatment. The results showed that use of sodium metabisulfite increased the lightness of black fungus, significantly increased the contents of total polyphenols and reducing sugars in the fungus (p < 0.05), increased the content of soluble protein, and decreased the content of total flavonoids. In addition, sodium metabisulfite destroyed vitamin C and B₁ in black fungus. When the concentration of sodium metabisulfite was 0.5% and the soaking time 20 or 30 min, the color of black fungus improved markedly, and nutrients were not negatively affected. Therefore, the use of sodium metabisulfite improved the quality of fungus to a certain extent.

Self-propelled nanomotors based on hierarchical metal-organic framework composites for the removal of heavy metal ions

The outstanding performance efficiency for the removal of heavy metal ions in solution is governed by various factors: (a) sufficient contact probability between heavy metal ions and the adsorbent, (b) convenient diffusion/accessibility of heavy metal ions to the surface and the interior of the adsorbent, and (c) abundant binding sites for heavy metal ions on the adsorbent. We designed an efficient MnFe₂O₄ @MIL-53 @UiO-66 @MnO₂ adsorbent for Pb(II) and Cd(II) removal. The adsorbents were fabricated by merging self-propelled nanomotors, exploiting hierarchical structure, and using a metal-organic framework (MOF) composite to simultaneously meet the three requirements. The sufficient contact probability between Pb(II)/Cd(II) and MnFe₂O₄ @MIL-53 @UiO-66 @MnO₂ was achieved via the self-propelled movement of MnFe₂O₄ @MIL-53 @UiO-66 @MnO₂ which was induced by the catalytic decomposition of H₂O₂ by MnO₂. The convenient diffusion/accessibility of Pb(II)/Cd(II) on the surface and interior of MnFe₂O₄ @MIL-53 @UiO-66 @MnO₂ was achieved by exploiting the properties of the hierarchical structure of MnFe₂O₄ @MIL-53 @UiO-66 @MnO₂. Abundant binding sites (-COOH) on MIL-53 and UiO-66 composites were present for the binding of the Pb(II)/Cd(II) ions to the adsorbent. The adsorption capacities of the nanomotor adsorbent for Pb(II) and Cd(II) were 1018 and 440.8 mg g^-1 at 25 °C, respectively. Additionally, the complex formed of MnFe₂O₄ and MIL-53 endowed the adsorbent with easy-recyclable properties under the influence of an external magnet. The nanomotors exhibit satisfactory removal performances for Pb(II) and Cd(II).

Color-Tunable Fluorescent Hierarchical Nanoassemblies with Concentration-Encoded Emission

Cephalopods possess a dynamic coloration behavior to change their iridescence due to the concentration-induced optical properties of chromatophores and hierarchical assembly of reflectin. However, cephalopods rarely have iridescence in the darkfield. It would be interesting to develop color-tunable fluorescent hierarchical nanoassemblies with concentration-encoded emission. Herein, to construct the bioavailable fluorophore with dynamic coloration properties, a histidine-rich peptide is designed, which can self-assemble into hierarchical nanoassemblies stabilized by hydrogen bonds and π-π stacking interactions. The peptidyl nanoassemblies emit fluorescent iridescence, encompassing the blue to orange region due to the assembly-induced emission. The fluorescence of histidine-rich peptides is color-tunable and reversible, which can be dynamically controlled in a concentration-encoded mode. Due to the coloration ability of histidine-rich peptides, fluorescent polychromatic human cells are developed, highlighting its potential role as a fluorescent candidate for future applications such as bioimaging, implantable light-emitting diodes, and photochromic camouflage.

Silver nanoparticles anchored magnetic self-assembled carboxymethyl cellulose-ε-polylysine hybrids with synergetic antibacterial activity for wound infection therapy

The severe bacterial infection and chronic wound healing caused by the abuse of antibiotics threaten the public health, which calls the need for the development of novel antibacterial agents and alternative therapeutic strategies. Herein, magnetic carboxymethyl cellulose-ε-polylysine hybrids (FCE) were synthesized via a facile one-pot coprecipitation method and further used as matrix to anchor silver nanoparticles (Ag NPs). The as-resulted Ag/FCE hybrids were employed to inactivate pathogenic bacteria and accelerate bacteria-infected wound healing with the assistance of H₂O₂. In vitro investigation revealed the combination of hydroxyl radical (·OH) originated from low concentration of H₂O₂ catalyzed by Ag/FCE and the antimicrobial activity of Ag NPs endowed effective antibacterial performance to the hybrids against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Investigation on antibacterial mechanism indicated antibacterial activity of the synergetic strategy was achieved by destroying bacterial cell integrity, arresting metabolic, producing intracellular ROS, and oxidizing GSH. Additionally, in vivo assay exhibited Ag/FCE possessed satisfactory biocompatibility and effectively accelerated S. aureus-infected wound healing with the presence of low concentration of H₂O₂. Altogether, the presented results supported the great potential application of the synergistic antibacterial strategy for the therapy of bacterial-infected wound healing.

Effects of fermentation with Lactobacillus fermentum 21828 on the nutritional characteristics and antioxidant activity of Lentinus edodes liquid

BACKGROUND

Few studies to date have evaluated the use of Lactobacillus and Bifidobacterium in edible fungus fermentation. To obtain a fermented Lentinus edodes liquid product with good taste and effects, a strain with good fermentation performance from nine strains tested was selected, and the physicochemical properties and antioxidant capacity of the resulting product were evaluated.

RESULTS

Lactobacillus fermentum 21828 exhibited adhesion, tolerance to low pH and bile salts, and good fermentation performance. The number of viable bacteria was 1.05 × 10⁸  CFU mL^-1 , and the extraction rate of crude polysaccharide from L. edodes was 2.79% after fermentation. The effects of fermentation on the contents and composition of nutrients in L. edodes liquid were marked, with changes in total soluble protein, total soluble sugar, total acid, and total phenol levels. The 2,2-diphenyl-1-picrylhydrazyl radical-scavenging rate in the fermentation liquid was 93.01%, which was significantly higher than that in non-fermented liquid (80.33%). Furthermore, analysis of volatile and 5'-nucleotide contents showed that fermentation altered the flavor of the product, whereas sensory evaluation showed that the fermented product was preferred.

CONCLUSION

Our study demonstrated that the fermented L. edodes liquid exhibited better nutritional and functional properties, as well as sensory characteristics, compared with unfermented liquid. © 2021 Society of Chemical Industry.

Highly galloylated and A-type prodelphinidins and procyanidins in persimmon (Diospyros kaki L.) peel

The structure of persimmon peel proanthocyanidins (PPPAs) was characterized. After acid catalysis of PPPAs in the presence of phloroglucinol, five reaction products such as (epi)gallocatechin-phloroglucinol ((E)GC-ph) etc. were identified by HPLC-DAD-ESI/MS. FT-IR analysis confirmed that all of the compounds exhibited a 2, 3-cis configuration. Therefore, the extension units in PPPAs were EGC, epigallocatechin gallate (EGCG), epicatechin, and epicatechin gallate and only EGCG was detected as the terminal unit. PPPAs contained 25.21% of procyanidins and 74.79% of prodelphindins and had a high degree of 3-O-galloylation (>74.79%). The mean degree of polymerization of PPPAs was calculated to be 10.18. MALDI-TOF MS analysis showed that A-type linkage and galloylation existed commonly in PPPAs.

Reduction the contamination of patulin during the brewing of apple cider and its characteristics

Patulin is one of the most significant food safety problems in fruit and derived products. The reduction of patulin contamination in food processing has always been the focus of research. In this study, nine yeast strains were applied for the brewing of apple cider and the fate of patulin was determined. In this process, the patulin contamination can be decreased by adsorption onto and degradation of yeast cells in the main fermentation (20.8-49.1%), as well as the adsorption removal during clarification (18.7-58%), inverted cans (21.3-31.4%) and aging (1.0-5.8%). Saccharomyces cerevisiae (1027) was selected to reveal the elimination mechanism of patulin in main fermentation. The decrease of patulin content was mainly due to degradation and the intracellular enzymes played a more important role than extracellular ones. In addition, the synthesis of enzymes was related to the induction of patulin. Furthermore, the degradation product of patulin in the main fermentation was identified as E-ascladiol, which is less toxic than patulin. Based on the representative strain of S. cerevisiae 1027, patulin contamination can be effectively eliminated during apple cider brewing. This study provides a new insight into eliminating patulin contamination in the brewing of apple cider.

The Safety of Cold-Chain Food in Post-COVID-19 Pandemic: Precaution and Quarantine

Since the outbreak of coronavirus disease-19 (COVID-19), cold-chain food contamination caused by the pathogenic severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has attracted huge concern. Cold-chain foods provide a congenial environment for SARS-CoV-2 survival, which presents a potential risk for public health. Strengthening the SARS-CoV-2 supervision of cold-chain foods has become the top priority in many countries. Methodologically, the potential safety risks and precaution measures of SARS-CoV-2 contamination on cold-chain food are analyzed. To ensure the safety of cold-chain foods, the advances in SARS-CoV-2 detection strategies are summarized based on technical principles and target biomarkers. In particular, the techniques suitable for SARS-CoV-2 detection in a cold-chain environment are discussed. Although many quarantine techniques are available, the field-based quarantine technique on cold-chain food with characteristics of real-time, sensitive, specific, portable, and large-scale application is urgently needed.

Lactobacillus kefiranofaciens JKSP109 and Saccharomyces cerevisiae JKSP39 isolated from Tibetan kefir grain co-alleviated AOM/DSS induced inflammation and colorectal carcinogenesis

This study aimed to investigate the alleviative effects of Lactobacillus kefiranofaciens JKSP109 (LK) and Saccharomyces cerevisiae JKSP39 (SC) isolated from Tibetan kefir grain on colon inflammation and colorectal carcinogenesis. Azoxymethane (AOM) and dextran sulfate sodium (DSS) were used to establish a mouse model of colorectal cancer (CRC). The treatment group mice were administered with LK, SC, or the combination of LK and SC for five days per week from the day of receiving AOM. The composition of the gut microbiota was assessed using internal transcribed spacer 2 and 16S rRNA gene high-throughput sequencing. Furthermore, the biomarkers associated with gut barrier integrity, inflammation, regulators of cell proliferation, and apoptosis were evaluated. The results showed that the administration of LK, SC, and their combination increased the body weights and decreased the disease activity index (DAI) score and tumor multiplicity. As compared to the CRC model group, the three treatment groups positively regulated the gut microbiota. Meanwhile, the three treatments also enhanced the gut barrier, decreased the expression of proinflammatory cytokines and oncocyte proliferation indicators, and increased the expression of terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive tumor epithelial cells and content of short chain fatty acids in fecal samples. All these results indicated that the LK and SC alleviated the inflammation and colorectal carcinogenesis in AOM/DSS-induced CRC mouse models, and the majority of tested indexes in the combination group were superior to single strain groups.

Demand-oriented construction of Mo3S13-LDH: A versatile scavenger for highly selective and efficient removal of toxic Ag(I), Hg(II), As(III), and Cr(VI) from water

Inspired by the classic ion-exchange reaction, a single phase material of Mg_0.66Al_0.34(OH)₂(Mo₃S₁₃)_0.03(NO₃)_0.14(CO₃)_0.07·H₂O (Mo₃S₁₃-LDH) was masterly constructed by intercalating Mo₃S₁₃^2- into the MgAl-LDH gallery. Prepared Mo₃S₁₃-LDH displays excellent binding affinity and high selectivity for Ag(I) and Hg(II) in a mixed solution, in which an apparent selectivity order of Hg(II) > Ag(I) ≫ Pb(II), Cu(II), Ni(II), Co(II), Cd(II), and Mn(II) is observed. Enormous capture capacities (q_m^Ag = 446.4 mg/g, q_m^Hg = 354.6 mg/g) and fast equilibration time (within 60 min) place Mo₃S₁₃-LDH in the upper ranks of materials for such removal. For oxoanions, As(III) (HAsO₃^2-) and Cr(VI) (CrO₄^2-) can be specifically trapped by Mo₃S₁₃-LDH with comparable loading ability (q_m^As = 61.8 mg/g, q_m^Cr = 90.6 mg/g) in the coexistence of multiple interfering anions. Notably, high Hg(II) and Cr(VI) concentrations are finally reduced below the safe limit of drinking water. The excellent capture capacity of Mo₃S₁₃-LDH benefits from the rational design by following two aspects: (i) the multiple sulfur ligands in Mo₃S₁₃^2- groups give place to various capture modes and different affinity orders for target ions, and (ii) large-sized Mo₃S₁₃^2- groups widen the interlayer spacing of LDH, thereby accelerating the mass transfer process. Furthermore, the satisfactory structural stability of Mo₃S₁₃-LDH is also reflected through the unchanged hexagonal prismatic shape after adsorption. All of these highlight the great potential of Mo₃S₁₃-LDH for the application in water remediation.