Colorimetric Aerogel Gas Sensor with High Sensitivity and Stability.

The detection of formic acid vapor in the usage environment is extremely important for human health and safety. The utilization of metal-organic frameworks (MOFs) for the detection of gaseous molecules is an attractive strategy. However, the rational design and construction of MOF-based gas sensors with high sensitivity and mechanical stability remain a significant challenge. In this study, a simple approach is reported to fabricate colorimetric aerogel sensors assembled from MOF particles via ice template-assisted methods. As the aerogel sensor with staggered lamellae structures significantly provides a high air-volume intake of flowing gas, it generates a sufficient probability of contact reactions for highly mobile target molecules. Additionally, it enhances the mechanical stability by providing stress resistance between the staggered lamellae structures. Compared to conventional film sensors for the detection of formic acid molecules, aerogel sensors exhibit an 8-fold lower limit of detection, 15-fold better sensitivity at low concentrations, 34-fold faster response time, and higher stability. This approach shows great potential for rapid and real-time detection of target molecules as well as superior performance in the structural construction of various gas-sensitive materials.

Hydrogen-bonded organic framework-stabilized charge transfer cocrystals for NIR-II photothermal cancer therapy.

Charge-transfer (CT) cocrystals consisting of an electron donor and acceptor have gained attention for designing photothermal (PT) conversion materials with potential for biomedical and therapeutic use. However, the applicability of CT cocrystals is limited by their low stability and aqueous dispersity in biological settings. In this study, we present the self-assembly of CT cocrystals within hydrogen-bonded organic frameworks (HOFs), which not only allows for the dispersion and stabilization of cocrystals in aqueous solution but also promotes the CT interaction within the confined space of HOFs for photothermal conversion. We demonstrate that the CT interaction-driven self-assembly of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) with PFC-1 HOFs results in the formation of cocrystal-encapsulated TQC@PFC-1 while retaining the crystalline structure of the cocrystal and PFC-1. TQC@PFC-1, in particular, exhibits significant absorption in the second near-infrared region (NIR-II) and excellent photothermal conversion efficiency, as high as 32%. Cellular delivery studies show that TQC@PFC-1 can be internalized in different types of cancer cells, leading to an effective NIR-II photothermal therapy effect both in cultured cells and in vivo. We anticipate that the strategy of self-assembly and stabilization of CT cocrystals in nanoscale HOFs opens the path for tuning their photophysical properties and interfacing cocrystals with biological settings for photothermal therapeutic applications.

A novel ESKAPE-sensitive peptide with enhanced stability and its application in controlling multiple bacterial contaminations in chilled fresh pork.

The co-existence of various pathogenic bacteria on the surface of pork products exacerbates difficulties in food safety control. Developing broad-spectrum and stable antibacterial agents that are not antibiotics is an unmet need. To address this issue, all l-arginine residues of a reported peptide (IIRR)4-NH2 (zp80) were substituted with the corresponding D enantiomers. This novel peptide (IIrr)4-NH2 (zp80r) was expected to maintain favourable bioactivity against ESKAPE strains and have enhanced proteolytic stability compared with zp80. In a series of experiments, zp80r maintained favourable bioactivities against starvation-induced persisters. Electron microscopy and fluorescent dye assays were used to verify the antibacterial mechanism of zp80r. Importantly, zp80r reduced bacterial colonies in chilled fresh pork contaminated with multiple bacterial species. This newly designed peptide is a potential antibacterial candidate to combat problematic foodborne pathogens during storage of pork.

Metschnikowia citriensis FL01 antagonize Geotrichum citri-aurantii in citrus fruit through key action of iron depletion.

Metschnikowia citriensis FL01 has great potential for biocontrol applications for its excellent biocontrol efficacy on postharvest diseases of citrus fruit, and the iron depletion by pulcherriminic acid (PA) and then formation of insoluble pigment pulcherrimin had been speculated as an important action mechanism. To identify the genes involved in pulcherrimin synthesis and reutilization in M. citriensis FL01, we de novo assembled the genome of M. citriensis FL01 based on long-read PacBio sequencing. The final assembled genome consisted of 12 contigs with a genome size of 25.74 Mb, G + C content of 49.16% and 9310 protein-coding genes. The genome-wide BLAST of the PUL genes of M. pulcherrima APC 1.2 showed that the four PUL genes were clustered and located on Contig 4 of M. citriensis FL01. In order to further clarify the role of pulcherrimin pigment on biocontrol of M. citriensis FL01, CRISPR/cas9 technology was used to knock out PUL2 gene that was responsible for PA synthesis and the pigmentless mutants with stable phenotype were obtained. The mutant strains of M. citriensis FL01 lost the ability to produce pulcherrimin pigment, and simultaneously lost the ability to inhibit the growth of Geotrichum citri-aurantii in vitro. Moreover, the biocontrol efficacy of pigmentless mutant strains against sour rot was about 80% lower than that of wild-type M. citriensis FL01. These results directly proved that the iron depletion was an important mechanism of M. citriensis FL01.

Investigation of antibiofilm activity, antibacterial activity, and mechanistic studies of an amphiphilic peptide against Acinetobacter baumannii.

Biofilm-producing pathogens, such as Acinetobacter baumannii, have aroused escalating attention. Because these bacteria could secrete mixture with close-knit architecture and complicated components to resist traditional antibiotics. Here, we reported an amphiphilic peptide denoted as zp3 (GIIAGIIIKIKK-NH2), which showed favorable bioactivity against Acinetobacter baumannii ATCC 19606 (minimal inhibitory concentration, MIC = 4 µM) and low cytotoxicity to mammalian cells Vero (half maximal inhibitory concentration, IC50 > 100 µM). Importantly, zp3 could inhibit the formation of biofilm at micromole level and eliminate around 50% preformed biofilm at 32 µM after 6 h treatment. This peptide was able to bind with biofilm while maintaining a helical structure in a mimic biofilm-rich environment. In vivo test demonstrated that zp3 rescued 33.3% of larvae after 48 h infection and reduced 1 log live bacteria inside the animal body after 6 h treatment. The bactericidal mode for zp3 was attributed to the combination of influencing ions balance at low concentration and inducing permeability alteration and pore formation on the Acinetobacter baumannii membrane at high concentration. Application on medical textiles also proved that zp3 could perform a good antibacterial activity in practice.

Pichia galeiformis Induces Resistance in Postharvest Citrus by Activating the Phenylpropanoid Biosynthesis Pathway.

This study aimed to investigate the effect of Pichia galeiformis on disease resistance and elucidate the changes in phenylpropane biosynthesis treated by P. galeiformis in postharvest citrus. The results showed that P. galeiformis reduced the disease incidence and lesion diameters without direct contact with the pathogen Penicillium digitatum. Transcriptome analysis revealed that phenylpropanoid biosynthesis was triggered by P. galeiformis. Genes encoding phenylpropanoid biosynthesis were upregulated, including phenylalanine ammonia-lyase (PAL), 4-coumaroyl-CoA ligase (4CL), cinnamate-4-hydroxylase (C4H), peroxidase (POD), cinnamyl alcohol dehydrogenase (CAD), O-methyltransferase, and hydroxyl cinnamoyl transferase. Moreover, P. galeiformis increased the activity of PAL, 4CL, C4H, POD, polyphenol oxidase, and CAD in citrus pericarp. In addition, P. galeiformis treated citrus displayed higher levels of total phenolic compounds, flavonoid, and lignin and higher amounts of ferulic and sinapic acid. In conclusion, these results suggested that P. galeiformis could induce resistance through modulating the pathway of phenylpropanoid biosynthesis in postharvest citrus.

A rhodamine-deoxylactam based fluorescent probe for fast and selective detection of nitric oxide in living cells.

Nitric oxide (NO) plays vital roles in many physiological process and is closely related to many diseases. So far, a number of fluorescent probes have been constructed for the detection of NO successfully. However, the probes still suffer from long-time reaction and limited selectivity. Herein, a fluorescent probe named dRB-OPD is synthesized and used to recognize NO. The probe contains a deoxy-rhodamine B as fluorophore and o-phenylenediamino as reaction site. dRB-OPD shows fast response to NO within 40 s with 170-fold fluorescence enhancement. Moreover, the probe shows high selectivity towards NO over dehydroascorbic acid (DHA), ascorbic acid (AA), and methylglyoxal (MGO). Particularly, the probe can avoid the serious interference from cysteine (Cys) found in the rhodamine lactam-based fluorescent NO probes (RB-OPD). In addition, the probe is applied for the detection of exogenous and endogenous NO in the HepG2 and RAW 264.7 cells with satisfactory results.

A near-infrared fluorescent probe based on BODIPY derivative with high quantum yield for selective detection of exogenous and endogenous cysteine in biological samples.

Cysteine (Cys) is involved in cellular growth and Cys deficiency is related with many diseases. So far, a number of fluorescent probes have been constructed for the detection of Cys successfully. However, the probes are difficult to discriminate Cys from Hcy and the emission wavelength of the probes is in ultraviolet or visible range. Herein, a NIR fluorescent probe named NIR-BODIPY-Ac is synthesized and used to detect Cys. The emission wavelength of the probe is at 708 nm that belongs to near-infrared (NIR) region by attaching indolium to BODIPY core, which is suitable for bioimaging in vivo. Moreover, the probe exhibits high fluorescence quantum yield (Φ = 0.51) after the addition of Cys and high sensitivity toward Cys with 81-fold fluorescence enhancement. The linear range of the probe for Cys covers from 0.2 to 30 µM with a detection limit of 0.05 µM. Furthermore, the probe shows high selectivity towards Cys owing to the fact that there is more fast reaction rate between the probe and Cys than that of Hcy. In particular, the NIR fluorescent probe is applied for the detection of exogenous and endogenous Cys in biological samples such as cell, tissue and mouse with satisfactory results.