Pectin modified with phenolic acids: Evaluation of their emulsification properties, antioxidation activities, and antibacterial activities

Three phenolic acids including p-hydroxybenzoic acid (PHBA), 3,4-dihydroxybenzoic acid, (DHBA), and gallic acid (GA) were grafted onto native pectin (Na-Pe) through enzymatic method. Ultraviolet-visible spectrometry, Fourier transform infrared spectroscopy, and ¹H NMR analyses were used to explore the reaction mechanism. Results indicated that the p-hydroxyl of the phenolic acids reacted with the methoxycarbonyl of pectin through transesterification, and a covalent connection was formed. The phenolic acid contents of PHBA modified pectin (Ph-Pe), DHBA modified pectin (Dh-Pe), and GA modified pectin (Ga-Pe) were 20.18%, 18.87%, and 20.32%, respectively. After acylation with phenolic acids, the 1,1-diphenyl-2-picryl hydrazine clearance of pectin changed from 7.68% (Na-Pe) to 6.88% (Ph-Pe), 40.80% (Dh-Pe), and 90.30% (Ga-Pe), whereas its inhibition ratio of pectin increased from 3.11% (Na-Pe) to 35.02% (Ph-Pe), 66.36% (Dh-Pe), and 77.89% (Ga-Pe). Moreover, compared with Na-Pe, modified pectins exhibited better emulsification properties and stronger antibacterial activities against both Escherichia coli and Staphylococcus aureus.

Occurrence, Genotyping, and Antibiotic Susceptibility of Cronobacter spp. in Drinking Water and Food Samples from Northeast China

Cronobacter species (formerly Enterobacter sakazakii) are emerging opportunistic bacterial pathogens that can infect both infants and adults. This study was conducted to isolate and genotype diverse Cronobacter species from drinking water, chilled fresh pork, powdered infant formula, instant noodles, cookies, fruits, vegetables, and dishes in Northeast China and to evaluate the antibiotic resistance and susceptibility of the isolates. Thirty-four Cronobacter strains were isolated and identified: 21 C. sakazakii isolates (61.8%), 10 C. malonaticus isolates (29.4%), 2 C. dublinensis isolates (5.9%), and 1 C. turicensis isolate (2.9%). These isolates were further divided into 15 sequence types (STs) by multilocus sequence typing. C. sakazakii ST4 (10 isolates, 29.4%), ST1 (3 isolates, 8.8%), and ST8 (3 isolates, 8.8%) and C. malonaticus ST7 (four isolates, 11.8%) were dominant. Antibiotic susceptibility testing indicated that all 34 Cronobacter isolates were susceptible to ampicillin-sulbactam, cefotaxime, ciprofloxacin, gentamicin, meropenem, tetracycline, piperacillin-tazobactam, and trimethoprim-sulfamethoxazole, 88.2% were susceptible to chloramphenicol, and 67.6% were resistant to cephalothin. The results of this study enhance knowledge about genotyping and antibiotic resistance of these Cronobacter species and could be used to prevent potential hazards caused by these strains in drinking water and various food products.

Action mode of cranberry anthocyanin on physiological and morphological properties of Staphylococcus aureus and its application in cooked meat

This study researched the action mode of cranberry anthocyanin (CA) against Staphylococcus aureus and the effect of CA on the counts of S. aureus and the quantity of cooked meat during storage. The antibacterial effect was assessed by minimum inhibitory concentration (MIC) and survival populations of S. aureus strains after CA treatments. The changes in intracellular adenosine 5'-triphosphate (ATP) concentration, cell membrane potential, content of bacterial protein and cell morphology were analyzed to reveal possible action mode. Application potentials of CA as antimicrobial agent were assessed during storage of cooked pork and beef. The result showed that the MIC of CA against S. aureus strains was 5 mg/mL. Approximately 8 log CFU/mL of S. aureus strains can be completely inhibited after treatment with 2.0 MIC of CA for 0.5 h. Treatments of CA resulted in lower intracellular ATP and soluble protein levels, damaged membrane structure and leakage of cytoplasmic. Application of CA on cooked pork and beef caused a significant decrease in S. aureus counts and pH values, and color-darkening compared with control samples. These findings demonstrated that CA played an effective antimicrobial against S. aureus and had a potential as natural preservative to inhibit the growth of food pathogens.

Hemodynamics and ventricular function in a zebrafish model of injury and repair

Myocardial infarction results in scar tissue and irreversible loss of ventricular function. Unlike humans, zebrafish has the capacity to remove scar tissue after injury. To assess ventricular function during repair, we synchronized microelectrocardiogram (μECG) signals with a high-frequency ultrasound pulsed-wave (PW) Doppler to interrogate cardiac hemodynamics. μECG signals allowed for identification of PW Doppler signals for passive (early [E]-wave velocity) and active ventricular filling (atrial [A]-wave velocity) during diastole. The A wave (9.0±1.2 cm·s(-1)) is greater than the E wave (1.1±0.4 cm·s(-1)), resulting in an E/A ratio <1 (0.12±0.05, n=6). In response to cryocauterization to the ventricular epicardium, the E-wave velocity increased, accompanied by a rise in the E/A ratio at 3 days postcryocauterization (dpc) (0.55±0.13, n=6, p<0.001 vs. sham). The E waves normalize toward the baseline, along with a reduction in the E/A ratio at 35 dpc (0.36±0.06, n=6, p<0.001 vs. sham) and 65 dpc (0.2±0.16, n=6, p<0.001 vs. sham). In zebrafish, E/A<1 at baseline is observed, suggesting the distinct two-chamber system in which the pressure gradient across the atrioventricular valve is higher compared with the ventriculobulbar valve. The initial rise and subsequent normalization of E/A ratios support recovery in the ventricular diastolic function.

Preparation of acylated chitosan with caffeic acid in non-enzymatic and enzymatic systems: Characterization and application in pork preservation

To further improve the performance of chitosan in food processing and preservation, this study investigated the grafting of the caffeic acid onto the chitosan in non-enzymatic and enzymatic systems. Result suggested that the caffeic acid was successfully incorporated into the chitosan in the non-enzymatic system, and the grafting ratio of modified chitosan (CA@CTS-N) was 7.49%. Moreover, lipase had a significant positive effect on the grafting reaction of the chitosan, and the modified chitosan prepared in enzymatic system (CA@CTS-E) obtained a higher grafting ratio, which was 11.82%. In both systems, the carboxyl of the caffeic acid was bonded to the amino of the chitosan and formed carbonyl ammonia. After the introduction of foreign group, many changes occurred in the functional properties of the modified chitosan. First, the water solubility of the chitosan was significantly improved from 0.00285 (native chitosan, CTS) to 0.221 (CA@CTS-N) and 0.774 g/100 mL (CA@CTS-E). The caffeoyl had a significant impact on the emulsifying properties of the chitosan. Compared with those of CTS, the modified chitosan had stronger antioxidation and antibacterial activities against Escherichia coli, Staphylococcus aureus, and Candida albicans. Finally, the pork treated with the modified chitosan exhibited longer shelf life than that treated with CTS.

Antibiotic and Desiccation Resistance of Cronobacter sakazakii and C. malonaticus Isolates from Powdered Infant Formula and Processing Environments

This study evaluated the antimicrobial and desiccation resistance of Cronobacter sakazakii and Cronobacter malonaticus isolates from powdered infant formula and processing environments. The antimicrobial susceptibility tests showed that the 70 Cronobacter strains, representing 19 sequence types, were susceptible to the most of the antibiotics except for amoxicillin-clavulanate, ampicillin, and cefazolin. Furthermore, the growth of six C. sakazakii and two C. malonaticus strains from different sequence types (STs) in hyperosmotic media was measured. The growth of the two C. sakazakii strains (CE1 and CE13) from the neonatal pathovars ST4 and ST8, were significantly higher (p < 0.05) than that of other strains. C. malonaticus strain CM35 (ST201) was the slowest grower in all strains, and most could not grow in more than 8% NaCl solution. Also the survival of these strains under desiccation conditions was followed for 1 year. The viable count of Cronobacter spp. under desiccation conditions was reduced on average by 3.02 log cycles during 1 year, with CE13 (ST8) being the most desiccation resistant strain. These results will improve our understanding of the persistence of the two closely related species C. sakazakii and C. malonaticus which are of concern for neonatal and adult health.

Single-frame deep-learning super-resolution microscopy for intracellular dynamics imaging

Single-molecule localization microscopy (SMLM) can be used to resolve subcellular structures and achieve a tenfold improvement in spatial resolution compared to that obtained by conventional fluorescence microscopy. However, the separation of single-molecule fluorescence events that requires thousands of frames dramatically increases the image acquisition time and phototoxicity, impeding the observation of instantaneous intracellular dynamics. Here we develop a deep-learning based single-frame super-resolution microscopy (SFSRM) method which utilizes a subpixel edge map and a multicomponent optimization strategy to guide the neural network to reconstruct a super-resolution image from a single frame of a diffraction-limited image. Under a tolerable signal density and an affordable signal-to-noise ratio, SFSRM enables high-fidelity live-cell imaging with spatiotemporal resolutions of 30 nm and 10 ms, allowing for prolonged monitoring of subcellular dynamics such as interplays between mitochondria and endoplasmic reticulum, the vesicle transport along microtubules, and the endosome fusion and fission. Moreover, its adaptability to different microscopes and spectra makes it a useful tool for various imaging systems.

Hydrophobic Interface Starch Nanofibrous Film for Food Packaging: From Bioinspired Design to Self-Cleaning Action

Starch-derived edible food films have great potential as biodegradable food packaging materials because they reduce the overuse of traditional petroleum-based plastic. Herein, we demonstrate a direct method of mass producing a pure starch food packaging film that consisted of starch nanofibers by using a temperature-assisted electrospinning technique without addition of any nonstarch components. To overcome the major issue of ultralow hydrophobicity of starch nanofibrous film (SNF), we used a facile and low-cost solution immersion approach to create a fiber coating of stearic acid (STA) inspired by biological organisms with superhydrophobic properties, such as lotus leaves. Hierarchical flower-like micronanostructures were obtained on SNF by controlled assembly of STA onto the surface of starch nanofibers. Benefiting from the effective formation of STA self-assembled lamella, the multiscale microstructure surface features, low surface energy, and enhancing thermal stability of SNF were obtained and confirmed to result in the variety of its hydrophobicity, which can be also tailored by simple controlling of the solution concentration of STA. Importantly, the STA-self-assembled coated SNF enabled water to roll freely in all directions, which is a crucial factor for self-cleaning. Our novel strategy based on self-assembly can guide development of bioinspired hydrophobic interfaces for starch-based films for edible hydrophobic materials.

Integrating light-sheet imaging with virtual reality to recapitulate developmental cardiac mechanics

Currently, there is a limited ability to interactively study developmental cardiac mechanics and physiology. We therefore combined light-sheet fluorescence microscopy (LSFM) with virtual reality (VR) to provide a hybrid platform for 3D architecture and time-dependent cardiac contractile function characterization. By taking advantage of the rapid acquisition, high axial resolution, low phototoxicity, and high fidelity in 3D and 4D (3D spatial + 1D time or spectra), this VR-LSFM hybrid methodology enables interactive visualization and quantification otherwise not available by conventional methods, such as routine optical microscopes. We hereby demonstrate multiscale applicability of VR-LSFM to (a) interrogate skin fibroblasts interacting with a hyaluronic acid-based hydrogel, (b) navigate through the endocardial trabecular network during zebrafish development, and (c) localize gene therapy-mediated potassium channel expression in adult murine hearts. We further combined our batch intensity normalized segmentation algorithm with deformable image registration to interface a VR environment with imaging computation for the analysis of cardiac contraction. Thus, the VR-LSFM hybrid platform demonstrates an efficient and robust framework for creating a user-directed microenvironment in which we uncovered developmental cardiac mechanics and physiology with high spatiotemporal resolution.

Minutes-timescale 3D isotropic imaging of entire organs at subcellular resolution by content-aware compressed-sensing light-sheet microscopy

Rapid 3D imaging of entire organs and organisms at cellular resolution is a recurring challenge in life science. Here we report on a computational light-sheet microscopy able to achieve minute-timescale high-resolution mapping of entire macro-scale organs. Through combining a dual-side confocally-scanned Bessel light-sheet illumination which provides thinner-and-wider optical sectioning of deep tissues, with a content-aware compressed sensing (CACS) computation pipeline which further improves the contrast and resolution based on a single acquisition, our approach yields 3D images with high, isotropic spatial resolution and rapid acquisition over two-order-of-magnitude faster than conventional 3D microscopy implementations. We demonstrate the imaging of whole brain (~400 mm3), entire gastrocnemius and tibialis muscles (~200 mm3) of mouse at ultra-high throughput of 5~10 min per sample and post-improved subcellular resolution of ~ 1.5 μm (0.5-μm iso-voxel size). Various system-level cellular analyses, such as mapping cell populations at different brain sub-regions, tracing long-distance projection neurons over the entire brain, and calculating neuromuscular junction occupancy across whole muscle, are also readily accomplished by our method.

Regulation of gene expression of various phase I and phase II drug-metabolizing enzymes by tamoxifen in rat liver

The objective of the present investigation was to evaluate the effect of tamoxifen (TAM) on the gene expression of different phase I and phase II drug-metabolizing enzymes. Groups of male and female F344/NCr rats were administered either corn oil or TAM (2.8 to 45 mg/kg body wt x 14 days) dissolved in corn oil by gavage. An additional group of rats received a diet supplemented with phenobarbital (PB, 500 ppm). Northern blot analyses of total liver RNA were conducted using [32P]-labeled cDNA or oligonucleotide probes coding for different sulfotransferase (ST); UDP-glucuronosyltransferase (UGT), glutathione S-transferase (GST), epoxide hydrolase (EPH) or cytochrome P450 (CYP) mRNA transcripts. In male rats, TAM increased the levels of STel, STa and STpl mRNAs, whereas PB increased only the STel mRNA. In female rats, there was no expression of STel and STHA mRNA in either control or TAM-treated animals. TAM and PB increased UGTBe/p mRNAs in all rats, whereas UGTml mRNA was elevated only in PB-treated animals. EPH mRNA was elevated markedly in all rats treated with TAM and PB, whereas GSTya/ye mRNA was highly increased by PB, but only marginally increased by TAM. Finally, TAM increased CYP3A1 mRNA, and slightly increased CYP2B1 mRNA, whereas PB highly elevated mRNAs for both of these CYP genes. In conclusion, treatments of rats with TAM increased the mRNA levels of many phase I and phase II drug-metabolizing enzymes, and this pleiotypic response to TAM seems to be different from other prototype inducers such as PB or dioxin (TCDD).

Stearic acid esterified pectin: Preparation, characterization, and application in edible hydrophobic pectin/chitosan composite films

This work investigated the modification of low-methoxy pectin with stearic anhydride through microwave action with 4-dimethylaminopyridine as catalyst. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses indicated that stearic acid was grafted on the pectin through esterification reaction, with the maximum stearic acid grafting ratio (SGR) of 10.7% for the modified pectin. The introduction of stearic acid was shown to significantly improve the emulsifying activity and stability of pectin. Composite films were prepared by blending the modified pectins and chitosan, and compared with the contact angle of 65.3° for the film with native low-methoxy pectin (PC0), the films with modified pectins showed a significant angle increase, with the highest contact angle reaching 101.9°, indicating a hydrophobic surface. Moreover, an appropriate amount of aliphatic chains could improve the tensile strength and elongation at break of the composite films due to the "anchoring effect".

High dynamic range optical projection tomography (HDR-OPT)

Traditional optical projection tomography (OPT) acquires a single image at each rotation angle, thereby suffering from limitations in CCD dynamic range; this conventional usage cannot resolve features in samples with highly heterogeneous absorption, such as in small animals with organs of varying size. We present a novel technique, applying multiple-exposure high dynamic range (HDR) imaging to OPT, and demonstrate its ability to resolve fine details in zebrafish embryos, without complicated chemical clearing. We implement the tomographic reconstruction algorithm on the GPU, yielding a performance increase of two orders of magnitude. These features give our method potential application in high-throughput, high-resolution in vivo 3D imaging.

Mechanical-electrical triggers and sensors using piezoelectric micowires/nanowires

We demonstrate a mechanical-electrical trigger using a ZnO piezoelectric fine-wire (PFW) (microwire, nanowire). Once subjected to mechanical impact, a bent PFW creates a voltage drop across its width, with the tensile and compressive surfaces showing positive and negative voltages, respectively. The voltage and current created by the piezoelectric effect could trigger an external electronic system, thus, the impact force/pressure can be detected. The response time of the trigger/sensor is approximately 10 ms. The piezoelectric potential across the PFW has a lifetime of approximately 100 s, which is long enough for effectively "gating" the transport current along the wire; thus a piezoelectric field effect transistor is possible based on the piezotronic effect.

Compact plane illumination plugin device to enable light sheet fluorescence imaging of multi-cellular organisms on an inverted wide-field microscope

We developed a compact plane illumination plugin (PIP) device which enabled plane illumination and light sheet fluorescence imaging on a conventional inverted microscope. The PIP device allowed the integration of microscope with tunable laser sheet profile, fast image acquisition, and 3-D scanning. The device is both compact, measuring approximately 15 by 5 by 5 cm, and cost-effective, since we employed consumer electronics and an inexpensive device molding method. We demonstrated that PIP provided significant contrast and resolution enhancement to conventional microscopy through imaging different multi-cellular fluorescent structures, including 3-D branched cells in vitro and live zebrafish embryos. Imaging with the integration of PIP greatly reduced out-of-focus contamination and generated sharper contrast in acquired 2-D plane images when compared with the stand-alone inverted microscope. As a result, the dynamic fluid domain of the beating zebrafish heart was clearly segmented and the functional monitoring of the heart was achieved. Furthermore, the enhanced axial resolution established by thin plane illumination of PIP enabled the 3-D reconstruction of the branched cellular structures, which leads to the improvement on the functionality of the wide field microscopy.

Advanced microscopy to elucidate cardiovascular injury and regeneration: 4D light-sheet imaging

The advent of 4-dimensional (4D) light-sheet fluorescence microscopy (LSFM) has provided an entry point for rapid image acquisition to uncover real-time cardiovascular structure and function with high axial resolution and minimal photo-bleaching/-toxicity. We hereby review the fundamental principles of our LSFM system to investigate cardiovascular morphogenesis and regeneration after injury. LSFM enables us to reveal the micro-circulation of blood cells in the zebrafish embryo and assess cardiac ventricular remodeling in response to chemotherapy-induced injury using an automated segmentation approach. Next, we review two distinct mechanisms underlying zebrafish vascular regeneration following tail amputation. We elucidate the role of endothelial Notch signaling to restore vascular regeneration after exposure to the redox active ultrafine particles (UFP) in air pollutants. By manipulating the blood viscosity and subsequently, endothelial wall shear stress, we demonstrate the mechanism whereby hemodynamic shear forces impart both mechanical and metabolic effects to modulate vascular regeneration. Overall, the implementation of 4D LSFM allows for the elucidation of mechanisms governing cardiovascular injury and regeneration with high spatiotemporal resolution.

Fast, 3D Isotropic Imaging of Whole Mouse Brain Using Multiangle-Resolved Subvoxel SPIM

The recent integration of light-sheet microscopy and tissue-clearing has facilitated an important alternative to conventional histological imaging approaches. However, the in toto cellular mapping of neural circuits throughout an intact mouse brain remains highly challenging, requiring complicated mechanical stitching, and suffering from anisotropic resolution insufficient for high-quality reconstruction in 3D. Here, the use of a multiangle-resolved subvoxel selective plane illumination microscope (Mars-SPIM) is proposed to achieve high-throughput imaging of whole mouse brain at isotropic cellular resolution. This light-sheet imaging technique can computationally improve the spatial resolution over six times under a large field of view, eliminating the use of slow tile stitching. Furthermore, it can recover complete structural information of the sample from images subject to thick-tissue scattering/attenuation. With Mars-SPIM, a digital atlas of a cleared whole mouse brain (≈7 mm × 9.5 mm × 5 mm) can readily be obtained with an isotropic resolution of ≈2 µm (1 µm voxel) and a short acquisition time of 30 min. It provides an efficient way to implement system-level cellular analysis, such as the mapping of different neuron populations and tracing of long-distance neural projections over the entire brain. Mars-SPIM is thus well suited for high-throughput cell-profiling phenotyping of brain and other mammalian organs.

Molecular cloning of three sulfotransferase cDNAs from mouse liver

Sulfate conjugation plays an important role in the biotransformation of not only xenobiotics but also many endogenous substances. Sulfotransferases, the enzymes that are responsible for this process, exist as a superfamily of genes. It has long been recognized that significant species differences exist among drug and carcinogen metabolizing enzymes such as cytochrome P450. Species differences in both regulation and catalytic activities of sulfotransferases may also exist. To investigate this, we conducted cDNA cloning and cDNA expression studies of sulfotransferase in the mouse. Three sulfotransferase cDNA clones were isolated from a female B6CBA mouse liver. Two of the clones, mSTa1 and mSTa2, were highly homologous to each other. Alignment of mSTa1 and mSTa2 cDNAs' nucleotide sequences with those of other sulfotransferase cDNAs revealed the greatest sequence identity with the rat STsmp cDNA. This analysis suggests that mSTa1, mSTa2 and rSTsmp cDNAs are derived from orthologous genes belonging to the alcohol/hydroxysteroid sulfotransferase gene family. The third clone, mSTp1 showed high identity to rSTp, hSTp1, hSTp3, and rSTp1C1, suggesting that mSTp1 belongs to the phenol family.

Investigation of a Lipase-Catalyzed Reaction between Pectin and Salicylic Acid and Its Isomers and Evaluation of the Emulsifying Properties, Antioxidant Activities, and Antibacterial Activities of the Corresponding Products

This study presents a method for modifying pectin with phenolic acids catalyzed by lipase in a two-phase system of water/tetrahydrofuran. Salicylic acid (SA) and its isomers, including m-hydroxybenzoic acid (MHBA) and p-hydroxybenzoic acid (PHBA), were grafted onto pectin, and the products were characterized via UV-vis, Fourier transform infrared spectroscopy (FTIR), and ¹H NMR analyses to explore the reaction process and mechanism between pectin and the three phenolic acids. Results indicated that lipase played a dual role in the reaction, namely, catalyzing the hydrolysis of the methyl group in the aqueous phase and esterifying the carboxyl group of pectin with the phenolic hydroxyl group of the phenolic acids in tetrahydrofuran. The grafting ratio of SA-modified pectin, MHBA-modified pectin, and PHBA-modified pectin was 1.89, 10.58, and 20.32%, respectively, and it was affected by the position of phenolic hydroxyl. Moreover, the effects of phenolic acids on the emulsifying properties, antioxidant activities, and antibacterial activities of the native and modified pectins were evaluated. In several aspects, the emulsifying properties of the modified pectins were better than those of native pectin. Moreover, the grafting of phenolic acids only slightly affected the 1,1-diphenyl-2-picryl hydrazine (DPPH) clearance of the modified pectins but substantially improved their inhibition ratio in a β-carotene bleaching assay. Furthermore, the modified pectins exhibited better bacteriostatic activity against both Escherichia coli and Staphylococcus aureus than native pectin.