Influence of temperature fluctuations on growth and recrystallization of ice crystals in frozen peeled shrimp (Litopenaeus vannamei) pre-soaked with carrageenan oligosaccharide and xylooligosaccharide.

Temperature fluctuation is a common problem in the frozen storage of shrimp products. This study investigated the influence of carrageenan oligosaccharide (CO) and xylooligosaccharide (XO) on the growth and recrystallization of ice crystals in frozen peeled shrimp exposed to temperature fluctuations. Shrimp soaked with water and 3.0% (w/v) Na4P2O7 solution were designated as the negative and positive controls, respectively. Our data revealed that both CO- and XO-soaked shrimp had significant improvements in thawing and cooking loss, myofibrillar protein content, Ca2+-ATPase activity, and textural variables when exposed to temperature fluctuations compared to control samples. Microstructural imaging indicated that soaking the shrimp in CO and XO slowed the progression of damage caused to tissue myofibrils by large ice crystals, as well as inhibited the growth and recrystallization of ice crystals in muscle tissues. SDS-PAGE analysis confirmed that treatment with the oligosaccharides exhibited marked effects on the stability of muscle proteins and inhibited the degradation of muscle proteins affected by the temperature fluctuations. Based on these data, we hypothesize that the incorporated CO and XO may bind to muscle proteins and capture water molecules in the myofibrillar network through hydrogen bonding, thereby suppressing the myofibrillar denaturation and tissue structure destruction induced by the growth and recrystallization of ice crystals.

Mitochondrial activity as an indicator of fish freshness.

The current methods used to routinely assess freshness in the fishing industry reflect more a state of spoilage than a state of freshness. Mitochondria, the seat of cellular respiration, undergo profound changes in post mortem tissues. The objective of this study was to demonstrate that mitochondrial activity constitutes a putative early fish freshness marker. The structure of gilthead sea bream (Sparus aurata) muscle tissue was evaluated over time by transmission electron microscopy. Respiration was assessed in mitochondria isolated from sea bream fillets using oxygraphy. Membrane potential (ΔΨm) was determined by fluorescence (Rhodamine 123). Mitochondrial activity of fillets stored at +4 °C was studied for 6 days. Changes in mitochondrial cristae structure appeared from Day 3 highlighting the presence of dense granules. ΔΨm and mitochondrial activity were significantly disrupted in sea bream fillets after 96 h of storage at +4 °C. Mitochondrial activity constituted a reliable and early indicator of fish freshness.

Structural and biochemical properties of silver carp surimi as affected by comminution method.

Effects of two typical comminution methods (shearing and blending) on structural and biochemical properties of silver carp surimi were comparatively investigated. Surimi myofibrils in striated appearance were progressively disrupted within 15 min of blending. The myofibrils were completely disintegrated after shearing for 5 min. Surface hydrophobicity of surimi increased and then gradually decreased (p < 0.05) under shearing, while it continuously increased (p < 0.05) under blending. As shearing time was extended, α-helical structure decreased and ß-sheet structure increased simultaneously; surface active sulfhydryl content (SH) increased and then decreased (p < 0.05); and intensity of myosin heavy chain (MHC) was gradually reduced. However, secondary structure, MHC intensity and SH were slightly changed as blending time extended. Ca2+-ATPase activities increased and then declined (p < 0.05) with transition times at 1 min and 5 min under shearing and blending, respectively. Results indicated that shearing disrupted the ultrastructure and changed biochemical properties of surimi more pronouncedly than blending.

Polymeric blends of hydrocolloid from chia seeds/apple pectin with potential antioxidant for food packaging applications.

The aim of this study was to investigate the antioxidant, mechanical and physical properties of a new film-based polymeric blend of hydrocolloids obtained from the aqueous extraction of chia seeds (source antioxidants) and apple pectin. The individual matrices films were brittle and rigid with poor mechanical properties. The blends formulations contributed to improved mechanical properties regarding workability and resistance. The antioxidant results showed the potential hydrocolloid from chia seeds as natural source of antioxidant in these polymeric films. The formulation 3 (14(hydrocolloid):41(pectin):25(glycerol):20(glutaraldehyde) displayed well thermal, mechanical, morphological and antioxidant properties, suggesting their great potential for food packaging.

Electrochemical DNA biosensor for potential carcinogen detection in food sample.

The presence of carcinogens in food is a major food safety concern. A nanocomposite-based electrochemical DNA biosensor was constructed for potential carcinogen detection in food samples by immobilizing amine terminated single stranded DNA onto silica nanospheres deposited onto a screen-printed electrode modified using gold nanoparticles. The effect of three different DNA sequences: 15-base guanine, 24-base guanine and 24-base adenine-thymine rich DNA on carcinogen (formaldehyde and acrylamide) detection was evaluated. The competitive binding of the DNA with the carcinogen and electroactive indicator, Methylene blue (MB) was measured using differential pulse voltammetry. Optimization studies were conducted for MB concentration and accumulation time, DNA concentration, buffer concentration, pH and ionic strength. Overall, the 24-base guanine rich DNA yielded the best results with a detection limit of 0.0001 ppm, linear range between 0.0001 ppm and 0.1 ppm and reproducibility below 5% R.S.D. Finally, the results obtained using the biosensor were validated using Ames test.

Carbon disulfide-modified magnetic ion-imprinted chitosan-Fe(III): A novel adsorbent for simultaneous removal of tetracycline and cadmium.

A novel composite of carbon disulfide-modified magnetic ion-imprinted chitosan-Fe(III), i.e., MMIC-Fe(III) composite, was prepared as an efficient adsorbent for the simultaneous removal of tetracycline (TC) and Cd(II). This adsorbent showed excellent performance in removing TC and Cd(II) due to its rapid kinetics, high adsorption capacity, good reusability, and was well suited for use with real water samples. Kinetics studies demonstrated that the adsorption proceeded according to a pseudo-second order model. The adsorption isotherms were well described by the Langmuir model, with maximum adsorption capacity for TC and Cd(II) being 516.29 and 194.31mg/g, respectively. The synergistic effect of TC and Cd(II) adsorption might be due to the formation of TC-Cd(II) complex bridging the adsorbate and adsorbent. These properties demonstrate the potential application of MMIC-Fe(III) for the simultaneous removal of TC and Cd(II), and may provide some information for the synergistic removal of antibiotics and heavy metals from aquatic environments.

Superior antibacterial activity of nanoemulsion of Thymus daenensis essential oil against E. coli.

Natural preservatives are being extensively investigated for their potential industrial applications in foods and other products. In this work, an essential oil (Thymus daenensis) was formulated as a water-dispersible nanoemulsion (diameter=143nm) using high-intensity ultrasound. The antibacterial activity of the essential oil in both pure and nanoemulsion forms was measured against an important food-borne pathogen bacterium, Escherichia coli. Antibacterial activity was determined by measuring the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The antibacterial activity of the essential oil against E. coli was enhanced considerably when it was converted into a nanoemulsion, which was attributed to easier access of the essential oils to the bacterial cells. The mechanism of antibacterial activity was investigated by measuring potassium, protein, and nucleic acid leakage from the cells, and electron microscopy. Evaluation of the kinetics of microbial deactivation showed that the nanoemulsion killed all the bacteria in about 5min, whereas only a 1-log reduction was observed for pure essential oil. The nanoemulsion appeared to amplify the antibacterial activity of essential oils against E. coli by increasing their ability to disrupt cell membrane integrity.

Antioxidant films based on cross-linked methyl cellulose and native Chilean berry for food packaging applications.

Development of antioxidant and antimicrobial active food packaging materials based on biodegradable polymer and natural plant extracts has numerous advantages as reduction of synthetic additives into the food, reduction of plastic waste, and food protection against microorganisms and oxidation reactions. In this way, active films based on methylcellulose (MC) and maqui (Aristotelia chilensis) berry fruit extract, as a source of antioxidants agents, were studied. On the other hand, due to the high water affinity of MC, this polymer was firstly cross-linked with glutaraldehyde (GA) at different concentrations. The results showed that the addition of GA decreased water solubility, swelling, water vapor permeability of MC films, and the release of antioxidant substances from the active materials increased with the concentration of GA. Natural extract and active cross-linked films were characterized in order to obtain the optimal formulation with the highest antioxidant activity and the best physical properties for latter active food packaging application.

Development and evaluation of folate functionalized albumin nanoparticles for targeted delivery of gemcitabine.

Gemcitabine is one of the most potent anticancer agents acting on a wide range of solid tumors, however, its use is limited by short half life and high dose leading to serious side effects. The present investigation describes the development and characterization of folate functionalized gemcitabine loaded bovine serum albumin nanoparticles (Fa-Gem-BSANPs). The nanoparticles were prepared by desolvation cross-linking technique and characterized for various parameters including morphology, particle size, zeta potential, drug loading and release profile. The particle size of Gem-BSANPs and Fa-Gem-BSANPs was found to be 159.1±5.29 and 208.7±1.80 nm, respectively. DSC and XRD analysis indicated amorphous nature of the drug within the particles. The encapsulated gemcitabine exhibited less hemolytic properties as compared to native drug. The anticancer activity of Fa-Gem-BSANPs was evaluated in folate receptor over expressing cell lines (Ovcar-5 and MCF-7) and folate receptor deficient cell line (MIAPaCa-2). The Fa-Gem-BSANPs showed superior anticancer activity as compared to Gem-BSANPs in Ovcar-5 and MCF-7 cells while no significant difference in cytotoxicity was found with MIAPaCa-2 cells. Confocal microscopy indicated facilitated intracellular uptake of Fa-Gem-BSANPs in MCF-7, which in turn result in a higher potential for apoptosis. Further, Fa-Gem-BSANPs exhibited improved anti-tumor activity in Ehrlich solid tumor model in mice. In conclusion, our study indicates that folate functionalized nanoparticles confer enhance cellular uptake and cytotoxicity for gemcitabine.

SC-III3, a novel scopoletin derivative, induces autophagy of human hepatoma HepG2 cells through AMPK/mTOR signaling pathway by acting on mitochondria.

(E)-3-(4-chlorophenyl)-N-(7-hydroxy-6-methoxy-2-oxo-2H-chromen-3-yl) acrylamide (SC-III3), a newly synthesized derivative of scopoletin, was previously shown to reduce the viability of HepG2 cells and tumor growth of HepG2 xenograft mouse model. It induces the death of HepG2 cells by a way irrelevant to apoptosis and necrosis. To shed light on the cytotoxic mechanisms of SC-III3, the present study addresses whether and how it can induce autophagic cell death. When HepG2 cells were incubated with various concentrations of SC-III3, autophagic vacuoles could be observed by transmission electron microscopy and monodansylcadaverine staining. Increased expressions of LC3-II to LC3-I and Beclin-1, required for autophagosome formation, were accompanied. These characteristics integrally indicated that SC-III3 could initiate autophagy in HepG2 cells. N-acetyl-l-cysteine (NAC), a ROS scavenger, could reverse SC-III3-caused ROS accumulation, but it did not affect SC-III3-induced autophagy, suggesting that ROS was not involved in SC-III3-mediated autophagy in HepG2 cells. SC-III3 significantly depressed mitochondrial function, as evidenced by disruption of mitochondrial transmembrane potential and loss of the mitochondrial cristae structure, as well as decrease of Cox-I, Cox-III, Cox-IV, and ATP levels. The autophagy and activation of AMPK-TSC2-mTOR-p70s6k pathways induced by SC-III3 in HepG2 cells could be efficiently blocked by pre-treatments of compound C (an inhibitor of AMPK). Moreover, addition of extracellular ATP to the cell culture media could reverse SC-III3-caused activation of AMPK-TSC2-mTOR-p70s6k pathway, autophagy and cell viability decrease in HepG2 cells. Collectively, SC-III3 leads to autophagy through inducing mitochondrial dysfunction, depleting ATP, and activating AMPK-mTOR pathway, which thus reflects the cytotoxic effect of SC-III3 in HepG2 cells.

Self-healable hydrogel on tumor cell as drug delivery system for localized and effective therapy.

A self-healable chitosan(CS)/polyvinyl alcohol (PVA) hydrogel as an injectable drug carrier was first prepared in situ on tumor cells for effective and localized therapy. PVA molecules have a synergistic effect on the formation and maintenance of 3D network conformation of hydrogel. The hydrogel shows good biocompatibility and could be easily and rapidly formed. When loaded with fluorouracil (5-FU), the hydrogel possessed good drug retention ability at pH 7.4, which can prevent the loss of drug to normal cells and reduce the side effect. As well, the hydrogel shows continuous and controllable drug release, with the final cumulative releasing amount of 84.8% at pH 5.0. Therefore, the hydrogel not only could maintain a higher 5-FU concentration around tumor cells to enhance the antitumor effect, but also can achieve pH sensitive controllable drug release at the lesion site. Meantime, the attractive self-healing ability of the CS/PVA hydrogel is first revealed in this study, which contributes to the regeneration of its integral network from the broken fragments. The CS/PVA hydrogel may hold promise for better applications in anti-tumor therapy.

N-terminal 5-mer peptide analog P165 of amyloid precursor protein inhibits UVA-induced MMP-1 expression by suppressing the MAPK pathway in human dermal fibroblasts.

Exposure to ultraviolet (UV) radiation leads to a progressive increase in dermal damage through the degradation of collagen, which is mediated by matrix metalloproteinases (MMPs). UV radiation alters the intracellular signaling events that regulate the elaboration of MMPs. Our previous study showed that P165, the N-terminal 5-mer peptide analog of amyloid precursor protein, exerts a protective effect on ultraviolet A (UVA)-induced loss of collagen type I in human dermal fibroblasts (HDFs) by inhibiting the generation of intracellular reactive oxygen species and MMP-1. In this study, we focused on specific signal transduction pathways to elucidate the possible photoprotective mechanisms of P165 in controlling MMP-1 inhibition. Results from western blot analyses indicated that pretreatment with P165 dose-dependently inhibited UVA-induced phosphorylation of extracellular regulated protein kinases (ERK), c-Jun N-terminal kniase (JNK), p38 mitogen-activated protein kinases (MAPKs), and the phosphorylation of their downstream targets c-Jun and c-Fos. The photoprotective effects of P165 were further demonstrated in collagen type I secretion and cellular senescence induced by UVA irradiation. These findings suggest that P165 exerts photoprotective activity in UVA-treated HDFs by regulating MMP-1 generation. This activity may be mediated by inhibiting the MAPK signaling pathways. Thus, P165 is a potential agent for the prevention of skin photoaging.