The thermal degradation of chitosan at different heating rates B in nitrogen was studied by thermogravimetric analysis. The results indicate that the thermal degradation of chitosan in nitrogen is a one-step reaction. The degradation temperatures increase with B. Experimentally, the initial degradation temperature (T 0 ) is (1.049B þ 326.8)8C; the temperature at the maximum degradation rate, that is, the peak temperature on a differential thermogravimetry curve (T p ), is (1.291B þ 355.2)8C; and the final degradation temperature (T f ) is (1.505B þ 369.7)8C. The degradation rates at T p and T f are not affected by B, and their average values are 50.17% and 72.16%, respectively, the maximum thermal degradation reaction rate, that is, the peak height on a differential thermogravimetry curve (R p ), increases with B. The relationship between B and R p is R p ¼ (1.20B þ 2.44)% min À1. The thermal degradation kinetic parameters are calculated with the Ozawa-Flynn-Wall method. The reaction activation energy (E) and frequency factor (A) change with an increasing degree of decomposition, and the variable trends of the two kinetic parameters are similar. The values of E and A increase remarkably during the initial stage of the reaction, then keep relatively steady, and finally reach a peak during the last stage. The velocity constants of the thermal degradation vary with the degree of decomposition and increase with the reaction temperature.

Nowadays, there is a growing interest to develop biodegradable functional composite materials for food packaging and biomedicine applications from renewable sources. Some composite films were prepared by the casting method using chitosan (CS) and agarose (AG) in different mass ratios. The composite films were analyzed for physical-chemical-mechanical properties including tensile strength (TS), elongation-at-break (EB), water vapor transmission rate (WVTR), swelling ratio, Fourier-transform infrared spectroscopy, and morphology observations. The antibacterial properties of the composite films were also evaluated. The obtained results reveal that an addition of AG in varied proportions to a CS solution leads to an enhancement of the composite film’s tensile strength, elongation-at-break, and water vapor transmission rate. The composite film with an agarose mass concentration of 60% was of the highest water uptake capacity. These improvements can be explained by the chemical structures of the new composite films, which contain hydrogen bonding interactions between the chitosan and agarose as shown by Fourier-transform infrared spectroscopy (FTIR) analysis and the micro-pore structures as observed with optical microscopes and scanning electron microscopy (SEM). The antibacterial results demonstrated that the films with agarose mass concentrations ranging from 0% to 60% possessed antibacterial properties. These results indicate that these composite films, especially the composite film with an agarose mass concentration of 60%, exhibit excellent potential to be used in food packaging and biomedical materials.

The thermal degradation of chitosan and chitosan-cupric ion compounds in nitrogen was studied by thermogravimetry analysis and differential thermal analysis (DTA) in the temperature range 30-6008C. The effect of cupric ion on the thermal degradation behaviors of chitosan was discussed. Fourier transform-infrared (FTIR) and X-ray diffractogram (XRD) analysis were utilized to determine the micro-structure of chitosan-cupric ion compounds. The results show that FTIR absorbance bands of À ÀNÀ ÀH, À ÀCÀ ÀNÀ À, À ÀCÀ ÀOÀ ÀCÀ À etc. groups of chitosan are shifted, and XRD peaks of chitosan located at 11.3, 17.8, and 22.88 are gradually absent with increasing weight fraction of cupric ion mixed in chitosan, which show that there are coordinating bonds between chitosan and cupric ion. The results of thermal analysis indicate that the thermal degradation of chitosan and chitosancupric ion compounds in nitrogen is a two-stage reaction.The first stage is the deacetylation of the main chain and the cleavage of glycosidic linkages of chitosan, and the second stage is the thermal destruction of pyranose ring of chitosan and the decomposition of residual carbon, in which both are exothermic. The effect of cupric ion on the thermal degradation of chitosan is significant. In the thermal degradation of chitosan-cupric ion compounds, the temperature of initial weight loss (T st ), the temperature of maximal weight loss rate (T max ), that is, the peak temperature on the DTG curve, and the peak temperature (T p ) on the DTA curve decrease, and the reaction activation energy (E a ) varies with increasing weight fraction of cupric ion.

BackgroundIn recent years, copper complexes have gradually become the focus of potential anticancer drugs due to their available redox properties and low toxicity. In this study, a novel mitochondrion-targeting copper (II) complex, [Cu (ttpy-tpp)Br2] Br (simplified as CTB), is first synthesized by our group. CTB with tri-phenyl-phosphine (TPP), a targeting and lipophilic group, can cross the cytoplasmic and mitochondrial membranes of tumor cells. The present study aims to investigate how CTB affects mitochondrial functions and exerts its anti-tumor activity in hepatoma cells.MethodsMultiple molecular experiments including Flow cytometry, Western blot, Immunofluorescence, Tracker staining, Transmission Electron Microscopy and Molecular docking simulation were used to elucidate the underlying mechanisms. Human hepatoma cells were subcutaneously injected into right armpit of male nude mice for evaluating the effects of CTB in vivo.ResultsCTB induced apoptosis via collapse of mitochondrial membrane potential (MMP), ROS production, Bax mitochondrial aggregation as well as cytochrome c release, indicating that CTB-induced apoptosis was associated with mitochondrial pathway in human hepatoma cells. Mechanistic study revealed that ROS-related mitochondrial translocation of p53 was involved in CTB-mediated apoptosis. Simultaneously, elevated mitochondrial Drp1 levels were also observed, and interruption of Drp1 activation played critical role in p53-dependent apoptosis. CTB also strongly suppressed the growth of liver cancer xenografts in vivo.ConclusionIn human hepatoma cells, CTB primarily induces mitochondrial dysfunction and promotes accumulation of ROS, leading to activation of Drp1. These stimulation signals accelerate mitochondrial accumulation of p53 and lead to the eventual apoptosis. Our research shows that CTB merits further evaluation as a chemotherapeutic agent for the treatment of Hepatocellular carcinoma (HCC).

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Hyperuricemia is typically defined as occurring above the saturation point of monosodium urate monohydrate (MSUM), which occurs at serum urate levels >6.8 mg dL−1.

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