Controlled Release Study on Bifidocin A from a Polyvinyl Alcohol/Chitosan Blend Particle-Based Biodegradable and Active Packaging Coupled with Mechanistic Assessment and Experimental Modeling.

On the basis of PVA-CS, which is incorporated with Bifidocin A, anti-microbial biodegradable films were prepared, characterized by their abilities to control the Bifidocin A's total release rate into foods as needed for packaging of active foods. This study aimed to explore the anti-microbial effects and release kinetics of active substances in polyvinyl alcoholchitosan (PVA-CS) particle composite films added with Bifidocin A. Pseudomonas fluorescens was used as indicator bacteria to evaluate the anti-microbial activity of the films. Fick's law, power law and negative exponential growth model were applied to further study the release kinetics of Bifidocin A. The results revealed that the composite films of PVA and CS had better mechanical properties and anti-microbial activity when the content of Bifidocin A was 50% with 1:1 PVA/CS, but it impairs the structure of the film, which can be resolved by including a suitable amount of grycerol. The anti-microbial was released faster at higher temperature and concentration of Bifidocin A, and the diffusion coeffcients increased significantlywith the increase of temperature and concentration. According to the thermodynamic parameters, the release of Bifidocin A was endothermic and spontaneous. High correlation factors (R² > 0.99) were acquired by fitting the release data of the Bifidocin A with the negative exponential growth model. The potential of Bifidocin A to deliver from the films into the food analog appropriately at low temperatures favored the obtained active films to be applied on food packaging, especially suitable for refrigerated foods.

Cisplatin and oxaliplatin inhibit gap junctional communication by direct action and by reduction of connexin expression, thereby counteracting cytotoxic efficacy.

Cisplatin [cis-diamminedichloroplatinum(II)]/oxaliplatin [1,2-diamminocyclohexane(trans-1)oxolatoplatinum(II)] toxicity is enhanced by functional gap junctions between treated cells, implying that inhibition of gap junctions may decrease cytotoxic activity of these platinum-based agents. This study investigates the effect of gap junction modulation by cisplatin/oxaliplatin on cytotoxicity in a transformed cell line. The effects were explored using junctional channels expressed in transfected HeLa cells and purified hemichannels. Junctional channels showed a rapid, dose-dependent decrease in dye coupling with exposure to cisplatin/oxaliplatin. With longer exposure, both compounds also decreased connexin expression. Both compounds inhibit the activity of purified connexin hemichannels, over the same concentration range that they inhibit junctional dye permeability, demonstrating that inhibition occurs by direct interaction of the drugs with connexin protein. Cisplatin/oxaliplatin reduced the clonogenic survival of HeLa cells at low density and high density in a dose-dependent manner, but to a greater degree at high density, consistent with a positive effect of gap junctional intercellular communication (GJIC) on cytotoxicity. Reduction of GJIC by genetic or pharmacological means decreased cisplatin/oxaliplatin toxicity. At low cisplatin/oxaliplatin concentrations, where effects on connexin channels are minimal, the toxicity increased with increased cell density. However, higher concentrations strongly inhibited GJIC, and this counteracted the enhancing effect of greater cell density on toxicity. The present results indicate that inhibition of GJIC by cisplatin/oxaliplatin decreases their cytotoxicity. Direct inhibition of GJIC and reduction of connexin expression by cisplatin/oxaliplatin may thereby compromise the effectiveness of these compounds and be a factor in the development of resistance to this class of chemotherapeutic agents.

Effects of 17ß-Estradiol combined with cyclical compressive stress on the proliferation and differentiation of mandibular condylar chondrocytes.

OBJECTIVE: The aim of this study is to investigate the effects of 17ß-Estradiol (E2) at different concentrations combined with cyclical compressive stress on the proliferation and differentiation of mandibular condylar chondrocytes (MCCs). DESIGN: MCCs, isolated from female Sprague-Dawley rats, were exposed to E2 at different concentration, cyclical compressive stress or the combination, effects of which on MCCs proliferation and differentiation were detected. RESULTS: E2 at physiological concentration (10-9 mol/L) has lower proliferative effects on MCCs, compared with non-physiological concentration (10-12 mol/L or 10-6 mol/L). For MCCs differentiation, effects of E2 at different concentration are totally opposite: E2 at 10-9 mol/L promotes MCCs differentiation, but at 10-12 mol/L or 10-6 mol/L, it inhibits MCCs differentiation. When combined with E2 at 10-9 mol/L, cyclical compressive stress shows synergistic effect on proliferation and differentiation. However, when combined with E2 at 10-12 mol/L or 10-6 mol/L cyclical compressive stress reverses the inhibition in MCCs differentiation provoked by E2 at 10-12 mol/L or 10-6 mol/L. CONCLUSION: Effects of E2 combined with cyclical compressive stress on MCCs proliferation and differentiation are different, which suggests that orthodontist should take fully consideration of the levels of E2 and adopt comprehensive strategies, so as to achieve better orthodontic effect.

Entrapment of proteins and peptides in chitosan-polyphosphoric acid hydrogel beads: A new approach to achieve both high entrapment efficiency and controlled in vitro release.

Bovine serum albumin (BSA), whey protein isolate (WPI), insulin and a casein hydrolysate were entrapped in chitosan-polyphosphoric acid (PPA) beads. The in vitro release of protein from the beads in simulated gastric fluid (SGF, pH 3) and simulated intestinal fluid (SIF, pH 7) was evaluated. High entrapment efficiencies were achieved for intact proteins (>95% in all cases) but entrapment was lower for the casein hydrolysate (circa 50%), possibly indicating a physical or steric entrapment of the proteins in these chitosan-PPA beads. Inhibited release of BSA, in both SGF and SIF, was achieved with low PPA concentration. Insulin and WPI were effectively retained in SGF and gradually released in SIF. Peptides from casein hydrolysate were partially (circa 35%) but quickly released in SGF with no further release in SIF. Overall, these results indicate that chitosan-PPA beads show potential for lower gastrointestinal delivery of bioactive protein material.

Entrapment of protein in chitosan-tripolyphosphate beads and its release in an in vitro digestive model.

This research sought to evaluate the entrapment and in vitro release behaviour of bovine serum albumin (BSA) in chitosan-tripolyphosphate (TPP) hydrogel beads. Beads were manufactured by extruding gel forming solutions containing varying concentrations of chitosan (1-2.5%w/w) and BSA (0.25-10%w/w) into TPP solutions ranging in concentration from 0.1 to 10%w/w and in ionic strength from 0.16 to 0.67M at pH values of 4, 5 and 9.4. Beads produced at a low TPP concentration of 0.4% w/w had the highest BSA entrapment efficiency (71.6±0.7%) and inhibited BSA release in simulated gastric fluid (SGF) to a greater extent. Increasing chitosan concentration resulted in a higher protein entrapment efficiency, but lowered the overall release. Increasing TPP concentration or the BSA concentration loaded, led to early release in SGF. The results indicate that the utilization of lower concentrations of TPP is a good approach to improve the protein retention ability of chitosan-TPP beads in a simulated gastric environment.

Study of a membrane bioreactor with glass fiber flat grille modules and the modules' optimization based on the local critical flux theory.

A novel flat grille membrane module using inorganic glass fibers as filter media is proposed for use in a membrane bioreactor for wastewater treatment. A model which integrates the concepts of back transport velocity, spatial local critical flux and temporal variation of the local flux has been developed. The membrane module was optimized based on experimental results and calculations using the model. The optimized parameters include the volume ratio of membrane solution for the surface modification of glass fibers, the fiber inner diameter and fiber length. The optimal values were 1:2 and 5mm respectively but the length had little effect on the performance of the module. The critical time was then calculated with the model and an equation developed. The result was in very good agreement with the observed one. Finally, the performance of the glass fiber MBR was monitored. The effluent quality and stability of the system were comparable to that of conventional MBRs. This MBR will be a promising technique for wastewater treatment given its low cost, high strength and good effluent quality.

[Dynamic membrane bioreactor with glass fiber tube covered with organic membrane].

A novel grille form complex membrane module composed of glass fiber covered with organic membrane and the dynamic membrane bioreactor (DMBR) with this complex membrane were studied. The results showed that the flux of the dynamic membrane of glass fiber tube without covering with organic membrane solution was only 4 L/(m2 x h) at a trans-membrane pressure (TMP) of 0.02 MPa. After the modification of covering with the organic membrane solution, the complex dynamic membrane flux could reach to a level of 16 L/(m2 x h) at a TMP of 0.01 MPa in operation, and after a hydraulic and chemical cleaning, the membrane flux was up to 17.1 L/(m2 x h) at a lower TMP of 0.003 MPa. When the glass fiber tube was coated with a membrane solution with a concentration of 1:4 (membrane materials/solution in volume ratio), the flux of the complex membrane worked steadily at 14.29 L/(m2 x h) more than 51 days, and according to calculation by TMP rising, the flux could maintain for almost 275 d. The average removal rates of COD and NH4+ -N were 81.96% and 83.66% respectively by the DMBR, and that were 21.01% and 3.61% only by the complex dynamic membrane. Moreover, the cost of complex membrane was approximately 40-60 yuan/m2, which was lower than the traditional organic membrane.

[Study of a new type of tubular self-forming dynamic membrane bioreactor and its application for treatment of landfill leachate].

A new type of fiberglass tubular self-forming dynamic membrane bioreactor (DMBR) and its application for treatment of landfill leachate on laboratory scale were studied. The results showed that the system worked with a average membrane flux 3.75 L/m2 x h) maintained by gravity filtration at a trans-membrane pressure (TMP) of 2 900 Pa for near 80 days. After the modification of membrane module, a higher membrane flux was achieved at a TMP of 1 450 Pa and the membrane flux could be maintained steadily at 6 L/(m2 x h) for a long time. At the same time, the formation and filtration performance of dynamic membrane (DM) was tested. The effluent turbidity was blow 1.0 NTU and the average removal of COD, BOD5 and NH4(+) -N in this system exceeded 71%, 96% and 98% respectively. Moreover, COD removal from the supernatant on an average of 19.34% was made only by the dynamic membrane.