Gelation studies of a cellulose-based biohydrogel: the influence of pH, temperature and sterilization.

International audienceThe present paper investigates the rheological properties of silated hydroxypropylmethylcellulose (Si-HPMC) biohydrogel used for biomaterials and tissue engineering applications. The general property of this modified cellulose ether is the occurrence of self-hardening due to silanol condensation subsequent to a decrease in pH (from 12.4 to nearly 7.4). The behavior of unsterilized and sterilized Si-HPMC solutions in diluted and concentrated domains is first described and compared. In addition, the influence of physiological parameters such as pH and temperature on the rate of the gelation process is studied. In dilute solution, the intrinsic viscosity ([eta]) of different pre-steam sterilization Si-HPMC solutions indicates that macromolecular chains occupy a larger hydrodynamic volume than the post-steam sterilization Si-HPMC solutions. Although the unsterilized Si-HPMC solutions demonstrate no detectable influence of pH upon the rheological behavior, a decrease in the limiting viscosities (eta(0)) of solutions with increasing pH is observed following steam sterilization. This effect can be explained by the formation of intra- and intermolecular associations during the sterilization stage originating from the temperature-induced phase separation. The formation of Si-HPMC hydrogels from injectable aqueous solution is studied after neutralization by different acid buffers leading to various final pHs. Gelation time (t(gel)) decreases when pH increases (t(gel) varies from 872 to 11s at pH 7.4 and 11.8, respectively). The same effect is observed by increasing the temperature from 20 to 45 degrees C. This is a consequence of the synergistic effect of the increased reaction rate and acid buffer diffusion. pH and temperature are important parameters in the gelation process and their influence is a key factor in controlling gelation time. By adapting the gel parameters one could propose hydrogels with cross-linking properties adapted to clinical applications by controlling the amount of pH of neutralization and temperature

Anomalous diffusion on fractal structure of magnetic membranes

The concept of diffusion on fractal structure of polymeric membrane with magnetic powder is presented. The fractal characteristics, i.e. static fractal dimension df and fractal dimension of the trajectory of the random walk dw, were evaluated for qualitative and quantitative description of membrane structures. The way of introducing the fractal dimension and anomalous-diffusion exponent into the generalized diffusion equation on fractal geometries obtained by Metzler et al. has been shown. The results showed that the random walk within the membranes of the smallest granulation of magnetic powder was of the most subdiffusive character

The effect of high-pressure on organocatalyzed ROP of γ-butyrolactone

In this paper, we report 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) supported high-pressure approach enforcing Ring-Opening Polymerization (ROP) of γ-butyrolactone (GBL), that due to unfavorable thermodynamics and low ring strain, is considered as a hardly polymerizable monomer. Application of Broadband Dielectric Spectroscopy (BDS) allowed us to find optimal thermodynamic conditions to perform well-controlled and notably fast polymerization (even within 1 h!), avoiding undesired crystallization process. It was shown that by varying pressure and temperature conditions, we could control molecular weight, dispersity of recovered macromolecules, as well as rate and efficiency of the reaction that are significantly altered with respect to the reference process carried out at ambient conditions. Experiments performed at respectively very low temperature T = 233 K and low/ moderate pressure (p = 75–250 MPa) and much higher temperatures (T = 248–268 K) and compressions (p = 1000 MPa) yielded poly(γ-butyrolactone) (PGBL) of tailored absolute molecular weight in moderate range Mn = 2.8–15.0 (up to 30.3) kg/mol and narrow/moderate dispersity ranging from Đ = 1.12–1.89. What is more, the implementation of MALDI-TOF, GPC and DSC analyses, clearly indicated that as i) the time of reaction gets longer, ii) the amount of catalyst increases, iii) the temperature lowers, the content of cyclic products in produced polymers grows. This phenomenon influences the rheological properties (viscosity), foil formation ability (films) and cell culture proliferation features of the recovered macromolecules. Presented results open a highly effective and repeatable route to produce PGBL via pressure-assisted ROP and indicate the possibility of tuning properties of this polymer by varying concentration of cycles or eventual block copolymerization with other biorelevant monomers to meet the expectations of the biotechnological industry

Recent Attempts in the Design of Efficient PVC Plasticizers with Reduced Migration

This paper reviews the current trends in replacing commonly used plasticizers in poly(vinyl chloride), PVC, formulations by new compounds with reduced migration, leading to the enhancement in mechanical properties and better plasticizing efficiency. Novel plasticizers have been divided into three groups depending on the replacement strategy, i.e., total replacement, partial replacement, and internal plasticizers. Chemical and physical properties of PVC formulations containing a wide range of plasticizers have been compared, allowing observance of the improvements in polymer performance in comparison to PVC plasticized with conventionally applied bis(2-ethylhexyl) phthalate, di-n-octyl phthalate, bis(2-ethylhexyl) terephthalate and di-n-octyl terephthalate. Among a variety of newly developed plasticizers, we have indicated those presenting excellent migration resistance and advantageous mechanical properties, as well as those derived from natural sources. A separate chapter has been dedicated to the description of a synergistic effect of a mixture of two plasticizers, primary and secondary, that benefits in migration suppression when secondary plasticizer is added to PVC blend

Collation Efficiency of Poly(Vinyl Alcohol) and Alginate Membranes with Iron-Based Magnetic Organic/Inorganic Fillers in Pervaporative Dehydration of Ethanol

Hybrid poly(vinyl alcohol) and alginate membranes were investigated in the process of ethanol dehydration by pervaporation. As a filler, three types of particles containing iron element, i.e., hematite, magnetite, and iron(III) acetyloacetonate were used. The parameters describing transport properties and effectiveness of investigated membranes were evaluated. Additionally, the physico-chemical properties of the resulting membranes were studied. The influence of polymer matrix, choice of iron particles and their content in terms of effectiveness of membranes in the process of ethanol dehydration were considered. The results showed that hybrid alginate membranes were characterized by a better separation factor, while poly(vinyl alcohol) membranes by a better flux. The best parameters were obtained for membranes filled with 7 wt% of iron(III) acetyloacetonate. The separation factor and pervaporative separation index were equal to 19.69 and 15,998 g⋅m−2⋅h−1 for alginate membrane and 11.75 and 14,878 g⋅m−2⋅h−1 for poly(vinyl alcohol) membrane, respectively

Evaluation of drug loading capacity and release characteristics of PEDOT/naproxen system: Effect of doping ions

Conducting polymers are versatile and robust materials that have recently become attractive as controlled drug delivery systems. Possessing ion exchangeable properties, they can serve as carriers for numerous biologically active species, showing particular applicability in neural tissue engineering and regional chemotherapy. In the pursuit of the design of the most effective controlled drug delivery system, we aimed to compare the performance of the conducting polymer-based matrix as a function of doping anion, using chloride, perchlorate and dodecyl sulfate, respectively, as the primary dopants. Due to their different ion radius and mobility, selected ions were found to provide substantial changes into polymer characteristics, having strong effects into the uptake and release of a model drug, naproxen sodium salt. PEDOT/ClO4 matrix, particularly, was found to possess superior properties providing highest mass of the formed polymer (103.45 +/- 10.09 mu g cm(-2)), charge storage capacity (44.9 mC cm(-2)) and ion exchange capacity (0.122 +/- 0.003 mu mol cm(-2)), leading also to the highest amounts of loaded (0.024 +/- 0.002 mu mol cm(-2)) and released (from 0.71 +/- 0.10 mu g cm(-2) to 1.61 +/- 0.59 mu g cm(-2)) drug. (C) 2018 Elsevier Ltd. All rights reserved.The authors are grateful to the National Science Centre in Poland for financing the research in the framework of Sonata (2016/23/D/ST5/01306). This publication has emanated from research conducted with the financial support of Science Foundation Ireland (SFI) and is co-funded under the European Regional Development Fund under Grant Number 13/RC/2073. This project has received funding from the European Union\u27s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 713690. The authors acknowledge the facilities and scientific and technical assistance of the Centre for Microscopy & Imaging at the National University of Ireland Galway, a facility that is funded by NUIG and the Irish Government\u27s Programme for Research in Third Level Institutions, Cycles 4 and 5, National Development Plan 2007–2013.2020-09-0

The investigations on process type influence on methyl violet adsorption on chitin and chitin deacetylation products

The aim of this work was to a study various adsorption processes of methyl violet (model compound of aniline dye) on chitin and chitin deacetylation products. Two types of adsorption processes - batch and continuous - were tested. Results illustrated that raw chitin is an effective adsorbent for methyl violet and the adsorption activity of chitin deacetylation products strongly decrease with increasing degree of deacetylation (DDA). The continuous process is more effective then batch process

Bio-Oil Derived from Teff Husk via Slow Pyrolysis Process in Fixed Bed Reactor and Its Characterization

Due to the depletion of fossil fuels and the destruction wrought by global warming caused by the combustion of fossil fuels, the search for renewable energy sources has become a major global concern. This study aimed to assess the bio-oil production from teff husk via slow pyrolysis process. The pyrolysis of teff husk took place in a batch reactor at a temperature between 400 °C and 500 °C with a 120 min retention time. At 450 °C, the pyrolysis process produced 32.96 wt.% of optimum bio-oil yield and had a HHV of 25.32 MJ/kg. TGA, FTIR, and SEM-EDX were used to analyze the produced bio-oil to investigate its thermal decomposition, functional groups, and surface morphology with its elemental composition, respectively. Alcohols, aromatic, phenols, alkanes, esters, and ethers were the primary compounds of the bio-oil produced by the slow pyrolysis of teff husk. The HHV of the biochar ranged from 21.22 to 22.85 MJ/kg. As a result, teff husk can be used to make biofuel; however, further bio-oil upgrading is needed for the produced teff husk bio-oil to be used effectively and commercially. Overall, the slow pyrolysis of teff husk offers a chance to produce biofuels with enhanced value that can be used for additional purposes