Application of supercritical carbon dioxide in the preparation of biodegradable polylactide membranes

Non-Resorbable Nanocomposite Membranes for Guided Bone Regeneration Based On Polysulfone-Quartz Fiber Grafted with Nano-TiO2

The polymer-inorganic nanoparticles composite membranes are the latest solutions for multiple physicochemical resistance and selectivity requirements of membrane processes. This paper presents the production of polysulfone-silica microfiber grafted with titanium dioxide nanoparticles (PSf-SiO₂-TiO₂) composite membranes. Silica microfiber of length 150-200 μm and diameter 12-15 μm were grafted with titanium dioxide nanoparticles, which aggregated as microspheres of 1-3 μm, applying the sol-gel method. The SiO₂ microfibers grafted with nano-TiO₂ were used to prepare 12% polysulfone-based nanocomposite membranes in N-methyl pyrrolidone through the inversion phase method by evaporation. The obtained nanocomposite membranes, PSf-SiO₂-TiO₂, have flux characteristics, retention, mechanical characteristics, and chemical oxidation resistance superior to both the polysulfone integral polymer membranes and the PSf-SiO₂ composite membranes. The antimicrobial tests highlighted the inhibitory effect of the PSf-SiO₂-TiO₂ composite membranes on five Gram (-) microorganisms and did not allow the proliferation of Candida albicans strain, proving that they are suitable for usage in the oral environment. The designed membrane met the required characteristics for application as a functional barrier in guided bone regeneration.

Development of PMMA membranes functionalized with hydroxypropyl-beta-cyclodextrins for controlled drug delivery using a supercritical CO(2)-assisted technology

Cyclodextrin-containing polymers have proved themselves to be useful for controlled release. Herein we describe the preparation of membranes of poly(methylmethacrylate) (PMMA) containing hydroxypropyl-beta-cyclodextrins (HP-beta-CDs) using a supercritical CO(2)-assisted phase inversion method, for potential application as drug delivery devices. Results are reported on the membrane preparation, physical properties, and drug elution profile of a model drug. The polymeric membranes were obtained with HP-beta-CD contents ranging from 0 to 33.4 wt%, by changing the composition of the casting solution, and were further impregnated with ibuprofen using supercritical carbon dioxide (scCO(2)) in batch mode. The influence of the membrane functionalization in the controlled release of ibuprofen was studied by performing in vitro experiments in buffer solution pH at 7.4. The release of the anti-inflammatory drug could be tuned by varying the cyclodextrin content on the membranes.

Supercritical gel drying: a powerful tool for tailoring symmetric porous PVDF-HFP membranes

In this work, poly(vinylidene fluoride) copolymer with hexafluoropropylene (PVDF-HFP) membrane-like aerogels have been generated for the first time. PVDF-HFP gels have been prepared from polymer-acetone solutions by adding various amounts of ethanol. A series of supercritical drying experiments have been performed at different pressures (from 100 to 200 bar) and temperatures (from 35 to 45 degrees C) and at various polymer concentrations (from 5 to 12 wt %). The effects of the process conditions on the membrane morphology have been evaluated, and structure-property relationships have been found. In all cases, the membranes exhibit interconnected structures with nanosized pores and high porosity, leading to reduced resistance to the gas mass transfer and high hydrophobic character of the surfaces. These membrane-like aerogels promise to form a new class of highly hydrophobic porous interfaces, potentially suitable to be used in membrane operations based, for example, on the contactor technology.