Imprinted contact lenses for sustained release of polymyxin B and related antimicrobial peptides

The aim of this work was to develop drug-soft contact lens combination products suitable for controlled release of antimicrobial peptides on the ocular surface. Incorporation of functional monomers and the application of molecular imprinting techniques were explored to endow 2-hydroxyethyl methacrylate (HEMA) hydrogels with the ability to load and to sustain the release of polymyxin B and vancomycin. Various HEMA–drug–functional monomer–cross–linker molar ratios were evaluated to prepare polymyxin B imprinted and non-imprinted hydrogels. Acrylic acid-functionalized and imprinted hydrogels loaded greater amounts of polymyxin B and led to more sustained release profiles, in comparison with non-functionalized and non-imprinted networks. Polymyxin B-loaded hydrogels showed good biocompatibility in hen’s egg test-chorioallantoic membrane tests. Functionalized hydrogels also loaded vancomycin and sustained its release, but the imprinting effect was only exhibited with polymyxin B, as demonstrated in rebinding tests. Microbiological assays carried out with Pseudomonas aeruginosa allowed identification of the most suitable hydrogel composition for efficient bacteria eradication; some hydrogels being able to stand several continued challenges against this important bacterial pathogen

Supercritical carbon dioxide and biomedicine: Opening the doors towards biocompatibility

Supercritical CO2 techniques are promising technologies for developing products that can be useful for biomedical engineering. However, the obtained products (aerogels, foams, membranes, fibers, liposomes, particles, impregnated polymers) with these processes are not widely used in hospitals or surgical procedures. This article assesses the current status of these techniques by reviewing the results obtained from different biological and mechanical preliminary tests on obtained products. This study finds that in vitro and in vivo tests of current formulations and materials are appropriate in terms of their biological response for future use. Still, there is a lack of knowledge concerning their behavior under real physiological conditions and some problems regarding their economic competitiveness versus conventional techniques. Mechanical studies are also needed for aerogels, foams and membranes and impregnated materials depending on the final application, since their use is limited by these properties. In this context, how these materials will behave in more realistic situations and if the biological response can be stimulated, as occurs under physiological conditions, have to be studied

Production of fungistatic porous structures of cellulose acetate loaded with quercetin, using supercritical CO2

In this work, supercritical phase inversion was used to produce membranes of cellulose acetate, loaded with a highly hydrophobic drug, quercetin, with antifungal properties. Changing process parameters, such as polymer concentration (5%, 10% and 15% w/w), pressure (100 and 200 bar) and temperature (45 and 50 °C), different membrane morphologies and pores size were obtained. Operating in this way, it was possible to control quercetin release: the existence of macrovoids (i.e., finger-like structure) promoted a faster drug release (about 200 min); whereas, cellular structures favored a prolonged drug release (up to 1400 min). These membranes were tested against two types of fungi (Kluyveromyces lactis and Yarrowia lipolitica), obtaining an efficient and prolonged antifungal effect, overcoming the problems of quercetin hydrophobicity

Supercritical CO2 assisted formation of composite membranes containing an amphiphilic fructose-based polymer

With the aim of increasing the mechanical and biological properties of different materials, a supercritical CO2 (SC-CO2) assisted technique was used to include a polymer with a natural origin (levan) in membranes of cellulose acetate (CA) and polyvinylidenefluoride-co-hexafluoropropylene (PVDF-HFP). CA-levan membranes were characterized by interconnected pores ranging from 9 to 13μm; due to levan addition, composite membranes increased their mechanical resistance and cells adhesion (from 8% to 30%). In the second system, the processing of a PVDF-HFP-DMSO-levan colloidal suspension system caused a morphological modification and the generation of a foam-like structure; a decrease of the mechanical resistance and an increase of cells adhesion (from 8% to 35%) were observed. Stress-strain responses for both systems were fitted using two different hyperelastic equations, Yeoh and Ogden; deviations from experimental data lower than 15% were obtained. In conclusion, SC-CO2 assisted process was able to generate composite structures with levan, accessible to the cells; i.e., transforming polymers like CA and PVDF-HFP in potentially useful materials for biological applications