Petr Bělský

Nanostructure of hyaluronan acyl-derivatives in the solid state

Acyl derivatives of hyaluronan (acyl-HA) are promising materials for biomedical applications. Depending on the acyl length and the degree of substitution, these derivatives range from self-assembling water-soluble polymers to materials insoluble in aqueous environments. The behaviour of acyl-HA was studied in solution, but little attention was paid to the solid state, despite its importance for applications such as medical device fabrication. We thus used X-ray scattering and electron microscopy to explore the solid-state nano-structure of acyl-HA. The set of samples included various substituents, substitution degrees and molecular weights. The obtained data showed that all studied acyl-HA materials contained structures with dimensions on the order of nanometres that were not present in unmodified HA. The size of the nanostructures increased with the acyl length, while the degree of substitution and molecular weight had negligible effects. We suggest that the observed nanostructure corresponds to a distribution of hydrophobic domains in a hydrophilic matrix of unmodified HA segments.

Biomaterials and Nanotechnology Approach to Medical Enhancement

Over the past few decades, biomaterial science has emerged as a new field in which a regeneration or replacement of damaged tissue has become one of the main focuses. Also, great advances in the application of multifunctional nanoparticles for biomedical applications have been made. Implementation of nanomedicine in cellular, preclinical, and clinical studies has led to exciting advances ranging from fundamental to applied research. This chapter will examine the key aspects of application of traditional biomaterials, their physicochemical properties, and behavior in biological system. Moreover, the unique properties of nanomaterials are highlighted in relation to their vast nanostructural characteristics and the field of application. With 164 references.

Influence of polyfurfuryl alcohol (PFA) loading on the properties of Nafion composite membranes

ABSTRACT Composite membranes based on Nafion (N115) loaded with furfuryl alcohol (FA) were prepared by in situ acid-catalyzed polymerization technique, with the aim to improve the ionic conductivity of Nafion membranes. The functionalization, thermal stability, electrical properties and mechanical strength of N115-PFA composites was analyzed by means of Fourier transform infrared (FT-IR) attenuated total reflection (ATR) spectroscopy, small- and wide-angle X-ray scattering (SAXS/WAXS), thermogravimetric analysis (TGA), electrical impedance spectroscopy, dynamic vapor sorption (DVS) and dynamic mechanical analyser (DMA). The FA loading in the resultant composites had a positive correlation with the water uptake (Wu), water vapor uptake (Wvu), ionic conductivity and thermo-mechanical stability. At low polyfurfuryl alcohol (PFA) loading, these membranes displayed higher Wu and improved ionic and electrical properties. Further, the thermo-mechanical stability also gradually increased with the PFA loading. All the composites showed a well-defined glass transition temperature in DMA, which shifted to higher temperature with repeated PFA loading. Overall, the results indicate that the developed composite membrane are promising for low temperature polymer electrolyte membrane (PEM) fuel cells.