Physicochemical properties of biopolymer-based polyelectrolyte complexes with controlled pH/thermo-responsiveness

Conformational Changes of Poly(Maleic Anhydride-alt-styrene) Modified with Amino Acids in an Aqueous Medium and Their Effect on Cytocompatibility and Hemolytic Response

The conformational changes of poly(maleic anhydride-alt-styrene) (PSMA) modified with different amino acids (PSMA-Aa) were studied in an aqueous medium as a function of ionic strength and pH. The specific viscosity of PSMA-Aa decreased with increasing salt concentration due to a more compact conformation. There was a decrease in surface tension with increasing concentrations of the modified polyelectrolyte having a greater effect for the PSMA modified with l-phenylalanine at pH 7.0, demonstrating a greater surface-active character. The conformational changes were also confirmed by molecular dynamics studies, indicating that PSMA-Aa exhibits a compact structure at pH 4.0 and a more extended structure at pH 7.0. On the other hand, the conformational changes of PSMA-Aa were related to its biological response, where the higher surface-active character of the PSMA modified with l-phenylalanine correlates very well with the higher hemolytic activity observed in red blood cells, in which the surface-active capacity supports lytic potency in erythrocytes. The cytocompatibility assays indicated that there were no significant cytotoxic effects of the PSMA-Aa. Additionally, in solvent-accessible surface area studies, it was shown that the carboxylate groups of the PSMA modified with l-phenylalanine are more exposed to the solvent at pH 7.0 and high salt concentrations, which correlates with lower fluorescence intensity, reflecting a loss of mitochondrial membrane potential. It is concluded that the study of the conformational changes in PE modified with amino acids is essential for their use as biomaterials and relevant to understanding the possible effects of PE modified with amino acids in biological systems.

Smart and green interfaces: from single bubbles/drops to industrial environmental and biomedical applications

Interfaces can be called Smart and Green (S&G) when tailored such that the required technologies can be implemented with high efficiency, adaptability and selectivity. At the same time they also have to be eco-friendly, i.e. products must be biodegradable, reusable or simply more durable. Bubble and drop interfaces are in many of these smart technologies the fundamental entities and help develop smart products of the everyday life. Significant improvements of these processes and products can be achieved by implementing and manipulating specific properties of these interfaces in a simple and smart way, in order to accomplish specific tasks. The severe environmental issues require in addition attributing eco-friendly features to these interfaces, by incorporating innovative, or, sometimes, recycle materials and conceiving new production processes which minimize the use of natural resources and energy. Such concept can be extended to include important societal challenges related to support a sustainable development and a healthy population. The achievement of such ambitious targets requires the technology research to be supported by a robust development of theoretical and experimental tools, needed to understand in more details the behavior of complex interfaces. A wide but not exhaustive review of recent work concerned with green and smart interfaces is presented, addressing different scientific and technological fields. The presented approaches reveal a huge potential in relation to various technological fields, such as nanotechnologies, biotechnologies, medical diagnostics, and new or improved materials.