Swelling behavior of bisensitive interpenetrating polymer networks for microfluidic applications.

Bisensitive interpenetrating polymer network (IPN) hydrogels of temperature sensitive net-poly(N-isopropylacrylamide) and pH sensitive net-poly(acrylic acid-co-acrylamide) for microfluidic applications were prepared via a sequential synthesis using free radical polymerization. The IPN indicated a suitable reversible alteration of swelling in response to the change in pH and temperature. The adequate change of the hydrogel volume is a basic requirement for microfluidic applications. Using the introduced correction factor f, it is possible to determine the cooperative diffusion coefficient (Dcoop) of cylindrical samples at any aspect ratio. The determined cooperative diffusion coefficient allowed the evaluation of varying swelling processes of different network structures. The presence of the second sub-network of the IPN improved the swelling behaviour of the first sub-network compared to the individual networks.

pH-triggered aggregate shape of different generations lysine-dendronized maleimide copolymers with maltose shell.

Glycopolymers are promising materials in the field of biomedical applications and in the fabrication of supramolecular structures with specific functions. For tunable design of supramolecular structures, glycopolymer architectures with specific properties (e.g., controlled self-assembly) are needed. Using the concept of dendronized polymers, a series of H-bond active giant glycomacromolecules with maleimide backbone and lysine dendrons of different generations were synthesized. They possess different macromolecular size and functionality along the backbone. Their peripheral maltose units lead to solubility under physiological conditions and controlled aggregation behavior. The aggregation behavior was investigated depending on generation number, pH value, and concentration. A portfolio of complementary analytical tools give an insight into the influence of the different parameters in shaping a rod-, coil-, and worm-like molecular structure and their controlled aggregate formation. MD simulation helped us to understand the complex aggregation behavior of the linear polymer chain without dendritic units.

Adhesion and viability of two enterococcal strains on covalently grafted chitosan and chitosan/kappa-carrageenan multilayers.

Chitosans are natural aminopolysaccharides, whose low cytotoxicity suggests their potential use for nonadhesive, antibacterial coatings on biomaterials implant surfaces. Here, the antiadhesive behavior and ability to kill bacteria upon adhesion ("contact killing") of chitosan coatings were evaluated for two strains of Enterococcus faecalis, isolated from clogged biliary stents. Chitosan coatings covalently grafted or applied as chitosan/kappa-carrageenan multilayers were characterized by ellipsometry, scanning force microscopy (SFM), X-ray photoelectron spectroscopy (XPS), and electrokinetic measurements. Decreases in initial bacterial deposition rates and the number of bacteria adhering in a more advanced state of the adhesion process were observed on both types of modified surfaces, with more pronounced effects on highly hydrated multilayers. Adhesion of negatively charged enterococci was slightly enhanced on chitosan-terminated multilayers, but antibacterial effect was absent on kappa-carrageenan-terminated multilayers. Thus, the efficacy of multilayers remains an interesting interplay between the promoting effect of cationically charged groups on adhesion of negatively charged bacteria and, on the other hand, their antibacterial effects.