Open Access

Introduction: produced by renewable resources, biodegradable polymers with their competitive mechanical properties, thermal stability and biocompatibility are important alternatives to other synthetic materials for use in medical devices, i.e. endotracheal suction catheters. However, infected catheters may lead to nosocomial infections, such as lower respiratory tract infections, with mechanical ventilation being a major risk for these. Antimicrobially coated endotracheal suction catheters may be one measure to reduce this risk. Methods: two procedures using ethanol and sodium hydroxide were tested to immobilize poly(hexamethylene biguanide) (PHMB) to polylactide-ε-caprolactone (PLA-ε-CL). The cytocompatibility of the coating was verified via the MTT assay and cytokine analysis in a cell monolayer and in a 3D mucosa model. The antimicrobial efficacy was tested using S. epidermidis; after this bacterial contamination and the adherence and viability of cells were tested. Chemical surface analysis has been performed with pristine and PHMB-coated specimens by means of infrared spectroscopy (ATR-FTIR). Results: with both applied coating procedures, PHMB could be immobilized onto the PLA-ε-CL surface. The biocompatibility of PLA-ε-CL was not impaired by the PHMB coating. IL-1α was slightly but significantly increased. Reduction of S. epidermidis was about 4 lg-levels after 6 h of incubation. Contamination of the surface prior to cell culture did not impair the adherence of the cells. Conclusion: we demonstrated that PLA-ε-CL coated with PHMB has good biocompatible properties with antimicrobial activity thus revealing the polymer to be a suitable material for the development of medical devices that are able to prevent bacterial contaminations and infections.

The water dynamics in a nanocomposite film that consists of the electrically conductive poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and cellulose nanofibrils (CNFs) have been investigated during three cycles of exposure to low and high relative humidity (RH = 5% and 85%, respectively) using quasi-elastic neutron scattering (QENS). The obtained dynamical structure factors are transformed into the imaginary part of the dynamic susceptibility to better differentiate between the individual relaxation processes. In a humid environment, two different water species are present inside the films: fast-moving bulk water and slow-moving hydration water. During the first cycle, a large amount of hydration water enhances the polymer chain mobility, eventually leading to irreversible structural rearrangements within the film. In the subsequent cycles, we observed a release of all bulk water and portions of hydration water upon drying, along with an uptake of both water species in a humid environment. The relaxation times of hydration water diffusion as a function of momentum transfer can be described by a jump-diffusion model. The obtained jump lengths, residence times, and diffusion coefficients of hydration water suggest a change in the hydration layer upon drying: water molecules around hydrophobic groups are released from the film, while the hydrogen bonds between water and hydrophilic groups are sufficiently strong to keep these molecules inside the films, even in a dry state. The QENS results can be correlated to the structural and conductive properties. In the dry state, the low hydration water content and the absence of bulk water allow for improved wetting of the CNFs by PEDOT:PSS, which eventually increases the electrical conductivity of the films.

Formaldehyde is the smallest existing aldehyde, a highly reactive color less gas at room temperature and ubiquitously present in our atmosphere. Because of its reactivity leading to the crosslinking of macromolecules like proteins, it is widely used in industrial applications, but also in cell biology in order to preserve cells and tissues for further analysis. In this work, we show that formaldehyde releasing solutions commonly used for fixation of cells, can diffuse via the gas phase to the neighboring well and influence signaling processes in the therein cultured cells. To analyze this effect, we utilized a stable reporter cell line for YAP signaling or a gene expression-based reporter for activation of the NF-κB pathway. We could show that next to formaldehyde, also glutaraldehyde and acetaldehyde were able to activate those signaling pathways. Additionally, especially the stable reporter cell line based on YAP signaling can also be used as sensor for bioavailable formaldehyde, being highly sensitive, easy to use, and reversible. The observed impact of formaldehyde on cellular signaling underscores the need for careful planning of experimental protocols and emphasizes the importance of implementing proper controls when utilizing this reagent in cellular signaling analyses.

Materials containing imidazole have been used as promising substances in the fields of life sciences, environmental science, and electrochemistry. In this study, tailored core–shell particles that respond to acidic solutions and fluorine-containing hydrophobic anions were synthesized through starved-feed emulsion polymerization. Imidazole, which responds to proton acids and hydrophobic anions, was incorporated as a functional moiety into the shell of the particles. The soft and viscoelastic matrix was composed of the copolymer, poly((n-butyl acrylate)-co-(1-vinylimidazole)), allowing for control of the hydrodynamic diameter of the core–shell particles due to the balance between hydrophilic and hydrophobic properties. The size comparison of monodisperse particles in the colloid state was investigated using dynamic light scattering (DLS) and transmission electron microscopy (TEM). Changes in the glass transition temperature, depending on the copolymer ratio, were calculated using the Fox equation. The particles were melt-sheared after extrusion to produce viscoelastic opal films, arranging the particles into colloidal crystal stacks showing vivid structural colors. The optical features changed in response to acidic solutions and hydrophobic anions and were examined using in situ ultraviolet–visible (UV–vis) spectroscopy. The degree of hydrophilicity of the film was compared through contact angle measurements. The manufactured smart opal film can be applied as an affordable sensor that exhibits optical color changes in response to acidic pH and hydrophobic anions.

Hydrogels are natural/synthetic polymer-based materials with a large percentage of water content, usually above 80 %, and are suitable for many application fields such as wearable sensors, biomedicine, cosmetics, agriculture, etc. However, their performance is susceptible to environmental changes in temperature, relative humidity, and mechanical deformation due to their aqueous and soft nature. We investigate the mechanical response of both filled and unfilled alginate/gellan hydrogels using a combined axial-torsional rheometric approach with cylindrical samples of large length/diameter ratio under controlled temperature and relative humidity. Dynamic Mechanical Analysis (DMA) is performed on the same specimen in both torsion and extension under identical experimental conditions. This rheometric approach ensures consistent initial and boundary conditions, which are essential for a reliable estimation of viscoelastic moduli G* and E*, and their dependence on temperature, frequency, and relative humidity. Our findings indicate that humidity critically affects the mechanical response of the material due to sample volume shrinkage, necessitating corrections to the viscoelastic moduli. We also find temperature plays a role only at low/medium relative humidity values. The inclusion of fillers leads to a modest increase in the elasticity of the hydrogel, probably due to restricted water diffusion out of the sample. In connection with the latest, unfilled samples in breaking tests present only slippage due to twist-induced surface water excess, opposite to breakage events shown by filled samples, probably linked to restricted water diffusion.