The development of tailorable and biocompatible three-dimensional (3D) substrates or molecular networks that reliably mimic the extracellular matrix (ECM) and influence cell behavior and growth in vitro is of increasing interest for cell-based applications in the field of tissue engineering and regenerative medicine. In this context, we present a novel coiled coil-based peptide that self-assembles into a 3D-α-helical fibril network and functions as a self-supporting hydrogel. By functionalizing distinct coiled-coil peptides with cellular binding motifs or carbohydrate ligands (mannose), and by utilizing the multivalency and modularity of coiled-coil assemblies, tailored artificial ECMs are obtained. Fibrillar network and ligand density, as well as ligand composition can readily be adjusted by changes in water content or peptide concentrations, respectively. Mesoscopic structure of these networks was assessed by rheology and small-angle neutron scattering experiments. Initial cell viability studies using NIH/3T3 cells showed comparable or even superior cell viability using the presented artificial ECMs, compared to commercially available 3D-cell culture scaffold Matrigel. The herein reported approach presents a reliable (low batch-to-batch variation) and modular pathway toward biocompatible and tailored artificial ECMs.

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Background: Airway mucus provides important protective functions in health and abnormal viscoelasticity is a hallmark of muco-obstructive lung diseases such as cystic fibrosis (CF). However, previous studies of sputum macrorheology from healthy individuals and patients with CF using different experimental protocols yielded in part discrepant results and data on a systematic assessment across measurement settings and conditions remain limited.Objectives: The aim of this study was to develop an optimized and reliable protocol for standardized macrorheological measurements of airway mucus model systems and native human sputum from healthy individuals and patients with muco-obstructive lung disease.Methods: Oscillatory rheological shear measurements were performed using bovine submaxillary mucin (BSM) at different concentrations (2% and 10% solids) and sputum samples from healthy controls (n = 10) and patients with CF (n = 10). Viscoelastic properties were determined by amplitude and frequency sweeps at 25°C and 37°C with or without solvent trap using a cone-plate geometry.Results: Under saturated atmosphere, we did not observe any temperature-dependent differences in 2% and 10% BSM macrorheology, whereas in the absence of evaporation control 10% BSM demonstrated a significantly higher viscoelasticity at 37°C. Similarly, during the measurements without evaporation control at 37°C we observed a substantial increase in the storage modulus G′ and the loss modulus G″ of the highly viscoelastic CF sputum but not in the healthy sputum.Conclusion: Our data show systematically higher viscoelasticity of CF compared to healthy sputum at 25°C and 37°C. For measurements at the higher temperature using a solvent trap to prevent evaporation is essential for macrorheological analysis of mucus model systems and native human sputum. Another interesting finding is that the viscoelastic properties are not much sensitive to the applied experimental deformation and yield robust results despite their delicate consistency. The optimized protocol resulting from this work will facilitate standardized quantitative assessment of abnormalities in viscoelastic properties of airway mucus and response to muco-active therapies in patients with CF and other muco-obstructive lung diseases.

The thermosensitive aggregation behavior in an aqueous solution of a library of amphiphilic BAB* copolymers is studied, where "A" represents a long permanently hydrophilic poly(N,N-dimethylacrylamide) (pDMAm) block, "B" represents a permanently hydrophobic end with an n-dodecyl chain, and "B*" represents a thermoresponsive (TR) block featuring a lower critical solution temperature (LCST). Four polyacrylamides are employed for B*, namely, poly(N-n-propylacrylamide) (pNPAm), poly(Nisopropylacrylamide) (pNiPAm), poly(N,N-diethylacrylamide) (pDEAm), and poly(N-acryloylpyrrolidine) (pNAP), which differ with respect to the hydrophilicity of their amide side chains and LCST behavior. While blocks A and B were kept constant, the lengths of the TR blocks were varied systematically. These amphiphilic copolymers were studied as a function of concentration and temperature via light and neutron scattering (static light scattering (SLS), dynamic light scattering (DLS), small-angle neutron scattering (SANS)). For sufficiently long pNiPAM and pDEAm blocks (DP n > 40), a pronounced hydrophobic effect at temperatures above the LCST transition results in well-structured, ordered aggregates. Thus, the aggregation can be controlled by the choice and length of the TR block, thereby elucidating a so far hardly explored class of temperature-sensitive polymeric amphiphiles.