Cationic homopolypeptides: A versatile tool to design multifunctional antimicrobial nanocoatings.

Postoperative infections are the most common complications faced by surgeons after implant surgery. To address this issue, an emerging and promising approach is to develop antimicrobial coatings using antibiotic substitutes. We investigated the use of polycationic homopolypeptides in a layer-by-layer coating combined with hyaluronic acid (HA) to produce an effective antimicrobial shield.

Polyarginine as a Simultaneous Antimicrobial, Immunomodulatory, and miRNA Delivery Agent within Polyanionic Hydrogel.

Implantation of biomedical devices is followed by immune response to the implant, as well as occasionally bacterial, yeast, and/or fungal infections. In this context, new implant materials and coatings that deal with medical device-associated complications are required. Antibacterial and anti-inflammatory materials are also required for wound healing applications, especially in diabetic patients with chronic wounds.

Insensitivity of dental pulp stem cells migration to substrate stiffness.

Dental pulp stem cells (DPSCs) are a promising cell source for regeneration of dental pulp. Migration is a key event but influence of the microenvironment rigidity (5 kPa at the center of dental pulp to 20 GPa for the dentin) is largely unknown. Mechanical signals are transmitted from the extracellular matrix to the cytoskeleton, to the nuclei, and to the chromatin, potentially regulating gene expression.

Enzyme assisted peptide self-assemblies trigger cell adhesion in high density oxime based host gels.

Peptide supramolecular self-assemblies are recognized as important components in responsive hydrogel based materials with applications in tissue engineering and regenerative medicine. Studying the influence of hydrogel matrices on the self-assembly behavior of peptides and interaction with cells is essential to guide the future development of engineered biomaterials. In this contribution, we present a PEG based host hydrogel material generated by oxime click chemistry that shows cellular adhesion behavior in response to enzyme assisted peptide self-assembly (EASA) within the host gel.

Phase Separation in Supramolecular Hydrogels Based on Peptide Self-Assembly from Enzyme-Coated Nanoparticles.

Spatial localization of biocatalysts, such as enzymes, has recently proven to be an effective process to direct supramolecular self-assemblies in a spatiotemporal way. In this work, silica nanoparticles (NPs) functionalized covalently by alkaline phosphatase (NPs@AP) induce the localized growth of self-assembled peptide nanofibers from NPs by dephosphorylation of Fmoc-FFY peptides (Fmoc: fluorenylmethyloxycarbonyl; F: phenylalanine; Y: tyrosine; : phosphate group). The fibrillary nanoarchitecture around NPs@AP underpins a homogeneous hydrogel, which unexpectedly undergoes a macroscopic shape change over time.

Cell shape and substrate stiffness drive actin-based cell polarity.

A general trait of living cells is their ability to exert contractile stresses on their surroundings and thus respond to substrate rigidity. At the cellular scale, this response affects cell shape, polarity, and ultimately migration. The regulation of cell shape together with rigidity sensing remains largely unknown.

Chromatin de-condensation by switching substrate elasticity.

Mechanical properties of the cellular environment are known to influence cell fate. Chromatin de-condensation appears as an early event in cell reprogramming. Whereas the ratio of euchromatin versus heterochromatin can be increased chemically, we report herein for the first time that the ratio can also be increased by purely changing the mechanical properties of the microenvironment by successive 24 h-contact of the cells on a soft substrate alternated with relocation and growth for 7 days on a hard substrate.

Topological defects in epithelia govern cell death and extrusion.

Epithelial tissues (epithelia) remove excess cells through extrusion, preventing the accumulation of unnecessary or pathological cells. The extrusion process can be triggered by apoptotic signalling, oncogenic transformation and overcrowding of cells. Despite the important linkage of cell extrusion to developmental, homeostatic and pathological processes such as cancer metastasis, its underlying mechanism and connections to the intrinsic mechanics of the epithelium are largely unexplored.

Epithelial Cell Packing Induces Distinct Modes of Cell Extrusions.

The control of tissue growth, which is a key to maintain the protective barrier function of the epithelium, depends on the balance between cell division and cell extrusion rates [1, 2]. Cells within confluent epithelial layers undergo cell extrusion, which relies on cell-cell interactions [3] and actomyosin contractility [4, 5]. Although it has been reported that cell extrusion is also dependent on cell density [6, 7], the contribution of tissue mechanics, which is tightly regulated by cell density [8-12], to cell extrusion is still poorly understood.

Micropillar substrates: a tool for studying cell mechanobiology.

Increasing evidence has shown that mechanical cues from the environment play an important role in cell biology. Mechanotransduction or the study of how cells can sense these mechanical cues, and respond to them, is an active field of research. However, it is still not clear how cells sense and respond to mechanical cues.

Contribution of soft substrates to malignancy and tumor suppression during colon cancer cell division.

In colon cancer, a highly aggressive disease, progression through the malignant sequence is accompanied by increasingly numerous chromosomal rearrangements. To colonize target organs, invasive cells cross several tissues of various elastic moduli. Whether soft tissue increases malignancy or in contrast limits invasive colon cell spreading remains an open question.

Multiarray cell stretching platform for high-magnification real-time imaging.

Aim: This article reports the development of a multiarray microchip with real-time imaging capability to apply mechanical strains onto monolayered cell cultures.

Materials & Methods: Cells were cultured on an 8-µm thick membrane that was positioned in the microscope focal plane throughout the stretching process. Each stretching unit was assembled from three elastomeric layers and a glass coverslip.

The control of chromosome segregation during mitosis in epithelial cells by substrate elasticity.

Materials of defined elasticity, including synthetic material scaffolds and tissue-derived matrices, can regulate biological responses of cells and in particular adhesion, migration, growth and differentiation which are essential parameters for tissue integration. These responses have been extensively investigated in interphase cells, but little is known whether and how material elasticity affects mitotic cells. We used polyelectrolyte multilayer films as model substrates with elastic modulus ranging from Eap = 0 up to Eap = 500 kPa and mitotic PtK2 epithelial cells to address these important questions.

Selective and uncoupled role of substrate elasticity in the regulation of replication and transcription in epithelial cells.

Actin cytoskeleton forms a physical connection between the extracellular matrix, adhesion complexes and nuclear architecture. Because tissue stiffness plays key roles in adhesion and cytoskeletal organization, an important open question concerns the influence of substrate elasticity on replication and transcription. To answer this major question, polyelectrolyte multilayer films were used as substrate models with apparent elastic moduli ranging from 0 to 500 kPa.