Synthetic Transient Crosslinks Program the Mechanics of Soft, Biopolymer-Based Materials.

Actin networks are adaptive materials enabling dynamic and static functions of living cells. A central element for tuning their underlying structural and mechanical properties is the ability to reversibly connect, i.e.

DNA Nanotubes as a Versatile Tool to Study Semiflexible Polymers.

Mechanical properties of complex, polymer-based soft matter, such as cells or biopolymer networks, can be understood in neither the classical frame of flexible polymers nor of rigid rods. Underlying filaments remain outstretched due to their non-vanishing backbone stiffness, which is quantified via the persistence length (lp), but they are also subject to strong thermal fluctuations. Their finite bending stiffness leads to unique, non-trivial collective mechanics of bulk networks, enabling the formation of stable scaffolds at low volume fractions while providing large mesh sizes.

Single Actin Bundle Rheology.

Bundled actin structures play an essential role in the mechanical response of the actin cytoskeleton in eukaryotic cells. Although responsible for crucial cellular processes, they are rarely investigated in comparison to single filaments and isotropic networks. Presenting a highly anisotropic structure, the determination of the mechanical properties of individual bundles was previously achieved through passive approaches observing bending deformations induced by thermal fluctuations.

Tuning Synthetic Semiflexible Networks by Bending Stiffness.

The mechanics of complex soft matter often cannot be understood in the classical physical frame of flexible polymers or rigid rods. The underlying constituents are semiflexible polymers, whose finite bending stiffness (κ) leads to nontrivial mechanical responses. A natural model for such polymers is the protein actin.

The ultrastructure of rabbit sclera after scleral crosslinking with riboflavin and blue light of different intensities.

Purpose: We aimed to determine the ultrastructural changes of collagen fibrils and cells in the rabbit sclera after scleral crosslinking using riboflavin and blue light of different intensities. Scleral crosslinking is known to increase scleral stiffness and may inhibit the axial elongation of progressive myopic eyes.

Methods: The equatorial parts of the sclera of one eye of six adult albino rabbits were treated with topical riboflavin solution (0.

Transition from a Linear to a Harmonic Potential in Collective Dynamics of a Multifilament Actin Bundle.

Attractive depletion forces between rodlike particles in highly crowded environments have been shown through recent modeling and experimental approaches to induce different structural and dynamic signatures depending on relative orientation between rods. For example, it has been demonstrated that the axial attraction between two parallel rods yields a linear energy potential corresponding to a constant contractile force of 0.1 pN.

Damage threshold in adult rabbit eyes after scleral cross-linking by riboflavin/blue light application.

Several scleral cross-linking (SXL) methods were suggested to increase the biomechanical stiffness of scleral tissue and therefore, to inhibit axial eye elongation in progressive myopia. In addition to scleral cross-linking and biomechanical effects caused by riboflavin and light irradiation such a treatment might induce tissue damage, dependent on the light intensity used. Therefore, we characterized the damage threshold and mechanical stiffening effect in rabbit eyes after application of riboflavin combined with various blue light intensities.

Dose-dependent collagen cross-linking of rabbit scleral tissue by blue light and riboflavin treatment probed by dynamic shear rheology.

Purpose: To determine the visco-elastic properties of isolated rabbit scleral tissue and dose-dependent biomechanical and morphological changes after collagen cross-linking by riboflavin/blue light treatment.

Material: Scleral patches from 87 adult albino rabbit eyes were examined by dynamic shear rheology. Scleral patches were treated by riboflavin and different intensities of blue light (450 nm), and the impact on the visco-elastic properties was determined by various rheological test regimes.

Tailoring the material properties of gelatin hydrogels by high energy electron irradiation.

Natural hydrogels such as gelatin are highly desirable biomaterials for application in drug delivery, biosensors, bioactuators and extracellular matrix components due to strong biocompatibility and biodegradability. Typically, chemical crosslinkers are used to optimize material properties, often introducing toxic byproducts into the material. In this present work, electron irradiation is employed as a reagent-free crosslinking technique to precisely tailor the viscoelasticity, swelling behavior, thermal stability and structure of gelatin.

Fluorescent beads disintegrate actin networks.

We studied the influence of fluorescent polystyrene beads on both entangled and cross-linked actin networks. Thermal bead fluctuations were observed via video particle tracking and analyzed with one-point microrheology. Illumination of fluorescent beads with their appropriate excitation wavelength leads to a drastic softening of actin gels.