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Peptides naturally have stimuli‐adaptive structural conformations that are advantageous for endowing synthetic materials with dynamic functionalities. Here, we report a carbodiimide‐based approach, combined with electrostatic modulation, to instruct π‐conjugated peptides to self‐assemble and be responsive to thermal disassembly cues upon consumption of the assembly trigger. Quaterthiophene‐functionalized peptides are utilized as a model system herein to study the formation of nanostructures at non‐equilibrium states. Peptides were designed to have aspartic acid at the termini to allow intramolecular anhydride formation upon adding carbodiimide, which consequentially reduces the electrostatic repulsion and facilitates assembly. We show that the carbodiimide‐fueled assembly and subsequent thermally assisted disassembly can be modulated by the net charge of the peptidic monomers, suggesting an assembly mechanism that can be encoded by sequence design. This carbodiimide‐based approach for the assembly of designer π‐conjugated systems offers a unique opportunity to develop bioelectronic supramolecular materials with controllable formation of dynamic and stimuli‐responsive structures.

 

Spatiotemporally functionalized hydrogels have exciting applications in tissue engineering, but their preparation often relies on radical‐based strategies that can be deleterious in biological settings. Herein, the computationally guided design, synthesis, and application of a water‐soluble cyclopentadienone‐norbornadiene (CPD‐NBD) adduct is disclosed as a diene photocage for radical‐free Diels‐Alder photopatterning. We show that this scalable CPD‐NBD derivative is readily incorporated into hydrogel formulations, providing gels that can be patterned with dienophiles upon 365 nm uncaging of cyclopentadiene. Patterning is first visualized through conjugation of cyanine dyes, then biological utility is highlighted by patterning peptides to direct cellular adhesion. Finally, the ease of use and versatility of this CPD‐NBD derivative is demonstrated by direct incorporation into a commercial 3D printing resin to enable the photopatterning of structurally complex, printed hydrogels.

 

Hydrogels hold much promise for 3D printing of functional living materials; however, challenges remain in tailoring mechanical robustness as well as biological performance. In addressing this challenge, the modular synthesis of functional hydrogels from 3‐arm diblock copolypeptide stars composed of an inner poly(l‐glutamate) domain and outer poly(l‐tyrosine) or poly(l‐valine) blocks is described. Physical crosslinking due to ß‐sheet assembly of these star block copolymers gives mechanical stability during extrusion printing and the selective incorporation of methacrylate units allows for subsequent photocrosslinking to occur under biocompatible conditions. This permits direct ink writing (DIW) printing of bacteria‐based mixtures leading to 3D objects with high fidelity and excellent bacterial viability. The tunable stiffness of different copolypeptide networks enables control over proliferation and colony formation for embeddedEscherichia colibacteria as demonstrated via isopropyl ß‐d‐1‐thiogalactopyranoside (IPTG) induction of green fluorescent protein (GFP) expression. This translation of molecular structure to network properties highlights the versatility of these polypeptide hydrogel systems with the combination of writable structures and biological activity illustrating the future potential of these 3D‐printed biocomposites.

 

This review summarizes recent progress in investigating polymer systems by using Differential dynamic microscopy (DDM), a rapidly emerging approach that transforms a commercial microscope by combining real‐space information with the powerful capabilities of conventional light scattering analysis. DDM analysis of a single microscope movie gives access to the sample dynamics in a wide range of scattering wave‐vectors, enabling contemporary polymer science experiments that would be difficult or impossible with standard light scattering techniques. Examples of application include the characterization of polymer solutions and networks, of polymer based colloidal systems, of biopolymers, and of cellular motility in polymeric fluids. Further applications of DDM to a variety of polymer systems are suggested to be just behind the corner and it is thus likely that DDM will become a tool of choice of the modern experimental polymer scientists.

 

Silicone elastomer medical implants are ubiquitous in medicine, particularly for breast augmentation. However, when these devices are placed within the body, disruption of the natural biological interfaces occurs, which significantly changes the native energy-dissipation mechanisms of living systems. These new interfaces can introduce non-physiological contact pressures and tribological conditions that provoke inflammation and soft tissue damage. Despite their significance, the biotribological properties of implant-tissue and implant-extracellular matrix (ECM) interfaces remain poorly understood. Here, we developed an in vitro model of soft tissue damage using a custom-built in situ biotribometer mounted onto a confocal microscope. Sections of commercially-available silicone breast implants with distinct and clinically relevant surface roughness ([Formula: see text]m, [Formula: see text]m, and [Formula: see text]m) were mounted to spherically-capped hydrogel probes and slid against collagen-coated hydrogel surfaces as well as healthy breast epithelial (MCF10A) cell monolayers to model implant-ECM and implant-tissue interfaces. In contrast to the “smooth” silicone implants ([Formula: see text]m), we demonstrate that the “microtextured” silicone implant ([Formula: see text]m) induced higher frictional shear stress ([Formula: see text]  Pa), which led to greater collagen removal and cell rupture/delamination. Our studies may provide insights into post-implantation tribological interactions between silicone breast implants and soft tissues. 

Abstract Some textured silicone breast implants with high average surface roughness (‘macrotextured’) have been associated with a rare cancer of the immune system, Breast Implant-Associated Anaplastic Large Cell Lymphoma (BIA-ALCL). Silicone elastomer wear debris may lead to chronic inflammation, a key step in the development of this cancer. Here, we model the generation and release of silicone wear debris in the case of a folded implant-implant (‘shell-shell’) sliding interface for three different types of implants, characterized by their surface roughness. The ‘smooth’ implant shell with the lowest average surface roughness tested (R a = 2.7 ± 0.6 μ m) resulted in average friction coefficients of μ avg = 0.46 ± 0.11 across 1,000 mm of sliding distance and generated 1,304 particles with an average particle diameter of D avg = 8.3 ± 13.1 μ m. The ‘microtextured’ implant shell (R a = 32 ± 7.0 μ m) exhibited μ avg = 1.20 ± 0.10 and generated 2,730 particles with D avg = 4.7 ± 9.1 μ m. The ‘macrotextured’ implant shell (R a = 80 ± 10 μ m) exhibited the highest friction coefficients, μ avg = 2.82 ± 0.15 and the greatest number of wear debris particles, 11,699, with an average particle size of D avg = 5.3 ± 3.3 μ m. Our data may provide guidance for the design of silicone breast implants with lower surface roughness, lower friction, and smaller quantities of wear debris.