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In-Gel Direct Laser Writing for 3D-Designed Hydrogel Composites That Undergo Complex Self-Shaping
Self-shaping and actuating materials inspired by biological system have enormous potential for biosensor, microrobotics, and optics. However, the control of 3D-complex microactuation is still challenging due to the difficulty in design of nonuniform internal stress of micro/nanostructures. Here, we develop in-gel direct laser writing (in-gel DLW) procedure offering a high resolution inscription whereby the two materials, resin and hydrogel, are interpenetrated on a scale smaller than the wavelength of the light. The 3D position and mechanical properties of the inscribed structures could be tailored to a resolution better than 100 nm over a wide density range. These provide an unparalleled means of inscribing a freely suspended microstructures of a second material like a skeleton into the hydrogel body and also to direct isotropic volume changes to bending and distortion motions. In the combination with a thermosensitive hydrogel rather small temperature variations could actuate large amplitude motions. This generates complex modes of motion through the rational engineering of the stresses present in the multicomponent material. More sophisticated folding design would realize a multiple, programmable actuation of soft materials. This method inspired by biological system may offer the possibility for functional soft materials capable of biomimetic actuation and photonic crystal application.
DNA Nanotechnology Enters Cell Membranes
DNA is more than a carrier of genetic information: It is a highly versatile structural motif for the assembly of nanostructures, giving rise to a wide range of functionalities. In this regard, the structure programmability is the main advantage of DNA over peptides, proteins, and small molecules. DNA amphiphiles, in which DNA is covalently bound to synthetic hydrophobic moieties, allow interactions of DNA nanostructures with artificial lipid bilayers and cell membranes. These structures have seen rapid growth with great potential for medical applications. In this Review, the current state of the art of the synthesis of DNA amphiphiles and their assembly into nanostructures are first summarized. Next, an overview on the interaction of these DNA amphiphiles with membranes is provided, detailing on the driving forces and the stability of the interaction. Moreover, the interaction with cell surfaces in respect to therapeutics, biological sensing, and cell membrane engineering is highlighted. Finally, the challenges and an outlook on this promising class of DNA hybrid materials are discussed.
Turning a Killing Mechanism into an Adhesion and Antifouling Advantage
Mild and universal methods to introduce functionality in polymeric surfaces remain a challenge. Herein, a bacterial killing mechanism based on amphiphilic antimicrobial peptides is turned into an adhesion advantage. Surface activity (surfactant) of the antimicrobial liquid chromatography peak I (LCI) peptide is exploited to achieve irreversible binding of a protein–polymer hybrid to surfaces via physical interactions. The protein–polymer hybrid consists of two blocks, a surface-affine block (LCI) and a functional block to prevent protein fouling on surfaces by grafting antifouling polymers via single electron transfer-living radical polymerization (SET-LRP). The mild conditions of SET-LRP of N-2-hydroxy propyl methacrylamide (HPMA) and carboxybetaine methacrylamide (CBMAA) preserve the secondary structure of the fusion protein. Adsorption kinetics and grafting densities are assessed using surface plasmon resonance and ellipsometry on model gold surfaces, while the functionalization of a range of artificial and natural surfaces, including teeth, is directly observed by confocal microscopy. Notably, the fusion protein modified with poly(HPMA) completely prevents the fouling from human blood plasma and thereby exhibits a resistance to protein fouling that is comparable to the best grafted-from polymer brushes. This, combined with their simple application on a large variety of materials, highlights the universal and scalable character of the antifouling concept. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim