Silk‐Pectin Hydrogel with Superior Mechanical Properties,Biodegradability, and Biocompatibility

A new method is developed to prepare silk hydrogels and silk‐pectin hydrogels via dialysis against methanol to obtain hydrogels with high concentrations of silk fibroin. The relationship between the mechanical and biological properties and the structure of the silk‐pectin hydrogels is subsequently evaluated. The present results suggest that pectin associates with silk molecules when the silk concentration exceeds 15 wt%, suggesting that a silk concentration of over 15 wt% is critical to construct interacting silk‐pectin networks. The silk‐pectin hydrogel reported here is composed of a heterogeneous network, which is different from fiber‐reinforced, interpenetrated networks and double‐network hydrogels, as well as high‐stiffness hydrogels (elastic modulus of 4.7 ± 0.9 MPa, elastic stress limit of 3.9 ± 0.1 MPa, and elastic strain limit of 48.4 ± 0.5%) with regard to biocompatibility and biodegradability.     

Preparation of Molecule‐Responsive Microsized Hydrogels via Photopolymerization for Smart Microchannel Microvalves

Microdevices designed for practical environmental pollution monitoring need to detect specific pollutants such as dioxins. Bisphenol A (BPA) has been widely used as a monomer for the synthesis of polycarbonate and epoxy resins. However, the recent discovery of its high potential ability to disrupt human endocrine systems has made the development of smart systems and microdevices for its detection and removal necessary. Molecule‐responsive microsized hydrogels with β‐cycrodextrin (β‐CD) as ligands are prepared by photopolymerization using a fluorescence microscope. The molecule‐responsive micro‐hydrogels show ultra‐quick shrinkage in response to target BPA. Furthermore, the flow rate of a microchannel is autonomously regulated by the molecule‐responsive shrinking of their hydrogels as smart microvalves.

     

Injectable,Interconnected, High‐Porosity Macroporous Biocompatible Gelatin Scaffolds Made by Surfactant‐Free Emulsion Templating

High‐porosity interconnected, thermoresponsive macroporous hydrogels are prepared from oil‐in‐water high internal phase emulsions (HIPEs) stabilized by gelatin‐graft‐poly(N‐isopropylacrylamide). PolyHIPEs are obtained by gelling HIPEs utilizing the thermoresponsiveness of the copolymer components. PolyHIPEs properties can be controlled by varying the aqueous phase composition, internal phase volume ratio, and gelation temperature. PolyHIPEs respond to temperature changes experienced during cell seeding, allowing fibroblasts to spread, proliferate, and penetrate into the scaffold. Encapsulated cells survive ejection of cell‐laden hydrogels through a hypodermic needle. This system provides a new strategy for the fabrication of safe injectable biocompatible tissue engineering scaffolds.

     

Nitrile Oxide‐Norbornene Cycloaddition as a Bioorthogonal Crosslinking Reaction for the Preparation of Hydrogels

This communication describes the first application of cycloaddition between an in situ generated nitrile oxide with norbornene leading to a polymer crosslinking reaction for the preparation of poly(ethylene glycol) hydrogels under physiological conditions. Hydrogels with high water content and robust physical strength are readily formed within 2–5 min by a simple two‐solution mixing method which allows 3D encapsulation of neuronal cells. This bioorthogonal crosslinking reaction provides a simple yet highly effective method for preparation of hydrogels to be used in bioengineering.

     

Light-Sensitive Phenacyl Crosslinked Dextran Hydrogels for Controlled Delivery**

Stimuli-responsive soft materials enable controlled release of loaded drug molecules and biomolecules. Controlled release of potent chemotherapeutic or immunotherapeutic agents is crucial to reduce unwanted side effects. In an effort to develop controlled release strategies that can be triggered by using Cerenkov luminescence, we have developed polymer hydrogels that can release bovine serum albumin and immunoglobulin G by using light (254 nm–375 nm) as a trigger. We describe the synthesis and photochemical characterization of two light sensitive phenacyl bis-azide crosslinkers that are used to prepare transparent self-supporting hydrogel patches. One crosslinker was designed to optimize the overlap with the Cerenkov luminescence emission window, bearing an π-extended phenacyl core, resulting in a high quantum yield (14 %) of photocleavage when irradiated with 375 nm light. We used the extended phenacyl crosslinker for the preparation of protein-loaded dextran hydrogel patches, which showed efficient and selective dosed release of bovine serum albumin or immunoglobulin G after irradiation with 375 nm light. Cerenkov-triggered release is as yet inconclusive due to unexpected side-reactivity. Based on the high quantum yield, efficient release and large overlap with the Cerenkov window, we envision application of these photosensitive soft materials in radiation targeted drug release.     

Self-assembly in magnetic supramolecular hydrogels

Most recent advances in the synthesis of supramolecular hydrogels based on low molecular weight gelators (LMWGs) have focused on the development of novel hybrid hydrogels, combining LMWGs and different additives. The dynamic nature of the noncovalent interactions of supramolecular hydrogels, together with the specific properties of the additives included in the formulation, allow these novel hybrid hydrogels to present interesting features, such as stimuli-responsiveness, gel-sol reversibility, self-healing and thixotropy, which make them very appealing for multiple biomedical and biotechnological applications. In particular, the inclusion of magnetic nanoparticles in the hydrogel matrix results in magnetic hydrogels, a particular type of stimuli-responsive materials that respond to applied magnetic fields. This review focuses on the recent advances in the development of magnetic supramolecular hydrogels, with special emphasis in the role of the magnetic nanoparticles in the self-assembly process, as well as in the exciting applications of these materials.     

自振荡凝胶的仿生运动

定向运动是生命体最基本的功能,是其进化、生存和繁衍的前提。近年来为了研究生命体的运动机制,许多人工系统被相继开发并用于模拟部分生命体的运动行为。在诸多人工仿生系统里,自振荡凝胶由于同时具有内部驱动产生动能、运动定向性、无缆化和环境自适应等性能而备受瞩目。本文介绍了自振荡凝胶仿生运动的化学-机械能转换的理论根源并综述了仿生运动模式研究近期的进展,在此基础上展望了自振荡凝胶运动研究面临的机遇、挑战和未来发展方向。