Autonomous Chitosan-Based Self-Healing Hydrogel Formed through Noncovalent Interactions

A facile strategy was developed for the formation of an autonomous chitosan-based self-healing hydrogel. This hydrogel was fabricated using in situ free radical polymerization of acrylic acid (AA) and acrylamide (AM) in the presence of chitosan in dilute acetic acid aqueous solution under mild conditions. The in situ formed hydrogel is mainly composed of chitosan graft copolymers (CS-g-P­(AM-r-AA)) and a small amount of nongrafted copolymers (P­(AM-r-AA)), which interact with each other through a combination of multiple noncovalent interactions, including the interchain electrostatic complexation between −[AA]– segments and positively charged amino groups of chitosan, the H-bonding between −[AM]– segments, and the H-bonding between −[AM]– segments and the chitosan backbone. Owing to the cooperation of these noncovalent interactions and the reversible nature of the noncovalent network structure, the obtained hydrogel exhibits rapid network recovery, high stretchability, and efficient autonomous self-healing properties. The hydrogel can also dissolve completely in dilute acidic aqueous solution under mild conditions, visibly reflecting the unique network feature of this self-healing hydrogel system

Development of Lignin Supramolecular Hydrogels with Mechanically Responsive and Self-Healing Properties

The development of functional polymers from renewable lignin is attractive due to the depletion of fossil fuel and increasing environmental usage. A series of poly­(ethylene glycol) methyl ether methacrylate (PEGMA)-grafted lignin hyperbranched copolymers were prepared by atom transfer radical polymerization (ATRP). The chemical structures, molecular characteristic and thermal properties of these copolymers were evaluated and such copolymers were prepared in a range of molecular weights from 38.7 to 65.0 kDa by adjusting the PEGMA-to-lignin weight ratio. As a result from their hyperbranch architecture, their aqueous solutions were found to form supramolecular hydrogels with a very low critical gelation concentration of 1 wt % copolymers, in the presence of α-cyclodextrin (α-CD). The rheological properties of the supramolecular assemblies were investigated and these hydrogel systems showed tunable mechanical response and excellent self-healing capability. Combined with good biocompatibility, these new types of green supramolecular hydrogels based on lignin–PEGMA/cyclodextrin inclusion are potentially useful as a smart biomaterial for biomedical application

Highly Efficient Supramolecular Aggregation-Induced Emission-Active Pseudorotaxane Luminogen for Functional Bioimaging

The direct tracking of cells using fluorescent dyes is a constant challenge in cell therapy due to aggregation-induced quenching (ACQ) effect and biocompatibility issues. Here, we demonstrate the development of a biocompatible and highly efficient aggregation-induced emission (AIE)-active pseudorotaxane luminogen based on tetraphenylethene conjugated poly­(ethylene glycol) (TPE-PEG₂) (guest) and α-cyclodextrin (α-CD) (host). It is capable of showing significant fluorescent emission enhancement at the 400–600 nm range when excited at 388 nm, without increasing the concentration of AIE compound. The fluorescent intensity of TPE-PEG₂ solution was effectively enhanced by 4–12 times with gradual addition of 1–4 mM of α-CD. 2D NOSEY ¹H NMR revealed clear correlation spots between the characteristic peaks of α-CD and PEG, indicating the interaction between protons of ethylene glycol and cyclodextrin, and the structures are mainly based on threaded α-CD. The host–guest complex exhibits boosted fluorescent emission because the PEG side chains are confined in “nano-cavities” (host), thus, applying additional restriction on intermolecular rotation of TPE segments. <i>In vitro</i> cell experiments demonstrated the potential of AIE-active pseudorotaxane polymer as a biocompatible bioimaging probe