Chemical reaction networks (CRN) embedded in hydrogels can transform responsive materials into complex self‐regulating materials that generate feedback to counter the effect of external stimuli. This study presents hydrogels containing the β‐cyclodextrin (CD) and ferrocene (Fc) host–guest pair as supramolecular crosslinks where redox‐responsive behavior is driven by the enzyme–fuel couples horse radish peroxidase (HRP)–H2O2 and glucose oxidase (GOx)–d‐glucose. The hydrogel can be tuned from a responsive to a self‐regulating supramolecular system by varying the concentration of added reduction fuel d‐glucose. The onset of self‐regulating behavior is due to formation of oxidation fuel in the hydrogel by a cofactor intermediate GOx[FADH2]. UV/Vis spectroscopy, rheology, and kinetic modeling were employed to understand the emergence of out‐of‐equilibrium behavior and reveal the programmable negative feedback response of the hydrogel, including the adaptation of its elastic modulus and its potential as a glucose sensor.

The fabrication of biocatalytic, porous, recyclable, and mechanoresponsive elastic sponge like material is shown from a mixture of core–shell alkaline phosphatase-polymer surfactant bioconjugates and nanoparticles.

Hydrogels have emerged as one of the best studied, widely applied and most versatile classes of soft materials. Hydrogels are important biomimetic nanomaterials comparable to extracellular matrices in terms of water content, porosity, and rigidity. In this regard, self‐assembled hydrogels based on supramolecular host‐guest interactions have enabled unique characteristics like stimuli response, self‐healing, shape memory and self‐regulation. In particular, the use of cyclodextrins and their host‐guest chemistry is a powerful tool for the development of functional hydrogels with unprecedented properties. In this article, recent advances on hydrogels based on supramolecular chemistry of cyclodextrins are reviewed to provide an overview of the manifold design strategies, material properties and areas of application. We contrast the progress on cyclodextrin containing polymer gels to that of their low molecular weight counterparts by highlighting selected publications from each of these subcategories.

Polyethyleneimine (PEI), a cationic polyelectrolyte, finds great utility as a nonviral gene transfection vector. The mechanism of gene delivery process across the cell membrane through PEI-based polyplexes is still much debated; however, a general consensus is that the proton binding-based PEI conformational changes occur as the pH alters during the process. Taking a step back, even the understanding of wide pH range (from 1 to 10) dependent conformational changes for neat PEI in explicit water remains elusive. In pursuit of this objective, using a combination of optical and electron microscopy, we observed that a dilute aqueous solution of linear or branched PEI (M w ranging from 0.8 to 750 kDa) at room temperature and having pH in the range 2.5–4 undergoes a completely novel and highly unprecedented slow self-assembly process to form a micrometer-sized thick fibrillar network. These self-assembled structures are highly robust, irreversible, and interestingly, generic for PEI and form over 24–72 h in a dilute aqueous solution irrespective of the molecular weight and configuration of PEI. A combination of turbidity and acid titration experiments on PEI aqueous solutions having different pH values reveal that the mechanism of this hierarchical self-assembly (between pH 2.5-4) can be explained by the unique protonation behavior of PEI chains and their ability to undergo conformational/morphological transitions.