Mechanistic insights into gelation and rheological behavior of Pluronic F127-based thermoresponsive hydrogels

How Gellan gum gelation is affected by acyl substituents: from hierarchical organization to simple viscoelastic behavior.

Gellan gum, a linear anionic exopolysaccharide, is widely employed as a gelling agent owing to its biocompatibility and tunable rheological properties. Its degree of acylation determines high acyl (HA-Gg) and low acyl (LA-Gg) forms, yielding hydrogels with different chemical-physical properties. Rheological measurements show a distinct gelation mechanism: LA-Gg forms rigid, ionically crosslinked networks (G' ∼25 kPa; critical strain ≈2%) exhibiting two-step yielding, whereas HA-Gg produces softer elastic gels lacking hierarchical organization (G' ∼1 kPa; LVR extends up to ∼500% strain). Despite their wide use, the molecular mechanism by which acyl substituents affect Gellan gum gelation is still lacking. Here a comparison between HA-Gg and LA-Gg, combining spectroscopy, rheology, and atomistic molecular dynamics (MD) simulations within a single framework is performed, providing a molecular-level interpretation of these differences. In dilute regime, circular dichroism measurements reveals distinct behavior for LA-Gg and HA-Gg, in coil and double-helix conformations, respectively. MD simulations explain the observed features, showing that acylation enhances intra-helix hydrogen bonding, stabilizing the double-helix structure, while hindering calcium-mediated inter-helix associations. Overall, acylation exerts a dual effect: it strengthens local structural units, but weakening supramolecular connectivity. This interplay governs macroscopic mechanical response, enabling rational design of Gellan gum hydrogels with tailored properties.

An Injectable, Self-Healing Hydrogel Based on G-Quadruplexes/Phenylboronic Acid Composites with Antibacterial Activity

The injectable, self-healing G-quadruplex hydrogel constructed in this study integrates a porous architecture, dynamic reversibility, and robust biological functionality, highlighting its promising potential in antibacterial applications.

Spontaneous Phase Separation Enables Rapid, Polymerization-Free Fabrication of Gels.

Hydrogels are cross-linked polymeric networks with wide applications in drug delivery, tissue engineering, biosensing, and environmental remediation. These hydrogels additionally host living cells, small molecules, and biological propagules, which further expand the applications of these materials. However, most, if not all, fabrication methods require covalent modifications. In this work, by deliberately selecting polymers with a known propensity to phase separate and formulating compositions far from the binodal boundary, we demonstrate the propensity of the system to transition directly into viscoelastic liquids or gels. This behavior is demonstrated using a model system of poly(ethylene glycol) (PEG) and dextran (DEX). We carried out rheological studies to provide insights into the viscoelastic behavior of these gels. We systematically characterized the gels through colorimetric assays, FTIR, MALDI-TOF, and thermogravimetric analysis (TGA) to discern the molecular compositions and solvent content of the gels. These experimental findings are supplemented with coarse-grained (CG) simulation insights to investigate the mechanistic origins of phase separation propensity with varying molecular weights of DEX. We utilized coexisting densities in the two phases using CG simulations to predict the role of DEX molecular weight in the partitioning of PEG and DEX in the two phases. Finally, we exploit the fabricated gel's ability to encapsulate live cells, antibiotics, and plant seeds. We anticipate that this ATPS-based fabrication technique will provide a scalable, cross-linker-free route to multifunctional gels, enabling advanced applications in drug delivery and responsive materials.

Structural reinforcement of Pluronic F127/chitosan thermoresponsive hydrogels through polydopamine incorporation for controllable drug transport.

Results establish PDA-mediated non-covalent reinforcement as an effective crosslinker-free strategy for engineering thermoresponsive hydrogels with tunable network mechanics and controllable NIR-responsive drug transport for localized chemo-photothermal therapy.

Tunable Sol-Gel Transition in Poloxamer Blends for Injectable Osteoarticular Applications.

The results show that careful selection and optimization of poloxamer blends allow tailoring material properties for specific biomedical functions, and make them practical for further development in injectable biomaterials and drug delivery systems for osteoarticular repair.

Self-Degradable Temporary Plugging Agent Based on Dynamic Covalent Bond-Crosslinked Double-Network Hydrogels