arXiv subjects

Changxin Dong

Publications and source records attributed to Changxin Dong.

4 recordsLinked to original sources

arXiv2025

Evolving transport properties of dynamic hydrogels enable self-tuning of short- and long-term cargo delivery

Hydrogels are crosslinked polymer networks with high water content, widely employed in biomedical applications such as drug delivery, tissue engineering, and regenerative medicine. Injectable, depot-forming hydrogels enable sustained release of therapeutic agents by modulating macromolecular diffusion through dynamic polymer networks. However, achieving reliable control over release kinetics remains a challenge, as the injection process induces shear-mediated disruption of transient crosslinks, leading to an initial burst release that can cause local toxicity and compromise therapeutic efficacy. Here, we present a hydrogel formulation strategy designed to restore network structure post-injection through rapid reformation of dynamic crosslinks, enabling time-dependent regulation of diffusion properties. By tuning viscoelastic parameters, including stress relaxation time and network recovery rate, we reduced the extent of burst release without compromising sustained delivery. Using model protein cargo, we demonstrate in both $in~vitro$ and $in~vivo$ settings that hydrogels with faster crosslink reformation kinetics exhibit significantly lower early-phase release while maintaining long-term delivery comparable to unmodified formulations. These results establish a mechanistic framework for decoupling short- and long-term release behavior, offering a broadly applicable strategy for precise drug delivery in soft tissue environments.

cond-mat.soft↗

arXiv2025

Hydrogel-to-Aerogel Transitions in Polymer-Particle Hydrogels Expand the Wildfire Defense Window

The 2025 Los Angeles wildfires caused widespread urban destruction and displacement, and severe economic losses, highlighting the urgent need for better fire retardants. Current fire suppression strategies rely heavily on water, chemical fire retardants, and water-enhancing gels, which use superabsorbent polymers to retain water and adhere to substrates, offering extended fire protection compared to water alone. However, their effectiveness is limited by evaporation and degradation under extreme heat and wind conditions. This study investigates the thermal properties, evaporation dynamics, and fire retardancy mechanisms of a novel polymer-particle (PP) hydrogel with aerogel-forming capabilities. The boiling-induced water vapor expansion and bubble nucleation drive the transformation of the hydrogel into a highly porous, foam-like fire-retardant coating upon rapid heat desiccation, enhancing thermal insulation. By evaluating the retardancy window across different evaporation stages under high heat and wind conditions, this study aims to determine the duration, effectiveness, and governing physical mechanisms of this unique retardant system. These findings provide a framework for designing the next generation of fire retardants with optimized thermal stability and extended protection for wildfire mitigation.

cond-mat.mtrl-sci↗

arXiv2024

Water-enhancing gels exhibiting heat-activated formation of silica aerogels for protection of critical infrastructure during catastrophic wildfire

A promising strategy to address the pressing challenges with wildfire, particularly in the wildland-urban interface (WUI), involves developing new approaches for preventing and controlling wildfire within wildlands. Among sprayable fire-retardant materials, water-enhancing gels have emerged as exceptionally effective for protecting civil infrastructure. They possess favorable wetting and viscoelastic properties that reduce the likelihood of ignition, maintaining strong adherence to a wide array of surfaces after application. Although current water-enhancing hydrogels effectively maintain surface wetness by creating a barricade, they rapidly desiccate and lose efficacy under high heat and wind typical of wildfire conditions. To address this limitation, we developed unique biomimetic hydrogel materials from sustainable cellulosic polymers crosslinked by colloidal silica particles that exhibit ideal viscoelastic properties and facile manufacturing. Under heat activation, the hydrogel transitions into a highly porous and thermally insulative silica aerogel coating in situ, providing a robust protective layer against ignition of substrates, even when the hydrogel fire suppressant becomes completely desiccated. By confirming the mechanical properties, substrate adherence, and enhanced substrate protection against fire, these heat-activatable biomimetic hydrogels emerge as promising candidates for next-generation water-enhancing fire suppressants. These advancements have the potential to dramatically improve our ability to protect homes and critical infrastructure during wildfire.

cond-mat.mtrl-sci↗

arXiv2023

Biomimetic non-ergodic aging by dynamic-to-covalent transitions in physical hydrogels

Hydrogels are soft materials engineered to suit a multitude of applications that exploit their tunable mechanochemical properties. Dynamic hydrogels employing noncovalent, physically crosslinked networks dominated by either enthalpic or entropic interactions enable unique rheological and stimuli-responsive characteristics. In contrast to enthalpy-driven interactions that soften with increasing temperature, entropic interactions result in largely temperature-independent mechanical properties. By engineering interfacial polymer-particle interactions, we can induce a dynamic-to-covalent transition in entropic hydrogels that leads to biomimetic non-ergodic aging in the microstructure without altering the network mesh size. This transition is tuned by varying temperature and formulation conditions such as $p$H, which allows for multivalent tunability in properties. These hydrogels can thus be designed to exhibit either temperature-independent metastable dynamic crosslinking or time-dependent stiffening based on formulation and storage conditions, all while maintaining strucutural features critical for controlling mass transport, akin to many biological tissues. Such robust materials with versatile and adaptable properties can be utilized in applications such as wildfire suppression, surgical adhesives, and depot-forming injectable drug delivery systems.

cond-mat.soft↗