Model for the phase separation of poly(N-isopropylacrylamide)-clay nanocomposite hydrogel based on energy-density functional

Recent advances in the application of clay-containing hydrogels for hemostasis and wound healing

INTRODUCTION

Immediate control of bleeding and anti-infection play important roles in wound management. Multiple organ dysfunction syndrome and death may occur if persistent bleeding, hemodynamic instability, and hypoxemia are not addressed. The combination of clay and hydrogel provides a new outlet for wound hemostasis. In this review, the current research progress of hydrogel/clay composite hemostatic agents was reviewed.

AREAS COVERED

This paper summarizes the characteristics of several kinds of clay including kaolinite, montmorillonite, laponite, sepiolite, and palygorskite. The advantages and disadvantages of its application in hemostasis were also summarized. Future directions for the application of hydrogel/clay composite hemostatic agents are presented.

EXPERT OPINION

Clay can activate the endogenous hemostatic pathway by increasing blood cell concentration and promoting plasma absorption to accelerate the hemostasis. Clay is antimicrobial due to the slow release of metal ions and has a rich surface charge with a high affinity for proteins and cells to promote tissue repair. Hydrogels have some properties such as good biocompatibility, strong adhesion, high stretchability, and good self-healing. Despite promising advances, hydrogel/clay composite hemostasis remains a limitation. Therefore, more evidence is needed to further elucidate the risk factors and therapeutic effects of hydrogel/clay in hemostasis and wound healing.

Nanosheet-hydrogel composites: from preparation and fundamental properties to their promising applications

Hydrogels are an important class of soft materials with elastic and intelligent properties. Nevertheless, these traditional hydrogels usually possess poor mechanical properties and limited functions, which greatly restrict their further applications. With the rapid development of nanotechnology, there have been significant advances in the design and fabrication of functional nanocomposite hydrogels with unique properties and functions. Among various materials, nanosheets with planar topography, large specific surface areas, and versatile physicochemical properties have attracted intense research interest. Herein, this review summarises the synthesis mechanisms, fundamental properties, and promising applications of nanosheet-incorporated hydrogels. In particular, how the nanosheet structure is applied to improve the overall performance of the hydrogel in each application is emphasized. Additionally, the current challenges and prospects are briefly discussed in this area. We expect that the combination of nanosheets and hydrogels can attract more researchers' interest and bring new opportunities in the future.

Mechanics Underpinning Phase Separation of Hydrogels

This paper reveals the underpinning role of mechanical constraints and dynamic loading in triggering volume phase transitions and phase separation of hydrogels. Using the Flory-Rehner free energy that does not predict phase separation of hydrogels under equilibrium free swelling, we show that mechanical constraints can lead to coexistence of multiple phases. We systematically obtain the states of equilibrium for hydrogels under various mechanical constraints and unravel how mechanical constraints change the convexity of the free energy and monotonicity of the stress-stretch curves, leading to phase coexistence. Using a phase-field model, we predict the pattern evolution of phase coexistence and show that many features cannot be captured by the homogeneous states of equilibrium due to large mismatch stretch between the coexisting phases. We further reveal that the system size, quenching rate, and loading rate can significantly influence the phase behavior, which provides insights for experimental studies related to morphological patterns of hydrogels.