Sponge-like porous polyvinyl alcohol/chitosan-based hydrogel with integrated cushioning, pH-indicating and antibacterial functions.

Developing a packaging material with integrated cushioning, intelligent and active functions is highly desired but remains challenging in the food industry. Here we show that a sponge-like porous hydrogel with pH-indicating and antibacterial additives can meet this requirement. We use polyvinyl alcohol and chitosan as the primary polymers to construct a hydrogel with hierarchical structures through a freeze-casting method in combination with salting-out treatment. The synergy of aggregated polymer chains and the sponge-like porous structure makes the hydrogel resilient and efficient in energy absorption. It also enables rapid movement of molecules/particles and fast reaction due to the large specific surface area of the pore structures and the large amount of free water in it, leading to a sensitive pH-indicating function. The hydrogel shows an obvious color variation within a wide pH range in 3 min. The silver nanoparticles are fixed in the dense polymer networks, enabling a lasting release of silver ions. The porous structure makes the silver ion reach the protected item in a short time, achieving an antibacterial effect against S. aureus and E. coli with little cytotoxicity. This work paves the way for fabricating multifunctional hydrogels for diverse advanced packaging systems.

In Situ Rapid-Formation Sprayable Hydrogels for Challenging Tissue Injury Management.

Rapid-acting, convenient, and broadly applicable medical materials are in high demand for the treatment of extensive and intricate tissue injuries in extremely medical scarcity environment, such as battlefields, wilderness, and traffic accidents. Conventional biomaterials fail to meet all the high criteria simultaneously for emergency management. Here, a multifunctional hydrogel system capable of rapid gelation and in situ spraying, addressing clinical challenges related to hemostasis, barrier establishment, support, and subsequent therapeutic treatment of irregular, complex, and urgent injured tissues, is designed. This hydrogel can be fast formed in less than 0.5 s under ultraviolet initiation. The precursor maintains an impressively low viscosity of 0.018 Pa s, while the hydrogel demonstrates a storage modulus of 0.65 MPa, achieving the delicate balance between sprayable fluidity and the mechanical strength requirements in practice, allowing flexible customization of the hydrogel system for differentiated handling and treatment of various tissues. Notably, the interactions between the component of this hydrogel and the cell surface protein confer upon its inherently bioactive functionalities such as osteogenesis, anti-inflammation, and angiogenesis. This research endeavors to provide new insights and designs into emergency management and complex tissue injuries treatment.

Dopamine-assisted co-deposition of hydroxyapatite-functionalised nanoparticles of polydopamine on implant surfaces to promote osteogenesis in environments with high ROS levels.

Environments with high reactive oxygen species (ROS) levels, which are common in patients with diseases such as diabetes, periodontitis, and osteoporosis, impair the osseointegration of implants. To address this issue, by using a one-pot dopamine-assisted co-deposition method, we constructed a three-dimensional coating of hydroxyapatite-functionalised nanoparticles of polydopamine (HA/nPDAs) on implant surfaces, where polydopamine is designed to protect cells via scavenging excessive ROS and HA facilitates osteogenesis. First, nanoparticles of polydopamine (nPDAs) were prepared by self-polymerization and assembly of dopamine under alkaline conditions, and HA/nPDAs were obtained by incubating nPDAs in simulated body fluid (SBF) due to metal chelation and ionic interactions triggered by the catechol moieties of PDA. Thereafter, HA/nPDAs with thickness of ~4 µm were constructed on titanium surfaces by immersing titanium discs in a weak alkaline solution of HA/nPDAs and dopamine through interface interactions driven by catechol chemistry. The properties of coatings (e.g., thickness, composition, hydrophilia and morphology) can be controlled by preparation conditions such as mineralization time and reactant concentration. The coatings display efficient ROS-scavenging ability, promote cell proliferation, and upregulate the activity of alkaline phosphatase and the expression of osteogenesis-related genes in environments with high or normal ROS levels, demonstrating the great promise of such coatings for osseointegration promotion, especially in the state of high ROS in diseases. This study provides a facile, efficient, mild, and universal strategy in engineering functional surfaces on any substrates for diversified applications by simple variation of co-deposited components, through taking advantages of versatile catechol chemistry and nanoparticles with stereo structure and great specific surface area.