Bioinspired injectable hydrogels for bone regeneration

The effective regeneration of bone/cartilage defects remains a significant clinical challenge, causing irreversible damage to millions annually.Conventional therapies such as autologous or artificial bone grafting often yield unsatisfactory outcomes, emphasizing the urgent need for innovative treatment methods. Biomaterial-based strategies, including hydrogels and active scaffolds, have shown potential in promoting bone/cartilage regeneration. Among them, injectable hydrogels have garnered substantial attention in recent years on account of their minimal invasiveness, shape adaptation, and controlled spatiotemporal release. This review systematically discusses the synthesis of injectable hydrogels, bioinspired approaches-covering microenvironment, structural, compositional, and bioactive component-inspired strategies-and their applications in various bone/cartilage disease models, highlighting bone/cartilage regeneration from an innovative perspective of bioinspired design. Taken together, bioinspired injectable hydrogels offer promising and feasible solutions for promoting bone/cartilage regeneration, ultimately laying the foundations for clinical applications. Furthermore, insights into further prospective directions for AI in injectable hydrogels screening and organoid construction are provided.

Liposome-polymer complex for drug delivery system and vaccine stabilization

Liposomes have been used extensively as micro- and nanocarriers for hydrophobic or hydrophilic molecules. However, conventional liposomes are biodegradable and quickly eliminated, making it difficult to be used for delivery in specific routes, such as the oral and systemic routes. One way to overcome this problem is through complexation with polymers, which is referred to as a liposome complex. The use of polymers can increase the stability of liposome with regard to pH, chemicals, enzymes, and the immune system. In some cases, specific polymers can condition the properties of liposomes to be explicitly used in drug delivery, such as targeted delivery and controlled release. These properties are influenced by the type of polymer, crosslinker, interaction, and bond in the complexation process. Therefore, it is crucial to study and review these parameters for the development of more optimal forms and properties of the liposome complex. This article discusses the use of natural and synthetic polymers, ways of interaction between polymers and liposomes (on the surface, incorporation in lamellar chains, and within liposomes), types of bonds, evaluation standards, and their effects on the stability and pharmacokinetic profile of the liposome complex, drugs, and vaccines. This article concludes that both natural and synthetic polymers can be used in modifying the structure and physicochemical properties of liposomes to specify their use in targeted delivery, controlled release, and stabilizing drugs and vaccines.

Facile fabrication of thermo/redox responsive hydrogels based on a dual crosslinked matrix for a smart on-off switch

Stimuli-responsive or "smart" soft materials have raised considerable attention due to their ability to spontaneously respond to external environmental variations and have a great potential for wide applications. Herein, a thermo/redox responsive hydrogel is facilely constructed based on a dual crosslinked matrix: the primary chemical crosslinked copolymer is composed of thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) and poly(ionic liquid), and the secondary physical crosslinking component is generated by the ionic coordination between iron ions and carboxyl groups in the poly(ionic liquid). The non-covalent ion coordination crosslinking is introduced into a covalently crosslinked network, which further strengthens the soft PNIPAM matrix and enhances the mechanical performances of the hydrogels. The excellent thermosensitivity of PNIPAM and the good conductive property of poly(ionic liquid) provide the hydrogel with an attractive performance as a thermo-responsive switch. Moreover, the trapped iron ions in the network endow the hydrogels with redox-responsiveness, which could be reversibly chemically oxidized and reduced. The mechanical strength of hydrogels could also be tuned by the crosslinked capacity of iron ions within the gel matrix between the strong binding of the oxidized state (Fe3+) and poor coordination of the reduced state (Fe2+). These stimuli-responsive hydrogels have the potential to be used as smart materials for stimuli-responsive devices.