Nickel-Catcher-Doped Zwitterionic Hydrogel Coating on Nickel-Titanium Alloy Toward Capture and Detection of Nickel Ions

Flexible coatings based on hydrogel to enhance the biointerface of biomedical implants

The use of biomedical implants in surgical techniques promotes the restoration of lost tissue or organ physiological functions in the body. The interface between different materials determines their interactions and ultimately affects the physicochemical properties of biomedical implants. After implantation, the biointerface plays a crucial role in determining the biocompatibility and functionality of biomedical implants. Surface modification of biomaterials by developing novel biomaterials like various flexible coatings to meet the requirements of biointerfaces, such as mechanical performance, compatibility safety, and biological activities, can improve material-biological interactions by maintaining its original volumetric characteristics. Hydrogels possess excellent plasticity, biodegradability, biocompatibility, and extracellular-matrix-like properties, making them widely used in the biomedical field. Moreover, due to their unique three-dimensional crosslinked hydrophilic network, hydrogels can encapsulate a variety of materials, such as small molecules, polymers, and particle. In recent years, it has been proved that coating biomedical implant materials with flexible hydrogels can optimize the biointerface and holds vast potential for implant surface modification. In this review, we first discussed the potential requirements of the biointerface on the surface of implantable materials in both in vitro and in vivo biological microenvironments. Based on these comprehensive reviews, we also introduced the potential applications of hydrogels in both in vitro and in vivo settings. Finally, this review focused on the challenges faced by the biointerface of implantable materials constructed based on hydrogels and proposed future approaches to inspire researchers with new ideas.

Antibacterial-Based Hydrogel Coatings and Their Application in the Biomedical Field-A Review

Hydrogels exhibit excellent moldability, biodegradability, biocompatibility, and extracellular matrix-like properties, which make them widely used in biomedical fields. Because of their unique three-dimensional crosslinked hydrophilic networks, hydrogels can encapsulate various materials, such as small molecules, polymers, and particles; this has become a hot research topic in the antibacterial field. The surface modification of biomaterials by using antibacterial hydrogels as coatings contributes to the biomaterial activity and offers wide prospects for development. A variety of surface chemical strategies have been developed to bind hydrogels to the substrate surface stably. We first introduce the preparation method for antibacterial coatings in this review, which includes surface-initiated graft crosslinking polymerization, anchoring the hydrogel coating to the substrate surface, and the LbL self-assembly technique to coat crosslinked hydrogels. Then, we summarize the applications of hydrogel coating in the biomedical antibacterial field. Hydrogel itself has certain antibacterial properties, but the antibacterial effect is not sufficient. In recent research, in order to optimize its antibacterial performance, the following three antibacterial strategies are mainly adopted: bacterial repellent and inhibition, contact surface killing of bacteria, and release of antibacterial agents. We systematically introduce the antibacterial mechanism of each strategy. The review aims to provide reference for the further development and application of hydrogel coatings.

Lignin-containing hydrogels with anti-freezing, excellent water retention and super-flexibility for sensor and supercapacitor applications

We developed a highly conductive and flexible, anti-freezing sulfonated lignin (SL)-containing polyacrylic acid (PAA) (SL-g-PAA-Ni) hydrogel, with a high concentration of NiCl₂. Ni²⁺ contributes multi-functions to the preparation of the hydrogel and its final properties, such as fast polymerization reaction as a result of the presence of redox pairs of Ni³⁺/Ni²⁺ and hydroquinone/quinone, and anti-freezing properties of the hydrogel due to the salt effects of NiCl₂ so that at -20 °C the hydrogel shows similar properties to those at the room temperature. Thanks to the effective coordinations of Ni²⁺ with catecholic groups and carboxylic groups, as well as the rich hydrogen bonding capacity, the resultant hydrogel possesses excellent mechanical properties. High ionic conductivity (6.85 S·m^-1) of the hydrogel is obtained due to the supply of high concentration of Ni²⁺. Moreover, the ionic solvation effect of NiCl₂ in the hydrogel imparts excellent water retention ability, with water retention of ~93 % after 21-day storage. The SL-g-PAA-Ni hydrogel can accurately detect various human motions at -20 °C. The supercapacitor assembled from SL-g-PAA-Al hydrogel at -20 °C manifests a high specific capacitance of 252 F·g^-1, with maximum energy density of 26.97 Wh·kg^-1, power density of 2667 W·kg^-1, and capacitance retention of 96.7 % after 3000 consecutive charge-discharge cycles.