Super-Rapid In Situ Formation of a Silver Ion-Induced Supramolecular Hydrogel with Efficient Antibacterial Activity for Root Canal Disinfection

Recent Advances in Functional Hydrogels for Treating Dental Hard Tissue and Endodontic Diseases

Oral health is the basis of human health, and almost everyone has been affected by oral diseases. Among them, endodontic disease is one of the most common oral diseases. Limited by the characteristics of oral biomaterials, clinical methods for endodontic disease treatment still face large challenges in terms of reliability and stability. The hydrogel is a kind of good biomaterial with an adjustable 3D network structure, excellent mechanical properties, and biocompatibility and is widely used in the basic and clinical research of endodontic disease. This Review discusses the recent advances in functional hydrogels for dental hard tissue and endodontic disease treatment. The emphasis is on the working principles and therapeutic effects of treating different diseases with functional hydrogels. Finally, the challenges and opportunities of hydrogels in oral clinical applications are discussed and proposed. Some viewpoints about the possible development direction of functional hydrogels for oral health in the future are also put forward. Through systematic analysis and conclusion of the recent advances in functional hydrogels for dental hard tissue and endodontic disease treatment, this Review may provide significant guidance and inspiration for oral disease and health in the future.

Mechanisms of Triton X-100 reducing the Ag+-resistance of Enterococcus faecalis

To investigate the mechanism of Triton X-100 (TX-100) reducing the Ag+-resistance of Enterococcus faecalis (E. faecalis), and evaluate the antibacterial effect of TX-100 + Ag+ against the induced Ag+-resistant E. faecalis (AREf). The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of AgNO3 against E. faecalis with/without TX-100 were determined to verify the enhanced antibacterial activity. Transmission electron microscopy (TEM) was used to observe the morphological changes of E. faecalis after treatment. The intra- and extracellular concentration of Ag+ in treated E. faecalis was evaluated using inductively coupled plasma mass spectrometer (ICP-MS). The changes in cell membrane potential and integrity of treated E. faecalis were also observed using the flow cytometer. Moreover, AREf was induced through continuous exposure to sub-MIC of Ag+ and the antibacterial effect of TX-100 + Ag+ on AREf was further evaluated. The addition of 0.04% TX-100 showed maximal enhanced antibacterial effect of Ag+ against E. faecalis. The TEM and ICP-MS results demonstrated that TX-100 could facilitate Ag+ to enter E. faecalis through changing the membrane structure and integrity. Flow cytometry further showed the effect of TX-100 on membrane potential and permeability of E. faecalis. In addition, the enhanced antibacterial effect of TX-100 + Ag+ was also confirmed on induced AREf. TX-100 can facilitate Ag+ to enter E. faecalis through disrupting the membrane structure and changing the membrane potential and permeability, thus reducing the Ag+-resistance of E. faecalis and enhancing the antibacterial effect against either normal E. faecalis or induced AREf.

Thermosensitive hydrogel with programmed dual-octenidine release combating biofilm for the treatment of apical periodontitis

The utilization of intracanal medicaments is an indispensable procedure in root-canal treatment. However, the conventional intracanal medicaments still need improvement regarding antimicrobial efficacy and ease of clinical operation. To address the above issues, OCT/PECT@OCT + ALK composite hydrogel characterized by programming sequential release of dual antimicrobial agents has been proposed. Thanks to the self-assemble ability of amphiphilic copolymer poly(ε-caprolactone-co-1,4,8-trioxa [4.6]spiro-9-undecanone)-poly(ethylene glycol)-poly(ε-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-undecanone) (PECT), dual hydrophilic and hydrophobic antimicrobial agents could be easily encapsulated in the hydrogel system and tailored for sequential drug release for a better antibiofilm effect. The hydrophilic octenidine (Octenidine dihydrochloride, OCT-HCl) is encapsulated in the hydrophilic part of hydrogel for instantaneous elevating the drug concentration through bursting release, and the hydrophobic octenidine (Octenidine, OCT) is further loaded into the PECT nanoparticles to achieve a slower and sustained-release profile. Additionally, calcium hydroxide (Ca(OH)2) was incorporated into the system and evenly dispersed among PECT nanoparticles to create an alkaline (ALK) environment, synergistically enhancing the antibiofilm effect with higher efficiency and prolonged duration. The antibiofilm effect has been demonstrated in root-canal models and apical periodontitis rats, exhibiting superior performance compared to clinically used Ca(OH)2 paste. This study demonstrates that OCT/PECT@OCT + ALK composite thermosensitive hydrogel is a potential intracanal medicament with excellent antibiofilm effect and clinical operability.

Fast gelling, high performance MXene hydrogels for wearable sensors

Hydrogel-based functional materials had attracted great attention in the fields of artificial intelligence, soft robotics, and motion monitoring. However, the gelation of hydrogels induced by free radical polymerization typically required heating, light exposure, and other conditions, limiting their practical applications and development in real-life scenarios. In this study, a simple and direct method was proposed to achieve rapid gelation at room temperature by incorporating reductive MXene sheets in conjunction with metal ions into the chitosan network and inducing the formation of a polyacrylamide network in an extremely short time (10 s). This resulted in a dual-network MXene-crosslinked conductive hydrogel composite that exhibited exceptional stretchability (1350 %), remarkably low dissipated energy (0.40 kJ m-3 at 100 % strain), high sensitivity (GF = 2.86 at 300-500 % strain), and strong adhesion to various substrate surfaces. The study demonstrated potential applications in the reliable detection of various motions, including repetitive fine movements and large-scale human body motions. This work provided a feasible platform for developing integrated wearable health-monitoring electronic systems.

Nucleobase-Functionalized 7-Deazaisoguanine and 7-Deazapurin-2,6-diamine Nucleosides: Halogenation, Cross-Coupling, and Cycloaddition

The functionalization in position-7 of 7-deazaisoguanine and 7-deazapurin-2,6-diamine ribo- and 2'-deoxyribonucleosides by halogen atoms (chloro, bromo, iodo), and clickable alkynyl and vinyl side chains for copper-catalyzed and copper-free cycloadditions is described. Problems arising during the synthesis of the 7-iodinated isoguanine ribo- and 2'-deoxyribonucleosides were solved by the action of acetone. The impact of side chains and halogen atoms on the pKa values and hydrophobicity of nucleosides was investigated. Halogenated substituents increase the lipophilic character of nucleosides in the order Cl < Br < I and decrease the pK values of protonation. Photophysical properties (fluorescence, solvatochromism, and quantum yields) of azide-alkyne click adducts bearing pyrene as sensor groups were determined. Pyrene fluorescence was solvent-dependent and changed according to the linker lengths. Excimer emission was observed in dioxane for the long linker adduct. Bioorthogonal inverse-electron-demanding Diels-Alder cycloadditions (iEDDA) were conducted on the electron-rich vinyl groups of 7-deazaisoguanine and 7-deazapurin-2,6-diamine nucleosides as dienophiles and 3,6-dipyridyl-1,2,4,5-tetrazine as diene. The initially formed complex reaction mixture of isomers could be easily oxidized with iodine in tetrahydrofuran (THF)/pyridine leading to single aromatic tetrazine adducts within a short time and in excellent yields.

Body temperature-induced adhesive hyaluronate/gelatin-based hybrid hydrogel dressing for promoting skin regeneration

Skin wound management faces significant clinical challenges, including continuous bacterial infection and inflammation. Therefore, developing removable hydrogel dressings with intrinsic multifunctional properties is highly desirable. In this study, a body temperature-induced adhesive and removable hydrogel was designed to treat skin defect wounds. The HA/Gel-R-Ag hybrid gel was prepared by incorporating a silver ion-crosslinked sulfhydryl hyaluronate/gelatin-based polymeric gel network into a supramolecular rhein gel network, thereby significantly enhancing its mechanical properties. Temperature-responsive gelatin chains give the hybrid gel reversible tissue adhesiveness and detachment, thus avoiding secondary injury to wounds when changing the hydrogels. The hybrid gel exhibited excellent bactericidal ability owing to the antibacterial capacity of the silver ions and rhein. Moreover, both HA and rhein endowed the hybrid gel with immunoregulatory effects by promoting macrophage polarization from pro-inflammatory M1 phenotype to anti-inflammatory M2 phenotype. In a full-thickness skin defect mouse mode, this porous, degradable, and biocompatible HA/Gel-R-Ag hybrid gel boosted skin regeneration by inhibiting inflammation and promoting collagen deposition and angiogenesis. It is thus a simple method for widening the application range of mechanically weak rhein gels and providing a promising wound dressing material with multiple intrinsic functions for treating skin wounds.

Unraveling the New Perspectives on Antimicrobial Hydrogels: State-of-the-Art and Translational Applications

The growing impact of infections and the rapid emergence of antibiotic resistance represent a public health concern worldwide. The exponential development in the field of biomaterials and its multiple applications can offer a solution to the problems that derive from these situations. In this sense, antimicrobial hydrogels represent a promising opportunity with multiple translational expectations in the medical management of infectious diseases due to their unique physicochemical and biological properties as well as for drug delivery in specific areas. Hydrogels are three-dimensional cross-linked networks of hydrophilic polymers that can absorb and retain large amounts of water or biological fluids. Moreover, antimicrobial hydrogels (AMH) present good biocompatibility, low toxicity, availability, viscoelasticity, biodegradability, and antimicrobial properties. In the present review, we collect and discuss the most promising strategies in the development of AMH, which are divided into hydrogels with inherent antimicrobial activity and antimicrobial agent-loaded hydrogels based on their composition. Then, we present an overview of the main translational applications: wound healing, tissue engineering and regeneration, drug delivery systems, contact lenses, 3D printing, biosensing, and water purification.