Mussel-inspired double cross-linked hydrogels with desirable mechanical properties, strong tissue-adhesiveness, self-healing properties and antibacterial properties

A Microenvironment-Responsive, Controlled Release Hydrogel Delivering Embelin to Promote Bone Repair of Periodontitis via Anti-Infection and Osteo-Immune Modulation

Periodontitis, a prevalent chronic inflammatory disease, poses significant challenges for effective treatment due to its complex etiology involving specific bacteria and the inflammatory immune microenvironment. Here, this study presents a novel approach for the targeted treatment of periodontitis utilizing the immunomodulatory and antibacterial properties of Embelin, a plant-derived compound, within an injectable hydrogel system. The developed Carboxymethyl Chitosan-Oxidized Dextran (CMCS-OD) hydrogel formed via dynamic chemical bonds exhibited self-healing capabilities and pH-responsive behavior, thereby facilitating the controlled release of Embelin and enhancing its efficacy in a dynamic oral periodontitis microenvironment. This study demonstrates that this hydrogel system effectively prevents bacterial invasion and mitigates excessive immune response activation. Moreover, it precisely modulates macrophage M1/M2 phenotypes and suppresses inflammatory cytokine expression, thereby fostering a conducive environment for bone regeneration and addressing periodontitis-induced bone loss. These findings highlight the potential of the approach as a promising strategy for the clinical management of periodontitis-induced bone destruction.

Recent Advances in Environmentally Friendly Dual-crosslinking Polymer Networks

Environmentally friendly crosslinked polymer networks feature degradable covalent or non-covalent bonds, with many of them manifesting dynamic characteristics. These attributes enable convenient degradation, facile reprocessibility, and self-healing capabilities. However, the inherent instability of these crosslinking bonds often compromises the mechanical properties of polymer networks, limiting their practical applications. In this context, environmentally friendly dual-crosslinking polymer networks (denoted EF-DCPNs) have emerged as promising alternatives to address this challenge. These materials effectively balance the need for high mechanical properties with the ability to degrade, recycle, and/or self-heal. Despite their promising potential, investigations into EF-DCPNs remain in their nascent stages, and several gaps and limitations persist. This Review provides a comprehensive overview of the synthesis, properties, and applications of recent progress in EF-DCPNs. Firstly, synthetic routes to a rich variety of EF-DCPNs possessing two distinct types of dynamic bonds (i.e., imine, disulfide, ester, hydrogen bond, coordination bond, and other bonds) are introduced. Subsequently, complex structure- and dynamic nature-dependent mechanical, thermal, and electrical properties of EF-DCPNs are discussed, followed by their exemplary applications in electronics and biotechnology. Finally, future research directions in this rapidly evolving field are outlined.

Curcumin-loaded mesoporous polydopamine nanoparticles modified by quaternized chitosan against bacterial infection through synergistic effect

Clinically, open wounds caused by accidental trauma and surgical lesion resection are easily infected by external bacteria, hindering wound healing. Antibacterial photodynamic therapy has become a promising treatment strategy for wound infection. In this study, a novel antibacterial nanocomposite material (QMC NPs) was synthesized by curcumin, quaternized chitosan and mesoporous polydopamine nanoparticles. The results showed that 150 μg/mL QMC NPs had good biocompatibility and exerted excellent antibacterial activity against Staphylococcus aureus and Escherichia coli after blue laser irradiation (450 nm, 1 W/cm2). In vivo, QMC NPs effectively treated bacterial infection and accelerated the healing of infected wounds in mice.

Hydrogel transformed from sandcastle-worm-inspired powder for adhering wet adipose surfaces

Normally, hydrogel adhesives do not perform well on adipose matters that are covered with bodily fluids. Besides, the maintenance of high extensibility and self-healing ability in fully swollen state still remains challenging. Based on these concerns, we reported a sandcastle-worm-inspired powder, which was made of tannic acid-functionalized cellulose nanofiber (TA-CNF), polyacrylic acid (PAA) and polyethyleneimine (PEI). The obtained powder can rapidly absorb diverse bodily fluids and transform into a hydrogel, displaying fast (＜3 s), self-strengthening and repeatable wet adhesion to adipose tissues. Due to the dense physically cross-linked network, the formed hydrogel still showed excellent extensibility (∼14 times) and self-healing ability after being immersed in water. Moreover, excellent hemostasis, antibacterial ability and biocompatibility make it suitable for numerous biomedical applications. With combined advantages of powders and hydrogels, such as good adaptability to irregular sites, efficient drug loading capacity and tissue affinity, the sandcastle-worm-inspired powder offers significant promise as tissue adhesive and repair materials. This work may open new avenues for designing high-performance bioadhesives with efficient and robust wet adhesiveness to adipose tissues.

Versatile Hydrogel Dressing with Skin Adaptiveness and Mild Photothermal Antibacterial Activity for Methicillin-Resistant Staphylococcus Aureus-Infected Dynamic Wound Healing

Bacterial infection often induces chronic repair of wound healing owing to aggravated inflammation. Hydrogel dressing exhibiting intrinsic antibacterial activity may substantially reduce the use of antibiotics for infected wound management. Hence, a versatile hydrogel dressing (rGB/QCS/PDA-PAM) exhibiting skin adaptiveness on dynamic wounds and  mild photothermal antibacterial activity is developed for safe and efficient infected wound treatment. Phenylboronic acid-functionalized graphene (rGB) and oxadiazole-decorated quaternary carboxymethyl chitosan (QCS) are incorporated into a polydopamine-polyacrylamide (PDA-PAM) network with multiple covalent and noncovalent bonds, which conferred the hydrogel with flexible mechanical properties, strong tissue adhesion and excellent self-healing ability on the dynamic wounds. Moreover, the glycocalyx-mimicking phenylboronic acid on the surface of rGB enables the hydrogel to specifically capture bacteria. The enhanced membrane permeability of QCS enhanced bacterial vulnerability to photothermal therapy（PTT）, which is demonstrated by efficient mild PTT antibacteria against methicillin-resistant Staphylococcus aureus in vitro and in vivo at temperatures of <49.6 °C. Consequently, the hydrogel demonstrate accelerated tissue regeneration on MRSA-infected wound in vivo, with an intact epidermis, abundant collagen deposition and prominent angiogenesis. Therefore, rGB/QCS/PDA-PAM is a versatile hydrogel dressing exhibiting inherent antibacterial activity and has considerable potential in treating wounds infected with drug-resistant bacteria.

Recent advances in adhesive materials used in the biomedical field: adhesive properties, mechanism, and applications

Adhesive materials are natural or synthetic polymers with the ability to adhere to the surface of luminal mucus or epithelial cells. They are widely used in the biomedical field due to their unique adhesion, biocompatibility, and excellent surface properties. When used in the human body, they can adhere to an accessible target and remain at the focal site for a longer period, improving the therapeutic effect on local disease. An adhesive material with bacteriostatic properties can play an antibacterial role at the focal site and the adhesive properties of the material can prevent the focal site from being infected by bacteria for a period. In addition, some adhesive materials can promote cell growth and tissue repair. In this review, the properties and mechanism of natural adhesive materials, organic adhesive materials, composite adhesive materials, and underwater adhesive materials have been introduced systematically. The applications of these adhesive materials in drug delivery, antibacterials, tissue repair, and other applications are described in detail. Finally, we have discussed the prospects and challenges of using adhesive materials in the field of biomedicine.

Construction of an antibacterial hydrogel based on diammonium glycyrrhizinate and gallic acid for bacterial- infected wound healing

The current antibacterial wound dressings with antibiotic substances or metal bactericidal agents may lead to severe multidrug resistance and poor biocompatibilities. Herein, we report an inherent antibacterial hydrogel constructed by only two naturally small molecules gallic acid (GA) and diammonium glycyrrhizinate (DG) for promoting Staphylococcus aureus (S. aureus)-infected wound healing. The resultant GAD hydrogel can be fabricated by co-assembly of these two materials through simple steps. Thanks to the incorporation of GA and DG, GAD hydrogel enabled a strong mechanical performance and great self-healing property with a sustained-release of drugs into skin wounds. Moreover, the cell viability assays showed that GAD hydrogel had good cytocompatibility by promoting cell proliferation and migration. In addition, GAD hydrogel had broad antibacterial efficiency against both Gram-positive and Gram-negative bacteria. Taken together, GAD hydrogel is a promising dressing to accelerate bacterial-infected wound healing through reconstructing an intact and thick epidermis without antibiotics or cytokines.

Temperature/pH-Sensitive Double Cross-Linked Hydrogels as Platform for Controlled Delivery of Metoclopramide

Novel double cross-linked (DC) hydrogels with pH-/temperature-sensitive properties were designed and developed. Therefore, linear pH-sensitive poly(methyl vinyl ether-alt-maleic acid) (P(VME/MA)) macromolecules were absorbed within a thermosensitive poly(N-isopropylacrylamide-co-hydroxyethylacrylamide)-hydrogel (PNH) and, subsequently, cross-linked together through a solvent-free thermal method. As a novelty, double cross-linked hydrogels were obtained from previously purified polymers in the absence of any solvent or cross-linking agent, which are generally harmful for the body. The new DC structures were characterized by FT-IR spectroscopy, SEM, swelling kinetic measurements, and mechanical tests. The resulting scaffolds exhibited interconnected pores and a flexible pattern, compared to the brittle structure of conventional PNH. The swelling kinetics of DC hydrogels were deeply affected by temperature (25 and 37 °C) and pH (7.4 and 1.2). Furthermore, the hydrogels absorbed a great amount of water in a basic environment and displayed improved mechanical properties. Metoclopramide (Met) was loaded within DC hydrogels as a model drug to investigate the ability of the support to control the drug release rate. The results obtained recommended them as convenient platforms for the oral administration of drugs, with the release of the largest part of the active principle occurring in the colon.

Design strategies for adhesive hydrogels with natural antibacterial agents as wound dressings: Status and trends

The wound healing process is usually susceptible to different bacterial infections due to the complex physiological environment, which significantly impairs wound healing. The topical application of antibiotics is not desirable for wound healing because the excessive use of antibiotics might cause bacteria to develop resistance and even the production of super bacteria, posing significant harm to human well-being. Wound dressings based on adhesive, biocompatible, and multi-functional hydrogels with natural antibacterial agents have been widely recognized as effective wound treatments. Hydrogels, which are three-dimensional (3D) polymer networks cross-linked through physical interactions or covalent bonds, are promising for topical antibacterial applications because of their excellent adhesion, antibacterial properties, and biocompatibility. To further improve the healing performance of hydrogels, various modification methods have been developed with superior biocompatibility, antibacterial activity, mechanical properties, and wound repair capabilities. This review summarizes hundreds of typical studies on various ingredients, preparation methods, antibacterial mechanisms, and internal antibacterial factors to understand adhesive hydrogels with natural antibacterial agents for wound dressings. Additionally, we provide prospects for adhesive and antibacterial hydrogels in biomedical applications and clinical research.

Well-Distributed Polysilsesquioxane-Modified Carbon Nanotubes for Thermal Conductive Insulating Silicone Rubbers

Despite carbon nanotubes (CNTs) have garnered tremendous research interests for enhancing the electrical and thermal conductivity of polymers, it is still a considerable challenge to achieve the uniform dispersion of carbon nanotubes in polymer matrix. Herein, inspired by the mussel-inspired chemistry, we adopted the strategy of coating CNTs with polydopamine. And the polysilsesquioxane-modified CNTs (CNTs-PSQ) were obtained based on the click chemistry reaction. The FT-IR, Raman, XRD, and TGA collectively demonstrated the successful modification of PSQ on the surface of CNTs. The incorporation of PSQ could significantly improve the dispersion of CNTs in the silicon rubbers, and a strong interfacial interaction was formed between CNTs-PSQ and silicon rubber matrix, as observed from TEM images of silicon rubber/CNTs-PSQ nanocomposites. Meanwhile, compared with the nanocomposites with neat CNTs, the ones with CNTs-PSQ exhibited simultaneously improved electrical conductivity and insulating performance. This strategy proposed for the preparation of PSQ-modified CNTs provides insights toward highly insulating and thermal conducting polymers.

Precisely controlled polydopamine-mediated antibacterial system: mathematical model of polymerization, prediction of antibacterial capacity, and promotion of wound healing

In this work, the polydopamine (PDA)-mediated antibacterial system is synthesized to carry out antimicrobial activities in vitro and in vivo. First, to precisely control the surface modification of nanodiamonds (NDs), a mathematical kinetics model of PDA deposition is established, and the conditions of synthesis reaction are discussed including influencing factors such as the concentrations of dopamine, reaction time, and the kinetic constant k1, which is a function of several variables associated with the reaction temperature, light irradiance (especially at ultraviolet wavelengths), pH value and concentration of dissolved O2 in the solution. A simulated visualization demonstrates that the deposition thickness of PDA is positively correlated with temperature and light irradiance, and PDA is easier to deposit in an alkaline solution and will be terminated if the dissolved O2 is insufficient. Then, the precisely controlled thickness of PDA can control the growth of AgNPs, rendering the intensity of Raman peaks increased and providing a predictable antibacterial effect against E. coli in vitro. An optimized antibacterial hydrogel containing NDs-PDA/Ag is prepared and characterized by the Fourier transform infrared spectroscopy and field emission scanning electron microscopy. Finally, the antibacterial experiments to promote wound healing in vivo are performed, which are verified by pathological and immunohistochemical-stained sections. This work provides a theoretical basis of predicting the PDA-assisted surface modification of NDs, giving a divinable antibacterial effect, and promoting wounds healing in vivo.

Ultrafast gelation of multifunctional hydrogel/composite based on self-catalytic Fe3+/Tannic acid-cellulose nanofibers

Multifunctional hydrogels with transparency, ultraviolet (UV)-blocking, stretchable, self-healing, adhesive, antioxidant and antibacterial properties are promising materials for biomedical and relevant applications. However, preparation of these hydrogels at ambient environment without stimuli is still a challenge. Here, a series of hydrogels possessing ultrashort gelation time (~30 s) at room or cold temperature were fabricated based on self-catalytic Fe³⁺/Tannic acid-cellulose nanofiber (Fe³⁺/TA-CNF). Fe³⁺/TA-CNF formed stable redox pairs to activate ammonium persulfate (initiator), generating abundant free radicals to trigger the ultrafast polymerization of acrylic acid (AA). To improve the antibacterial ability of hydrogel, a bilayer hydrogel composite (NF@HG) composed of tetracycline hydrochloride (TH)-loaded electrospun nanofibers and hydrogel layer was fabricated via a mild casting method. The NF@HG exhibited enhanced antibacterial ability and the sustained release of TH can provide long-term antibacterial activity. Besides, cell viability results demonstrated that NF@HG was non-cytotoxic. Taken together, this strategy based on self-catalytic Fe³⁺/TA-CNF system may inspire new aspects on fast and economical preparation of multifunctional hydrogels or composites, which have attractive industrial applications for biomedical materials.

Nature-Inspired Hydrogel Network for Efficient Tissue-Specific Underwater Adhesive

Underwater adhesives with efficient, selective, and repeatable adhesion are urgently needed for biomedical applications. Catechol-containing hydrogel adhesives have aroused much interest, but the design of specific underwater adhesives to biotic surfaces is still a challenge. Here we report a facile way that recapitulates the adhesion mechanism of mussel and sea gooseberry for the development of robust and specific hydrogel adhesives. With an exquisite design of chemical bonding, catechol chemistry, and electrostatic interaction, the hydrogel consisting of poly(acrylic acid) grafted with N-hydroxysuccinimide ester (PAA-NHS ester), tea polyphenol (TP), chitosan (CS), and Al³⁺ exhibited fast, specific, and repeatable underwater adhesion to various biological tissues, such as porcine skin, intestine, liver, and shrimp. Furthermore, nanofibers-hydrogel composite (NF-HG) was prepared via the wicking effect of curcumin-loaded electrospun nanofibers. The NF-HG exhibited pH-responsive color changing properties, sustained drug release, and good cell viability, which made it suitable as a novel wound healing material. This strategy may provide great inspiration for designing multifunctional specific underwater adhesives.

A Sequential Therapeutic Hydrogel With Injectability and Antibacterial Activity for Deep Burn Wounds' Cleaning and Healing

As a severe clinical challenge, escharotomy and infection are always the core concerns of deep burn injuries. However, a usual dressing without multifunctionality leads to intractable treatment on deep burn wounds. Herein, we fabricated a sequential therapeutic hydrogel to solve this problem. Cross-linked by modified polyvinyl alcohol (PVA-SH/ε-PL) and benzaldehyde-terminated F127 triblock copolymers (PF127-CHO), the hydrogel demonstrated excellent mechanical properties, injectability, tissue adhesiveness, antibacterial activity, biocompatibility, and satisfactory wound cleaning through both in vitro and in vivo assays. Additionally, based on the conception of “sequential therapy,” we proposed for the first time to load bromelain and EGF into the same hydrogel in stages for wound cleaning and healing. This work provides a strategy to fabricate a promising wound dressing for the treatment of deep burn wounds with injectability and improved patients’ compliance as it simplified the process of treatment due to its “three in one” characteristic (antibacterial activity, wound cleaning, and healing effects); therefore, it has great potential in wound dressing development and clinical application.