Injectable photosensitizing supramolecular hydrogels: A robust physically cross-linked system based on polyvinyl alcohol/chitosan/tannic acid with self-healing and antioxidant properties

Borax - and tannic acid-based post-3D-printing treatment to tune the mechanical properties of scaffolds

Digital light processing (DLP) methods are constrained by the narrow range of cell-compatible resins, limiting their use in biomedical applications that require varied mechanical and biofunctional properties. Current bioresins based on natural polymers such as methacrylated gelatine or alginate usually lack sufficient stretchability and toughness. In this study, we propose a post-processing strategy to tune the mechanical and functional properties of a DLP printable polyethylene glycol diacrylate (PEGDA)/polyvinyl alcohol (PVA) resin via simple treatment with 5% (w/v) tannic acid (TA) or borax (B). The TA treatment reduced the resin's toughness by ∼17% and compressive modulus by ∼16%, while B treatment increased the toughness by ∼53% and the compressive modulus by ∼44% compared with non-treated hydrogels. TA-treated hydrogels continuously released over 59% of the loaded TA, demonstrating antibacterial and radical scavenging activities. Moreover, TA-treated hydrogels, DLP-printed in a tubular shape, demonstrated the highest durability, remaining intact for ∼32 cycles before failure, which was ∼17 cycles more than that for the non-treated hydrogels. Our in vivo larval model further confirmed the hydrogels' biocompatibility. This study offers a practical approach for post-fabrication tuning of the mechanical and bioactive properties of DLP-printed PEGDA-PVA hydrogels, expanding the utility of existing resins for potential biomedical applications, such as soft tissue engineering.

Tri-network PVA/chitosan/gelatin hydrogel modified by tannic acid with self-healing, adhesive and anti-inflammatory properties to accelerate wound healing

Wound inflammation is a key issue in wound healing as it often causes serious complications and delays wound healing. In this study, hemostatic and antimicrobial hydrogels composed of polyvinyl alcohol (PVA), chitosan (CS) and gelatin (Gel) were prepared. Phenylboronic acid (3-CPBA) and tannic acid (TA) were introduced to modify the multinetwork hydrogel to promote wound repair. PGCPT-1.2 hydrogel had a water content of >85 % and was biocompatible. Due to the antibacterial effect of chitosan itself. The PGCPT hydrogel exhibited 100 % antimicrobial activity against both Escherichia coli and Staphylococcus aureus within 12 h. The hydrogel exhibited shape memory behavior and self-healing ability. Histological analysis showed that PGCPT-1.2 hydrogel reduced tumor necrosis factor-α (TNF-α) levels by accelerating collagen deposition. The wound healing rate at day 14 was 97 % ± 0.4 %. PGCPT-1.2 hydrogel dressing with 1.2 % TA addition had the best effect in promoting wound healing, and it is a promising dressing for promoting wound healing and a therapeutic strategy worth developing.

Recent advances in tannic acid-based gels: Design, properties, and applications

With the flourishing of mussel-inspired chemistry, the fast-growing development for environmentally friendly materials, and the need for inexpensive and biocompatible analogues to PDA in gel design, TA has led to its gradual emergence as a research focus due to its remarkable biocompatible, renewable, sustainable and particular physicochemical properties. As a natural building block, TA can be used as a substrate or crosslinker, ensuring versatile functional polymeric networks for various applications. In this review, the design of TA-based gels is summarized in detail (i.e., different interactions such as: metal coordination, electrostatic, hydrophobic, host-guest, cation-π and π-π stacking interactions, hydrogen bonding and various reactions including: phenol-amine Michael and Schiff base, phenol-thiol Michael addition, phenol-epoxy ring opening reaction, etc.). Subsequently, TA-based gels with a variety of functionalities, including mechanical, adhesion, conductive, self-healing, UV-shielding, anti-swelling, anti-freezing, shape memory, antioxidant, antibacterial, anti-inflammatory and responsive properties are introduced in detail. Then, a summary of recent developments in the use of TA-based gels is provided, including bioelectronics, biomedicine, energy, packaging, water treatment and other fields. Finally, the difficulties that TA-based gels are currently facing are outlined, and an original yet realistic viewpoint is provided in an effort to spur future development.

Functionalized amino acid-based injectable hydrogels for sustained drug delivery

Drug delivery vehicles optimize therapeutic outcomes by enhancing drug efficacy, minimizing side effects, and providing controlled release. Injectable hydrogels supersede conventional ones in the field of drug delivery owing to their less invasive administration and improved targeting. However, they face challenges such as low biodegradability and biocompatibility, potentially compromising their effectiveness. To address these limitations, a modified amino acid-based pH-responsive injectable shear-thinning hydrogel cl-β-CD-g-p(Gly-MA) has been developed as an efficient drug carrier. In the two-step synthetic approaches, first, the well-known amino acid glycine (Gly) is modified to form glycine methacrylate (Gly-MA). Afterward, Gly-MA is chemically crosslinked with β-cyclodextrin (β-CD), an oligosaccharide, using an ethylene glycol dimethacrylate (EGDMA) crosslinker. The presence of these biomaterials as building blocks enhances the biocompatibility, hemocompatibility, and biodegradability of the hydrogel. They also reduce the risk of immunogenicity. The unique property of easy injectability enables minimally invasive administration. This feature also helps prolong drug retention at the target site, further optimizing drug delivery efficiency. Moreover, the pH-responsive feature of the developed cl-β-CD-g-p(Gly-MA) hydrogel ensures controlled drug release in response to the physiological conditions of the target site, enhancing therapeutic efficacy. The study focuses on investigating the in vitro loading and release of diclofenac sodium (DS), a non-steroidal anti-inflammatory drug (NSAID) commonly used to treat arthritic pain and inflammation.

Highly efficient removal of adsorbed cationic dyes by dual-network chitosan-based hydrogel

This research presents the effective preparation of a novel dual network chitosan-based hydrogel (CMAPP) for the adsorption of methylene blue (MB), malachite green (MG), crystalline violet (CV), and basic fuchsin (BF) using the sol-gel method to address the escalating issue of dye pollution. FTIR, XRD, SEM, EDS, XPS, TGA, and zeta potential study examined hydrogel production and physicochemical properties. To ascertain the maximum adsorption capacity, the influences of pH, temperature, initial dye concentration, contact time, and adsorbent dosage on adsorption were systematically analyzed. It was observed that CMAPP demonstrated significant removal efficiencies (97.62%, 96.67%, 98.12%, and 99.32%) for the dyes MB, MG, CV, and BF at a concentration of 500 mg/L under optimal conditions. The findings from the adsorption kinetics and isotherm studies indicated that pseudo-second-order kinetics and the Langmuir model were the most appropriate for characterizing the adsorption process of hydrogels. The thermodynamic findings demonstrated that the adsorption process was exothermic and spontaneous. After five cycles of adsorption, the hydrogel demonstrated a consistent dye removal efficiency of around 80%, indicating commendable recyclability. In the interference studies, CMAPP exhibits superior anti-interference capability against CV and BF, which is advantageous for its practical application. The findings from XPS and FTIR investigations indicate that electrostatic attraction, hydrogen bonding, and n-π interactions are the primary forces between the adsorbent and the dyes. The synthesis of CMAPP offers an innovative approach for the effective elimination of cationic dyes and demonstrates significant potential in the treatment of complicated wastewater.

Multifunctional hydrogel based on polyvinyl alcohol/chitosan/metal polyphenols for facilitating acute and infected wound healing

Bacterial-infected wounds could cause delayed wound healing due to increased inflammation, especially wounds infected by drug-resistant bacteria remain a major clinical problem. However, traditional treatment strategies were gradually losing efficacy, such as the abuse of antibiotics leading to enhanced bacterial resistance. Therefore, there was an urgent need to develop an antibiotic-free multifunctional dressing for bacterially infected wound healing. This study demonstrated the preparation of a multifunctional injectable hydrogel and evaluated its efficacy in treating acute and infected wounds. The hydrogel was prepared by a one-step mixing method, and cross-linked by natural deep eutectic solvent (DES), polyvinyl alcohol (PVA), chitosan (CS), tannic acid (TA), and Cu2+ through non-covalent interactions (hydrogen bonds and metal coordination bonds). PVA/CS/DES/CuTA500 hydrogel has multiple functional properties, including injectability, tissue adhesion, biocompatibility, hemostasis, broad-spectrum antibacterial, anti-inflammatory, and angiogenesis. Most importantly, in the MRSA-infected skin wound model, PVA/CS/DES/CuTA500 hydrogel could ultimately accelerate infected wound healing by killing bacteria, activating M2 polarization, inhibiting inflammation, and promoting angiogenesis. In summary, the PVA/CS/DES/CuTA500 hydrogel showed great potential as a wound dressing for bacterial infected wounds treatment in the clinic.

Chitosan-based self-healing hydrogel dressing for wound healing

Skin has strong self-regenerative capacity, while severe skin defects do not heal without appropriate treatment. Therefore, in order to cover the wound sites and hasten the healing process, wound dressings are required. Hydrogels have emerged as one of the most promising candidates for wound dressings because of their hydrated and porous molecular structure. Chitosan (CS) with biocompatibility, oxygen permeability, hemostatic and antimicrobial properties is beneficial for wound treatment and it can generate self-healing hydrogels through reversible crosslinks, from dynamic covalent bonding, such as Schiff base bonds, boronate esters, and acylhydrazone bonds, to physical interactions like hydrogen bonding, electrostatic interaction, ionic bonding, metal-coordination, host-guest interactions, and hydrophobic interaction. Therefore, various chitosan-based self-healing hydrogel dressings have been prepared in recent years to cope with increasingly complex wound conditions. This review's objective is to provide comprehensive information on the self-healing mechanism of chitosan-based hydrogel wound dressings, discuss their advanced functions including antibacterial, conductive, anti-inflammatory, anti-oxidant, stimulus-responsive, hemostatic/adhesive and controlled release properties, further introduce their applications in the promotion of wound healing in two categories: acute and chronic (infected, burn and diabetic) wounds, and finally discuss the future perspective of chitosan-based self-healing hydrogel dressings for wound healing.

Use of photosensitive molecules in the crosslinking of biopolymers: applications and considerations in biomaterials development

The development of diverse types of biomaterials has significantly contributed to bringing new biomedical strategies to treat clinical conditions. Applications of these biomaterials can range from mechanical support and protection of injured tissues to joint replacement, tissue implants, and drug delivery systems. Among the strategies commonly used to prepare biomaterials, the use of electromagnetic radiation to initiate crosslinking stands out. The predominance of photo-induced polymerization methods relies on a fast, efficient, and straightforward process that can be easily adjusted to clinical needs. This strategy consists of irradiating the components that form the material with photons in the near ultraviolet-visible wavelength range (i.e., ∼310 to 750 nm) in the presence of a photoactive molecule. Upon photon absorption, photosensitive molecules can generate excited species that initiate photopolymerization through different reaction mechanisms. However, this process could promote undesired side reactions depending on the target zone or treatment type (e.g., oxidative stress and modification of biomolecules such as proteins and lipids). This review explores the basic concepts behind the photopolymerization process of ex situ and in situ biomaterials. Particular emphasis was put on the photosensitization initiated by the most employed photosensitizers and the photoreactions that they mediate in aqueous media. Finally, the undesired oxidation reactions at the bio-interface and potential solutions are presented.

Self-Healing Guar Gum-Based Nanocomposite Hydrogel Promotes Infected Wound Healing through Photothermal Antibacterial Therapy

Preventing bacterial infections is a crucial aspect of wound healing. There is an urgent need for multifunctional biomaterials without antibiotics to promote wound healing. In this study, we fabricated a guar gum (GG)-based nanocomposite hydrogel, termed GBTF, which exhibited photothermal antibacterial therapy for infected wound healing. The GBTF hydrogel formed a cross-linked network through dynamic borate/diol interactions between GG and borax, thereby exhibiting simultaneously self-healing, adaptable, and injectable properties. Additionally, tannic acid (TA)/Fe3+ nanocomplexes (NCs) were incorporated into the hydrogel to confer photothermal antibacterial properties. Under the irradiation of an 808 nm near-infrared laser, the TA/Fe3+ NCs in the hydrogel could rapidly generate heat, leading to the disruption of bacterial cell membranes and subsequent bacterial eradication. Furthermore, the hydrogels exhibited good cytocompatibility and hemocompatibility, making them a precandidate for preclinical and clinical applications. Finally, they could significantly promote bacteria-infected wound healing by reducing bacterial viability, accelerating collagen deposition, and promoting epithelial remodeling. Therefore, the multifunctional GBTF hydrogel, which was composed entirely of natural substances including guar gum, borax, and polyphenol/ferric ion NCs, showed great potential for regenerating infected skin wounds in clinical applications.

Antibacterial adhesive based on oxidized tannic acid-chitosan for rapid hemostasis

Currently, bacterial infections and bleeding interfere with wound healing, and multifunctional hydrogels with appropriate blood homeostasis, skin adhesion, and antibacterial activity are desirable. In this study, chitosan-based hydrogels were synthesized using oxidized tannic acid (OTA) and Fe3+ as cross-linkers (CS-OTA-Fe) by forming covalent, non-covalent, and metal coordination bonds between Fe3+ and OTA. Our results demonstrated that CS-OTA-Fe hydrogels showed antibacterial properties against Gram-positive bacteria (Staphylococcus aureus)and Gram-negative bacteria (Escherichia coli), low hemolysis rate (< 2 %), rapid blood clotting ability, in vitro (< 2 min), and in vivo (90 s) in mouse liver bleeding. Additionally, increasing the chitosan concentration from 3 wt% to 4.5 wt% enhanced cross-linking in the network, leading to a significant improvement in the strength (from 106 ± 8 kPa to 168 ± 12 kPa) and compressive modulus (from 50 ± 9 kPa to 102 ± 14 kPa) of hydrogels. Moreover, CS-OTA-Fe hydrogels revealed significant adhesive strength (87 ± 8 kPa) to the cow's skin tissue and cytocompatibility against L929 fibroblasts. Overall, multifunctional CS-OTA-Fe hydrogels with tunable mechanical properties, excellent tissue adhesive, self-healing ability, good cytocompatibility, and fast hemostasis and antibacterial properties could be promising candidates for biomedical applications.

Synthesis and Properties of Injectable Hydrogel for Tissue Filling

Hydrogels with injectability have emerged as the focal point in tissue filling, owing to their unique properties, such as minimal adverse effects, faster recovery, good results, and negligible disruption to daily activities. These hydrogels could attain their injectability through chemical covalent crosslinking, physical crosslinking, or biological crosslinking. These reactions allow for the formation of reversible bonds or delayed gelatinization, ensuring a minimally invasive approach for tissue filling. Injectable hydrogels facilitate tissue augmentation and tissue regeneration by offering slow degradation, mechanical support, and the modulation of biological functions in host cells. This review summarizes the recent advancements in synthetic strategies for injectable hydrogels and introduces their application in tissue filling. Ultimately, we discuss the prospects and prevailing challenges in developing optimal injectable hydrogels for tissue augmentation, aiming to chart a course for future investigations.

The Recent Progress of the Cellulose-Based Antibacterial Hydrogel

Cellulose-based antibacterial hydrogel has good biocompatibility, antibacterial performance, biodegradability, and other characteristics. It can be very compatible with human tissues and degradation, while its good water absorption and moisturizing properties can effectively absorb wound exudates, keep the wound moist, and promote wound healing. In this paper, the structural properties, and physical and chemical cross-linking preparation methods of cellulose-based antibacterial hydrogels were discussed in detail, and the application of cellulose-based hydrogels in the antibacterial field was deeply studied. In general, cellulose-based antibacterial hydrogels, as a new type of biomaterial, have shown good potential in antimicrobial properties and have been widely used. However, there are still some challenges, such as optimizing the preparation process and performance parameters, improving the antibacterial and physical properties, broadening the application range, and evaluating safety. However, with the deepening of research and technological progress, it is believed that cellulose-based antibacterial hydrogels will be applied and developed in more fields in the future.

Supramolecular hydrogels for wound repair and hemostasis

The unique network characteristics and stimuli responsiveness of supramolecular hydrogels have rendered them highly advantageous in the field of wound dressings, showcasing unprecedented potential. However, there are few reports on a comprehensive review of supramolecular hydrogel dressings for wound repair and hemostasis. This review first introduces the major cross-linking methods for supramolecular hydrogels, which includes hydrogen bonding, electrostatic interactions, hydrophobic interactions, host-guest interactions, metal ligand coordination and some other interactions. Then, we review the advanced materials reported in recent years and then summarize the basic principles of each cross-linking method. Next, we classify the network structures of supramolecular hydrogels before outlining their forming process and propose their potential future directions. Furthermore, we also discuss the raw materials, structural design principles, and material characteristics used to achieve the advanced functions of supramolecular hydrogels, such as antibacterial function, tissue adhesion, substance delivery, anti-inflammatory and antioxidant functions, cell behavior regulation, angiogenesis promotion, hemostasis and other innovative functions in recent years. Finally, the existing problems as well as future development directions of the cross-linking strategy, network design, and functions in wound repair and hemostasis of supramolecular hydrogels are discussed. This review is proposed to stimulate further exploration of supramolecular hydrogels on wound repair and hemostasis by researchers in the future.

Advances in injectable hydrogel: Design, functional regulation, and biomedical applications

Recently, injectable hydrogels have been considered smart materials and have been widely researched for their use as scaffolds. They resemble the extracellular matrix of native tissue and have the capability for homogeneous mixing with therapeutic agents. It can be implanted into living bodies with minimal invasiveness and usability for irregularly shaped sites. Such unique features make the injectable hydrogels as promising materials in tissue engineering, drug delivery system, and gene/protein delivery. This review article provides a comprehensive overview of the different mechanisms employed in the preparation of injectable hydrogel, as well as a detailed exploration of its applications in the biomedical field. Furthermore, the article highlights the critical importance of developing injectable hydrogels as market‐viable products, highlighting their potential impact in the field of regenerative medicine.

Controllable Preparation and Research Progress of Photosensitive Antibacterial Complex Hydrogels

Hydrogels are materials consisting of a network of hydrophilic polymers. Due to their good biocompatibility and hydrophilicity, they are widely used in biomedicine, food safety, environmental protection, agriculture, and other fields. This paper summarizes the typical complex materials of photocatalysts, photosensitizers, and hydrogels, as week as their antibacterial activities and the basic mechanisms of photothermal and photodynamic effects. In addition, the application of hydrogel-based photoresponsive materials in microbial inactivation is discussed, including the challenges faced in their application. The advantages of photosensitive antibacterial complex hydrogels are highlighted, and their application and research progress in various fields are introduced in detail.

Evaluation of singlet oxygen generators of novel water-soluble perylene diimide photosensitizers

In this study, novel photosensitizers using three water-soluble green perylene diimide (PDI)-based ligands were synthesized, which can be used as photosensitizing drugs in photodynamic cancer therapy (PDT). These three efficient singlet oxygen generators were prepared via reactions of three newly designed molecules, namely 1,7-di-3-morpholine propylamine-N,N'-(l-valine-t-butylester)-3,4:9,10-perylyne diimide, 1,7-dimorpholine-N,N'-(O-t-butyl-l-serine-t-butylester)-3,4:9,10-perylene diimide and 1,7-dimorpholine-N,N'-(l-alanine t-butylester)-3,4:9,10-perylene diimide. Although there have been numerous photosensitizers, most of them have a limited useable range of solvent conditions or low photostability. These sensitizers have demonstrated strong absorption and red-light excitation. The singlet oxygen production of the newly synthesized compounds was investigated using a chemical method with 1,3-diphenyl-iso-benzofuran as a trap molecule. In addition, they do not have any dark toxicity at the active concentrations. Owing to these remarkable properties, we demonstrate the singlet oxygen generation of these novel water-soluble green perylene diimide (PDI) photosensitizers with substituent groups at the 1 and 7 positions of the PDI material, which are promising for PDT.

Recent advances in engineered polymeric materials for efficient photodynamic inactivation of bacterial pathogens

Nowadays, infectious diseases persist as a global crisis by causing significant destruction to public health and the economic stability of countries worldwide. Especially bacterial infections remain a most severe concern due to the prevalence and emergence of multi-drug resistance (MDR) and limitations with existing therapeutic options. Antibacterial photodynamic therapy (APDT) is a potential therapeutic modality that involves the systematic administration of photosensitizers (PSs), light, and molecular oxygen (O₂) for coping with bacterial infections. Although the existing porphyrin and non-porphyrin PSs were effective in APDT, the poor solubility, limited efficacy against Gram-negative bacteria, and non-specific distribution hinder their clinical applications. Accordingly, to promote the efficiency of conventional PSs, various polymer-driven modification and functionalization strategies have been adopted to engineer multifunctional hybrid phototherapeutics. This review assesses recent advancements and state-of-the-art research in polymer-PSs hybrid materials developed for APDT applications. Further, the key research findings of the following aspects are considered in-depth with constructive discussions: i) PSs-integrated/functionalized polymeric composites through various molecular interactions; ii) PSs-deposited coatings on different substrates and devices to eliminate healthcare-associated infections; and iii) PSs-embedded films, scaffolds, and hydrogels for regenerative medicine applications.

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Synthetic strategies of engineered polymer-based hybrid materials integrated with photosensitizers for APDT.

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Utilization of photosensitizer-incorporated polymeric materials in health care applications.

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Challenges and opportunities in the future development of polymeric biomaterials with improved photo-bactericidal properties.

Highly stretchable, self-healing, and degradable ionic conductive cellulose hydrogel for human motion monitoring

Self-healing biomass-based conductive hydrogels are applied as flexible strain sensors for wearable devices and human movement monitoring. Cellulose is the most abundant biomass-based materials and exhibits excellent toughness, dispersion and degradability. In this paper, nanocellulose crystals (NCCs) prepared from sisal, used as reinforcing fillers were coated with tannic acid (TA) to prepare inexpensive bio-nanocomposite hydrogels that also included polyvinyl alcohol, okra polysaccharide (OP), and borax. These hydrogels exhibit excellent self-healing and mechanical properties with the maximum elongation, toughness, and self-healing efficiency (9 min) of 1426.2 %, 264.4 kJ/m³, and 62.1 %, respectively. A fabricated hydrogel strain sensor was successfully used to detect and monitor various human movements such as wrist bending, elbow bending, and slight changes in facial expression. In addition, this sensor possessed excellent durability and good working stability after repeated circulation. The nanocomposite hydrogel synthesized in this work utilized natural polysaccharide to manufacture flexible functional materials with good application prospects in the field of flexible sensors.

A Porous Hydrogel with High Mechanical Strength and Biocompatibility for Bone Tissue Engineering

Polyvinyl alcohol (PVA) hydrogels are considered to be ideal materials for tissue engineering due to their high water content, low frictional behavior, and good biocompatibility. However, their limited mechanical properties restrict them from being applied when repairing load-bearing tissue. Inspired by the composition of mussels, we fabricated polyvinyl alcohol/hydroxyapatite/tannic acid (PVA/HA/TA) hydrogels through a facile freeze–thawing method. The resulting composite hydrogels exhibited high moisture content, porous structures, and good mechanical properties. The compressive strength and tensile strength of PVA hydrogels were improved from 0.77 ± 0.11 MPa and 0.08 ± 0.01 MPa to approximately 3.69 ± 0.41 MPa and 0.43 ± 0.01 MPa, respectively, for the PVA/HA/1.5TA hydrogel. The toughness and the compressive elastic modulus of PVA/HA/1.5TA hydrogel also attained 0.86 ± 0.02 MJm⁻³ and 0.11 ± 0.02 MPa, which was approximately 11 times and 5 times higher than the PVA hydrogel, respectively. The PVA/HA/1.5TA hydrogel also exhibited fatigue resistance abilities. The mechanical properties of the composite hydrogels were improved through the introduction of TA. Furthermore, in vitro PVA/HA/1.5TA hydrogel showed excellent cytocompatibility by promoting cell proliferation in vitro. Scanning electron microscopy analysis indicated that PVA/HA/1.5TA hydrogels provided favorable circumstances for cell adhesion. The aforementioned results also indicate that the composite hydrogels had potential applications in bone tissue engineering, and this study provides a facile method to improve the mechanical properties of PVA hydrogel.