An Injectable Self-Assembling Collagen-Gold Hybrid Hydrogel for Combinatorial Antitumor Photothermal/Photodynamic Therapy

Recent advances of injectable in situ-forming hydrogels for preventing postoperative tumor recurrence

The unavoidable residual tumor tissue from surgery and the strong aggressiveness of tumor cells pose challenges to the postoperative treatment of tumor patients, accompanied by in situ tumor recurrence and decreased quality of life. Therefore, there is an urgent need to explore appropriate postoperative therapeutic strategies to remove residual tumor cells after surgery to inhibit tumor recurrence and metastasis after surgery. In recent years, with the rapid development of biomedical materials, the study of local delivery systems as postoperative delivery of therapeutic agents has gradually attracted the attention of researchers. Injectable in situ-forming hydrogel is a locally administered agent injected in situ as a solution that can be loaded with various therapeutic agents and rapidly gels to form a semi-solid gel at the treatment site. This type of hydrogel tightly fills the surgical site and covers irregular excision surfaces. In this paper, we review the recent advances in the application of injectable in situ-forming hydrogels in postoperative therapy, focusing on the matrix materials of this type of hydrogel and its application in the postoperative treatment of different types of tumors, as well as discussing the challenges and prospects of its clinical application.

Cross-linker engineered poly(hydroxyethyl methacrylate) hydrogel allows photodynamic and photothermal therapies and controlled drug release

Here, we disclose the synthesis of poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels incorporating a squaraine dye (Sq) as a chemical crosslinker, viz. Sq@PHEMA. Photothermal and photodynamic features of Sq@PHEMA hydrogels are evaluated in detail. It is noteworthy that Sq@PHEMA induces hyperthermia upon irradiation with an 808 nm laser. Furthermore, Sq@PHEMA enables the generation of reactive oxygen species (ROS) upon irradiation with red light. To our delight, Sq@PHEMA hydrogels can be used as efficient dual photosensitizers pertinent to both PDT and PTT simultaneously. Finally, the hydrogels are loaded with methotrexate (MTX) to investigate controlled drug release behavior. It is noted that Sq@PHEMA hydrogels are promising candidates as drug delivery systems since on-demand MTX release is feasible upon irradiation. In summary, we effectively demonstrate that hydrogel cross-linker engineering allows for synergistic photodynamic and photothermal therapy. Furthermore, drug delivery is also feasible with the Sq@PHEMA core.

Synergistic Regulation of Targeted Organelles in Tumor Cells to Promote Photothermal-Immunotherapy Using Intelligent Core-Satellite-Like Nanoparticles for Effective Treatment of Breast Cancer

The normal operation of organelles is critical for tumor growth and metastasis. Herein, an intelligent nanoplatform (BMAEF) is fabricated to perform on-demand destruction of mitochondria and golgi apparatus, which also generates the enhanced photothermal-immunotherapy, resulting in the effective inhibition of primary and metastasis tumor. The BMAEF has a core of mesoporous silica nanoparticles loaded with brefeldin A (BM), which is connected to ethylenebis(oxyethylenenitrilo)tetraacetic acid (EGTA) and folic acid co-modified gold nanoparticles (AEF). During therapy, the BMAEF first accumulates in tumor cells via folic acid-induced targeting. Subsequently, the schiff base/ester bond cleaves in lysosome to release brefeldin A and AEF with exposed EGTA. The EGTA further captures Ca2+ to block ion transfer among mitochondria, endoplasmic reticulum, and golgi apparatus, which not only induced dysfunction of mitochondria and golgi apparatus assisted by brefeldin A to suppress both energy and material metabolism against tumor growth and metastasis, but causes AEF aggregation for tumor-specific photothermal therapy and photothermal assisted immunotherapy. Moreover, the dysfunction of these organelles also stops the production of BMI1 and heat shock protein 70 to further enhance the metastasis inhibition and photothermal therapy, which meanwhile triggers the escape of cytochrome C to cytoplasm, leading to additional apoptosis of tumor cells.

A self-healing thermogelling polymer with tunable transparency based on biomolecule alginate grafting phenylboronic acid

Thermogelling polymers with transparency, structure stability and biocompatibility are promising for biomedicine application. In this study, a thermogelling polymer P-C5PEG with tunable transparency was developed by the reaction between alternating copolymer C5PEG and chemically modified biomolecule Alg-PBA via boronic ester bonds. The sol-to-gel transition of P-C5PEG aqueous solution sensitively responded to changes in temperature, and the critical value could be adjusted between 15 and 40 °C by varying the content of C5PEG and Alg-PBA. As the weight ratio of Alg-PBA to C5PEG was over 0.3, the transparency of as-synthesized hydrogel kept above 75 % at 37 °C. Meanwhile, immersion P-C5PEG hydrogel in CaCl2 solution significantly increased its mechanical strength by 3 times due to chelation effect. The shear-resistance and self-healing properties were ensured by dynamic boronic ester bonds due to the protective effect of hydrophobic gel network. As a drug delivery, P-C5PEG hydrogel had a swelling rate of 3748.7 ± 103 % in PBS and could continuously release fluorescein sodium within 24 h. Moreover, the in vitro degradability and cytotoxicity of P-C5PEG was confirmed. Finally, the mechanisms behind the thermogelling property and tunable transparency were revealed. Overall, this thermogelling P-C5PEG polymer, with tunable transparency and thermo-responsiveness, exhibits great potential for biomedicine application.

Recent Advances in the 3D Printing of Conductive Hydrogels for Sensor Applications: A Review

Conductive hydrogels, known for their flexibility, biocompatibility, and conductivity, have found extensive applications in fields such as healthcare, environmental monitoring, and soft robotics. Recent advancements in 3D printing technologies have transformed the fabrication of conductive hydrogels, creating new opportunities for sensing applications. This review provides a comprehensive overview of the advancements in the fabrication and application of 3D-printed conductive hydrogel sensors. First, the basic principles and fabrication techniques of conductive hydrogels are briefly reviewed. We then explore various 3D printing methods for conductive hydrogels, discussing their respective strengths and limitations. The review also summarizes the applications of 3D-printed conductive hydrogel-based sensors. In addition, perspectives on 3D-printed conductive hydrogel sensors are highlighted. This review aims to equip researchers and engineers with insights into the current landscape of 3D-printed conductive hydrogel sensors and to inspire future innovations in this promising field.

Hydrogel for light delivery in biomedical applications

Traditional optical waveguides or mediums are often silica-based materials, but their applications in biomedicine and healthcare are limited due to the poor biocompatibility and unsuitable mechanical properties. In term of the applications in human body, a biocompatible hydrogel system with excellent optical transparency and mechanical flexibility could be beneficial. In this review, we explore the different designs of hydrogel-based optical waveguides derived from natural and synthetic sources. We highlighted key developments such as light emitting contact lenses, implantable optical fibres, biosensing systems, luminating and fluorescent materials. Finally, we expand further on the challenges and perspectives for hydrogel waveguides to achieve clinical applications.

A Transparent and Injectable Biomaterial Prepared by Mixing Collagen and Anti-Cancer Platinum Derivatives

This study presents the synthesis of a cross-linked collagen material, named platinum-containing collagen gel (PCG), which is achieved by simply mixing collagen and derivatives of an anti-cancer platinum complex. The cross-linking reagents are derivatives of cisplatin or transplatin, generated through a ligand exchange with dimethyl sulfoxide. PCG exhibits superior physical strength and transparency compared with the native collagen gel formed through spontaneous fibril formation. The versatility of PCG as a cell culture scaffold, applicable to both 2D and 3D models, with low cytotoxicity is demonstrated. Furthermore, PCG exhibits pH-responsive gel-forming properties. This enables the removal of free cross-linker by dialysis in an acidic solution and subsequent gel formation upon neutralization. This material holds promise for application in cell culture scaffolds and medical injections.

Photoactivated Formation of an Extravascular Dynamic Hydrogel as an Intelligent Blood Flow Regulator to Reprogram the Immunogenic Landscape

Long-term tumor starvation may be a potential strategy to elevate the antitumor immune response by depriving nutrients. However, combining long-term starvation therapy with immunotherapy often yields limited efficacy due to the blockage of immune cell migration pathways. Herein, an intelligent blood flow regulator (BFR) is first established through photoactivated in situ formation of the extravascular dynamic hydrogel to compress blood vessels, which can induce long-term tumor starvation to elicit metabolic stress in tumor cells without affecting immune cell migration pathways. By leveraging methacrylate-modified nanophotosensitizers (HMMAN) and biodegradable gelatin methacrylate (GelMA), the developed extravascular hydrogel dynamically regulates blood flow via enzymatic degradation. Additionally, aPD-L1 loaded into HMMAN continuously blocks immune checkpoints. Systematic in vivo experiments demonstrate that the combination of immune checkpoint blockade (ICB) and BFR-induced metabolic stress (BIMS) significantly delays the progression of Lewis lung and breast cancers by reshaping the tumor immunogenic landscape and enhancing antitumor immune responses.

Imageable Brachytherapy with Chelator-Free Radiolabeling Hydrogel

Brachytherapy stands as an essential clinical approach for combating locally advanced tumors. Here, an injectable brachytherapy hydrogel is developed for the treatment of both local and metastatic tumor. Fe-tannins nanoparticles are efficiently and stably radiolabeled with clinical used therapeutic radionuclides (such as 131I, 90Y, 177Lu, and 225Ac) without a chelator, and then chemically cross-linked with 4-armPEG-SH to form brachytherapy hydrogel. Upon intratumoral administration, magnetic resonance imaging (MRI) signal from ferric ions embedded within the hydrogel directly correlates with the retention dosage of radionuclides, which can real-time monitor radionuclides emitting short-range rays in vivo without penetration limitation during brachytherapy. The hydrogel's design ensures the long-term tumor retention of therapeutic radionuclides, leading to the effective eradication of local tumor. Furthermore, the radiolabeled hydrogel is integrated with an adjuvant to synergize with immune checkpoint blocking therapy, thereby activating potent anti-tumor immune responses and inhibiting metastatic tumor growth. Therefore, this work presents an imageable brachytherapy hydrogel for real-time monitoring therapeutic process, and expands the indications of brachytherapy from treatment of localized tumors to metastatic tumors.

Self-Assembling Triple-Helix Recombinant Collagen Hydrogel Enriched with Tyrosine

The self-assembly of collagen within the human body creates a complex 3D fibrous network, providing structural integrity and mechanical strength to connective tissues. Recombinant collagen plays a pivotal role in the realm of biomimetic natural collagen. However, almost all of the reported recombinant collagens lack the capability of self-assembly, severely hindering their application in tissue engineering and regenerative medicine. Herein, we have for the first time constructed a series of self-assembling tyrosine-rich triple helix recombinant collagens, mimicking the structure and functionality of natural collagen. The recombinant collagen consists of a central triple-helical domain characterized by the (Gly-Xaa-Yaa)n sequence, along with N-terminal and C-terminal domains featuring the GYY sequence. The introduction of GYY has a negligible impact on the stability of the triple-helical structure of recombinant collagen while simultaneously promoting its self-assembly into fibers. In the presence of [Ru(bpy)3]Cl2 and APS as catalysts, tyrosine residues in the recombinant collagen undergo covalent cross-linking, resulting in a hydrogel with exceptional mechanical properties. The recombinant collagen hydrogel exhibits outstanding biocompatibility and bioactivity, significantly enhancing the proliferation, adhesion, migration, and differentiation of HFF-1 cells. This innovative self-assembled triple-helix recombinant collagen demonstrates significant potential in the fields of tissue engineering and medical materials.

Collagen/chitosan/genipin hydrogel loaded with phycocyanin nanoparticles and ND-336 for diabetic wound healing

Diabetic wound healing remains a healthcare challenge due to the overexpression of matrix metalloproteinase-9 (MMP-9) and the imbalance between angiogenic factors and vascular inhibitory factors. In this study, we developed a nanocomposite injectable collagen/chitosan hydrogel for the treatment of delayed diabetic wound healing, which can promote cell migration to the wound site (through the addition of phycocyanin) and reduce the expression of MMP-9 (through the use of ND-336) to improve the therapeutic effect of diabetic wound healing. Furthermore, different weight ratios of collagen and chitosan hydrogels were prepared to select the hydrogel with proper mechanical properties. In vitro experiments confirmed that all hydrogels have favorable biocompatibility and hemocompatibility. Notably, Gel 2, with a weight ratio of collagen and chitosan at 25:75, was found to have an excellent capability to facilitate cell migration and in vivo studies further proved that Gel 2 nanocomposite hydrogel had the best ability to improve diabetic wound healing by promoting cell migration and decreasing MMP-9 expression. The collagen/chitosan/genipin hydrogel loaded phycocyanin and ND-336 can be harnessed for non-toxic and efficient treatment of wound healing management of diabetes.

Superior adsorption and removal of industrial dye from aqueous solution via magnetic silver metal-organic framework nanocomposite

The indirect emission had a negative influence on the ecosystem of enormous amounts of harmful dyes into water. Fe3O4@Ag-MOF was successfully fabricated to capture Gentine violet (GV)) as a model example of cationic dye from their aqueous solutions was evaluated in this search as a method to eliminate dyes from water contaminants. FTIR, XPS, BET, TGA, SEM, TEM, and XRD have all been used to study this adsorbent in order to determine its structural and chemical characteristics as well as to interpret its binding mechanisms. According to the results of the characterization, the synthesized composite had a size about 45 nm, a surface area of 856.06 m2/g, and considerable magnetic characteristics (66.2 emug-1). Consequently, we created mesoporous surfaces that had a strong ability to interface and absorb GV dye. It is possible to use the pseudo-second order rate equation to characterize the kinetic profile., while the Langmuir equation fits isotherm models. At pH 9, maximum sorption capacities can reach 1.68 mmol.g-1. Additionally, the investigations of temperature profiles indicated the endothermic process and Thermodynamic parameters were discovered as, ΔG°, ΔH° and ΔS° The synthesized adsorbent had an interestingly high reusability of > 92 percent up to the sixth cycle. These findings revealed that a mixture of electrostatic interactions, π-π stacking, hydrogen bonds, and pore filling were involved in the GV adsorption mechanism. Fe3O4@Ag-MOF was successful in demonstrating its effectiveness as a point-of-use colour collection candidate from actual dyeing effluents.

Construction of self-assembled nano cellulose crystals/chitosan nanobubbles composite hydrogel with improved gallic acid release property

Hydrogels are of great significance in the field of bioactive delivery. This study designed the self-assembly of gallic acid-loaded nano cellulose crystals/chitosan (NC/CS) hydrogels via Nano bubbles (NBs). NC/CS NBs 4:2 hydrogels improved the mechanical properties compared to those without NBs. The hardness of NC/CS (4:2) NBs hydrogels was greatly enhanced by 1.15 ± 0.05. The water-holding and swelling behavior can be tuned at different ratios. NC/CS NBs (4:2) showed the electrostatic interaction analyzed by FTIR, XRD, and XPS. SEM results displayed smoother and smaller pores along dense networks promoted by NBs. The antioxidant activity of hydrogels was increased by adding NBs (P < 0.05). In vitro and vivo release activity of gallic acid was higher in simulated intestinal fluid (SIF) at 4:2, depicting the controlled release mechanism. Thus, current work revealed that NBs and low concentrations of NC can be self-assembled with chitosan chains, producing a highly compact hydrogel structure.

Exudate-Induced Gelatinizable Nanofiber Membrane with High Exudate Absorption and Super Bactericidal Capacity for Bacteria-Infected Wound Management

Invasion of bacteria and continuous oozing of exudate are significant causes of interference with the healing of infected wounds. Therefore, an exudate-induced gelatinizable and near-infrared (NIR)-responsive nanofiber membrane composed of polyvinyl alcohol (PVA), carboxymethyl chitosan (CMC), and Fe-doped phosphomolybdic acid (Fe-PMA) with exceptional exudate absorption capacity and potent bactericidal efficacy is developed and denoted as the PVA-FP-CMC membrane. After absorbing exudate, the fiber membrane can transform into a hydrogel membrane, forming coordination bonds between the Fe-PMA and CMC. The unique exudate-induced gelation process imparts the membrane with high exudate absorption and retention capability, and the formed hydrogel also traps the bacteria that thrive in the exudate. Moreover, it is discovered for the first time that the Fe-PMA exhibits an enhanced photothermal conversion capability and photocatalytic activity compared to the PMA. Therefore, the presence of Fe-PMA provides the membrane with a photothermal and photodynamic therapeutic effect for killing bacteria. The PVA-FP-CMC membrane is proven with a liquid absorption ratio of 520.7%, a light-heat conversion efficiency of 41.9%, high-level generation of hydroxyl radical (•OH) and singlet oxygen (1O2), and a bacterial killing ratio of 100% for S. aureus and 99.6% for E. coli. The treatment of infected wounds on the backs of rats further confirms the promotion of wound healing by the PVA-FP-CMC membrane with NIR irradiation. Overall, this novel functional dressing for the synergistic management of bacteria-infected wounds presents a promising therapeutic strategy for tissue repair and regeneration.

A novel bola-molecular self-assembling hydrogel for enhancing diabetic wound healing

HYPOTHESIS

Chronic wounds, particularly those caused by diabetes, pose a significant challenge for clinical treatment due to their prolonged healing process and associated complications, which can lead to increased morbidity. A biocompatible hydrogel with strong antibacterial properties and the ability to promote angiogenesis can be directly absorbed in the wound site for healing.

EXPERIMENTS

A series of self-healing, antibacterial bolaamphiphilic supramolecular self-assembling hydrogels (HLQMes/Cu) were developed based on metal-ligand coordination between various concentrations of Cu2+ solution and the head group of l-histidine methyl ester in HLQMes. This is the first report on the application of bola-molecular supramolecular hydrogels for the treatment of chronic wounds.

FINDINGS

The bola-molecular hydrogels reduced the toxicity of copper ions by coordination, and the HLQMes/Cu hydrogel, with 1.3 mg/mL Cu2+ (HLQMes/Cu1.3), demonstrated good biocompatibility and antibacterial properties and effectively enhanced wound healing in a diabetic wound model with full-thickness injuries. Immunohistochemical analysis revealed that the HLQMes/Cu1.3 hydrogel enhanced epithelial formation and collagen deposition in wounds. Immunofluorescence studies confirmed that the HLQMes/Cu1.3 hydrogel attenuated the expression of proinflammatory factor (IL-6) and promoted angiogenesis by upregulating α-SMA and CD31. These findings demonstrate the potential of this bolaamphiphilic supramolecular self-assembling hydrogel as a promising candidate for diabetic wound treatment.

Selenium-silk microgels as antifungal and antibacterial agents

Antimicrobial resistance is a leading threat to global health. Alternative therapeutics to combat the rise in drug-resistant strains of bacteria and fungi are thus needed, but the development of new classes of small molecule therapeutics has remained challenging. Here, we explore an orthogonal approach and address this issue by synthesising micro-scale, protein colloidal particles that possess potent antimicrobial properties. We describe an approach for forming silk-based microgels that contain selenium nanoparticles embedded within the protein scaffold. We demonstrate that these materials have both antibacterial and antifungal properties while, crucially, also remaining highly biocompatible with mammalian cell lines. By combing the nanoparticles with silk, the protein microgel is able to fulfill two critical functions; it protects the mammalian cells from the cytotoxic effects of the bare nanoparticles, while simultaneously serving as a carrier for microbial eradication. Furthermore, since the antimicrobial activity originates from physical contact, bacteria and fungi are unlikely to develop resistance to our hybrid biomaterials, which remains a critical issue with current antibiotic and antifungal treatments. Therefore, taken together, these results provide the basis for innovative antimicrobial materials that can target drug-resistant microbial infections.

Injectable hydrogels as promising in situ therapeutic platform for cartilage tissue engineering

Injectable hydrogels are gaining prominence as a biocompatible, minimally invasive, and adaptable platform for cartilage tissue engineering. Commencing with their synthesis, this review accentuates the tailored matrix formulations and cross-linking techniques essential for fostering three-dimensional cell culture and melding with complex tissue structures. Subsequently, it spotlights the hydrogels' enhanced properties, highlighting their augmented functionalities and broadened scope in cartilage tissue repair applications. Furthermore, future perspectives are advocated, urging continuous innovation and exploration to surmount existing challenges and harness the full clinical potential of hydrogels in regenerative medicine. Such advancements are crucial for validating the long-term efficacy and safety of hydrogels, positioning them as a promising direction in regenerative medicine to address cartilage-related ailments.

Preparation and characterization of a novel composite acellular matrix/hyaluronic acid thermosensitive hydrogel for interstitial cystitis/bladder pain syndrome

Bladder mucosa damage that causes harm to the interstitium is a recognized pathogenesis of interstitial cystitis/bladder pain syndrome (IC/BPS). The intravesical instillation of drugs is an important second-line therapy, but it is often necessary to use drugs repeatedly in the clinic because of their short residence time in the bladder cavity, which alters the therapeutic effect. To overcome this drawback, this study developed a novel composite acellular matrix/hyaluronic acid (HA) thermosensitive hydrogel (HA-Gel) using rabbit small intestinal submucosa extracellular matrix (ECM) as the thermosensitive material and HA as the drug component and examined its composition, microstructure, thermodynamic properties, temperature sensitivity, rheological properties, biocompatibility, drug release, hydrogel residue, and bacteriostatic properties. The study showed HA-Gel was liquid at temperatures of 15-37.5°C and solid at 37.5-50°C, its swelling rate decreased with increasing temperature, and its lower critical solution temperature occurred at approximately 37.5°C. This property made the hydrogel liquid at room temperature convenient for intravesical perfusion and turned into a solid about 1 min after entering the body and rising to body temperature to increase its residence time. Subsequent experiments also proved that the gel residue time of HA-Gel in vivo and the drug release time of HA in vivo could reach more than 5 days, which was significantly higher than that of HA alone, and it had good biocompatibility and antibacterial properties. Therefore, this hydrogel possesses the proper characteristics to possibly make it an ideal dosage form for IC/BPS intravesical instillation therapy.

Nanofiber-Reinforced Composite Gel Enabling High Ionic Conductivity and Ultralong Cycle Life for Zn Ion Batteries

Despite the impressive merits of gel electrolytes for aqueous Zn-ion batteries, it remains a significant challenge to design and develop the gel electrolyte with high ionic conductivity, excellent dimensional stability, and long cycle life. Herein, a composite electrolyte (PTP) with thermolastic polyurethane -poly(m-phenylene isophthalamide)  nanofiber-reinforced polyvinyl alcohol gel strategy is proposed for highly reversible Zn plating/stripping. Mechanically robust and ultrathin PTP contains functional groups for building ion migration channels and immobilizing water molecules, which accelerates Zn2+ migration and mitigates water-related side reactions. Thus, the Zn anodes exhibit excellent electrochemical performance involving high cycling stability (6500 h at 5 mA cm-2 , 5 mA h cm-2 ) and achieving an exceptional cumulative capacity of more than 16 000 mA h cm-2 . This enhancement is well maintained when combined with MnO2 cathode. This work provides a reasonable solution for stabilizing Zn anodes and also provides new ideas for the modification of nanofiber-reinforced gel electrolytes.

Dual stimuli-responsive delivery system for self-regulated colon-targeted delivery of poorly water-soluble drugs

Inflammatory bowel disease (IBD) are chronic inflammatory conditions which cause significant patient morbidity. Local drug delivery to the colon can improve treatment efficacy and reduce side effects associated with IBD treatment. Smart drug delivery systems are designed to regulate the release of therapeutic agents at the desired site of action. pH-responsive drug carriers have been previously utilised for improved oral drug delivery beyond stomach harsh conditions. Additionally, the colon possesses a diverse microbiome secreting bioactive molecules e.g., enzymes, that can be exploited for targeted drug delivery. We herein synthesised and characterised a 2-hydroxyethyl methacrylate and methacrylic acid copolymer, crosslinked with an azobenzyl crosslinker, that displayed pH- and enzyme-responsive properties. The swelling and drug release from hydrogel were analysed in pH 1.2, 6.5 and 7.4 buffers, and in the presence of rat caecal matter using metronidazole and mesalamine as model BCS Class I and IV drugs, respectively. Swelling studies displayed pH-responsive swelling behaviour, where swelling was maximum at pH 7.4 and minimum at pH 1.2 (69 % versus 32 %). Consequently, drug release was limited in gastric and small intestinal conditions but increased significantly when exposed to colonic conditions containing caecal matter. This system displays promising capacity for achieving colon-targeted drug delivery with enhanced dissolution of poorly water-soluble drugs for local treatment of IBD and other colon-targeted therapies.

Suppressing ACQ of molecular photosensitizers by distorting the conjugated-plane for enhanced tumor photodynamic therapy

Non-AIE-type molecular photosensitizers (PSs) suffer from the aggregation-caused-quenching (ACQ) effect in an aqueous medium due to the strong hydrophobic and π-π interactions of their conjugated planes, which significantly hinders the enhancement of tumor photodynamic therapy (PDT). So far, some ionic PSs have been reported with good water-solubility, though the ACQ effect can still be induced in a biological environment rich in ions, leading to unsatisfactory in vivo delivery and fluorescence imaging performance. Hence, designing molecular PSs with outstanding anti-ACQ properties in water is highly desirable, but it remains a tough challenge for non-AIE-type fluorophores. Herein, we demonstrated a strategy for the design of porphyrin-type molecular PSs with remarkable solubility and anti-ACQ properties in an aqueous medium, which was assisted by quantum chemical simulations. It was found that cationic branched side chains can induce serious plane distortion in diphenyl porphyrin (DPP), which was not observed for tetraphenyl porphyrin (TPP) with the same side chains. Moreover, the hydrophilicity of the chain spacer is also crucial to the plane distortion for attaining the desired anti-ACQ properties. Compared to ACQ porphyrin, anti-ACQ porphyrin displayed type-I ROS generation in hypoxia and much higher tumor accumulation efficacy by blood circulation, leading to highly efficient in vivo PDT for hypoxic tumors. This study demonstrates the power of sidechain chemistry in tuning the configuration and aggregation behaviors of porphyrins in water, offering a new path to boost the performance of PSs to fulfill the increasing clinical demands on cancer theranostics.

Multifunctional photothermally responsive hydrogel as an effective whole-process management platform to accelerate chronic diabetic wound healing

The management of chronic diabetic wounds is a complex issue that requires wound repair, regulation of inflammatory levels, and intervention to prevent bacterial infection. To address this issue, we developed a multifunctional photothermally responsive hydrogel (PAG-CuS) as an effective platform for managing the entire wound-healing process, including promoting wound healing, providing anti-inflammatory therapy, and performing photothermal sterilization. Constructed through copolymerization of acrylic acid (AA), methacrylic anhydride-modified gelatin (GelMA), and lipoic acid sodium (LAS) coated copper sulfide nanoparticles (CuS@LAS), PAG-CuS possessed a porous three-dimensional structure that promoted cell adhesion and had a substantial water-holding capacity. Additionally, the internal CuS@LAS not only conferred photothermal antibacterial properties to the hydrogel but also served as physical cross-linking agents, thus enhancing its mechanical strength. Under the NIR-induced photothermal effect, the porous hydrogel liberates CuS@LAS, and later CuS@LAS expels LAS via micelle deassembly to eliminate intracellular ROS. This results in the down-regulation of MMP-9 expression, promoting ECM production and facilitating wound healing. Meanwhile, the release of Cu2+ from PAG-CuS could enhance CD31 expression in endothelial cells, promoting microvessel formation, which is crucial for wound healing. In the diabetic wound model of GK rats, the PAG-CuS hydrogel reduced ROS levels, increased microvessel count, improved epithelialization, and enhanced wound healing. Therefore, this versatile photothermal hydrogel has the potential to be applied in sterilization, scavenging free radicals, and promoting angiogenesis, making it an effective and comprehensive solution to manage the challenges of diabetic wounds. STATEMENT OF SIGNIFICANCE: Assessment of functional recovery and timely adjustment of treatment strategy is critical in the management of chronic diabetic wounds. In this work, we prepared PAG-CuS composite hydrogels by integrating in situ reduction, chemical crosslinking, and nanoenhancement techniques. The near-infrared light-induced photothermal effect of PAG-CuS gel rapidly kills bacteria at the lesion site, and the generated heat simultaneously promotes the multilevel release of LAS from the gel, which could regulate the levels of ROS and MMP-9 to promote extracellular matrix formation. In addition, the Cu2+ released from the gel can promote the formation of blood vessels to improve blood oxygenation. Therefore, this project proposes a synergistic solution to realize the whole process of management to accelerate chronic diabetic wound healing.

Titanium dioxide nanoparticles embedded in assembled dipeptide hydrogels for microfluidic photodegradation

Dipeptides can be self-assembled via non-covalent bonds towards functional nanostructures for diverse applications in nanotechnology. Here, we introduce a convenient microfluidics-guided dipeptide design as a platform for photodegradation of contaminants in water. Titanium dioxide (TiO2) nanoparticles (NPs) are chosen as photocatalysts due to their vastly studied properties. By using a well-defined microchannel architecture, the dipeptide N-fluorenylmethoxycarbonyl diphenylalanine (Fmoc-FF) and TiO2 NPs are efficiently mixed leading to a self-assembled Fmoc-FF hydrogel with embedded TiO2. Owing to shear-thinning and rapid self-healing of Fmoc-FF hydrogels, we can transfer and inject Fmoc-FF/TiO2 hydrogels into any other microdevice for specific applications, where these low-molecular-weight-gelator- (LMWG-)based Fmoc-FF hydrogels fill out the microchannel volume. Different morphologies of Fmoc-FF/TiO2 hydrogels are obtained by simple concentration screening of TiO2 NPs and Fmoc-FF. Owing to the density of the three-dimensionally twined Fmoc-FF nanofibers, solutions swelling the dipeptide hydrogel can be exchanged without leaching out TiO2 NPs. By further analysis, our hydrogel-filled flow cell can be employed for continuous-flow photodegradation in water under light irradiation. Especially, compared to the TiO2 NPs suspension, Fmoc-FF/TiO2 hydrogels with relatively low concentrations of TiO2 exhibit enhanced photodegradation capabilities due to better dispersion of nanoparticles. Such strategy provides a versatile platform for embedment of small inorganic catalysts or enzymes for (bio-)chemical conversion of solutes passing through the hydrogel network.

Smart Aqueous Zinc Ion Battery: Operation Principles and Design Strategy

The zinc ion battery (ZIB) as a promising energy storage device has attracted great attention due to its high safety, low cost, high capacity, and the integrated smart functions. Herein, the working principles of smart responses, smart self-charging, smart electrochromic as well as smart integration of the battery are summarized. Thus, this review enables to inspire researchers to design the novel functional battery devices for extending their application prospects. In addition, the critical factors associated with the performance of the smart ZIBs are comprehensively collected and discussed from the viewpoint of the intellectualized design. A profound understanding for correlating the design philosophy in cathode materials and electrolytes with the electrode interface is provided. To address the current challenging issues and the development of smart ZIB systems, a wide variety of emerging strategies regarding the integrated battery system is finally prospected.

Multifunctional hydrogel for synergistic reoxygenation and chemo/photothermal therapy in metastatic breast cancer recurrence and wound infection

Metastatic recurrence and postoperative wound infection are two major challenges for breast cancer patients. In this study, a multifunctional responsive hydrogel system was developed for synergistic reoxygenation and chemo/photothermal therapy in metastatic breast cancer and wound infection. The hydrogel system was obtained by cross-linking Prussian blue-modified N-carboxyethyl chitosan (PBCEC) and oxidized sodium alginate using the amino and aldehyde groups on the polysaccharides, resulting in the formation of responsive dynamic imine bonds. Conditioned stimulation (e.g., acid microenvironment) enabled the controlled swelling of hydrogels as well as subsequent slow release of loaded doxorubicin (DOX). Additionally, this hydrogel system decomposed endogenous reactive oxygen species into oxygen to relieve the hypoxic tumor microenvironment and promote the healing of infected-wounds. Both in vitro and in vivo experiments demonstrated the synergistic reoxygenation and chemo/photothermal effects of the PB/DOX hydrogel system against metastatic breast cancer and its recurrence, as well as postoperative wound infection. Thus, the combination of reoxygenation and chemo/photothermal therapy represents a novel strategy for treating and preventing tumor recurrence and associated wound infection.

Pectin-based double network hydrogels as local depots of celastrol for enhanced antitumor therapy

In this study, A double-network (DN) hydrogel composed of a physical glycyrrhizic acid (GA) network and a chemically crosslinked pectin-based network was fabricated as a local depot of celastrol (CEL) for cancer treatment. The obtained DN hydrogel possessed excellent mechanical performance, flexibility, biocompatibility, biodegradability and self-healing property. Furthermore, the release profile of CEL loaded DN hydrogel maintained a controlled and sustained release of CEL for a prolonged period. Finally, in vivo animal experiments demonstrated that the DN hydrogel could significantly enhance the therapeutic efficiency of CEL in CT-26 tumor-bearing mice upon intratumoral injection while effectively alleviate the toxicity of the CEL. In summary, this injectable pectin-based double network hydrogels are ideal delivery vehicle for tumor therapy.

Marine collagen: Unveiling the blue resource-extraction techniques and multifaceted applications

Marine organisms such as fish and shellfish are composed of compounds with properties and characteristics that have been proven useful in a variety of sectors such as cosmetics, healthcare (wound healing), food industries, and tissue engineering. Collagen extraction from fish waste as a "blue resource" has attracted research attention over the past decade. Around 75 % of fish waste contains a high concentration of collagen. This has driven research in the conversion of these low-cost by-products into valuable products. Collagen extracted by acidic or/and enzymatic methods is gaining a lot of attention today due to its low cost and high yield. Fermentation and enzymatic hydrolysis stand out as one of the most environmentally sustainable and ecologically friendly methods for collagen extraction. Because of its great biocompatibility, excellent bioactivity, and low antigenicity, marine collagen is receiving more attention. Furthermore, collagen-derived peptides may exhibit interesting antioxidant activity, potent antihypertensive activity, and antimicrobial activity against different strains of bacteria. This review focuses on the advancements in extraction and detection methods of marine collagen, both from a technological and legislative standpoint, in addition to exploring its diverse range of application domains.

Substituent alkyl-chain-dependent supramolecular chirality, tunable chiroptical property, and dye adsorption in azobenzene-glutamide-amphiphile based hydrogel

Controlling the supramolecular chirality of a self-assembly system by molecular structure design and external stimuli in aqueous solution is significant but challenging. Here, we design and synthesize several glutamide-azobenzene-based amphiphiles with different length alkyl chains. The amphiphiles can form self-assemblies in aqueous solution and show CD signals. As the number of the alkyl chain of amphiphiles increases, the CD signals of the assemblies can be enhanced. However, the long alkyl chains conversely restrict the isomerization of the azobenzene and the corresponding chiroptical property. Moreover, the alkyl length can determine the nanostructure of the assemblies and exert critical influence on the dye adsorption efficiency. This work exhibits some insights into the tunable chiroptical property of the self-assembly by delicate molecular design and external stimuli, and emphasizes the molecular structure can determine the corresponding application.

In situ photo-crosslinkable hyaluronic acid-based hydrogel embedded with GHK peptide nanofibers for bioactive wound healing

A versatile hydrogel was developed for enhancing bioactive wound healing by introducing the amphiphilic GHK peptide (GHK-C16) into a photo-crosslinkable tyramine-modified hyaluronic acid (HA-Ty). GHK-C16 self-assembled into GHK nanofibers (GHK NF) in HA-Ty solution, which underwent in situ gelation after the wound area was filled with precursor solution. Blue light irradiation (460-490 nm), with riboflavin phosphate as a photoinitiator, was used to trigger crosslinking, which enhanced the stability of the highly degradable hyaluronic acid and enabled sustained release of the nanostructured GHK derivatives. The hydrogels provided a microenvironment that promoted the proliferation of dermal fibroblasts and the activation of cytokines, leading to reduced inflammation and increased collagen expression during wound healing. The complexation of Cu2+ into GHK nanofibers resulted in superior wound healing capabilities compared with non-lipidated GHK peptide with a comparable level of growth factor (EGF). Additionally, nanostructured Cu-GHK improved angiogenesis through vascular endothelial growth factor (VEGF) activation, which exerted a synergistic therapeutic effect. Furthermore, in vivo wound healing experiments revealed that the Cu-GHK NF/HA-Ty hydrogel accelerated wound healing through densely packed remodeled collagen in the dermis and promoting the growth of denser fibroblasts. HA-Ty hydrogels incorporating GHK NF also possessed improved mechanical properties and a faster wound healing rate, making them suitable for advanced bioactive wound healing applications. STATEMENT OF SIGNIFICANCE: By combining photo-crosslinkable tyramine-modified hyaluronic acid with self-assembled Cu-GHK-C16 peptide nanofibers (Cu-GHK NF), the Cu-GHK NF/HA-Ty hydrogel offers remarkable advantages over conventional non-structured Cu-GHK for wound healing. It enhances cell proliferation, migration, and collagen remodeling-critical factors in tissue regeneration. The incorporation of GHK nanofibers complexed with copper ions imparts potent anti-inflammatory effects, promoting cytokine activation and angiogenesis during wound healing. The Cu-GHK NF/hydrogel's unique properties, including in situ photo-crosslinking, ensure high customization and potency in tissue regeneration, providing a cost-effective alternative to growth factors. In vivo experiments further validate its efficacy, demonstrating significant wound closure, collagen remodeling, and increased fibroblast density. Overall, the Cu-GHK NF/HA-Ty hydrogel represents an advanced therapeutic option for wound healing applications.

Thermo-Responsive Hydrogels Coupled with Photothermal Agents for Biomedical Applications

Intelligent hydrogels are materials with abilities to change their chemical nature or physical structure in response to external stimuli showing promising potential in multitudinous applications. Especially, photo-thermo coupled responsive hydrogels that are prepared by encapsulating photothermal agents into thermo-responsive hydrogel matrix exhibit more attractive advantages in biomedical applications owing to their spatiotemporal control and precise therapy. This work summarizes the latest progress of the photo-thermo coupled responsive hydrogel in biomedical applications. Three major elements of the photo-thermo coupled responsive hydrogel, i.e., thermo-responsive hydrogel matrix, photothermal agents, and construction methods are introduced. Furthermore, the recent developments of these hydrogels for biomedical applications are described with some selected examples. Finally, the challenges and future perspectives for photo-thermo coupled responsive hydrogels are outlined.

Multifunctional AuPt Nanoparticles for Synergistic Photothermal and Radiation Therapy

Background

Photothermal therapy (PTT) has gained considerable interest as an emerging modality for cancer treatment in recent years. Radiation therapy (RT) has been widely used in the clinic as a traditional treatment method. However, RT and PTT treatments are limited by side effects and penetration depth, respectively. In addition, hypoxia within the tumor can lead to increased resistance to treatment.

Methods

We synthesized multiple sizes of AuPt by modulating the reaction conditions. The smallest size of AuPt was selected and modified with folic acid (FA) for PTT and RT synergy therapy. Various methods including transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FITR) are used to determine the structure and composition of AuPt-FA (AF). In addition, we researched the photothermal properties of AF with IR cameras and infrared lasers. Flow cytometry, colony formation assays, CCK8, and fluorescent staining for probing the treatment effect in vitro. Also, we explored the targeting of AF by TEM and In Vivo Imaging Systems (IVIS). In vivo experiments, we record changes in tumor volume and weight as well as staining of tumor sections (ROS, Ki67, and hematoxylin and eosin).

Results

The AuPt with particle size of 16 nm endows it with remarkably high photothermal conversion efficiency (46.84%) and catalase activity compared to other sizes of AuPt (30 nm and 100 nm). AF alleviates hypoxia in the tumor microenvironment, leading to the production of more reactive oxygen species (ROS) during the treatment. In addition, the therapeutic effect was significantly enhanced by combining RT and PTT, with an apoptosis rate of 81.1% in vitro and an in vivo tumor volume reduction rate of 94.0% in vivo.

Conclusion

These results demonstrate that AF potentiates the synergistic effect of PTT and RT and has the potential for clinical translation.

Multifunctional Photothermal Hydrogel in the Second Near-Infrared Window for Localized Tumor Therapy

A copper selenide-embedded gellan gum hydrogel (Cu2-xSe@GG) is designed as an "all-in-one" antitumor agent. The obtained nanocomposite hydrogel exhibits strong near-infrared light absorption and high photothermal conversion efficiency in both the NIR-I and NIR-II biowindows. The photothermal conversion efficiency achieves 58.8% under the irradiation of 0.75 W/cm2 with a 1064 nm laser. Furthermore, the nanocomposite hydrogel has catalase- and peroxidase-mimicking activities, which could alter the tumor microenvironment by reducing hypoxia and/or increasing the production of reactive oxygen species. Moreover, the multifunctional Cu2-xSe@GG nanocomposite hydrogel can also be used as an immune agonist resiquimod (R848) carrier to promote immune regulation and enhance the therapeutic effect. The single-syringe R848/Cu2-xSe@GG treatment achieves synergetic photothermal immunotherapy, showing 97.4% of tumor regression rate from an initial large tumor of 300 mm3.

Glucose-Responsive Self-Regulated Injectable Silk Fibroin Hydrogel for Controlled Insulin Delivery

Stimuli-responsive drug delivery systems are gaining importance in personalized medicine to deliver therapeutic doses in response to disease-specific stimulation. Pancreas-mimicking glucose-responsive insulin delivery systems offer improved therapeutic outcomes in the treatment of type 1 and advanced stage of type 2 diabetic conditions. Herein, we present a glucose-responsive smart hydrogel platform based on phenylboronic acid-functionalized natural silk fibroin protein for regulated insulin delivery. The modified protein was synergistically self-assembled and cross-linked through β-sheet and phenylboronate ester formation. The dynamic nature of the bonding confers smooth injectability through the needle. The cross-linked hydrogel structures firmly hold the glucose-sensing element and insulin in its pores and contribute to long-term sensing and drug storage. Under hyperglycemic conditions, the hydrogen peroxide generated from the sensing element induces hydrogel matrix degradation by oxidative cleavage, enabling insulin release. In vivo studies in a type 1 diabetic Wistar rat model revealed that the controlled insulin release from the hydrogel restored diabetic glucose level to physiological conditions for 36 h. This work establishes the functional modification of silk fibroin into a glucose-responsive hydrogel platform for regulated and functional insulin delivery application.

Individually Tailored Modular "Egg" Hydrogels Capable of Spatiotemporally Controlled Drug Release for Spinal Cord Injury Repair

Controllable drug delivery systems (DDS) can overcome the disadvantages of conventional drug administration processes, such as high dosages or repeated administration. Herein, a smart DDS collagen hydrogel is deployed for spinal cord injury (SCI) repair based on modular designing of "egg" nanoparticles (NPs) that ingeniously accomplish controlled drug release via inducing a signaling cascade in response to external and internal stimuli. The "egg" NPs consist of a three-layered structure: tannic acid/Fe3+ /tetradecanol "eggshell," zeolitic imidazolate framework-8 (ZIF-8) "egg white," and paclitaxel "yolk." Then NPs served as a crosslinking epicenter, blending with collagen solutions to generate functional hydrogels. Remarkably, the "eggshell" efficiently converts near-infrared (NIR) irradiation into heat. Subsequently, tetradecanol can be triggered to disintegrate via heat, exposing the structure of ZIF-8. The Zn-imidazolium ion coordination bond of the "egg white" is susceptible to cleaving at the acidic SCI site, decomposing the skeleton to release paclitaxel on demand. As expected, the paclitaxel release rate upon NIR irradiation increased up to threefold on the seventh day, which matches endogenous neural stem/progenitor cell migration process. Taken together, the collagen hydrogels facilitate the neurogenesis and motor function recovery, demonstrating a revolutionary strategy for spatiotemporally controlled drug release and providing guidelines for the design of DDS.

Hydrogen-bonded organic framework-stabilized charge transfer cocrystals for NIR-II photothermal cancer therapy

Charge-transfer (CT) cocrystals consisting of an electron donor and acceptor have gained attention for designing photothermal (PT) conversion materials with potential for biomedical and therapeutic use. However, the applicability of CT cocrystals is limited by their low stability and aqueous dispersity in biological settings. In this study, we present the self-assembly of CT cocrystals within hydrogen-bonded organic frameworks (HOFs), which not only allows for the dispersion and stabilization of cocrystals in aqueous solution but also promotes the CT interaction within the confined space of HOFs for photothermal conversion. We demonstrate that the CT interaction-driven self-assembly of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) with PFC-1 HOFs results in the formation of cocrystal-encapsulated TQC@PFC-1 while retaining the crystalline structure of the cocrystal and PFC-1. TQC@PFC-1, in particular, exhibits significant absorption in the second near-infrared region (NIR-II) and excellent photothermal conversion efficiency, as high as 32%. Cellular delivery studies show that TQC@PFC-1 can be internalized in different types of cancer cells, leading to an effective NIR-II photothermal therapy effect both in cultured cells and in vivo. We anticipate that the strategy of self-assembly and stabilization of CT cocrystals in nanoscale HOFs opens the path for tuning their photophysical properties and interfacing cocrystals with biological settings for photothermal therapeutic applications.

Injectable hydrogels for the delivery of nanomaterials for cancer combinatorial photothermal therapy

Progress in the nanotechnology field has led to the development of a new class of materials capable of producing a temperature increase triggered by near infrared light. These photothermal nanostructures have been extensively explored in the ablation of cancer cells. Nevertheless, the available data in the literature have exposed that systemically administered nanomaterials have a poor tumor-homing capacity, hindering their full therapeutic potential. This paradigm shift has propelled the development of new injectable hydrogels for the local delivery of nanomaterials aimed at cancer photothermal therapy. These hydrogels can be assembled at the tumor site after injection (in situ forming) or can undergo a gel-sol-gel transition during injection (shear-thinning/self-healing). Besides incorporating photothermal nanostructures, these injectable hydrogels can also incorporate or be combined with other agents, paving the way for an improved therapeutic outcome. This review analyses the application of injectable hydrogels for the local delivery of nanomaterials aimed at cancer photothermal therapy as well as their combination with photodynamic-, chemo-, immuno- and radio-therapies.

Biomimetic Antithrombotic Tissue-Engineered Vascular Grafts for Converting Cholesterol and Free Radicals into Nitric Oxide

Small-diameter tissue-engineered vascular grafts (sdTEVGs) are essential materials used in bypass or replacement surgery for cardiovascular diseases; however, their application efficacy is limited because of patency rates, especially under hyperlipidemia, which is also clinically observed in patients with cardiovascular diseases. In such cases, improving sdTEVG patency is challenging because cholesterol crystals easily cause thrombosis and impede endothelialization. Herein, the development of a biomimetic antithrombotic sdTEVG incorporating cholesterol oxidase and arginine into biomineralized collagen-gold hydrogels on a sdTEVG surface is described. Biomimetic antithrombotic sdTEVGs represent a multifunctional substrate for the green utilization of hazardous substances and can convert cholesterol into hydrogen peroxide, which can react with arginine to generate nitric oxide (NO). NO is a vasodilator that can simulate the antithrombotic action of endothelial cells under hyperlipidemic conditions. In vivo studies show that sdTEVGs can rapidly produce large amounts of NO via a cholesterol catalytic cascade to inhibit platelet aggregation, thereby improving the blood flow velocity and patency rates 60 days after sdTEVG transplantation. A practical and reliable strategy for transforming "harmful" substances into "beneficial" factors at early transplantation stages is presented, which can also promote vascular transplantation in patients with hyperlipidemia.

Advances in preparation and application of antibacterial hydrogels

Bacterial infections, especially those caused by drug-resistant bacteria, have seriously threatened human life and health. There is urgent to develop new antibacterial agents to reduce the problem of antibiotics. Biomedical materials with good antimicrobial properties have been widely used in antibacterial applications. Among them, hydrogels have become the focus of research in the field of biomedical materials due to their unique three-dimensional network structure, high hydrophilicity, and good biocompatibility. In this review, the latest research progresses about hydrogels in recent years were summarized, mainly including the preparation methods of hydrogels and their antibacterial applications. According to their different antibacterial mechanisms, several representative antibacterial hydrogels were introduced, such as antibiotics loaded hydrogels, antibiotic-free hydrogels including metal-based hydrogels, antibacterial peptide and antibacterial polymers, stimuli-responsive smart hydrogels, and light-mediated hydrogels. In addition, we also discussed the applications and challenges of antibacterial hydrogels in biomedicine, which are expected to provide new directions and ideas for the application of hydrogels in clinical antibacterial therapy.

Hydrogel Nanocomposite Towards Optical Sensing of Spermine in Biomedical and Real-Life Food Samples and Remediation of Toxic Dyes from Wastewater

Nanocomposites such as graphene oxide (GO) have been incorporated into hydrogels to enhance conventional hydrogels' properties and develop new functions. Unique and strong molecular interactions between GO and low molecular weight gelators allow the fabrication of various functional hydrogels suitable for different applications. In the present study, we report a stable and soft nanocomposite hydrogel comprising a pyrene-based chiral amphipath having an amino acid (l-phenylalanine) core with pendant oligo-oxyethylene hydrophilic chains and GO. The mechanical and viscoelastic properties of the nanocomposite hydrogel were thoroughly studied using various spectroscopic, microscopic, and mechanical techniques. Even without GO, native hydrogels could form a self-supported thermoreversible and thixotropic hydrogel composed of the fibrillar network. Unlike native hydrogels, the morphological investigation of nanocomposite gels shows the presence of cross-linked nanosheet-like structures. The combined effect of π-π stacking and H-bonding interactions is the driving force for the formation of such composite hydrogels. Moreover, the nanocomposite hydrogels possess significantly superior mechanical stiffness than the native hydrogels. Interestingly, the thixotropic properties observed with the parent gel were retained even in the presence of carbon nanomaterials (GO). The nanocomposite hydrogel could be employed in the optical sensing of a biogenic polyamine, spermine, resulting in a visible gel-to-sol transition. The superior electrostatic interaction between the GOs and spermine molecules might have led to the release of entrapped fluorogenic dyes from the hydrogel network and a turn-on emission response. The sensory system was employed to analyze spermine content in human urine samples and decomposed food items. A gel-coated paper strip was also developed for onsite detection of the spermine. The nanocomposite hydrogel was further utilized to remove toxic organic dyes such as methylene blue (MB) and rhodamine B (RhB) from the aqueous media. The nanocomposite hydrogel thus showed excellent dye removal capabilities and was also found to be recyclable. Calculations of different mechanical parameters suggest that the dye removal efficiency of the nanocomposite hydrogel was better for MB than for RhB.

Emodin-Based Nanoarchitectonics with Giant Two-Photon Absorption for Enhanced Photodynamic Therapy

Two-photon-excited photodynamic therapy (TPE-PDT) has significant advantages over conventional photodynamic therapy (PDT). However, obtaining easily accessible TPE photosensitizers (PSs) with high efficiency remains a challenge. Herein, we demonstrate that emodin (Emo), a natural anthraquinone (NA) derivative, is a promising TPE PS with a large two-photon absorption cross-section (TPAC: 380.9 GM) and high singlet oxygen (1 O2 ) quantum yield (31.9 %). When co-assembled with human serum albumin (HSA), the formed Emo/HSA nanoparticles (E/H NPs) possess a giant TPAC (4.02×107  GM) and desirable 1 O2 generation capability, thus showing outstanding TPE-PDT properties against cancer cells. In vivo experiments reveal that E/H NPs exhibit improved retention time in tumors and can ablate tumors at an ultra-low dosage (0.2 mg/kg) under an 800 nm femtosecond pulsed laser irradiation. This work is beneficial for the use of natural extracts NAs for high-efficiency TPE-PDT.

Supramolecular Arrangement and Rheological Properties of Bisamide Gels

We report a systematic study of the gelation behavior of nBA gelators in xylene, with odd and even n-methylene spacers between the amide groups (n = 5-10) and 17 carbons at each end. The melting temperatures (Tm0) of nBA gels are obtained from fitting our DSCN(T) model to the experimental DSC data. The found Tm0 of nBA gels is about 35 °C lower than Tm0 of the pure nBA gelators. This is reasonably well explained by a simple model combining theories of Flory-Huggins and Gibbs free energy of melting (FHM model). We attribute this depression to an increase in entropy upon melting of the gel due to mixing with the solvent. The odd-even alternation in Tm0 of nBA gels, which was also found for the nBA gelators, indicates that the solid structures inside the gels are somewhat similar. This was studied using XRD: similar 00l reflections were found in the XRD patterns of all nBA gels and their nBA gelators. For even nBA gels, the same reflections in the 19-25° (2θ) region confirm that the sheetlike supramolecular structure of the gels is analogous to the lamellar structure of the solid gelators. For odd nBA gels, a slight difference in the reflections around 20-25° (2θ) implies a somewhat different side-by-side packing of odd nBA gels compared to the solid state. This variation is found for all the odd gels, and indeed, they show distinctly different morphologies compared to the even nBA gels. The possible effect of this on the rheological properties is discussed using some inspiration from the Halpin-Tsai model for composites where nBA gels are considered to be analogous to composite materials. The change of the storage modulus (G') with the shape factor of woven fibers and sheets in nBA gels (20 wt %) indicates that a rheological odd-even effect might indeed be present.

Nano-crosslinked dynamic hydrogels for biomedical applications

Hydrogels resemble natural extracellular matrices and have been widely studied for biomedical applications. Nano-crosslinked dynamic hydrogels combine the injectability and self-healing property of dynamic hydrogels with the versatility of nanomaterials and exhibit unique advantages. The incorporation of nanomaterials as crosslinkers can improve the mechanical properties (strength, injectability, and shear-thinning properties) of hydrogels by reinforcing the skeleton and endowing them with multifunctionality. Nano-crosslinked functional hydrogels that can respond to external stimuli (such as pH, heat, light, and electromagnetic stimuli) and have photothermal properties, antimicrobial properties, stone regeneration abilities, or tissue repair abilities have been constructed through reversible covalent crosslinking strategies and physical crosslinking strategies. The possible cytotoxicity of the incorporated nanomaterials can be reduced. Nanomaterial hydrogels show excellent biocompatibility and can facilitate cell proliferation and differentiation for biomedical applications. This review introduces different nano-crosslinked dynamic hydrogels in the medical field, from fabrication to application. In this review, nanomaterials for dynamic hydrogel fabrication, such as metals and metallic oxides, nanoclays, carbon-based nanomaterials, black phosphorus (BP), polymers, and liposomes, are discussed. We also introduce the dynamic crosslinking method commonly used for nanodynamic hydrogels. Finally, the medical applications of nano-crosslinked hydrogels are presented. We hope that this summary will help researchers in the related research fields quickly understand nano-crosslinked dynamic hydrogels to develop more preparation strategies and promote their development and application.

Nanoarchitecture-Integrated Hydrogel Systems toward Therapeutic Applications

Hydrogels, as one of the most feasible soft biomaterials, have gained considerable attention in therapeutic applications by virtue of their tunable properties including superior patient compliance, good biocompatibility and biodegradation, and high cargo-loading efficiency. However, hydrogel application is still limited by some challenges like inefficient encapsulation, easy leakage of loaded cargoes, and the lack of controllability. Recently, nanoarchitecture-integrated hydrogel systems were found to be therapeutics with optimized properties, extending their bioapplication. In this review, we briefly presented the category of hydrogels according to their synthetic materials and further discussed the advantages in bioapplication. Additionally, various applications of nanoarchitecture hybrid hydrogels in biomedical engineering are systematically summarized, including cancer therapy, wound healing, cardiac repair, bone regeneration, diabetes therapy, and obesity therapy. Last, the current challenges, limitations, and future perspectives in the future development of nanoarchitecture-integrated flexible hydrogels are addressed.

Photodynamic and Photothermal Therapies: Synergy Opportunities for Nanomedicine

Tumoricidal photodynamic (PDT) and photothermal (PTT) therapies harness light to eliminate cancer cells with spatiotemporal precision by either generating reactive oxygen species or increasing temperature. Great strides have been made in understanding biological effects of PDT and PTT at the cellular, vascular and tumor microenvironmental levels, as well as translating both modalities in the clinic. Emerging evidence suggests that PDT and PTT may synergize due to their different mechanisms of action, and their nonoverlapping toxicity profiles make such combination potentially efficacious. Moreover, PDT/PTT combinations have gained momentum in recent years due to the development of multimodal nanoplatforms that simultaneously incorporate photodynamically- and photothermally active agents. In this review, we discuss how combining PDT and PTT can address the limitations of each modality alone and enhance treatment safety and efficacy. We provide an overview of recent literature featuring dual PDT/PTT nanoparticles and analyze the strengths and limitations of various nanoparticle design strategies. We also detail how treatment sequence and dose may affect cellular states, tumor pathophysiology and drug delivery, ultimately shaping the treatment response. Lastly, we analyze common experimental design pitfalls that complicate preclinical assessment of PDT/PTT combinations and propose rational guidelines to elucidate the mechanisms underlying PDT/PTT interactions.

Hydrogels-A Promising Materials for 3D Printing Technology

Hydrogels are a promising material for a variety of applications after appropriate functional and structural design, which alters the physicochemical properties and cell signaling pathways of the hydrogels. Over the past few decades, considerable scientific research has made breakthroughs in a variety of applications such as pharmaceuticals, biotechnology, agriculture, biosensors, bioseparation, defense, and cosmetics. In the present review, different classifications of hydrogels and their limitations have been discussed. In addition, techniques involved in improving the physical, mechanical, and biological properties of hydrogels by admixing various organic and inorganic materials are explored. Future 3D printing technology will substantially advance the ability to pattern molecules, cells, and organs. With significant potential for producing living tissue structures or organs, hydrogels can successfully print mammalian cells and retain their functionalities. Furthermore, recent advances in functional hydrogels such as photo- and pH-responsive hydrogels and drug-delivery hydrogels are discussed in detail for biomedical applications.

Preparation of polymer nanoparticle-based complex coacervate hydrogels using polymerisation-induced self-assembly derived nanogels

This paper reports a generic method to prepare polymer nanoparticle-based complex coacervate (PNCC) hydrogels by employing rationally designed nanogels synthesised by reversible addition-fragmentation chain-transfer (RAFT)-mediated polymerisation-induced self-assembly (PISA). Specifically, a poly(potassium 3-sulfopropyl methacrylate) (PKSPMA) macromolecular chain-transfer agent (macro-CTA) was synthesised via RAFT solution polymerisation followed by chain-extension with a statistical copolymer of benzyl methacrylate (BzMA) and methacrylic acid (MAA) at pH 2. Thus, pH-responsive nanoparticles (NPs) comprising a hydrophobic polyacid core-forming block and a sulfonate-functional stabiliser block were formed. With the introduction of methacrylic acid into the core of the NPs, they become swollen with increasing pH, as judged by dynamic light scattering (DLS), indicating nanogel-type behaviour. PNCC hydrogels were prepared by simply mixing the PISA-derived nanogels and cationic branched polyethyleneimine (bPEI) at 20% w/w. In the absence of MAA in the core of the NPs, gel formation was not observed. The mass ratio between the nanogels and bPEI affected resulting hydrogel strength and a mixture of bPEI and PKSPMA₆₈-P(BzMA_0.6-stat-MAA_0.4)₃₀₀ NPs with a mass ratio of 0.14 at pH ∼7 resulted in a hydrogel with a storage modulus of approximately 2000 Pa, as determined by oscillatory rheology. This PNCC hydrogel was shear-thinning and injectable, with recovery of gel strength occurring rapidly after the removal of shear.

Biomimetic mineralization based on self-assembling peptides

Biomimetic science has attracted great interest in the fields of chemistry, biology, materials science, and energy. Biomimetic mineralization is the process of synthesizing inorganic minerals under the control of organic molecules or biomolecules under mild conditions. Peptides are the motifs that constitute proteins, and can self-assemble into various hierarchical structures and show a high affinity for inorganic substances. Therefore, peptides can be used as building blocks for the synthesis of functional biomimetic materials. With the participation of peptides, the morphology, size, and composition of mineralized materials can be controlled precisely. Peptides not only provide well-defined templates for the nucleation and growth of inorganic nanomaterials but also have the potential to confer inorganic nanomaterials with high catalytic efficiency, selectivity, and biotherapeutic functions. In this review, we systematically summarize research progress in the formation mechanism, nanostructural manipulation, and applications of peptide-templated mineralized materials. These can further inspire researchers to design structurally complex and functionalized biomimetic materials with great promising applications.

Selenium Silk Nanostructured Films with Antifungal and Antibacterial Activity

The rapid emergence of drug-resistant bacteria and fungi poses a threat for healthcare worldwide. The development of novel effective small molecule therapeutic strategies in this space has remained challenging. Therefore, one orthogonal approach is to explore biomaterials with physical modes of action that have the potential to generate antimicrobial activity and, in some cases, even prevent antimicrobial resistance. Here, to this effect, we describe an approach for forming silk-based films that contain embedded selenium nanoparticles. We show that these materials exhibit both antibacterial and antifungal properties while crucially also remaining highly biocompatible and noncytotoxic toward mammalian cells. By incorporating the nanoparticles into silk films, the protein scaffold acts in a 2-fold manner; it protects the mammalian cells from the cytotoxic effects of the bare nanoparticles, while also providing a template for bacterial and fungal eradication. A range of hybrid inorganic/organic films were produced and an optimum concentration was found, which allowed for both high bacterial and fungal death while also exhibiting low mammalian cell cytotoxicity. Such films can thus pave the way for next-generation antimicrobial materials for applications such as wound healing and as agents against topical infections, with the added benefit that bacteria and fungi are unlikely to develop antimicrobial resistance to these hybrid materials.

3D Printing of Hybrid-Hydrogel Materials for Tissue Engineering: a Critical Review

Purpose

Key natural polymers, known as hydrogels, are an important group of materials in design of tissue-engineered constructs that can provide suitable habitat for cell attachment and proliferation. However, in comparison to tissues within the body, these hydrogels display poor mechanical properties. Such properties cause challenges in 3D printing of hydrogel scaffolds as well as their surgical handling after fabrication. For this reason, the purpose of this study is to critically review the 3D printing processes of hydrogels and their characteristics for tissue engineering application.

Methods

A search of Google Scholar and PubMed has been performed from 2003 to February 2022 using a combination of keywords. A review of the types of 3D printing is presented. Additionally, different types of hydrogels and nano-biocomposite materials for 3D printing application are critically reviewed. The rheological properties and crosslinking mechanisms for the hydrogels are assessed.

Results

Extrusion-based 3D printing is the most common practice for constructing hydrogel-based scaffolds, and it allows for the use of varying types of polymers to enhance the properties and printability of the hydrogel-based scaffolds. Rheology has been found to be exceedingly important in the 3D printing process; however, shear-thinning and thixotropic characteristics should also be present in the hydrogel. Despite these features of extrusion-based 3D printing, there are limitations to its printing resolution and scale.

Conclusion

Combining natural and synthetic polymers and a variety of nanomaterials, such as metal, metal oxide, non-metal, and polymeric, can enhance the properties of hydrogel and provide additional functionality to their 3D-printed constructs.