Peptide-/Drug-Directed Self-Assembly of Hybrid Polyurethane Hydrogels for Wound Healing

Hydrogel innovations for 3D organoid culture

Organoids are functional cell-tissue complexes that mimic structural and functional characteristics of organsin vitroin three dimensions (3D). Mimicking the natural extracellular matrix (ECM) environment is critical for guiding stem cell fate within organoid cultures. Current organoid cultures predominantly utilize animal- or tumor-derived ECMs such as dECMs and Matrigel. However, these materials introduce batch variability and uncertainty in composition, which hinders reproducibility. In contrast, naturally derived and synthetic hydrogels with excellent biocompatibility offer precise and adjustable compositions, along with tunable mechanical properties, thereby providing robust support for organoid development and maturation. We explore innovative hydrogel designs tailored specifically for organoid cultures, emphasizing the influence and meticulous control of functional hydrogels on organoid formation, differentiation, and maturation processes. Furthermore, the review highlights the potential of functionalized hydrogel scaffolds to advance both research and industrial applications in tissue and organ engineering. As research progresses, investigations will further concentrate on improving the adjustable properties, expanding their scope of application, and more biologically compatible gelation strategies of hydrogels.

Smart self-assembled peptide-based hydrogels: Mechanism, design and biomedical applications

Peptide hydrogels have gained widespread attention in biomedical engineering due to their unique ability to mimic the cellular microenvironment in vivo. Stimulus-responsive self-assembled (SAP) hydrogels can undergo conformational changes in response to changes in the external environment, prompting a sol-gel transition. Their inherent biodegradability, excellent surface activity and biocompatibility make them ideal candidates for a wide range of biomedical applications, and these SAP hydrogels can be widely used in the fields of tissue engineering, cell and drug delivery, wound healing and medical diagnostic imaging. In this paper, the basic properties, design principles, preparation methods and self-assembly mechanisms of different types of stimuli-responsive SAP hydrogels are reviewed. By designing and constructing stimulus-responsive SAP hydrogels, we can create materials that mimic natural physiological environments, thereby better simulating cell behavior and tissue repair. In addition, it highlights specific applications of these hydrogels in biomedical engineering, supported by examples from recent literature. The report summarizes the current state of research, highlights key challenges, and provides insights into future prospects to encourage continued innovation and exploration in this rapidly evolving field.

Improving the bioactivity and mechanical properties of poly(ethylene glycol)-based hydrogels through a supramolecular support network

Most synthetic hydrogels are formed through radical polymerization to yield a homogenous covalent meshwork. In contrast, natural hydrogels form through mechanisms involving both covalent assembly and supramolecular interactions. In this communication, we expand the capabilities of covalent poly(ethylene glycol) (PEG) networks through co-assembly of supramolecular peptide nanofibers. Using a peptide hydrogelator derived from the tryptophan zipper (Trpzip) motif, we demonstrate how in situ formation of nanofiber networks can tune the stiffness of PEG-based hydrogels, while also imparting shear thinning, stress relaxation, and self-healing properties. The hybrid networks show enhanced toughness and durability under tension, providing scope for use in load bearing applications. A small quantity of Trpzip peptide renders the non-adhesive PEG network adhesive, supporting adipose derived stromal cell adhesion, elongation, and growth. The integration of supramolecular networks into covalent meshworks expands the versatility of these materials, opening up new avenues for applications in biotechnology and medicine.

Influence of Electrostatic Interactions on the Self-Assembly of Charged Peptides

Peptides can be designed to self-assemble into predefined supramolecular nanostructures, which are then employed as biomaterials in a range of applications, including tissue engineering, drug delivery, and vaccination. However, current self-assembling peptide (SAP) hydrogels exhibit inadequate self-healing capacities and necessitate the use of sophisticated printing apparatus, rendering them unsuitable for 3D printing under physiological conditions. Here, we report a precisely designed charged peptide, Z5, with the object of investigating the impact of electrostatic interactions on the self-assembly and the rheological properties of the resulting hydrogels. This peptide displays salt-triggered self-assembly resulting in the formation of a nanofiber network with a high β-sheet content. The peptide self-assembly and the hydrogel properties can be modified according to the ionic environment. It is noteworthy that the Z5 hydrogel in normal saline (NS) shows exceptional self-healing properties, demonstrating the ability to recover its initial strength in seconds after the removal of shear force, thus rendering it an acceptable material for printing. In contrast, the strong salt shielding effect and the ionic cross-linking of Z5 hydrogels in PBS result in the bundling of peptide nanofibers, which impedes the recovery of the initial strength post-destruction. Furthermore, incorporating materials with varied charging properties into Z5 hydrogels can alter the electrostatic interactions among peptide nanofibers, further modulating the rheological properties and the printability of SAP hydrogels.

Fabrication of curcumin-incorporated human amniotic membrane extracellular matrix-derived scaffold to enhance full-thickness wound healing in diabetic rats

The multifactorial nature of diabetic wounds necessitates a mixed approach for successful treatment. Compensation of degenerated wound tissue extracellular matrix (ECM) and application of anti-inflammatory and antioxidant agents have been shown to be promising. Here, an attempt was made to fabricate a biocompatible wound dressing from curcumin-incorporated human amniotic membrane (HAM) ECM-derived scaffold to accelerate diabetic wound healing in rats. Therefore, after inducing diabetes, an excisional ischemic wound was created on rat skin, then treatments were administered for a period of 21 days. The main groups were the diabetic animals that received an engraftment of HAM scaffold (HAMS group) and the curcumin-incorporated HAMS (HAMS/β/C group). Evaluation at post-wounding days 7, 14, and 21 indicated that the parameters related to regeneration, including wound closure, volume of new epidermis and dermis, proliferating cells, fibroblasts, blood vessels, collagen deposition, and tensile strength, as well as transcripts of Vegf, bFgf, and Tgf-β genes of the healed wound in both HAMS and HAMS/β/C groups were considerably greater than those of the diabetic group. Conversely, the presence of inflammatory cells, i.e., neutrophils and macrophages, and the transcripts of Tnf-α and Il-1β showed a dramatic decrease in the treated groups relative to the diabetic group. Finally, compared to the HAMS group, considerable differences were found with the HAMS/β/C group in almost all evaluated parameters. Overall, these results suggest that using the complementary or synergistic effects of curcumin and HAMS could be a promising approach to improve diabetic wound healing.

ROS/Thermo dual-sensitive hydrogel loaded with a nanoemulsion of patchouli essential oil for ulcerative colitis

Patchouli essential oil (PEO) is acknowledged as a potent contender for the management of ulcerative colitis (UC). However, the limited ability of PEO to be absorbed by the body and its low stability substantially limit its potential uses. Furthermore, UC lesions are mainly concentrated in the rectal and colonic mucosa, with excessive production of reactive oxygen species (ROS). Herein, a nanoemulsion of PEO (PEONE) was developed to enhance the stability and bioavailability of a drug. Subsequently, we developed a novel platform for the rectal administration of a ROS/thermo dual-sensitive Bletilla striata polysaccharide-based hydrogel (RTH) co-loaded with PEONE to efficiently treat UC. As expected, the sol-gel transition of PEONE@RTH, after its intrarectal administration, resulted in its extended presence in the colon and facilitated its attachment to the inflammation site. Moreover, PEONE@RTH alleviated dextran sulfate sodium-induced UC symptoms by suppressing inflammation and oxidative stress, repairing the damage to the intestinal epithelial barrier (claudin-1 and occludin), increasing short-chain fatty acid content and inhibiting the MAPK signalling pathway. Additionally, PEONE@RTH exhibits exceptional safety and biocompatibility. Thus, PEONE@RTH has the potential to provide a novel approach for treating UC and other intestinal disorders characterised by similar clinical conditions.

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.

A review of polysaccharide hydrogels as materials for skin repair and wound dressing: Construction, functionalization and challenges

Hydrogels can imitate the extracellular matrix, therefore facilitating the creation of an ideal healing environment for wounds. Consequently, they are popular as a material choice for wound dressings. Polysaccharides have been widely used in wound dressings due to their good biocompatibility and degradability. In this study, we first discuss skin and wound physiology before summarizing the methods for producing hydrogels from polysaccharides and their derivatized. These include not just normal polysaccharides like chitosan, cellulose, and alginate, but also Chinese medicinal polysaccharides with therapeutic properties. Then, strategies for causing hydrogel production from polysaccharides or their derivatives are briefly explained. Finally, the functions of hydrogel dressings are reviewed, including antibacterial, antioxidant, and adhesive properties, as well as the methods for achieving these properties. Furthermore, current issues and concerns are discussed, with the goal of providing fresh paths for the development of future wound dressings.

A Photothermal Polymeric Platform for Efficient and Safe Gene Transfection: When Polyethylenimine Collaborates with Indocyanine Green

Gene transfection, defined by the delivery of nucleic acids into cellular compartments, stands as a crucial procedure in gene therapy. While branched polyethylenimine (PEI) is widely regarded as the "gold standard" for nonviral vectors, its cationic nature presents several issues, including nonspecific protein adsorption and notable cytotoxicity. Additionally, it often fails to achieve high transfection efficiency, particularly with hard-to-transfect cell types. To overcome these challenges associated with PEI as a vector for plasmid DNA (pDNA), the photothermal agent indocyanine green (ICG) is integrated with PEI and pDNA to form the PEI/ICG/pDNA (PI/pDNA) complex for more efficient and safer gene transfection. The negatively charged ICG serves a dual purpose: neutralizing PEI's excessive positive charges to reduce cytotoxicity and, under near-infrared irradiation, inducing local heating that enhances cell membrane permeability, thus facilitating the uptake of PI/pDNA complexes to boost transfection efficiency. Using pDNA encoding vascular endothelial growth factor as a model, our system shows enhanced transfection efficiency in vitro for hard-to-transfect endothelial cells, leading to improved cell proliferation and migration. Furthermore, in vivo studies reveal the therapeutic potential of this system in accelerating the healing of infected wounds by promoting angiogenesis and reducing inflammation. This approach offers a straightforward and effective method for gene transfection, showing potentials for tissue engineering and cell-based therapies.

Elastin-Derived Peptide-Based Hydrogels as a Potential Drug Delivery System

A peptide-based hydrogel sequence was computationally predicted from the Ala-rich cross-linked domains of elastin. Three candidate peptides were subsequently synthesised and characterised as potential drug delivery vehicles. The elastin-derived peptides are Fmoc-FFAAAAKAA-NH2, Fmoc-FFAAAKAA-NH2, and Fmoc-FFAAAKAAA-NH2. All three peptide sequences were able to self-assemble into nanofibers. However, only the first two could form hydrogels, which are preferred as delivery systems compared to solutions. Both of these peptides also exhibited favourable nanofiber lengths of at least 1.86 and 4.57 µm, respectively, which are beneficial for the successful delivery and stability of drugs. The shorter fibre lengths of the third peptide (maximum 0.649 µm) could have inhibited their self-assembly into the three-dimensional networks crucial to hydrogel formation.

Click method preserves but EDC method compromises the therapeutic activities of the peptide-activated hydrogels for critical ischemic vessel regeneration

Peptide-functionalized hydrogel is one of commonly used biomaterials to introduce hydrogel-induced vessel regeneration. Despite many reports about the discoveries of high-active peptides (or ligands) for regeneration, the study on the conjugating methods for the hydrogel functionalization with peptides is limited. Here, we compared the vasculogenic efficacy of the peptide-functionalized hydrogels prepared by two commonly used conjugating methods, 1-ethyl-3-(3-dimethylamino propyl) carbodiimide (EDC) and Click methods, through cell models, organ-on-chips models, animal models, and RNA sequencing analysis. Two vascular-related cell types, the human umbilical vein endothelial cells (HUVECs) and the adipose-derived stem cells (ADSCs), have been cultured on the hydrogel surfaces prepared by EDC/Click methods. It showed that the hydrogels prepared by Click method supported the higher vasculogenic activities while the ones made by EDC method compromised the peptide activities on hydrogels. The vasculogenesis assays further revealed that hydrogels prepared by Click method promoted a better vascular network formation. In a critical ischemic hindlimb model, only the peptide-functionalized hydrogels prepared by Click method successfully salvaged the ischemic limb, significantly improved blood perfusion, and enhanced the functional recoveries (through gait analysis and animal behavior studies). RNA sequencing studies revealed that the hydrogels prepared by Click method significantly promoted the PI3K-AKT pathway activation compared to the hydrogels prepared by EDC method. All the results suggested that EDC method compromised the functions of the peptides, while Click method preserved the vascular regenerating capacities of the peptides on the hydrogels, illustrating the importance of the conjugating method during the preparation of the peptide-functionalized hydrogels.

In Situ Nanoencapsulation of Curcumin in Soy Protein Isolate Amyloid-like Aggregates for Enhanced Wound Healing

The importance of amyloid nanofibrils made from food proteins is rising in diverse fields, such as biomedicine and food science. These protein nanofibrils (PNFs) serve as versatile and sustainable building blocks for biomaterials, characterized by their high β-sheet content and an ordered hydrogen bond network. These properties offer both stability and flexibility, along with an extreme aspect ratio and reactive functional groups. Plant-derived amyloid nanofibrils, such as soy protein isolate (SPI) PNFs, are increasingly favored due to their affordability and sustainability compared with animal proteins. This study aimed to explore the formation and application of SPI amyloid-like aggregates (SPIA) and their nanoencapsulation of curcumin (Cur) for biomedical purposes, particularly in wound healing. Under specific conditions of low pH and high temperature, SPIA formed, exhibited an amyloid nature, and successfully encapsulated Cur, thereby enhancing its stability and availability. Spectroscopic and microscopic analyses confirmed structural changes in SPIA upon the incorporation of Cur and the fabrication of SPIA@Cur. The obtained results indicate that in the presence of Cur, SPIA forms faster, attributed to accelerated SPI denaturation, an increased nucleation rate, and enhanced self-assembly facilitated by Cur's hydrophobic interactions and π-π stacking with SPI peptides. In vitro studies demonstrated the biocompatibility, biodegradability, and antioxidant properties of SPIA@Cur along with controlled release behavior. In vivo experiments in male Wistar rats revealed that both SPIA and SPIA@Cur significantly accelerate wound closure compared with untreated wounds, with SPIA@Cur showing slightly better efficacy. The histological analysis supported enhanced wound healing, indicating the potential of SPIA@Cur for biomedical applications.

Mechanism of Peptide Self-assembly and Its Study in Biomedicine

The development of peptide-based materials is one of the most challenging aspects of biomaterials research in recent years. The assembly of peptides is mainly controlled by forces such as hydrogen bonding, hydrophobic interaction, electrostatic interaction, and π-π accumulation. Peptides have unique advantages such as simple structure, easy synthesis, good biocompatibility, non-toxicity, easy modification, etc. These factors make peptides turn into ideal biomedical materials, and they have a broad application prospect in biomedical materials, and thus have received wide attention. In this review, the mechanism and classification of peptide self-assembly and its applications in biomedicine and hydrogels were introduced.

Sulfated glyco-based hydrogels as self-healing, adhesive, and anti-inflammatory dressings for wound healing

Hydrogels have emerged as a new type of wound dressing materials that involved in different stages of the healing processes. However, most of the existing wound dressings mainly offer a protective and moisturizing layer to prevent cross-infection, while the anti-inflammatory and anti-oxidative properties are frequently induced by extra addition of other bioactive molecules. Here, a novel type of sulfated glyco-functionalized hydrogels for wound dressing was prepared through the hybrid supramolecular co-assembly of carbohydrate segments (FG, FGS and FG3S), fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF), and diphenylalanine-dopamine (FFD). Implanting sulfated carbohydrates can mimic the structure of glycosaminoglycans (GAGs), promoting cell proliferation and migration, along with anti-inflammatory effects. In situ polymerization of FFD introduced a secondary covalent network to the hydrogel, meanwhile, providing anti-oxidation and adhesion properties to wound surfaces. Furthermore, the dynamic supramolecular interactions within the hydrogels also confer self-healing capabilities to the wound dressing materials. In vivo experiments further demonstrated significantly accelerated healing rates with the multifunctional hydrogel FG3S-FFD, indicating high application potential.

Multifunctional polypeptide-based hydrogel bio-adhesives with pro-healing activities and their working principles

Wound healing is a complex physiological process involving hemostasis, inflammation, proliferation, and tissue remodeling. Therefore, there is an urgent need for suitable wound dressings for effective and systematical wound management. Polypeptide-based hydrogel bio-adhesives offer unique advantages and are ideal candidates. However, comprehensive reviews on polypeptide-based hydrogel bio-adhesives for wound healing are still lacking. In this review, the physiological mechanisms and evaluation parameters of wound healing were first described in detail. Then, the working principles of hydrogel bio-adhesives were summarized. Recent advances made in multifunctional polypeptide-based hydrogel bio-adhesives involving gelatin, silk fibroin, fibrin, keratin, poly-γ-glutamic acid, ɛ-poly-lysine, serum albumin, and elastin with pro-healing activities in wound healing and tissue repair were reviewed. Finally, the current status, challenges, developments, and future trends of polypeptide-based hydrogel bio-adhesives were discussed, hoping that further developments would be stimulated to meet the growing needs of their clinical applications.

Stimuli-responsive peptide assemblies: Design, self-assembly, modulation, and biomedical applications

Peptide molecules have design flexibility, self-assembly ability, high biocompatibility, good biodegradability, and easy functionalization, which promote their applications as versatile biomaterials for tissue engineering and biomedicine. In addition, the functionalization of self-assembled peptide nanomaterials with other additive components enhances their stimuli-responsive functions, promoting function-specific applications that induced by both internal and external stimulations. In this review, we demonstrate recent advance in the peptide molecular design, self-assembly, functional tailoring, and biomedical applications of peptide-based nanomaterials. The strategies on the design and synthesis of single, dual, and multiple stimuli-responsive peptide-based nanomaterials with various dimensions are analyzed, and the functional regulation of peptide nanomaterials with active components such as metal/metal oxide, DNA/RNA, polysaccharides, photosensitizers, 2D materials, and others are discussed. In addition, the designed peptide-based nanomaterials with temperature-, pH-, ion-, light-, enzyme-, and ROS-responsive abilities for drug delivery, bioimaging, cancer therapy, gene therapy, antibacterial, as well as wound healing and dressing applications are presented and discussed. This comprehensive review provides detailed methodologies and advanced techniques on the synthesis of peptide nanomaterials from molecular biology, materials science, and nanotechnology, which will guide and inspire the molecular level design of peptides with specific and multiple functions for function-specific applications.

Laminin mimetic angiogenic and collagen peptide hydrogel for enhance dermal wound healing

Laminins are essential in basement membrane architecture and critical in re-epithelialization and angiogenesis. These processes and collagen deposition are vital in skin wound healing. The role of angiogenic peptides in accelerating the wound-healing process has been known. The bioactive peptides could be a potential approach due to their similar effects as growth factors and inherent biocompatible and biodegradable nature with lower cost. They can also recognize ligand-receptor interaction and mimic the extracellular matrix. Here, we report novel angiogenic DYVRLAI, CDYVRLAI, angiogenic-collagen PGPIKVAV, and Ac-PGPIKVAV peptides conjugated sodium carboxymethyl cellulose hydrogel, which was designed from laminin. The designed peptide exhibits a better binding with the α3β1, αvβ3, and α5β1 integrins and CXCR2 receptor, indicating their angiogenic and collagen binding efficiency. The peptides were evaluated to stimulate wound healing in full-thickness excision wounds in normal and diabetic mice (type II). They demonstrated their efficacy in terms of angiogenesis (CD31), re-epithelialization through regeneration of the epidermis (H&E), and collagen deposition (MT). The synthesized peptide hydrogel (DYVRLAI and CDYVRLAI) showed enhanced wound contraction up to 10.1 % and 12.3 % on day 7th compared to standard becaplermin gel (49 %) in a normal wound model. The encouraging results were also observed with the diabetic model, where these peptides showed a significant decrease of 5.20 and 5.17 % in wound size on day 10th compared to the commercial gel (9.27 %). These outcomes signify that the modified angiogenic peptide is a cost effective, novel peptide motif to promote dermal wound healing in both models.

Antioxidant Hydrogels: Antioxidant Mechanisms, Design Strategies, and Applications in the Treatment of Oxidative Stress-Related Diseases

Oxidative stress is a biochemical process that disrupts the redox balance due to an excess of oxidized substances within the cell. Oxidative stress is closely associated with a multitude of diseases and health issues, including cancer, diabetes, cardiovascular diseases, neurodegenerative disorders, inflammatory conditions, and aging. Therefore, the developing of antioxidant treatment strategies has emerged as a pivotal area of medical research. Hydrogels have garnered considerable attention due to their exceptional biocompatibility, adjustable physicochemical properties, and capabilities for drug delivery. Numerous antioxidant hydrogels have been developed and proven effective in alleviating oxidative stress. In the pursuit of more effective treatments for oxidative stress-related diseases, there is an urgent need for advanced strategies for the fabrication of multifunctional antioxidant hydrogels. Consequently, the authors' focus will be on hydrogels that possess exceptional reactive oxygen species and reactive nitrogen species scavenging capabilities, and their role in oxidative stress therapy will be evaluated. Herein, the antioxidant mechanisms and the design strategies of antioxidant hydrogels and their applications in oxidative stress-related diseases are discussed systematically in order to provide critical insights for further advancements in the field.

Stereogenic Harmony Fabricated Mechanoresponsive Homochiral Triphenylalanine Analogues with Synergistic Antibacterial Performances: A Potential Weapon for Dermal Wound Management

The wound recovery phenomenon remains as one of the long challenging concerns worldwide. In search of user-friendly dressing materials, in this report, we fabricated a rational combinatorial strategy utilizing stereogenic harmony in a triphenylalanine fragment and appending it to δ-amino valeric acid at the N-terminus (hydrogelators I-VII) such that a potential scaffold could be fished out from the design. Our investigations revealed that all the hydrogelators displayed not only excellent self-healing performance as well as high mechanical strength at physiological pH but also mechanical stress-triggered gel-sol-gel transition properties. The structural and morphological investigation confirmed the presence of β-sheet-like assemblies stabilized by intermolecular H-bonding and π-π interactions. Moreover, these scaffolds showed substantial antibacterial as well as antifungal efficacy against common wound pathogens, i.e, four Gram-positive bacteria (Staphylococcus aureus, Streptococcus mutans, B. subtilis, E. fecalis), four Gram-negative bacteria (Escherichia coli, Klebsiella pneumonia, P. aerugonosa, Proteus spp.), and two fungal strains (C. albicans and A. niger). The manifestation of consistent antioxidant properties might be due to the enhancement of amphiphilicity in hydrogelators, which has led to the generation of reactive oxygen species (ROS) in a facile manner, a probable mechanism to damage the microbial membrane, the driving force behind the antimicrobial efficacy. Also, the constructs exhibited proteolytic resistance and remarkable biocompatibility toward mammalian cells. Thus, based on the above benchmarks, the homochiral hydrogelator IV was seived out from a pool of seven, and we proceeded toward its in vivo evaluation using full-thickness excisional wounds in Wister rats. The scaffolds also accentuated the re-epithelialization as well in comparison to the negative control, thereby facilitating the wound closure process in a very short span of time (10 days). Overall, our in vitro and in vivo analysis certifies hydrogelator IV as an ideal dressing material that might hold immense promise for future wound care management.

pH-Responsive Injectable Multifunctional Pluronic F127/Gelatin-Based Hydrogels with Hydrogen Production for Treating Diabetic Wounds

Diabetic chronic wounds remain a major clinical challenge with long-term inflammatory responses and extreme oxidative damage. Hence, a pH-responsive injectable multifunctional hydrogel [Gel/CUR-FCHO/Mg (GCM) micromotors] via a Schiff base reaction between gelatin and benzaldehyde-grafted Pluronic F127 drug-loaded micelles (FCHO) was fabricated for the first time. Dynamic Schiff base linkage endowed the GCM hydrogel with the ability to be self-healing, injectable, and pH-responsive for on-demand drug delivery at the wound site. Curcumin (CUR), a hydrophobic drug with antioxidative, anti-inflammatory, and antibacterial activities, was encapsulated into the hydrogel matrix by micellization (CUR-FCHO micelles). Simultaneously, magnesium-based micromotors (Mg micromotors) were physically entrapped into the system for providing active hydrogen (H2) to scavenge reactive oxygen species and alleviate inflammatory responses. As a result, the GCM micromotor hydrogel displayed an inherent antibacterial property, extraordinary antioxidative performance, and remarkable biocompatibility. In the diabetic mouse with a full-thickness cutaneous defect wound, the GCM hydrogel could remodel the inflammatory microenvironment and stimulate vascularization and collagen deposition, thereby facilitating wound closure and enhancing tissue regeneration, which offered a promising therapeutic option for diabetic chronic wound management.

Curcumin-loaded methacrylate pullulan with grafted carboxymethyl-β-cyclodextrin to form hydrogels for wound healing: In vitro evaluation

A pullulan (Pul)-derivative hydrogel was developed by introducing methacrylate (MA) groups and β-cyclodextrin (βCD) to form a Pul-βCD-MA hydrogel by UV cross-linking. The MA was expected to improve the hydrogel's mechanical properties and the βCD to increase the solubility of curcumin. Pul-βCD-MA was successfully synthesized, as confirmed by the 1H NMR and FTIR spectra. Hydrogels were formed at Pul-βCD-MA concentrations of 5 %, 7.5 %, or 10 % w/v. Pul-βCD-MA showed enhanced curcumin solubility compared to Pul or Pul-MA. The morphological analysis of the hydrogel showed a porous structure. The concentration of βCD affected the hydrogels' mechanical properties, and the 7.5 % hydrogel (with or without curcumin) did not fracture. The cumulative release of curcumin in the 7.5 % Pul-βCD-MA hydrogel was 60 % over 8 h. The release profile fit the Korsmeyer-Peppas model. In vitro cytotoxicity tests revealed that hydrogels were biocompatible with human primary dermal fibroblast cells. Curcumin-loaded Pul-βCD-MA hydrogels significantly accelerated wound healing compared to Pul-βCD-MA hydrogels without curcumin loading. Therefore, the Pul derivative's hydrogel may be a promising material for wound healing.

Tailored biomedical materials for wound healing

Wound healing is a long-term, multi-stage biological process that mainly includes haemostatic, inflammatory, proliferative and tissue remodelling phases. Controlling infection and inflammation and promoting tissue regeneration can contribute well to wound healing. Smart biomaterials offer significant advantages in wound healing because of their ability to control wound healing in time and space. Understanding how biomaterials are designed for different stages of wound healing will facilitate future personalized material tailoring for different wounds, making them beneficial for wound therapy. This review summarizes the design approaches of biomaterials in the field of anti-inflammatory, antimicrobial and tissue regeneration, highlights the advanced precise control achieved by biomaterials in different stages of wound healing and outlines the clinical and practical applications of biomaterials in wound healing.

Peptide-polyurea hybrids: a platform for tunable, thermally-stable, and injectable hydrogels

Drawing inspiration from natural systems, such as the highly segmented structures found in silk fibroin, is an important strategy when designing strong, yet dynamic biomaterials. Polymer-peptide hybrids aim to incorporate the benefits of hierarchical polypeptide structures into synthetic platforms that are promising materials for hydrogel systems due to aspects such as their biocompatibility and structural tunability. In this work, we demonstrated the utility of poly(ethylene glycol) (PEG) peptide-polyurea hybrids as self-assembled hydrogels. Specifically, poly(ε-carbobenzyloxy-L-lysine)-b-PEG-b-poly(ε-carbobenzyloxy-L-lysine) and poly(β-benzyl-L-aspartate)-b-PEG-b-poly(β-benzyl-L-aspartate) triblock copolymers were used as the soft segments in linear peptide-polyurea (PPU) hybrids. We systematically examined the effect of peptide secondary structure and peptide segment length on hydrogelation, microstructure, and rheological properties of our PPU hydrogels. Polymers containing α-helical secondary structures resulted in rapid gelation upon the addition of water, as driven by hierarchical assembly of the peptide segments. Peptide segment length dictated gel strength and resistance to deformation via complex relationships. Simulated injection experiments demonstrated that PPU hydrogels recover their original gel network within 10 s of cessation of high shear. Finally, we showed that PPU hydrogels remain solid-like within the range of 10 to 80 °C; however, a unique softening transition occurs at temperatures corresponding to slight melting of secondary structures. Overall, this bioinspired PPU hybrid platform provides opportunities to design synthetic, bioinspired polymers for hydrogels with tunable microstructure and mechanics for a wide range of thermal and injection-based applications.

A Homochiral Diphenylalanine Analog Based Mechanoresponsive Hydrogel: An Insight Towards Its Wound Healing Efficacy

Deciphering the most promising strategy for the evolution of potential wound-healing therapeutics is one of the greatest challenging affairs to date. The development of peptide-based smart scaffolds with innate antimicrobial, anti-inflammatory, and antioxidant properties is an appealing way out. Aligned to the goal a set of Hydrogelators I-IV were developed utilizing the concept of chiral orchestration in diphenylalanine fragment, such that the most potent construct with all the bench marks namely mechanoresponsiveness, biocompatibility, consistent antimicrobial and antioxidant properties, could be fished out from the design. Interestingly, our in vitro Antifungal and Lipid peroxidation analysis identified the homochiral isomer Boc-δ-Ava-L-Phe-L-Phe-OH (Hydrogelator I), as an ideal candidate for the wound healing experiment, so we proceeded for the in vivo histopathological and antioxidant measurements in Wister rats. Indeed the wound images obtained from the different sets of animals on the 14th day of treatment demonstrated that with increased recovery time, hydrogelator I displayed a significant reduction in the lesion diameter compared to the marketed drug, and negative control. Even the histopathological measurements using H & E staining demonstrated diminished tissue destruction, neutrophil infiltration necrosis, and lymphatic proliferation in the hydrogelators, in comparison to others, backed by in vivo lipid peroxidation data. Overall our investigation certifies hydrogelator I as an effective therapeutic for managing the wound healing complication.

A biodegradable injectable fluorescent polyurethane-oxidized dextran hydrogel for non-invasive monitoring

Hydrogels have been extensively used in the field of biomedical engineering. In order to achieve non-invasive and real-time visualization of the in vivo status of hydrogels, we designed a fluorescent polyurethane-oxidized dextran (PU-OD) hydrogel with good injectability and self-healing properties, which was cross-linked from a tetraphenyl ethylene (TPE)-containing fluorescent polyurethane emulsion with oxidized dextran by dynamic acylhydrazone bonds. The hydrogel can be used as a visual platform for drug delivery as well as monitoring its own degradation. The network structure of the hydrogel gave it drug-loading capability, and the acylhydrazone bond enabled its pH-responsive drug release. Meanwhile, the PU-OD hydrogel could undergo fluorescence resonance transfer with doxorubicin hydrochloride, showing its potential application in monitoring drug release. In addition, fluorometric and weighing methods were performed to monitor the degradation behavior of the hydrogels in vivo and in vitro, respectively, showing that the non-invasive fluorometric method can be consistent with the invasive weighing method. This work highlights that the introduction of aggregation-induced emission molecules into polyurethanes provides a visual platform that allows for non-invasive monitoring of the material without affecting its own function, which is convenient and less damaging to the body or animals. Consequently, it possesses excellent and promising potential in biomedical materials technologies.

Drug-Embedded Nanovesicles Assembled from Peptide-Decorated Hyaluronic Acid for Rheumatoid Arthritis Synergistic Therapy

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that causes endless pain and poor quality of life in patients. Usage of a lubricant combined with anti-inflammatory therapy is considered a reasonable and effective approach for the treatment of RA. Herein, inspired by glycopeptides, a peptide-decorated hyaluronic acid was synthesized, and the grafted Fmoc-phenylalanine-phenylalanine-COOH (FmocFF) peptide self-assembled with β-sheet conformations could induce the folding of polymer molecular chains to form a vesicle structure in aqueous solution. The hydrophobic anti-inflammatory drug curcumin (Cur) could be embedded in the vesicle walls through π-π interactions with the FmocFF peptide. Furthermore, the inflammation suppression function of the Cur-loaded vesicles both in vitro and in vivo was demonstrated to be an effective treatment for RA therapy. This work proposes new insights into the folding and hierarchical assembly of glycopeptide mimics, providing an efficient approach for constructing intelligent platforms for drug delivery, disease therapy, and diagnostic applications.

Structurally dynamic self-healable hydrogel cooperatively inhibits intestinal inflammation and promotes mucosal repair for enhanced ulcerative colitis treatment

Hydrogels are a class of biocompatible materials with versatile functions that have been increasing explored for the localized treatment of ulcerative colitis (UC), but various mechanical stimuli may cause premature hydrogel breakage and detachment, impeding their further clinical translation. Here we report a multifunctional mechanically-resilient self-healing hydrogel for effective UC treatment, which is synthesized through the host-guest interaction between dopamine/β-cyclodextrin-modified hyaluronic acid (HA-CD-DA) and amantadine-modified carboxymethyl chitosan (CMCS-AD). The excessive β-CD cavities allow the incorporation of dexamethasone (DEX), while the porous hydrogel network potentiates the encapsulation of basic fibroblast growth factor (bFGF) and L-alanyl-l-glutamine (ALG). DA moieties in HA components allow firm adhesion of the hydrogel to the ulcerative lesions after in-situ implantation, while the reversible host-guest interaction between CD and AD could enhance the persistence of hydrogel. The hydrogel demonstrated favorable biocompatibility and could continuously release DEX to induce M1-to-M2 repolarization of mucosal macrophages through inhibiting the toll-like receptor 4 (TLR4)-nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) axis. Furthermore, the co-delivered bFGF and ALG facilitates the regeneration of ulcerative mucosa and restore its barrier functions to ameliorate UC symptoms. The mechanically resilient hydrogel offers an integrative approach for UC therapy in the clinics.

Yttrium Oxide Nanoparticle-Loaded, Self-Assembled Peptide Gel with Antibacterial, Anti-Inflammatory, and Proangiogenic Properties for Wound Healing

Chronic wounds are a major healthcare challenge owing to their complex healing mechanism and number of impediments to the healing process, like infections, unregulated inflammation, impaired cellular functions, poor angiogenesis, and enhanced protease activity. Current topical care strategies, such as surgical debridement, absorption of exudates, drug-loaded hydrogels for infection and inflammation management, and exogenous supply of growth factors for angiogenesis and cell proliferation, slow the progression of wounds and reduce patient suffering but suffer from low overall cure rates. Therefore, we have developed a proteolytically stable, multifunctional nanoparticle loaded-peptide gel with inherent anti-inflammatory, antibacterial, and pro-angiogenic properties to provide a favorable wound healing milieu by restoring impaired cellular functions. We have fabricated a self-assembled, lauric acid-peptide conjugate gel, LA-LLys-DPhe-LLys-NH2, loaded with yttrium oxide (Y2O3) nanoparticles (NLG). Gel formed a nanofibrous structure, and nanoparticles were passively entrapped within the network. The surface morphology, stability, viscoelastic, and self-healing characteristics of gels were characterized. It showed a high stability against degradation by proteolytic enzymes and highly potent antibacterial activities against E. coli and S. aureus due to the presence of positively charged side chains of lysine in the peptide chain. It also exhibited an excellent antioxidant activity as well as ability to stimulate cell proliferation in murine fibroblast (L929) cells and human umbilical vein endothelial cells (HUVECs). The incorporation of nanoparticles promoted angiogenesis by upregulating pro-angiogenic genes, vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF2), and epidermal growth factor (EGFR), and the gel caused complete wound closure in cells. In summary, the Y2O3 nanoparticle-loaded lauric acid-peptide conjugate gel is able to elicit the desired tissue regeneration responses and, therefore, has a strong potential as a matrix for the treatment of chronic wounds.

Fmoc-diphenylalanine gelating nanoarchitectonics: A simplistic peptide self-assembly to meet complex applications

9-fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF), has been has been extensively explored due to its ultrafast self-assembly kinetics, inherent biocompatibility, tunable physicochemical properties, and especially, the capability of forming self-sustained gels under physiological conditions. Consequently, various methodologies to develop Fmoc-FF gels and their corresponding applications in biomedical and industrial fields have been extensively studied. Herein, we systemically summarize the mechanisms underlying Fmoc-FF self-assembly, discuss the preparation methodologies of Fmoc-FF hydrogels, and then deliberate the properties as well as the diverse applications of Fmoc-FF self-assemblies. Finally, the contemporary shortcomings which limit the development of Fmoc-FF self-assembly are raised and the alternative solutions are proposed, along with future research perspectives.

Development of Polyurethane/Peptide-Based Carriers with Self-Healing Properties

In situ-forming gels with self-assembling and self-healing properties are materials of high interest for various biomedical applications, especially for drug delivery systems and tissue regeneration. The main goal of this research was the development of an innovative gel carrier based on dynamic inter- and intramolecular interactions between amphiphilic polyurethane and peptide structures. The polyurethane architecture was adapted to achieve the desired amphiphilicity for self-assembly into an aqueous solution and to facilitate an array of connections with peptides through physical interactions, such as hydrophobic interactions, dipole-dipole, electrostatic, π–π stacking, or hydrogen bonds. The mechanism of the gelation process and the macromolecular conformation in water were evaluated with DLS, ATR-FTIR, and rheological measurements at room and body temperatures. The DLS measurements revealed a bimodal distribution of small (~30–40 nm) and large (~300–400 nm) hydrodynamic diameters of micelles/aggregates at 25 °C for all samples. The increase in the peptide content led to a monomodal distribution of the peaks at 37 °C (~25 nm for the sample with the highest content of peptide). The sol–gel transition occurs very quickly for all samples (within 20–30 s), but the equilibrium state of the gel structure is reached after 1 h in absence of peptide and required more time as the content of peptide increases. Moreover, this system presented self-healing properties, as was revealed by rheological measurements. In the presence of peptide, the structure recovery after each cycle of deformation is a time-dependent process, the recovery is complete after about 300 s. Thus, the addition of the peptide enhanced the polymer chain entanglement through intermolecular interactions, leading to the preparation of a well-defined gel carrier. Undoubtedly, this type of polyurethane/peptide-based carrier, displaying a sol–gel transition at a biologically relevant temperature and enhanced viscoelastic properties, is of great interest in the development of medical devices for minimally invasive procedures or precision medicine.

Design Considerations, Formulation Approaches, and Strategic Advances of Hydrogel Dressings for Chronic Wound Management

Wound healing is a complex and dynamic physiological process consisting of a series of cellular and molecular events that initiate immediately after a tissue lesion, to reconstruct the skin layer. It is indubitable that patients with chronic wounds, severely infected wounds, or any metabolic disorder of the wound microenvironment always endure severe pain and discomfort that affect their quality of life. It is essential to treat chronic wounds for conserving the physical as well as mental well-being of affected patients and for convalescing to improve their quality of life. For supporting and augmenting the healing process, the selection of pertinent wound dressing is essential. A substantial reduction in healing duration, disability, associated cost, and risk of recurrent infections can be achieved via engineering wound dressings. Hydrogels play a leading role in the path of engineering ideal wound dressings. Hydrogels, comprising water to a large extent, providing a moist environment, being comfortable to patients, and having biocompatible and biodegradable properties, have found their success as suitable wound dressings in the market. The exploitation of hydrogels is increasing perpetually after substantiation of their broader therapeutic actions owing to their resemblance to dermal tissues, their capability to stimulate partial skin regeneration, and their ability to incorporate therapeutic moieties promoting wound healing. This review entails properties of hydrogel supporting wound healing, types of hydrogels, cross-linking mechanisms, design considerations, and formulation strategies of hydrogel engineering. Various categories of hydrogel wound dressing fabricated recently are discussed based on their gel network composition, degradability, and physical and chemical cross-linking mechanisms, which provide an outlook regarding the importance of tailoring the physicochemical properties of hydrogels. The examples of marketed hydrogel wound dressings are also incorporated along with the future perspectives and challenges associated with them.

Synergy of antioxidant and M2 polarization in polyphenol-modified konjac glucomannan dressing for remodeling wound healing microenvironment

Effective skin wound healing and tissue regeneration remain a challenge. Excessive/chronic inflammation inhibits wound healing, leading to scar formation. Herein, we report a wound dressing composed of KGM-GA based on the natural substances konjac glucomannan (KGM) and gallic acid (GA) that accelerates wound healing without any additional drugs. An in vitro study showed that KGM-GA could not only stimulate macrophage polarization to the anti-inflammatory M2 phenotype but also decrease reactive oxygen species (ROS) levels, indicating excellent anti-inflammatory properties. Moreover, in vivo studies of skin wounds demonstrated that the KGM-GA dressing significantly improved wound healing by accelerating wound closure, collagen deposition, and angiogenesis. In addition, it was observed that KGM-GA regulated M2 polarization, reducing the production of intracellular ROS in the wound microenvironment, which was consistent with the in vitro experiments. Therefore, this study designed a multifunctional biomaterial with biological activity, providing a novel dressing for wound healing.

New Hydrogels Based on Agarose/Phytagel and Peptides

Short aromatic peptide derivatives, i.e., peptides or amino acids modified with aromatic groups, such as 9-fluorenylmethoxycarbonyl (Fmoc), can self-assemble into extracellular matrix-like hydrogels due to their nanofibrillar architecture. Among different types of amino acids, lysine (Lys) and glycine (Gly) are involved in multiple physiological processes, being key factors in the proper growth of cells, carnitine production, and collagen formation. The authors have previously successfully presented the possibility of obtaining supramolecular gels based on Fmoc-Lys-Fmoc and short peptides such as Fmoc-Gly-Gly-Gly in order to use them as a substrate for cell cultures. This paper investigates how the introduction of a gelling polymer can influence the properties of the network as well as the compatibility of the resulting materials with different cell types. A series of hydrogel compositions consisting of combinations of Fmoc-Lys-Fmoc and Fmoc-Gly-Gly-Gly with Agarose and Phytagel are thus obtained. All compositions form structured gels as shown by rheological studies and scanning electron microscopy. Fourier transform infrared spectroscopy analysis evidences the formation of H-bonds between the polysaccharides and amino acids or short peptides. Moreover, all gels exhibit good cell viability on fibroblasts as demonstrated by a live-dead staining test and good in vivo biocompatibility, which highlights the great potential of these biomaterials for biomedical applications.

Biomimetic graphene-supported ultrafine platinum nanowires for colorimetric and electrochemical detection of hydrogen peroxide

The detection of hydrogen peroxide (H₂O₂) is of great significance in environmental monitoring, enzymatic reactions, and disease diagnosis. Here we present the peptide-mediated biomimetic synthesis of ultrafine platinum nanowires (PtNWs) on graphene oxide (GO) nanosheets for the formation of functional hybrids, which show high potential for the fabrication of colorimetric and electrochemical sensors for the detection of H₂O₂ with high performance. A multifunctional peptide with the sequence KIIIIKYWYAF was designed to create peptide nanofibers (PNFs) via a controllable self-assembly process, which serves as a bridge between GO nanosheets and PtNWs to form PtNWs-PNFs/GO hybrids. On this basis, a dual-mode sensor platform for both colorimetric and electrochemical sensing of H₂O₂ was fabricated successfully. The obtained results indicate that the synthesized PtNWs-PNFs/GO hybrids could catalyze the decomposition of H₂O₂ to generate ˙OH radicals with a significant current response, and the ˙OH radicals are capable of overoxidizing 3,3',5,5',-tetramethylbenzidine (TMB), producing a blue-colored species with a distinct color change for colorimetric sensing. In addition, due to its high catalytic activity, the fabricated PtNWs-PNFs/GO hybrid-based electrochemical sensor exhibits a wider linear detection range of 0.05 μM-15 mM and a low detection limit of 0.0206 μM, which can be applied to detect H₂O₂ with high selectivity and sensitivity. Our study provides a green and environmentally friendly synthetic strategy for the preparation of biomimetic materials from PtNWs, and the fabricated colorimetric/electrochemical dual-mode H₂O₂ sensor platform will have a great impact in bioanalysis, environmental monitoring, and biomedicine.

Nanoarchitectonics beyond perfect order - not quite perfect but quite useful

Nanoarchitectonics, like architectonics, allows the design and building of structures, but at the nanoscale. Unlike those in architectonics, and even macro-, micro-, and atomic-scale architectonics, the assembled structures at the nanoscale do not always follow the projected design. In fact, they do follow the projected design but only for self-assembly processes producing structures with perfect order. Here, we look at nanoarchitectonics allowing the building of nanostructures without a perfect arrangement of building blocks. Here, fabrication of structures from molecules, polymers, nanoparticles, and nanosheets to polymer brushes, layer-by-layer assembly structures, and hydrogels through self-assembly processes is discussed, where perfect order is not necessarily the aim to be achieved. Both planar substrate and spherical template-based assemblies are discussed, showing the challenging nature of research in this field and the usefulness of such structures for numerous applications, which are also discussed here.

Biomedical Applications of Polyurethane Hydrogels, Polyurethane Aerogels and Polyurethane-Graphene Nanocomposite Materials

BACKGROUND

Increasing new emerging ill-healths have posed therapeutic challenges in modern medicine. Hence polyurethane hydrogels that comprise polyol, copolymer and extender could be prepared from diverse chemical compounds with adjuvants such as ascorbic acid, sorbitol among others. Their mechano-physicochemical properties are functions of their biological activities. Therefore there is need to assess their therapeutic potentials.

METHODS

literature were searched on synthesis and medical uses of polyurethane - hydrogels, polyurethane - aerogels and polyurethane - graphene nanocomposite materials, with a view to identifying their sources, synthesis, mechanical and physiochemical properties, biomedical applications, chirality, and the relevance of Lipinski's rule of five in the synthesis of oral polyurethane nanocomposite materials.

RESULTS

The prepared hydrogels and aerogels could be used as polymer carriers for intradermal, cutaneous and intranasal drugs. They can be fabricated and used as prosthetics. In addition the strength modulus (tensile stress-tensile strain ratio), biodegradability, biocompatibility and non-toxic effects of the polyurethane hydrogels and aerogels are the highly desirable properties. However, body and environmental temperatures may contribute to their instability, hence there is need to improve on the synthesis of aerogels and hydrogels of polyurethane that can last for many years. Alcoholism, diabetes, pyrogenic diseases, mechanical and physical forces, and physiological variability may also reduce the life span of polyurethane aerogels and hydrogels.

CONCLUSION

Synthesis of polyurethane hydrogel-aerogel complex that can be used in complex, rare biomedical cases is of paramount importance. These hydrogels and aerogels may be hydrophobic, hydrophilic, aerophobic-aerophilic or amphiphilic and sometimes lipophilic depending on structural components and the intended biomedical uses. Polyurethane graphene nanocomposite materials are used in the treatment of a myriad of diseases including cancer and bacterial infection.

Co-encapsulation of Egg-White-Derived Peptides (EWDP) and Curcumin within the Polysaccharide-Based Amphiphilic Nanoparticles for Promising Oral Bioavailability Enhancement: Role of EWDP

The comprehensive utilization of food-derived nutraceuticals with different polarities has been extremely restricted by their poor bioavailability and coexistence in a single system. This study aimed to fabricate a self-assembly of amphiphilic nanoparticles (NPs) for the hydrophilic EWDP and hydrophobic curcumin based on the carboxymethyl chitosan (CMCS) shell and γ-cyclodextrin (γ-CD) core. Notably, EWDP could cooperate with CMCS to yield superior colloidal properties with an excellent curcumin aqueous solubility and co-encapsulation capacity (>10%) for the NPs (pH 2.0-7.0). This phenomenon was mainly ascribed to the additional hydrogen-bonding network and hydrophobic interaction introduced by EWDP. Besides, the overall antioxidant activity, bioaccessibility, gastrointestinal stability, and Caco-2 cell absorption properties were significantly improved in the presence of EWDP (>20% increase). Therefore, EWDP could function as both a potential affinity agent and a nutrition enhancer to expand the co-delivery applications for diverse nutraceuticals with promising oral bioavailability enhancement in food and pharmaceutical areas.

Supramolecular Thermo-Contracting Adhesive Hydrogel with Self-Removability Simultaneously Enhancing Noninvasive Wound Closure and MRSA-Infected Wound Healing

Conventional wound closure and dressing are two crucial, time-consuming but isolated principles in wound care. Even though tissue adhesive opens a new era for wound closure, the method and biomaterial that can simultaneously achieve noninvasive wound closure and promote wound healing are highly appreciated. Herein, a novel supramolecular poly(N-isopropylacrylamide) hybrid hydrogel dressing composed of quaternized chitosan-graft-β-cyclodextrin, adenine, and polypyrrole nanotubes via host-guest interaction and hydrogen bonds is developed. The hydrogel demonstrates thermal contraction of 47% remaining area after 2 h at 37 ℃ and tissue adhesion of 5.74 kPa, which are essential for noninvasive wound closure, and multiple mechanical and biological properties including suitable mechanical properties, self-healing, on-demand removal, antioxidant, hemostasis, and photothermal/intrinsic antibacterial activity (higher 99% killing ratio within 5 min after irradiation). In both full-thickness skin incision and excision wound models, the hydrogel reveals significant wound closure after 24 h post-surgery. In acute and methicillin-resistant Staphylococcus aureus-infected wound and photothermal/intrinsic antibacterial activity assays, wounds treated with the hydrogel demonstrate enhanced wound healing with rapid wound closure rate, mild inflammatory response, advanced angiogenesis, and well-arranged collagen fibers. Altogether, the results indicate the hydrogel is promising in synchronously noninvasive wound closure and enhanced wound healing.

Emerging Fabrication Strategies of Hydrogels and Its Applications

Recently, hydrogels have been investigated for the controlled release of bioactive molecules, such as for living cell encapsulation and matrices. Due to their remote controllability and quick response, hydrogels are widely used for various applications, including drug delivery. The rate and extent to which the drugs reach their targets are highly dependent on the carriers used in drug delivery systems; therefore the demand for biodegradable and intelligent carriers is progressively increasing. The biodegradable nature of hydrogel has created much interest for its use in drug delivery systems. The first part of this review focuses on emerging fabrication strategies of hydrogel, including physical and chemical cross-linking, as well as radiation cross-linking. The second part describes the applications of hydrogels in various fields, including drug delivery systems. In the end, an overview of the application of hydrogels prepared from several natural polymers in drug delivery is presented.

Supramolecular Hydrogels: Design Strategies and Contemporary Biomedical Applications

Self-assembly of supramolecular hydrogels is driven by dynamic, non-covalent interactions between molecules. Considerable research effort has been exerted to fabricate and optimise supramolecular hydrogels that display shear-thinning, self-healing, and reversibility, in order to develop materials for biomedical applications. This review provides a detailed overview of the chemistry behind the dynamic physicochemical interactions that sustain hydrogel formation (hydrogen bonding, hydrophobic interactions, ionic interactions, metal-ligand coordination, and host-guest interactions). Novel design strategies and methodologies to create supramolecular hydrogels are highlighted, which offer promise for a wide range of applications, specifically drug delivery, wound healing, tissue engineering and 3D bioprinting. To conclude, future prospects are briefly discussed, and consideration given to the steps required to ultimately bring these biomaterials into clinical settings.

Biodegradable and Injectable Hydrogels in Biomedical Applications

Injectable hydrogels are a unique class of hydrogels that are formed upon injection into living bodies. They possess features of typical hydrogels such as softness, 3D network structures, large contents of water, the ability to load water-soluble substances, and so on. Furthermore, their injectability allows injectable hydrogels to be implanted into living bodies using a syringe in a minimally invasive way. After being loaded with different active substances (drugs, proteins, genes, viruses, cells, etc.), injectable hydrogels have been demonstrated to be potential in many different biomedical applications including controlled release and tissue engineering. However, biodegradability is also an important property of injectable hydrogels and allows removal of the hydrogels after accomplishment of their tasks. In this Perspective, we aim at introducing several different types of biodegradable and injectable hydrogels and compare their differences in properties and applications. Lastly, we also point out some remaining problems and future trends in the field of biodegradable and injectable hydrogels.

Recent Advances and Biomedical Applications of Peptide-Integrated Conducting Polymers

Conducting polymers (CPs) are of great interests to researchers around the world in biomedical applications owing to their unique electrical and mechanical properties. Besides, they are easy to fabricate and have long-term stability. These features make CPs a powerful building block of modern biomaterials. Peptide functionalization has been a versatile tool for the development of CP-based biomaterials. With the aid of peptide modifications, the biocompatibility, target selectivity, and cellular interactions of CPs can be greatly improved. Reflecting these aspects, an increasing number of studies on peptide-integrated conducting polymers have been reported recently. In this review, various kinds of peptide immobilization strategies on CPs are introduced. Moreover, the aims of peptide modification are discussed in three aspects: enhancing the specific selectivity, avoiding nonspecific adhesion, and mimicking the environment of extracellular matrix. We highlighted recent studies in the applications of peptide-integrated CPs in electrochemical sensors, antifouling surfaces, and conductive biointerfaces. These studies have shown great potentials from the integration of peptide and CPs as a versatile platform for advanced biological and clinical applications in the near future.

Ultrashort Peptides and Hyaluronic Acid-Based Injectable Composite Hydrogels for Sustained Drug Release and Chronic Diabetic Wound Healing

Peptide hydrogels are widely used for biomedical applications owing to their good biocompatibility and unique advantages in terms of amino acid-based structures and functions. However, the exploration of the peptide/saccharide composite hydrogels as potential biomaterials for chronic diabetic wound healing is still limited. Herein, hyaluronic acid (HA) was incorporated into diphenylalanine (FF) conjugated with different aromatic moieties by a one-pot reaction. Our results showed that the dipeptide derivatives modified by benzene (B), naphthalene (N), and pyrene (P) self-assembled into composite hydrogels with uniform distribution and good mechanical properties in the presence of HA. The obtained N-FF/HA composite hydrogel exhibited greatly improved self-healing properties via injection syringe needle operation and good biocompatibility on human skin fibroblast (HSF) cells. Besides, the structure of thinner nanofibers and honeycomb networks inside the composite hydrogel allowed for a longer sustained release of curcumin, a hydrophobic drug for anti-inflammation and wound healing. The curcumin-loaded N-FF/HA composite hydrogels could promote chronic wound healing in the streptozotocin-induced type I diabetic mouse model. The results suggested that our developed saccharide-peptide hydrogels could serve as very promising synthetic biomaterials for applications in both drug delivery and wound healing in the future.

Rational synthesis of Three-Layered plasmonic nanocomposites of copper Sulfide/Gold/Zinc-Doped Prussian blue analogues for improved photothermal disinfection and wound healing

Bacteria-infected wounds have imposed serious challenges in human health whereas the abuse of antibiotics makes bacteria drug-resistant and becoming more and more difficult to deal with. Herein, we developed a drug-free three-layered photothermal bactericide from inside to outside consisting of copper sulfide (CuS), gold (Au) and zinc-doped Prussian blue analogues (ZnPBA) (named as CuS@Au@ZnPBA). The CuS@Au@ZnPBA was demonstrated to possess remarkably-improved photothermal property and excellent biosafety. Local heat generated by CuS@Au@ZnPBA under the irradiation of 808 nm laser enables efficient bacteria ablation in vitro and in a mouse model of cutaneous wound infection. Meanwhile, the released zinc ions (Zn²⁺) could upregulate the genes involved in collagen deposition to accelerate wound healing. Overall, the finely-designed nanocomposites can serve as a promising kind of antibacterial alternative to current antibiotic therapies against bacterial wound infections.

A self-assembled amphiphilic polysaccharide-based co-delivery system for egg white derived peptides and curcumin with oral bioavailability enhancement

Egg white derived peptides (EWDP) and curcumin are well known for diverse biological activities, but the combinational usage of the two natural nutraceuticals is extremely limited by their low oral bioavailability and distinctly different polarities. Therefore, this study aimed to exploit a facile self-assembled amphiphilic system for oral co-delivery of hydrophilic egg white derived peptides (EWDP) and hydrophobic curcumin. The hydrophobic curcumin was first loaded into the hydrophobic cavity of β-cyclodextrin (β-CD) as a core. Then, the hydrophilic EWDP was absorbed into the region between the core and the N-[(2-hydroxy-3-trimethyl ammonium) propyl] chitosan (HTCC) shell to form the amphiphilic nanoparticles (NPs) via layer-by-layer self-assembly. The resulting NPs showed ideal oral applicability with excellent colloidal properties and encapsulation capacity for EWDP and curcumin at pH 2.0-7.0. X-ray Photoelectron Spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (¹H NMR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) results indicated that hydrogen bonding and hydrophobic interaction were the main driving force for the formation of amphiphilic NPs. Upon combination with HTCC, EWDP (both shell material and core nutraceuticals) could facilitate curcumin loading into the deeper β-CD cavity site with admirable solubility improvement. Moreover, EWDP and curcumin after co-delivery exhibited superior bioavailability (especially for bioactivity and cellular absorption) than the simple mixture and conventional curcumin inclusion complex. Overall, these findings are enlightening for the rational peptide based oral co-delivery system formulations for a broader range of hydrophilic and hydrophobic nutraceuticals (initially synergistic or not) in the food and related health-promoting fields.

Peptide-Polydopamine Nanocomposite Hydrogel for a Laser-Controlled Hydrophobic Drug Delivery

Smart antibacterial systems, delivering antimicrobials in a highly controlled manner, are one strategy toward fighting the rise of antibiotic-resistant pathogens. Here, we engineer a laser-responsive antimicrobial nanocomposite hydrogel combining a peptide amphiphile and a photothermally active polydopamine nanoparticle (PDNP) to entrap the hydrophobic rifampicin within the hydrophilic hydrogel matrix. We show that the ability of the gelator to interact and retain rifampicin within the gel induced structural changes in its nanofiber network and mechanical properties. Furthermore, PDNP inclusion enabled laser-induced drug release, preventing growth of a Gram-negative E. coli. Overall, our work provides a significant advance in designing smart materials for controlled drug delivery applications.

Functional Hydrogels as Wound Dressing to Enhance Wound Healing

Hydrogels, due to their excellent biochemical and mechnical property, have shown attractive advantages in the field of wound dressings. However, a comprehensive review of the functional hydrogel as a wound dressing is still lacking. This work first summarizes the skin wound healing process and relates evaluation parameters and then reviews the advanced functions of hydrogel dressings such as antimicrobial property, adhesion and hemostasis, anti-inflammatory and anti-oxidation, substance delivery, self-healing, stimulus response, conductivity, and the recently emerged wound monitoring feature, and the strategies adopted to achieve these functions are all classified and discussed. Furthermore, applications of hydrogel wound dressing for the treatment of different types of wounds such as incisional wound and the excisional wound are summarized. Chronic wounds are also mentioned, and the focus of attention on infected wounds, burn wounds, and diabetic wounds is discussed. Finally, the future directions of hydrogel wound dressings for wound healing are further proposed.

Antimicrobial Peptides: The Promising Therapeutics for Cutaneous Wound Healing

Chronic wound infections have caused an increasing number of deaths and economic burden, which necessitates wound treatment options. Hitherto, the development of functional wound dressings has achieved reasonable progress. Antibacterial agents, growth factors, and miRNAs are incorporated in different wound dressings to treat various types of wounds. As an effective antimicrobial agent and emerging wound healing therapeutic, antimicrobial peptides (AMPs) have attracted significant attention. The present study focuses on the application of AMPs in wound healing and discusses the types, properties and formulation strategies of AMPs used for wound healing. In addition, the clinical trial and the current status of studies on "antimicrobial peptides and wound healing" are elaborated through bibliometrics. Also, the challenges and opportunities for further development and utilization of AMP formulations in wound healing are discussed.