Adhesive Hemostatic Conducting Injectable Composite Hydrogels with Sustained Drug Release and Photothermal Antibacterial Activity to Promote Full‐Thickness Skin Regeneration During Wound Healing

Developing injectable nanocomposite conductive hydrogel dressings with multifunctions including adhesiveness, antibacterial, and radical scavenging ability and good mechanical property to enhance full‐thickness skin wound regeneration is highly desirable in clinical application. Herein, a series of adhesive hemostatic antioxidant conductive photothermal antibacterial hydrogels based on hyaluronic acid‐graft‐dopamine and reduced graphene oxide (rGO) using a H₂O₂/HPR (horseradish peroxidase) system are prepared for wound dressing. These hydrogels exhibit high swelling, degradability, tunable rheological property, and similar or superior mechanical properties to human skin. The polydopamine endowed antioxidant activity, tissue adhesiveness and hemostatic ability, self‐healing ability, conductivity, and NIR irradiation enhanced in vivo antibacterial behavior of the hydrogels are investigated. Moreover, drug release and zone of inhibition tests confirm sustained drug release capacity of the hydrogels. Furthermore, the hydrogel dressings significantly enhance vascularization by upregulating growth factor expression of CD31 and improve the granulation tissue thickness and collagen deposition, all of which promote wound closure and contribute to a better therapeutic effect than the commercial Tegaderm films group in a mouse full‐thickness wounds model. In summary, these adhesive hemostatic antioxidative conductive hydrogels with sustained drug release property to promote complete skin regeneration are an excellent wound dressing for full‐thickness skin repair.     

Development of nanotechnology for advancement and application in wound healing: a review

Wound healing is a series of different dynamic and complex phenomena. Many studies have been carried out based on the type and severity of wounds. However, to recover wounds faster there are no suitable drugs available, which are highly stable, less expensive as well as has no side effects. Nanomaterials have been proven to be the most promising agent for faster wound healing among all the other wound healing materials. This review briefly discusses the recent developments of wound healing by nanotechnology, their applicability and advantages. Nanomaterials have unique physicochemical, optical, and biological properties. Some of them can be directly applied for wound healing or some of them can be incorporated into scaffolds to create hydrogel matrix or nanocomposites, which promote wound healing through their antimicrobial, as well as selective anti‐ and pro‐inflammatory, and proangiogenic properties. Owing to their high surface area to volume ratio, nanomaterials have not only been used for drug delivery vectors but also can affect wound healing by influencing collagen deposition and realignment and provide approaches for skin tissue regeneration.Inspec keywords: skin, wounds, cellular biophysics, drug delivery systems, tissue engineering, hydrogels, nanocomposites, proteins, nanomedicineOther keywords: wound healing materials, nanomaterials, nanotechnology, proangiogenic properties, proinflammatory properties, collagen deposition, drug delivery vectors, skin tissue regeneration     

Circulating Exosomal miR‐20b‐5p Inhibition Restores Wnt9b Signaling and Reverses Diabetes‐Associated Impaired Wound Healing

At present, developing therapeutic strategies to improve wound healing in individuals with diabetes remains challenging. Exosomes represent a promising nanomaterial from which microRNAs (miRNAs) can be isolated. These miRNAs have the potential to exert therapeutic effects, and thus, determining the potential therapeutic contributions of specific miRNAs circulating in exosomes is of great importance. In the present study, circulating exosomal miRNAs are identified in diabetic patients and assessed for their roles in the context of diabetic wound healing. A significant upregulation of miR‐20b‐5p is observed in exosomes isolated from patients with type 2 diabetes mellitus (T2DM), and this miRNA is able to suppress human umbilical vein endothelial cell angiogenesis via regulation of Wnt9b/β‐catenin signaling. It is found that the application of either miR‐20b‐5p or diabetic exosomes to wound sites is sufficient to slow wound healing and angiogenesis. In diabetic mice, it is found that knocking out miR‐20b‐5p significantly enhances wound healing and promotes wound angiogenesis. Together, these findings thus provide strong evidence that miR‐20b‐5p is highly enriched in exosomes from patients with T2DM and can be transferred to cells of the vascular endothelium, where it targets Wnt9b signaling to negatively regulate cell functionality and angiogenesis.     

Smart Bandage for Monitoring and Treatment of Chronic Wounds

Chronic wounds are a major health concern and they affect the lives of more than 25 million people in the United States. They are susceptible to infection and are the leading cause of nontraumatic limb amputations worldwide. The wound environment is dynamic, but their healing rate can be enhanced by administration of therapies at the right time. This approach requires real‐time monitoring of the wound environment with on‐demand drug delivery in a closed‐loop manner. In this paper, a smart and automated flexible wound dressing with temperature and pH sensors integrated onto flexible bandages that monitor wound status in real‐time to address this unmet medical need is presented. Moreover, a stimuli‐responsive drug releasing system comprising of a hydrogel loaded with thermo‐responsive drug carriers and an electronically controlled flexible heater is also integrated into the wound dressing to release the drugs on‐demand. The dressing is equipped with a microcontroller to process the data measured by the sensors and to program the drug release protocol for individualized treatment. This flexible smart wound dressing has the potential to significantly impact the treatment of chronic wounds.     

CSF1R‐ and SHP2‐Inhibitor‐Loaded Nanoparticles Enhance Cytotoxic Activity and Phagocytosis in Tumor‐Associated Macrophages

Immune modulation of macrophages has emerged as an attractive approach for anti‐cancer therapy. However, there are two main challenges in successfully utilizing macrophages for immunotherapy. First, macrophage colony stimulating factor (MCSF) secreted by cancer cells binds to colony stimulating factor 1 receptor (CSF1‐R) on macrophages and in turn activates the downstream signaling pathway responsible for polarization of tumor‐associated macrophages (TAMs) to immunosuppressive M2 phenotype. Second, ligation of signal regulatory protein α (SIRPα) expressed on myeloid cells to CD47, a transmembrane protein overexpressed on cancer cells, activates the Src homology region 2 (SH2) domain ‐phosphatases SHP‐1 and SHP‐2 in macrophages. This results in activation of “eat‐me‐not” signaling pathway and inhibition of phagocytosis. Here, it is reported that self‐assembled dual‐inhibitor‐loaded nanoparticles (DNTs) target M2 macrophages and simultaneously inhibit CSF1R and SHP2 pathways. This results in efficient repolarization of M2 macrophages to an active M1 phenotype, and superior phagocytic capabilities as compared to individual drug treatments. Furthermore, suboptimal dose administration of DNTs in highly aggressive breast cancer and melanoma mouse models show enhanced anti‐tumor efficacy without any toxicity. These studies demonstrate that the concurrent inhibition of CSF1‐R and SHP2 signaling pathways for macrophage activation and phagocytosis enhancement could be an effective strategy for macrophage‐based immunotherapy.     

Dextran-based hydrogel containing chitosan microparticles loaded with growth factors to be used in wound healing

Skin injuries are traumatic events, which are seldom accompanied by complete structural and functional restoration of the original tissue. Different strategies have been developed in order to make the wound healing process faster and less painful. In the present study in vitro and in vivo assays were carried out to evaluate the applicability of a dextran hydrogel loaded with chitosan microparticles containing epidermal and vascular endothelial growth factors, for the improvement of the wound healing process. The carriers' morphology was characterized by scanning electron microscopy. Their cytotoxicity profile and degradation by-products were evaluated through in vitro assays. In vivo experiments were also performed to evaluate their applicability for the treatment of skin burns. The wound healing process was monitored through macroscopic and histological analysis. The macroscopic analysis showed that the period for wound healing occurs in animals treated with microparticle loaded hydrogels containing growth factors that were considerably smaller than that of control groups. Moreover, the histological analysis revealed the absence of reactive or granulomatous inflammatory reaction in skin lesions. The results obtained both in vitro and in vivo disclosed that these systems and its degradation by-products are biocompatible, contributed to the re-establishment of skin architecture and can be used in a near future for the controlled delivery of other bioactive agents used in regenerative medicine.     

Nanozyme-Based Supramolecular Self-Assembly As an Artificial Host Defense System For Treatment of Bacterial Infections

The proper functioning of host defense system (HDS) is the key to combating bacterial infection in biological organisms. However, the delicate HDS may be dysfunctional or dysregulated, resulting in persistent infection, tissue damage, or delayed wound healing. Herein, a powerful artificial “host defense system” (aHDS) is designed and constructed for treatment of bacterial infections. First, the aHDS can quickly trap the bacteria by electrostatic interactions. Next, the system can be stimulated to produce large amounts of cytotoxic reactive oxygen species (ROS) and exert strong antibacterial effects, which can further regulate the immune microenvironment, leading to macrophage polarization from M0 to pro-inflammatory phenotype (M1) for synergistic bacteria killing. At the later stages, the system can exhibit excellent antioxidant enzyme-like activities to reprogram the M1 macrophage to anti-inflammatory phenotype (M2) for accelerating wound healing. This powerful aHDS can effectively combat the bacteria and avoid excessive inflammatory responses for the treatment of bacteria-infected wounds.     

Assessment of reinforced poly(ethylene glycol) chitosan hydrogels as dressings in a mouse skin wound defect model

Wound dressings of chitosan are biocompatible, biodegradable, antibacterial and hemostatic biomaterials. However, applications for chitosan are limited due to its poor mechanical properties. Here, we conducted an in vivo mouse angiogenesis study on reinforced poly(ethylene glycol) (PEG)-chitosan (RPC) hydrogels. RPC hydrogels were formed by cross-linking chitosan with PEGs of different molecular weights at various PEG to chitosan ratios in our previous paper. These dressings can keep the wound moist, had good gas exchange capacity, and was capable of absorbing or removing the wound exudate. We examined the ability of these RPC hydrogels and neat chitosan to heal small cuts and full-thickness skin defects on the backs of male Balb/c mice. Histological examination revealed that chitosan suppressed the infiltration of inflammatory cells and accelerated fibroblast proliferation, while PEG enhanced epithelial migration. The RPC hydrogels promoted wound healing in the small cuts and full layer wounds. The optimal RPC hydrogel had a swelling ratio of 100% and a water vapor transmission rate (WVTR) of about 2000 g/m²/day. In addition, they possess good mechanical property and appropriate degradation rates. Thus, the optimal RPC hydrogel formulation functioned effectively as a wound dressing and promoted wound healing.     

Immune Cell‐Mediated Biodegradable Theranostic Nanoparticles for Melanoma Targeting and Drug Delivery

Although tremendous efforts have been made on targeted drug delivery systems, current therapy outcomes still suffer from low circulating time and limited targeting efficiency. The integration of cell‐mediated drug delivery and theranostic nanomedicine can potentially improve cancer management in both therapeutic and diagnostic applications. By taking advantage of innate immune cell's ability to target tumor cells, the authors develop a novel drug delivery system by using macrophages as both nanoparticle (NP) carriers and navigators to achieve cancer‐specific drug delivery. Theranostic NPs are fabricated from a unique polymer, biodegradable photoluminescent poly (lactic acid) (BPLP‐PLA), which possesses strong fluorescence, biodegradability, and cytocompatibility. In order to minimize the toxicity of cancer drugs to immune cells and other healthy cells, an anti‐BRAF V600E mutant melanoma specific drug (PLX4032) is loaded into BPLP‐PLA nanoparticles. Muramyl tripeptide is also conjugated onto the nanoparticles to improve the nanoparticle loading efficiency. The resulting nanoparticles are internalized within macrophages, which are tracked via the intrinsic fluorescence of BPLP‐PLA. Macrophages carrying nanoparticles deliver drugs to melanoma cells via cell–cell binding. Pharmacological studies also indicate that the PLX4032 loaded nanoparticles effectively kill melanoma cells. The “self‐powered” immune cell‐mediated drug delivery system demonstrates a potentially significant advancement in targeted theranostic cancer nanotechnologies.     

Influence of radiation crosslinked carboxymethyl-chitosan/gelatin hydrogel on cutaneous wound healing

A series of carboxymethyl chitosan (CM-chitosan) and gelatin hydrogels were prepared by radiation crosslinking. A pre-clinical study was performed by implantation model and full-thickness cutaneous wound model in Sprague–Dawley rats to preliminarily evaluate the biocompatibility, biodegradability and effects on healing. In the implantation test, as a component of the hydrogels, CM-chitosan showed a positive effect on promoting cell proliferation and neovascularization, while gelatin was efficient to stabilize the structure and prolong the degradation time. To evaluate the function on wound healing, the hydrogels were applied to the relatively large full-thickness cutaneous wounds (Φ3.0 cm). Compared with the control groups, the hydrogel group showed significantly higher percentage of wound closure on days 9, 12 and 15 postoperatively, which was consistent with the significantly thicker granulation tissue on days 3 and 6. All results apparently revealed that the radiation crosslinked CM-chitosan/Gelatin hydrogels could induce granulation tissue formation and accelerate the wound healing.     

Moisture-Adaptive Contractile Biopolymer-Derived Fibers for Wound Healing Promotion

The advancement in thermosensitive active hydrogels has opened promising opportunities to dynamic full-thickness skin wound healing. However, conventional hydrogels lack breathability to avoid wound infection and cannot adapt to wounds with different shapes due to the isotropic contraction. Herein, a moisture-adaptive fiber that rapidly absorbs wound tissue fluid and produces a large lengthwise contractile force during the drying process is reported. The incorporation of hydroxyl-rich silica nanoparticles in the sodium alginate/gelatin composite fiber greatly improves the hydrophilicity, toughness, and axial contraction performance of the fiber. This fiber exhibits a dynamic contractile behavior as a function of humidity, generating ≈15% maximum contraction strain or ≈24 MPa maximum isometric contractile stress. The textile knitted by the fibers features excellent breathability and generates adaptive contraction in the target direction during the natural desorption of tissue fluid from the wounds. In vivo animal experiments further demonstrate the advantages of the textiles over traditional dressings in accelerating wound healing.     

A Self‐Pumping Dressing for Draining Excessive Biofluid around Wounds

Excessive biofluid around wounds often causes infection and hinders wound healing. However, the intrinsic hydrophilicity of the conventional dressing inevitably retains excessive biofluid at the interface between the dressing and the wound. Herein, a self‐pumping dressing is reported, by electrospinning a hydrophobic nanofiber array onto a hydrophilic microfiber network, which can unidirectionally drain excessive biofluid away from wounds and finally accelerate the wound healing process. The hydrophilic microfiber network offers a draining force to pump excessive biofluid through the hydrophobic nanofiber array, which can further keep those pumped biofluids from rewetting the wounds. In the proof of concept, the self‐pumping dressing unidirectionally drains the biofluid from murine dorsum wounds, thereby resulting in faster wound healing than conventional dressings. This unique self‐pumping dressing has enormous potential to be a next‐generation dressing for healing wounds clinically.     

Adipose‐Derived Biogenic Nanoparticles for Suppression of Inflammation

Extracellular vesicles secreted from adipose‐derived mesenchymal stem cells (ADSCs) have therapeutic effects in inflammatory diseases. However, production of extracellular vesicles (EVs) from ADSCs is costly, inefficient, and time consuming. The anti‐inflammatory properties of adipose tissue‐derived EVs and other biogenic nanoparticles have not been explored. In this study, biogenic nanoparticles are obtained directly from lipoaspirate, an easily accessible and abundant source of biological material. Compared to ADSC‐EVs, lipoaspirate nanoparticles (Lipo‐NPs) take less time to process (hours compared to months) and cost less to produce (clinical‐grade cell culture facilities are not required). The physicochemical characteristics and anti‐inflammatory properties of Lipo‐NPs are evaluated and compared to those of patient‐matched ADSC‐EVs. Moreover, guanabenz loading in Lipo‐NPs is evaluated for enhanced anti‐inflammatory effects. Apolipoprotein E and glycerolipids are enriched in Lipo‐NPs compared to ADSC‐EVs. Additionally, the uptake of Lipo‐NPs in hepatocytes and macrophages is higher. Lipo‐NPs and ADSC‐EVs have comparable protective and anti‐inflammatory effects. Specifically, Lipo‐NPs reduce toll‐like receptor 4‐induced secretion of inflammatory cytokines in macrophages. Guanabenz‐loaded Lipo‐NPs further suppress inflammatory pathways, suggesting that this combination therapy can have promising applications for inflammatory diseases.     

Smart Magnetic Fluorescent Nanoparticle Imaging Probes to Monitor MicroRNAs

An imaging system that can be used to evaluate the expression levels of microRNAs during neuronal development can provide noninvasive information for investigating a variety of biological phenomena related to microRNAs (miRNAs, miRs). Herein, the development of a novel imaging platform to monitor intracellular miR124a during neuronal differentiation is reported using rhodamine‐coated cobalt ferrite magnetic fluorescent (MF) nanoparticles linked to a quenching molecular system containing an miR124a binding sequence (MF‐miR124a beacon). During neuronal differentiation, in vitro fluorescence signals of the MF‐miR124a beacon are significantly increased under conditions where miR124a is highly expressed, and dramatically return to the original quenched fluorescence after anti‐miR124a treatment. In vivo fluorescence images show enhanced fluorescence signals in mice with P19 cells within a poly‐L ‐lactic acid scaffold after induction of neuronal differentiation. In addition, magnetic resonance (MR) images provide in vivo tracking of cells containing the MF‐miR124a beacon. These studies represent the first step toward the use of nanotechnological imaging of mature miRNA, and this technique could be used for cellular tracking with a MR imaging system as well as for simultaneous monitoring of the miRNA expression pattern in vivo.     

Microalgae-Based Biohybrid Microrobot for Accelerated Diabetic Wound Healing

A variety of wound healing platforms have been proposed to alleviate the hypoxic condition and/or to modulate the immune responses for the treatment of chronic wounds in diabetes. However, these platforms with the passive diffusion of therapeutic agents through the blood clot result in the relatively low delivery efficiency into the deep wound site. Here, a microalgae-based biohybrid microrobot for accelerated diabetic wound healing is developed. The biohybrid microrobot autonomously moves at velocity of 33.3 µm s⁻¹ and generates oxygen for the alleviation of hypoxic condition. In addition, the microrobot efficiently bound with inflammatory chemokines of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) for modulating the immune responses. The enhanced penetration of microrobot is corroborated by measuring fibrin clots in biomimetic wound using microfluidic devices and the enhanced retention of microrobot is confirmed in the real wounded mouse skin tissue. After deposition on the chronic wound in diabetic mice without wound dressing, the wounds treated with microrobots are completely healed after 9 days with the significant decrease of inflammatory cytokines below 31% of the control level and the upregulated angiogenesis above 20 times of CD31⁺ cells. These results confirm the feasibility of microrobots as a next-generation platform for diabetic wound healing.     

Recent trends in metal ion based hydrogel biomaterials for tissue engineering and other biomedical applications

Recently,the metal ion cross-linked hydrogels have gained enormous interest because of its excellent properties like self-healing,fast recovery,biocompatibility and high mechanical properties combined with multi-stimuli responsiveness.In this review article,we have summarized the recent trends in the development of metal ion cross-linked hydrogels for tissue engineering and biomedical applications.A number of metal ions and their contribution in the synthesis of various cross-linked hydrogels are discussed with respect to their crosslinking mechanisms,compositions,physio-chemical and biological properties.A special emphasis has been given to ferric(Fe³⁺)ion cross-linked hydrogels and their different combinations owing to their numerous researches reported in the recent past with exceptional properties.The application of these metal ion based hydrogels in biomedical applications including tissue engineering,sensing,wound healing,drug delivery and as tissue adhesive and tissue sealants are reviewed with specific examples.Importantly,the application of these metal ion cross-linked hydrogels as inks in 3 D printing is explained in a separate section.Finally,the possible toxic effects of the different metal ions and their effects have been scrutinized.Future directions and comprehensive applications of the hydrogels are highlighted.     

Small extracellular vesicles secreted by urine-derived stem cells enhanced wound healing in aged mice by ameliorating cellular senescence

Regeneration of chronic skin wounds in tissue is still a key challenge in regenerative medicine because of the accumulation of senescent cells and increasing secretion of s¨enescence-associated secretory phenotype(SASP)in the wound site.Recently,some studies have reported that small extracellular vesicles(sEVs)derived from stem cells can alleviate cellular senescence with very low risk of tumorigenesis and immune responses.As our previous studies have shown that urine-derived stem cells(USCs)can be obtained easily and noninvasively and sEVs derived from USCs(USC-sEVs)have capabilities of regenerating tissue injuries,using USC-sEVs to enhance chronic skin wound healing in aged tissue might be a feasible and efficient strategy.Therefore,in this study,the USC-sEVs were collected and firstly loaded in a human acellular amniotic membrane(HAAM)for controlled releasing and locating the USC-sEVs in the wound site before they were implanted into a chronic skin wound in aged mice.In vivo results showed that the USC-sEVs in HAAM could effectively accelerate the wound healing by ameliorating cellular senescence and reducing the secretion of SASP in the aged skin wounds.To elucidate the mechanism,USC-sEVs were used to in vitro culture human dermal fibroblasts(HDFs)and results showed that USC-sEVs could rejuvenate senescent fibroblasts by reversing the aging phenotypes of senescent HDFs and efficiently reducing the secretion of SASP after they activated the Sirt1 pathway.Therefore,USC-sEVs are efficient for enhancing wound healing in aged mice by ameliorating cellular senescence.     

Glycocalyx‐Mimicking Nanoparticles for Stimulation and Polarization of Macrophages via Specific Interactions

Malignant tumors develop multiple mechanisms to impair and escape from antitumor immune responses, of which tumor‐associated macrophages that often show immunosuppressive phenotype (M2), play a critical role in tumor‐induced immunosuppression. Therefore, strategies that can reverse M2 phenotype and even enhance immune‐stimulation function of macrophage would benefit tumor immunotherapy. In this paper, self‐assembled glyco‐nanoparticles (glyco‐NPs), as artificial glycocalyx, have been found to be able to successfully induce the polarization of mouse primary peritoneal macrophages from M2 to inflammatory type (M1). The polarization change was evidenced by the decreased expression of cell surface signaling molecules CD206 and CD23, and the increased expression of CD86. Meanwhile, secretion of cytokines supported this polarization change as well. More importantly, this phenomenon is observed not only in vitro, but also in vivo. As far as we known, this is the first report about macrophage polarization being induced by synthetic nanomaterials. Moreover, preparation, characterization of these glyco‐NPs and their interaction with the macrophages are also demonstrated.     

On-Demand Removable Self-Healing and pH-Responsive Europium-Releasing Adhesive Dressing Enables Inflammatory Microenvironment Modulation and Angiogenesis for Diabetic Wound Healing

Current diabetic wound treatments remain unsatisfactory due to the lack of a comprehensive strategy that can integrate strong applicability (tissue adhesiveness, shape adaptability, fast self-healability, and facile dressing change) with the initiation and smooth connection of the cascade wound healing processes. Herein, benefiting from the multifaceted bonding ability of tannic acid to metal ions and various polymers, a family of tannin–europium coordination complex crosslinked citrate-based mussel-inspired bioadhesives (TE-CMBAs) are specially developed for diabetic wound healing. TE-CMBAs can gel instantly (< 60 s), possess favorable shape-adaptability, considerable mechanical strengths, high elasticity, considerable wet tissue adhesiveness (≈40 kPa), favorable photothermal antimicrobial activity, excellent anti-oxidant activity, biocompatibility, and angiogenetic property. The reversible hydrogen bond crosslinking and sensitive metal–phenolic coordination also confers TE-CMBAs with self-healability, pH-responsive europium ion and TA releasing properties and on-demand removability upon mixing with borax solution, enabling convenient painless dressing change and the smooth connection of inflammatory microenvironment modulation, angiogenesis promotion, and effective extracellular matrix production leveraging the acidic pH condition of diabetic wounds. This adhesive dressing provides a comprehensive regenerative strategy for diabetic wound management and can be extended to other complicated tissue healing scenarios.