In situ formed anti-inflammatory hydrogel loading plasmid DNA encoding VEGF for burn wound healing

Growth Factor Binding Peptides in Poly (Ethylene Glycol) Diacrylate (PEGDA)-Based Hydrogels for an Improved Healing Response of Human Dermal Fibroblasts

Growth factors (GF) are critical cytokines in wound healing. However, the direct delivery of these biochemical cues into a wound site significantly increases the cost of wound dressings and can lead to a strong immunological response due to the introduction of a foreign source of GFs. To overcome this challenge, we designed a poly(ethylene glycol) diacrylate (PEGDA) hydrogel with the potential capacity to sequester autologous GFs directly from the wound site. We demonstrated that synthetic peptide sequences covalently tethered to PEGDA hydrogels physically retained human transforming growth factor beta 1 (hTGFβ1) and human vascular endothelial growth factor (hVEGF) at 3.2 and 0.6 ng/mm², respectively. In addition, we demonstrated that retained hTGFβ1 and hVEGF enhanced human dermal fibroblasts (HDFa) average cell surface area and proliferation, respectively, and that exposure to both GFs resulted in up to 1.9-fold higher fraction of area covered relative to the control. After five days in culture, relative to the control surface, non-covalently bound hTGFβ1 significantly increased the expression of collagen type I and hTGFβ1 and downregulated vimentin and matrix metalloproteinase 1 expression. Cumulatively, the response of HDFa to hTGFβ1 aligns well with the expected response of fibroblasts during the early stages of wound healing.

Current Progress and Outlook of Nano-Based Hydrogel Dressings for Wound Healing

Wound dressing is an important tool for wound management. Designing wound dressings by combining various novel materials and drugs to optimize the peri-wound environment and promote wound healing is a novel concept. Hydrogels feature good ductility, high water content, and favorable oxygen transport, which makes them become some of the most promising materials for wound dressings. In addition, nanomaterials exhibit superior biodegradability, biocompatibility, and colloidal stability in wound healing and can play a role in promoting healing through their nanoscale properties or as carriers of other drugs. By combining the advantages of both technologies, several outstanding and efficient wound dressings have been developed. In this paper, we classify nano-based hydrogel dressings into four categories: hydrogel dressings loaded with a nanoantibacterial drug; hydrogel dressings loaded with oxygen-delivering nanomedicines; hydrogel dressings loaded with nanonucleic acid drugs; and hydrogel dressings loaded with other nanodelivered drugs. The design ideas, advantages, and challenges of these nano-based hydrogel wound dressings are reviewed and analyzed. Finally, we envisaged possible future directions for wound dressings in the context of relevant scientific and technological advances, which we hope will inform further research in wound management.

Engineering functional natural polymer-based nanocomposite hydrogels for wound healing

Skin injury occurs due to acute trauma, chronic trauma, infection, and surgical intervention, which can result in severe dysfunction and even death in humans. Therefore, clinical intervention is critical for the treatment of skin wounds. One idealized method is to use wound dressings to protect skin wounds and promote wound healing. Among these wound dressings, nanocomposite natural polymer hydrogels (NNPHs) are multifunctional wound dressings for wound healing. The combination of nanomaterials and natural polymer hydrogels avoids the shortcomings of a single component. Moreover, nanomaterials could provide improved antibacterial, anti-inflammatory, antioxidant, stimuli-responsive, electrically conductive and mechanical properties of hydrogels to accelerate wound healing. This review focuses on recent advancements in NNPHs for skin wound healing and repair. Initially, the functions and requirements of NNPHs as wound dressings were introduced. Second, the design, preparation and capacities of representative NNPHs are classified based on their nanomaterial. Third, skin wound repair applications of NNPHs have been summarized based on the types of wounds. Finally, the potential issues of NNPHs are discussed, and future research is proposed to prepare idealized multifunctional NNPHs for skin tissue regeneration.

Potential use of bioactive nanofibrous dural substitutes with controlled release of IGF-1 for neuroprotection after traumatic brain injury

For patients suffering from traumatic brain injury (TBI), the closure of dural defects after decompressive craniectomy is the prerequisite to restoring normal physiological functions. It is also an urgent challenge to provide a neuroprotection effect against the primary and secondary nerve damage during long-term recovery. To solve these issues, we herein develop a class of bioactive, nanofibrous dural substitutes that can long-term release insulin-like growth factor 1 (IGF-1) for improving the survival and neurite outgrowth of neural cells after TBI. Such dural substitutes were polycaprolactone (PCL) nanofibers encapsulated with hyaluronic acid methacryloyl (HAMA)/IGF-1 by blend or coaxial electrospinning techniques, achieving bioactive PCL/HAMA/IGF nanofibrous dural substitutes with different release profiles of IGF-1. The nanofibrous dural substitutes exhibited good mechanical properties and hydrophobicity, which prevent cerebrospinal fluid leakage, maintain normal intracranial pressure, and avoid external impact on the brain. We also found that the viability and neurite outgrowth of SH-SY5Y cells and primary neurons were significantly enhanced after neurite transection or oxygen and glucose deprivation treatment. Taken together, such PCL/HAMA/IGF nanofibrous dural substitutes hold promising potential to provide neuroprotection effects after primary and secondary nerve damage in TBI, which would bring significant benefits to the field of neurosurgery involving the use of artificial dura mater.

Spongy-like hydrogels prevascularization with the adipose tissue vascular fraction delays cutaneous wound healing by sustaining inflammatory cell influx

In vitro prevascularization is one of the most explored approaches to foster engineered tissue vascularization. We previously demonstrated a benefit in tissue neovascularization by using integrin-specific biomaterials prevascularized by stromal vascular fraction (SVF) cells, which triggered vasculogenesis in the absence of extrinsic growth factors. SVF cells are also associated to biological processes important in cutaneous wound healing. Thus, we aimed to investigate whether in vitro construct prevascularization with SVF accelerates the healing cascade by fostering early vascularization vis-à-vis SVF seeding prior to implantation. Prevascularized constructs delayed re-epithelization of full-thickness mice wounds compared to both non-prevascularized and control (no SVF) groups. Our results suggest this delay is due to a persistent inflammation as indicated by a significantly lower M2(CD163+)/M1(CD86+) macrophage subtype ratio. Moreover, a slower transition from the inflammatory to the proliferative phase of the healing was confirmed by reduced extracellular matrix deposition and increased presence of thick collagen fibers from early time-points, suggesting the prevalence of fiber crosslinking in relation to neodeposition. Overall, while prevascularization potentiates inflammatory cell influx, which negatively impacts the cutaneous wound healing cascade, an effective wound healing was guaranteed in non-prevascularized SVF cell-containing spongy-like hydrogels confirming that the SVF can have enhanced efficacy.

Hydrogels for the management of second-degree burns: currently available options and future promise

Burn wounds result from exposure to hot liquids, chemicals, fire, electric discharge or radiation. Wound severity ranges from first-degree injury, which is superficial, to fourth-degree injury, which exposes bone, tendons and muscles. Rapid assessment of burn depth and accurate wound management in the outpatient setting is critical to prevent injury progression into deeper layers of the dermis. Injury progression is of particular pertinence to second-degree burns, which are the most common form of thermal burn. As our understanding of wound healing advances, treatment options and technologies for second-degree burn management also evolve. Polymeric hydrogels are a class of burn wound dressings that adhere to tissue, absorb wound exudate, protect from the environment, can be transparent facilitating serial wound evaluation and, in some cases, enable facile removal for dressing changes. This review briefly describes the burn level classification and common, commercially available dressings used to treat second-degree burns, and then focuses on new polymeric hydrogel burn dressings under preclinical development analyzing their design, structure and performance. The review presents the follow key learning points: (1) introduction to the integument system and the wound-healing process; (2) classification of burns according to severity and clinical appearance; (3) available dressings currently used for second-degree burns; (4) introduction to hydrogels and their preparation and characterization techniques; and (5) pre-clinical hydrogel burn wound dressings currently being developed.

A composite hydrogel containing resveratrol-laden nanoparticles and platelet-derived extracellular vesicles promotes wound healing in diabetic mice

Diabetic wounds are difficult to heal because of persistent inflammation and limited angiogenesis. Resveratrol (RES) is an anti-inflammatory and antioxidant agent. Platelet-derived extracellular vesicles (PDEVs) are rich in growth factors and cytokines, which promote proliferation and angiogenesis. However, single drug treatment has limited efficacy and delivery efficiency. Bioengineering can improve the limited effect of single drugs by combining drugs and materials to obtain complementary or cooperative bioengineered drugs. In this study, gelatin methacrylate (GelMA) and silk fibroin glycidyl methacrylate (SFMA) were used to synthesize GelMA/SFMA composite hydrogels with suitable mechanical properties, swelling ratio and biodegradability. The composite hydrogel was used as a wound dressing for sustained drug release. RES was loaded into mesoporous silica nanoparticles (MSNs) to synthesize MSN-RES to enhance the release dynamic, and MSN-RES and PDEVs were combined with the composite hydrogels to form GelMA/SFMA/MSN-RES/PDEVs hydrogels. The GelMA/SFMA/MSN-RES/PDEVs had low cytotoxicity and good biocompatibility, inhibited macrophage iNOS expression, and promoted the tube formation by human umbilical vein endothelial cells (HUVECs) in vitro. In a diabetic mouse wound model, the GelMA/SFMA/MSN-RES/PDEVs hydrogels decreased the expression of pro-inflammatory factors TNF-α and iNOS, increased the expression of anti-inflammatory factors TGF-β1 and Arg-1, promoted angiogenesis, and accelerated wound healing. Interestingly, the GelMA/SFMA/MSN-RES/PDEVs hydrogels promoted the expression of extracellular purinergic signaling pathway-related CD73 and adenosine 2A receptor (A2A-R). Therefore, the GelMA/SFMA/MSN-RES/PDEVs hydrogels could be used as wound dressings to regulate the inflammation and angiogenesis of diabetic wounds and accelerate wound healing. STATEMENT OF SIGNIFICANCE: Drugs often fail to function because of a continuous oxidative stress microenvironment and inflammation. Here, a GelMA/SFMA hydrogel, with enhanced mechanical properties and liquid absorption ability, is proposed for sustained release of drugs. In addition to carrying platelet-derived extracellular vesicles (PDEVs) with pro-angiogenic effects, the hydrogels were also loaded with nanoparticle-encapsulated resveratrol with anti-inflammatory activities, aiming to reduce inflammation and oxidative stress in the wound microenvironment, such that the wound could receive proliferative repair signals to achieve sequential treatment and heal quickly. We also experimentally predicted that the regulatory mechanism of the GelMA/SFMA/MSN-RES/PDEVs in wound healing might be related to the extracellular purinergic signaling pathway.

Comparison of Deep Partial Thickness Burns Wound Healing with Resveratrol Gel and Paraffin Gauze in Wistar Rats

BACKGROUND: Various modalities of wound care in burn cases are offered, but there is no standard algorithm used. Paraffin gauze dressing, as one of the commonly used dressings, is considered to have many shortcomings. Resveratrol, a stilbenoid derived from plants, is reported to have a role in wound healing process, it has the potential to be one of the modalities for treating burns. This study aims to strengthen studies on the role of resveratrol in wound healing process, especially in burns compared with paraffin gauze. AIM: This study conducted to prove that resveratrol gel more superior than paraffin gauze in deep partial thickness burns healing process. METHODS: This research is a laboratory experimental study with a post-test only design, simple randomized, and single blind. A sample of 32 Wistar rats with deep partial thickness burns was divided into four control groups and four treatment groups. Control groups were treated using paraffin gauze. Treatment groups were treated using resveratrol gel. Group 1 of each group was assessed for epithelialization. Angiogenesis, fibroblasts, and collagen deposition was assessed on day 5 in Group 2, day 14 in Group 3, and day 21 in Group 4. RESULTS: Angiogenesis was significantly higher in the treatment group than the control group on day 5 and 14 (p = 0.047; 95% CI = 1.23–5.23 and p = 0.032; 95% CI = 0.21–3.28) but not significantly different on day 21 (p = 0.107; 95% CI = −0.43–3.43). The number of fibroblasts in the treatment group was significantly higher on day 5, 14, and 21 (p = 0.004; 0.038; and 0.005; 95% CI = 2.42–17.19; 5.38–16.78; 4.24–15.25). Collagen deposition was not significantly different on day 5 (p = 0.342; 95% CI = −5.65–14.63) but was significantly higher on day 14 and 21 (p = 0.048; 95% CI = 0.11–23.7 and p = 0.002; 95% CI = 10.14–26.57). The epithelialization process occurred earlier in the treatment group than in the control group (p = 0.001). CONCLUSION: Topical administration of resveratrol gel accelerates the epithelialization process, which increases the number of angiogenesis, fibroblasts, and collagen deposition in deep partial thickness burns compared to paraffin gauze.

Evaluating polymeric biomaterials to improve next generation wound dressing design

Wound healing is a dynamic series of interconnected events with the ultimate goal of promoting neotissue formation and restoration of anatomical function. Yet, the complexity of wound healing can often result in development of complex, chronic wounds, which currently results in a significant strain and burden to our healthcare system. The advancement of new and effective wound care therapies remains a critical issue, with the current therapeutic modalities often remaining inadequate. Notably, the field of tissue engineering has grown significantly in the last several years, in part, due to the diverse properties and applications of polymeric biomaterials. The interdisciplinary cohesion of the chemical, biological, physical, and material sciences is pertinent to advancing our current understanding of biomaterials and generating new wound care modalities. However, there is still room for closing the gap between the clinical and material science realms in order to more effectively develop novel wound care therapies that aid in the treatment of complex wounds. Thus, in this review, we discuss key material science principles in the context of polymeric biomaterials, provide a clinical breadth to discuss how these properties affect wound dressing design, and the role of polymeric biomaterials in the innovation and design of the next generation of wound dressings.

Gene therapy to enhance angiogenesis in chronic wounds

Skin injuries and chronic non-healing wounds are one of the major global burdens on the healthcare systems worldwide due to their difficult-to-treat nature, associated co-morbidities, and high health care costs. Angiogenesis has a pivotal role in the wound-healing process, which becomes impaired in many chronic non-healing wounds, leading to several healing disorders and complications. Therefore, induction or promotion of angiogenesis can be considered a promising approach for healing of chronic wounds. Gene therapy is one of the most promising upcoming strategies for the treatment of chronic wounds. It can be classified into three main approaches: gene augmentation, gene silencing, and gene editing. Despite the increasing number of encouraging results obtained using nucleic acids (NAs) as active pharmaceutical ingredients of gene therapy, efficient delivery of NAs to their site of action (cytoplasm or nucleus) remains a key challenge. Selection of the right therapeutic cargo and delivery methods is crucial for a favorable prognosis of the healing process. This article presents an overview of gene therapy and non-viral delivery methods for angiogenesis induction in chronic wounds.

Nucleic acid-based therapeutics for dermal wound healing

Non-healing wounds have long been the subject of scientific and clinical investigations. Despite breakthroughs in understanding the biology of delayed wound healing, only limited advances have been made in properly treating wounds. Recently, research into nucleic acids (NAs) such as small-interfering RNA (siRNA), microRNA (miRNA), plasmid DNA (pDNA), aptamers, and antisense oligonucleotides (ASOs) has resulted in the development of a latest therapeutic strategy for wound healing. In this regard, dendrimers, scaffolds, lipid nanoparticles, polymeric nanoparticles, hydrogels, and metal nanoparticles have all been explored as NA delivery techniques. However, the translational possibility of NA remains a substantial barrier. As a result, different NAs must be identified, and their distribution method must be optimized. This review explores the role of NA-based therapeutics in various stages of wound healing and provides an update on the most recent findings in the development of NA-based nanomedicine and biomaterials, which may offer the potential for the invention of novel therapies for this long-term condition. Further, the challenges and potential for miRNA-based techniques to be translated into clinical applications are also highlighted.

ECM-mimetic immunomodulatory hydrogel for methicillin-resistant Staphylococcus aureus-infected chronic skin wound healing

The treatment of difficult-to-heal wounds remains a substantial clinical challenge due to deteriorative tissue microenvironment including the loss of extracellular matrix (ECM), excessive inflammation, impaired angiogenesis, and bacterial infection. Inspired by the chemical components, fibrous structure, and biological function of natural ECM, antibacterial and tissue environment-responsive glycopeptide hybrid hydrogel was developed for chronic wound healing. The hydrogel can facilitate the cell proliferation and macrophage polarization to M2 phenotype, and show potent antibacterial efficacy against both Gram-negative and Gram-positive bacteria. Significantly, the glycopeptide hydrogel accelerated the reconstruction of methicillin-resistant Staphylococcus aureus (MRSA)-infected full-thickness diabetic and scalding skin by orchestrating a pro-regenerative response indicated by abundant M2-type macrophages, attenuated inflammation, and promoted angiogenesis. Collectively, ECM-mimetic and immunomodulatory glycopeptide hydrogel is a promising multifunctional dressing to reshape the damaged tissue environment without additional drugs, exogenous cytokines, or cells, providing an effective strategy for the repair and regeneration of chronic cutaneous wounds.

Validation of the traditional medicinal use of a Mexican endemic orchid (Prosthechea karwinskii) through UPLC-ESI-qTOF-MS/MS characterization of its bioactive compounds

Ethnopharmacological relevance

The orchid Prosthechea karwinskii is a medicinal orchid in Oaxaca, Mexico, used to treat diabetes, cough, wounds, and burns, prevent miscarriage and assist in labor. Each part of the plant (leaves, pseudobulbs, or flowers) is used by healers for certain treatment conditions, indicating that each part has different biocompounds with specific pharmacological activity.

Aim of the study

To characterize the biocompounds in extracts from leaves, pseudobulbs, and flowers of P. karwinskii and evaluate their ROS inhibition capacity to associate it with medicinal uses.

Materials and methods

The compounds present in extracts from leaves, pseudobulbs, and flowers of P. karwinskii were identified by UPLC-ESI-qTOF-MS/MS. The chemical differentiation of each extract was tested by principal component analysis (PCA) using compound intensity values. For each extract, total phenol and flavonoid contents were quantified. Their antioxidant capacity was evaluated ex vivo by inhibition of ROS with DCFH-DA and in vitro with DPPH radical.

Results

Based on the PCA, it was observed that some compounds were completely separated from others according to the correlation that they presented. The compounds common to all three plant parts were quinic, malic, succinic, azelaic, and pinellic acids. Among the compounds identified, two were exclusive to leaves, four to pseudobulbs, and ten to flowers. Some of the identified compounds have well-known antioxidant activity. The leaves had the highest content of total phenols and flavonoids, and the highest in vitro and ex vivo antioxidant capacity. A strong correlation was observed between phenol and flavonoid contents, and antioxidant capacity ex vivo and in vitro.

Conclusions

It was found that the bioactive compounds and antioxidant capacity of each part of the plant were associated with its traditional medicinal use. A pharmacological potential was also found in P. karwinskii for further biological studies because of the type of compounds it contained.

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Compounds common and specific to each plant part were identified by UPLC-ESI-qTOF-MS/MS.

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The biological activities reported for the identified compounds validate the traditional medicinal use of P. karwinskii.

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Embelin (inflammation) is exclusive to leaves, phloridzin (diabetes) to pseudobulbs, and abscisic acid (in labor) to flowers.

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In the literature, the antioxidant compounds are rutin, kaempferol-3-O-rutinoside, embelin, guanosine, and azelaic acid.

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Pearson's correlation coefficients indicate that a higher content of phenols and flavonoids has a higher antioxidant capacity.

Therapeutic delivery of nucleic acids for skin wound healing

Though wound care has advanced, treating chronic wounds remains a challenge and there are many clinical issues that must be addressed. Gene therapy is a recent approach to treating chronic wounds that remains in its developmental stage. The limited reports available describe the therapeutic applications of various forms of nucleic acid delivery for treating chronic wounds, including DNA, mRNA, siRNA, miRNA and so on. Though these bioactive molecules represent great therapeutic potential, sustaining their bioactivity in the wound bed is a challenge. To overcome this hurdle, delivery systems are also being widely investigated. In this review, nucleic acid-based therapy and its delivery for treating chronic wounds is discussed in detail.

Complexation of phytochemicals with cyclodextrins and their derivatives- an update

Bioactive phytochemicals from natural source have gained tremendous interest over several decades due to their wide and diverse therapeutic activities playing key role as functional food supplements, pharmaceutical and nutraceutical products. Nevertheless, their application as therapeutically active moieties and formulation into novel drug delivery systems are hindered due to major drawbacks such as poor solubility, bioavailability and dissolution rate and instability contributing to reduction in bioactivity. These drawbacks can be effectively overcome by their complexation with different cyclodextrins. Present article discusses complexation of phytochemicals varying from flavonoids, phenolics, triterpenes, and tropolone with different natural and synthetic cyclodextrins. Moreover, the article summarizes complexation methods, complexation efficiency, stability, stability constants and enhancement in rate and extent of dissolution, bioavailability, solubility, in vivo and in vitro activities of reported complexed phytochemicals. Additionally, the article presents update of published patent details comprising of complexed phytochemicals of therapeutic significance. Thus, phytochemical cyclodextrin complexes have tremendous potential for transformation into drug delivery systems as substantiated by significant outcome of research findings.

Advances in Immunomodulation and Immune Engineering Approaches to Improve Healing of Extremity Wounds

Delayed healing of traumatic wounds often stems from a dysregulated immune response initiated or exacerbated by existing comorbidities, multiple tissue injury or wound contamination. Over decades, approaches towards alleviating wound inflammation have been centered on interventions capable of a collective dampening of various inflammatory factors and/or cells. However, a progressive understanding of immune physiology has rendered deeper knowledge on the dynamic interplay of secreted factors and effector cells following an acute injury. There is a wide body of literature, both in vitro and in vivo, abstracted on the immunomodulatory approaches to control inflammation. Recently, targeted modulation of the immune response via biotechnological approaches and biomaterials has gained attention as a means to restore the pro-healing phenotype and promote tissue regeneration. In order to fully realize the potential of these approaches in traumatic wounds, a critical and nuanced understanding of the relationships between immune dysregulation and healing outcomes is needed. This review provides an insight on paradigm shift towards interventional approaches to control exacerbated immune response following a traumatic injury from an agonistic to a targeted path. We address such a need by (1) providing a targeted discussion of the wound healing processes to assist in the identification of novel therapeutic targets and (2) highlighting emerging technologies and interventions that utilize an immunoengineering-based approach. In addition, we have underscored the importance of immune engineering as an emerging tool to provide precision medicine as an option to modulate acute immune response following a traumatic injury. Finally, an overview is provided on how an intervention can follow through a successful clinical application and regulatory pathway following laboratory and animal model evaluation.

Progress in hydrogels for skin wound repair

As the first defensive line between the human body and the outside world, the skin is vulnerable to damage from the external environment. Skin wounds can be divided into acute wounds (mechanical injuries, chemical injuries and surgical wounds, etc.) and chronic wounds (burns, infections, diabetes, etc.). In order to manage skin wound, a variety of wound dressings have been developed, including gauze, films, foams, nanofibers, hydrocolloids and hydrogels. Recently, hydrogels have received much attention because of their natural extracellular matrix (ECM)-mimik structure, tunable mechanical properties, and facile bioactive substance delivery capability. They show great potential application in skin wound repair. This paper first introduces the anatomy and function of the skin, the process of wound healing and conventional wound dressings, and then introduces the composition and construction methods of hydrogels. Next, this paper introduces the necessary properties of hydrogels in skin wound repair and the latest research progress of hydrogel dressings for skin wound repair. Finally, the future development goals of hydrogel materials in the field of wound healing are proposed. This article is protected by copyright. All rights reserved.

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.

Recent Advances in Bioengineered Scaffolds for Cutaneous Wound Healing

Wound healing is an evolved dynamic biological process. Though many research and clinical approaches have been explored to restore damaged or diseased skin, the current treatment for deep cutaneous injuries is far from being perfect, and the ideal regenerative therapy remains a significant challenge. Of all treatments, bioengineered scaffolds play a key role and represent great progress in wound repair and skin regeneration. In this review, we focus on the latest advancement in biomaterial scaffolds for wound healing. We discuss the emerging philosophy of designing biomaterial scaffolds, followed by precursor development. We pay particular attention to the therapeutic interventions of bioengineered scaffolds for cutaneous wound healing, and their dual effects while conjugating with bioactive molecules, stem cells, and even immunomodulation. As we review the advancement and the challenges of the current strategies, we also discuss the prospects of scaffold development for wound healing.

Dextran, as a biological macromolecule for the development of bioactive wound dressing materials: A review of recent progress and future perspectives

Skin is the largest organ in the body which plays different roles in maintaining hemostasis. Although this tissue has a high healing potential, severe skin wounds cannot heal without external interventions. Among various treatment strategies, tissue-engineered wound dressings have gained significant attention. In this regard, tremendous progress has been made in the field of tissue engineering to develop constructs with higher healing activities. Material selection and optimization are key factors in development of such dressings. Among different candidates, dextran-based wound dressings have been extensively studied. Dextran is a branched biological macromolecule which is composed of anhydroglucose monomers. Due to its excellent biocompatibility, biodegradability, non-toxicity, modifiable functional groups, and proven clinical safety, dextran has found application in wound healing research. In the current review, applications, challenges, and future perspectives of dextran-based wound dressings will be discussed.

Hydrogels in Burn Wound Management-A Review

Inert hydrogels are of a great importance in burn first aid. Hydrogel dressings may be an alternative to cooling burn wounds with streaming water, especially in cases of mass casualty events, lack of clean water, hypothermia, or large extent of burns. Hydrogels that contain mostly water evacuate the heat cumulating in the skin by evaporation. They not only cool the burn wound, but also reduce pain and protect the wound area from contamination and further injuries. Hydrogels are ideally used during the first hours after injury, but as they do not have antimicrobial properties per se, they might not prevent wound infection. The hydrogel matrix enables incorporating active substances into the dressing. The active forms may contain ammonium salts, nanocrystal silver, zinc, growth factor, cytokines, or cells, as well as natural agents, such as honey or herbs. Active dressings may have antimicrobial activity or stimulate wound healing. Numerous experiments on animal models proved their safety and efficiency. Hydrogels are a new dressing type that are still in development.

Spatiotemporally dynamic therapy with shape-adaptive drug-gel for the improvement of tissue regeneration with ordered structure

A spatiotemporally dynamic therapy (SDT) is proposed as a powerful therapeutic modality that provides spatially dynamic responses of drug-carriers for adapting to the wound microenvironment. Herein, dynamic chitosan-poly (ethylene glycol) (CP) Schiff-base linkages are employed to perform SDT by directly converting a liquid drug Kangfuxin (KFX) into a gel formation. The obtained KFX-CP drug-gel with shape-adaptive property is used to treat a representative oral mucositis (OM) model in a spatiotemporally dynamic manner. The KFX-CP drug-gel creates an instructive microenvironment to regulate signaling biomolecules and endogenous cells behavior, thereby promoting OM healing by the rule of dynamically adjusting shape to fit the irregular OM regions first, and then provides space for tissue regeneration, over KFX potion control and the general hydrogel group of CP hydrogel and KFX-F127. Most interestingly, the regenerated tissue has ordered structure like healthy tissue. Therefore, the SDT provides a new approach for the design of next generation of wound dressing and tissue engineering materials.

Novel dopamine-modified oxidized sodium alginate hydrogels promote angiogenesis and accelerate healing of chronic diabetic wounds

Herein, the dopamine (DA) was grafted with oxidized sodium alginate (OSA) via Schiff base reduction reaction, aiming to fabricate novel DA-grafted OSA (OSA-DA) hydrogels with enhanced biocompatibility and suitable adhesion for clinical applications. The chemical structures of OSA-DA were characterized via UV-Vis, FTIR and ¹H NMR spectroscopy analysis. The hydrogel characteristics, biocompatibility, as well as the chronic diabetic wound healing efficacy were investigated. Our results demonstrated that DA was grafted with OSA successfully with highest grafting rate of 7.50%. Besides, OSA-DA hydrogels possessed suitable swelling ratio and appropriate adhesion characteristics. Additionally, OSA-DA exhibited satisfactory cytocompatibility and cell affinity in L-929 cells, and superior biocompatibility in SD rats. Moreover, OSA-DA exerted remarkable promoting effects on migration and tube formation of human umbilical vein endothelial cells (HUVECs). Studies on full-thickness excision chronic diabetic wounds further revealed that OSA-DA hydrogels could accelerate healing via promoting angiogenesis, reducing inflammation response, and stimulating collagen deposition. Overall, our studies would provide basis for SA-based hydrogels as clinical wound dressings.

In situ-formed adhesive hyaluronic acid hydrogel with prolonged amnion-derived conditioned medium release for diabetic wound repair

Hydrogels have long been used for encapsulating stem cell-derived conditioned mediums to achieve skin regeneration after wounding. However, inappropriate mechanical strength, low adhesion and low elasticity limit their clinical application. To address these challenges, we engineered a hyaluronic acid-based hydrogel grafted with methacrylic anhydride and N-(2-aminoethyl)-4-[4-(hydroxymethyl)-2-methoxy-5-nitrophenoxy]-butanamide (NB) groups to encapsulate a lyophilized amnion-derived conditioned medium (AM-CM). This hydrogel can photopolymerize in situ within 3 s by photo-initiated free-radical crosslinking between methacrylate moieties. Meanwhile, the formed o-nitrosobenzaldehyde groups by photo-irradiation could covalently bond with the amino groups of tissue surface, which allowed strong tissue adhesion. Furthermore, the hydrogel possessed excellent mechanical properties, high elasticity, favorable biocompatibility and prolonged AM-CM release. Our further vitro and in vivo studies showed that the hydrogel significantly accelerated diabetic wound healing by regulating macrophage polarization and promoting angiogenesis. The engineered hydrogel with AM-CM release has high potential to treat chronic wounds in clinics.

Advances in Modified Hyaluronic Acid-Based Hydrogels for Skin Wound Healing

Hyaluronic acid (HA) is a natural linear anionic polysaccharide with many unique characteristics such as excellent biocompatibility and biodegradability, native biofunctionality, hydrophilicity, and non-immunoreactivity. HA plays crucial roles in numerous...

Functional Hydrogel Dressings for Treatment of Burn Wounds

The therapy of burns is a challenging clinical issue. Burns are long-term injuries, and numerous patients suffer from chronic pain. Burn treatment includes management, infection control, wound debridement and escharotomy, dressing coverage, skin transplantation, and the use of skin substitutes. The future of advanced care of burn wounds lies in the development of “active dressings”. Hydrogel dressings have been employed universally to accelerate wound healing based on their unique properties to overcome the limitations of existing treatment methods. This review briefly introduces the advantages of hydrogel dressings and discusses the development of new hydrogel dressings for wound healing along with skin regeneration. Further, the treatment strategies for burns, ranging from external to clinical, are reviewed, and the functional classifications of hydrogel dressings along with their clinical value for burns are discussed.

Synthesis and characterization of levan hydrogels and their use for resveratrol release

Considering the need for systematic studies on levan based hydrogels to widen their use in drug delivery systems and biomedical applications, this study is mainly focused on the synthesis and comprehensive characterization as well as drug release properties of hydrogels based on Halomonas levan (HL) and its chemical derivatives. For this, hydrolyzed and phosphonated HL derivatives were chemically synthesized and then cross-linked with 1,4-Butanediol diglycidyl ether (BDDE) and the obtained hydrogels were characterized in terms of their swelling, adhesivity, and rheological properties. Both native and phosphonated HL hydrogels retained their rigid gel like structure with increasing shear stress levels and tack test analysis showed superior adhesive properties of the phosphonated HL hydrogels. Moreover, hydrogels were loaded with resveratrol and entrapment and release studies as well as cell culture studies with human keratinocytes were performed. Biocompatible and adhesive features of the hydrogels confirmed their suitability for tissue engineering and drug delivery applications.

Biodegradable gelatin/silver nanoparticle composite cryogel with excellent antibacterial and antibiofilm activity and hemostasis for Pseudomonas aeruginosa-infected burn wound healing

Burn wounds are susceptible to bacterial infections and are usually accompanied by a large amount of exudate, making the treatment of burn wounds a challenge in the clinic. Here, we developed a biodegradable cryogel with high water absorption and good antibacterial and antibiofilm activity based on gelatin (GT) and silver nanoparticles (Ag NPs) to promote burn wound healing. The porous GT/Ag cryogel had a swelling ratio of up to 4000%, effectively absorbing wound exudate and allowing for gas exchange. Moreover, the GT/Ag cryogel had an excellent killing effect on methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PA), which burn wounds are susceptible to, and can effectively remove mature biofilms. In the rat liver defect noncompressible hemorrhage model, GT/Ag cryogels with shape memory performance showed better hemostatic ability than commercial gelatin sponges. Most importantly, the GT/Ag cryogel was more effective than the Tegaderm^TM dressing and GT cryogel in promoting wound contraction, collagen deposition, and angiogenesis and reducing inflammation in a PA-infected burn wound model. In addition, GT/Ag cryogels degraded in the body within 4 weeks, which alleviated the pain of peeling the dressing from the wound. Therefore, GT/Ag cryogels with outstanding antibacterial properties and effective absorption of wound exudates are excellent candidates for wound dressings to promote burn wound repair.

The biological applications of DNA nanomaterials: current challenges and future directions

DNA, a genetic material, has been employed in different scientific directions for various biological applications as driven by DNA nanotechnology in the past decades, including tissue regeneration, disease prevention, inflammation inhibition, bioimaging, biosensing, diagnosis, antitumor drug delivery, and therapeutics. With the rapid progress in DNA nanotechnology, multitudinous DNA nanomaterials have been designed with different shape and size based on the classic Watson-Crick base-pairing for molecular self-assembly. Some DNA materials could functionally change cell biological behaviors, such as cell migration, cell proliferation, cell differentiation, autophagy, and anti-inflammatory effects. Some single-stranded DNAs (ssDNAs) or RNAs with secondary structures via self-pairing, named aptamer, possess the ability of targeting, which are selected by systematic evolution of ligands by exponential enrichment (SELEX) and applied for tumor targeted diagnosis and treatment. Some DNA nanomaterials with three-dimensional (3D) nanostructures and stable structures are investigated as drug carrier systems to delivery multiple antitumor medicine or gene therapeutic agents. While the functional DNA nanostructures have promoted the development of the DNA nanotechnology with innovative designs and preparation strategies, and also proved with great potential in the biological and medical use, there is still a long way to go for the eventual application of DNA materials in real life. Here in this review, we conducted a comprehensive survey of the structural development history of various DNA nanomaterials, introduced the principles of different DNA nanomaterials, summarized their biological applications in different fields, and discussed the current challenges and further directions that could help to achieve their applications in the future.

Rational Design of Immunomodulatory Hydrogels for Chronic Wound Healing

With all the advances in tissue engineering for construction of fully functional skin tissue, complete regeneration of chronic wounds is still challenging. Since immune reaction to the tissue damage is critical in regulating both the quality and duration of chronic wound healing cascade, strategies to modulate the immune system are of importance. Generally, in response to an injury, macrophages switch from pro-inflammatory to an anti-inflammatory phenotype. Therefore, controlling macrophages' polarization has become an appealing approach in regenerative medicine. Recently, hydrogels-based constructs, incorporated with various cellular and molecular signals, have been developed and utilized to adjust immune cell functions in various stages of wound healing. Here, the current state of knowledge on immune cell functions during skin tissue regeneration is first discussed. Recent advanced technologies used to design immunomodulatory hydrogels for controlling macrophages' polarization are then summarized. Rational design of hydrogels for providing controlled immune stimulation via hydrogel chemistry and surface modification, as well as incorporation of cell and molecules, are also dicussed. In addition, the effects of hydrogels' properties on immunogenic features and the wound healing process are summarized. Finally, future directions and upcoming research strategies to control immune responses during chronic wound healing are highlighted.

Vascularization in skin wound healing: where do we stand and where do we go?

Cutaneous healing is a highly complex process that, if altered due to, for example, impaired vascularization, results in chronic wounds or repaired neotissue of poor quality. Significant progress has been achieved in promoting neotissue vascularization during tissue repair/regeneration. In this review, we discuss the strategies that have been explored and how each one of them contributes to regulate vascularization in the context of cutaneous wound healing from two different perspectives - biomaterial-based and a cell-based approaches. Finally, we discuss the implications of these findings on the development of the 'next generation' approaches to target vascularization in wound healing highlighting the importance of going beyond its contribution to regulate vascularization and take into consideration the temporal features of the healing process and of different types of wounds.

Biomimetic Hydrogels to Promote Wound Healing

Wound healing is a common physiological process which consists of a sequence of molecular and cellular events that occur following the onset of a tissue lesion in order to reconstitute barrier between body and external environment. The inherent properties of hydrogels allow the damaged tissue to heal by supporting a hydrated environment which has long been explored in wound management to aid in autolytic debridement. However, chronic non-healing wounds require added therapeutic features that can be achieved by incorporation of biomolecules and supporting cells to promote faster and better healing outcomes. In recent decades, numerous hydrogels have been developed and modified to match the time scale for distinct stages of wound healing. This review will discuss the effects of various types of hydrogels on wound pathophysiology, as well as the ideal characteristics of hydrogels for wound healing, crosslinking mechanism, fabrication techniques and design considerations of hydrogel engineering. Finally, several challenges related to adopting hydrogels to promote wound healing and future perspectives are discussed.

Modern Wound Dressings: Hydrogel Dressings

Chronic wounds do not progress through the wound healing process in a timely manner and are considered a burden for healthcare system; they are also the most common reason for decrease in patient quality of life. Traditional wound dressings e.g., bandages and gauzes, although highly absorbent and effective for dry to mild, exudating wounds, require regular application, which therefore can cause pain upon dressing change. In addition, they have poor adhesional properties and cannot provide enough drainage for the wound. In this regard, the normalization of the healing process in chronic wounds is an extremely urgent task of public health and requires the creation and implementation of affordable dressings for patients with chronic wounds. Modern wound dressings (WDs) are aimed to solve these issues. At the same time, hydrogels, unlike other types of modern WDs (foam, films, hydrocolloids), have positive degradation properties that makes them the perfect choice in applications where a targeted delivery of bioactive substances to the wound is required. This mini review is focused on different types of traditional and modern WDs with an emphasis on hydrogels. Advantages and disadvantages of traditional and modern WDs as well as their applicability to different chronic wounds are elucidated. Furthermore, an effectiveness comparison between hydrogel WDs and the some of the frequently used biotechnologies in the field of regenerative medicine (adipose-derived mesenchymal stem cells (ADMSCs), mesenchymal stem cells, conditioned media, platelet-rich plasma (PRP)) is provided.

Nanotechnology-Assisted RNA Delivery: From Nucleic Acid Therapeutics to COVID-19 Vaccines

In recent years, the main quest of science has been the pioneering of the groundbreaking biomedical strategies needed for achieving a personalized medicine. Ribonucleic acids (RNAs) are outstanding bioactive macromolecules identified as pivotal actors in regulating a wide range of biochemical pathways. The ability to intimately control the cell fate and tissue activities makes RNA-based drugs the most fascinating family of bioactive agents. However, achieving a widespread application of RNA therapeutics in humans is still a challenging feat, due to both the instability of naked RNA and the presence of biological barriers aimed at hindering the entrance of RNA into cells. Recently, material scientists' enormous efforts have led to the development of various classes of nanostructured carriers customized to overcome these limitations. This work systematically reviews the current advances in developing the next generation of drugs based on nanotechnology-assisted RNA delivery. The features of the most used RNA molecules are presented, together with the development strategies and properties of nanostructured vehicles. Also provided is an in-depth overview of various therapeutic applications of the presented systems, including coronavirus disease vaccines and the newest trends in the field. Lastly, emerging challenges and future perspectives for nanotechnology-mediated RNA therapies are discussed.

Recent Progress on Polysaccharide-Based Hydrogels for Controlled Delivery of Therapeutic Biomolecules

A plethora of applications using polysaccharides have been developed in recent years due to their availability as well as their frequent nontoxicity and biodegradability. These polymers are usually obtained from renewable sources or are byproducts of industrial processes, thus, their use is collaborative in waste management and shows promise for an enhanced sustainable circular economy. Regarding the development of novel delivery systems for biotherapeutics, the potential of polysaccharides is attractive for the previously mentioned properties and also for the possibility of chemical modification of their structures, their ability to form matrixes of diverse architectures and mechanical properties, as well as for their ability to maintain bioactivity following incorporation of the biomolecules into the matrix. Biotherapeutics, such as proteins, growth factors, gene vectors, enzymes, hormones, DNA/RNA, and antibodies are currently in use as major therapeutics in a wide range of pathologies. In the present review, we summarize recent progress in the development of polysaccharide-based hydrogels of diverse nature, alone or in combination with other polymers or drug delivery systems, which have been implemented in the delivery of biotherapeutics in the pharmaceutical and biomedical fields.

Investigation of the potential therapeutic effect of cationic lipoplex mediated fibroblast growth factor-2 encoding plasmid DNA delivery on wound healing

BACKGROUND

Developing an alternative and efficient therapy for wound healing has been an important research topic for pharmaceutical sciences. A straightforward but effective system for delivering fibroblast growth factor-2 (FGF-2) encoding plasmid DNA (pFGF-2) for wound healing therapy was aimed to develop in this study.

METHODS

In order to provide the delivery of pFGF-2, a delivery vector, namely, cationic lipid nanoparticle (cLN) was developed by the melt-emulsification process, complexed with pFGF-2 to form a lipoplex system and further characterized. The pFGF-2 binding and protecting ability of lipoplexes were evaluated. The cytotoxicity and transfection efficiency of the lipoplexes, FGF-2 expression levels, and in vitro wound healing ability have been investigated on the L929 fibroblast cell line.

RESULTS

The obtained lipoplex system has a particle size of 88.53 nm with a low PDI (0.185), and zeta potential values of 27.8 mV with a spherical shape. The ability of cLNs to bind pFGF-2 and protect against nucleases was demonstrated by gel retardation assay. Furthermore, the developed FGF-2 carrying lipoplexes system showed significant transfection and FGF-2 expression ability comparing naked plasmid. Finally, scratch assay revealed that the developed system is able to promote in vitro cell proliferation/migration in 48 h.

CONCLUSION

Promising results have been achieved with the use of lipoplexes carrying pFGF-2, and this approach could be considered as a potentially applicable concept for the future gene-based wound healing therapies.

Development of an in-situ forming, self-healing scaffold for dermal wound healing: in-vitro and in-vivo studies

The importance of the extra-cellular matrix (ECM) for wound healing has been extensively researched. Understanding its importance, multiple ECM mimetic scaffolds have been developed. However, the majority of such scaffolds are prefabricated. Due to their stiffness, prefabricated scaffolds cannot come into direct contact with the basal skin cells at the wound bed, limiting their efficacy. We have developed a unique wound dressing, using chitosan (CH) and chondroitin sulfate (CS), that can form a porous scaffold (CH-CS PEC) in-situ, at the wound site, by simple mixing of the polymer solutions. As CH is positively and CS is negatively charged, mixing these two polymer solutions would lead to electrostatic cross-linking between the polymers, converting them to a porous, viscoelastic scaffold. Owing to the in-situ formation, the scaffold can come in direct contact with the cells at the wound bed, supporting their proliferation and biofunction. In the present study, we confirmed the cross-linked scaffold formation by solid-state NMR, XRD, and TGA analysis. We have demonstrated that the scaffold had a high viscoelastic property, with self-healing capability. Both keratinocyte and fibroblast cells exhibited significantly increased migration and functional markers expression when grown on this scaffold. In the rat skin-excisional wound model, treatment with the in-situ forming CH-CS PEC exhibited enhanced wound healing efficacy. Altogether, this study demonstrated that mixing CH and CS solutions lead to the spontaneous formation of a highly viscoelastic, porous scaffold, which can support epidermal and dermal cell proliferation and bio-function, with an enhanced in-vivo wound healing efficacy.

Modulation of macrophages by a paeoniflorin-loaded hyaluronic acid-based hydrogel promotes diabetic wound healing

The impaired wound healing in diabetes is a central concern of healthcare worldwide. However, current treatments often fail due to the complexity of diabetic wounds, and thus, emerging therapeutic approaches are needed. Macrophages, a prominent immune cell in the wound, play key roles in tissue repair and regeneration. Recent evidence has demonstrated that macrophages in diabetic wounds maintain a persistent proinflammatory phenotype that causes the failure of healing. Therefore, modulation of macrophages provides great promise for wound healing in diabetic patients. In this study, the potential of paeoniflorin (PF, a chemical compound derived from the herb Paeonia lactiflora) for the transition of macrophages from M1 (proinflammatory phenotype) to M2 (anti-inflammatory/prohealing phenotype) was confirmed using ex vivo and in vivo experimental approaches. A hydrogel based on high molecular weight hyaluronic acid (HA) was developed for local administration of PF in experimental diabetic mice with a full-thickness wound. The resultant formulation (HA-PF) was able to significantly promote cutaneous healing as compared to INTRASITE Gel (a commercial hydrogel wound dressing). This outcome was accompanied by the amelioration of inflammation, the improvement of angiogenesis, and re-epithelialization, and the deposition of collagen. Our study indicates the significant potential of HA-PF for clinical translation in diabetic wound healing.

Approaches to Modulate the Chronic Wound Environment Using Localized Nucleic Acid Delivery

Significance: Nonhealing wounds have been the subject of decades of basic and clinical research. Despite new knowledge about the biology of impaired wound healing, little progress has been made in treating chronic wounds, leaving patients with few therapeutic options. Diabetic ulcers are a particularly common form of nonhealing wound. Recent Advances: Recently, investigation of therapeutic nucleic acids (TNAs), including plasmid DNA, small interfering RNA, microRNA mimics, anti-microRNA oligonucleotides, messenger RNA, and antisense oligonucleotides, has created a new treatment strategy for chronic wounds. TNAs can modulate the wound toward a prohealing environment by targeting gene pathways associated with inflammation, proteases, cell motility, angiogenesis, epithelialization, and oxidative stress. A variety of delivery systems have been investigated for TNAs, including dendrimers, lipid nanoparticles (NPs), polymeric micelles, polyplexes, metal NPs, and hydrogels. This review summarizes recent developments in TNA delivery for therapeutic targets associated with chronic wounds, with an emphasis on diabetic ulcers. Critical Issues: Translational potential of TNAs remains a key challenge; we highlight some drug delivery approaches for TNAs that may hold promise. We also describe current commercial efforts to locally deliver nucleic acids to modulate the wound environment. Future Directions: Localized nucleic acid delivery holds promise for the treatment of nonhealing chronic wounds. Future efforts to improve targeting of these nucleic acid therapies in the wound with both spatial and temporal control through drug delivery systems will be crucial to successful clinical translation.

Biomaterial-based delivery of nucleic acids for tissue regeneration

Gene therapy is a promising novel method of tissue regeneration by stimulating or inhibiting key signaling pathways. However, their therapeutic applications in vivo are largely limited by several physiological obstacles, such as degradation of nucleases, impermeability of cell membranes, and transport to the desired intracellular compartments. Biomaterial-based gene delivery systems can overcome the problems of stability and local drug delivery, and can temporarily control the overexpression of therapeutic genes, leading to the local production of physiologically relevant levels of regulatory factors. But the gene delivery of biomaterials for tissue regeneration relies on multi-factor design. This review aims to outline the impact of gene delivery methods, therapeutic genes and biomaterials selection on this strategy, emphatically introduce the latest developments in the design of gene delivery vehicles based on biomaterials, summarize the mechanism of nucleic acid for tissue regeneration, and explore the strategies of nucleic acid delivery vehicles for various tissue regeneration.

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.

Toward a Better Regeneration through Implant-Mediated Immunomodulation: Harnessing the Immune Responses

Tissue repair/regeneration, after implantation or injury, involves comprehensive physiological processes wherein immune responses play a crucial role to enable tissue restoration, amidst the immune cells early-stage response to tissue damages. These cells break down extracellular matrix, clear debris, and secret cytokines to orchestrate regeneration. However, the immune response can also lead to abnormal tissue healing or scar formation if not well directed. This review first introduces the general immune response post injury, with focus on the major immune cells including neutrophils, macrophages, and T cells. Next, a variety of implant-mediated immunomodulation strategies to regulate immune response through physical, chemical, and biological cues are discussed. At last, various scaffold-facilitated regenerations of different tissue types, such as, bone, cartilage, blood vessel, and nerve system, by harnessing the immunomodulation are presented. Therefore, the most recent data in biomaterials and immunomodulation is presented here in a bid to shape expert perspectives, inspire researchers to go in new directions, and drive development of future strategies focusing on targeted, sequential, and dynamic immunomodulation elicited by implants.

Promising Polymeric Drug Carriers for Local Delivery: The Case of in situ Gels

BACKGROUND

At present, the controlled local drug delivery is a very promising approach compared to systemic administration, since it mostly targets the affected tissue. In fact, various drug carriers for local delivery have been prepared with improved therapeutic efficacy.

OBJECTIVE

in situ polymer gels are drug delivery systems that not only present liquid characteristics before their administration in body, but once they are administered, form gels due to gelation. Their gelation mechanism is due to factors such as pH alteration, temperature change, ion activation or ultraviolet irradiation. in situ gels offer various advantages compared to conventional formulations due to their ability to release drugs in a sustainable and controllable manner. Most importantly, in situ gels can be used in local drug delivery applications for various diseases.

METHODS

This review includes the basic knowledge and theory of in situ gels as well as their various applications according to their administration route.

RESULTS

Various natural, semisynthetic, and synthetic polymers can produce in situ polymeric gels. For example, natural polysaccharides such as alginic acid, chitosan, gellan gum, carrageenan etc. have been utilized as in situ gels for topical delivery. Besides the polysaccharides, poloxamers, poly(Nisopropylacrylamide), poly(ethyleneoxide)/ (lactic-co-glycolic acid), and thermosensitive liposome systems can be applied as in situ gels. In most cases, in situ polymeric gels could be applied via various administration routes such as oral, vaginal, ocular, intranasal and injectable.

CONCLUSION

To conclude, it can be revealed that in situ gels could be a promising alternative carrier for both chronic and immediate diseases.

PDGF-BB/SA/Dex injectable hydrogels accelerate BMSC-mediated functional full thickness skin wound repair by promoting angiogenesis

Wound healing is a well-orchestrated dynamic and interactive process, which needs a favorable microenvironment and suitable angiogenesis. Platelet derived growth factor-BB (PDGF-BB) plays a crucial role in wound healing. However, the short half-life of PDGF-BB limits its efficacy. In the present study, we successfully synthesized an injectable hydrogel with sodium alginate (SA) and dextran (Dex) as a delivery system to simultaneously deliver PDGF-BB and bone marrow-derived mesenchymal stem cells (BMSCs) in the wound. Our work demonstrates that the PDGF-BB protein enhanced the survival, migration and endothelial cell (EC) differentiation of BMSCs in vitro. The PDGF-BB/SA/Dex hydrogels could sustainably release PDGF-BB with excellent biocompatibility in vitro and in vivo. Besides, these composite hydrogels loaded with BMSCs could accelerate wound healing by improving epithelialization and collagen deposition. In addition, the PDGF-BB/SA/Dex hydrogels promoted the EC-differentiation of transplanted BMSCs and proliferation of hair follicle stem cells in the wound. Furthermore, the expressions of angiogenesis-specific markers, PDGFR-β, p-PI3K, p-Akt, and p-eNOS, were obviously increased in the PDGF-BB/SA/Dex/BMSCs group. In conclusion, the PDGF-BB/SA/Dex injectable hydrogels could accelerate BMSC-mediated skin wound healing by promoting angiogenesis via the activation of the PDGF-BB/PDGFR-β-mediated PI3K/Akt/eNOS pathway, which may provide a new therapeutic strategy for stem cell therapy in wound healing.

Hyaluronic Acid-Based Scaffolds as Potential Bioactive Wound Dressings

The negative factors that result in delayed and prolonged wound healing process include microbial pathogens, excess wound exudates, underlying conditions, smoking, obesity, etc. Most of the currently used wound dressings demonstrate an inadequate capacity to treat wounds resulting from the factors mentioned above. The commonly used wound dressings include hydrogels, films, hydrocolloids, foams, fibers, sponges, dermal patches, bandages, etc. These wound dressings can be loaded with various types of bioactive agents (e.g., antibiotics, nanoparticles, anti-inflammatory drugs, etc.) to improve their therapeutic outcomes. Biopolymers offer interesting properties suitable for the design of wound dressings. This review article will be based on hyaluronic-acid-based scaffolds loaded with therapeutic agents for the treatment of wounds.

In Vivo Tissue Implantation Model of In Vivo Tissue Implantation Model of Lidocaine (LCH)-Encapsulated Dextran (DEX)/Glycol (GLY) Nanoparticles Delivery for Pain Management

Lidocaine-loaded nanoparticles are versatile nanomaterials that may be used in pain treatment due to their wound healing properties. The current study describes a wound dressing formulation focused on lidocaine-loaded dextran/ethylene glycol nanoparticles (an anesthetic drug). The lidocaine-loaded dextran/ethylene glycol membranes were fabricated using lidocaine solutions inside the dextran/ethylene glycol medium. The influence of various experimental conditions on dextran/ethylene glycol nanoparticle formations were examined. The sizes of dextran/ethylene glycol and lidocaine-loaded dextran/glycol nanoparticles were examined through the HR-SEM. Moreover, the efficacy antibacterial activity of dextran/glycol and lidocaine-loaded dextran/ethylene glycol nanoparticles was evaluated against the microorganisms grampositive and negative. Furthermore, we observed the In Vivo wound healing of wounds in skin using a mice model over a 16 days period. In this difference to the wounds of untreated mouse, quick healing was observed in the lidocaine-loaded dextran/glycol nanoparticles-treated wounds with fewer injury. These results specify that lidocaine-loaded dextran/ethylene glycol nanoparticles-based dressing material could be a ground-breaking nanomaterial having wound repair and implantations potential required for wound injury in pain management, which was proven using an animal model.

Recent trends on burn wound care: hydrogel dressings and scaffolds

Acute and chronic wounds can cause severe physical trauma to patients and also result in an immense socio-economic burden. Thus, wound management has attracted increasing attention in recent years. However, burn wound management is still a major challenge in wound management. Autografts are often considered the gold-standard for burn care, but their application is limited by many factors. Hence, ideal burn dressings and skin substitute dressings are desirable. With the development of biomaterials and progress of tissue engineering technology, some innovative dressings and tissue engineering scaffolds, such as nanofibers, films, foams and hydrogels, have been widely used in the field of biomedicine, especially in wound management. Among them, hydrogels have attracted tremendous attention with their unique advantages. In this review, we discuss the challenges in burn wound management, several crucial design considerations with respect to hydrogels for burn wound healing, and available polymers for hydrogels in burn wound care. In addition, the potential application and plausible prospect of hydrogels are also highlighted.

Autocrine and Paracrine Effects of Vascular Endothelial Cells Promote Cutaneous Wound Healing

Background

When vascular endothelial cells are subjected to external stimuli, paracrine hormones and cytokines act on adjacent cells. The regulation of the biological behaviour of cells is closely related to the maintenance of organ function and the occurrence and development of disease. However, it is unclear whether vascular endothelial cells affect the biological behaviour of cells involved in wound repair through autocrine and paracrine mechanisms and ultimately play a role in wound healing. We aimed to verify the effect of the autocrine and paracrine functions of vascular endothelial cells on wound healing.

Materials and Methods

ELISA was used to detect platelet-derived growth factor, basic fibroblast growth factor, epidermal growth factor, and vascular endothelial growth factor in human umbilical vascular endothelial cell-conditioned medium (HUVEC-CM). Different concentrations of HUVEC-CM were used to treat different stem cells. CCK-8 and scratch assays were used to detect the proliferation and migration ability of each cell. A full-thickness dorsal skin defect model was established in mice, and skin wound healing was observed after the local injection of HUVEC-CM, endothelial cell medium (ECM), or normal saline. H&E staining and immunofluorescence were used to observe the gross morphology of the wound tissue, the epithelial cell migration distance, and the expression of CD3 and CD31.

Results

HUVEC-CM promotes the proliferation and migration of epidermal stem cells, skin fibroblasts, bone marrow mesenchymal stem cells, and HUVECs themselves. Furthermore, HUVEC-CM can promote angiogenesis in mouse skin wounds and granulation tissue formation and can accelerate wound surface epithelialization and collagen synthesis, thereby promoting wound healing.

Conclusion

Our results clearly suggest that it is practicable and effective to promote wound healing with cytokines secreted by vascular endothelial cells in a mouse model.