Skin Wound Healing Process and New Emerging Technologies for Skin Wound Care and Regeneration

Isolation of Aloe saponaria-Derived Extracellular Vesicles and Investigation of Their Potential for Chronic Wound Healing

A chronic wound is caused by a failure to progress through the normal phases of wound repair in an orderly and timely manner. To induce skin regeneration while inhibiting chronic inflammation, numerous natural products, and in particular, plant-derived biomaterials, have been developed. Aloe saponaria, is known to contain flavonoid and phenolic acid compounds with anti-oxidative and anti-inflammatory properties. Here, we isolated extracellular vesicles (EVs) from Aloe saponaria by polyethylene glycol (PEG)-based precipitation and investigated their potential as a therapeutic for chronic wound healing. The Aloe saponaria-derived EVs (AS-EVs) showed no significant cytotoxicity on several cell types, despite a high level of intracellular uptake. When lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages were treated with AS-EVs, significant reductions in the expression of pro-inflammatory genes, such as interleukin-6 and interleukin-1β, were observed. Proliferation and migration of human dermal fibroblasts, as determined by the water-soluble tetrazolium salt-8 and transwell migration assay, respectively, were shown to be promoted by treatment with AS-EVs. It was also demonstrated that AS-EVs enhanced tube formation in human umbilical vein endothelial cells, indicating a stimulatory activity on angiogenesis; one of the crucial steps for effective wound healing. Collectively, our results suggest the potential of AS-EVs as a natural therapeutic for chronic wound healing.

Skin microbiome considerations for long haul space flights

Dysbiosis of the human skin microbiome has long been associated with changes to the pH of the skin, dermal immune function and chronic skin conditions. Dermatological issues have been noted as the most prevalent medical presentation in the microgravity environment of space. The change in gravitational forces has been implicated in human immuno-suppression, also impacted by changes in the gastrointestinal-skin axis and its impact on Vitamin D metabolism, altered microbial gene expression in resident flora (leading changes in biofilm formation) and increased virulence factors in potential pathogens. There are also other stressors to the skin microbiome unique to space travel, including increased exposure to radiation, prolonged periods of dry washing technique, air quality and changes in microbe replication and growth parameters. Optimal microbiome health leads to enhanced skin barrier manufacture and maintenance, along with improved skin immune function and healing. In a microgravity environment expected to be experienced during long space flights, disruptions to the skin microbiome, coupled with increased virulence of pathological viruses and bacteria has implications for holistic skin health, astronaut cognitive function and mental health, and is coupled with slowed rates of wound healing. Scenario management for holistic skin health and restoration of microbiome homeostasis on long space flights require consideration.

Cell-free therapy based on stem cell-derived exosomes: A promising approach for wound healing

There are several successive and overlapping phases in wound healing as a complex process. By the disruption of each of these phases, chronic non-healing wounds are resultant. Despite the present soothing surgeries, standard wound dressings and topical gels, the wound is often not completely closed. Today, stem cells have attracted a huge deal of attention therapeutically and pharmaceutically considering their unique features. However, they have some restrictions. Moreover, it is hoped to eliminate the limitations of cellular therapies based on their derivatives known as exosomes. Exosomes are extracellular vesicles secreted from cells. They have a diameter of almost 30-150 nm and miRNAs, mRNAs, and proteins that are possibly different from the source cell are included in exosomal contents. Such nanovesicles have a key role in the intercellular communication of pathological and physiological procedures. Exosome-based therapy is a new significant method for wound healing. By exosomes effects, wound management may be improved and a new therapeutic model may be highlighted for cell-free therapies with reduced side effects for the wound repair.

Turning gray selenium into a nanoaccelerator of tissue regeneration by PEG modification

Selenium (Se) is an essential trace element involved in nearly all human physiological processes but suffers from a narrow margin between benefit and toxicity. The nanoform of selenium has been proven shown to be more bioavailable and less toxic, yet significant challenges remain regarding the efficient and feasible synthesis of biologically active nanoselenium. In addition, although nanoselenium has shown a variety of biological activities, more interesting nanoselenium features are expected. In this work, hydrosoluble nanoselenium termed Nano-Se in the zero oxidation state was synthesized between gray Se and PEG. A zebrafish screen was carried out in zebrafish larvae cocultured with Nano-Se. Excitingly, Nano-Se promoted the action of the FGFR, Wnt, and VEGF signaling pathways, which play crucial roles in tissue regeneration. As expected, Nano-Se not only achieved the regeneration of zebrafish tail fins and mouse skin but also promoted the repair of skin in diabetic mice while maintaining a profitable safe profile. In brief, the Nano-Se reported here provided an efficient and feasible method for bioactive nanoselenium synthesis and not only expanded the application of nanoselenium to regenerative medicine but also likely reinvigorated efforts for discovering more peculiarunique biofunctions of nanoselenium in a great variety of human diseases.

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It was found that selenium nanoparticles through FGFR、Wnt、VEGFR signal pathway to promote tissue regeneration;

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Development a new water-soluble, bio-compatible, zero oxidation state Nano-Se;

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Development a new efficient and safe nano-biologic agent for promoting tissue regeneration.

Pharmaceutics 2022 Best Paper Awards

Pharmaceutics [...]

Nanoparticles incorporated in nanofibers using electrospinning: A novel nano-in-nano delivery system

Nanofibers are cutting-edge drug delivery systems that are being utilised to treat a variety of ailments. Nanofibers are mostly woven by electrospinning techniques that are majorly used in drug delivery, wound dressing, tissue engineering, sensors, etc. They have several limitations that can be addressed by developing nano-in-nano delivery techniques. Nanoparticles are incorporated into nanofibers in these nano-in-nano systems. They offer a lot of benefits over other nanosystems, including the ability to shield drugs from physical deterioration, the ability to provide prolonged drug release, high surface area to volume ratio, increased drug loading capacity and the potential to be employed in critical conditions such as cancer. These nanoparticles can be encapsulated, entrapped, or adsorbed onto nanofibers in a variety of ways. To include nanosystems into nanofibers, a variety of materials and different kinds of nanoparticles can be used. The present review gives an insight to the applications of nano - in - nano drug delivery system for different diseases/disorders. The review also brings forward the current state of these novel delivery systems along with future perspectives.

Air-Pressure-Supported Application of Cultured Human Keratinocytes in a Fibrin Sealant Suspension as a Potential Clinical Tool for Large-Scale Wounds

The treatment of large-scale skin wounds remains a therapeutic challenge. In most cases there is not enough autologous material available for full coverage. Cultured epithelial autografts are efficient in restoring the lost epidermal cover; however, they have some disadvantages, such as difficult application and protracted cell cultivation periods. Transplanting a sprayed keratinocyte suspension in fibrin sealant as biological carrier is an option to overcome those disadvantages. Here, we studied different seeding techniques regarding their applicability and advantages on cell survival, attachment, and outgrowth in vitro and thereby improve the cell transfer to the wound bed. Human primary keratinocytes were suspended in a fibrin sealant. WST-8 assay was used to evaluate the vitality for 7 days. Furthermore, the cells were labeled with CellTracker™ CM-Di-I and stained with a life/dead staining. Cell morphology, shape, and distribution were microscopically analyzed. There was a significant increase in vitality while cultivating the cells in fibrin. Sprayed cells were considerably more homogenously distributed. Sprayed cells reached the confluent state earlier than dripped cells. There was no difference in the vitality and morphology in both groups over the observation period. These findings indicate that the sprayed keratinocytes are superior to the application of the cells as droplets. The sprayed application may offer a promising therapeutic option in the treatment of large chronic wounds.

Fabrication of Curcumin-Loaded Silk Fibroin and Polyvinyl Alcohol Composite Hydrogel Films for Skin Wound Healing

Skin regeneration of full-thickness wounds remains a challenge, requiring a well-regulated interplay of cell-cell and cell-matrix signaling. Herein, the composite hydrogel films composed of silk fibroin (SF) and polyvinyl alcohol (PVA) as scaffolds loaded with curcumin nanoparticles (Cur NPs) were developed for skin wound healing. The structure and physicochemical properties of hydrogel films were first evaluated by scanning electron microscopy (SEM), water contact angle, and chemical and mechanical measurements. In addition, the as-fabricated composite hydrogel films have a unique 3D structure and excellent biocompatibility that facilitates the adhesion and growth of cells. Antimicrobial tests in vitro showed that they could inhibit the growth of bacteria due to the incorporation of Cur NPs into composite hydrogel films. The efficacy of the curcumin-loaded SF/PVA composite hydrogel films for skin wound healing was investigated on the skin defect model in vivo. Immunological analysis showed that the as-fabricated Cur NP-loaded SF/PVA composite hydrogel films inhibited inflammation at the wound sites, while promoting angiogenesis during the wound healing process.

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.

Generation of an Immortalized Human Adipose-Derived Mesenchymal Stromal Cell Line Suitable for Wound Healing Therapy

Adipose-derived mesenchymal stromal cells (ADSC) are a promising source for cellular therapy of chronic wounds. However, the limited life span during in vitro expansion impedes their extensive use in clinical applications and basic research. We hypothesize that by introduction of an ectopic expression of telomerase into ADSC, the cells’ lifespans could be significantly extended. To test this hypothesis, we aimed at engineering an immortalized human ADSC line using a lentiviral transduction with human telomerase (hTERT). ADSC were transduced with a third-generation lentiviral system and a hTERT codifying plasmid (pLV-hTERT-IRES-hygro). A population characterized by increased hTERT expression, extensive proliferative potential and remarkable (potent) multilineage differentiation capacity was selected. The properties for wound healing of this immortalized ADSC line were assessed after 17 passages. Their secretome induced the proliferation and migration of keratinocytes, dermal fibroblasts, and endothelial cells similarly to untransduced ADSC. Moreover, they sustained the complete re-epithelialization of a full thickness wound performed on a skin organotypic model. In summary, the engineered immortalized ADSC maintain the beneficial properties of parent cells and could represent a valuable and suitable tool for wound healing in particular, and for skin regenerative therapy in general.

Borrowing the Features of Biopolymers for Emerging Wound Healing Dressings: A Review

Wound dressing design is a dynamic and rapidly growing field of the medical wound-care market worldwide. Advances in technology have resulted in the development of a wide range of wound dressings that treat different types of wounds by targeting the four phases of healing. The ideal wound dressing should perform rapid healing; preserve the body’s water content; be oxygen permeable, non-adherent on the wound and hypoallergenic; and provide a barrier against external contaminants—at a reasonable cost and with minimal inconvenience to the patient. Therefore, choosing the best dressing should be based on what the wound needs and what the dressing does to achieve complete regeneration and restoration of the skin’s structure and function. Biopolymers, such as alginate (ALG), chitosan (Cs), collagen (Col), hyaluronic acid (HA) and silk fibroin (SF), are extensively used in wound management due to their biocompatibility, biodegradability and similarity to macromolecules recognized by the human body. However, most of the formulations based on biopolymers still show various issues; thus, strategies to combine them with molecular biology approaches represent the future of wound healing. Therefore, this article provides an overview of biopolymers’ roles in wound physiology as a perspective on the development of a new generation of enhanced, naturally inspired, smart wound dressings based on blood products, stem cells and growth factors.

Innovative Treatment Strategies to Accelerate Wound Healing: Trajectory and Recent Advancements

Wound healing is highly specialized dynamic multiple phase process for the repair of damaged/injured tissues through an intricate mechanism. Any failure in the normal wound healing process results in abnormal scar formation, and chronic state which is more susceptible to infections. Chronic wounds affect patients’ quality of life along with increased morbidity and mortality and are huge financial burden to healthcare systems worldwide, and thus requires specialized biomedical intensive treatment for its management. The clinical assessment and management of chronic wounds remains challenging despite the development of various therapeutic regimens owing to its painstakingly long-term treatment requirement and complex wound healing mechanism. Various conventional approaches such as cell therapy, gene therapy, growth factor delivery, wound dressings, and skin grafts etc., are being utilized for promoting wound healing in different types of wounds. However, all these abovementioned therapies are not satisfactory for all wound types, therefore, there is an urgent demand for the development of competitive therapies. Therefore, there is a pertinent requirement to develop newer and innovative treatment modalities for multipart therapeutic regimens for chronic wounds. Recent developments in advanced wound care technology includes nanotherapeutics, stem cells therapy, bioengineered skin grafts, and 3D bioprinting-based strategies for improving therapeutic outcomes with a focus on skin regeneration with minimal side effects. The main objective of this review is to provide an updated overview of progress in therapeutic options in chronic wounds healing and management over the years using next generation innovative approaches. Herein, we have discussed the skin function and anatomy, wounds and wound healing processes, followed by conventional treatment modalities for wound healing and skin regeneration. Furthermore, various emerging and innovative strategies for promoting quality wound healing such as nanotherapeutics, stem cells therapy, 3D bioprinted skin, extracellular matrix-based approaches, platelet-rich plasma-based approaches, and cold plasma treatment therapy have been discussed with their benefits and shortcomings. Finally, challenges of these innovative strategies are reviewed with a note on future prospects.

Honey-Loaded Reinforced Film Based on Bacterial Nanocellulose/Gelatin/Guar Gum as an Effective Antibacterial Wound Dressing

Recently, the use of bacterial nanocellulose (BNC) produced by Acetobacter, which has suitable properties for tissue engineering application as a perfect wound dressing, has attracted considerable attention. For this purpose, we successfully developed honey loaded BNC-reinforced gelatin/dialdehyde-modified guar gum films (H/BNC/Ge/D-GG). Prepared films were studied for their morphological, thermal stability, mechanical, water solubility and degradability properties. The physicochemical properties of the developed films with or without honey loading were studied. The results indicated that by enhancing the honey content of the film, the degradation behavior, adhesion and proliferation of NIH-3T3 fibroblast cells were improved. The films with 15 wt% of honey revealed inhibition activity against S. aureus (13.0±0.1 mm) and E. coli (15.0±1.0 mm) bacteria. Cell culture results demonstrated that the prepared films had good cytocompatibility. Based on the results, the prepared H/BNC/Ge/D-GG films appear to have high potential for antibacterial wound dressings.

Protease-responsive hydrogel, cross-linked with bioactive curcumin-derived carbon dots, encourage faster wound closure

The pharmacological effects of curcumin can be ascribed to its dose-dependent activity. Therapeutic application of curcumin is hindered by its poor solubility and low bioavailability. Carbon dots are gaining attention in biomedical applications in view of their unique photo-physical properties. Some carbon dots derived from bioactive molecules have shown superior activity than the parent compound. With an aim to address the limitations of curcumin, herein we compared the wound healing activity of curcumin-derived carbon dots (CurCD) with curcumin. The improved solubility and stability of CurCD, combined with its superior proliferative, proangiogenic and anti-bacterial activity suggested that CurCD would be more beneficial than curcumin in wound healing. To enable the sustained release of CurCD at the wound site, a protease-responsive hydrogel (GHCD) was prepared with CurCD acting as a cross-linker. A comparative study using a skin excision model revealed that GHCD supported faster wound closure with improved angiogenesis and complete restoration of the epithelium. Apart from the establishment of CurCD as a wound healing agent, the study provides a novel carbon dot based approach for molecules with limitations of solubility and bioavailability.

Hypoxia reveals a new function of Foxn1 in the keratinocyte antioxidant defense system

Skin exposed to environmental threats, including injuries and oxidative stress, develops an efficient but not fully recognized system of repair and antioxidant protection. Here, using mass spectrometry analysis (LC-MS/MS), followed by in vitro and in vivo experiments, we provided evidence that Foxn1 in keratinocytes regulates elements of the electron transport chain and participates in the thioredoxin system (Txn2, Txnrd3, and Srxn1) induction, particularly in a hypoxic environment. We first showed that Foxn1 in keratinocytes upregulates glutathione thioredoxin reductase 3 (Txnrd3) protein expression, and high levels of Txnrd3 mRNA were detected in injured skin of Foxn1^+/+ mice. We also showed that Foxn1 strongly downregulated the Ccn2 protein expression, participating in epidermal reconstruction after injury. An in vitro assay revealed that Foxn1 controls keratinocyte migration, stimulating it under normoxia and suppressing it under hypoxia. Keratinocytes overexpressing Foxn1 and exposed to hypoxia displayed a reduced ability to promote angiogenesis by downregulating Vegfa expression. In conclusion, this study showed a new mechanism in which Foxn1, along with hypoxia, participates in the activation of antioxidant defense and controls the functional properties of keratinocytes.

Multifunctional and Smart Wound Dressings—A Review on Recent Research Advancements in Skin Regenerative Medicine

The healing of wounds is a dynamic function that necessitates coordination among multiple cell types and an optimal extracellular milieu. Much of the research focused on finding new techniques to improve and manage dermal injuries, chronic injuries, burn injuries, and sepsis, which are frequent medical concerns. A new research strategy involves developing multifunctional dressings to aid innate healing and combat numerous issues that trouble incompletely healed injuries, such as extreme inflammation, ischemic damage, scarring, and wound infection. Natural origin-based compounds offer distinct characteristics, such as excellent biocompatibility, cost-effectiveness, and low toxicity. Researchers have developed biopolymer-based wound dressings with drugs, biomacromolecules, and cells that are cytocompatible, hemostatic, initiate skin rejuvenation and rapid healing, and possess anti-inflammatory and antimicrobial activity. The main goal would be to mimic characteristics of fetal tissue regeneration in the adult healing phase, including complete hair and glandular restoration without delay or scarring. Emerging treatments based on biomaterials, nanoparticles, and biomimetic proteases have the keys to improving wound care and will be a vital addition to the therapeutic toolkit for slow-healing wounds. This study focuses on recent discoveries of several dressings that have undergone extensive pre-clinical development or are now undergoing fundamental research.

Deciphering the focuses and trends in skin regeneration research through bibliometric analyses

Increasing attention to skin regeneration has rapidly broadened research on the topic. However, no bibliometric analysis of the field’s research trends has yet been conducted. In response to this research gap, this study analyzed the publication patterns and progress of skin regeneration research worldwide using a bibliometric analysis of 1,471 papers comprising 1,227 (83.4%) original articles and 244 (16.6%) reviews sourced from a Web of Science search. Publication distribution was analyzed by country/region, institution, journal, and author. The frequency of keywords was assessed to prepare a bibliometric map of the development trends in skin regeneration research. China and the United States were the most productive countries in the field: China had the greatest number of publications at 433 (29.4%) and the United States had the highest H-index ranking (59 with 15,373 citations or 31.9%). Author keywords were classified into four clusters: stem cell, biomaterial, tissue engineering, and wound dressing. “Stem cells,” “chitosan,” “tissue engineering,” and “wound dressings” were the most frequent keywords in each cluster; therefore, they reflected the field’s current focus areas. “Immunomodulation,” “aloe vera,” “extracellular vesicles,” “injectable hydrogel,” and “three-dimensional (3D) bioprinting” were relatively new keywords, indicating that biomaterials for skin regeneration and 3D bioprinting are promising research hotspots in the field. Moreover, clinical studies on new dressings and techniques to accelerate skin regeneration deserve more attention. By uncovering current and future research hotspots, this analysis offers insights that may be useful for both new and experienced scholars striving to expand research and innovation in the field of skin regeneration.

Clinical and histopathological effects of ointment prepared from kombucha floating cellulose layer on wound healing and the activity of matrix metalloproteinase 1 in diabetic rats

Introduction: High blood glucose results in high levels of matrix metalloproteinases. Clinical and histopathological effects of the kombucha ointment on the healing of diabetic wounds were evaluated.

Materials and methods: This study was conducted at research Lab, Department of Micobiology, Falavarjan of Branch Islamic Azad University, Isfahan, Iran from October 2019 to September 2020. A 6 mm diameter ulcer was aseptically created on the back of forty-eight rats with streptozotocin-induced diabetes. The animals were randomly divided into 4 groups: the group that was treated with base ointment, the group that was treated with 10% kombucha ointment, the group that was treated with 20% kombucha ointment, and the group that received no ointment treatment. Then the rats in each group were divided to 4 sampling groups that were sampled on the second, fifth, tenth, and fourteenth days. Microscopic features, inflammation and vasculature and fibroblast infiltration, as well as the matrix metalloproteinase 1(MMP1) were evaluated on days 2, 5, 10, 14 after wound healing.

Results: 20% kombucha ointment let to inflammation and an angiogenesis decrease compared to those in the basic group and 10%-kombucha-ointment group. Also 20% kombucha ointment led to an increase in vascular remodeling and penetration of fibroblasts. MMP1 levels increased on the second (p < 0.001) and fifth days after wounding when treatrd with 10% and 20% kombucha ointment (p > 0.05). The expression of MMP1 decreased on the ten and fourteenth days when using 20% kombucha ointment compared to the control, placebo, and 10% kombucha ointment groups (p > 0.05).

Discussion: The histopatological finding indicated that both quantity and time duration of the treatment had significant effects on a degree of inflammation and angiogenesis.

Сonclusion: Ointment prepared from 20% scoby improved the healing of diabetic ulcers within 14 days.

Bacterial cellulose reinforced chitosan-based hydrogel with highly efficient self-healing and enhanced antibacterial activity for wound healing

Biocompatible hydrogels with versatile functions are highly desired for demanding the complicated tissue issues, including irregular site and motional wound. Herein, a bio-based hydrogel with multifunctional properties is designed based on quaternized chitosan and dialdehyde bacterial cellulose. As a functional wound dressing, the hydrogel shows rapid self-healing performance and injectable behaviors due to dynamic Schiff-base interactions and presents superior antibacterial activity against E. coli (gram-negative) and S. aureus (gram-positive). The constructed 3D hydrogel also exhibits proper compressive property, desired water retention capacity. To be mentioned, the hydrogel could mimic the structure of natural extracellular matrix (ECM) in the presence of bacterial cellulose nanofibers. Thus, the biopolymer-based hydrogel shows good biocompatibility in terms of cell proliferation and cell spreading. The prepared chitosan-based hydrogel with self-healing, antibacterial, and low cost will become a promising biomaterial for wound healing.

Biofabrication of ZnO/Malachite nanocomposite and its coating with chitosan to heal infectious wounds

Recently, nanocomposites produced from clays and metals coated with chitosan have shown wound healing activity. This study aimed to synthesize the zinc oxide/malachite nanocomposite (ZnO/Mlt-NC) and its coating form with chitosan (ZnO/Mlt/Chsn-NC). Physicochemical characterization of the produced nanocomposites was investigated. Biomedical effects of nanocomposites, such as in vivo and in vitro antibacterial activity, antioxidant properties, cytotoxicity, and modulation in the gene expressions of interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10), and transforming growth factor-β (TGF-β) and histopathological parameters, were also investigated. Expression intensities of basic fibroblast growth factor (bFGF) and tumor necrosis factor alpha (TNF-α) were also investigated by immunofluorescence staining. To investigate biomedical effects under in vivo conditions, infected wounds were induced and inoculated with Staphylococcus aureus (ATCC 25923), and Pseudomonas aeruginosa (ATCC 27853). The results indicated spherical ZnO nanoparticles on the surface of malachite and strong antibacterial activity and antioxidant properties. The ointments produced from the nanocomposites also exhibited wound healing activity. The administration of the ointments prepared from ZnO/Mlt, and ZnO/Mlt/Chsn NCs decreased the expressions of IL-1β, IL-6, and TNF-α, while it increased the expressions of IL-10, TGF-β and bFGF. In sum, the nanocomposites produced from ZnO, malachite, and chitosan had better biological activity than ZnO/Malachite nanocomposites. We suggest applying ZnO/Mlt/Chsn nanocomposites in the structure of ointments to treat infected wounds after future clinical studies.

Cellular Mechanisms in Acute and Chronic Wounds after PDT Therapy: An Update

PDT is a two-stage treatment that combines light energy with a photosensitizer designed to destroy cancerous and precancerous cells after light activation. Photosensitizers are activated by a specific wavelength of light energy, usually from a laser. The photosensitizer is nontoxic until it is activated by light. However, after light activation, the photosensitizer becomes toxic to the targeted tissue. Among sensitizers, the topical use of ALA, a natural precursor of protoporphyrin IX, a precursor of the heme group, and a powerful photosensitizing agent, represents a turning point for PDT in the dermatological field, as it easily absorbable by the skin. Wound healing requires a complex interaction and coordination of different cells and molecules. Any alteration in these highly coordinated events can lead to either delayed or excessive healing. The goal of this review is to elucidate the cellular mechanisms involved, upon treatment with ALA-PDT, in chronic wounds, which are often associated with social isolation and high costs in terms of care.

Investigation of the synergistic effect of platelet-rich plasma and polychromatic light on human dermal fibroblasts seeded chitosan/gelatin scaffolds for wound healing

Conventional wound healing treatments are insufficient for chronic wounds caused by factors such as senescence of fibroblasts, reduced growth factor synthesis, and poor angiogenesis. Recently, tissue engineering approaches have been investigated to develop effective therapies. In this study, a biochemical/biophysical stimulant-based 3D system was developed for the healing of chronic wounds. In this direction, genipin crosslinked chitosan (CHT)/gelatin (GEL) scaffolds were fabricated by freeze-drying and loaded with platelet-rich plasma (PRP). The scaffolds were seeded with human dermal fibroblasts and then, polychromatic light in near infrared region (NIR) was applied to the scaffolds for activating the platelets and stimulating the fibroblasts (photoactivation, PAC). Thus, fibroblasts were stimulated both chemically and physically by PRP and light, respectively. Cell migration, proliferation, morphology, gene expressions and reactive oxygen species (ROS) activity were evaluated in-vitro. Laminin and collagen 4 expressions that are important for extracellular matrix (ECM) formation, and PDGF (Platelet-derived growth factor) and VEGF (Vascular endothelial growth factor) expressions that are important for vascularization significantly increased in the presence of both PRP and light. Besides, PRP and light improved cell migration in 3D core-and shell model synergistically. Hydrogen peroxide content decreased in both PRP and light, indicating inhibition of ROS production. It was concluded that the stimulation of platelets with light in the NIR has a great potential to use for both platelets activation and stimulation of fibroblasts. As a result, an effective therapy can be developed for chronic wounds by using scaffold-based 3D systems together with PRP and photostimulation.

Transplantation of decellularised human amniotic membranes seeded with mesenchymal stem cell-educated macrophages into animal models

The reconstruction of chronic skin wounds remains a public health challenge in dermatology. Precisely controlling and monitoring the wound-healing process should result in enhanced outcomes for the patient. Cell-based therapies have shown great potential in medicine due to their immunomodulatory and healing properties. Herein, we produced activated macrophages by treating circulating monocytes with mesenchymal stem cell (MSC) supernatant. We also demonstrated the critical role of activated macrophages transplantation using amniotic membranes in accelerating wound healing in an animal wound model. The activated macrophages not only exhibited immunomodulatory cytokines like transforming growth factorβ (TGFβ) and interleukin 10 (and IL10) secretion but also showed attachment and proliferation ability on the amniotic membrane scaffold. Moreover, MSCs supernatant-treated cells also displayed significant ARG1, CD206, and IL 10 genes expression. Inspired by the in vitro results, we examined the in vivo therapeutic efficacy of the activated macrophage transplantation using an acellular amniotic membrane carrier in a full-thickness cutaneous wound model. The wound healing rate was significant in the group treated with macrophages generated via mesenchymal cell therapy seeded human amniotic membrane. There was less scarring in the wound sites after placing cell-scaffold constructs in the wound sites in the animal models. Overall, macrophages stimulated with mesenchymal cells' supernatant exhibited improved healing processes in incisional wounds by decreasing the inflammatory phase, increasing angiogenesis, and reducing scar tissue development.

The combination of mesoglycan and VEGF promotes skin wound repair by enhancing the activation of endothelial cells and fibroblasts and their cross-talk

Skin wound healing requires accurate therapeutic topical managements to accelerate tissue regeneration. Here, for the first time, we found that the association mesoglycan/VEGF has a strong pro-healing activity. In detail, this combination induces angiogenesis in human endothelial cells promoting in turn fibroblasts recruitment. These ones acquire a notable ability to invade the matrigel coating and to secrete an active form of metalloproteinase 2 in presence of endothelial cells treated with mesoglycan/VEGF. Next, by creating intrascapular lesions on the back of C57Bl6 mice, we observed that the topical treatments with the mesoglycan/VEGF promotes the closure of wounds more than the single substances beside the control represented by a saline solution. As revealed by eosin/hematoxylin staining of mice skin biopsies, treatment with the combination mesoglycan/VEGF allows the formation of a well-structured matrix with a significant number of new vessels. Immunofluorescence analyses have revealed the presence of endothelial cells at the closed region of wounds, as evaluated by CD31, VE-cadherin and fibronectin staining and of activated fibroblasts assessed by vimentin, col1A and FAP1α. These results encourage defining the association mesoglycan/VEGF to activate endothelial and fibroblast cell components in skin wound healing promoting the creation of new vessels and the deposition of granulation tissue.

Exosomes Derived From Umbilical Cord Mesenchymal Stem Cells Treat Cutaneous Nerve Damage and Promote Wound Healing

Wound repair is a key step in the treatment of skin injury caused by burn, surgery, and trauma. Various stem cells have been proven to promote wound healing and skin regeneration as candidate seed cells. Therefore, exosomes derived from stem cells are emerging as a promising method for wound repair. However, the mechanism by which exosomes promote wound repair is still unclear. In this study, we reported that exosomes derived from umbilical cord mesenchymal stem cells (UC-MSCs) promote wound healing and skin regeneration by treating cutaneous nerve damage. The results revealed that UC-MSCs exosomes (UC-MSC-Exo) promote the growth and migration of dermal fibroblast cells. In in vitro culture, dermal fibroblasts could promote to nerve cells and secrete nerve growth factors when stimulated by exosomes. During the repair process UC-MSC-Exo accelerated the recruitment of fibroblasts at the site of trauma and significantly enhanced cutaneous nerve regeneration in vivo. Interestingly, it was found that UC-MSC-Exo could promote wound healing and skin regeneration by recruiting fibroblasts, stimulating them to secrete nerve growth factors (NGFs) and promoting skin nerve regeneration. Therefore, we concluded that UC-MSC-Exo promote cutaneous nerve repair, which may play an important role in wound repair and skin regeneration.

Development of Lepidium sativum Extracts/PVA Electrospun Nanofibers as Wound Healing Dressing

Lepidium sativum L. (Garden cress/Hab El Rashad) (Ls), family Brassicaceae, has considerable importance in traditional medicine worldwide because of its antioxidant and anti-inflammatory activities. Ls fruits were used in Ayurvedic medicines as a useful drug for injuries, skin, and eye diseases. The aim of this study was to examine the effectiveness of the total ethanol extract (TEE) and polysaccharide (Poly) of Ls seeds loaded on poly(vinyl alcohol) (PVA) nanofibers (NFs) as a wound healing dressing and to correlate the activity with the constituents of each. TEE and Poly were phytochemically analyzed qualitatively and quantitatively. Qualitative analysis proved the presence of phenolic acids, flavonoids, tannins, sterols, triterpenes, and mucilage. Meanwhile, quantitative determinations were carried out spectrophotometrically for total phenolic and total flavonoid contents. High-performance liquid chromatography (HPLC) for TEE identified 15 phenolic acids and flavonoid compounds, with gallic acid and catechin as the majors. Separation, purification, and identification of the major compounds were achieved through a Puriflash system, column Sephadex LH20, and spectroscopic data (¹H, ¹³C NMR, and UV). Eight compounds (gallic acid, catechin, rutin, kaempferol-3-O-rutinoside, quercetin-3-O-rhamnoside, kaempferol-3-O-rhamnoside, quercetin, and kaempferol) were obtained. Gas-liquid chromatography (GLC) analysis for Poly identified 11 compounds, with galactose being the main. The antioxidant activity for both extracts was measured by three different methods based on different mechanisms: 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing ability of plasma (FRAP), and 3-ethylbenzothiazoline-6-sulfonic acid (ABTS). TEE has the highest effectiveness as an antioxidant agent with IC₅₀ 82.6 ± 8.35 μg/mL for DPPH and 772.47 and 758.92 μM Trolox equivalent/mg extract for FRAP and ABTS, respectively. The PVA nanofibers (NFs) for each sample were fabricated by electrospinning. The fabricated NFs were characterized by SEM and Fourier transform infrared spectroscopy (FTIR); the results revealed successful encapsulation of TEE and Poly in the prepared NFs. Moreover, the swelling index of TEE in the prepared NFs shows that it is the most appropriate for use as a wound dressing. Cytotoxicity studies indicated a high cell viability with IC₅₀ 216 μg/mL and 1750 μg/mL for TEE and Poly, respectively. Moreover, the results revealed that nanofibers possess higher cell viability compared to solutions with the same sample quantities: 9-folds for TEE and 4-folds for Poly of amount 400 μg. The in vitro wound healing test showed that the TEE nanofibers performed better than Poly nanofibers in accelerating wound healing, with 90% for TEE, more than that for the Poly extract (82%), after 48 h. These findings implied that the incorporation of TEE in PVA nanofibers was more efficient than incorporation of Poly in improving the biological activity in wound healing. In conclusion, the TEE and polysaccharides of L. sativum L seed are ideal candidates for nanofibrous wound dressings. Furthermore, the contents of phenolic acids and flavonoids in TEE, which have potential antioxidant activity, make the TEE of L. sativum more favorable for wound healing dressing.

Role of Cultured Skin Fibroblasts in Regenerative Dermatology

The skin, as the largest organ, covers the entire outer part of the body, and since this organ is directly exposed to microbial, thermal, mechanical and chemical damage, it may be destroyed by factors such as acute trauma, chronic wounds or even surgical interventions. Cell therapy is one of the most important procedures to treat skin lesions. Fibroblasts are cells that are responsible for the synthesis of collagen, elastin, and the organization of extracellular matrix (ECM) components and have many vital functions in wound healing processes. Today, cultured autologous fibroblasts are used to treat wrinkles, scars, wounds and subcutaneous atrophy. The results of many studies have shown that fibroblasts can be effective and beneficial in the treatment of skin lesions. On the other hand, skin substitutes are used as a regenerative model to improve and regenerate the skin. The use of these alternatives, restorative medicine and therapeutic cells such as fibroblasts has tremendous potential in the treatment of skin diseases and can be a new window for the treatment of diseases with no definitive treatment. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description ofthese Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Exploring Silk Sericin for Diabetic Wounds: An In Situ-Forming Hydrogel to Protect against Oxidative Stress and Improve Tissue Healing and Regeneration

Chronic wounds are one of the most frequent complications that are associated with diabetes mellitus. The overproduction of reactive oxygen species (ROS) is a key factor in the delayed healing of a chronic wound. In the present work, we develop a novel in situ-forming silk sericin-based hydrogel (SSH) that is produced by a simple methodology using horseradish peroxidase (HRP) crosslinking as an advanced dressing for wound healing. The antioxidant and angiogenic effects were assessed in vitro and in vivo after in situ application using an excisional wound-healing model in a genetically-induced diabetic db/db mice and though the chick embryo choriollantoic membrane (CAM) assay, respectively. Wounds in diabetic db/db mice that were treated with SSH closed with reduced granulation tissue, decreased wound edge distance, and wound thickness, when compared to Tegaderm, a dressing that is commonly used in the clinic. The hydrogel also promoted a deposition of collagen fibers with smaller diameter which may have had a boost effect in re-epithelialization. SSH treatment slightly induced two important endogenous antioxidant defenses, superoxide dismutase and catalase. A CAM assay made it possible to observe that SSH led to an increase in the number of newly formed vessels without inducing an inflammatory reaction. The present hydrogel may result in a multi-purpose technology with angiogenic, antioxidant, and anti-inflammatory properties, while advancing efficient and organized tissue regeneration.

In vitro and in vivo evaluation of porous alginate hydrogel containing retinoic acid for skin wound healing applications

The current study’s main aim was to fabricate and evaluate alginate (Alg) hydrogel containing retinoic acid (RA) as wound healing materials. Different RA concentrations (2, 10, and 50% w/w) were incorporated into the hydrogel. The results showed that the prepared hydrogels had a porous structure with a pore size of 69.69 ± 22.1 µm for pure Alg hydrogel and 78.44 ± 27.8 µm for Alg/RA hydrogel. The swelling measurement showed that the hydrogels swelled up to 65% and the incorporation of RA reduced the degree of swelling . The in vitro studies confirmed the hemo- and biocompatibility of the Alg/RA 2% and increasing the RA concentration induced hemolysis and toxic effects. The animal studies showed that the lowest RA concentration resulted in the best treatment outcome while increasing the RA concentration suppressed the healing process. In conclusion, these results showed that RA induced wound healing process at low concentration, and the prepared hydrogel could be used as the wound healing materials.

pH-responsive silica nanoparticles for the treatment of skin wound infections

Chronic wounds are not only a burden for patients but also challenging for clinic treatment due to biofilm formation. Here, we utilized the phenomenon that chronic wounds possess an elevated local pH of 8.9 and developed pH-sensitive silica nanoparticles (SiNPs) to achieve a targeted drug release on alkaline wounds and optimized drug utility. Chlorhexidine (CHX), a disinfectant and antiseptic, was loaded into SiNPs as the model drug. The loaded CHX displayed a release 4 - 5 fold higher at pH 8.0 and 8.5 than at pH 6.5, 7.0 and 7.4. CHX-SiNPs furthermore exhibited a distinctive antibacterial activity at pH 8.0 and 8.5 against both Gram-negative and -positive bacterial pathogens, while no cytotoxicity was found according to cell viability analysis. The CHX-SiNPs were further formulated into alginate hydrogels to allow ease of use. The antibacterial efficacy of CHX-SiNPs was then studied with artificial wounds on ex vivo human skin. Treatment with CHX-SiNPs enabled nearly a 4-lg reduction of the viable bacterial cells, and the alginate formulated CHX-SiNPs led to almost a 3-lg reduction compared to the negative controls. The obtained results demonstrated that CHX-SiNPs are capable of efficient pH-triggered drug release, leading to high antibacterial efficacy. Moreover, CHX-SiNPs enlighten clinic potential towards the treatment of chronic wound infections. STATEMENT OF SIGNIFICANCE: A platform for controlled drug release at a relatively high pH value i.e., over 8, was established by tuning the physical structures of silica nanoparticles (SiNPs). Incorporation of chlorhexidine, an antimicrobial agent, into the fabricated SiNPs allowed a distinctive inhibition of bacterial growth at alkaline pHs, but not at acidic pHs. The efficacy of the SiNPs loaded with chlorhexidine in treating wound infections was further validated by utilizing ex vivo human skin samples. The presented work demonstrates clinic potential of employing alkaline pH as a non-invasive stimulus to achieve on-demand delivery of antimicrobials through SiNPs, showcasing a valuable approach to treating bacterial infections on chronic wounds.

Electrospun nanofibers based on carboxymethyl cellulose/polyvinyl alcohol as a potential antimicrobial wound dressing

In this work, citric acid-based quantum dots (CA-QDs) as a novel and safe crosslinked agent was applied in different feeding ratios (5-15 wt%) to synthesize carboxymethyl cellulose/polyvinyl alcohol (CMC/PVA) nanofibers (NFs) for the first time. Colistin (CL) as an antibacterial agent was also loaded (2 w/w%) during the synthesizing process of CMC/PVA electrospun NFs to trigger antimicrobial properties. The morphological, hydrophilic, and mechanical properties of the prepared NFs were fully investigated with different techniques. The electrospun NFs with crosslinking ratios of 10 wt% CA-QDs revealed appropriate mechanical properties. According to cell culture data, the prepared NFs demonstrated good cytocompatibility against HFF-1 cells (over 80% cell viability). Remarkably, CL-loaded NFs showed desired antibacterial efficacy against S. aureus, E. coli, K. pneumoniae, and P. aeruginosa with 1.0-1.4, 1.3-1.4, 0.8-1.0, and 1.3-1.5 cm inhibition zones, respectively. These outcomes suggested that the fabricated NFs can be useful as wound healing scaffolds.

Solid Dispersions Incorporated into PVP Films for the Controlled Release of Trans-Resveratrol: Development, Physicochemical and In Vitro Characterizations and In Vivo Cutaneous Anti-Inflammatory Evaluation

Trans-resveratrol can promote various dermatological effects. However, its high crystallinity decreases its solubility and bioavailability. Therefore, solid dispersions have been developed to promote its amorphization; even so, they present as powders, making cutaneous controlled drug delivery unfeasible and an alternative necessary for their incorporation into other systems. Thus, polyvinylpyrrolidone (PVP) films were chosen with the aim of developing a controlled delivery system to treat inflammation and bacterial infections associated with atopic dermatitis. Four formulations were developed: two with solid dispersions (and trans-resveratrol) and two as controls. The films presented with uniformity, as well as bioadhesive and good barrier properties. X-ray diffraction showed that trans-resveratrol did not recrystallize. Fourier-transform infrared spectroscopy (FT-IR) and thermal analysis evidenced good chemical compatibilities. The in vitro release assay showed release values from 82.27 ± 2.60 to 92.81 ± 2.50% (being a prolonged release). In the in vitro retention assay, trans-resveratrol was retained in the skin, over 24 h, from 42.88 to 53.28%. They also had low cytotoxicity over fibroblasts. The in vivo assay showed a reduction in inflammation up to 66%. The films also avoided Staphylococcus aureus’s growth, which worsens atopic dermatitis. According to the results, the developed system is suitable for drug delivery and capable of simultaneously treating inflammation and infections related to atopic dermatitis.

Genipin-Crosslinking Effects on Biomatrix Development for Cutaneous Wound Healing: A Concise Review

Split skin graft (SSG), a standard gold treatment for wound healing, has numerous limitations such as lack of fresh skin to be applied, tedious process, severe scarring, and keloid formation followed by higher risks of infection. Thus, there is a gap in producing polymeric scaffolds as an alternative for wound care management. Bioscaffold is the main component in tissue engineering technology that provides porous three-dimensional (3D) microarchitecture for cells to survive. Upon skin tissue reconstruction, the 3D-porous structure ensures sufficient nutrients and gaseous diffusion and cell penetration that improves cell proliferation and vascularization for tissue regeneration. Hence, it is highly considered a promising candidate for various skin wound healing applications. To date, natural-based crosslinking agents have been extensively used to tailor the physicochemical and mechanical properties of the skin biomatrix. Genipin (GNP) is preferable to other plant-based crosslinkers due to its biological activities, such as antiinflammatory and antioxidant, which are key players to boost skin wound healing. In addition, it has shown a noncytotoxic effect and is biocompatible with human skin cells. This review validated the effects of GNP in biomatrix fabrication for skin wound healing from the last 7 years of established research articles and stipulated the biomaterial development-scale point of view. Lastly, the possible role of GNP in the skin wound healing cascade is also discussed. Through the literature output, it can be concluded that GNP has the capability to increase the stability of biomatrix and maintain the skin cells viability, which will contribute in accelerating wound healing.

Advancements in Skin Delivery of Natural Bioactive Products for Wound Management: A Brief Review of Two Decades

Application of modern delivery techniques to natural bioactive products improves their permeability, bioavailability, and therapeutic efficacy. Many natural products have desirable biological properties applicable to wound healing but are limited by their inability to cross the stratum corneum to access the wound. Over the past two decades, modern systems such as microneedles, lipid-based vesicles, hydrogels, composite dressings, and responsive formulations have been applied to natural products such as curcumin or aloe vera to improve their delivery and efficacy. This article reviews which natural products and techniques have been formulated together in the past two decades and the success of these applications for wound healing. Many cultures prefer natural-product-based traditional therapies which are often cheaper and more available than their synthetic counterparts. Improving natural products’ effect can provide novel wound-healing therapies for those who trust traditional compounds over synthetic drugs to reduce medical inequalities.

Biomaterials-Based Regenerative Strategies for Skin Tissue Wound Healing

Skin tissue wound healing proceeds through four major stages, including hematoma formation, inflammation, and neo-tissue formation, and culminates with tissue remodeling. These four steps significantly overlap with each other and are aided by various factors such as cells, cytokines (both anti- and pro-inflammatory), and growth factors that aid in the neo-tissue formation. In all these stages, advanced biomaterials provide several functional advantages, such as removing wound exudates, providing cover, transporting oxygen to the wound site, and preventing infection from microbes. In addition, advanced biomaterials serve as vehicles to carry proteins/drug molecules/growth factors and/or antimicrobial agents to the target wound site. In this review, we report recent advancements in biomaterials-based regenerative strategies that augment the skin tissue wound healing process. In conjunction with other medical sciences, designing nanoengineered biomaterials is gaining significant attention for providing numerous functionalities to trigger wound repair. In this regard, we highlight the advent of nanomaterial-based constructs for wound healing, especially those that are being evaluated in clinical settings. Herein, we also emphasize the competence and versatility of the three-dimensional (3D) bioprinting technique for advanced wound management. Finally, we discuss the challenges and clinical perspective of various biomaterial-based wound dressings, along with prospective future directions. With regenerative strategies that utilize a cocktail of cell sources, antimicrobial agents, drugs, and/or growth factors, it is expected that significant patient-specific strategies will be developed in the near future, resulting in complete wound healing with no scar tissue formation.

A Review on Recent Progress of Stingless Bee Honey and Its Hydrogel-Based Compound for Wound Care Management

Stingless bee honey has a distinctive flavor and sour taste compared to Apis mellifera honey. Currently, interest in farming stingless bees is growing among rural residents to meet the high demand for raw honey and honey-based products. Several studies on stingless bee honey have revealed various therapeutic properties for wound healing applications. These include antioxidant, antibacterial, anti-inflammatory, and moisturizing properties related to wound healing. The development of stingless bee honey for wound healing applications, such as incorporation into hydrogels, has attracted researchers worldwide. As a result, the effectiveness of stingless bee honey against wound infections can be improved in the future to optimize healing rates. This paper reviewed the physicochemical and therapeutic properties of stingless bee honey and its efficacy in treating wound infection, as well as the incorporation of stingless bee honey into hydrogels for optimized wound dressing.

A Review on Current Designation of Metallic Nanocomposite Hydrogel in Biomedical Applications

In the past few decades, nanotechnology has been receiving significant attention globally and is being continuously developed in various innovations for diverse applications, such as tissue engineering, biotechnology, biomedicine, textile, and food technology. Nanotechnological materials reportedly lack cell-interactive properties and are easily degraded into unfavourable products due to the presence of synthetic polymers in their structures. This is a major drawback of nanomaterials and is a cause of concern in the biomedicine field. Meanwhile, particulate systems, such as metallic nanoparticles (NPs), have captured the interest of the medical field due to their potential to inhibit the growth of microorganisms (bacteria, fungi, and viruses). Lately, researchers have shown a great interest in hydrogels in the biomedicine field due to their ability to retain and release drugs as well as to offer a moist environment. Hence, the development and innovation of hydrogel-incorporated metallic NPs from natural sources has become one of the alternative pathways for elevating the efficiency of therapeutic systems to make them highly effective and with fewer undesirable side effects. The objective of this review article is to provide insights into the latest fabricated metallic nanocomposite hydrogels and their current applications in the biomedicine field using nanotechnology and to discuss the limitations of this technology for future exploration. This article gives an overview of recent metallic nanocomposite hydrogels fabricated from bioresources, and it reviews their antimicrobial activities in facilitating the demands for their application in biomedicine. The work underlines the fabrication of various metallic nanocomposite hydrogels through the utilization of natural sources in the production of biomedical innovations, including wound healing treatment, drug delivery, scaffolds, etc. The potential of these nanocomposites in relation to their mechanical strength, antimicrobial activities, cytotoxicity, and optical properties has brought this technology into a new dimension in the biomedicine field. Finally, the limitations of metallic nanocomposite hydrogels in terms of their methods of synthesis, properties, and outlook for biomedical applications are further discussed.

Adaptive injectable carboxymethyl cellulose/poly (γ-glutamic acid) hydrogels promote wound healing

The clinical acceleration of skin autogenous healing remains a great challenge, especially in the early stage after injury. In this work, a novel directly injectable hydrogel with high self-adaptability is designed as a provisional matrix to close the apposition of wound edges, using carboxymethyl cellulose and poly (γ-glutamic acid) through Schiff-base reaction. Benefiting from the dynamic covalent cross-linking structure, the functional biodegradable hydrogels are easy to prepare (gel time 5-180 s), demonstrating adequate mechanical strength (40-120 kPa), anti-fatigue abilities, and rapid self-healing (5-10 min at skin defect). Furthermore, the hydrogels exhibit biocompatibility and proliferation-promoting activity with murine fibroblasts. In the full-thickness dermal animal models, it significantly promoted collagen deposition, skin-function restoration, and VEGF expression. This hydrogel shows potential as a dressing available for skin regeneration during the healing of dermal injuries.

Exploration of Lipid-Based Nanocarriers as Drug Delivery Systems in Diabetic Foot Ulcer

Diabetes mellitus is a chronic manifestation characterized by high levels of glucose in the blood resulting in several complications including diabetic wounds and ulcers, which predominantly require a longer duration of treatment and adversely affect the quality of life of the patients. Nanotechnology-based therapeutics (both intrinsic and extrinsic types) have emerged as a promising treatment in diabetic foot ulcer/chronic wounds owing to their unique characteristics and specific functional properties. In this review, we have focused on the significance of the use of lipids in the healing of diabetic ulcers, their interaction with the injured skin, and recent trends in lipid-based nanocarriers for the healing of diabetic wounds. Lipid nanocarriers are also being investigated for gene therapy in diabetic wound healing to encapsulate nucleic acids such as siRNA and miRNA, which could silence the expression of inflammatory cytokines overexpressed in chronic wounds. Additionally, these are also being explored for encapsulating proteins, peptides, growth factors, and other biological genetic material as therapeutic agents. Lipid-based nanocarriers encompassing a wide variety of carriers such as liposomes, niosomes, ethosomes, solid lipid nanoparticles, and lipidoid nanoparticles that are explored for the treatment of foot ulcers supplemented with relevant research studies have been discussed in the present review. Lipid-based nanodrug delivery systems have demonstrated promising wound healing potential, particularly in diabetic conditions due to the enhanced efficacy of the entrapped active molecules.

Droplet-based bioprinting enables the fabrication of cell–hydrogel–microfibre composite tissue precursors

Composites offer the option of coupling the individual benefits of their constituents to achieve unique material properties, which can be of extra value in many tissue engineering applications. Strategies combining hydrogels with fibre-based scaffolds can create tissue constructs with enhanced biological and structural functionality. However, developing efficient and scalable approaches to manufacture such composites is challenging. Here, we use a droplet-based bioprinting system called reactive jet impingement (ReJI) to integrate a cell-laden hydrogel with a microfibrous mesh. This system uses microvalves connected to different bioink reservoirs and directed to continuously jet bioink droplets at one another in mid-air, where the droplets react and form a hydrogel that lands on a microfibrous mesh. Cell–hydrogel–fibre composites are produced by embedding human dermal fibroblasts at two different concentrations (5 × 106 and 30 × 106 cells/mL) in a collagen–alginate–fibrin hydrogel matrix and bioprinted onto a fibre-based substrate. Our results show that both types of cell–hydrogel–microfibre composite maintain high cell viability and promote cell–cell and cell–biomaterial interactions. The lower fibroblast density triggers cell proliferation, whereas the higher fibroblast density facilitates faster cellular organisation and infiltration into the microfibres. Additionally, the fibrous component of the composite is characterised by high swelling properties and the quick release of calcium ions. The data indicate that the created composite constructs offer an efficient way to create highly functional tissue precursors for laminar tissue engineering, particularly for wound healing and skin tissue engineering applications.

Graphic abstract