Peptide-Modified Chitosan Hydrogels Accelerate Skin Wound Healing by Promoting Fibroblast Proliferation, Migration, and Secretion

Therapeutic Potential of Nanocarrier Mediated Delivery of Peptides for Wound Healing: Current Status, Challenges and Future Prospective

Wound healing presents a complex physiological process that involves a sequence of events orchestrated by various cellular and molecular mechanisms. In recent years, there has been growing interest in leveraging nanomaterials and peptides to enhance wound healing outcomes. Nanocarriers offer unique properties such as high surface area-to-volume ratio, tunable physicochemical characteristics, and the ability to deliver therapeutic agents in a controlled manner. Similarly, peptides, with their diverse biological activities and low immunogenicity, hold great promise as therapeutics in wound healing applications. In this review, authors explore the potential of peptides as bioactive components in wound healing formulations, focusing on their antimicrobial, anti-inflammatory, and pro-regenerative properties. Despite the significant progress made in this field, several challenges remain, including the need for standardized characterization methods, optimization of biocompatibility and safety profiles, and translation from bench to bedside. Furthermore, developing multifunctional nanomaterial-peptide hybrid systems represents promising avenues for future research. Overall, the integration of nanomaterials made up of natural or synthetic polymers with peptide-based formulations holds tremendous therapeutic potential in advancing the field of wound healing and improving clinical outcomes for patients with acute and chronic wounds.

Biomaterials for immunomodulation in wound healing

The substantial economic impact of non-healing wounds, scarring, and burns stemming from skin injuries is evident, resulting in a financial burden on both patients and the healthcare system. This review paper provides an overview of the skin's vital role in guarding against various environmental challenges as the body's largest protective organ and associated developments in biomaterials for wound healing. We first introduce the composition of skin tissue and the intricate processes of wound healing, with special attention to the crucial role of immunomodulation in both acute and chronic wounds. This highlights how the imbalance in the immune response, particularly in chronic wounds associated with underlying health conditions such as diabetes and immunosuppression, hinders normal healing stages. Then, this review distinguishes between traditional wound-healing strategies that create an optimal microenvironment and recent peptide-based biomaterials that modulate cellular processes and immune responses to facilitate wound closure. Additionally, we highlight the importance of considering the stages of wounds in the healing process. By integrating advanced materials engineering with an in-depth understanding of wound biology, this approach holds promise for reshaping the field of wound management and ultimately offering improved outcomes for patients with acute and chronic wounds.

Precise Engineering of Growth Factor Presentation Using Extracellular Microenvironment-Mimicking Microfluidic Microparticles

One of the main challenges in tissue engineering is finding a way to deliver specific growth factors (GFs) with precise spatiotemporal control over their presentation. Here, we report a novel strategy for generating microscale carriers with enhanced affinity for high content loading suitable for the sustained and localized delivery of GFs. Our developed microparticles can be injected locally and sustainably release encapsulated growth factors for up to 28 days. Fine-tuning of particles' size, affinity, microstructures, and release kinetics is achieved using a microfluidic system along with bioconjugation techniques. We also describe an innovative 3D micromixer platform to control the formation of core-shell particles based on superaffinity using a polymer-peptide conjugate for further tuning of release kinetics and delayed degradation. Chitosan shells block the burst release of encapsulated GFs and enable their sustained delivery for up to 10 days. The matched release profiles and degradation provide the local tissues with biomimetic, developmental-biologic-compatible signals to maximize regenerative effects. The versatility of this approach is verified using three different therapeutic proteins, including human bone morphogenetic protein-2 (rhBMP-2), vascular endothelial growth factor (VEGF), and stromal cell-derived factor 1 (SDF-1α). As in vivo morphogenesis is typically driven by the combined action of several growth factors, the proposed technique can be developed to generate a library of GF-loaded particles with designated release profiles.

Immunomodulatory hydrogels for skin wound healing: cellular targets and design strategy

Skin wounds significantly impact the global health care system and represent a significant burden on the economy and society due to their complicated dynamic healing processes, wherein a series of immune events are required to coordinate normal and sequential healing phases, involving multiple immunoregulatory cells such as neutrophils, macrophages, keratinocytes, and fibroblasts, since dysfunction of these cells may impede skin wound healing presenting persisting inflammation, impaired vascularization, and excessive collagen deposition. Therefore, cellular target-based immunomodulation is promising to promote wound healing as cells are the smallest unit of life in immune response. Recently, immunomodulatory hydrogels have become an attractive avenue to promote skin wound healing. However, a detailed and comprehensive review of cellular targets and related hydrogel design strategies remains lacking. In this review, the roles of the main immunoregulatory cells participating in skin wound healing are first discussed, and then we highlight the cellular targets and state-of-the-art design strategies for immunomodulatory hydrogels based on immunoregulatory cells that cover defect, infected, diabetic, burn and tumor wounds and related scar healing. Finally, we discuss the barriers that need to be addressed and future prospects to boost the development and prosperity of immunomodulatory hydrogels.

Advancements and applications of upconversion nanoparticles in wound dressings

Wound healing is a complex process that requires effective management to prevent infections and promote efficient tissue regeneration. In recent years, upconversion nanoparticles (UCNPs) have emerged as promising materials for wound dressing applications due to their unique optical properties and potential therapeutic functionalities. These nanoparticles possess enhanced antibacterial properties when functionalized with antibacterial agents, helping to prevent infections, a common complication in wound healing. They can serve as carriers for controlled drug delivery, enabling targeted release of therapeutic agents to the wound site, allowing for tailored treatment and optimal healing conditions. These nanoparticles possess the ability to convert near-infrared (NIR) light into the visible and/or ultraviolet (UV) regions, making them suitable for therapeutic (photothermal therapy and photodynamic therapy) and diagnostic applications. In the context of wound healing, these nanoparticles can be combined with other materials such as hydrogels, fibers, metal-organic frameworks (MOFs), graphene oxide, etc., to enhance the healing process and prevent the growth of microbial infections. Notably, UCNPs can act as sensors for real-time monitoring of the wound healing progress, providing valuable feedback to healthcare professionals. Despite their potential, the use of UCNPs in wound dressing applications faces several challenges. Ensuring the stability and biocompatibility of UCNPs under physiological conditions is crucial for their effective integration into dressings. Comprehensive safety and efficacy evaluations are necessary to understand potential risks and optimize UCNP-based dressings. Scalability and cost-effectiveness of UCNP synthesis and manufacturing processes are important considerations for practical applications. In addition, efficient incorporation of UCNPs into dressings, achieving uniform distribution, poses an important challenge that needs to be addressed. Future research should prioritize addressing concerns regarding stability and biocompatibility, efficient integration into dressings, rigorous safety evaluation, scalability, and cost-effectiveness. The purpose of this review is to critically evaluate the advantages, challenges, and key properties of UCNPs in wound dressing applications to provide insights into their potential as innovative solutions for enhancing wound healing outcomes. We have provided a detailed description of various types of smart wound dressings, focusing on the synthesis and biomedical applications of UCNPs, specifically their utilization in different types of wound dressings.

Four-Arm Polymer-Guided Formation of Curcumin-Loaded Flower-Like Porous Microspheres as Injectable Cell Carriers for Diabetic Wound Healing

Stem cell injection is an effective approach for treating diabetic wounds; however, shear stress during injections can negatively affect their stemness and cell growth. Cell-laden porous microspheres can provide shelter for bone mesenchymal stem cells (BMSC). Herein, curcumin-loaded flower-like porous microspheres (CFPM) are designed by combining phase inversion emulsification with thermally induced phase separation-guided four-arm poly (l-lactic acid) (B-PLLA). Notably, the CFPM shows a well-defined surface topography and inner structure, ensuring a high surface area to enable the incorporation and delivery of a large amount of -BMSC and curcumin. The BMSC-carrying CFPM (BMSC@CFPM) maintains the proliferation, retention, and stemness of -BMSCs, which, in combination with their sustainable curcumin release, facilitates the endogenous production of growth/proangiogenic factors and offers a local anti-inflammatory function. An in vivo bioluminescence assay demonstrates that BMSC@CFPM can significantly increase the retention and survival of BMSC in wound sites. Accordingly, BMSC@CFPM, with no significant systemic toxicity, could significantly accelerate diabetic wound healing by promoting angiogenesis, collagen reconstruction, and M2 macrophage polarization. RNA sequencing further unveils the mechanisms by which BMSC@CFPM promotes diabetic wound healing by increasing -growth factors and enhancing angiogenesis through the JAK/STAT pathway. Overall, BMSC@CFPM represents a potential therapeutic tool for diabetic wound healing.

Fabrication and Bioactivity of Peptide-Conjugated Biomaterial Tissue Engineering Constructs

Tissue engineering combines materials engineering, cells and biochemical factors to improve, restore or replace various types of biological tissues. A nearly limitless combination of these strategies can be combined, providing a means to augment the function of a number of biological tissues such as skin tissue, neural tissue, bones, and cartilage. Compounds such as small molecule therapeutics, proteins, and even living cells have been incorporated into tissue engineering constructs to influence biological processes at the site of implantation. Peptides have been conjugated to tissue engineering constructs to circumvent limitations associated with conjugation of proteins or incorporation of cells. This review highlights various contemporary examples in which peptide conjugation is used to overcome the disadvantages associated with the inclusion of other bioactive compounds. This review covers several peptides that are commonly used in the literature as well as those that do not appear as frequently to provide a broad scope of the utility of the peptide conjugation technique for designing constructs capable of influencing the repair and regeneration of various bodily tissues. Additionally, a brief description of the construct fabrication techniques encountered in the covered examples and their advantages in various tissue engineering applications is provided.

Smart thermosensitive poloxamer hydrogels loaded with Nr-CWs for the treatment of diabetic wounds

The treatment of diabetic wound is a focus issue. At present, the Nocardia rubra cell wall skeleton (Nr-CWS) has been proved proven to promote angiogenesis and wound repair. Unfortunately, the high-glucose diabetic wound environment makes many drugs unable to be released effectively, and soon be removed. Smart thermosensitive poloxamer hydrogel (TH) is an ideal and adjustable drug delivery platform compatible with most living tissues. Here, a multifunctional composite thermosensitive hydrogel was developed. A mixture of poloxamers 407 and 188 as the gel matrix, and then it was physically mixed with Nr-CWS. The delivery vehicle not only controlled its release stably, preventing degradation in vitro, but also showed good affinity in vitro. In vivo, compared with thermosensitive poloxamer hydrogel alone or the direct use of Nr-CWS, the thermosensitive poloxamer hydrogel loaded with Nr-CWS promoted the proliferation of vascular endothelial cells effectively, resulting in increased expression of derma-related structural proteins and enhanced angiogenesis and wound healing. This study indicated that the angiogenesis and skin regeneration brought by Nr-CWS hydrogel are related to the activation of phosphatidylinositol 3 kinase and protein kinase B, Janus kinase/signal transducer and activator of transcription, and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase signaling pathways.

Pharmacodynamics of Dracorhodin Perchlorate and Its Inflammation-Targeting Emulsion Gel for Wound Healing

The mechanism of dracorhodin perchlorate for the repair of rat skin wounds was investigated. In order to screen a more favorable drug delivery system for wound repair, the therapeutic effect of dracorhodin perchlorate inflammation-targeted emulsion gel was compared with that of non-targeted emulsion gel on rat wounds. Compared with non-targeted emulsion gels, inflammation-targeted emulsion gels had a better transdermal penetration and lower potentials (−51.6 mV and −17.1 mV, respectively). The recovery of the wound from the dracorhodin perchlorate inflammation targeted emulsion gel group was better than that of the dracorhodin perchlorate inflammation non-targeted emulsion gel group and the positive drug group. Compared with the no-target emulsion gel group, the bFGF expression on day 7 and the EGF expression on day 14 in the targeted emulsion group showed 45.5% and 49.9% improvement, respectively. Pathological tissue slices showed that the epidermis, dermis, and basal layer inflammatory cells in the inflammation-targeted emulsion gel group and non-targeted emulsion gel group were significantly reduced, the granulation tissue proliferation was obvious, and the inflammation-targeted emulsion gel group was more effective. The results proved that dracorhodin perchlorate had a repairing effect on rat skin wounds, and its mechanism might be related to the promotion of the expression of EGF and bFGF in tissues.

Investigation of construction and characterization of carboxymethyl chitosan - sodium alginate nanoparticles to stabilize Pickering emulsion hydrogels for curcumin encapsulation and accelerating wound healing

Limitations in compatibility and effectiveness in delivering bioactive compounds often make it prohibitively difficult to apply Pickering emulsions in wound dressing. In this research, we prepared Pickering emulsion composite hydrogels based on carboxymethyl chitosan - sodium alginate (CMCS-SA) nanoparticles (NPs) stabilized Pickering emulsions, poloxamer 407 (PLX), and curcumin (CUR). CMCS-SA NPs were prepared and used to stabilize Pickering emulsion. The stability of Pickering emulsion improved with the increase of the concentration of NPs, and was highly sensitive to ionic strength change. This Pickering emulsion remained stable at various temperatures. After curcumin were introduced into the emulsion, 0.6% CMCS-SA NPs Pickering emulsion showed controlled release of curcumin in vitro. The CMCS-SA-PLX-CUR hydrogels also exhibited smooth surface and dense structure. This composite hydrogels has antibacterial properties against Escherichia coli and Staphylococcus aureus. Moreover, the CMCS-SA-PLX-CUR hydrogels improved wound healing and increased expression of Ki67 and CD31. RT-qPCR results indicated that the mRNA levels of α-SMA and TGF-β1 in the CMCS-SA-PLX-CUR group were downregulated, while the mRNA levels of TGF-β3 increased. The present study suggests that the potentials of CMCS-SA-PLX-CUR hydrogels are promising in protecting bioactive components and wound care management.

Localized delivery of curcumin by thermosensitive hydrogels for promoting wound healing

BACKGROUND

Curcumin can promote wound healing, but its drug delivery medium needs to be improved further.

OBJECTIVES

A curcumin-loaded thermosensitive hydrogel was prepared, its characterization was evaluated, and its promoting effect on wound healing was observed.

METHODS

Curcumin-loaded thermosensitive hydrogels were prepared with different percentages of poloxamer 188 and poloxamer 407. A small tube inversion assay was used to observe the sol-gel transition temperature, and a rotational rheometer was used to detect the sol viscosity, sol-gel phase transition temperature and phase transition time. The microstructure of the gel was observed by scanning electron microscopy, and Fourier infrared spectroscopy was used to evaluate whether curcumin was successfully loaded. Finally, its promoting effect on wound healing was observed in vivo and in vitro.

RESULTS

Poloxamer 407 24% and poloxamer 188 1% were selected to prepare curcumin-loaded thermosensitive hydrogels. After 60 ± 15 s at 32 °C, the sol-gel transition process was completed, with certain elastic behavior and solid-like rheological properties. Scanning electron microscopy showed that the pores of the curcumin-P407/P188 thermosensitive hydrogel were interconnected, with an average pore size ranging from 5 to 10 μm. Hydrogels showed a higher swelling ratio. Fourier transform infrared spectroscopy showed that curcumin had been incorporated into the hydrogel. Live/dead cell assays suggested that the hydrogel was not toxic to fibroblasts. Curcumin-loaded thermosensitive hydrogels can promote an increase in S-phase fibroblasts and improve wound healing.

CONCLUSIONS

Curcumin-loaded P407/P188 thermosensitive hydrogel improves wound healing. More in-depth research is needed in the future.

Progress in the Development of Graphene-Based Biomaterials for Tissue Engineering and Regeneration

Over the last few decades, tissue engineering has become an important technology for repairing and rebuilding damaged tissues and organs. The scaffold plays an important role and has become a hot pot in the field of tissue engineering. It has sufficient mechanical and biochemical properties and simulates the structure and function of natural tissue to promote the growth of cells inward. Therefore, graphene-based nanomaterials (GBNs), such as graphene and graphene oxide (GO), have attracted wide attention in the field of biomedical tissue engineering because of their unique structure, large specific surface area, good photo-thermal effect, pH response and broad-spectrum antibacterial properties. In this review, the structure and properties of typical GBNs are summarized, the progress made in the development of GBNs in soft tissue engineering (including skin, muscle, nerve and blood vessel) are highlighted, the challenges and prospects of the application of GBNs in soft tissue engineering have prospected.

Self-healing polysaccharide-based injectable hydrogels with antibacterial activity for wound healing

Because the wound is difficult to heal, repeated bacterial infection will lead to complex clinical problems. Therefore, it is necessary to find an effective method to strengthen the healing process and resist bacterial infection. Hydrogels have many advantages, such as injectability and self-healing under physiological conditions, so they have been widely studied in recent years. Hydrogels can keep the wound moist and promote the wound healing. In addition, the growth of bacteria can be obviously inhibited by hydrogels themself or by doping some antibacterial active substances. Based on this, herein, this review highlighted the preparation and properties of different polysaccharide-based injectable hydrogels, and discuss their biological applications in antibacterial therapy for wound healing in recent years.

The Antimicrobial Peptide Human β-Defensin-3 Accelerates Wound Healing by Promoting Angiogenesis, Cell Migration, and Proliferation Through the FGFR/JAK2/STAT3 Signaling Pathway

In addition to its antimicrobial activity, the skin-derived antimicrobial peptide human β-defensin-3 (hBD-3) promotes keratinocyte proliferation and migration to initiate the wound healing process; however, its effects on fibroblasts, which are the major cell type responsible for wound healing, remain unclear. We investigated the role of hBD-3 in cell migration, proliferation and production of angiogenic growth factors in human fibroblasts and evaluated the in vivo effect of hBD-3 on promoting wound healing and angiogenesis. Following hBD-3 treatment, the mouse wounds healed faster and showed accumulation of neutrophils and macrophages in the early phase of wound healing and reduction of these phagocytes 4 days later. hBD-3-treated wounds also displayed an increased number of fibroblasts and newly formed vessels compared to those of the control mice. Furthermore, the expression of various angiogenic growth factors was increased in the hBD-3-treated wounds. Additionally, in vitro studies demonstrated that hBD-3 enhanced the secretion of angiogenic growth factors such as fibroblast growth factor, platelet-derived growth factor and vascular endothelial growth factor and induced the migration and proliferation of human fibroblasts. The hBD-3-mediated activation of fibroblasts involves the fibroblast growth factor receptor 1 (FGFR1)/Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathways, as evidenced by the inhibitory effects of pathway-specific inhibitors. We indeed confirmed that hBD-3 enhanced the phosphorylation of FGFR1, JAK2 and STAT3. Collectively, the current study provides novel evidence that hBD-3 might be a potential candidate for the treatment of wounds through its ability to promote wound healing, angiogenesis and fibroblast activation.

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.

A multifunctional substance P-conjugated chitosan hydrochloride hydrogel accelerates full-thickness wound healing by enhancing synchronized vascularization, extracellular matrix deposition, and nerve regeneration

Due to the native skin limitations and the complexity of reconstructive microsurgery, advanced biomaterials are urgently required to promote wound healing for severe skin defects caused by accidents and disasters. Accumulating evidence has supported that substance P (SP) has a potential effect on skin regeneration. However, SP application is seriously impeded by its poor stability and oxidative reactions occurring during production, transportation, and storage. An SP-conjugated chitosan hydrochloride hydrogel (CSCl-SP) fabricated in this study demonstrated an enhanced capacity to repair full-thickness skin defects. CSCl-SP provided a stable in vitro delivery system for SP. The dissolution of CSCl-SP promoted the proliferation, migration, and tube formation, as well as angiogenesis-related gene and protein expression in human umbilical vein endothelial cells. CSCI-SP also stimulated the proliferation, migration, and production of anabolic growth factor in human fibroblasts. Moreover, CSCl-SP significantly promoted the neurite outgrowth in Neuro-2A cells. In vivo, CSCl-SP dramatically strengthened the vascularization, extracellular matrix deposition and remodeling, and nerve regeneration, thereby promoting efficient recovery of the full-thickness skin defect. Thus, synchronized multifunction of the CSCl-SP hydrogel makes it a promising and smart material for intractable skin defects.

Topical Gynura procumbens as a Novel Therapeutic Improves Wound Healing in Diabetic Mice

Nonhealing wounds are major socioeconomic challenges to healthcare systems worldwide. Therefore, there is a substantially unmet need to develop new drugs for wound healing. Gynura procumbens, a herb found in Southeast Asia, may be an effective therapeutic for nonhealing diabetic wounds. The aim of this study was to evaluate the efficacy of G. procumbens on wound healing in the diabetic milieu. G. procumbens extract was obtained using 95% ethanol and its components were determined by thin layer chromatography. Diabetes was induced in mice using streptozotocin. We found that G. procumbens extract contained stigmasterol, kaempferol and quercetin compounds. Topical application of G. procumbens on the wounded skin of diabetic mice accelerated wound healing and induced the expression of angiogenin, epidermal growth factor, fibroblast growth factor, transforming growth factor and vascular endothelial growth factor. Furthermore, G. procumbens promoted in vitro wound healing and enhanced the migration and/or proliferation of human endothelial cells, fibroblasts, keratinocytes and mast cells cultured in diabetic conditions. Finally, G. procumbens promoted vascular formation in the diabetic mice. To the best of our knowledge, this is the first study that evaluates in vivo wound healing activities of G. procumbens and activation of cells involved in wound healing process in diabetic conditions. The findings that G. procumbens accelerates wound healing and activates cells involved in the wound healing process suggest that G. procumbens might be an effective alternative therapeutic option for nonhealing diabetic wounds.

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.

β-Cyclodextrin/Triclosan Complex-Grafted Methacrylated Glycol Chitosan Hydorgel by Photocrosslinking via Visible Light Irradiation for a Tissue Bio-Adhesive

Accelerating wound healing with minimized bacterial infection has become a topic of interest in the development of the new generation of tissue bio-adhesives. In this study, we fabricated a hydrogel system (MGC-g-CD-ic-TCS) consisting of triclosan (TCS)-complexed beta-cyclodextrin (β-CD)-conjugated methacrylated glycol chitosan (MGC) as an antibacterial tissue adhesive. Proton nuclear magnetic resonance (1H NMR) and differential scanning calorimetry (DSC) results showed the inclusion complex formation between MGC-g-CD and TCS. The increase of storage modulus (G') of MGC-g-CD-ic-TCS after visible light irradiation for 200 s indicated its hydrogelation. The swollen hydrogel in aqueous solution resulted in two release behaviors of an initial burst and sustained release. Importantly, in vitro and in vivo results indicated that MGC-g-CD-ic-TCS inhibited bacterial infection and improved wound healing, suggesting its high potential application as an antibacterial tissue bio-adhesive.

Nanosystems for the Encapsulation of Natural Products: The Case of Chitosan Biopolymer as a Matrix

Chitosan is a cationic natural polysaccharide, which has emerged as an increasingly interesting biomaterialover the past few years. It constitutes a novel perspective in drug delivery systems and nanocarriers' formulations due to its beneficial properties, including biocompatibility, biodegradability and low toxicity. The potentiality of chemical or enzymatic modifications of the biopolymer, as well as its complementary use with other polymers, further attract the scientific community, offering improved and combined properties in the final materials. As a result, chitosan has been extensively used as a matrix for the encapsulation of several valuable compounds. In this review article, the advantageous character of chitosan as a matrix for nanosystemsis presented, focusing on the encapsulation of natural products. A five-year literature review is attempted covering the use of chitosan and modified chitosan as matrices and coatings for the encapsulation of natural extracts, essential oils or pure naturally occurring bioactive compounds are discussed.

Innovation inspired by nature: Biocompatible self-healing injectable hydrogels based on modified-β-chitin for wound healing

Remarkable properties of hydrogels are compromised by failure to recover from damage, bringing their intended functions to an end. To address this, hydrogels can be functionalized with self-healing property to enable them to restore themselves after damage, thus, extending their lifetime. Herein, hydrogels were prepared by cross-linking acrylamide-modified β-chitin (Am-β-Chn) with alginate dialdehyde (ADA) to form Schiff base, showing IR characteristic peak at 1650 cm^-1, attributed to the stretching vibration of CN. The dynamic Schiff base and H-bond rendered the double crosslinked hydrogels self-healing as demonstrated by continuous step strain rheology. Characterization of the hydrogels revealed excellent biocompatibility, biodegradability, injectability and self-healing properties. Furthermore, the wound healing property of the hydrogels was investigated in vivo using zebrafish as a model system. Indirect application of Am-β-Chn/ADA hydrogel remarkably led to ~87% wound healing as compared to control which gave ~50%, suggesting that hydrogels are effective in accelerating wound healing. However, a clear understanding of the exact mechanism of its wound healing property remains to be investigated. To the best of our knowledge, this is the first innovation of developing novel double crosslinked Am-β-Chn/ADA hydrogels with both self-healing and accelerated wound healing properties, directly from marine-food wastes.

Quercetin loaded chitosan tripolyphosphate nanoparticles accelerated cutaneous wound healing in Wistar rats

Previous studies have shown that quercetin on topical application improved cutaneous wound healing in rats, but hydrophobic nature and less skin penetration limits its potential as topical healing agent. Therefore, present study was planned to investigate wound healing potential of chitosan based quercetin nanoparticles. Quercetin loaded nanoparticles were synthesized by ionic gelation method and characterized by various standard techniques. A 2 × 2 cm² square shaped wound was created on the thoraco-lumbar part of rats. Wounded rats were divided into 6 groups namely, gel (20%), blank nanoparticle (0.16%), bulk quercetin (0.3%), quercetin nanoparticles (0.03%), quercetin nanoparticles (0.1%) and quercetin nanoparticles (0.3%) treated groups. Different formulations of quercetin nanoparticles were applied on the wounds for the duration of study and healing tissues were collected on 7th, 14th and 21st day to study various parameters. Quercetin loaded nanoparticles were 361.16 ± 9.72 nm size and spherical in shape. We observed quercetin nanoparticles (0.03%) treatment caused marked reduction in the tumor necrosis factor-alpha, whereas expressions of interleukin 10, vascular endothelial growth factor and transforming growth factor beta1 was increased significantly with treatment. The granulation tissue of quercetin nanoparticles (0.03%) treated group showed better quality healing and maturity as supported by the increased blood vessels density, decreased inflammatory cells, increased number of myofibroblasts, deposition and arrangement of collagen fibers and re-epithelialization. In conclusion, quercetin nanoparticles (0.03%) treatment significantly improved wound healing by modulation of cytokines and growth factors involved in inflammatory and proliferative phases of wound healing.

Design, characterization, and evaluation of antibacterial gels, Boc-D-Phe-γ4-L-Phe-PEA/chitosan and Boc-L-Phe-γ4-L-Phe-PEA/chitosan, for biomaterial-related infections

Self-assembled peptide gels have generated interest as antibacterial materials to prevent biomaterial-related infections but these peptides are often associated with poor proteolytic stability. Efforts have been made to stabilize peptides by incorporating non-natural amino acids and/or linkages but complexation with polymers have not been explored. Therefore, we developed self-assembled peptide/chitosan gels, Boc-D-Phe-γ⁴-L-Phe-PEA (NH007)/chitosan and Boc-L-Phe-γ⁴-L-Phe-PEA (NH009)/chitosan, by complexing dipeptide NH007 or NH009 with chitosan in DMSO:acetic acid. The gels were characterized using SEM, FTIR, contact angle, and rheology data and found to exhibit excellent viscoelastic and self-healing characteristics. Complexation with chitosan led to an increase in stability against proteolytic degradation. Peptide/chitosan gels showed broad spectrum antibacterial activities against Gram-negative and Gram-positive bacteria, such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis at a high inoculum of 10⁷-10⁸ cfu/mL. NH007/chitosan gels showed 70-75% inhibition, whereas NH009/chitosan showed 78-81% inhibition and NH009/chitosan gels, in particular, showed strong antibacterial activity against pathogenic strain of P. aeruginosa. A unique feature of these gels is that the antibacterial activities did not decrease gradually but were sustained for up to 48 h. The mechanistic studies using SEM and HR-TEM indicated interaction of gels with bacterial membrane components, leading to cell lysis. The MTT and LDH assays indicated >90% cell viability and only 8-10% toxicity towards NIH 3T3 fibroblast cells. Thus, peptide/chitosan gels developed in the present work showed improved proteolytic stability and sustained antibacterial activities and, therefore, may be used for preventing biomaterial-related infections.

Chitosans for Tissue Repair and Organ Three-Dimensional (3D) Bioprinting

Chitosan is a unique natural resourced polysaccharide derived from chitin with special biocompatibility, biodegradability, and antimicrobial activity. During the past three decades, chitosan has gradually become an excellent candidate for various biomedical applications with prominent characteristics. Chitosan molecules can be chemically modified, adapting to all kinds of cells in the body, and endowed with specific biochemical and physiological functions. In this review, the intrinsic/extrinsic properties of chitosan molecules in skin, bone, cartilage, liver tissue repair, and organ three-dimensional (3D) bioprinting have been outlined. Several successful models for large scale-up vascularized and innervated organ 3D bioprinting have been demonstrated. Challenges and perspectives in future complex organ 3D bioprinting areas have been analyzed.

Peptide-Conjugated Nanoparticles as Targeted Anti-angiogenesis Therapeutic and Diagnostic in Cancer

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Targeting angiogenesis in the microenvironment of a tumor can enable suppression of tumor angiogenesis and delivery of anticancer drugs into the tumor. Anti-angiogenesis targeted delivery systems utilizing passive targeting such as Enhanced Permeability and Retention (EPR) and specific receptor-mediated targeting (active targeting) should result in tumor-specific targeting. One targeted anti-angiogenesis approach uses peptides conjugated to nanoparticles, which can be loaded with anticancer agents. Anti-angiogenesis agents can suppress tumor angiogenesis and thereby affect tumor growth progression (tumor growth arrest), which may be further reduced with the targetdelivered anticancer agent. This review provides an update of tumor vascular targeting for therapeutic and diagnostic applications, with conventional or long-circulating nanoparticles decorated with peptides that target neovascularization (anti-angiogenesis) in the tumor microenvironment.

Functional Hydrogels and Their Application in Drug Delivery, Biosensors, and Tissue Engineering

Hydrogel is a new class of functional polymer materials with a promising potential in the biomedical field. The purpose of this article is to review recent advancements in several types of biomedical hydrogels, including conductive hydrogels, injectable hydrogels, double network hydrogels, responsive hydrogels, nanocomposite hydrogels, and sliding hydrogels. In comparison with traditional hydrogels, these advanced hydrogels exhibit significant advantages in structure, mechanical properties, and applications. The article focuses on different methods used to prepare advanced biomedical hydrogels and their diversified applications as drug delivery systems, wound dressings, biosensors, contact lenses, and tissue replacement. These advances are rapidly overcoming current limitations of hydrogels, and we anticipate that further research will lead to the development of advanced hydrogels with ubiquitous roles in biomedicine and tissue replacement and regeneration.

Progress in the Development of Chitosan-Based Biomaterials for Tissue Engineering and Regenerative Medicine

Over the last few decades, chitosan has become a good candidate for tissue engineering applications. Derived from chitin, chitosan is a unique natural polysaccharide with outstanding properties in line with excellent biodegradability, biocompatibility, and antimicrobial activity. Due to the presence of free amine groups in its backbone chain, chitosan could be further chemically modified to possess additional functional properties useful for the development of different biomaterials in regenerative medicine. In the current review, we will highlight the progress made in the development of chitosan-containing bioscaffolds, such as gels, sponges, films, and fibers, and their possible applications in tissue repair and regeneration, as well as the use of chitosan as a component for drug delivery applications.

Anti-miR-200b promotes wound healing by regulating fibroblast functions in a novel mouse model

MicroRNA-200b (miR-200b) down-regulation has been found in wound-healing tissues. Fibroblasts are the predominant cells that orchestrate the production of collagen in wound healing. However, it is still unclear whether miR-200b can affect the wound healing by regulating the fibroblasts' function. The current rodent wound-healing models are not ideal due to their marked difference in structure compared with the human skin. In this study, we demonstrated that the murine plantar skin had similar anatomical features to the human skin. Using this model, the gain/loss-of-function studies showed that miR-200b caused a significantly delayed wound healing in vivo. Furthermore, using cell proliferation, migration and collagen synthesis assays, we found that miR-200b attenuated cell proliferation, migration and collagen synthesis of fibroblasts, which are critical aspects of wound healing. miR-200b also decreased the expression of Zeb1. Collectively, we established a new murine plantar skin model for the investigation of wound healing, and based on it we found that miR-200b affected the wound healing by regulating the biological function of fibroblasts, which provided a new insight for wound healing.

Engineered delivery strategies for enhanced control of growth factor activities in wound healing

Growth factors (GFs) are versatile signalling molecules that orchestrate the dynamic, multi-stage process of wound healing. Delivery of exogenous GFs to the wound milieu to mediate healing in an active, physiologically-relevant manner has shown great promise in laboratories; however, the inherent instability of GFs, accompanied with numerous safety, efficacy and cost concerns, has hindered the clinical success of GF delivery. In this article, we highlight that the key to overcoming these challenges is to enhance the control of the activities of GFs throughout the delivering process. We summarise the recent strategies based on biomaterials matrices and molecular engineering, which aim to improve the conditions of GFs for delivery (at the 'supply' end of the delivery), increase the stability and functions of GFs in extracellular matrix (in transportation to target cells), as well as enhance the GFs/receptor interaction on the cell membrane (at the 'destination' end of the delivery). Many of these investigations have led to encouraging outcomes in various in vitro and in vivo regenerative models with considerable translational potential.

Peptide SIKVAV-modified chitosan hydrogels promote skin wound healing by accelerating angiogenesis and regulating cytokine secretion

Skin wound healing is complex and involves the processes of many factors, among which angiogenesis and inflammatory responses play important roles. New blood vessels provide nutrition and oxygen for skin wound repair. Cytokines in skin wounds, which include pro-inflammatory and anti-inflammatory factors, can modulate the inflammatory response. Therefore, treatment strategies that promote angiogenesis and modulate the inflammatory response in skin wounds can accelerate skin wound healing. This study explored the effects of peptide Ser-Ile-Lys-Val-Ala-Val (SIKVAV)-modified chitosan hydrogels in skin wound healing. General observation demonstrated that SIKVAV-modified chitosan hydrogels promoted the contraction of skin wounds compared with the negative and positive controls. Masson's trichrome staining indicated that peptide-modified chitosan hydrogels accelerated the deposition of more collagen fibers in the skin wounds compared with the negative and positive controls. Immunohistochemistry assays showed that more myofibroblasts were deposited and more angiogenesis was found in skin wounds treated with peptide-modified chitosan hydrogels compared with the negative and positive controls. In addition, qRT-PCR assays showed that peptide-modified chitosan hydrogels promoted the expression of TGF-β1 (transforming growth factor-β1) mRNA and inhibited the expression of TNF-α (tumor necrosis factor-α) mRNA and IL-1β (Interleukin-1β) mRNA and IL-6 (Interleukin-6) mRNA in skin wounds. Taken together, these results indicate the potential of SIKVAV-modified chitosan hydrogels in skin wound healing as complex biomaterials.

Multifunctional smart hydrogels: potential in tissue engineering and cancer therapy

In recent years, clinical applications have been proposed for various hydrogel products. Hydrogels can be derived from animal tissues, plant extracts and/or adipose tissue extracellular matrices; each type of hydrogel presents significantly different functional properties and may be used for many different applications, including medical therapies, environmental pollution treatments, and industrial materials. Due to complicated preparation techniques and the complexities associated with the selection of suitable materials, the applications of many host-guest supramolecular polymeric hydrogels are limited. Thus, improvements in the design and construction of smart materials are highly desirable in order to increase the lifetimes of functional materials. Here, we summarize different functional hydrogels and their varied preparation methods and source materials. The multifunctional properties of hydrogels, particularly their unique ability to adapt to certain environmental stimuli, are chiefly based on the incorporation of smart materials. Smart materials may be temperature sensitive, pH sensitive, pH/temperature dual sensitive, photoresponsive or salt responsive and may be used for hydrogel wound repair, hydrogel bone repair, hydrogel drug delivery, cancer therapy, and so on. This review focuses on the recent development of smart hydrogels for tissue engineering applications and describes some of the latest advances in using smart materials to create hydrogels for cancer therapy.

Electrofabrication of functional materials: Chloramine-based antimicrobial film for infectious wound treatment

Electrical signals can be imposed with exquisite spatiotemporal control and provide exciting opportunities to create structure and confer function. Here, we report the use of electrical signals to program the fabrication of a chloramine wound dressing with high antimicrobial activity. This method involves two electrofabrication steps: (i) a cathodic electrodeposition of an aminopolysaccharide chitosan triggered by a localized region of high pH; and (ii) an anodic chlorination of the deposited film in the presence of chloride. This electrofabrication process is completed within several minutes and the chlorinated chitosan can be peeled from the electrode to yield a free-standing film. The presence of active NCl species in this electrofabricated film was confirmed with chlorination occurring first on the amine groups and then on the amide groups when large anodic charges were used. Electrofabrication is quantitatively controllable as the cathodic input controls film growth during deposition and the anodic input controls film chlorination. In vitro studies demonstrate that the chlorinated chitosan film has antimicrobial activities that depend on the chlorination degree. In vivo studies with a MRSA infected wound healing model indicate that the chlorinated chitosan film inhibited bacterial growth, induced less inflammation, developed reorganized epithelial and dermis structures, and thus promoted wound healing compared to a bare wound or wound treated with unmodified chitosan. These results demonstrate the fabrication of advanced functional materials (i.e., antimicrobial wound dressings) using controllable electrical signals to both organize structure through non-covalent interactions (i.e., induce chitosan's reversible self-assembly) and to initiate function-conferring covalent modifications (i.e., generate chloramine bonds). Potentially, electrofabrication may provide a simple, low cost and sustainable alternative for materials fabrication.

STATEMENT OF SIGNIFICANCE

We believe this work is novel because this is the first report (to our knowledge) that electronic signals enable the fabrication of advanced antimicrobial dressings with controlled structure and biological performance. We believe this work is significant because electrofabrication enables rapid, controllable and sustainable materials construction with reduced adverse environmental impacts while generating high performance materials for healthcare applications. More specifically, we report an electrofbrication of antimicrobial film that can promote wound healing.

Advances in Carbon Nanotubes-Hydrogel Hybrids in Nanomedicine for Therapeutics

In spite of significant advancement in hydrogel technology, low mechanical strength and lack of electrical conductivity have limited their next-level biomedical applications for skeletal muscles, cardiac and neural cells. Host-guest chemistry based hybrid nanocomposites systems have gained attention as they completely overcome these pitfalls and generate bioscaffolds with tunable electrical and mechanical characteristics. In recent years, carbon nanotube (CNT)-based hybrid hydrogels have emerged as innovative candidates with diverse applications in regenerative medicines, tissue engineering, drug delivery devices, implantable devices, biosensing, and biorobotics. This article is an attempt to recapitulate the advancement in synthesis and characterization of hybrid hydrogels and provide deep insights toward their functioning and success as biomedical devices. The improved comparative performance and biocompatibility of CNT-hydrogels hybrids systems developed for targeted biomedical applications are addressed here. Recent updates toward diverse applications and limitations of CNT hybrid hydrogels is the strength of the review. This will provide a holistic approach toward understanding of CNT-based hydrogels and their applications in nanotheranostics.