Biocomposite nanofiber matrices to support ECM remodeling by human dermal progenitors and enhanced wound closure

Stem Cells and Nanofibers for Skin Regeneration and Wound Healing

Stem cells have been attractive targets for tissue regeneration due to their inherent ability to differentiate into various specialized cell types; however, efforts for stem cell transplantation for the treatment of degenerated tissues have been hampered by the propensity of some stem cell types to form teratomas and the lessened viability of stem cells after transplantation. These disadvantages can be prevented using tailored extracellular matrix-like materials that can be used as an aid for the transplantation of stem cells. Nanomaterials, in particular nanofibers, have great potential to be used as extracellular matrix-like materials for this purpose. In this article, we will review the use of stem cells and nanofibers for skin regeneration and wound healing.

Resveratrol-Ampicillin Dual-Drug Loaded Polyvinylpyrrolidone/Polyvinyl Alcohol Biomimic Electrospun Nanofiber Enriched with Collagen for Efficient Burn Wound Repair

Background

The healing of burn wounds is a complicated physiological process that involves several stages, including haemostasis, inflammation, proliferation, and remodelling to rebuild the skin and subcutaneous tissue integrity. Recent advancements in nanomaterials, especially nanofibers, have opened a new way for efficient healing of wounds due to burning or other injuries.

Methods

This study aims to develop and characterize collagen-decorated, bilayered electrospun nanofibrous mats composed of PVP and PVA loaded with Resveratrol (RSV) and Ampicillin (AMP) to accelerate burn wound healing and tissue repair.

Results

Nanofibers with smooth surfaces and web-like structures with diameters ranging from 200 to 400 nm were successfully produced by electrospinning. These fibres exhibited excellent in vitro properties, including the ability to absorb wound exudates and undergo biodegradation over a two-week period. Additionally, these nanofibers demonstrated sustained and controlled release of encapsulated Resveratrol (RSV) and Ampicillin (AMP) through in vitro release studies. The zone of inhibition (ZOI) of PVP-PVA-RSV-AMP nanofibers against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was found 31±0.09 mm and 12±0.03, respectively, which was significantly higher as compared to positive control. Similarly, the biofilm study confirmed the significant reduction in the formation of biofilms in nanofiber-treated group against both S. aureus and E. coli. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis proved the encapsulation of RSV and AMP successfully into nanofibers and their compatibility. Haemolysis assay (%) showed no significant haemolysis (less than 5%) in nanofiber-treated groups, confirmed their cytocompatibility with red blood cells (RBCs). Cell viability assay and cell adhesion on HaCaT cells showed increased cell proliferation, indicating its biocompatibility as well as non-toxic properties. Results of the in-vivo experiments on a burn wound model demonstrated potential burn wound healing in rats confirmed by H&E-stained images and also improved the collagen synthesis in nanofibers-treated groups evidenced by Masson-trichrome staining. The ELISA assay clearly indicated the efficient downregulation of TNF-alpha and IL-6 inflammatory biomarkers after treatment with nanofibers on day 10.

Conclusion

The RSV and AMP-loaded nanofiber mats, developed in this study, expedite burn wound healing through their multifaceted approach.

Integration of polysaccharide electrospun nanofibers with microneedle arrays promotes wound regeneration: A review

Utilizing electrospun nanofibers and microneedle arrays in wound regeneration has been practiced for several years. Researchers have recently asserted that using multiple methods concurrently might enhance efficiency, despite the inherent strengths and weaknesses of each individual approach. The combination of microneedle arrays with electrospun nanofibers has the potential to create a drug delivery system and wound healing method that offer improved efficiency and accuracy in targeting. The use of microneedles with nanofibers allows for precise administration of pharmaceuticals due to the microneedles' capacity to pierce the skin and the nanofibers' role as a drug reservoir, resulting in a progressive release of drugs over a certain period of time. Electrospun nanofibers have the ability to imitate the extracellular matrix and provide a framework for cellular growth and tissue rejuvenation, while microneedle arrays show potential for enhancing tissue regeneration and enhancing the efficacy of wound healing. The integration of electrospun nanofibers with microneedle arrays may be customized to effectively tackle particular obstacles in the fields of wound healing and drug delivery. However, some issues must be addressed before this paradigm may be fully integrated into clinical settings, including but not limited to ensuring the safety and sterilization of these products for transdermal use, optimizing manufacturing methods and characterization of developed products, larger-scale production, optimizing storage conditions, and evaluating the inclusion of multiple therapeutic and antimicrobial agents to increase the synergistic effects in the wound healing process. This research examines the combination of microneedle arrays with electrospun nanofibers to enhance the delivery of drugs and promote wound healing. It explores various kinds of microneedle arrays, the materials and processes used, and current developments in their integration with electrospun nanofibers.

Geometric constraint-triggered collagen expression mediates bacterial-host adhesion

Cells living in geometrically confined microenvironments are ubiquitous in various physiological processes, e.g., wound closure. However, it remains unclear whether and how spatially geometric constraints on host cells regulate bacteria-host interactions. Here, we reveal that interactions between bacteria and spatially constrained cell monolayers exhibit strong spatial heterogeneity, and that bacteria tend to adhere to these cells near the outer edges of confined monolayers. The bacterial adhesion force near the edges of the micropatterned monolayers is up to 75 nN, which is ~3 times higher than that at the centers, depending on the underlying substrate rigidities. Single-cell RNA sequencing experiments indicate that spatially heterogeneous expression of collagen IV with significant edge effects is responsible for the location-dependent bacterial adhesion. Finally, we show that collagen IV inhibitors can potentially be utilized as adjuvants to reduce bacterial adhesion and thus markedly enhance the efficacy of antibiotics, as demonstrated in animal experiments.

Spray nebulization enables polycaprolactone nanofiber production in a manner suitable for generation of scaffolds or direct deposition of nanofibers onto cells

Spray nebulization is an elegant, but relatively unstudied, technique for scaffold production. Herein we fabricated mesh scaffolds of polycaprolactone (PCL) nanofibers via spray nebulization of 8% PCL in dichloromethane (DCM) using a 55.2 kPa compressed air stream and 17 ml h-1polymer solution flow rate. Using a refined protocol, we tested the hypothesis that spray nebulization would simultaneously generate nanofibers and eliminate solvent, yielding a benign environment at the point of fiber deposition that enabled the direct deposition of nanofibers onto cell monolayers. Nanofibers were collected onto a rotating plate 20 cm from the spray nozzle, but could be collected onto any static or moving surface. Scaffolds exhibited a mean nanofiber diameter of 910 ± 190 nm, ultimate tensile strength of 2.1 ± 0.3 MPa, elastic modulus of 3.3 ± 0.4 MPa, and failure strain of 62 ± 6%.In vitro, scaffolds supported growth of human keratinocyte cell epithelial-like layers, consistent with potential utility as a dermal scaffold. Fourier-transform infrared spectroscopy demonstrated that DCM had vaporized and was undetectable in scaffolds immediately following production. Exploiting the rapid elimination of DCM during fiber production, we demonstrated that nanofibers could be directly deposited on to cell monolayers, without compromising cell viability. This is the first description of spray nebulization generating nanofibers using PCL in DCM. Using this method, it is possible to rapidly produce nanofiber scaffolds, without need for high temperatures or voltages, yielding a method that could potentially be used to deposit nanofibers onto cell cultures or wound sites.

Chlorella sp.-ameliorated undesirable microenvironment promotes diabetic wound healing

Chronic diabetic wound remains a critical challenge suffering from the complicated negative microenvironments, such as high-glucose, excessive reactive oxygen species (ROS), hypoxia and malnutrition. Unfortunately, few strategies have been developed to ameliorate the multiple microenvironments simultaneously. In this study, Chlorella sp. (Chlorella) hydrogels were prepared against diabetic wounds. In vitro experiments demonstrated that living Chlorella could produce dissolved oxygen by photosynthesis, actively consume glucose and deplete ROS with the inherent antioxidants, during the daytime. At night, Chlorella was inactivated in situ by chlorine dioxide with human-body harmless concentration to utilize its abundant contents. It was verified in vitro that the inactivated-Chlorella could supply nutrition, relieve inflammation and terminate the oxygen-consumption of Chlorella-respiration. The advantages of living Chlorella and its contents were integrated ingeniously. The abovementioned functions were proven to accelerate cell proliferation, migration and angiogenesis in vitro. Then, streptozotocin-induced diabetic mice were employed for further validation. The in vivo outcomes confirmed that Chlorella could ameliorate the undesirable microenvironments, including hypoxia, high-glucose, excessive-ROS and chronic inflammation, thereby synergistically promoting tissue regeneration. Given the results above, Chlorella is considered as a tailor-made therapeutic strategy for diabetic wound healing.

Comparison of biopolymer scaffolds for the fabrication of skin substitutes in a porcine wound model

This study compared three acellular scaffolds as templates for the fabrication of skin substitutes. A collagen-glycosaminoglycan (C-GAG), a biodegradable polyurethane foam (PUR) and a hybrid combination (PUR/C-GAG) were investigated. Scaffolds were prepared for cell inoculation. Fibroblasts and keratinocytes were serially inoculated onto the scaffolds and co-cultured for 14 days before transplantation. Three pigs each received four full-thickness 8 cm × 8 cm surgical wounds, into which a biodegradable temporising matrix (BTM) was implanted. Surface seals were removed after integration (28 days), and three laboratory-generated skin analogues and a control split-thickness skin graft (STSG) were applied for 16 weeks. Punch biopsies confirmed engraftment and re-epithelialisation. Biophysical wound parameters were also measured and analysed. All wounds showed greater than 80% epithelialisation by day 14 post-transplantation. The control STSG displayed 44% contraction over the 16 weeks, and the test scaffolds, C-GAG 64%, Hybrid 66.7% and PUR 67.8%. Immunohistochemistry confirmed positive epidermal keratins and basement membrane components (Integrin alpha-6, collagens IV and VII). Collagen deposition and fibre organisation indicated the degree of fibrosis and scar produced for each graft. All scaffold substitutes re-epithelialised by 4 weeks. The percentage of original wound area for the Hybrid and PUR was significantly different than the STSG and C-GAG, indicating the importance of scaffold retainment within the first 3 months post-transplant. The PUR/C-GAG scaffolds reduced the polymer pore size, assisting cell retention and reducing the contraction of in vitro collagen. Further investigation is required to ensure reproducibility and scale-up feasibility.

Antifungal Activity of Camelus-Derived LFA-LFC Chimeric Peptide Gelatin Film and Effect on Oral Bacterial Biofilm

The objective of this study was to construct lactoferrin (LFA-LFC) chimeric peptide gelatin drug-loaded fiber film by tissue engineering strategy, and study its bacteriostatic effect on oral pathogens (especially Candida albicans) and its effect on biofilm. First of all, LFA-LFC chitosan nanoparticles were prepared firstly, and then fluconazole gelatin (LF/GH/F) film loaded with LFA-LFC was prepared by electrospinning. Scanning electron microscope (SEM), mechanical strength, drug release, cytotoxicity, and real-time PCR were used to test the properties of the synthesized materials. SEM showed that there was the reticular structure for fiber film before and after cross-linking. LF/GH/F film had no obvious cytotoxicity, with good biocompatibility and drug release; real-time PCR and antibacterial test showed that the LF/GH/F film had good antibacterial activity. LF/GH/F film has a good inhibitory effect on oral pathogens, and its mechanism is related to biofilm. The antibacterial experiments of nanofiber membrane in vitro and the effect of bacterial biofilm were carried out. The effect of LF/GH/F on oral microbial flora structure was studied by fluorescence quantitative pest techniques.

Sustained delivery of rhMG53 promotes diabetic wound healing and hair follicle development

MG53 is an essential component of the cell membrane repair machinery, participating in the healing of dermal wounds. Here we develop a novel delivery system using recombinant human MG53 (rhMG53) protein and a reactive oxygen species (ROS)-scavenging gel to treat diabetic wounds. Mice with ablation of MG53 display defective hair follicle structure, and topical application of rhMG53 can promote hair growth in the mg53 ^-/- mice. Cell lineage tracing studies reveal a physiological function of MG53 in modulating the proliferation of hair follicle stem cells (HFSCs). We find that rhMG53 protects HFSCs from oxidative stress-induced apoptosis and stimulates differentiation of HSFCs into keratinocytes. The cytoprotective function of MG53 is mediated by STATs and MAPK signaling in HFSCs. The thermosensitive ROS-scavenging gel encapsulated with rhMG53 allows for sustained release of rhMG53 and promotes healing of chronic cutaneous wounds and hair follicle development in the db/db mice. These findings support the potential therapeutic value of using rhMG53 in combination with ROS-scavenging gel to treat diabetic wounds.

A Nanozyme-Immobilized Hydrogel with Endogenous ROS-Scavenging and Oxygen Generation Abilities for Significantly Promoting Oxidative Diabetic Wound Healing

Non-healing wound is a common complication of diabetic patients associated with high morbidity and mortality. Engineered therapeutic hydrogels have enviable advantages in tissue regeneration, however, they are suboptimal for the healing of diabetic wounds characterized by reactive oxygen species (ROS) accumulation and chronic hypoxia. Here, a unique biological metabolism-inspired hydrogel, for ameliorating this hostile diabetic microenvironment, is presented. Consisting of natural polymers (hydrazide modified hyaluronic acid and aldehyde modified hyaluronic acid) and a metal-organic frameworks derived catalase-mimic nanozyme (ε-polylysine coated mesoporous manganese cobalt oxide), the engineered nanozyme-reinforced hydrogels can not only capture the endogenous elevated ROS in diabetic wounds, but also synergistically produce oxygen through the ROS-driven oxygen production ability. These fascinating properties of hydrogels protect skin cells (e.g., keratinocytes, fibroblasts, and vascular endothelial cells) from ROS and hypoxia-mediated death and proliferation inhibition. Diabetic wounds treated with the nanozyme-reinforced hydrogels highlight the potential of inducing the macrophages polarization from pro-inflammatory phenotype (M1) to anti-inflammatory subtype (M2). The hydrogel dressings demonstrate a prominently accelerated healing rate as shown by alleviating the excessive inflammatory, inducing efficiently proliferation, re-epithelialization, collagen deposition, and neovascularization. This work provides an effective strategy based on nanozyme-reinforced hydrogel as a ROS-driven oxygenerator for enhancing diabetic wound healing.

Smart Thermoresponsive Electrospun Nanofibers with On-Demand Release of Carbon Quantum Dots for Cellular Uptake

Developing a smart responsive surface for on-demand delivery of organic, inorganic, and biological cargo in vitro cellular uptake is always in constant demand. Herein, we present carbon quantum dot (CQD)-loaded (poly(N-isopropylacrylamide) (PNIPAAm)/poly(methyl methacrylate (PMMA)) blend nanofiber sheets having a thermoresponsive nature. As a model cargo, fluorescent CQDs are used for the demonstration of the on-demand delivery mechanism. In addition, a thermoresponsive nature is produced by the PNIPAAm polymer in the nanofiber matrix while the PMMA polymer provides extra stability and firmness to the nanofibers against the sudden dissolution of the nanofibers in aqueous media. The synthesis of CQDs and their loading into a blend nanofiber matrix are confirmed using fluorescence spectrophotometry, transmission electron microscopy, and fluorescence microscopy. The morphologies and diameters of the nanofibers are analyzed by scanning electron microscopy. Burst effect analysis proves that 30% (w/w) PNIPAAm-containing nanofibers possess the highest stability with the least dissolution in aqueous media. Thermoresponsiveness of the nanofibers is further confirmed through water contact angle measurements. Quantitative fluorescence results show that more than 80% of loaded CQDs can be released upon thermal stimulation. The fluorescence micrographs reveal that the blend nanofiber sheets can effectively improve the cellular uptake of CQDs by simply increasing the local concentrations via applying thermal stimulation as the released mechanism.

A review of current advancements for wound healing: Biomaterial applications and medical devices

Wound healing is a complex process that is critical in restoring the skin's barrier function. This process can be interrupted by numerous diseases resulting in chronic wounds that represent a major medical burden. Such wounds fail to follow the stages of healing and are often complicated by a pro‐inflammatory milieu attributed to increased proteinases, hypoxia, and bacterial accumulation. The comprehensive treatment of chronic wounds is still regarded as a significant unmet medical need due to the complex symptoms caused by the metabolic disorder of the wound microenvironment. As a result, several advanced medical devices, such as wound dressings, wearable wound monitors, negative pressure wound therapy devices, and surgical sutures, have been developed to correct the chronic wound environment and achieve skin tissue regeneration. Most medical devices encompass a wide range of products containing natural (e.g., chitosan, keratin, casein, collagen, hyaluronic acid, alginate, and silk fibroin) and synthetic (e.g., polyvinyl alcohol, polyethylene glycol, poly[lactic‐co‐glycolic acid], polycaprolactone, polylactic acid) polymers, as well as bioactive molecules (e.g., chemical drugs, silver, growth factors, stem cells, and plant compounds). This review addresses these medical devices with a focus on biomaterials and applications, aiming to deliver a critical theoretical reference for further research on chronic wound healing.

Green Polymer Nanocomposites for Skin Tissue Engineering

Fabrication of an appropriate skin scaffold needs to meet several standards related to the mechanical and biological properties. Fully natural/green scaffolds with acceptable biodegradability, biocompatibility, and physiological properties quite often suffer from poor mechanical properties. Therefore, for appropriate skin tissue engineering and to mimic the real functions, we need to use synthetic polymers and/or additives as complements to green polymers. Green nanocomposites (either nanoscale natural macromolecules or biopolymers containing nanoparticles) are a class of scaffolds with acceptable biomedical properties window (drug delivery and cardiac, nerve, bone, cartilage as well as skin tissue engineering), enabling one to achieve the required level of skin regeneration and wound healing. In this review, we have collected, summarized, screened, analyzed, and interpreted the properties of green nanocomposites used in skin tissue engineering and wound dressing. We particularly emphasize the mechanical and biological properties that skin cells need to meet when seeded on the scaffold. In this regard, the latest state of the art studies directed at fabrication of skin tissue and bionanocomposites as well as their mechanistic features are discussed, whereas some unspoken complexities and challenges for future developments are highlighted.

Nature-Derived and Synthetic Additives to poly(ɛ-Caprolactone) Nanofibrous Systems for Biomedicine; an Updated Overview

As a low cost, biocompatible, and bioresorbable synthetic polymer, poly (ɛ-caprolactone) (PCL) is widely used for different biomedical applications including drug delivery, wound dressing, and tissue engineering. An extensive range of in vitro and in vivo tests has proven the favourable applicability of PCL in biomedicine, bringing about the FDA approval for a plethora of PCL made medical or drug delivery systems. This popular polymer, widely researched since the 1970s, can be readily processed through various techniques such as 3D printing and electrospinning to create biomimetic and customized medical products. However, low mechanical strength, insufficient number of cellular recognition sites, poor bioactivity, and hydrophobicity are main shortcomings of PCL limiting its broader use for biomedical applications. To maintain and benefit from the high potential of PCL, yet addressing its physicochemical and biological challenges, blending with nature-derived (bio)polymers and incorporation of nanofillers have been extensively investigated. Here, we discuss novel additives that have been meant for enhancement of PCL nanofiber properties and thus for further extension of the PCL nanofiber application domain. The most recent researches (since 2017) have been covered and an updated overview about hybrid PCL nanofibers is presented with focus on those including nature-derived additives, e.g., polysaccharides and proteins, and synthetic additives, e.g., inorganic and carbon nanomaterials.

Aminolysis as a surface functionalization method of aliphatic polyester nonwovens: impact on material properties and biological response

Aminolysis treatment improves L929 cell–scaffold interaction. It is possible to reach compromise between the concentration of NH2 groups and mechanical properties change.

Prevention of Postsurgical Abdominal Adhesion Using Electrospun TPU Nanofibers in Rat Model

Intra-abdominal adhesions following surgery are a challenging problem in surgical practice. This study fabricated different thermoplastic polyurethane (TPU) nanofibers with different average diameters using the electrospinning method. The conditions were evaluated by scanning electron microscopy (SEM), atomic force microscope (AFM), and Fourier transform infrared spectrometer (FTIR) analysis. A static tensile test was applied using a strength testing device to assess the mechanical properties of the electrospun scaffolds. By changing the effective electrospinning parameters, the best quality of nanofibers could be achieved with the lowest bead numbers. The electrospun nanofibers were evaluated in vivo using a rat cecal abrasion model. The macroscopic evaluation and the microscopic study, including the degree of adhesion and inflammation, were investigated after three and five weeks. The resultant electrospun TPU nanofibers had diameters ranging from about 200 to 1000 nm. The diameters and morphology of the nanofibers were significantly affected by the concentration of polymer. Uniform TPU nanofibers without beads could be prepared by electrospinning through reasonable control of the process concentration. These nanofibers' biodegradability and antibacterial properties were investigated by weight loss measurement and microdilution methods, respectively. The purpose of this study was to provide electrospun nanofibers having biodegradability and antibacterial properties that prevent any adhesions or inflammation after pelvic and abdominal surgeries. The in vivo experiments revealed that electrospun TPU nanofibers reduced the degree of abdominal adhesions. The histopathological study confirmed only a small extent of inflammatory cell infiltration in the 8% and 10% TPU. Conclusively, nanofibers containing 8% TPU significantly decreased the incidence and severity of postsurgical adhesions, and it is expected to be used in clinical applications in the future.

Fibrous Polymer-Based Composites Obtained by Electrospinning for Bone Tissue Engineering

Currently, the significantly developing fields of tissue engineering related to the fabrication of polymer-based materials that possess microenvironments suitable to provide cell attachment and promote cell differentiation and proliferation involve various materials and approaches. Biomimicking approach in tissue engineering is aimed at the development of a highly biocompatible and bioactive material that would most accurately imitate the structural features of the native extracellular matrix consisting of specially arranged fibrous constructions. For this reason, the present research is devoted to the discussion of promising fibrous materials for bone tissue regeneration obtained by electrospinning techniques. In this brief review, we focus on the recently presented natural and synthetic polymers, as well as their combinations with each other and with bioactive inorganic incorporations in order to form composite electrospun scaffolds. The application of several electrospinning techniques in relation to a number of polymers is touched upon. Additionally, the efficiency of nanofibrous composite materials intended for use in bone tissue engineering is discussed based on biological activity and physiochemical characteristics.

Mesoporous silica incorporated PCL/Curcumin nanofiber for wound healing application

Electrospinning, a recent fast-emerging technique highly applicable in the production of nanofibers has gained vast recognition owing to its explicit applications in various domains. Amongst which, the production of nanoscaffolds for wound healing applications has been focused recently due to advantages over conventional wound healing methods. In the present research, a composite nanoscaffold comprising SBA-15 (Santa Barbara Amorphous), amine functionalized SBA-15 polycaprolactone (PCL) and curcumin was investigated for its potentiality in wound healing therapeutics. The high biocompatibility and cell adhesion of amine functionalized SBA-15 and the widely explored antimicrobial properties of curcumin added benefit for the wound healing target. The prepared highly interconnected electrospun fibers with porous structure were characterized through various studies such as FTIR, XRD, SEM and EDAX. Further, antibacterial studies against both Gram positive (Bacillus subtilis) and Gram negative (Escherichia coli) strains revealed an improved zone of inhibition. Major invitro studies such as cell migration, proliferation, bio-compatibility was experimented through cell adhesion and live and dead assay using Swiss 3T6 cell lines. In vivo studies on female Wister rats using the fabricated nanofibers incorporated with curcumin and amine functionalized SBA-15 showed 99% scar-less wound healing within 21 days. Re-epithelization of tissue, collagen deposition and formation of granulation tissue were observed from the results of Hematoxylin-Eosin and Masson's tri-chrome staining. From the observations, it can be concluded that the fabricated nanoscaffold could be an effective substrate for wound healing therapeutics.

Biotechnological Applications of Polymeric Nanofiber Platforms Loaded with Diverse Bioactive Materials

This review article highlights the critical research and formative works relating to nanofiber composites loaded with bioactive materials for diverse applications, and discusses the recent research on the use of electrospun nanofiber incorporating bioactive compounds such as essential oils, herbal bioactive components, plant extracts, and metallic nanoparticles. Inevitably, with the common advantages of bioactive components and polymer nanofibers, electrospun nanofibers containing bioactive components have attracted intense interests for their applications in biomedicine and cancer treatment. Many studies have only concentrated on the production and performance of electrospun nanofiber loaded with bioactive components; in this regard, the features of different types of electrospun nanofiber incorporating a wide variety of bioactive compounds and their developing trends are summarized and assessed in the present article, as is the feasible use of nanofiber technology to produce products on an industrial scale in different applications.

A designer cell culture insert with a nanofibrous membrane toward engineering an epithelial tissue model validated by cellular nanomechanics

Engineered platforms for culturing cells of the skin and other epithelial tissues are useful for the regeneration and development of in vitro tissue models used in drug screening. Recapitulating the biomechanical behavior of the cells is one of the important hallmarks of successful tissue generation on these platforms. The biomechanical behavior of cells profoundly affects the physiological functions of the generated tissue. In this work, a designer nanofibrous cell culture insert (NCCI) device was developed, consisting of a free-hanging polymeric nanofibrous membrane. The free-hanging nanofibrous membrane has a well-tailored architecture, stiffness, and topography to better mimic the extracellular matrix of any soft tissue than conventional, flat tissue culture polystyrene (TCPS) surfaces. Human keratinocytes (HaCaT cells) cultured on the designer NCCIs exhibited a 3D tissue-like phenotype compared to the cells cultured on TCPS. Furthermore, the biomechanical characterization by bio-atomic force microscopy (Bio-AFM) revealed a markedly altered cellular morphology and stiffness of the cellular cytoplasm, nucleus, and cell-cell junctions. The nuclear and cytoplasmic moduli were reduced, while the stiffness of the cellular junctions was enhanced on the NCCI compared to cells on TCPS, which are indicative of the fluidic state and migratory phenotype on the NCCI. These observations were corroborated by immunostaining, which revealed enhanced cell-cell contact along with a higher expression of junction proteins and enhanced migration in a wound-healing assay. Taken together, these results underscore the role of the novel designer NCCI device as an in vitro platform for epithelial cells with several potential applications, including drug testing, disease modeling, and tissue regeneration.

Fabrication of gelatin/silk fibroin/phage nanofiber scaffold effective against multidrug resistant Pseudomonas aeruginosa

OBJECTIVE

The alarming rise of multi-drug resistant (MDR) Pseudomonas aeruginosa has prompted the World Health Organization to consider it a serious threat to human health. Although phage (Phg), an effective antibacterial treatment option, can maintain long-term infectivity via lyophilized storage, freeze-drying can be expensive and time-consuming. Thus, we propose electrospun gelatin/fibroin (G/F) nanofibrous formulation for dehydrating and storing phage against MDR P. aeruginosa.

SIGNIFICANCE

The formulation of phage within the nanofibrous structure of the electrospun G/F scaffold would result in antimicrobial activity against MDR P. aeruginosa leading to enhanced wound healing.

METHODS

Phg effective against MDR P. aeruginosa was isolated, characterized and loaded within G/F nanofibers by electrospinning. Morphology, crystallinity and thermal stability as well as the antimicrobial activity and the biocompatibility of the developed G/F/Phg nanofibers were determined.

RESULTS

Phg-loaded G/F nanofibers revealed an amorphous structure with good thermal stability at temperatures below 300 °C and exhibited effective antibacterial activity against MDR P. aeruginosa with ∼2 log reduction in the bacterial count which increased to ∼4 log reduction in bacterial count after 16 h as compared to both the G/F nanofibers and the negative control. Lack of cytotoxic effects on cultured fibroblasts supported the biocompatibility of G/F/Phg nanofibers.

CONCLUSION

The developed G/F/Phg nanofibers are able to maintain the viability of phage and represent a promising antimicrobial dressing for wounds infected with MDR P. aeruginosa.

Sustained oxygenation accelerates diabetic wound healing by promoting epithelialization and angiogenesis and decreasing inflammation

Nonhealing diabetic wounds are common complications for diabetic patients. Because chronic hypoxia prominently delays wound healing, sustained oxygenation to alleviate hypoxia is hypothesized to promote diabetic wound healing. However, sustained oxygenation cannot be achieved by current clinical approaches, including hyperbaric oxygen therapy. Here, we present a sustained oxygenation system consisting of oxygen-release microspheres and a reactive oxygen species (ROS)-scavenging hydrogel. The hydrogel captures the naturally elevated ROS in diabetic wounds, which may be further elevated by the oxygen released from the administered microspheres. The sustained release of oxygen augmented the survival and migration of keratinocytes and dermal fibroblasts, promoted angiogenic growth factor expression and angiogenesis in diabetic wounds, and decreased the proinflammatory cytokine expression. These effects significantly increased the wound closure rate. Our findings demonstrate that sustained oxygenation alone, without using drugs, can heal diabetic wounds.

Reconstruction of Ultra-thin Alveolar-capillary Basement Membrane Mimics

Alveolar-capillary basement membrane (BM) is ultra-thin (<2 µm) extracellular matrix that maintains integral epithelial-endothelial cell layers. In vitro reconstructions of alveolar-capillary barrier supported on synthetic scaffolds closely resembling the fibrous and ultra-thin natural BM are essential in mimicking the lung pathophysiology. Although BM topology and dimensions are well known to significantly influence cellular behavior, conventionally used BM mimics fail to recreate this natural niche. To overcome this, electrospun ultra-thin 2 µm poly(caprolactone) (PCL) nanofibrous mesh is used to establish an alveolar-capillary barrier model of lung endothelial/epithelial cells. Transepithelial electrical resistance (TEER) and permeability studies reveal integral tight junctions and improved mass transport through the highly porous PCL meshes compared to conventional dense membranes with etched pores. The chemotaxis of neutrophils is shown across the barrier in presence of inflammatory response that is naturally impeded in confined regions. Conventional requirement of 3 µm or larger pore size can lead to barrier disruption due to epithelial/endothelial cell invasion. Despite high porosity, the interconnected BM mimic prevents barrier disruption and allows neutrophil transmigration, thereby demonstrating the physiological relevance of the thin nanofibrous meshes. It is envisioned that these bipolar cultured barriers would contribute to an organ-level in vitro model for pathological disease, environmental pollutants, and nanotoxicology.

Development of Cephradine-Loaded Gelatin/Polyvinyl Alcohol Electrospun Nanofibers for Effective Diabetic Wound Healing: In-Vitro and In-Vivo Assessments

Diabetic wound infections caused by conventional antibiotic-resistant Staphylococcus aureus strains are fast emerging, leading to life-threatening situations (e.g., high costs, morbidity, and mortality) associated with delayed healing and chronic inflammation. Electrospinning is one of the most widely used techniques for the fabrication of nanofibers (NFs), induced by a high voltage applied to a drug-loaded polymer solution. Particular attention is given to electrospun NFs for pharmaceutical applications (e.g., original drug delivery systems) and tissue regeneration (e.g., as tissue scaffolds). However, there is a paucity of reports related to their application in diabetic wound infections. Therefore, we prepared eco-friendly, biodegradable, low-immunogenic, and biocompatible gelatin (GEL)/polyvinyl alcohol (PVA) electrospun NFs (BNFs), in which we loaded the broad-spectrum antibiotic cephradine (Ceph). The resulting drug-loaded NFs (LNFs) were characterized physically using ultraviolet-visible (UV-Vis) spectrophotometry (for drug loading capacity (LC), drug encapsulation efficiency (EE), and drug release kinetics determination), thermogravimetric analysis (TGA) (for thermostability evaluation), scanning electron microscopy (SEM) (for surface morphology analysis), and Fourier-transform infrared spectroscopy (FTIR) (for functional group identification). LNFs were further characterized biologically by in-vitro assessment of their potency against S. aureus clinical strains (N = 16) using the Kirby–Bauer test and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, by ex-vivo assessment to evaluate their cytotoxicity against primary human epidermal keratinocytes using MTT assay, and by in-vivo assessment to estimate their diabetic chronic wound-healing efficiency using NcZ10 diabetic/obese mice (N = 18). Thin and uniform NFs with a smooth surface and standard size (<400 nm) were observed by SEM at the optimized 5:5 (GEL:PVA) volumetric ratio. FTIR analyses confirmed the drug loading into BNFs. Compared to free Ceph, LNFs were significantly more thermostable and exhibited sustained/controlled Ceph release. LNFs also exerted a significantly stronger antibacterial activity both in-vitro and in-vivo. LNFs were significantly safer and more efficient for bacterial clearance-induced faster chronic wound healing. LNF-based therapy could be employed as a valuable dressing material to heal S. aureus-induced chronic wounds in diabetic subjects.

Novel Self-Directing Single-Polymer Jet Developing Layered-Like 3D Buckled Microfibrous Scaffolds for Tissue Engineering Applications

Electrospinning is a promising technique for the fabrication of bioscaffolds in tissue engineering applications. Pertaining issues of multiple polymer jets and bending instabilities result in random paths which lend poor controllability over scaffolds morphology for affecting the porosity and mechanical stability. The present study alleviates these challenges by demonstrating a novel self-directing single jet taking a specifically patterned path to deposit fibers into circular and uniform scaffolds without tuning any externally controlled parameters. High-speed camera observation revealed that the charge retention and dissipation on the collected fibers caused rapid autojet switching between the two jetting modes, namely, a microcantilever-like armed jet motion and a whipping motion, which sequentially expand the area and thickness of the scaffolds, respectively, in a layered-like fashion. The physical properties showed that the self-switching dual-jet modes generated multilayered microfibrous scaffolds (MFSs) with dual morphologies and varied fiber packing density, thereby establishing the gradient porosity and mechanical strength (through buckled fibers) in the scaffolds. In vitro studies showed that as-spun scaffolds are cell-permeable hierarchical 3D microporous structures enabling lateral cell seeding into multiple layers. The cell proliferation on days 6 and 9 increased 21% and 38% correspondingly on MFSs than on nanofibrous scaffolds (NFSs) done by conventional multijets electrospinning. Remarkably, this novel and single-step process is highly reproducible and tunable for developing fibrous scaffolds for tissue engineering applications.

Electrospun Nanofibers of Natural and Synthetic Polymers as Artificial Extracellular Matrix for Tissue Engineering

Many types of polymer nanofibers have been introduced as artificial extracellular matrices. Their controllable properties, such as wettability, surface charge, transparency, elasticity, porosity and surface to volume proportion, have attracted much attention. Moreover, functionalizing polymers with other bioactive components could enable the engineering of microenvironments to host cells for regenerative medical applications. In the current brief review, we focus on the most recently cited electrospun nanofibrous polymeric scaffolds and divide them into five main categories: natural polymer-natural polymer composite, natural polymer-synthetic polymer composite, synthetic polymer-synthetic polymer composite, crosslinked polymers and reinforced polymers with inorganic materials. Then, we focus on their physiochemical, biological and mechanical features and discussed the capability and efficiency of the nanofibrous scaffolds to function as the extracellular matrix to support cellular function.

Electrospun PCL/PLA Scaffolds Are More Suitable Carriers of Placental Mesenchymal Stromal Cells Than Collagen/Elastin Scaffolds and Prevent Wound Contraction in a Mouse Model of Wound Healing

Mesenchymal stem/stromal cells (MSCs) exert beneficial effects during wound healing, and cell-seeded scaffolds are a promising method of application. Here, we compared the suitability of a clinically used collagen/elastin scaffold (Matriderm) with an electrospun Poly(ε-caprolactone)/poly(l-lactide) (PCL/PLA) scaffold as carriers for human amnion-derived MSCs (hAMSCs). We created an epidermal-like PCL/PLA scaffold and evaluated its microstructural, mechanical, and functional properties. Sequential spinning of different PCL/PLA concentrations resulted in a wide-meshed layer designed for cell-seeding and a dense-meshed layer for apical protection. The Matriderm and PCL/PLA scaffolds then were seeded with hAMSCs, with or without Matrigel coating. The quantity and quality of the adherent cells were evaluated in vitro. The results showed that hAMSCs adhered to and infiltrated both scaffold types but on day 3, more cells were observed on PCL/PLA than on Matriderm. Apoptosis and proliferation rates were similar for all carriers except the coated Matriderm, where apoptotic cells were significantly enhanced. On day 8, the number of cells decreased on all carrier types except the coated Matriderm, which had consistently low cell numbers. Uncoated Matriderm had the highest percentage of proliferative cells and lowest apoptosis rate of all carrier types. Each carrier also was topically applied to skin wound sites in a mouse model and analyzed in vivo over 14 days via optical imaging and histological methods, which showed detectable hAMSCs on all carrier types on day 8. On day 14, all wounds exhibited newly formed epidermis, and all carriers were well-integrated into the underlying dermis and showing signs of degradation. However, only wounds treated with uncoated PCL/PLA maintained a round appearance with minimal contraction. Overall, the results support a 3-day in vitro culture of scaffolds with hAMSCs before wound application. The PCL/PLA scaffold showed higher cell adherence than Matriderm, and the effect of the Matrigel coating was negligible, as all carrier types maintained sufficient numbers of transplanted cells in the wound area. The anti-contractive effects of the PCL/PLA scaffold offer potential new therapeutic approaches to wound care.

Biomimetically Mineralized Alginate Nanocomposite Fibers for Bone Tissue Engineering: Mechanical Properties and in Vitro Cellular Interactions

We report herein the structural and mechanical properties and in vitro cellular response of hydroxyapatite (HAp)/alginate nanocomposite fibrous scaffolds mimicking the mineralized collagen fibrils of bone tissue. The biomimetically "engineered" nanocomposites, fabricated by electrospinning and in situ synthesis strategy, were compared with pure alginate nanofibers and micrometer-level HAp/alginate composite fibers. The tensile strength and elastic modulus of the nanocomposites increased by 79.3 and 158.4%, respectively, compared to those of alginate. The uniform nucleation and HAp nanocrystal growth on the alginate nanofibers resulted in such enhancement of the mechanical properties via a stress-transfer effect. Rat calvarial osteoblasts were stably attached and stretched more extensively on the nanocomposites' surface than on the pristine alginate. The controlled deposition of the HAp nanophase contributed to a much faster cell proliferation rate on the nanocomposites than on the others. The improved structural stability and osteoblast interactions suggest the fibrous nanocomposite scaffold's potential advantages for bone tissue regeneration.

Electrospun Biomaterials in the Treatment and Prevention of Scars in Skin Wound Healing

Electrospinning is a promising method for the rapid and cost-effective production of nanofibers from a wide variety of polymers given the high surface area morphology of these nanofibers, they make excellent wound dressings, and so have significant potential in the prevention and treatment of scars. Wound healing and the resulting scar formation are exceptionally well-characterized on a molecular and cellular level. Despite this, novel effective anti-scarring treatments which exploit this knowledge are still clinically absent. As the process of electrospinning can produce fibers from a variety of polymers, the treatment avenues for scars are vast, with therapeutic potential in choice of polymers, drug incorporation, and cell-seeded scaffolds. It is essential to show the new advances in this field; thus, this review will investigate the molecular processes of wound healing and scar tissue formation, the process of electrospinning, and examine how electrospun biomaterials can be utilized and adapted to wound repair in the hope of reducing scar tissue formation and conferring an enhanced tensile strength of the skin. Future directions of the research will explore potential novel electrospun treatments, such as gene therapies, as targets for enhanced tissue repair applications. With this class of biomaterial gaining such momentum and having such promise, it is necessary to refine our understanding of its process to be able to combine this technology with cutting-edge therapies to relieve the burden scars place on world healthcare systems.

From Dermal Patch to Implants-Applications of Biocomposites in Living Tissues

Composites are composed of two or more materials, displaying enhanced performance and superior mechanical properties when compared to their individual components. The use of biocompatible materials has created a new category of biocomposites. Biocomposites can be applied to living tissues due to low toxicity, biodegradability and high biocompatibility. This review summarizes recent applications of biocomposite materials in the field of biomedical engineering, focusing on four areas-bone regeneration, orthopedic/dental implants, wound healing and tissue engineering.

Isolation, Characterization, and Safety Evaluation of Human Skin-Derived Precursors from an Adherent Monolayer Culture System

Background

Skin-derived precursors (SKPs) are promising candidates for regenerative medicine. Several studies have transcultured human SKPs (termed tSKPs) from fibroblasts (FBs) expanded in monolayer culture. Herein, we optimized the procedure by treating flasks with poly-2-hydroxyethyl methacrylate (poly-HEMA).

Methods

tSKPs generated from our adherent monolayer culture system were investigated for protein expression and differentiation capacity. The aggregated cells and the proliferative cells within tSKP spheres were detected by mix-culturing FBs expressing two different fluorescent proteins and BrdU- or EdU-positive cells, respectively. To distinguish tSKPs from FBs, we compared their phenotypes and transcriptomes. The tumorigenicity of tSKPs and FBs was also assessed in our study.

Results

tSKPs expressed Versican, Fibronectin, Vimentin, Sox2, and Nestin. Under appropriate stimuli, tSKPs could differentiate to mesenchymal or neural lineages. While these spheres were heterogeneous populations consisting of both proliferative and aggregated cells, the rate of proliferative cells correlated with a seeding density. tSKPs, isolated from FBs, were distinctive from FBs in cell cycle, marker expression, neural differentiation potential, and transcript profiles despite the two sharing partial similarity in certain properties. As for tumorigenesis, both tSKPs and FBs could be considered as nontumorigenic ex vivo and in vivo.

Conclusion

tSKPs were heterogeneous populations presenting similar characteristics as traditional SKPs, while being different from FBs. The potential mixture of FBs in spheres did not affect the biosafety of tSKPs, as both of which had normal karyotype and nontumorigenicity. Taken together, we suggested tSKPs had potential applications in regenerative medicine.

Titanium Nanorods Loaded PCL Meshes with Enhanced Blood Vessel Formation and Cell Migration for Wound Dressing Applications

Proper management of nonhealing wounds is an imperative clinical challenge. For the effective healing of chronic wounds, suitable wound coverage materials with the capability to accelerate cell migration, cell proliferation, angiogenesis, and wound healing are required to protect the healing wound bed. Biodegradable polymeric meshes are utilized as effective wound coverage materials to protect the wounds from the external environment and prevent infections. Among them, electrospun biopolymeric meshes have got much attention due to their extracellular matrix mimicking morphology, ability to support cell adhesion, and cell proliferation. Herein, electrospun nanocomposite meshes based on polycaprolactone (PCL) and titanium dioxide nanorods (TNR) are developed. TNR incorporated PCL meshes are fabricated by electrospinning technique and characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy (FTIR) analysis, and X-Ray diffraction (XRD) analysis. In vitro cell culture studies, in ovo angiogenesis assay, in vivo implantation study, and in vivo wound healing study are performed. Interestingly, obtained in vitro and in vivo results demonstrated that the presence of TNR in the PCL meshes greatly improved the cell migration, proliferation, angiogenesis, and wound healing. Owing to the above superior properties, they can be used as excellent biomaterials in wound healing and tissue regeneration applications.

Advanced drug delivery systems and artificial skin grafts for skin wound healing

Cutaneous injuries, especially chronic wounds, burns, and skin wound infection, require painstakingly long-term treatment with an immense financial burden to healthcare systems worldwide. However, clinical management of chronic wounds remains unsatisfactory in many cases. Various strategies including growth factor and gene delivery as well as cell therapy have been used to enhance the healing of non-healing wounds. Drug delivery systems across the nano, micro, and macroscales can extend half-life, improve bioavailability, optimize pharmacokinetics, and decrease dosing frequency of drugs and genes. Replacement of the damaged skin tissue with substitutes comprising cell-laden scaffold can also restore the barrier and regulatory functions of skin at the wound site. This review covers comprehensively the advanced treatment strategies to improve the quality of wound healing.

Naturally-derived electrospun wound dressings for target delivery of bio-active agents

Electrospun nanofibers are known as the advanced means for wound dressing. They have represented remarkable potency to encapsulate and deliver biomolecules promoting the wound healing process. Compared to synthetic polymers, naturally derived polymers (NDP) are more qualified candidates for fabrication of biomedical electrospun scaffolds. Not only nanofibers of NDP illustrate higher biocompatibility and biodegradability rates, but also they mimic the native extracellular matrix more closely, which leads to the wound closure acceleration by enhancing tissue regeneration. Aside, incorporation of bioactive molecules and therapeutic agents into the nanofibers can generate innovative bioactive wound dressings with significantly improved healing potentials. This paper starts with a brief discussion on the steps and factors influencing the wound healing process. Then, the recent applications of electrospun nanofibers as wound dressing with healing accelerating properties are reviewed. Further, the various healing agents and alternative strategies for modification and functionalization of bioactive naturally-derived electrospun nanofibers are discussed.

Polydopamine modification of silk fibroin membranes significantly promotes their wound healing effect

Natural polymer-based wound dressings have gained great attention in skin tissue engineering.

[Experimental study on long-term outcome of porcine collagen membrane xenotransplantation in vivo]

Objective

To observe the long-term outcome and biocompatibility of the porcine collagen membrane (DermalGen) after xenotransplantation in vivo.

Methods

Twenty Sprague Dawley rats were randomly divided into 2 groups ( n=10). DermalGen were implanted subcutaneously into the dorsum of rats in experimental group, and the rats in control group were treated with sham-operation. At 3, 7, and 15 days and 1, 3, 6, and 12 months after operation, the samples of experimental group were harvested and gross observation, histological observation, CD31 immunohistochemical staining, and transmission electron microscope observation were taken to observe the inflammatory reaction, angiogenesis, and collagen arrangement. The skin tissues of the control group at 12 months were observed and compared.

Results

All incisions healed in experimental group, without obvious swelling and inflammatory reaction. The DermalGen was closely contact with the surrounding tissue without obvious rejection, and it was still legible at 12 months. Histological observation of experimental group showed that the infiltration of fibroblasts and inflammatory cells were seen at 7 days. More capillaries and fibroblast cells were seen and the inflammatory response gradually faded at 15 days and 1 month. There were abundant vessels and cells in the DermalGen at 3 months. The angiogenesis and fibroblasts decreased gradually, and the collagen started to format and margin blended simultaneously at 6 and 12 months. The inflammatory cells in experimental group at 15 days and 1 month were significantly more than that in control group ( P<0.05), and no significant difference was found at 12 months between experimental group and control group ( P>0.05). Immunohistochemical staining of experimental group showed that the angiogenesis changed obviously with the time, and the density of vessels decreased significantly at 12 months. Compared with control group, the possitive expressions of CD31 in experimental group at 15 days and 12 months after operation were significantly decreased ( P<0.05), and were significantly increased at 1 month ( P<0.05). Transmision electron microscope observation showed that the arrangement of collagen in grafted DermalGen had no obvious changed when compared with the DermalGen, and vascular endothelial cell, capillarypericytes and fibroblast cells could be seen inside.

Conclusion

The DermalGen structure is stable after long-term xenotransplantation and with good tolerogenic property in vivo.

The Human Skin-Derived Precursors for Regenerative Medicine: Current State, Challenges, and Perspectives

Skin-derived precursors (SKPs) are an adult stem cell source with self-renewal and multipotent differentiation. Although rodent SKPs have been discussed in detail in substantial studies, human SKPs (hSKPs) are rarely reported. Understanding the biological properties and possible mechanisms underlying hSKPs has important implications for regenerative medicine particularly clinical applications, as human-derived sources are more suitable for clinical transplantation. The finding that hSKPs derivatives, such as neural and mesodermal progeny, have both in vitro and in vivo function without any genetical modification makes hSKPs a trustable, secure, and accessible resource for cell-based therapy. Here, we provide an overview of hSKPs, describing their characteristics, originations and niches, and potential applications. A comparison between traditional and innovative culture methods used for hSKPs is also introduced. Furthermore, we discuss the challenges and the future perspectives towards the field of hSKPs. With this review, we hope to point out the current stage of hSKPs and highlight the problems that remain in this field.