Preparation of sodium alginate/poly(ethylene oxide) blend nanofibers with lecithin

Alginate-based nanocarriers for the delivery and controlled-release of bioactive compounds

Alginate-based nanocarriers are propitious vehicles used for the delivery of bioactive compounds (bioactives). In this area, calcium alginate and sodium alginate are the most promising wall materials because they are nontoxic, comparatively cheap, simple in production, biocompatible and biodegradable. In this review, we have highlighted different alginate-based nanocarriers such as nanoparticles, nanofibers, nanoemulsions, nanocomplexes, and nanohydrogels; also entrapment of different bioactives within alginate nanocarriers and their bioavailability in the gastric environment has been comprehensively discussed. Being biopolymers, alginates can be exploited as emulsifiers/ encapsulants for entrapment and delivery of different bioactives such as vitamins, minerals, essential fatty acids, peptides, essential oils, bioactive oils, polyphenols and carotenoids. Furthermore, the use of alginate-based nanocarriers in combination with other polysaccharides/ emulsifiers was recognized as the most effective and favorable approach for the protection, delivery and sustained release of bioactives.

Development of silk fibroin‑sodium alginate scaffold loaded silk fibroin nanoparticles for hemostasis and cell adhesion

During wound healing process, it is essential to promote hemostasis and cell adhesion. Herein, we incorporated a scaffold with nanoparticles to improve the hemostatic properties and stimulate cell adhesion. The nanoparticles were prepared by self-assembling of silk fibroin, and the scaffold loaded nanoparticles were synthesized by crosslinking and freeze-drying. Macroscopical images showed that the nanoparticles distributed uniformly and increased the surface roughness of scaffold pore wall. The addition of nanoparticles decreased the pore size, enhanced the compression strength, lowered the degradation rate, and maintained the resilience and water uptake capacity. Compared with pure scaffold, the scaffold loaded nanoparticles revealed higher blood clotting index and promoted platelets adhesion. Furthermore, in vitro tests showed that scaffold loaded nanoparticles exhibited excellent biocompatibility, and stimulation effects on cell proliferation, migration, and adhesion for both L929 cells and HUVECs. Therefore, the scaffold loaded nanoparticles possessed great potential as a wound dressing for efficient hemostasis and subsequent wound healing.

ELECTROSPUN SODIUM ALGINATE/POLY(ETHYLENE OXIDE) NANOFIBERS FOR WOUND HEALING APPLICATIONS: CHALLENGES AND FUTURE DIRECTIONS

Alginate is an interesting natural biopolymer to be considered for biomedical applications due to its advantages and good biological properties. These biological properties make electrospun alginate nanofibers suitable for various uses in the biomedical field, such as wound healing dressings, drug delivery systems, or both. Unfortunately, the fabrication of alginate nanofibers by electrospinning is very challenging because of the high viscosity of the solution, high surface tension and rigidity in water due to hydrogen bonding, and also their diaxial linkages. This review presents an overview of the factors affecting the electrospinning process of sodium alginate/poly(ethylene oxide) (SA/PEO), the application of SA/PEO in drug delivery systems for wound healing applications, and the degradation and swelling properties of SA/PEO. The challenges and future directions of SA/PEO in the medical field are also discussed.

Nutrient alloying elements in biodegradable metals: a review

As a new generation of biomedical metallic materials, biodegradable metals have become a hot research topic in recent years because they can completely degrade in the human body, thus preventing secondary surgery, and reducing the pain and economic burden for patients. Clinical applications require biodegradable metals with adequate mechanical properties, corrosion resistance, and biocompatibility. Alloying is an important method to create biodegradable metals with required and comprehensive performances. Since nutrient elements already have important effects on various physiological functions of the human body, the alloying of nutrient elements with biodegradable metals has attracted much attention. The present review summarizes and discusses the effects of nutrient alloying elements on the mechanical properties, biodegradation behavior, and biocompatibility of biodegradable metals. Moreover, future research directions of biodegradable metals with nutrient alloying elements are suggested.

Current Trends in Advanced Alginate-Based Wound Dressings for Chronic Wounds

Chronic wounds represent a major public health issue, with an extremely high cost worldwide. In healthy individuals, the wound healing process takes place in different stages: inflammation, cell proliferation (fibroblasts and keratinocytes of the dermis), and finally remodeling of the extracellular matrix (equilibrium between metalloproteinases and their inhibitors). In chronic wounds, the chronic inflammation favors exudate persistence and bacterial film has a special importance in the dynamics of chronic inflammation in wounds that do not heal. Recent advances in biopolymer-based materials for wound healing highlight the performance of specific alginate forms. An ideal wound dressing should be adherent to the wound surface and not to the wound bed, it should also be non-antigenic, biocompatible, semi-permeable, biodegradable, elastic but resistant, and cost-effective. It has to give protection against bacterial, infectious, mechanical, and thermal agents, to modulate the level of wound moisture, and to entrap and deliver drugs or other molecules This paper explores the roles of alginates in advanced wound-dressing forms with a particular emphasis on hydrogels, nanofibers networks, 3D-scaffolds or sponges entrapping fibroblasts, keratinocytes, or drugs to be released on the wound-bed. The latest research reports are presented and supported with in vitro and in vivo studies from the current literature.

Preparation of Alginate-Based Biomaterials and Their Applications in Biomedicine

Alginates are naturally occurring polysaccharides extracted from brown marine algae and bacteria. Being biocompatible, biodegradable, non-toxic and easy to gel, alginates can be processed into various forms, such as hydrogels, microspheres, fibers and sponges, and have been widely applied in biomedical field. The present review provides an overview of the properties and processing methods of alginates, as well as their applications in wound healing, tissue repair and drug delivery in recent years.

Facile fabrication of phospholipid-functionalized nanofiber-based barriers with enhanced anti-adhesion efficiency

Electrospun nanofibrous membranes (NFMs) have attracted considerable attention as a potential physical barrier for reducing postoperative adhesion. However, no anti-adhesion barrier can completely prevent adhesion formation. In this study, phospholipid-functionalized NFMs were readily fabricated by one-step electrospinning to obtain nanofiber-based barriers with enhanced wettability and anti-adhesion efficiency. The optimized phospholipid NFMs were shown to have a fiber diameter of 831 nm ± 135 nm that is drastically decreasing, high porosity of 87.6 % ± 1.1 %, and superior hydrophilicity. Moreover, the phospholipid NFMs with excellent cytocompatibility exhibited fibroblasts being significantly reduced (≈ 51 %) after incubation of 3 days compared to that of the NFMs (≈ 96 %), confirming long-lasting anti-adhesion capability against fibroblasts. Meanwhile, less cell adhesion and proliferation of Raw 264.7 macrophages on NFM-10Lec indicated its superior anti-inflammatory effects. Thus, the facile phospholipid-functionalized nanofibers provided a promising strategy for anti-adhesion applications.

Preparation and characterisation of a novel silk fibroin/hyaluronic acid/sodium alginate scaffold for skin repair

To mimic the natural structure of tissue extracellular matrix, a novel silk fibroin (SF)/hyaluronic acid (HA)/sodium alginate (SA) composite scaffold (92% in porosity) was prepared by freeze-drying. Fourier-transform infrared spectroscopy and Raman spectra indicated interactions among SF, HA, and SA molecules. Scanning electron microscopy showed that the prepared SF/HA/SA scaffold had soft, elastic characteristics, with an average pore diameter of 93 μm. Mechanical property, thermogravimetric analyses and degradation results indicated that the SF/HA/SA scaffold had good physical stability in body fluid and mechanical movement-related environments. Cell proliferation, morphological, and live-dead analyses showed that NIH-3T3 fibroblast cells were better able to attach, grow, and proliferate on the SF/HA/SA scaffold compared with SF, SF/HA, and SF/SA scaffolds. We evaluated the wound healing effects in a rat full-thickness burn model. The hematoxylin-eosin (H&E) and Masson's trichrome staining results from SF/HA/SA scaffold showed that improved re-epithelialization, enhanced extracellular matrix remodeling. Our findings showed that the prepared SF/HA/SA scaffold can provide a potential way as a wound dressing for skin repair.

Recent Advances in the Use of Algal Polysaccharides for Skin Wound Healing

BACKGROUND

Chronic skin wounds and pressure ulcers represent major health care problems in diabetic individuals, as well as patients who suffered a spinal cord injury. Current treatment methods are only partially effective and such wounds exhibit a high recurrence rate. Open wounds are at high risk of invasive wound infections, which can lead to amputation and further disability. An interdisciplinary approach is needed to develop new and more effective therapies.

METHODS

The purpose of this work is to review recent studies focusing on the use of algal polysaccharides in commercially available as well as experimental wound dressings. Studies that discuss wound dressings based on algal polysaccharides, some of which also contain growth factors and even living cells, were identified and included in this review.

RESULTS AND CONCLUSION

Algal polysaccharides possess mechanical and physical properties, along with excellent biocompatibility and biodegradability that make them suitable for a variety of applications as wound dressings. Furthermore, algal polysaccharides have been used for a dual purpose, namely as wound covering, but also as a vehicle for drug delivery to the wound site.

Alginate in Wound Dressings

Alginate is a biopolymer used in a variety of biomedical applications due to its favourable properties, such as biocompatibility and non-toxicity. It has been particularly attractive in wound healing applications to date. It can be tailored to materials with properties suitable for wound healing. Alginate has been used to prepare different forms of materials for wound dressings, such as hydrogels, films, wafers, foams, nanofibres, and in topical formulations. The wound dressings prepared from alginate are able to absorb excess wound fluid, maintain a physiologically moist environment, and minimize bacterial infections at the wound site. The therapeutic efficacy of these wound dressings is influenced by the ratio of other polymers used in combination with alginate, the nature of cross linkers used, the time of crosslinking, nature of excipients used, the incorporation of nanoparticles, and antibacterial agents. This review provides a comprehensive overview of the different forms of wound dressings containing alginate, in vitro, and in vivo results.

Reactive electrospinning of composite nanofibers of carboxymethyl chitosan cross-linked by alginate dialdehyde with the aid of polyethylene oxide

We have prepared carboxymethyl chitosan-alginate dialdehyde (CMCS-ADA) nanofibers via a reactive electrospinning process with the aid of polyethylene oxide (PEO). The presence of PEO delayed the gelation of CMCS and ADA, thus providing ease of use to adjust the mixing of CMCS-PEO and ADA-PEO blended solution. The mixed solution can be adjusted to come out from the needle before the gel formation or when the gel was just about to form. Defect-free CMCS-ADA-PEO nanofibers with average diameters ranging from 100nm to 900nm were obtained using water as a solvent. The in situ cross-linked CMCS-ADA nanofibers were then obtained following the extraction of water-soluble PEO. After immersion in phosphate-buffered saline (PBS) at a pH of 7.4 for up to 15days, the as-spun CMCS-ADA-PEO composite nanofibers maintained structural integrity, confirming the success of the crosslinking. The PEO-extracted CMCS-ADA nanofibers promoted the adhesion, proliferation and alkaline phosphatase activity of bone marrow stromal cells.

Preparation of Nanofibers with Renewable Polymers and Their Application in Wound Dressing

Renewable polymers have attracted considerable attentions in the last two decades, predominantly due to their environmentally friendly properties, renewability, good biocompatibility, biodegradability, bioactivity, and modifiability. The nanofibers prepared from the renewable polymers can combine the excellent properties of the renewable polymer and nanofiber, such as high specific surface area, high porosity, excellent performances in cell adhesion, migration, proliferation, differentiation, and the analogous physical properties of extracellular matrix. They have been widely used in the fields of wound dressing to promote the wound healing, hemostasis, skin regeneration, and treatment of diabetic ulcers. In the present review, the different methods to prepare the nanofibers from the renewable polymers were introduced. Then the recent progress on preparation and properties of the nanofibers from different renewable polymers or their composites were reviewed; the application of them in the fields of wound dressing was emphasized.

Smart Dressings Based on Nanostructured Fibers Containing Natural Origin Antimicrobial, Anti-Inflammatory, and Regenerative Compounds

A fast and effective wound healing process would substantially decrease medical costs, wound care supplies, and hospitalization significantly improving the patients' quality of life. The search for effective therapeutic approaches seems to be imperative in order to avoid the aggravation of chronic wounds. In spite of all the efforts that have been made during the recent years towards the development of artificial wound dressings, none of the currently available options combine all the requirements necessary for quick and optimal cutaneous regeneration. Therefore, technological advances in the area of temporary and permanent smart dressings for wound care are required. The development of nanoscience and nanotechnology can improve the materials and designs used in topical wound care in order to efficiently release antimicrobial, anti-inflammatory and regenerative compounds speeding up the endogenous healing process. Nanostructured dressings can overcome the limitations of the current coverings and, separately, natural origin components can also overcome the drawbacks of current antibiotics and antiseptics (mainly cytotoxicity, antibiotic resistance, and allergies). The combination of natural origin components with demonstrated antibiotic, regenerative, or anti-inflammatory properties together with nanostructured materials is a promising approach to fulfil all the requirements needed for the next generation of bioactive wound dressings. Microbially compromised wounds have been treated with different essential oils, honey, cationic peptides, aloe vera, plant extracts, and other natural origin occurring antimicrobial, anti-inflammatory, and regenerative components but the available evidence is limited and insufficient to be able to draw reliable conclusions and to extrapolate those findings to the clinical practice. The evidence and some promising preliminary results indicate that future comparative studies are justified but instead of talking about the beneficial or inert effects of those natural origin occurring materials, the scientific community leads towards the identification of the main active components involved and their mechanism of action during the corresponding healing, antimicrobial, or regenerative processes and in carrying out systematic and comparative controlled tests. Once those natural origin components have been identified and their efficacy validated through solid clinical trials, their combination within nanostructured dressings can open up new avenues in the fabrication of bioactive dressings with outstanding characteristics for wound care. The motivation of this work is to analyze the state of the art in the use of different essential oils, honey, cationic peptides, aloe vera, plant extracts, and other natural origin occurring materials as antimicrobial, anti-inflammatory and regenerative components with the aim of clarifying their potential clinical use in bioactive dressings. We conclude that, for those natural occurring materials, more clinical trials are needed to reach a sufficient level of evidence as therapeutic agents for wound healing management.

Advances in skin regeneration: application of electrospun scaffolds

The paucity of cellular and molecular signals essential for normal wound healing makes severe dermatological ulcers stubborn to heal. The novel strategies of skin regenerative treatments are focused on the development of biologically responsive scaffolds accompanied by cells and multiple biomolecules resembling structural and biochemical cues of the natural extracellular matrix (ECM). Electrospun nanofibrous scaffolds provide similar architecture to the ECM leading to enhancement of cell adhesion, proliferation, migration and neo tissue formation. This Review surveys the application of biocompatible natural, synthetic and composite polymers to fabricate electrospun scaffolds as skin substitutes and wound dressings. Furthermore, the application of biomolecules and therapeutic agents in the nanofibrous scaffolds viz growth factors, genes, antibiotics, silver nanoparticles, and natural medicines with the aim of ameliorating cellular behavior, wound healing, and skin regeneration are discussed.

Electrospun Sodium Alginate/Polyethylene Oxide Fibers and Nanocoated Yarns

Sodium alginate (NaAlg), as a natural biopolymer, was electrospun from aqueous solution via blending with a biofriendly synthetic polymer polyethylene oxide. The morphology and chemical properties of resultant alginate-based nanofibers were characterized by using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffractometer (PXRD), and differential scanning calorimetry (DSC). At a wide voltage window (i.e., 12–24 kV), smooth and uniform nanofibers were obtained from the 5.0% concentration with the NaAlg/PEO ratio ranging from 1 : 1 to 1 : 3. The results from FTIR, PXRD, and DSC demonstrate that molecular interaction exists between these two polymers and, therefore, contributes to the alteration of crystallinity of electrospun fibers. In addition, NaAlg/PEO nanofiber-coated polylactic acid (PLA) yarns with different twist levels were also fabricated in this work. The results show that the tensile strength of the nanocoated hybrid yarn and the tensile strength of uncoated yarn increase with the twist per centimeter (TPC) up to 0.5 but decrease when TPC is further increased. The tensile properties of hybrid yarn are superior to those of the uncoated yarn.

Small-diameter tissue engineered vascular graft made of electrospun PCL/lecithin blend

In this study, natural lecithin was incorporated into cholesterol-poly(ε-caprolactone) (Chol-PCL) by solution blending in order to modify the performance of the hydrophobic and bio-inert PCL. The fibrous Chol-PCL/lecithin membranes were fabricated by electrospinning, and the surface morphology and properties were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, static water contact angle, and mechanical tensile testing. The blood compatibility of the scaffolds was evaluated by in vitro hemolysis assay. The cytocompatibility of the scaffolds was investigated by cell adhesion and proliferation using bone-marrow mesenchymal stem cells (MSCs). Subcutaneous implantation was also performed to evaluate the in vivo inflammatory reaction. The tubular tissue-engineered vascular graft (TEVG) was further constructed by rolling cell sheet comprising fibrous membrane and MSCs. Furthermore, endothelial cells (ECs) were seeded onto the lumen of the graft with the aim to form vascular endothelium. The preliminary results indicate that electrospun Chol-PCL/lecithin scaffolds show improved hemocompatibility and cytocompatibility compared with neat Chol-PCL, and combining the Chol-PCL/lecithin fibrous scaffold with MSCs and ECs with well controlled distribution is a promising strategy for constructing TEVGs.