Preparation and characterization of poly(ɛ-caprolactone) nonwoven mats via melt electrospinning

Enhancing Tensile Modulus of Polyurethane-Based Shape Memory Polymers for Wound Closure Applications through the Addition of Palm Oil

Thermo-responsive, biocompatible polyurethane (PU) with shape memory properties is highly desirable for biomedical applications. An innovative approach to producing wound closure strips using shape memory polymers (SMPs) is of significant interest. In this work, PU composed of polycaprolactone (PCL) and 1,4-butanediol (BDO) was synthesized using two-step polymerization. Palm oil (PO) was added to PU for enhancing the Young's modulus of the PU beyond the set criterion of 130 MPa. It was found that PU had the ability to crystallize at room temperature and the segments of individual PCL and BDO polyurethanes crystallized separately. The crystalline domains and hard segment of PU greatly affected the tensile properties. The reduction of crystalline domains by the addition of PO and deformation at the higher melting temperature of the crystalline PCL polyurethane phase improved the shape fixity and shape recovery ratios. The new irreversible phase, raised from the permanent deformation upon stretching at the between melting temperature of the crystalline PCL and BDO polyurethanes of 70 °C, resulted in a decrease in shape fixity ratio after the first thermomechanical stretching-recovering cycles. The demonstration of PU as a wound closure strip showed its efficiency and potential until the surgical wound healed.

Electrospinning technologies for the delivery of Biopharmaceuticals: Current status and future trends

This review provides an in-depth exploration of electrospinning techniques employed to produce micro- or nanofibres of biopharmaceuticals using polymeric solutions or melts with high-voltage electricity. Distinct from prior reviews, the current work narrows its focus on the recent developments and advanced applications in biopharmaceutical formulations. It begins with an overview of electrospinning principles, covering both solution and melt modes. Various methods for incorporating biopharmaceuticals into electrospun fibres, such as surface adsorption, blending, emulsion, co-axial, and high-throughput electrospinning, are elaborated. The review also surveys a wide array of biopharmaceuticals formulated through electrospinning, thereby identifying both opportunities and challenges in this emerging field. Moreover, it outlines the analytical techniques for characterizing electrospun fibres and discusses the legal and regulatory requirements for their production. This work aims to offer valuable insights into the evolving realm of electrospun biopharmaceutical delivery systems.

Cell-Biomaterial Constructs for Wound Healing and Skin Regeneration

Over the years, conventional skin grafts, such as full-thickness, split-thickness, and pre-sterilized grafts from human or animal sources, have been at the forefront of skin wound care. However, these conventional grafts are associated with major challenges, including supply shortage, rejection by the immune system, and disease transmission following transplantation. Due to recent progress in nanotechnology and material sciences, advanced artificial skin grafts-based on the fundamental concepts of tissue engineering-are quickly evolving for wound healing and regeneration applications, mainly because they can be uniquely tailored to meet the requirements of specific injuries. Despite tremendous progress in tissue engineering, many challenges and uncertainties still face skin grafts in vivo, such as how to effectively coordinate the interaction between engineered biomaterials and the immune system to prevent graft rejection. Furthermore, in-depth studies on skin regeneration at the molecular level are lacking; as a consequence, the development of novel biomaterial-based systems that interact with the skin at the core level has also been slow. This review will discuss 1) the biological aspects of wound healing and skin regeneration, 2) important characteristics and functions of biomaterials for skin regeneration applications, and 3) synthesis and applications of common biomaterials for skin regeneration. Finally, the current challenges and future directions of biomaterial-based skin regeneration will be addressed.

Morphological and Mechanical Properties of Electrospun Polycaprolactone Scaffolds: Effect of Applied Voltage

The aim of this work is to investigate the effect of the applied voltage on the morphological and mechanical properties of electrospun polycaprolactone (PCL) scaffolds for potential use in tissue engineering. The morphology of the scaffolds was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and the BET techniques for measuring the surface area and pore volume. Stress-strain curves from tensile tests were obtained for estimating the mechanical properties. Additional studies for detecting changes in the chemical structure of the electrospun PCL scaffolds by Fourier transform infrared were performed, while contact angle and X-ray diffraction analysis were realized for determining the wettability and crystallinity, respectively. The SEM, AFM and BET results demonstrate that the electrospun PCL fibers exhibit morphological changes with the applied voltage. By increasing the applied voltage (10 to 25 kV) a significate influence was observed on the fiber diameter, surface roughness, and pore volume. In addition, tensile strength, elongation, and elastic modulus increase with the applied voltage, the crystalline structure of the fibers remains constant, and the surface area and wetting of the scaffolds diminish. The morphological and mechanical properties show a clear correlation with the applied voltage and can be of great relevance for tissue engineering.

Melt Electrospinning of Polymers: Blends, Nanocomposites, Additives and Applications

Melt electrospinning has been developed in the last decade as an eco-friendly and solvent-free process to fill the gap between the advantages of solution electrospinning and the need of a cost-effective technique for industrial applications. Although the benefits of using melt electrospinning compared to solution electrospinning are impressive, there are still challenges that should be solved. These mainly concern to the improvement of polymer melt processability with reduction of polymer degradation and enhancement of fiber stability; and the achievement of a good control over the fiber size and especially for the production of large scale ultrafine fibers. This review is focused in the last research works discussing the different melt processing techniques, the most significant melt processing parameters, the incorporation of different additives (e.g., viscosity and conductivity modifiers), the development of polymer blends and nanocomposites, the new potential applications and the use of drug-loaded melt electrospun scaffolds for biomedical applications.

Biomimicry in Bio-Manufacturing: Developments in Melt Electrospinning Writing Technology Towards Hybrid Biomanufacturing

Melt electrospinning writing has been emerged as a promising technique in the field of tissue engineering, with the capability of fabricating controllable and highly ordered complex three-dimensional geometries from a wide range of polymers. This three-dimensional (3D) printing method can be used to fabricate scaffolds biomimicking extracellular matrix of replaced tissue with the required mechanical properties. However, controlled and homogeneous cell attachment on melt electrospun fibers is a challenge. The combination of melt electrospinning writing with other tissue engineering approaches, called hybrid biomanufacturing, has introduced new perspectives and increased its potential applications in tissue engineering. In this review, principles and key parameters, challenges, and opportunities of melt electrospinning writing, and particularly, recent approaches and materials in this field are introduced. Subsequently, hybrid biomanufacturing strategies are presented for improved biological and mechanical properties of the manufactured porous structures. An overview of the possible hybrid setups and applications, future perspective of hybrid processes, guidelines, and opportunities in different areas of tissue/organ engineering are also highlighted.

Melt Electrospinning Designs for Nanofiber Fabrication for Different Applications

Nanofibers have been attracting growing attention owing to their outstanding physicochemical and structural properties as well as diverse and intriguing applications. Electrospinning has been known as a simple, flexible, and multipurpose technique for the fabrication of submicro scale fibers. Throughout the last two decades, numerous investigations have focused on the employment of electrospinning techniques to improve the characteristics of fabricated fibers. This review highlights the state of the art of melt electrospinning and clarifies the major categories based on multitemperature control, gas assist, laser melt, coaxial, and needleless designs. In addition, we represent the effect of melt electrospinning process parameters on the properties of produced fibers. Finally, this review summarizes the challenges and obstacles connected to the melt electrospinning technique.

Mediating human stem cell behaviour via defined fibrous architectures by melt electrospinning writing

The architecture within which cells reside is key to mediating their specific functions within the body. In this study, we use melt electrospinning writing (MEW) to fabricate cell micro-environments with various fibrous architectures to study their effect on human stem cell behaviour. We designed, built and optimised a MEW apparatus and used it to fabricate four different platform designs of 10.4 ± 2 μm fibre diameter, with angles between fibres on adjacent layers of 90°, 45°, 10° and R (random). Mechanical characterisation was conducted via tensile testing, and human skeletal stem cells (hSSCs) were seeded to scaffolds to study the effect of architecture on cell morphology and mechanosensing (nuclear YAP). Cell morphology was significantly altered between groups, with cells on 90° scaffolds having a lower aspect ratio, greater spreading, greater cytoskeletal tension and nuclear YAP expression. Long term cell culture studies were then conducted to determine the differentiation potential of scaffolds in terms of alkaline phosphatase activity, collagen and mineral production. Across these studies, an increased cell spreading in 3-dimensions is seen with decreasing alignment of architecture correlated with enhanced osteogenesis. This study therefore highlights the critical role of fibrous architecture in regulating stem cell behaviour with implications for tissue engineering and disease progression.

STATEMENT OF SIGNIFICANCE

This is the first study which has investigated the effect of controlled fibrous architectures fabricated via melt electrospinning writing on stem cell behaviour and differentiation. After optimising the fabrication process and characterising scaffolds via SEM and mechanical testing, skeletal stem cells were seeded onto fibrous scaffolds with various micro-architectures. These architectures drove cell shape changes resulting in architecture dependent nuclear YAP localisation, suggesting altered mechanosensing at early time points. In agreement with these early markers, long term cell culture studies revealed for the first time that a 90° fibrous architecture is optimal for the osteogenic differentiation of skeletal stem cells.

Biocompatible, degradable thermoplastic polyurethane based on polycaprolactone-block-polytetrahydrofuran-block-polycaprolactone copolymers for soft tissue engineering

Biodegradable synthetic polymers have been widely used as tissue engineering scaffold materials. Even though they have shown excellent biocompatibility, they have failed to resemble the low stiffness and high elasticity of soft tissues because of the presence of massive rigid ester bonds. Herein, we synthesized a new thermoplastic polyurethane elastomer (CTC-PU(BET)) using poly ester ether triblock copolymer (polycaprolactone-block-polytetrahydrofuran-block-polycaprolactone triblock copolymer, PCTC) as the soft segment, aliphatic diisocyanate (hexamethylene diisocyanate, HDI) as the hard segment, and degradable diol (bis(2-hydroxyethyl) terephthalate, BET) as the chain extender. PCTC inhibited crystallization and reduced the melting temperature of CTC-PU(BET), and BET dramatically enhanced the thermal decomposition and hydrolytic degradation rate when compared with conventional polyester-based biodegradable TPUs. The CTC-PU(BET) synthesized in this study possessed a low tensile modulus and tensile strength of 2.2 MPa and 1.3 MPa, respectively, and an elongation-at-break over 700%. Meanwhile, it maintained a 95.3% recovery rate and 90% resilience over ten cycles of loading and unloading. In addition, the TPU could be electrospun into both random and aligned fibrous scaffolds consisting of major microfibers and nanobranches. 3T3 fibroblast cell culture confirmed that these scaffolds outperformed the conventional biodegradable TPU scaffolds in terms of substrate-cellular interactions and cell proliferation. Considering the advantages of this TPU, such as ease of synthesis, low cost, low stiffness, high elasticity, controllable degradation rate, ease of processability, and excellent biocompatibility, it has great prospects to be used as a tissue engineering scaffold material for soft tissue regeneration.

Melt electrospinning of daunorubicin hydrochloride-loaded poly (ε-caprolactone) fibrous membrane for tumor therapy

Daunorubicin hydrochloride is a cell-cycle non-specific antitumor drug with a high therapeutic effect. The present study outlines the fabrication of daunorubicin hydrochloride-loaded poly (ε-caprolactone) (PCL) fibrous membranes by melt electrospinning for potential application in localized tumor therapy. The diameters of the drug-loaded fibers prepared with varying concentrations of daunorubicin hydrochloride (1, 5, and 10 wt%) were 2.48 ± 1.25, 2.51 ± 0.78, and 2.49 ± 1.58 μm, respectively. Fluorescence images indicated that the hydrophobic drug was dispersed in the hydrophilic PCL fibers in their aggregated state. The drug release profiles of the drug-loaded PCL melt electrospun fibrous membranes were approximately linear, with slow release rates and long-term release periods, and no observed burst release. The MTT assay was used to examine the cytotoxic effect of the released daunorubicin hydrochloride on HeLa and glioma cells (U87) in vitro. The inhibition ratios of HeLa and glioma cells following treatment with membranes prepared with 1, 5, and 10 wt% daunorubicin hydrochloride were 62.69%, 76.12%, and 85.07% and 62.50%, 77.27%, and 84.66%, respectively. Therefore, PCL melt electrospun fibrous membranes loaded with daunorubicin hydrochloride may be used in the local administration of oncotherapy.

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Daunorubicin hydrochloride-loaded PCL fibrous membranes were prepared by melt electrospinning.

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Hydrophilic drug was dispersed in the PCL melt electrospun fiber in the form of aggregation.

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Daunorubicin hydrochloride-loaded PCL fibrous membranes showed low drug release rate and long-term release periods.

Melt electrospinning vs. solution electrospinning: A comparative study of drug-loaded poly (ε-caprolactone) fibres

Curcumin-loaded poly (ε-caprolactone) (PCL) fibres prepared by melt and solution electrospinning methods were both fabricated to investigate their difference in characterization and drug release behaviour. The increasing curcumin content did not influence the morphologies of melt electrospun fibre, but enhanced the range of diameter distribution of solution electrospun fibre owing to the curcumin aggregates in the spinning solution which disturbed the stability of jet. Moreover, a large amount of curcumin with amorphous state could be loaded in the melt electrospun fibre. Whereas the limited solubility of curcumin in the solvent led to the drug aggregates dispersing within the solution electrospun fibre. In addition, the melt electrospun fibres had low drug release rate without burst release on the profiles due to the high crystallinity in the fibre, but high drug release rate and burst release occurred on the release profiles of the solution electrospun fibres because of their low crystallinity, porous structure and roughness surface.

Recent advances in melt electrospinning

With the emergence of one-dimensional (1D) functional nanomaterials and their promising applications, electrospinning (e-spinning) technology and electrospun (e-spun) ultrathin fibers have been widely explored.

Fabrication of microfibrous and nano-/microfibrous scaffolds: melt and hybrid electrospinning and surface modification of poly(L-lactic acid) with plasticizer

Biodegradable poly(L-lactic acid) (PLA) fibrous scaffolds were prepared by electrospinning from a PLA melt containing poly(ethylene glycol) (PEG) as a plasticizer to obtain thinner fibers. The effects of PEG on the melt electrospinning of PLA were examined in terms of the melt viscosity and fiber diameter. Among the parameters, the content of PEG had a more significant effect on the average fiber diameter and its distribution than those of the spinning temperature. Furthermore, nano-/microfibrous silk fibroin (SF)/PLA and PLA/PLA composite scaffolds were fabricated by hybrid electrospinning, which involved a combination of solution electrospinning and melt electrospinning. The SF/PLA (20/80) scaffolds consisted of a randomly oriented structure of PLA microfibers (average fiber diameter = 8.9 µm) and SF nanofibers (average fiber diameter = 820 nm). The PLA nano-/microfiber (20/80) scaffolds were found to have similar pore parameters to the PLA microfiber scaffolds. The PLA scaffolds were treated with plasma in the presence of either oxygen or ammonia gas to modify the surface of the fibers. This approach of controlling the surface properties and diameter of fibers could be useful in the design and tailoring of novel scaffolds for tissue engineering.