Blending and Morphology Control To Turn Hydrophobic SEBS Electrospun Mats Superhydrophilic

Structural Control of Nanofibers According to Electrospinning Process Conditions and Their Applications

Nanofibers have gained much attention because of the large surface area they can provide. Thus, many fabrication methods that produce nanofiber materials have been proposed. Electrospinning is a spinning technique that can use an electric field to continuously and uniformly generate polymer and composite nanofibers. The structure of the electrospinning system can be modified, thus making changes to the structure, and also the alignment of nanofibers. Moreover, the nanofibers can also be treated, modifying the nanofiber structure. This paper thoroughly reviews the efforts to change the configuration of the electrospinning system and the effects of these configurations on the nanofibers. Excellent works in different fields of application that use electrospun nanofibers are also introduced. The studied materials functioned effectively in their application, thereby proving the potential for the future development of electrospinning nanofiber materials.

A facile one-stone-two-birds strategy for fabricating multifunctional 3D nanofibrous scaffolds

Local bacterial infections lead to delayed wound healing and in extreme cases, such as diabetic foot ulcers, to non-healing due to the impaired cellular function in such wounds. Thus, many scientists have focused on developing advanced therapeutic platforms to treat infections and promote cellular proliferation and angiogenesis. This study presents a facile approach for designing nanofibrous scaffolds in three dimensions (3D) with enhanced antibacterial activity to meet the need of treating chronic diabetic wounds. Being a cationic surfactant as well as an antimicrobial agent, octenidine (OCT) makes a 2D membrane hydrophilic, enabling it to be modified into a 3D scaffold in a "one stone, two birds" manner. Aqueous sodium borohydride (NaBH4) solution plays a dual role in the fabrication process, functioning as both a reducing agent for the in situ synthesis of silver nanoparticles (Ag NPs) anchored on the nanofiber surface and a hydrogen gas producer for expanding the 2D membranes into fully formed 3D nanofiber scaffolds, as demonstrated by morphological analyses. Various techniques were used to characterize the developed scaffold (e.g., SEM, XRD, DSC, FTIR, and surface wettability), demonstrating a multilayered porous structure and superhydrophilic properties besides showing sustained and prolonged release of OCT (61% ± 1.97 in 144 h). Thanks to the synergistic effect of OCT and Ag NPs, the antibacterial performance of the 3D scaffold was significantly higher than that of the 2D membrane. Moreover, cell viability was studied in vitro on mouse fibroblasts L929, and the noncytotoxic character of the 3D scaffold was confirmed. Overall, it is shown that the obtained multifunctional 3D scaffold is an excellent candidate for diabetic wound healing and skin repair.

Durable Light-Driven Three-Dimensional Smart Switchable Superwetting Nanotextile as a Green Scaled-Up Oil-Water Separation Technology

Stimuli-responsive polymer architectures are attracting a lot of interest, but it still remains a great challenge to develop effective industrial-scale strategies. A single-stage and cost-effective approach was applied to fabricate a three-dimensional (3D) smart responsive surface with fast and reversibly switchable wetting between superhydrophobicity and superhydrophilicity/underwater superoleophobicity properties induced by photo and heat stimuli. Commercially available PVDF and P25TiO₂ as starting materials fabricated with a scaled-up electrospinning approach were applied to prepare 3D smart switchable PVDF-P25TiO₂ nanotextile superwetted by both UV and solar light that is simply recovered by heat at a reasonable time. The superhydrophilic/underwater superoleophobic photo-induced nanotextile will act in "water-removing" mode in which water quickly passes through and the oil is blocked on the surface. An acceptable recycling, reusing, and superior antifouling and self-cleaning performance arising from a TiO₂ photocatalytic effect makes it highly desired in a green scaled-up industry oily wastewater treatment technology. With these advantages, a large-scale industrial production process can be simply simulated by applying a conducting mesh-like collector substrate.

Reduction of thrombotic and inflammatory complications of polystyrene-block-polyisoprene-block-polystyrene (SIS) with one-step electrospinning

Polystyrene-block-polyisoprene-block-polystyrene (SIS) has been used as biomaterials due to its soft and stable properties under physiological conditions. However, the thrombotic and inflammatory complications caused by SIS restrain its application as blood-contacting implant. To overcome this problem, the hydrophilic core-shell structured SIS-based microfiber with antioxidant encapsulation is fabricated with one-step reactive electrospinning. We demonstrate that the phase separation of SIS and acylated Pluronic F127 (F127-DA) components and crosslinking during electrospinning renders the microfiber blood compatible and stable under physiological condition; the encapsulation of 2-O-d-glucopyranosyl-l-ascorbic acid (AA-2G) in microfiber and subsequent release of AA-2G detoxifies the excess reactive oxygen species (ROS). The microfibers are nontoxic to cells and promote the fast growth and proliferation of human umbilical vein endothelial cells (HUVECs) in the presence of ROS; the thrombotic and inflammatory complications are effectively reduced with implant evaluation in vivo. Therefore, our work paves a new way to improve the biocompatibility of SIS, making it a promising candidate for blood contact materials.

Lactonic Sophorolipid Increases Surface Wettability of Poly-l-lactic Acid Electrospun Fibers

The hydrophobicity of electrospun poly-l-lactic acid (PLLA) fibers hinders their integration with surrounding tissue for a variety of applications. In this study, we increased PLLA fiber hydrophilicity by incorporating the natural surfactant, lactonic sophorolipid (LSL). PLLA+LSL fibers had similar fiber morphology but significantly greater surface wettability, which suggested LSL accumulation on the fiber surface. Differential scanning calorimetry results also suggested that LSL was phase separated from PLLA. Despite the altered surface wettability of these fibers, there was no change in fibroblast adhesion. Future studies may explore the use of this natural surfactant to deliver bioactive factors to enhance fibroblast adhesion.

A comprehensive review of electrospinning block copolymers

Electrospinning provides a versatile and cost-effective route for the generation of continuous nanofibres with high surface area-to-volume ratio from various polymers. In parallel, block copolymers (BCPs) are promising candidates for many diverse applications, where nanoscale operation is exploited, owing to their intrinsic self-assembling behaviour at these length scales. Judicious combination of BCPs (with their ability to make nanosized domains at equilibrium) and electrospinning (with its ability to create nano- and microsized fibres and particles) allows one to create BCPs with high surface area-to-volume ratio to deliver higher efficiency or efficacy in their given application. Here, we give a comprehensive overview of the wide range of reports on BCP electrospinning with focus placed on the use of molecular design alongside control over specific electrospinning type and post-treatment methodologies to control the properties of the resultant fibrous materials. Particular attention is paid to the applications of these materials, most notably, their use as biomaterials, separation membranes, sensors, and electronic materials.

Surfactant-assisted-water-exposed versus surfactant-aqueous-solution-exposed electrospinning of novel super hydrophilic polycaprolactone based fibers: Analysis of drug release behavior

Surface hydrophilicity and scaffold integrity determine the drug release behavior of drug loaded electrospun fibrous mats. When mixture miscibility is acceptable, blend electrospinning of hydrophobic with hydrophilic polymers can improve scaffold hydrophilicity while the hydrophobic polymer maintains the mechanical strength of scaffold. Polycaprolactone (PCL) and Pluronic P123 (P123) blend electrospinning has been investigated. In routine blend electrospinning, surface enrichment of Pluronic sets a limit for P123 weight ratio in which exceeding from that limit causes the excess P123 to be accumulated within the electrospun fiber core. To overcome this setback, a method named surfactant assisted water exposed (SAWE) electrospinning was introduced which was proven to be effective for increasing the surface enrichment of Pluronic. In order to test the validity of this method, the electrospinning of solution containing PCL which is exposed to aqueous solution of P123 was investigated. This new method was named surfactant aqueous solution exposed (SASE) electrospinning. Myelin formation at the contact interface of aqueous solution and chloroform solution was studied and it was found that this layer can effectively barricade the migration of Pluronic chains between immiscible phases. For SASE, fiber surface coverage by P123 was uneven and loose. Electrospun scaffolds from SAWE and SASE were loaded with drug to investigate the effect of the exposure time during electrospinning on in vitro drug release. By increasing the exposure time, the abnormal two-stage phased release profile of SAWE became normal with moderate initial burst. Longer exposure time increased the initial burst of the drug loaded SASE fibers. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 597-609, 2019.

Dexamethasone loaded multi-layer poly-l-lactic acid/pluronic P123 composite electrospun nanofiber scaffolds for bone tissue engineering and drug delivery

In tissue engineering, it is common to mix drugs that can control proliferation and differentiation of cells into polymeric solutions as part of composite to get bioactive scaffolds. However, direct incorporation of drugs might potentially result in undesired burst release. To overcome this problem, here we developed electrospun multilayer drug loaded poly-l-lactic acid/pluronic P123 (PLLA-P123) composite scaffolds. The drug was loaded into the middle layer. The surface, the mechanical and physiochemical properties of the scaffolds were evaluated. The drug release profiles were monitored. Finally, the osteogenic proliferation and differentiation potential were determined. The scaffolds fabricated here have appropriate surface properties, but with different mechanical strength and osteogenic proliferation and differentiation. Multi-layer scaffolds where the drug was in the middle layer and PLLA-plasma and PLLA-P123 with cover layer showed the best osteogenic proliferation and differentiation than the other groups of scaffolds. The drug release profiles of the scaffolds were completely different: single layer scaffolds showed burst release within the first day, while multilayer scaffolds showed controlled release. Therefore, the multilayer drug loaded scaffolds prepared have dual benefits can provide both better osteogenesis and controlled release of drugs and bioactive molecules at the implant site.

Bioinspired Antioxidant Defense System Constructed by Antioxidants-Eluting Electrospun F127-Based Fibers

Cells were continuously exposed to oxidative damage by overproduction of reactive oxygen species (ROS) when they contacted implanted biomaterials. The strategy to prevent cells from oxidative injures remains a challenge. Inspired by the antioxidant defense system of cells, we constructed a biocompatible and ROS-responsive architecture on the substrate of styrene-b-(ethylene-co-butylene)-b-styrene elastomer (SEBS). The strategy was based on fabrication of architectures through reactive electrospinning of mixture including SEBS, acylated Pluronic F127, copolymer of poly(ethylene glycol) diacrylate and 1,2-ethanedithiol (PEGDA-EDT), and antioxidants (AA-2G) and ROS-triggered release of AA-2G from microfibers to detoxify the excess ROS. We demonstrated that the stable and hydrophilic architecture was constructed by phase separation of SEBS/F127 components and cross-linking between polymer chains during electrospinning; the ROS-responsive fibers controlled the release of AA-2G and the interaction of AA-2G with ROS reduced the oxidative damage to cells. The bioinspired architecture not only reduced mechanical and oxidative damage to cells but also maintained normal ROS level for physiological hemostasis. This work provides basic principles to design and develop antioxidative biomaterials for implantation in vivo.

An improved surface for enhanced stem cell proliferation and osteogenic differentiation using electrospun composite PLLA/P123 scaffold

Poly-L-lactic acid (PLLA) nano fibrous scaffolds prepared by electrospinning technology have been used widely in tissue engineering applications. However, PLLA scaffolds are hydrophobic in nature, moreover the fibrous porous structure produced by electrospinning makes the scaffolds even more hydrophobic which generally limits cell attachment and proliferation. Polymer blending is one of the several efforts used so far to enhance hydrophilicity and recognized as an easy cost-effective approach for the manipulation physiochemical properties of polymeric biomaterials. Pluronic block copolymers containing hydrophilic poly(ethylene oxide) (PEO) blocks and hydrophobic poly(propylene oxide) (PPO) blocks are arranged in triblock structure: PEO-PPO-PEO. It is commonly used recently to blend hydrophobic polymers to enhance hydrophilicity for pharmaceutical and tissue engineering applications. In this study, novel pluronic P123 blend PLLA electrospun nanofibre scaffolds with improved hydrophilicity and biological properties were fabricated. The surface morphology and surface chemistry of the nanofibre scaffolds were characterized by scanning electron microscope (SEM) and FTIR analyses. Surface hydrophilicity and change in mechanical properties were studied. The ability of the scaffolds to support the attachment, and proliferation and differentiation of human adipose tissue derived MSCs, were evaluated generally. The fabricated scaffolds have completely improved, hydrophilicity, similar osteogenic differentiation potential with plasma-treated PLLA nanofibre scaffold, and hence P123 blend PLLA electrospun nanofibre scaffolds are a very good and cost effective choice as a scaffold for bone tissue engineering application.

Improvement of heat transfer by promoting dropwise condensation using electrospun polytetrafluoroethylene thin films

Homogeneous superhydrophobic PTFE thin films showed stable dropwise condensation and much higher heat transfer. They contribute to energy-efficient transfer.

Wetting of Hydrophilic Electrospun Mats Produced by Blending SEBS with PEO-PPO-PEO Copolymers of Different Molecular Weight

The interaction of electrospun mats with water is critical for many possible applications, and the water contact angle on the surface is the parameter usually measured to characterize wetting. Although useful for hydrophobic surfaces, this approach is limited for hydrophilic mats, where wicking also has to be considered. In this case, it is still unclear how the fiber surface chemical composition and morphology will affect the wetting behavior of electrospun mats. In this work, wetting was studied with different hydrophilic membranes produced by blending thermoplastic elastomer poly(styrene)-b-poly(ethylene-butylene)-b-poly(styrene) (SEBS) with amphiphilic poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) molecules. Three different types of PEO-PPO-PEO, with different molar masses, PEO content, and physical form were used. The effect of these differences on the wetting behavior of the electrospun mats was evaluated by contact angle goniometry, wicking measurements, and different imaging techniques. X-ray photoelectron spectroscopy was used to characterize the surface chemical composition. The smaller molecules quickly saturated the surface at low concentrations, making the mats hydrophilic. The sheath of PEO-PPO-PEO also resulted in fast absorption of water, when comparing the saturated and nonsaturated surfaces. Longer PEO chain-ends seemed to hinder complete segregation and also led to a higher activation time when in contact with water. Liquid PEO-PPO-PEO was easily leached by water.

Thermally induced chemical cross-linking reinforced fluorinated polyurethane/polyacrylonitrile/polyvinyl butyral nanofibers for waterproof-breathable application

Thermally induced chemical cross-linking could enhance the FPAN/PVB/BIP composite nanofibrous membranes with robust mechanical, waterproof and breathable performance.