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The preparation of core–sheath fibers by electrospinning is a topic of significant interest for producing composite fibers with distinct core and sheath functionalities. Moreover, in core–sheath fibers, low-molecular-weight substances or nanosized inorganic additives can be deposited in a targeted manner within the core or the sheath. Commonly, for obtaining a core–sheath structure, coaxial electrospinning is used. It requires a coaxial spinneret and suitable immiscible solvents for the inner and outer solutions. The single-nozzle spinneret electrospinning of emulsions can address these issues, but use of a stabilizing agent is needed. A third approach—preparation of core–sheath fibers by single-nozzle spinneret electrospinning of homogeneous blend solutions of two polymers or of a polymer/low-molecular-weight substance—has been much less studied. It circumvents the difficulties associated with the coaxial and the emulsion electrospinning and is thoroughly discussed in this review. The formation of core–sheath fibers in this case is attributed to phase-separation-driven self-organization during the electrospinning process. Some possibilities for obtaining core–double sheath fibers using the same method are also indicated. The gained knowledge on potential applications of core–sheath fibers prepared by single-nozzle spinneret electrospinning of emulsions and homogeneous blend solutions is also discussed. [ABSTRACT FROM AUTHOR]

Obtaining core-sheath fibers by single-spinneret electrospinning is a recent and straightforward approach to prepare composite fibers. Fibers of more complex architecture consisting of poly(ethylene oxide) (PEO) core, inner poly(Llactide) sheath sd and outer beeswax (BW) sheath may also be obtained using this method. In the present study we report its applicability for a large series of (bio)degradable polyesters such as poly(e-caprolactone), poly(D,L-lactide-co-glycolide), poly(butylene succinate), poly(3-hydroxybutyrate), and poly(L-lactideco- D,L-lactide). The fibers have a well-differentiated PEO core, polyester inner sheath and BW outer sheath. The possibility for targeted location of hydrophilic or hydrophobic substances in the core or in the sheaths of the PEO/polyester/BW fibers has been demonstrated using nanosized zinc oxide with unmodified (hydrophilic) or silanized (hydrophobic) surface. PEO/polyester/BW fibrous materials loaded with a model drug (5-nitro-8-hydroxyquinoline) exhibit antimicrobial activity. The obtained results show that single-spinneret electrospinning is a novel and versatile method to prepare core-double sheath composite fibers prospective for various applications such as biomedicine, cosmetics, and food packaging. [ABSTRACT FROM AUTHOR]

Fibrous materials composed of core–sheath fibers from poly(ethylene oxide) (PEO), beeswax (BW) and 5-nitro-8-hydroxyquinoline (NQ) were prepared via the self-organization of PEO and BW during the single-spinneret electrospinning of a homogeneous blend solution of the partners. Additionally, the application of the same approach enabled the preparation of fibrous materials composed of core–double sheath fibers from PEO, poly(L-lactide) (PLA) and NQ or 5-chloro-7-iodo-8-hydroxyquinoline (CQ), as well as from PEO, poly(ε-caprolactone) (PCL) and NQ. The consecutive selective extraction of BW and of the polyester with hexane and tetrahydrofuran, respectively, evidenced that core–double sheath fibers from PEO/polyester/BW/drug consisted of a PEO core, a polyester inner sheath and a BW outer sheath. In order to evaluate the possibility of the application of fibrous materials from PEO/BW/NQ, PEO/PLA/BW/NQ, PEO/PCL/BW/NQ and PEO/PLA/BW/CQ for plant protection, microbiological studies were performed using both phytopathogenic microorganisms (Pseudomonas corrugata, Fusarium graminearum and Fusarium avenaceum) and beneficial microorganisms (Pseudomonas chlororaphis, Bacillus amyloliquefaciens and Trichoderma asperellum). It was found that the fibrous materials had anti-bacterial and anti-fungal activity against both phytopathogenic and beneficial microorganisms. This is the first report on the activity of fibrous materials loaded with 8-hydroxyquinoline derivatives not only against phytopathogenic but also against beneficial microorganisms that are of importance in agriculture. [ABSTRACT FROM AUTHOR]