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In this study, aiming to improve the mechanical performance of the Poly (lactic acid) (PLA)-based nanofibrous structures, the electrospinning method was employed to develop twisted yarns with core-shell structure. Within this process, a conventional ring-spun cotton yarn fed to the electrical field, where nanofibers covered it by a certain orientation owning to the twisting procedure. This approach combines the excellent biological and physical-mechanical properties of cotton with outstanding features of the PLA nanofibers for biomedical applications. The effects of the core and shell structures on the ultimate properties of the electrospun core-shell yarns were investigated. Scanning electron microscopy (SEM) demonstrated that relatively uniform and bead-free fibers with smooth surfaces were formed. SEM images also confirmed that the nanofibers were arranged around the core with a specific angle to the axis (with the angle range of 8–44 based on the twisting rate) to constitute a twisted core-shell yarn. The diameter of the electrospun yarns decreased (∼ 22%) by increasing the twist rate. The influence of the core on the mechanical behavior of core-shell yarn are also discussed. Improvements in mechanical performance of core-shell yarns were generally perceived at low twist levels of the core yarn (αe = 2.8), and electrospun shell (40 rpm). Graphical Abstract [ABSTRACT FROM AUTHOR]

Poly(lactic acid)(PLA) is an aliphatic polyester that can be derived from natural and renewable resources. Owing to favorable features, such as biocompatibility, biodegradability, good thermal and mechanical performance, and processability, PLA has been considered as one of the most promising biopolymers for biomedical applications. Particularly, electrospun PLA nanofibers with distinguishing characteristics, such as similarity to the extracellular matrix, large specific surface area and high porosity with small pore size and tunable mechanical properties for diverse applications, have recently given rise to advanced spillovers in the medical area. A variety of PLA-based nanofibrous structures have been explored for biomedical purposes, such as wound dressing, drug delivery systems, and tissue engineering scaffolds. This review highlights the recent advances in electrospinning of PLA-based structures for biomedical applications. It also gives a comprehensive discussion about the promising approaches suggested for optimizing the electrospun PLA nanofibrous structures towards the design of specific medical devices with appropriate physical, mechanical and biological functions. [ABSTRACT FROM AUTHOR]

Core‐shell‐structured polyvinyl alcohol (PVA)‐poly (lactic acid) (PLA) nanofibers combining the hydrophilic trait of PVA and the biocompatibility of PLA were produced using coaxial electrospinning. This allowed the incorporation of AgNO3 in the PVA core of the distinct fibers as shown through transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) showed relatively uniform and bead‐free fibers with smooth surfaces. Ag‐containing fibers show significantly decreased diameters compared with Ag‐free samples as a result of the increased conductivity of the spinning solutions with increasing amounts of AgNO3. In a postsynthetic treatment, the AgNO3 was reduced forming silver nanoparticles (Ag NPs). Ag NPs of 45 to 90 nm size were located in the PVA core but also on the surface of the core‐shell fibers and as individual, agglomerated, and polymer‐coated particles of 100‐200 nm. Powder X‐ray diffraction (PXRD), energy dispersive X‐ray spectroscopy (EDX), and UV‐vis absorption spectroscopy confirmed the increasing amounts of Ag in the core‐shell fibers when using increasing amounts of AgNO3 in the spinning solutions. The antibacterial activity of the nanofiber mats against two prokaryotes Escherichia coli (Gram‐negative) and Staphylococcus aureus (Gram‐positive) increased with increasing amounts of Ag, as expected and produces inhibition zones of 1 to 2 mm. [ABSTRACT FROM AUTHOR]