Department of Chemsitry, Bioengineering division

The prominent success of polycaprolactone (PCL) electrospun nanofibrous mats (ENM) has expanded the use of PCL over other polymers for tissue engineering applications. However, the major challenge in the design of a nanofibrous scaffold is to modify its surface properties while preserving its bulk properties. Therefore, the first part of the study is focused on the fabrication of PCL-ENMs by alternating-current electrospinning using the following solvent systems: formic acid, formic acid/acetic acid (1/1) and formic acid/acetic acid/acetone (1/1/1). While the second part is focused on an nm-thick surface chemical modification via medium pressure argon and nitrogen plasma treatment, and the third part is dedicated to investigating the morphology, wettability, surface functional groups, crystallite size, crystallinity, crystallization, and melting temperature of plasma-treated nanofibers. Samples were characterized using scanning electron microscopy (SEM), water contact angle analysis...

h i g h l i g h t s The variation of the waveform and frequency of high-voltage alternating current (AC) provides a novel approach to the control of the spinnability and productivity of polycaprolactone electrospun nanofibers (ENF). Unimodal-, bimodal-(beads and spindles) and trimodal-(beads, spindles and helical) structured fiber morphologies are attained as a function of the various waveforms. The square waveform of the highvoltage AC signal provides the highest ENF productivity followed by the sine and triangle waveforms. 50 Hz of all the waveforms results in a 3-fold higher throughput of ENF than do 10 or 20 Hz.

Fabrication of strong antibacterial composite nanofibrous yarns (CNYs) for suture applications by using common direct current electrospinning has been technologically challenging. In this work, we have demonstrated a more straightforward and facile approach to fabricate chlorhexidine (CHX)

Electrospinning technology employs direct current high voltage to produce electrospun fibers from the polymeric liquid or melt. However, until now, the impact of alternating current (AC) high voltage on the spinnability of polymers remains inadequately explored. This work studies the effects of various less toxic solvents and AC high voltage (25 and 32 kV RMS) on the spinnability, morphology, and productivity of polycaprolactone (PCL) electrospun nanofibrous scaffolds (ENS). Besides this, cellular activity on various PCL ENS is also evaluated. Herein, formic acid (F), formic acid/acetic acid (FA), and formic acid/ acetic acid/acetone (FAA) solvent systems are used to prepare various concentrations of PCL solutions. Preliminary polymeresolvent interaction studies confirm that FAA is the better solvent choice for PCL than FA and F. FAA-PCL exhibits higher viscosity than FA-PCL and F-PCL due to better polymeresolvent interactions and PCL stability. Consequently, FAA-PCL shows higher electrospun nanofiber productivity at 32 kV RMS (12.4 ± 0.3 g/h), followed by FA-PCL (6.9 ± 0.1 g/h) and F-PCL (2.2 ± 0.2 g/h). Finally, the cytotoxicity and in vitro experiments indicate that the fabricated ENS are noncytotoxic and biocompatible with 3T3-L1 mouse fibroblast cells. This study will inspire the academic and industrial communities to fabricate various polymeric nanofibers on a large scale using AC electrospinning technique.

Composite nanofibrous yarns (CNY), featuring a submicron electrospun sheath coated on a micro-scale core yarn have gained attention within the academic and industrial communities due to their unique structure. When braided, these CNYs hold great promise as next-generation surgical yarns. However, large-scale production of CNYs using conventional electrospinning techniques remains technologically challenging, and maintaining the integrity of the fibrous sheath during braiding presents further difficulties. Here, we propose a novel approach for continuously fabricating functional braided CNYs using collectorless alternating current (AC) electrospinning and braiding technology. Our approach utilized polycaprolactone-polylactic acid (PCL-PLA) blends and PCL-PLA with chlorhexidine (CHX) or triclosan (TRC) electrospun fibers for the sheath layer, while PLA micro-yarns acted as the core layer. Morphological analyses confirmed the successful fabrication of braided CNYs. Additionally, infrared spectroscopy validated the presence of CHX or TRC in the resulting yarns. The resulting braided CNYs exhibited excellent breaking force (29 N) and thermal stability (270 • C). Cytotoxicity and antibacterial assessments demonstrated that CHX-loaded braided CNYs could serve as biocompatible antibacterial surgical sutures. The proposed method offers a versatile approach for producing various functional braided CNYs applicable in tissue engineering scaffolds, filters, wearable electronics, and sensors.