Abstract
Mats of polyvinyl alcohol (PVA) core–shell nanofibers were produced using coaxial electrospinning in the presence of a thiosemicarbazone (TSC) N4-(S)-1-phenylethyl)-2-(pyridin-2-yl-ethylidene)hydrazine-1-carbothioamide (HapyTSCmB). Monolithic fibers with 0% or 5% TSC and core–shell fibers with 10% TSC in the spinning solution were studied to compare stability and release rates. SEM showed the formation of uniform, bead-free, cylindrical, and smooth fibers. NMR spectroscopy and thermal analysis (TG/DTA) gave proof for the chemical integrity of the TSC in the fiber mats after the electrospinning process. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy showed no TSC on the surface of the PVA/TSC-PVA fibers confirming the core–shell character. The TSC release profiles of the fibers as studied using UV-vis absorption spectroscopy showed a slower release from the PVA/TSC-PVA core–shell structure compared with the monolithic PVA/TSC fibers as well as lower cumulative release percentage (17%). Out of several release models, the Korsmeyer–Peppas model gave the best fit to the experimental data. The main release phase can be described with a Fick-type diffusion mechanism. Antibacterial properties were tested against the Gram-positive Staphylococcus aureus bacterium and gave a minimal inhibitory concentration of 12.5 μg/mL. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazoliumbromide (MTT)-based cytotoxicity experiments showed that the cell viability of fibroblast at different contents of TSC was slightly decreased from 1.5% up to 3.5% when compared to control cells.
Highlights
Thiosemicarbazones (TSCs) and their metal complexes are versatile molecules with a wide spectrum of antimicrobial, antitrypanosomal, antitumor, antimalarial, and antiviral activities and have been studied intensely in pharmaceutical and medicinal chemistry [1,2,3,4,5,6,7,8,9,10,11,12,13]
4 g of N4-(S)-1-phenylethyl)-2-(pyridin-2-yl-ethylidene)hydrazine-1-carbothioamide (HapyTSCmB) was synthesized from 1-(pyridin-2-yl)ethan-1-one and (S)-N4-(1-phenylethyl)hydrazinecarbothioamide in a process derived from an established ultra-sonic assisted condensation method by Carradori et al [11] (Scheme 1) in 74% yield
Nuclear magnetic resonance (NMR) spectroscopy on pieces of the fiber mats dissolved in DMSO-d6 were recorded at room temperature on a Bruker Avance II AV300 (300 MHz), using a triple resonance
Summary
Thiosemicarbazones (TSCs) and their metal complexes are versatile molecules with a wide spectrum of antimicrobial, antitrypanosomal, antitumor, antimalarial, and antiviral activities and have been studied intensely in pharmaceutical and medicinal chemistry [1,2,3,4,5,6,7,8,9,10,11,12,13]. TSCs are able to block the genetic expression of wide variety of viruses [11,13], including the herpes simplex virus [14,15,16,17,18,19,20,21] This virus affects the external genitalia, anal region, mucosal surfaces, and skin in other parts of the body, and external treatment is possible. This brought us to the idea to incorporate a TSC into fibrous mats to be used for treating herpes simplex infections.
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