Effect of processing and storage time of aqueous solutions on silk fibroin structure and methanol post-treatment of electrospun fibers

Melissa Puerta, Maria S. Peresin, Adriana Restrepo-Osorio

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    Abstract

    Silk fibroin (SF) is a natural and biocompatible polymer that is obtained from silk cocoons or from silk fibrous waste. In this study, aqueous solutions of SF were obtained from silk fibrous waste (SFW) and subjected to concentration by reverse dialysis with polyethylene glycol (PEG) or freeze-drying with subsequent resolubilization prior to processing via electrospinning. The regenerated SFW was stored at 4 °C, and its stability during refrigeration was investigated in terms of structural changes using visual monitoring and attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR) until gelation occurred. The electrospun nonwovens produced through both concentration processes were post-treated using methanol (MeOH), by immersion in the liquid solvent and by exposure to a saturated atmosphere. The electrospun nonwovens before and after post-treatments were characterized using scanning electron microscopy (SEM), FTIR-ATR, and differential scanning calorimetric (DSC). SFW re-suspended after the PEG concentration remained liquid and retained its electrospinnability for 21 days, while the resolubilized SFW solution after freeze-drying formed a gel after only 7 days. During these processability windows, it was possible to obtain SFW homogeneous fibers. Increasing solution storage time was correlated with increased fiber diameter and reduced porosity of the electrospun nonwovens. The fibers treated with MeOH, both liquid and vapor, showed an increase in diameter and crystallinity, as well as a reduction in their apparent porosity. This work contributes new information about pre- and post-processing of SFW aqueous solutions for electrospun SFW nonwovens, expanding the potential of a by-product of silk production in value-added biomaterials production. Graphical abstract: [Figure not available: see fulltext.]

    Original languageEnglish
    Pages (from-to)3842-3854
    Number of pages13
    JournalJournal of Materials Science
    Volume57
    Issue number5
    DOIs
    StatePublished - Feb 2022

    Bibliographical note

    Funding Information:
    The authors express their acknowledgements to Centro de Investigación para el Desarrollo y la Innovación (CIDI) of the Universidad Pontificia Bolivariana for the financial of the advanced training scholarship for the master’s student and to Ministerio de Ciencia, Tecnología e Innovación (MINCIENCIAS) for the financial support of the research project: Implantes Vasculares, Cod: 121080762864. Additionally, the USDA National Institute of Food and Agriculture, Hatch program (ALA013-17003), and McIntire-Stennis program (1022526) are acknowledged for the support of this work.

    Funding Information:
    The authors express their acknowledgements to Centro de Investigaci?n para el Desarrollo y la Innovaci?n (CIDI) of the Universidad Pontificia Bolivariana for the financial of the advanced training scholarship for the master?s student and to Ministerio de Ciencia, Tecnolog?a e Innovaci?n (MINCIENCIAS) for the financial support of the research project: Implantes Vasculares, Cod: 121080762864. Additionally, the USDA National Institute of Food and Agriculture, Hatch program (ALA013-17003), and McIntire-Stennis program (1022526) are acknowledged for the support of this work.

    Publisher Copyright:
    © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

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