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

  • Polymers & biopolymers
  • Published:
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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.

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Abbreviations

SF:

Silk fibroin

SFW :

Silk fibroin from silk fibrous waste

PEG:

Polyethylene glycol

CORSEDA:

Corporación para el Desarrollo de la Sericultura del Cauca, Colombia

FTIR-ATR:

Attenuated total reflectance Fourier transform infrared spectroscopy

MeOH:

Methanol

SEM:

Scanning electron microscopy

DSC:

Differential scanning calorimetric

HFIP:

Hexafluoro-2-propanol

UntreatedP:

Concentrated in PEG, no post-treatment

VMeOH1hP:

Concentrated in PEG and treated with saturated MeOH atmosphere

IMeOH1hP:

Concentrated in PEG and treated by immersion in MeOH

UntreatedL:

Freeze-dried, resolubilized, no post-treatment

VMEOH1hL:

Freeze-dried, resolubilized, and treated with saturated MeOH atmosphere

IMeOH1hL:

Freeze-dried, resolubilized, and treated by immersion in MeOH

T g :

Glass transition temperature

T recryst :

Recrystallization temperature

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Acknowledgements

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

This research received fundings from: Ministerio de Ciencia, Tecnología e Innovación (MINCIENCIAS) research project: Implantes Vasculares, Cod: 121080762864, The USDA National Institute of Food and Agriculture, Hatch program (ALA013-17003), and McIntire-Stennis program (1022526).

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All authors listed have made substantial, direct, and intellectual contribution to the work and approved it for publication. Melissa Puerta developed the materials and performed the experiments and the characterizations. Melissa Puerta, Maria S. Peresin, and Adriana Restrepo-Osorio contributed to conceptualization, data analysis, and writing the manuscript.

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Correspondence to Adriana Restrepo-Osorio.

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Puerta, M., Peresin, M.S. & Restrepo-Osorio, A. Effect of processing and storage time of aqueous solutions on silk fibroin structure and methanol post-treatment of electrospun fibers. J Mater Sci 57, 3842–3854 (2022). https://doi.org/10.1007/s10853-022-06873-x

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