Automated Methods to Determine Electrospun Fiber Alignment and Diameter Using the Radon Transform

Abstract

Recent evidence demonstrates the ability to change cell function by altering the physical properties of electrospun scaffolds, but many studies still do not characterize electrospun fiber alignment and diameter. To aid in the reporting of these crucial properties, we demonstrate two methods of quantifying electrospun fiber alignment with one method capable of determining electrospun fiber diameter. The first method assesses fiber alignment in a scanning electron microscopy image using the Radon Transform (RT) to calculate the entropy of the fibers in the image. The RT entropy method was more sensitive than a commonly used Fast Fourier Transform (FFT) method because the RT method was able to assess smaller changes in alignment (±2°) than the FFT (±4°, p < 0.05). The second method used the RT to detect both fiber diameter and fiber alignment by recognition of fiber edges. The RT edge method was more capable of identifying electrospun fiber alignment and diameter than a manual method using ImageJ because the ImageJ results were statistically different from information contained in images with defined alignment and diameter (p < 0.05) while the RT method showed no differences. However, the RT edge method of assessing fiber diameter was limited by the magnification of the image and was only capable of detecting fibers larger than four pixels in diameter. The RT edge method was more sensitive in differentiating between fiber scaffolds of different alignment than the entropy method since the RT edge method differentiated between all fiber alignment groups (p < 0.05) while the RT entropy method was less capable at high degrees of misalignment (> ± 8°). The RT is introduced as a sensitive tool for assessing electrospun fiber alignment, but more importantly, we have demonstrated for the first time an automated method of determining electrospun fiber diameter.

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References

  1. 1.

    Sill, T. J., & von Recum, H. A. (2008). Electrospinning: applications in drug delivery and tissue engineering. Biomaterials, 29, 1989–2006.

    Article  Google Scholar 

  2. 2.

    Lee, Y.-S., & Livingston, A. T. (2011). Electrospun nanofibrous materials for neural tissue engineering. Polymers, 3, 413–426.

    Article  Google Scholar 

  3. 3.

    Fong, H., Liu, W., Wang, C.-S., Vaia, R. A. (2002). Generation of electrospun fibers of nylon 6 and nylon 6-montmorillonite nanocomposite. Polymer, 43, 775–780.

    Article  Google Scholar 

  4. 4.

    Subramanian, A., Krishnan, U. M., Sethuraman, S. (2011). Fabrication of uniaxially aligned 3D electrospun scaffolds for neural regeneration. Biomedical Materials, 6, 025004.

    Article  Google Scholar 

  5. 5.

    Fennessey, S. F., & Farris, R. J. (2004). Fabrication of aligned and molecularly oriented electrospun polyacrylonitrile nanofibers and the mechanical behavior of their twisted yarns. Polymer, 45, 4217–4225.

    Article  Google Scholar 

  6. 6.

    Matthews, J. A., Wnek, G. E., Simpson, D. G., Bowlin, G. L. (2002). Electrospinning of collagen nanofibers. Biomacromolecules, 3, 232–238.

    Article  Google Scholar 

  7. 7.

    Liu, Y., Franco, A., Huang, L., Gersappe, D., Clark, R. A. F., Rafailovich, M. H. (2009). Control of cell migration in two and three dimensions using substrate morphology. Experimental Cell Research, 315, 2544–2557.

    Article  Google Scholar 

  8. 8.

    Johnson, J., Nowicki, M. O., Lee, C. H., Chiocca, E. A., Viapiano, M. S., Lawler, S. E., et al. (2009). Quantitative analysis of complex glioma cell migration on electrospun polycaprolactone using time-lapse microscopy. Tissue Engineering Part C Methods, 15, 531–540.

    Article  Google Scholar 

  9. 9.

    Wang, H. B., Mullins, M. E., Cregg, J. M., Hurtado, A., Oudega, M., Trombley, M. T., et al. (2009). Creation of highly aligned electrospun poly-l-lactic acid fibers for nerve regeneration applications. Journal of Neural Engineering, 6, 016001.

    Article  Google Scholar 

  10. 10.

    Corey, J. M., Lin, D. Y., Mycek, K. B., Chen, Q., Samuel, S., Feldman, E. L., et al. (2007). Aligned electrospun nanofibers specify the direction of dorsal root ganglia neurite growth. Journal of Biomedical Materials Research Part A, 83A, 636–645.

    Article  Google Scholar 

  11. 11.

    Yang, F., Murugan, R., Wang, S., Ramakrishna, S. (2005). Electrospinning of nano/micro scale poly(l-lactic acid) aligned fibers and their potential in neural tissue engineering. Biomaterials, 26, 2603–2610.

    Article  Google Scholar 

  12. 12.

    Saino, E., Focarete, M. L., Gualandi, C., Emanuele, E., Cornaglia, A. I., Imbriani, M., et al. (2011). Effect of electrospun fiber diameter and alignment on macrophage activation and secretion of proinflammatory cytokines and chemokines. Biomacromolecules, 12, 1900–1911.

    Article  Google Scholar 

  13. 13.

    Bashur, C. A., Shaffer, R. D., Dahlgren, L. A., Guelcher, S. A., Goldstein, A. S. (2009). Effect of fiber diameter and alignment of electrospun polyurethane meshes on mesenchymal progenitor cells. Tissue Engineering Part A, 15, 2435–2445.

    Article  Google Scholar 

  14. 14.

    Deitzel, J., Kleinmeyer, J., Harris, D., Beck, T. N. (2001). The effect of processing variables on the morphology of electrospun nanofibers and textiles. Polymer, 42, 261–272.

    Article  Google Scholar 

  15. 15.

    Baker, S. C., Atkin, N., Gunning, P. A., Granville, N., Wilson, K., Wilson, D., et al. (2006). Characterisation of electrospun polystyrene scaffolds for three-dimensional in vitro biological studies. Biomaterials, 27, 3136–3146.

    Article  Google Scholar 

  16. 16.

    Meechaisue, C., Dubin, R., Supaphol, P., Hoven, V. P., Kohn, J. (2006). Electrospun mat of tyrosine-derived polycarbonate fibers for potential use as tissue scaffolding material. Journal of Biomaterials Science Polymer Edition, 17, 1039–1056.

    Article  Google Scholar 

  17. 17.

    Shih, Y. V., Chen, C., Tsai, S., Wang, Y. J., Lee, O. K. (2006). Growth of mesenchymal stem cells on electrospun type I collagen nanofibers. Stem Cells, 24, 2391–2397.

    Article  Google Scholar 

  18. 18.

    Wang, H. B., Mullins, M. E., Cregg, J. M., McCarthy, C. W., Gilbert, R. J. (2010). Varying the diameter of aligned electrospun fibers alters neurite outgrowth and Schwann cell migration. Acta Biomaterialia, 6, 2970–2978.

    Article  Google Scholar 

  19. 19.

    Christopherson, G. T., Song, H., Mao, H.-Q. (2009). The influence of fiber diameter of electrospun substrates on neural stem cell differentiation and proliferation. Biomaterials, 30, 556–564.

    Article  Google Scholar 

  20. 20.

    Badami, A. S., Kreke, M. R., Thompson, M. S., Riffle, J. S., Goldstein, A. S. (2006). Effect of fiber diameter on spreading, proliferation, and differentiation of osteoblastic cells on electrospun poly(lactic acid) substrates. Biomaterials, 27, 596–606.

    Article  Google Scholar 

  21. 21.

    He, L., Liao, S., Quan, D., Ma, K., Chan, C., Ramakrishna, S., et al. (2010). Synergistic effects of electrospun PLLA fiber dimension and pattern on neonatal mouse cerebellum C17.2 stem cells. Acta Biomaterialia, 6, 2960–2969.

    Article  Google Scholar 

  22. 22.

    Ayres, C., Bowlin, G. L., Henderson, S. C., Taylor, L., Shultz, J., Alexander, J., et al. (2006). Modulation of anisotropy in electrospun tissue-engineering scaffolds: analysis of fiber alignment by the fast Fourier transform. Biomaterials, 27, 5524–5534.

    Article  Google Scholar 

  23. 23.

    Murphy, L. M. (1986). Linear feature detection and enhancement in noisy images via the Radon transform. Pattern Recognition Letters, 4, 279–284.

    Article  Google Scholar 

  24. 24.

    Grangeat, P. (2010). Tomography. Hoboken, NJ: John Wiley & Sons.

  25. 25.

    Schaub, N. J., Gilbert, R. J., Kirkpatrick, S. J. (2011). Electrospun fiber alignment using the radon transform. Proceedings of SPIE; 7897D.

  26. 26.

    Ayres, C. E., Jha, B. S., Meredith, H., Bowman, J. R., Bowlin, G. L., Henderson, S. C., et al. (2008). Measuring fiber alignment in electrospun scaffolds: a user’s guide to the 2D fast Fourier transform approach. Journal of Biomaterials Science Polymer Edition, 19, 603–621.

    Article  Google Scholar 

  27. 27.

    Bracewell, R. (1956). Strip integration in radio astronomy. Australian Journal of Physics, 9, 198–217.

    MathSciNet  MATH  Article  Google Scholar 

  28. 28.

    Vartanian, K. B., Kirkpatrick, S. J., Hanson, S. R., Hinds, M. T. (2008). Endothelial cell cytoskeletal alignment independent of fluid shear stress on micropatterned surfaces. Biochemical and Biophysical Research Communications, 371, 787–792.

    Article  Google Scholar 

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Acknowledgments

This work was supported by NSF CAREER Award 1105125 to RJG.

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Correspondence to Ryan J. Gilbert.

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Schaub, N.J., Kirkpatrick, S.J. & Gilbert, R.J. Automated Methods to Determine Electrospun Fiber Alignment and Diameter Using the Radon Transform. BioNanoSci. 3, 329–342 (2013). https://doi.org/10.1007/s12668-013-0100-y

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Keywords

  • Image Analysis
  • Electrospun Fibers
  • Fourier Transform
  • RT
  • SEM (Scanning Electron Microscopy)