2D-COS Raman Technique Reveals Biocompatibility of Carbon Nanofibers

Exploring the intricate structures of carbon nanofibers ©A.Rod - stock.adobe.com

In the realm of nanotechnology, carbon nanofibers (CNFs) are gaining prominence due to their potential applications across various industries, including energy storage, catalysis, and biomedicine. Researchers from Jagiellonian University and AGH University of Science and Technology in Kraków, Poland, have leveraged a cutting-edge analytical technique—two-dimensional correlation spectroscopy (2D-COS)—to assess the biocompatibility of CNFs. Their recent publication in the journal Applied Spectroscopy presents an advanced approach to evaluating these nanomaterials, which could have significant implications for their use in medical technologies (1).

Read More: 2D-COS Spectroscopy

The study, led by Aleksandra Wesełucha-Birczyńska, Elżbieta Długoń, Krzysztof Morajkaa, and Marta Błażewicz, investigated the properties of CNFs synthesized from polyacrylonitrile (PAN) fibers through a carbonization process at 1000 °C. This process produced two types of CNFs: electrospun carbon nanofibers (ESCNFs) and functionalized ESCNFs (ESCNF-f). The primary goal was to compare their biocompatibility and structural characteristics (1).

ESCNFs, produced without additional treatment, were found to be cytotoxic. This was evidenced by significant DNA damage and increased cell mortality in human skin fibroblasts exposed to these fibers. Conversely, ESCNF-f underwent an oxidation treatment to modify its surface, which enhanced its biocompatibility. These treated fibers showed reduced genotoxicity and better cell survival, indicating their potential for safer medical applications (1).

To elucidate the differences between the two CNF types, the researchers employed multiwavelength Raman microspectroscopy and 2D-COS. Raman spectroscopy, using a Renishaw InVia spectrometer with various laser lines (785 nm, 514.5 nm, and 442 nm), provided detailed spectral data. The D and G bands in the Raman spectra were analyzed to assess the carbon structure and disorder within the CNFs (1).

Raman Microspectroscopy and 2D-COS Analysis

The Raman spectroscopy results alone were not sufficient to clearly differentiate between the two CNF types. Therefore, the team applied 2D-COS, which treats variations in laser excitation as perturbations to enhance the resolution of structural differences. This advanced analytical technique revealed that the ESCNF-f had a more ordered structure resembling graphite, whereas the ESCNFs exhibited greater disorder (1).

The 2D-COS analysis involved preprocessing the spectral data, smoothing, baseline correction, and normalization using Renishaw’s WiRE software. The Generalized 2D correlation analysis, based on Noda’s methods (2,3), allowed the researchers to visualize how different laser energies influenced the CNFs. The resulting spectra indicated that ESCNF-f had distinct, less disordered phases compared to the ESCNFs, highlighting the effectiveness of the chemical modification process in improving the material's biocompatibility (1).

Genotoxicity and Biocompatibility

The study also included genotoxicity tests conducted on human skin fibroblasts from the CCL-110 cell line. The ESCNFs caused substantial DNA damage and higher cell mortality compared to control samples, emphasizing its cytotoxic nature. In contrast, ESCNF-f exhibited significantly lower genotoxicity and fewer dead cells, confirming its superior biocompatibility (1).

This research underscores the importance of surface modification in enhancing the safety of CNFs. The functionalization process not only reduced the toxic phases present in the ESCNFs but also improved the overall structural order of the fibers. This improvement in order is correlated with the removal of harmful phases, making the functionalized CNFs more suitable for biological applications (1).

Conclusion

The study illustrates the value of two-dimensional correlation spectroscopy in evaluating the safety and biocompatibility of nanomaterials. By distinguishing between toxic and non-toxic carbon nanofibers, 2D-COS offers a powerful tool for ensuring that nanomaterials meet safety standards for medical use. The findings provide a foundation for future research and development of CNFs, potentially leading to safer and more effective applications in biomedical technologies (1).

References

(1) Wesełucha-Birczyńska A.; Długoń E.; Morajka K.; Błażewicz M. Can Two-Dimensional Correlation Spectroscopy (2D-COS) Indicate Biocompatible Material? Appl. Spectrosc. 2024, 0 (0). DOI:10.1177/00037028241268223

(2) Noda, I., Dowrey, A. E.; Marcott, C.; Story, G .M.; Ozaki, Y. Generalized two-dimensional correlation spectroscopy. Appl. Spectrosc. 2000, 54 (7), 236A–248A. DOI: 10.1366/0003702001950454

(3) Noda, I. and Ozaki, Y. Two-dimensional correlation spectroscopy: applications in vibrational and optical spectroscopy; John Wiley & Sons, 2004. https://onlinelibrary.wiley.com/doi/book/10.1002/0470012404 (accessed 2024-08-13).