Introduction:: The study of cellulose nanofibrils (CNF) as a novel material has been heavily researched at the University of Maine. CNF has desirable properties, such as sustainability, biodegradability, and biocompatibility which make it a candidate material for new investment for biomedical research.1 CNF has specific geometric and surface properties making it chemically and mechanically versatile. It is hydrophilic, possesses high mechanical strength, and has moderate porosity in bulk. Based on these properties, the Mason Lab has extensively explored the potential application of dense CNF-based solid composites for use in healthcare-related applications ranging from disposable surgical tools to resorbable implants. Despite much progress, there remain several key unknowns that must first be addressed. One specific challenge is understanding and controlling the rehydration and degradation of this material system under biological conditions.
Materials and Methods:: Chemical cross-linking is a standard method employed in polymer chemistry that may alleviate some of these property drawbacks. One such promising cross-linking agent, Polycup (polyamide-epichlorohydrin - PAE), is widely used in industry, and is currently being explored as part of this project. It is unknown if the required mechanical properties can be achieved while maintaining the biosafety required for the targeted healthcare applications.3
For this project, there will essentially be three major aims: 1) the production of a series of bulk test materials where the loading of PAE and the thermal cross-linking activation energy (time x temp) have been systematically varied, 2) cut the as-produced materials to American Society for Testing and Materials (ASTM) shapes and sizes and obtain mechanical data (tensile, flexure, compression), and 3) perform FDA compliant ISO tissue culture biocompatibility assay on selected candidate materials using MC3T3-E1 osteoblasts.
Results, Conclusions, and Discussions:: Previous results have shown that the use of PAE as a cross-linking agent have proved to be promising. One test showed that the overall water absorption of CNF decreased over time when crosslinked with PAE. The previous test also showed that there was a larger number of pores when crosslinking occurred, but the overall pore volume was decreased. Moving forward, our lab will continue to work with PAE as a crosslinking additive, along with other mineral composites combined.
Acknowledgements (Optional): : The author would like to thank Dr. Mitchell Chesley and Dr. Michael Mason for their inspiration and mentorship of this project. I would also like to thank everybody in the Mason Lab for their constant support and collaboration.
References (Optional): : 1. Jorfi, M. & Foster, E. J. Recent advances in nanocellulose for biomedical applications. Journal of Applied Polymer Science vol. 132 Preprint at https://doi.org/10.1002/app.41719 (2015).
2. Effect of Chemical Crosslinking on Properties of Polymer Microbeads: A Review. Can Chem Trans 473–485 (2016) doi:10.13179/canchemtrans.2015.03.04.0245.
3. Sharma, S. & Deng, Y. Dual mechanism of dry strength improvement of cellulose nanofibril films by polyamide-epichlorohydrin resin cross-linking. Ind Eng Chem Res 55, 11467–11474 (2016).
