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Magnetically actuable polymer nanocomposites for bioengineering applications

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Abstract

Methods are presented for creating biocompatible composites with magnetic functionality by incorporating magnetic nanoparticles in a biodegradable polymer matrix. A wide range of volume fractions for magnetic particle loading and therefore magnetization density are achievable. The nanoscale of the particles aids in achieving dispersion, so that variations in physical and chemical properties occur on scales much less than that of cells. Sufficient magnetization is achieved to enable actuation of the material, i.e., the generation of strains of biologically significant magnitudes using remotely applied magnetic fields. The magnitude of the actuation is demonstrated to enable fluid pumping and create local strains in cell aggregates that should be sufficient to stimulate cell growth and differentiation. The composite materials can be formed into random-pore scaffold materials with controlled porosity, pore shape, and pore connectivity. They can also be shaped by pressing, rolling, or drawing and joined by thermoplastic welding, so that ordered three-dimensional scaffold structures and various shell structures, such as tubes and toroids, can be fabricated. When the composite sheets are formed into tubes, the application of a moving magnetic field induces simulated peristalsis. When intestinal cells were seeded on the composite sheets, cells remained viable and grew rapidly in vitro.

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Notes

  1. The particulate leaching protocol of porogen removal involves repeated rinses and replenishment of large volumes of water. We have evaluated this issue on a field emission high resolution SEM and found that using our porogen removal protocol, most of the porogens are removed after the first rinse, and all of the porogens are removed after the second rinse, but we typically rinse four times. The resultant porosity has never presented any problem to cell seeding. Additionally, we have prepared five micron thick sections of the scaffolds within 1 h of cell seeding and we have never noticed the presence of porogens. While the possibility exists that a minute, negligible fraction of nanosized porogens can remain encapsulated, we are highly confident that most of the porogens are removed given the large interconnectivity of the pores, relatively small volume fraction of the polymer and the fast dissolution rate of sugar in water.

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Acknowledgements

The authors are very grateful to Drs. Brian Naughton and David Clarke of the University of California, Santa Barbara, for carrying out SQUID tests and to Drs. Mark Field and Jeff Cheung for instruction on magnetism.

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Authors and Affiliations

  1. Teledyne Scientific Company, 1049 Camino Dos Rios, Thousand Oaks, CA, 91360, USA

    Julia J. Mack & Brian N. Cox

  2. Department of Bioengineering, University of California, Los Angeles, 420 Westwood Plaza, Room 7523 Boelter Hall, P.O. Box 951600, Los Angeles, CA, 90095-1600, USA

    Min Lee, James C. Y. Dunn & Benjamin W. Wu

  3. Department of Surgery, University of California, Los Angeles, 10833 Le Conte Avenue, Box 709818, Los Angeles, CA, 90095, USA

    James C. Y. Dunn

Authors
  1. Julia J. Mack
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  2. Brian N. Cox
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  3. Min Lee
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  4. James C. Y. Dunn
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  5. Benjamin W. Wu
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Correspondence to Julia J. Mack.

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Mack, J.J., Cox, B.N., Lee, M. et al. Magnetically actuable polymer nanocomposites for bioengineering applications. J Mater Sci 42, 6139–6147 (2007). https://doi.org/10.1007/s10853-006-0982-y

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  • DOI: https://doi.org/10.1007/s10853-006-0982-y

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