Biological Applications of Polyaniline Nanofibers

D.O. PERALTA, I.E. YSLAS, R. RIVERO, V. RIVAROLA, C.A. BARBERO

VIÑA DEL MAR CHILE

Workshop; INTERNATIONAL WORKSHOP FRONTIERS IN MATERIALS RESEARCHS III; 2006

  Polyaniline nanofibers are small objects which are suitable as multifunction vectors for insertion of bioactive principles into living cells.  Additionally, the optical properties of the fibers could be used with profit in Near Infrared (NIR) photothermal therapy and/or tomography. Since polyaniline has a broad absorption band, due to free carrier absorption, with a maximum at ca. 800 nm it absorbs in the NIR range. Living tissue absorbs little light between 700 and 1200 nm. Therefore, light in this region could penetrate several centimeters to be absorbed by a suitable susceptor, such as polyaniline. Polyaniline nanofibers can be easily synthesized by interfacial polymerization[1]. The diameter of the fibers can be controlled by changing the counterion present during polymerization in a range between 10 and 50 nm. While PANI nanofibers form a stable suspension in acid media, due to the repulsion of charges build up on the fibers by protonation, the precipitate at physiological pH, where the surface is deprotonated. To overcome that, we use a soluble polyaniline, functionalized by reaction of diazonium ion with polyaniline,[2] as a non covalent solubilizing agent.[3] To follow the intake of PANI nanofibers into the cells, the surface of the nanofiber is stained with a Dansyl fluorescent tag. Then immobilized cells (MCF-7, Human Breast Adenocarcinoma Cell Line) are incubated (3 and 6 hrs) in PBS buffer containing the dispersed nanofibers. It is found that, below a concentration threshold, PANI nanofibers are innocuous to the cells in the dark. The tagged nanofibers are easily detected inside the cytoplasm by fluorescence microscopy, indicating that are inserted into the cells. After 2 hrs, the nanofibers translocate onto the cell nucleus. The application of PANI nanofibers as multifunction vector and/or NIR photothermal therapy susceptor will be discussed. REFERENCES [1] D. Li and R. B. Kaner J. Am. Chem. Soc.; 128(2006)968 - 975 [2] D.F. Acevedo, M.C. Miras, C. A. Barbero, J.  Combin.  Chem., 7(2005)513-516. [3] D.F. Acevedo, J. Balach, C. Rivarola, M.C. Miras, C.A. Barbero, Faraday Discussions., 131(2006)352.