Low-temperature Plasma Processing of Micro- and Nanostructured Materials for Biomedical Applications
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Low-temperature Plasma Processing of Micro- and Nanostructured Materials for Biomedical Applications Masaaki Nagatsu, Roman V. Bekarevich, Alexei Balmakov, Iuliana Motrescu, Akihisa Ogino, Akiko Murakawa, and Enoch Y. Park Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan ABSTRACT We develop a plasma processing technique for modifying the surface properties of micro- and nanostructured materials for biomedical applications. We also investigate the physical and chemical roles of the plasma in modifying the surfaces of micro- and nanostructured materials such as magnetic nanoparticles (MNPs), carbon nanotubes (CNTs), nanophosphors, and biomolecules for various biomedical applications. We introduced amino groups onto the surfaces of graphite-encapsulated iron compound nanoparticles using a low-pressure Ar plasma pretreatment and ammonia plasma post-treatment followed by immobilization of biomolecules, such as dextran and N-acetyllactosamine (LacNAc). The present technique was also used to introduce amino groups onto CNT dot arrays grown on Si substrates for use in biochip sensors. INTRODUCTION Magnetic nanoparticles (MNPs) are attracting great interest due to their potential to be used in biomedical applications such as drug delivery systems, hyperthermia treatment, and enhancing the contrast of magnetic resonance imaging [1–8]. Carbon nanoparticles also have the potential to be used in these applications because they have large surface areas and can be readily functionalized, which makes them suitable for high-capacity binding of biomolecules. Applying protective shells or coatings (e.g., carbon, organic polymers, or silica) to MNPs is important to make them more compatible for biomedical applications since uncoated MNPs are susceptible to agglomeration, oxidation in air, and dissolution in acids. Graphite-encapsulated MNPs are promising materials for medical applications. Carbon or graphite layers can prevent iron nanoparticles from rapidly oxidizing and they also magnetically isolate nanoparticles from each other [9–11]. Drug delivery applications require fine and homogeneous dispersions of nanoparticles in liquid since are they are performed in vivo. However, fabricated particles typically contain elemental carbon, which is highly hydrophobic and tends to aggregate when introduced into water. Suitable surface modification could be used to enhance the dispersibility of nanoparticles so that they generate uniform and stable dispersions. To overcome the problem of particle agglomeration, we propose modifying nanoparticle surfaces by plasma processing followed by biomolecule immobilization. Plasma treatment is an effective surface modification technique. Compared to chemical modification techniques, plasma treatment has the advantages of having shorter reaction times, using nonpolluting processing, and providing a wider range of different functional groups [12], which can be used to connect and deliver therapeutic agents in biomedical applications. Of the v
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