Surface modification of bacterial magnetic nanoparticles using artificial polypeptides consisting of a repeated asparagi
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Surface modification of bacterial magnetic nanoparticles using artificial polypeptides consisting of a repeated asparagine-serine dipeptide and a transmembrane peptide Toru Honda, Tomoko Yoshino, Tsuyoshi Tanaka, and Tadashi Matsunaga Institute of Engineering, Tokyo University of Agriculture and Technology, 2-24-16, Nakacho, Koganei, 184-8588, Japan ABSTRACT Surface modification is an important part of fabricating nanoparticles with specific properties and functions. We have designed a dipeptide, which we call NS polypeptide, that consists of four asparagine (N) residues and one serine (S) residue, as a molecule for nanoparticle surface modification. Surface modification of magnetic nanoparticles with the NS polypeptide results in reduction of particle-particle and particle-cell interactions. Here, we describe the surface modification and functionalization of bacterial magnetic particles (BacMPs) by spontaneous integration of temporin L conjugated to NS polypeptide. BacMP membranes were modified temporin L. Furthermore, peptide-modified BacMPs showed high dispersibility in aqueous solution compared to unmodified BacMPs. This surface modification technique may represent a new strategy for reducing non-specific binding of nanoparticles to proteins or cells for use in a variety of protein- or cell-associated applications. INTRODUCTION Currently, nanoparticles are key elements in the development of a variety of cell-associated applications, including techniques for cell separation, in vivo/in vitro imaging, and drug or gene delivery [1-3]. Nanoparticles have a high surface area to volume ratio, and the functions and properties of nanoparticles can be controlled by surface modification with various molecules. To develop superior nanoparticles for specific applications, appropriate surface modification of the nanoparticles is necessary. Previous reports have shown independently that the hydrophilicity and neutral charge of the nanoparticle surface are important for reducing nonspecific interactions between nanoparticles and the cell surface [4, 5]. In many case, polyethylene glycol (PEG), which is a polar and uncharged molecule, has been used [6, 7]. PEG attached to the surface of nanoparticles serves as a steric barrier and reduces nonspecific interactions between nanoparticles and cells. We previously designed a hydrophilic dipeptide composed of multiple units including four asparagine (N) residues and one serine (S) residue to reduce particle-particle and particle-cell interactions. We named this peptide the NS polypepeptide [8]. This designed polypeptide showed potential as a new strategy for the surface modification of nanoparticles. Magnetospirillum magneticum AMB-1, a magnetotactic bacterium, synthesizes intracellular nanosized bacterial magnetic particles (BacMPs) that are 50 to 100 nm in diameter. These particles are surrounded by a lipid bilayer membrane, possess a single magnetic domain of magnetite, and exhibit strong ferrimagnetism [9, 10]. Functional proteins have been displayed on BacMP surfaces through gen
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