TECHNICAL NOTE Fabrication of semiconductor nanowires by conjugation of quantum dots to actin filaments Lan Yao & Gregory O. Andreev & Yana K. Reshetnyak & Oleg A. Andreev Received: 11 June 2009 / Revised: 13 August 2009 / Accepted: 17 August 2009 / Published online: 3 September 2009 # Springer-Verlag 2009 Abstract We demonstrate the feasibility of fabrication of semiconducting nanowires (quantum dots) using F-actin as a template. Three different approaches of assembling quantum dots into nanowires are described. The nanowires were characterized by fluorescence microscopy. Keywords Nanowires . Fabrication . Quantum dots . Fluorescence Introduction The semiconductor and metallic nanowires could be used in nanoscale electronic devices. However, nanowires fabrica- tion is still a significant challenge. Very promising strategy is based on application of self-assembling biomolecules as templates due to the high degree of their organization, naturally occurring self-assembling motifs, and straightfor- ward processes of chemical modifications. Silver [1], palladium [2], gold [3], and copper [4] have been deposited on DNA templates to fabricate metal nanowires. Mao and coworkers [5] had reported a virus-based scaffold for the synthesis of semiconducting nanowires. Other approaches involve deposition of metals on protein fibrils [6,7]. Recently, actin filaments were used to build gold nanowires [8]. Actin monomers were labeled with gold nanoparticles and polymerized to form nanowires. Actin is one of the key proteins involved in muscle contraction, cell division, and migration. It is a globular protein with molecular weight of 42 kDa and diameter of 5 nm. In presence of salts and magnesium, it polymerizes into long filament with two helically twisted strands. The length of actin filament could reach 20μm, while the thickness is about 10 nm (size of two actin monomers). Here, we used filamentous actin (F-actin) as a template for the assembling of water-soluble semiconductor nano- crystals (or quantum dots (QDs)) into nanowires. QDs exhibit high photostability and bright, narrow, and tunable fluorescence at a broad band of excitation wavelengths [9,10]. Therefore, they are widely used in fluorescence spectroscopy and microscopy. The unique electronic and optical properties of QDs, together with the advances in synthesis and biofunctionalization of QDs, provide the potential applications of QD nanowires in the areas of electro-optical and biomolecular devices. Materials and methods Materials The water-soluble coated with PEG-amine (polyethylene glycol containing NH 2 group) quantum dots: Qdot®525, Qdot®605, Qdot®655, Qdot®705, Qdot®800, and Qdots®655-phalloidin were purchased from Invitrogen, Inc. The concentrations of QDs stock solutions were provided by manufacturer. Actin was obtained from Cytoskeleton, Inc. N-hydroxysuccinimide (NHS), 1-ethyl- 3-[3-dimethylaminopropyl] carbodiimide hydrochloride (EDC) and N-[g-maleimidobutyryloxy]sulfosuccinimide L. Yao : Y. K. Reshetnyak : O. A. Andreev (*) Physics Department, University of Rhode Island, 2 Lippitt Rd, Kingston, RI 02881, USA e-mail: andreev@mail.uri.edu G. O. Andreev Physics Department, University of California San Diego, 9500 Gilman Dr. #0319, La Jolla, CA 92093, USA Anal Bioanal Chem (2009) 395:1563–1566 DOI 10.1007/s00216-009-3077-1