pubs.acs.org/Langmuir © 2010 American Chemical Society
Patterning of Quantum Dot Bioconjugates via Particle Lithography Zachary R. Taylor,† Ernest S. Sanchez,§ Joel C. Keay,§ Matthew B. Johnson,§ and David W. Schmidtke*,†,‡ †
University of Oklahoma Bioengineering Center, ‡School of Chemical, Biological, and Materials Engineering, and §Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 100 East Boyd, Norman, Oklahoma 73019, United States Received August 31, 2010. Revised Manuscript Received October 22, 2010 We present a simple technique to fabricate hexagonally ordered quantum dot bioconjugate (QDBC) dot arrays on glass coverslips. We used particle lithography to create periodic holes in a layer of methoxy-poly(ethylene glycol)-silane and then adsorbed QDBCs into the holes. To demonstrate the versatility of this technique, we made separate periodic arrays of quantum dots (QDs) conjugated to three different biologically important molecules: biotin, streptavidin, and anti-mouse IgG. The diameters of the regions where the QDBCs adsorbed were 500-600 nm and independent of the QDBC patterned. The site density of the QDBCs in the patterned holes could be varied by simply adjusting the coating concentration of the QDBC solution. We demonstrate the applicability of these substrates by designing a QDBC-based binding assay with a working concentration range of several orders of magnitude and a sub-picomolar detection limit.
Introduction Due to their unique fluorescent properties, semiconductor quantum dots (QDs) have been utilized in the development of novel light emitting devices,1 solar cells,2 biological imaging schemes,3-7 and biosensors for the detection of proteins,8-11 *To whom correspondence should be addressed. Telephone: (405) 3257944. Fax: (405) 325-5813. E-mail:
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18938 DOI: 10.1021/la103468u
nucleic acids,12-16 bacteria,17,18 and other chemical species.19-27 Compared to organic fluorophores, QDs exhibit both higher quantum efficiency and greater photostability. Furthermore, since their fluorescent properties are size-dependent, QDs with identical chemical compositions but different diameters can be used when multiple fluorophores are desired. For biological applications, QDs can be conjugated to a number of biomolecules including nucleic acids and proteins.28-30 These characteristics make QDs an important resource in a number of scientific fields. Recently, there has been a great deal of interest in patterning surfaces with QDs in sub-micrometer domains (Table 1). QDpatterned surfaces have potential applications in electronics, computing, data storage, molecular interaction studies, and biosensors.31 In biosensing applications, patterned surfaces present increased densification of surface recognition elements,32 availability of binding sites,33 and immobilization efficiency34 over homogeneously coated surfaces. Ultimately, these advantages lead to lower detection limits.32-34 Of the methods used to pattern QDs, particle lithography is an attractive option because it relies on simple, relatively inexpensive techniques and can be used to process several samples simultaneously. Particle lithography has previously been used to create (23) Ge, S.; Zhang, C.; Zhu, Y.; Yu, J.; Zhang, S. Analyst 2009, 135, 111–115. (24) Hu, X.; Han, H.; Hua, L.; Sheng, Z. Biosens. Bioelectron. 2010, 25, 1843– 1846. (25) Liu, J.; Bao, C.; Zhong, X.; Zhao, C.; Zhu, L. Chem. Commun. 2010, 46, 2971–2973. (26) Peng, C.; Li, Z.; Zhu, Y.; Chen, W.; Yuan, Y.; Liu, L.; Li, Q.; Xu, D.; Qiao, R.; Wang, L.; Zhu, S.; Jin, Z.; Xu, C. Biosens. Bioelectron. 2009, 24, 3657–3662. (27) Zou, Z.; Du, D.; Wang, J.; Smith, J. N.; Timchalk, C.; Li, Y.; Lin, Y. Anal. Chem. 2010, 82, 5125–5133. (28) Biju, V.; Itoh, T.; Anas, A.; Sujith, A.; Ishikawa, M. Anal. Bioanal. Chem. 2008, 391, 2469–2495. (29) Han, C.; Li, H. Anal. Bioanal. Chem. 2010, 397, 1437–1144. (30) Yu, W. W.; Chang, E.; Drezek, R.; Colvin, V. L. Biochem. Biophys. Res. Commun. 2006, 348, 781–786. (31) Yoffe, A. D. Adv. Phys. 2001, 50, 1–208. (32) Valsesia, A.; Colpo, P.; Mannelli, I.; Mornet, S.; Bretagnol, F.; Ceccone, G.; Rossi, F. Anal. Chem. 2008, 80, 1418–1424. (33) Agheli, H.; Malmstr€om, J.; Larsson, E. M.; Textor, M.; Sutherland, D. S. Nano Lett. 2006, 6, 1165–1171. (34) Lisboa, P.; Valsesia, A.; Mannelli, I.; Mornet, S.; Colpo, P.; Rossi, F. Adv. Mater. 2008, 20, 2352–2358.
Published on Web 11/12/2010
Langmuir 2010, 26(24), 18938–18944
Taylor et al.
Article Table 1. Comparison of Quantum Dot Sub-Micrometer Patterning Methodsa
pattern type
method of pattern formation
pattern size
quantum dot bioconjugate(s) patterned
dots dots (single QDs) dots/lines dots lines lines lines/wells lines/squares/cylinders
dip-pen nanolithography (DPN) 500-900 nm QD-IgG S-layer protein scaffolding 7-22 nm (spacing) dip-pen nanolithography (DPN) 230 nm/90-400 nm QD-SA; QD-IFNR2 particle Lithography 500-600 nm QD-SA; QD-B; QD-IgG microcontact Molding 160-510 nm electron-beam lithography 200 nm QD-IgG surface reconstructed block copolymers
