title: Quantum dot DNA bioconjugates: attachment chemistry strongly influences the resulting composite architecture.
abstract: The unique properties provided by hybrid semiconductor quantum dot (QD) bioconjugates continue to stimulate interest for many applications ranging from biosensing to energy harvesting. Understanding both the structure and function of these composite materials is an important component in their development. Here, we compare the architecture that results from using two common self-assembly chemistries to attach DNA to QDs. DNA modified to display either a terminal biotin or an oligohistidine peptidyl sequence was assembled to streptavidin/amphiphilic polymer- or PEG-functionalized QDs, respectively. A series of complementary acceptor dye-labeled DNA were hybridized to different positions on the DNA in each QD configuration and the separation distances between the QD donor and each dye-acceptor probed with Förster resonance energy transfer (FRET). The polyhistidine self-assembly yielded QD-DNA bioconjugates where predicted and experimental separation distances matched reasonably well. Although displaying efficient FRET, data from QD-DNA bioconjugates assembled using biotin-streptavidin chemistry did not match any predicted separation distances. Modeling based upon known QD and DNA structures along with the linkage chemistry and FRET-derived distances was used to simulate each QD-DNA structure and provide insight into the underlying architecture. Although displaying some rotational freedom, the DNA modified with the polyhistidine assembles to the QD with its structure extended out from the QD-PEG surface as predicted. In contrast, the random orientation of streptavidin on the QD surface resulted in DNA with a wide variety of possible orientations relative to the QD which cannot be controlled during assembly. These results suggest that if a particular QD biocomposite structure is desired, for example, random versus oriented, the type of bioconjugation chemistry utilized will be a key influencing factor.
authors.affiliation: Center for Bio/Molecular Science and Engineering, Code 6900, U.S. Naval Research Laboratory, Washington D.C. 20375, USA.
authors.forename: Kelly
authors.initials: K
authors.lastname: Boeneman
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Deschamps
authors.forename: Susan
authors.initials: S
authors.lastname: Buckhout-White
authors.forename: Duane E
authors.initials: DE
authors.lastname: Prasuhn
authors.forename: Juan B
authors.initials: JB
authors.lastname: Blanco-Canosa
authors.forename: Philip E
authors.initials: PE
authors.lastname: Dawson
authors.forename: Michael H
authors.initials: MH
authors.lastname: Stewart
authors.forename: Kimihiro
authors.initials: K
authors.lastname: Susumu
authors.forename: Ellen R
authors.initials: ER
authors.lastname: Goldman
authors.forename: Mario
authors.initials: M
authors.lastname: Ancona
authors.forename: Igor L
authors.initials: IL
authors.lastname: Medintz
mesh_terms: D001483:Base Sequence; D001710:Biotin / Q000378:metabolism; D004247:DNA / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000737:chemistry; D006639:Histidine / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D053761:Nanocomposites / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D045663:Quantum Dots; D019809:Streptavidin / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D010446:Peptide Fragments; D011092:Polyethylene Glycols; D006639:Histidine; D001710:Biotin; D004247:DNA; D019809:Streptavidin