1. ¹Department of Pharmaceutical Sciences, University of Connecticut, 69 North Eagleville Road, Unit 3092, Storrs, CT 06269, USA
2. ²Nanomaterials Optoelectronics Lab, Polymer Program, Department of Chemistry, Institute of Materials Science, University of Connecticut, 97 North Eagleville Road, Unit 3136, Storrs, CT 06269, USA
3. ³Department of Animal Science, Center of Excellence for Vaccine Research, University of Connecticut, 1390 Storrs Road, Unit 4163, Storrs, CT 06269, USA

Correspondence: Diane J. Burgess, Fax: +1 860 486 0538. E-mail: d.burgess@uconn.edu

Received 14 September 2005; Revised 7 March 2006; Accepted 10 March 2006.

Abstract

Semiconductor nanocrystal quantum dots (QDs) allow long-term imaging in the cellular environment with high photostability. QD biolabeling techniques have previously been developed for tagging proteins and peptides as well as oligonucleotides. In this contribution, QD-decorated plasmid DNA was utilized for the first time for long-term intracellular and intranuclear tracking studies. Conjugation of plasmid DNA with phospholipid-coated QDs was accomplished using a peptide nucleic acid (PNA)–N-succinimidyl-3-(2-pyridylthio) propionate linker. Gel electrophoresis and confocal and atomic force microscopy (AFM) were used to confirm the structure of QD–DNA conjugates. AFM imaging also revealed that multiple QDs were attached in a cluster at the PNA-reactive site of the plasmid DNA. These QD–DNA conjugates were capable of expressing the reporter protein, enhanced green fluorescent protein, following transfection in Chinese hamster ovary (CHO-K1) cells with an efficiency of ca. 62%, which was comparable to the control (unconjugated) plasmid DNA.