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Letter

Biodegradable Quantum Dot Nanocomposites Enable Live Cell Labeling and Imaging of Cytoplasmic Targets

Supporting Info

Betty Y. S. Kim^†^‡^§, Wen Jiang^†^‡, John Oreopoulos^†^‡, Christopher M. Yip^†^‡, James T. Rutka^§ and Warren C. W. Chan*^†^‡

Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, Ontario M5S 3G9, Canada, Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, Ontario M5S 3E1, Canada, and Division of Neurosurgery, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada

Nano Lett., 2008, 8 (11), pp 3887–3892

DOI: 10.1021/nl802311t

Publication Date (Web): September 25, 2008

†

Institute of Biomaterials and Biomedical Engineering.

‡

Terrence Donnelly Centre for Cellular and Biomolecular Research.

Division of Neurosurgery, The Hospital for Sick Children.

Co-first authors.

* To whom correspondence should be addressed. E-mail: warren.chan@utoronto.ca.

Abstract

Semiconductor quantum dots (QDs) offer great promise as the new generation of fluorescent probes to image and study biological processes. Despite their superior optical properties, QDs for live cell monitoring and tracking of cytoplasmic processes remain limited due to inefficient delivery methods available, altered state or function of cells during the delivery process and the requirement of surface-functionalized QDs for specific labeling of subcellular structures. Here, we present a noninvasive method to image subcellular structures in live cells using bioconjugated QD nanocomposites. By incorporating antibody-coated QDs within biodegradable polymeric nanospheres, we have designed a bioresponsive delivery system that undergoes endolysosomal to cytosolic translocation via pH-dependent reversal of nanocomposite surface charge polarity. Upon entering the cytosol, the polymer nanospheres undergo hydrolysis thus releasing the QD bioconjugates. This approach facilitates multiplexed labeling of subcellular structures inside live cells without the requirement of cell fixation or membrane permeabilization. As compared to conventional intracellular delivery techniques, this approach allows the high throughput cytoplasmic delivery of QDs with minimal toxicity to the cell. More importantly, this development demonstrates an important rational strategy for the design of a multifunctional nanosystem for biological applications.

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