Delivered by Ingenta to: Editor in Chief IP : 76.184.16.229 Sat, 22 Dec 2012 17:01:46 Copyright © 2012 by American Scientific Publishers All rights reserved. Printed in the United States of America Reviews in Nanoscience and Nanotechnology Vol. 1, pp. 257–270, 2012 (www.aspbs.com/rnn) Recent Progress on the Liposomes Loaded with Quantum Dots Chang Yang 1, 2 , Wei Chen 2 , Brian Quang Bui 2 , and Guangya Xiang 1, 3, * 1 School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China 2 Department of Physics, The University of Texas at Arlington, Arlington, TX 76019-0059, USA 3 Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, Tongji Medical College, Huazhong University of Science and Techonology, Wuhan 430030, China Quantum dots (QDs), semiconductor nanocrystals, are recognized as one of the most promising nanostructures for in vitro diagnostic applications. They are considered to be ideal candidates as fluorescent probes for long-term imaging to track whole cells or intracellular biomolecules due to their bright fluorescence, narrow emission, broad excitation, and high photostability. In the process of improving the performance of QDs, liposomes have been dramatically exploited. Hydrophobic QDs using liposome as a carrier can solve the problem of biocompatibility, while hydrophilic QDs entrapped in the liposomes can reduce the cytotoxicity. Additionally, an active targeting agent linked with the lipid materials can largely increase the targeting abil- ity of liposomes to tumor cells, such as anti-HER protein, EGF ligand, folate, and platelet derived growth factor (PDGF). The incorporation of QDs into liposomes can greatly enhance the uptake of living cells. The liposomes loaded with QDs are mainly distributed in the tumor, liver and spleen. They can be cleared by the mononuclear phagocyte system (MPS). Multifunctional liposomes loaded with QDs are developed, such as multi-fluorescent liposomes, fluorescent paramagnetic liposomes and theranostic liposomes, as a result, the development of personalized medicines are largely promoted. In summary, this review mainly introduces some developments with respect to the improvement of biocompatibility, cytotoxicity, and specificity of lipo- somes loaded with QDs, their intracellular transportation and the application of multifunctional QDs conjugated liposomes. KEYWORDS: Quantum Dots, Biocompatibility, Cytotoxicity, Liposome, Multifunctional Liposome, Intracellular Trafficking, Targeting, Theranostic Liposomes. CONTENTS 1. Introduction ................................. 257 2. Liposomes .................................. 259 3. Quantum Dots ............................... 260 4. Hydrophobic QDs Entrapped in a Liposome ............ 261 5. Liposomes Encapsulating Hydrophilic QDs ............. 262 6. Intracellular Trafficking and In Vivo Distribution of QDs Loaded Liposomes ............... 262 7. Targetting of Liposomes Loaded with QDs ............. 262 8. Multifunctional QD-Conjugated Liposomes ............. 264 9. Conclusion ................................. 267 Acknowledgments ............................. 267 References and Notes ........................... 267 ∗ Author to whom correspondence should be addressed. Email: gyxiang1968@hotmail.com Received: 6 August 2011 Accepted: 8 April 2012 1. INTRODUCTION Fluorescent probes play an important role in the bio- logical detection and bio-imaging due to its superior sensitivity, brightness, higher resolution, chemical identi- fication, faster detection and the possibility of color-coded multiplexing. 1–2 Conventional fluorescence technology is based on organic fluorophores, called organic dyes. The majority of common organic dyes are characterized by slightly structured, comparatively narrow absorption and emission bands, a small solvent polarity-insensitive Stokes shift, high molar absorption coefficients, and moderate- to-high fluorescence quantum yields. 3 Despite the advan- tages resulted from the established labeling protocols and developed fluorescence techniques, the broad absorption/ emission profiles and poor photostability still limit their effectiveness in extended-time imaging and the Rev. Nanosci. Nanotechnol. 2012, Vol. 1, No. 4 2157-9369/2012/1/257/014 doi:10.1166/rnn.2012.1017 257