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15
CONTENTS
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© 2002 by CRC Press LLC
Cell-Penetrating Peptide
Conjugations and
Magnetic Cell Labels
Ching-Hsuan Tung and Ralph Weissleder
15.1 Introduction ..................................................................................................327
15.2 Conjugation Tactics......................................................................................328
15.2.1 Direct Synthesis of CPP Conjugates ...............................................329
15.2.2 Solution Phase Conjugation.............................................................332
15.2.2.1 Amine-Reactive Reagents.................................................332
15.2.2.2 Sulfhydryl-Reactive Reagents ..........................................333
15.2.2.3 Heterobifunctional Conjugation .......................................333
15.3 Tat Peptide Delivers Magnetic Compounds into Mammalian Cells...........336
15.3.1 Cellular Internalization of Superparamagnetic Nanoparticles ........336
15.3.1.1 CLIO–Tat Is Internalized into Different Subsets
of Lymphocytes and CD34+ Cells...................................336
15.3.1.2 Label Distribution in Dividing Cell Populations .............337
15.3.1.3 CLIO–Tat Is Not Toxic to Cells at Concentrations
Used for Magnetic Labeling.............................................338
15.3.1.4 CLIO–Tat Labeling Allows Magnetic Sorting
of Lymphocytes Labeled In Vitro.....................................338
15.3.1.5 Recovery of In Vivo Injected Cells ..................................339
15.3.1.6 High Resolution In Vivo MR Imaging
of CLIO–Tat-Labeled Cells..............................................340
15.3.2 Internalization of Paramagnetic Chelates ........................................342
References..............................................................................................................344
15.1 INTRODUCTION
Cellular plasma membrane and intracellular membranes represent natural barriers
to a large number of exogeneous (and endogenous) molecules. To overcome this
delivery barrier for therapeutic and diagnostic drugs, a variety of strategies has been
proposed to ferry agents through cellular membranes. These strategies include receptor
mediated uptake, 1,2 fluid phase endocytosis (pinocytosis), 3 direct fusion with the
327