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Cell-Penetrating Peptide Conjugations and Magnetic Cell Labels 329
TABLE 15.1
Some Examples of CPP-Assisted Delivery Systems
CPP Cargos Ref.
HIV-Tat Peptide 36, 49
Protein 7, 18, 50–52
Oligonucleotide 28
DNA 53
Fluorescence tag 8, 33, 54
Chelator 33
Liposome 55
Particles 34, 35
Antennapedia Peptides 38, 56, 57
Protein 58
Oligonucleotide 59, 60
PNA 29
Transportan Peptide 56
Protein 23
PNA 29
Loligomer Fluorescence tag 15
Plasmid DNA 32
Drug 61
Hydrophobic signal Peptide 16, 24, 62
Protein 4
Oligonucleotide 27
Oligoarginine Fluorescence tag 39–41
Peptide 63
VP-22 Protein 13
used conjugating agents (“cross-linking agents”) can be divided into two subgroups:
homobifunctional conjugating reagents, which contain at least two identical reactive
groups, and heterobifunctional reagents, which have two different reactive groups.
The reactive groups usually include amines, sulfhydryls, and carboxylic acids. Other
conjugating agents, such as photoreactive and biotin–avidine agents, are less frequently
used in CPP conjugation and thus will not be discussed in this chapter.
15.2.1 DIRECT SYNTHESIS OF CPP CONJUGATES
Typically, CPPs are synthesized on an automatic synthesizer using solid phase
peptide chemistry. If CPP conjugates can be synthesized on the synthesizer directly,
the preparation would be convenient and straightforward. At least three questions
must be answered before making the conjugates. First, will the cargo molecules
survive in peptide synthesis and cleavage conditions? Second, does the cargo molecule
have the right functional group for coupling? Third, how is a synthetic scheme
designed? Usually this approach is only used for conjugating small synthetic compounds
to CPP.