Table 3.

Characteristics of protein transduction domain vs. profection methods

	PTDs	Profection*
Common features	Positive net charge mediates association with cell surface, endocytosis as main route of entrance
Differences	PTD-fusion proteins are at a molecular scale, covalent linkage of cargo and PTD	Particulate complexes, non-covalent association of cargo and transfection reagent
Efficiency and endosomal release	−	+
Sedimentation techniques for increasing efficiency and reducing toxicity applicable?	−	+
Therapeutic potential	+	−
Cytotoxicity/known side effects	HIV1-TAT-PTD, antennapedia-PTD and nona-arginine inhibit TNF signalling by downregulation of TNF-receptors (TNF receptors are internalized without being activated),191 penetratin has inhibitory effect on NFκB,192 dose and exposure-time dependent cytotoxic effects reported for HIV1-TAT-PTD and antennapedia-PTD,193 poration and intense damage of membranes by transportan.194	Cytotoxicity potentially increased compared with DNA-transfections as more lipids are required to complex proteins.76

^*Not including protein cationization. PTD, protein transduction domain; TNF, tumor necrosis factor.