ENGINEERING OF CELL-PENETRATING PEPTIDE-CONJUGATED INTRACELLULAR DELIVERY SYSTEMS - Biologically-Responsive Hybrid Biomaterials - page 208

Bcl-xL) resulted in robust protein transduction in cultures and also delivered the
protein across the blood-brain barrier to decrease neuronal cell death [79].
Recently L- or D-forms of penetratin, or the L- or D-forms of octaarginine
(L- or D-R8), was used for nasal insulin delivery. It was found that CPPs
dramatically increased nasal insulin absorption, and it was more pronounced for
L- and D-penetratin than L- or D-R8. L-penetratin was the most effective
promoter of insulin absorption compared with others CPPs. The pharmacological
availability and bioavailability of nasally administered insulin was up to 76.7 %
and 50.7 % relative to the subcutaneous route, respectively [80].
Heat shock protein 70 (HSP70) is an intracellular stress protein that confers
cytoprotection to a variety of cellular stressors. Weeler et al. generated a Tat-
HSP70 fusion protein using recombinant methods and treated HSF −/− cells with
either Tat-HSP70 or recombinant HSP70 prior to exposure to hyperoxia or lethal
heat shock. They showed that biologically active, exogenous HSP70 can be
delivered into cells using the HIV-1 Tat protein, and that the Tat-mediated
delivery of HSP70 confers cytoprotection against thermal stress and hyperoxia
and may represent a novel approach to augmenting intracellular HSP70 levels
[81]. Superoxide dismutase fused to TAT or to Pep-1 has been shown to protect
pancreatic beta cells against oxidative stress [82].
Morris et al. developed a new technique for protein delivery based on a
peptide, Pep-1 [60]. This Pep-1 has the capability to deliver different peptides,
proteins, and antibodies inside different cells, in vivo and in vitro, without any
chemical coupling between the cargo and Pep-1 [64]. This approach has the
significant advantage of not requiring any chemical modification of the CPP or
protein cargo, thus simplifying the formulation process. This Pep-1 strategy has
also been used to deliver therapeutic proteins in vivo across the blood-brain
barrier [83].
Antibodies are usually the most difficult large proteins to deliver into cell
and TATp has also enabled delivery of antibodies for radiotherapeutic
application [84]. Thus ability of CPPs to delivery antibodies to cells proves their
potential in the field of intracellular delivery.
2.2. Delivery of nanoparticles
The first example of use of TATp as a vector for nanoparticulate delivery was
described in 1999 [85]. In this study, the functionalized iron oxide nanoparticles
with TATp showed efficient labeling of cells, and thus might serve as a tool for
magnetic resonance imaging (MRI) or magnetic separation of homed cells in
vivo . TATp (48-57) was coupled to the dextran-coated superparamagnetic iron