3 research outputs found
Enhanced Prostate Cancer Targeting by Modified Protease Sensitive Photosensitizer Prodrugs
Prodrugs combining macromolecular delivery systems with
site-selective
drug release represent a powerful strategy to increase selectivity
of anticancer agents. We have adapted this strategy to develop new
polymeric photosensitizer prodrugs (PPP) sensitive to urokinase-like
plasminogen activator (uPA). In these compounds (to be referred to
as uPA-PPPs) multiple copies of pheophorbide <i>a</i> are
attached to a polymeric carrier via peptide linkers that can be cleaved
by uPA, a protease overexpressed in prostate cancer (PCa). uPA-PPPs
are non-phototoxic in their native state but become fluorescent and
produce singlet oxygen after uPA-mediated activation. In the present
work, we studied the influence of side-chain modifications, molecular
weight, and overall charge on the photoactivity and pharmacokinetics
of uPA-PPPs. An <i>in vitro</i> promising candidate with
convertible phototoxicity was then further investigated <i>in
vivo</i>. Systemic administration resulted in a selective accumulation
and activation of the prodrug in luciferase transfected PC-3 xenografts,
resulting in a 4-fold increase in fluorescence emission over time.
Irradiation of fluorescent tumors induced immediate tumor cell eradication
as shown by whole animal bioluminescence imaging. PDT with uPA-PPP
could therefore provide a more selective treatment of localized PCa
and reduce side effects associated with current radical treatments
Squalene-PEG-Exendin as High-Affinity Constructs for Pancreatic Beta-Cells
Novel drug delivery
systems targeting native, transplanted, or
cancerous beta-cells are of utmost importance. Herein, we present
new exendin-4 derivatives with modified unnatural amino acids at strategic
positions within the polypeptide sequence. The modified peptides allowed
modular orthogonal chemical modifications to attach imaging agents
and amphiphilic squalene-PEG groups. The resulting conjugates, SQ-PEG-ExC<sub>1</sub>-Cy5 and SQ-PEG-ExC<sub>40</sub>-Cy5 fluorescence probes,
display low nanomolar affinity to GLP-1R in fluorescence-based binding
assays with EC<sub>50</sub> at 1.1 Ā± 0.2 and 0.8 Ā± 0.2 nM,
respectively. Naturally expressing GLP-1R MIN6 cells and recombinantly
transfected CHL-GLP-1R positive cells were specifically targeted by
all of the new beta-cell probes in vitro. Specific islet targeting
was observed after i.v. injection of SQ-PEG-ExC<sub>1</sub>-Cy5 with
SQ-PEG in normoglycemic mice ex vivo. Semiquantitative biodistribution
analysis by epifluorescence indicated prolonged blood half-life (3.8
h) for the amphiphilic Ex conjugate. Liver and pancreas were identified
as main biodistribution organs for SQ-PEG-ExC<sub>1</sub>-Cy5
Kondratāeva Ligation: DielsāAlder-Based Irreversible Reaction for Bioconjugation
Diversification of existing chemoselective
ligations is required
to efficiently access complex and well-defined biomolecular assemblies
with unique and valuable properties. The development and bioconjugation
applications of a novel DielsāAlder-based irreversible site-specific
ligation are reported. The strategy is based on a Kondratāeva
cycloaddition between bioinert and readily functionalizable 5-alkoxyoxazoles
and maleimides that readily react together under mild and easily tunable
reaction conditions to afford a fully stable pyridine scaffold. The
potential of this novel bioconjugation is demonstrated through the
preparation of fluorescent conjugates of biomolecules and a novel
FoĢrster resonance energy transfer (FRET)-based probe suitable
for the in vivo detection and imaging of urokinase-like plasminogen
activator (uPA), which is a key protease involved in cancer invasion
and metastasis