3 research outputs found
Ultrasmall Paramagnetic Iron Oxide Nanoprobe Targeting Epidermal Growth Factor Receptor for In Vivo Magnetic Resonance Imaging of Hepatocellular Carcinoma
Hepatocellular carcinoma
(HCC) is a common worldwide cancer that
is rising rapidly in incidence. MRI is a powerful noninvasive imaging
modality for HCC detection, but lack of specific contrast agents limits
visualization of small tumors. EGFR is frequently overexpressed in
HCC and is a promising target. Peptides have fast binding kinetics,
short circulatory half-life, low imaging background, high vascular
permeability, and enhanced tissue diffusion for deep tumor penetration.
We demonstrate a peptide specific for EGFR labeled with an ultrasmall
paramagnetic iron oxide (UPIO) nanoparticle with 3.5 nm dimensions
to target HCC using T<sub>1</sub>-weighted MRI. We modified the hydrophobic
core with oleic acid and capped with PEGylated phospholipids DSPE-PEG
and DSPE-PEG-Mal. The EGFR peptide is attached via thioether-mediated
conjugation of a GGGSC linker to the maleimide-terminated phospholipids.
On in vivo MR images of HCC xenograft tumors, we observed peak nanoprobe
uptake at 2 h post-injection followed by a rapid return to baseline
by ∼24 h. We measured significantly greater MR signal in tumor
with the targeted nanoprobe versus scrambled peptide, blocked peptide,
and Gadoteridol. Segmented regions on MR images support rapid renal
clearance. No significant difference in animal weight, necropsy, hematology,
and chemistry was found between treatment and control groups at one
month post-injection. Our nanoprobe based on an EGFR specific peptide
labeled with UPIO designed for high stability and biocompatibility
showed rapid tumor uptake and systemic clearance to demonstrate safety
and promise for clinical translation to detect early HCC
Design and Synthesis of Near-Infrared Peptide for in Vivo Molecular Imaging of HER2
We report the development, characterization,
and validation of
a peptide specific for the extracellular domain of HER2. This probe
chemistry was developed for molecular imaging by using a structural
model to select an optimal combination of amino acids that maximize
the likelihood for unique hydrophobic and hydrophilic interactions
with HER2 domain 3. The sequence KSPNPRF was identified and conjugated
with either FITC or Cy5.5 via a GGGSK linker using Fmoc-mediated solid-phase
synthesis to demonstrate flexibility for this chemical structure to
be labeled with different fluorophores. A scrambled sequence was developed
for control by altering the conformationally rigid spacer and moving
both hydrophobic and hydrophilic amino acids on the C-terminus. We
validated peptide specificity for HER2 in knockdown and competition
experiments using human colorectal cancer cells in vitro, and measured
a binding affinity of <i>k</i><sub>d</sub> = 21 nM and time
constant of <i>k</i> = 0.14 min<sup>–1</sup> (7.14
min). We used this peptide with either topical or intravenous administration
in a preclinical model of colorectal cancer to demonstrate specific
uptake in spontaneous adenomas and to show feasibility for real time
in vivo imaging with near-infrared fluorescence. We used this peptide
in immunofluorescence studies of human proximal colon specimens to
evaluate specificity for sessile serrated and sporadic adenomas. Improved
visualization can be used endoscopically to guide tissue biopsy and
detect premalignant lesions that would otherwise be missed. Our peptide
design for specificity to HER2 is promising for clinical translation
in molecular imaging methods for early cancer detection
Multiplexed Targeting of Barrett’s Neoplasia with a Heterobivalent Ligand: Imaging Study on Mouse Xenograft in Vivo and Human Specimens ex Vivo
Esophageal adenocarcinoma (EAC) is
a molecularly heterogeneous
disease that is rising rapidly in incidence and has poor prognosis.
We developed a heterobivalent peptide to target detection of early
Barrett’s neoplasia by combining monomer heptapeptides specific
for either EGFR or ErbB2 in a heterodimer configuration. The structure
of a triethylene glycol linker was optimized to maximize binding interactions
to the surface receptors on cells. The Cy5.5-labeled heterodimer QRH*–KSP*–E3–Cy5.5
demonstrated specific binding to each target and showed 3-fold greater
fluorescence intensity and 2-fold higher affinity compared with those
of either monomer alone. Peak uptake in xenograft tumors was observed
at 2 h postinjection with systemic clearance by ∼24 h in vivo.
Furthermore, ligand binding was evaluated on human esophageal specimens
ex vivo, and 88% sensitivity and 87% specificity were found for the
detection of either high-grade dysplasia (HGD) or EAC. This peptide
heterodimer shows promise for targeted detection of early Barrett’s
neoplasia in clinical study