4 research outputs found
Dissecting the Carbohydrate Specificity of the Anti-HIVā1 2G12 Antibody by Single-Molecule Force Spectroscopy
Broadly neutralizing anti-HIV-1 monoclonal antibody 2G12
exclusively
targets a conserved cluster of high-mannose oligosaccharides present
on outer viral envelope glycoprotein gp120. This characteristic makes
the otherwise immunogenically āsilentā glycan shield
of gp120 a tempting target for drug and vaccine design. However, immune
responses against carbohydrate-based mimics of gp120 have failed to
provide immunization against HIV-1 infection, highlighting the need
to understand the molecular events that determine immunogenicity better.
In this work, the unbinding kinetics of the gp120ā2G12 (<i>k</i><sub>0</sub> = 0.002 Ā± 0.09 s<sup>ā1</sup>, <i>x</i><sup>ā§§Ā </sup> = 1.5 Ā± 1.2 nm), Man<sub>4</sub>ā2G12 (<i>k</i><sub>0</sub> = 0.35 Ā±
0.32 s<sup>ā1</sup>, <i>x</i><sup>ā§§Ā </sup> = 0.6 Ā± 0.2 nm), and Man<sub>5</sub>ā2G12 interactions
were measured by single-molecule force spectroscopy. To our knowledge,
this is the first single-molecule study aimed at dissecting the carbohydrateāantibody
recognition of the gp120ā2G12 interaction. We were able to
confirm crystallographic models that show both the binding of the
linear Man<sub>4</sub> arm to 2G12 and also the multivalent gp120
glycan binding to 2G12. These results demonstrate that single-molecule
force spectroscopy can be successfully used to dissect the molecular
mechanisms underlying immunity
<sup>68</sup>Ga-Labeled Gold Glyconanoparticles for Exploring BloodāBrain Barrier Permeability: Preparation, Biodistribution Studies, and Improved Brain Uptake via Neuropeptide Conjugation
New tools and techniques to improve
brain visualization and assess
drug permeability across the bloodābrain barrier (BBB) are
critically needed. Positron emission tomography (PET) is a highly
sensitive, noninvasive technique that allows the evaluation of the
BBB permeability under normal and disease-state conditions. In this
work, we have developed the synthesis of novel water-soluble and biocompatible
glucose-coated gold nanoparticles (GNPs) carrying BBB-permeable neuropeptides
and a chelator of the positron emitter <sup>68</sup>Ga as a PET reporter
for in vivo tracking biodistribution. The small GNPs (2 nm) are stabilized
and solubilized by a glucose conjugate. A NOTA ligand is the chelating
agent for the <sup>68</sup>Ga, and two related opioid peptides are
used as targeting ligands for improving BBB crossing. The radioactive
labeling of the GNPs is completed in 30 min at 70 Ā°C followed
by purification via centrifugal filtration. As a proof of principle,
a biodistribution study in rats is performed for the different <sup>68</sup>Ga-GNPs. The accumulation of radioactivity in different organs
after intravenous administration is measured by whole body PET imaging
and gamma counter measurements of selected organs. The biodistribution
of the <sup>68</sup>Ga-GNPs varies depending on the ligands, as GNPs
with the same gold core size show different distribution profiles.
One of the targeted <sup>68</sup>Ga-GNPs improves BBB crossing near
3-fold (0.020 Ā± 0.0050% ID/g) compared to nontargeted GNPs (0.0073
Ā± 0.0024% ID/g) as measured by dissection and tissue counting
Residual CTAB Ligands as Mass Spectrometry Labels to Monitor Cellular Uptake of Au Nanorods
Gold nanorods have numerous applications
in biomedical research,
including diagnostics, bioimaging, and photothermal therapy. Even
though surfactant removal and surface conjugation with antifouling
molecules such as polyethylene glycol (PEG) are required to minimize
nonspecific protein binding and cell uptake, the reliable characterization
of these processes remains challenging. We propose here the use of
laser desorption/ionization mass spectrometry (LDI-MS) to study the
ligand exchange efficiency of cetyltrimethylammonium bromide (CTAB)-coated
nanorods with different PEG grafting densities and to characterize
nanorod internalization in cells. Application of LDI-MS analysis shows
that residual CTAB consistently remains adsorbed on PEG-capped Au
nanorods. Interestingly, such residual CTAB can be exploited as a
mass barcode to discern the presence of nanorods in complex fluids
and in vitro cellular systems, even at very low concentrations
Cellular Uptake of Gold Nanoparticles Triggered by HostāGuest Interactions
We describe an approach
to regulate the cellular uptake of small
gold nanoparticles using supramolecular chemistry. The strategy relies
on the functionalization of AuNPs with negatively charged pyranines,
which largely hamper their penetration in cells. Cellular uptake can
be activated <i>in situ</i> through the addition of cationic
covalent cages that specifically recognize the fluorescent pyranine
dyes and counterbalance the negative charges. The high selectivity
and reversibility of the hostāguest recognition activates cellular
uptake, even in protein-rich biological media, as well as its regulation
by rational addition of either cage or pyranine