7 research outputs found
Molecular Dynamics Simulation and Experimental Studies of Gold Nanoparticle Templated HDL-like Nanoparticles for Cholesterol Metabolism Therapeutics
High-density lipoprotein
(HDL) plays an important role in the transport and metabolism of cholesterol.
Mimics of HDL are being explored as potentially powerful therapeutic
agents for removing excess cholesterol from arterial plaques. Gold
nanoparticles (AuNPs) functionalized with apolipoprotein A-I and with
the lipids 1,2-dipalmitoyl-<i>sn</i>-glycero-3-phosphocholine
and 1,2-dipalmitoyl-<i>sn</i>-glycero-3-phosphoethanolamine-N-[3-(2-pyridyldithio)propionate]
have been demonstrated to be robust acceptors of cellular cholesterol.
However, detailed structural information about this functionalized
HDL AuNP is still lacking. In this study, we have used X-ray photoelectron
spectroscopy and lecithin/cholesterol acyltransferase activation experiments
together with coarse-grained and all-atom molecular dynamics simulations
to model the structure and cholesterol uptake properties of the HDL
AuNP construct. By simulating different apolipoprotein-loaded AuNPs,
we find that lipids are oriented differently in regions with and without
apoA-I. We also show that in this functionalized HDL AuNP, the distribution
of cholesteryl ester maintains a reverse concentration gradient that
is similar to the gradient found in native HDL
Thrombin-Targeted Liposomes Establish a Sustained Localized Anticlotting Barrier against Acute Thrombosis
The
goal of the present work was to design and test an acute-use
nanoparticle-based antithrombotic agent that exhibits sustained local
inhibition of thrombin without requiring a systemic anticoagulant
effect to function against acute arterial thrombosis. To demonstrate
proof of concept, we functionalized the surface of liposomes with
multiple copies of the direct thrombin inhibitor, d-phenylalanyl-l-prolyl-l-arginyl-chloromethyl ketone (PPACK), which
exhibits high affinity for thrombin as a free agent but manifests
too rapid clearance <i>in vivo</i> to be effective alone.
The PPACK-liposomes were formulated as single unilamellar vesicles,
with a diameter of 170.78 ± 10.59 nm and a near neutral charge. <i>In vitro</i> models confirmed the inhibitory activity of PPACK-liposomes,
demonstrating a <i>K</i><sub><i>I</i>′</sub> of 172.6 nM. In experimental clots <i>in vitro</i>, treatment
of formed clots completely abrogated any further clotting upon exposure
to human plasma. The liposomes were evaluated <i>in vivo</i> in a model of photochemical-induced carotid artery injury, resulting
in significantly prolonged arterial occlusion time over that of controls
(69.06 ± 5.65 min for saline treatment, <i>N</i> =
6, 71.33 ± 9.46 min for free PPACK treated; <i>N</i> = 4, 85.75 ± 18.24 min for precursor liposomes; <i>N</i> = 4, 139.75 ± 20.46 min for PPACK-liposomes; <i>P</i> = 0.0049, <i>N</i> = 6). Systemic anticoagulant profiles
revealed a rapid return to control levels within 50 min, while still
maintaining antithrombin activity at the injury site. The establishment
of a potent and long-acting anticoagulant surface over a newly forming
clot with the use of thrombin targeted nanoparticles that do not require
systemic anticoagulation to be effective offers an alternative site-targeted
approach to the management of acute thrombosis