16 research outputs found
Multicompartment Lipid Cubic Nanoparticles with High Protein Upload: Millisecond Dynamics of Formation
Membrane shapes, produced by dynamically assembled lipid/protein architectures, are crucial for both physiological functions and the design of therapeutic nanotechnologies. Here we investigate the dynamics of lipid membrane–neurotrophic BDNF protein complexes formation and ordering in nanoparticles, with the purpose of innovation in nanostructure-based neuroprotection and biomimetic nanoarchitectonics. The kinetic pathway of membrane states associated with rapidly occurring nonequilibrium self-assembled lipid/protein nanoarchitectures was determined by millisecond time-resolved small-angle X-ray scattering (SAXS) at high resolution. The neurotrophin binding and millisecond trafficking along the flexible membranes induced an unusual overlay of channel-network architectures including two coexisting cubic lattices epitaxially connected to lamellar membrane stacks. These time-resolved membrane processes, involving intercalation of discrete stiff proteins in continuous soft membranes, evidence stepwise curvature control mechanisms. The obtained three-phase liquid-crystalline nanoparticles of neurotrophic composition put forward important advancements in multicompartment soft-matter nanostructure design
Synthesis and Solution Properties of PCL‑<i>b</i>‑PHPMA Diblock Copolymers Containing Stable Nitroxyl Radicals
This
work focuses on the synthesis and the aqueous solution properties
of novel amphiphilic PCL-<i>b</i>-PHPMA diblock copolymers
possessing 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) stable
radicals covalently conjugated to the hydrophobic poly(ε-caprolactone)
(PCL) block. A new synthetic approach (a four-step pathway) combining
ring-opening polymerization (ROP), carbodiimide chemistry (DCC method),
a reversible addition–fragmentation chain transfer (RAFT) polymerization
technique, and finally chemical oxidation was employed to successfully
produce a series of TEMPO-containing PCL-<i>b</i>-PHPMA
diblock copolymers for the first time. EPR spectroscopy was applied
to verify successful oxidation of the synthesized diblock copolymers
and to investigate the dynamics of the polymer chains before and after
micellization. The diblock copolymers self-assembled in PBS solution
into spherical radical-containing nanoparticles (RNPs), which were
characterized by <sup>1</sup>H NMR spectroscopy, dynamic (DLS), static
(SLS) light scattering, and cryo-transmission electron microscopy
(cryo-TEM). These novel RNPs could find applications, e.g., as drug
delivery systems and for the treatment of oxidative stress injuries
Polyelectrolyte pH-Responsive Protein-Containing Nanoparticles: The Physicochemical Supramolecular Approach
We
report on the physicochemical properties and self-assembly behavior
of novel efficient pH-sensitive nanocontainers based on the Food and
Drug Administration-approved anionic polymer Eudragit L100-55 (poly(methacrylic
acid-co-ethyl acrylate) 1:1) and nonionic surfactant Brij98. The features
of the interaction between Eudragit L100-55 and Brij98 at different
pH values and their optimal ratio for nanoparticle formation were
studied using isothermal titration calorimetry. The influence of the
polymer-to-surfactant ratio on the size and structure of particles was studied
at different pH values using dynamic light scattering and small-angle
X-ray scattering methods. It was shown that stable nanoparticles are
formed at acidic pH at polymer-to-surfactant molar ratios from 1:43
to 1:139. Trypsin was successfully encapsulated into Eudragit−Brij98
nanoparticles as a model bioactive component. The loading efficiency
was determined by labeling trypsin with radioactive iodine-125. Eudragit−Brij98
nanoparticles effectively protected trypsin against pepsin digestion.
The results showed that trypsin encapsulated into novel pH-sensitive
nanocontainers retained more than 50% of its activity after treatment
with pepsin compared with nonencapsulated trypsin. The described concept
will contribute both to understanding the principles of and designing
next-generation nanocontainers
Fluorinated 2‑Alkyl-2-oxazolines of High Reactivity: Spacer-Length-Induced Acceleration for Cationic Ring-Opening Polymerization As a Basis for Triphilic Block Copolymer Synthesis
The synthesis of defined triphilic
terpolymers with hydrophilic,
lyophilic, and fluorophilic blocks is an important challenge as a
basis for the development of multicompartment self-assembled structures
with potential for, e.g., cascade catalysis and multidrug loading.
The synthesis of fluorophilic poly(2-oxazoline)s generally suffers
from a very low reactivity of fluorinated 2-oxazoline monomers in
cationic ring-opening polymerization (CROP). We report a systematic
study on overcoming the extremely low reactivity of 2-perfluoroalkyl-2-oxazolines
in CROP by the insertion of methyl and ethyl hydrocarbon spacers between
the 2-oxazoline ring and the trifluoromethyl group. The kinetic studies
showed the gradual increase of the rate of polymerization with increasing
of the hydrocarbon spacer length. The monomer with an ethyl spacer
was found to have similar reactivity as 2-alkyl-2-oxazolines and allowed
the synthesis of defined triphilic triblock copolymers
DNA/Fusogenic Lipid Nanocarrier Assembly: Millisecond Structural Dynamics
Structural
changes occurring on a millisecond time scale during
uptake of DNA by cationic lipid nanocarriers are monitored by time-resolved
small-angle X-ray scattering (SAXS) coupled to a rapid-mixing stopped-flow
technique. Nanoparticles (NPs) of nanochannel organization are formed
by PEGylation, hydration, and dispersion of a lipid film of the fusogenic
lipid monoolein in a mixture with positively charged (DOMA) and PEGylated
(DOPE-PEG<sub>2000</sub>) amphiphiles and are characterized by the
inner cubic structure of very large nanochannels favorable for DNA
upload. Ultrafast structural dynamics of complexation and assembly
of these cubosome particles with neurotrophic plasmid DNA (pDNA) is
revealed thanks to the high brightness of the employed synchrotron
X-ray beam. The rate constant of the pDNA/lipid NP complexation is
estimated from dynamic roentgenograms recorded at 4 ms time resolution.
pDNA upload into the vastly hydrated channels of the cubosome carriers
leads to a fast nanoparticle–nanoparticle structural transition
and lipoplex formation involving tightly packed pDNA
Study of Complex Thermosensitive Amphiphilic Polyoxazolines and Their Interaction with Ionic Surfactants. Are Hydrophobic, Thermosensitive, and Hydrophilic Moieties Equally Important?
The temperature-driven self-assembly
of nonionic amphiphilic tailor-made
triblock copolymers has been studied by DLS, NMR, ITC, and SAXS. The
composition of these triblock copolymers is more complex than that
of the vast majority of poly(2-alkyl-2-oxazoline)s: a statistical
thermoresponsive (iPrOx) and hydrophobic (BuOx) central block with
terminal hydrophilic blocks (MeOx). In general, as temperature increases,
nanoparticles form in a process starting with single molecules that
become loose aggregates and ends with the formation of compact nanoparticles.
Here, we first attempt to resolve the effects of each block on nanoparticle
formation. It has been proven that the iPrOx/MeOx ratio determines
the value of the cloud point temperature, whereas the different BuOx–iPrOx
blocks determine the character of the process. Finally, we complete
our investigation by presenting the thermodynamic and structural profiles
of the complexation between these triblock poly(2-alkyl-2-oxazoline)s
and two ionic surfactants. The addition of an ionic surfactant promotes
a rearrangement of the polymer molecules and the formation of complexes
followed by the appearance of polymer–surfactant hybrid micelles.
Analysis of the interaction shows a strong and nonspecific reaction
between the polymers and the anionic surfactant sodium dodecyl sulfate
and weak but polymer-state-sensitive interactions between the polymer
and the cationic surfactant hexadecyltrimethylammonium bromide
Thermoresponsive Polymer Micelles as Potential Nanosized Cancerostatics
An effective chemotherapy for neoplastic
diseases requires the
use of drugs that can reach the site of action at a therapeutically
efficacious concentration and maintain it at a constant level over
a sufficient period of time with minimal side effects. Currently,
conjugates of high-molecular-weight hydrophilic polymers or biocompatible
nanoparticles with stimuli-releasable anticancer drugs are considered
to be some of the most promising systems capable of fulfilling these
criteria. In this work, conjugates of thermoresponsive diblock copolymers
with the covalently bound cancerostatic drug pirarubicin (PIR) were
synthesized as a reversible micelle-forming drug delivery system combining
the benefits of the above-mentioned carriers. The diblock copolymer
carriers were composed of hydrophilic poly[<i>N</i>-(2-hydroxypropyl)methacrylamide]-based
block containing a small amount (∼5 mol %) of comonomer units
with reactive hydrazide groups and a thermoresponsive poly[2-(2-methoxyethoxy)ethyl
methacrylate] block. PIR was attached to the hydrophilic block of
the copolymer through the pH-sensitive hydrazone bond designed to
be stable in the bloodstream at pH 7.4 but to be degraded in an intratumoral/intracellular
environment at pH 5–6. The temperature-induced conformation
change of the thermoresponsive block (coil–globule transition),
followed by self-assembly of the copolymer into a micellar structure,
was controlled by the thermoresponsive block length and PIR content.
The cytotoxicity and intracellular transport of the conjugates as
well as the release of PIR from the conjugates inside the cells, followed
by its accumulation in the cell nuclei, were evaluated in vitro using
human colon adenocarcinoma (DLD-1) cell lines. It was demonstrated
that the studied conjugates have a great potential to become efficacious
in vivo pharmaceuticals
Binding of HSA to Macromolecular <i>p</i>HPMA Based Nanoparticles for Drug Delivery: An Investigation Using Fluorescence Methods
Amphiphilic poly(<i>N</i>-(2-hydroxypropyl)methacrylamide)
copolymers (<i>p</i>HPMA) bearing cholesterol side groups
in phosphate buffer saline self-assemble into nanoparticles (NPs)
which can be used as tumor-targeted drug carriers. It was previously
shown by us that human serum albumin (HSA) interacts weakly with the
NPs. However, the mechanism of this binding could not be resolved
due to overlapping of signals from the complex system. Here, we use
fluorescence labeling to distinguish the components and to characterize
the binding: On the one hand, a fluorescent dye was attached to <i>p</i>HPMA, so that the diffusion behavior of the NPs could be
studied in the presence of HSA using fluorescence lifetime correlation
spectroscopy. On the other hand, quenching of the intrinsic fluorescence
of HSA revealed the origin of the binding, which is mainly the complexation
between HSA and cholesterol side groups. Furthermore, a binding constant
was obtained
Fluorophilic–Lipophilic–Hydrophilic Poly(2-oxazoline) Block Copolymers as MRI Contrast Agents: From Synthesis to Self-Assembly
This work focuses on the synthesis
and self-assembly of triphilic
poly(2-oxazoline) triblock copolymers with high fluorine content toward
our future aim of developing poly(2-oxazoline) magnetic resonance
imaging (MRI) contrast agents. A highly fluorinated 2-substituted-2-oxazoline
monomer, namely 2-(1<i>H</i>,1<i>H</i>,2<i>H</i>,2<i>H</i>-perfluorooctyl)-2-oxazoline, was synthesized
using the Grignard reaction. The polymerization kinetics of the synthesized
monomer was studied, and it was used for the preparation of triblock
copolymers with hydrophilic 2-methyl-2-oxazoline, hydrophobic 2-octyl-2-oxazoline,
and fluorophilic blocks by cationic ring-opening polymerization yielding
polymers with low relatively dispersity (1.2–1.4). The presence
of the blocks with the different nature in one copolymer structure
facilitated self-assembly of the copolymers in water and dimethyl
sulfoxide as observed by dynamic light scattering, cryo-transmission
electron microscopy, and small-angle neutron scattering. The nanoparticle
morphology is strongly influenced by the order and length of each
block and the nature of solvent, leading to nanoparticles with core–shell
structure as confirmed by small-angle neutron scattering. The reported
poly(2-oxazoline) block copolymers with high fluorine content have
high potential for future development of MRI contrast agents
Self-Assembly Thermodynamics of pH-Responsive Amino-Acid-Based Polymers with a Nonionic Surfactant
The behavior of pH-responsive polymers
poly(<i>N</i>-methacryloyl-l-valine) (P1), poly(<i>N</i>-methacryloyl-l-phenylalanine) (P2), and poly(<i>N</i>-methacryloylglycyne-l-leucine) (P3) has been
studied in the presence of the nonionic
surfactant Brij98. The pure polymers phase-separate in an acidic medium
with critical pH<sub>tr</sub> values of 3.7, 5.5, and 3.4, respectively.
The addition of the surfactant prevents phase separation and promotes
reorganization of polymer molecules. The nature of the interaction
between polymer and surfactant depends on the amino acid structure
in the side chain of the polymer. This effect was investigated by
dynamic light scattering, isothermal titration calorimetry, electrophoretic
measurements, small-angle neutron scattering, and infrared spectroscopy.
Thermodynamic analysis revealed an endothermic association reaction
in P1/Brij98 mixture, whereas a strong exothermic effect was observed
for P2/Brij98 and P3/Brij98. Application of regular solution theory
for the analysis of experimental enthalpograms indicated dominant
hydrophobic interactions between P1 and Brij98 and specific interactions
for the P2/Brij98 system. Electrophoretic and dynamic light scattering
measurements support the applicability of the theory to these cases.
The specific interactions can be ascribed to hydrogen bonds formed
between the carboxylic groups of the polymer and the oligo(ethylene
oxide) head groups of the surfactant. Thus, differences in polymer–surfactant
interactions between P1 and P2 polymers result in different structures
of polymer–surfactant complexes. Specifically, small-angle
neutron scattering revealed pearl-necklace complexes and “core–shell”
structures for P1/Brij98 and P2/Brij98 systems, respectively. These
results may help in the design of new pH-responsive site-specific
micellar drug delivery systems or pH-responsive membrane-disrupting
agents