385 research outputs found
Systematic screening of different polyglycerinâbased dienophile macromonomers for efficient nanogel formation through IEDDA inverse nanoprecipitation
Alternatives for strainâpromoted azideâalkyne cycloaddition (SPAAC) chemistries are needed because of the employment of expensive and not easily scalable precursors such as bicyclo[6.1.0]nonâ4âyne (BCN). Inverse electron demand Diels Alder (iEDDA)âbased click chemistries, using dienophiles and tetrazines, offer a more bioorthogonal and faster toolbox, especially in the biomedical field. Here, the straightforward synthesis of dendritic polyglycerin dienophiles (dPGâdienophiles) and dPGâmethylâtetrazine (dPGâmetTet) as macromonomers for a fast, stable, and scalable nanogel formation by inverse nanoprecipitation is reported. Nanogel sizeâinfluencing parameters are screened such as macromonomer concentration and waterâtoâacetone ratio are screened. dPGânorbonene and dPGâcyclopropene show fast and stable nanogel formation in the size range of 40â200 nm and are thus used for the coprecipitation of the model protein myoglobin. High encapsulation efficiencies of more than 70% at a 5 wt% feed ratio are obtained in both cases, showing the suitability of the mild gelation chemistry for the encapsulation of small proteins
Universal polymer coatings and their representative biomedical applications
Universal polymer coatings have excellent potential for biomedical
applications, because of their substrate-independent properties and versatile
surface functionalization methods. The goal of this review is to summarize the
state-of-art research on universal polymer coatings and their biomedical
applications, as well as to present their common features including some
general rules for their further development
Charged dendrimers revisited: Effective charge and surface potential of dendritic polyglycerol sulfate
We investigate key electrostatic features of charged dendrimers at hand of
the biomedically important dendritic polyglycerol sulfate (dPGS) macromolecule
using multi-scale computer simulations and Zetasizer experiments. In our
simulation study, we first develop an effective mesoscale Hamiltonian specific
to dPGS based on input from all-atom, explicit-water simulations of dPGS of low
generation. Employing this in coarse-grained, implicit-solvent/explicit-salt
Langevin dynamics simulations, we then study dPGS structural and electrostatic
properties up to the sixth generation. By systematically mapping then the
calculated electrostatic potential onto the Debye-H\"uckel form -- that serves
as a basic defining equation for the effective charge -- we determine
well-defined effective net charges and corresponding radii, surface charge
densities, and surface potentials of dPGS. The latter are found to be up to one
order of magnitude smaller than the bare values and consistent with previously
derived theories on charge renormalization and weak saturation for high
dendrimer generations (charges). Finally, we find that the surface potential of
the dendrimers estimated from the simulations compare very well with our new
electrophoretic experiments
Coordination-Induced Spin-State-Switch (CISSS) in water
We present a non-ionic water-soluble porphyrin that does not exhibit
measurable aggregation even at high concentrations in water. The spin state of
the corresponding nickel(II) complex changes from completely diamagnetic (low-
spin) to paramagnetic (high-spin) upon addition of a strong axial ligand. This
leads to a strongly reduced NMR relaxation time of the water protons even at
low concentrations of the complex
Synthesis of pH-degradable polyglycerol-based nanogels by iEDDA-mediated crosslinking for encapsulation of asparaginase using inverse nanoprecipitation
Biocompatible, environmentally responsive, and scalable nanocarriers are needed for targeted and triggered delivery of therapeutic proteins. Suitable polymers, preparation methods, and crosslinking chemistries must be considered for nanogel formation. Biocompatible dendritic polyglycerol (dPG) is used in the mild, surfactant-free inverse nanoprecipitation method for nanogel preparation. The biocompatible, fast, and bioorthogonal inverse electron demand Diels-Alder (iEDDA) crosslinking chemistry is used. In this work, the synthesis of pH-degradable nanogels, based on tetrazine, norbonene, and bicyclo[6.1.0]nonyne (BCN) functionalized macromonomers, is reported. The macromonomers are non-toxic up to 2.5 mg mLâ1 in three different cell lines. Nanogels are obtained in the size range of 47 to 200 nm and can be degraded within 48 h at pH 4.5 (BA-gels), and pH 3 (THP-gels), respectively. Encapsulation of asparaginase (32 kDa) yield encapsulation efficiencies of up to 93% at 5 wt.% feed. Overall, iEDDA-crosslinked pH-degradable dPG-nanogels from inverse nanoprecipitation are promising candidates for biomedical applications
Dendritic nanocarriers based on hyperbranched polymers
Hyperbranched polymers are obtained through one-step polymerization reactions
and exhibit properties that are very similar to those of perfect dendrimer
analogues. Therefore, hyperbranched polymers are a suitable alternative for
perfect dendrimers as building blocks for dendritic nanocarrier systems. With
regard to using soluble hyperbranched polymers as carrier systems, their
flexible chains are a major benefit as they can adopt and compartment guest
molecules. Upon encapsulation, the properties of the host decides the fate of
the guest, e.g., solubility, but the host can also shield a guest from the
environment and protect it, e.g., from degradation and deactivation. With
regard to the advantages of using hyperbranched polymers as nanocarrier
systems and their scalable synthesis, we will discuss different types of
hyperbranched polymers and their application as nanocarrier systems for drugs,
dyes, and other guest molecules
Algebraic Quantum Theory on Manifolds: A Haag-Kastler Setting for Quantum Geometry
Motivated by the invariance of current representations of quantum gravity
under diffeomorphisms much more general than isometries, the Haag-Kastler
setting is extended to manifolds without metric background structure. First,
the causal structure on a differentiable manifold M of arbitrary dimension
(d+1>2) can be defined in purely topological terms, via cones (C-causality).
Then, the general structure of a net of C*-algebras on a manifold M and its
causal properties required for an algebraic quantum field theory can be
described as an extension of the Haag-Kastler axiomatic framework.
An important application is given with quantum geometry on a spatial slice
within the causally exterior region of a topological horizon H, resulting in a
net of Weyl algebras for states with an infinite number of intersection points
of edges and transversal (d-1)-faces within any neighbourhood of the spatial
boundary S^2.Comment: 15 pages, Latex; v2: several corrections, in particular in def. 1 and
in sec.
Micro- and nanogels with labile crosslinks â from synthesis to biomedical applications
Micro- or nanosized three-dimensional crosslinked polymeric networks have been
designed and described for various biomedical applications, including living
cell encapsulation, tissue engineering, and stimuli responsive controlled
delivery of bioactive molecules. For most of these applications, it is
necessary to disintegrate the artificial scaffold into nontoxic residues with
smaller dimensions to ensure renal clearance for better biocompatibility of
the functional materials. This can be achieved by introducing stimuli-
cleavable linkages into the scaffold structures. pH, enzyme, and redox
potential are the most frequently used biological stimuli. Moreover, some
external stimuli, for example light and additives, are also used to trigger
the disintegration of the carriers or their assembly. In this review, we
highlight the recent progress in various chemical and physical methods for
synthesizing and crosslinking micro- and nanogels, as well as their
development for incorporation of cleavable linkages into the network of micro-
and nanogels
Polyester-Based, Biodegradable Core-Multishell Nanocarriers for the Transport of Hydrophobic Drugs
A water-soluble, core-multishell (CMS) nanocarrier based on a new
hyperbranched polyester core building block was synthesized and characterized
towards drug transport and degradation of the nanocarrier. The hydrophobic
drug dexamethasone was encapsulated and the enzyme-mediated biodegradability
was investigated by NMR spectroscopy. The new CMS nanocarrier can transport
one molecule of dexamethasone and degrades within five days at a skin
temperature of 32 °C to biocompatible fragments
Biocatalytic Synthesis Using Self-Assembled Polymeric Nano- and Microreactors
Biocatalysis is increasingly being explored for the sustainable development of green industry. Though enzymes show great industrial potential with their high efficiency, specificity, and selectivity, they suffer from poor usability and stability under abiological conditions. To solve these problems, researchers have fabricated nano- and micro-sized biocatalytic reactors based on the self-assembly of various polymers, leading to highly stable, functional, and reusable biocatalytic systems. This Review highlights recent progress in self-assembled polymeric nano- and microreactors for biocatalytic synthesis, including polymersomes, reverse micelles, polymer emulsions, Pickering emulsions, and static emulsions. We categorize these reactors into monophasic and biphasic systems and discuss their structural characteristics and latest successes with representative examples. We also consider the challenges and potential solutions associated with the future development of this field
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