5 research outputs found
Effect of Connectivity on the Structure and the LiquidâSolid Transition of Dense Suspensions of Soft Colloids
Aqueous solutions of multiarm flower-like
polyÂ(ethylene oxide)
(PEO) were formed and connected to various degrees by self-assembly.
The structure was rendered permanent by <i>in situ</i> UV-irradiation.
Dense suspensions of these single and connected soft colloids were
studied by static and dynamic light scattering and viscosity measurements.
The concentration dependence of the osmotic compressibility, the dynamic
correlation length, and the viscosity of single flowers was shown
to be close to that of equivalent PEO star-like polymers demonstrating
that the effect of forming loops on the interaction is small. It was
found that the osmotic compressibility and the dynamic correlation
length of dense suspensions are not influenced by the bridging. However,
when flower polymers are connected into clusters, motion in dense
suspensions needs to be collective over larger length scales. This
causes a much stronger increase of the viscosity for dense suspensions
of interpenetrated clusters compared to single-flower polymers
Sphere-Like ProteinâGlycopolymer Nanostructures Tailored by Polyassociation
Key parameters allow a reproducible
polyassociation between avidin
and biotinylated glycopolymers in order to fabricate defined supramolecular
nanostructures for future (bio)Âmedical and biotechnological applications.
Thus, the polymerization efficiency of biotinylated glycopolymers
in the fabrication of biohybrid structures (BHS) was investigated
with regard to the influence of (i) the degree of biotinylation of
the dendritic glycoarchitectures, (ii) two biotin linkers, (iii) the
dendritic scaffold (perfectly branched vs hyperbranched), and (iv)
the ligandâreceptor stoichiometry. The adjustment of all these
parameters opens the way to fabricate defined sizes of the final biohybrid
structures as a multifunctional platform ready for their use in different
applications. Various analytical techniques, including purification
of BHS, were used to gain fundamental insights into the structural
properties of the resulting proteinâglycopolymer BHS. Finally,
the elucidation of pivotal conformational properties of isolated BHS
with defined sizes by asymmetrical flow field flow fractionation study
revealed that they mainly possess spherical-/star-like properties.
From this study, the fundamental knowledge can be likely transferred
to other assemblies formed by molecular recognition processes (e.g.,
adamantane-β-cyclodextrin)
Coil-like Enzymatic Biohybrid Structures Fabricated by Rational Design: Controlling Size and Enzyme Activity over Sequential Nanoparticle Bioconjugation and Filtration Steps
Well-defined
enzymatic biohybrid structures (BHS) composed of avidin, biotinylated
polyÂ(propyleneimine) glycodendrimers, and biotinylated horseradish
peroxidase were fabricated by a sequential polyassociation reaction
to adopt directed enzyme prodrug therapy to proteinâglycopolymer
BHS for potential biomedical applications. To tailor and gain fundamental
insight into pivotal properties such as size and molar mass of these
BHS, the dependence on the fabrication sequence was probed and thoroughly
investigated by several complementary methods (e.g., UV/vis, DLS,
cryoTEM, AF4-LS). Subsequent purification by hollow fiber filtration
allowed us to obtain highly pure and well-defined BHS. Overall, by
rational design and control of preparation parameters, e.g., fabrication
sequence, ligandâreceptor stoichiometry, and degree of biotinylation,
well-defined BHS with stable and even strongly enhanced enzymatic
activities can be achieved. Open coil-like structures of BHS with
few branches are available by the sequential bioconjugation approach
between synthetic and biological macromolecules possessing similar
size dimensions
Tunable Fluorescence of a Semiconducting Polythiophene Positioned on DNA Origami
A novel
approach for the integration of Ď-conjugated polymers
(CPs) into DNA-based nanostructures is presented. Using the controlled
Kumada catalyst-transfer polycondensation, well-defined thiophene-based
polymers with controllable molecular weight, specific end groups,
and water-soluble oligoethylene glycol-based side chains were synthesized.
The end groups were used for the easy but highly efficient click chemistry-based
attachment of end-functionalized oligodeoxynucleotides (ODNs) with
predesigned sequences. As demonstrated by surface plasmon resonance
spectroscopy, the prepared block copolymers (BCPs), P3Â(EO)<sub>3</sub>T-<i>b</i>-ODN, comprising different ODN lengths and specific
or repetitive sequences, undergo specific hybridization with complementary,
thiol-functionalized ODNs immobilized on a gold surface. Furthermore,
the site-specific attachment of the BCPs to DNA origami structures
is studied. We demonstrate that a nanoscale object, that is, a single
BCP with a single ODN handle, can be directed and bound to the DNA
origami with reasonable yield, site-specificity, and high spatial
density. On the basis of these results, we are able to demonstrate
for the first time that optical properties of CP molecules densely
immobilized on DNA origami can be locally fine-tuned by controlling
the attractive ĎâĎ-stacking interactions between
the CPs. In particular, we show that the fluorescence of the immobilized
CP molecules can be significantly enhanced by surfactant-induced breakup
of ĎâĎ-stacking interactions between the CPâs
backbones. Such molecular control over the emission intensity of the
CPs can be valuable for the construction of sophisticated switchable
nanophotonic devices and nanoscale biosensors
Poly(ethylene oxide)â<i>b</i>âpoly(3-sulfopropyl methacrylate) Block Copolymers for Calcium Phosphate Mineralization and Biofilm Inhibition
PolyÂ(ethylene oxide) (PEO) has long
been used as an additive in
toothpaste, partly because it reduces biofilm formation on teeth.
It does not, however, reduce the formation of dental calculus or support
the remineralization of dental enamel or dentine. The present article
describes the synthesis of new block copolymers on the basis of PEO
and polyÂ(3-sulfopropyl methacrylate) blocks using atom transfer radical
polymerization. The polymers have very large molecular weights (over
10<sup>6</sup> g/mol) and are highly water-soluble. They delay the
precipitation of calcium phosphate from aqueous solution but, upon
precipitation, lead to relatively monodisperse hydroxyapatite (HAP)
spheres. Moreover, the polymers inhibit the bacterial colonization
of human enamel by <i>Streptococcus gordonii</i>, a pioneer
bacterium in oral biofilm formation, in vitro. The formation of well-defined
HAP spheres suggests that a polymer-induced liquid precursor phase
could be involved in the precipitation process. Moreover, the inhibition
of bacterial adhesion suggests that the polymers could be utilized
in caries prevention