Petr Formanek

Tailored Synthesis of Intelligent Polymer Nanocapsules: An Investigation of Controlled Permeability and pH-Dependent Degradability

In this study, we present a new route to synthesize an intelligent polymer nanocapsule with an ultrathin membrane based on surface-initiated reversible addition-fragmentation chain-transfer polymerization. The key concept of our report is to use pH-responsive polydiethylaminoethylmethacrylate as a main membrane-generating component and a degradable disulfide bond to cross-link the membrane. The permeability of membrane, tuned by adjusting pH and using different lengths of the cross-linkers, was proven by showing a dramatic swelling behavior of the nanocapsules with the longest cross-linker from 560 nm at pH 8.0 to 780 nm at pH 4.0. Also, due to the disulfide cross-linker, degradation of the capsules using GSH as reducing agent was achieved which is further significantly promoted at pH 4.0. Using a rather long-chain dithiol cross-linker, the synthesized nanocapsules demonstrated a good permeability allowing that an enzyme myoglobin can be postencapsulated, where the pH controlled enzyme activity by switching membrane permeability was also shown.

Highly ordered arrays of magnetic nanoparticles prepared via block copolymer assembly

In the present study we report a simple and reproducible method to prepare highly ordered arrays of Fe3O4 superparamagnetic nanoparticles (MNPs) via block copolymer (BCP) self assembly. Pre-synthesized MNPs with a mean diameter of 6.1 nm are selectively segregated within the lamellae or hexagonally packed cylinders composed of PVP blocks in poly(styrene-b-vinylpyridine) (PS-b-PVP) block copolymers without any additional surface modification. The density of the stabilizing shell in the MNPs as well as the position of pyridine nitrogen in the PVP block of the BCPs are found to be crucial for selective incorporation of MNPs into the PVP domains. The obtained results suggest a key importance of a mutual affinity between active blocks and the nanoparticles which should be maximized in order to attain high nanoparticles loadings and long-range structural orders.

Synthesis of Hetero-Polymer Functionalized Nanocarriers by Combining Surface-Initiated ATRP and RAFT Polymerization

Smart nanocarriers are created based on a bi-functional hetero-initiator for RAFT and ATRP technique, bi-functionalizing mesoporous silica nanoparticles with two polymer types. The pH-dependent behavior of PDEAEMA as the gatekeeper polymer is verified by electrokinetic measurements and a controlled release behavior is demonstrated using doxorubicin as the drug.

Helical Packing of Nanoparticles Confined in Cylindrical Domains of a Self‐Assembled Block Copolymer Structure

Theoretical models predict that a variety of self-assembled structures of closely packed spherical particles may result when they are confined in a cylindrical domain. In the present work we demonstrate for the first time that the polymer-coated nanoparticles confined in the self-assembled cylindrical domains of a block copolymer pack in helical morphology, where we can isolate individual fibers filled with helically arranged nanoparticles. This finding provides unique possibilities for fundamental as well as application-oriented research in similar directions.

Interconnection of Nanoparticles within 2D Superlattices of PbS/Oleic Acid Thin Films

Make it connected! 2D close-packed layers of inorganic nanoparticles are interconnected by organic fibrils of oleic acid as clearly visualized by electron holography. These fibrils can be mineralised by PbS to transform an organic-inorganic framework to a completely interconnected inorganic semiconducting 2D array.

Carbon onion–sulfur hybrid cathodes for lithium–sulfur batteries

In this study, we explore carbon onions (diameter below 10 nm), for the first time, as a substrate material for lithium sulfur cathodes. We introduce several scalable synthesis routes to fabricate carbon onion–sulfur hybrids by adopting in situ and melt diffusion strategies with sulfur fractions up to 68 mass%. The conducting skeleton of agglomerated carbon onions proved to be responsible for keeping active sulfur always in close vicinity to the conducting matrix. Therefore, the hybrids are found to be efficient cathodes for Li–S batteries, yielding 97–98% Coulombic efficiency over 150 cycles with a slow fading of the specific capacity (ca. 660 mA h g−1 after 150 cycles) in long term cycle test and rate capability experiments.

Functional Cellular Mimics for the Spatiotemporal Control of Multiple Enzymatic Cascade Reactions

Next-generation therapeutic approaches are expected to rely on the engineering of biomimetic cellular systems that can mimic specific cellular functions. Herein, we demonstrate a highly effective route for constructing structural and functional eukaryotic cell mimics by loading pH-sensitive polymersomes as membrane-associated and free-floating organelle mimics inside the multifunctional cell membrane. Metabolism mimicry has been validated by performing successive enzymatic cascade reactions spatially separated at specific sites of cell mimics in the presence and absence of extracellular organelle mimics. These enzymatic reactions take place in a highly controllable, reproducible, efficient, and successive manner. Our biomimetic approach to material design for establishing functional principles brings considerable enrichment to the fields of biomedicine, biocatalysis, biotechnology, and systems biology.

Synthesis of hollow silica nanostructures using functional hairy polymer nanofibers as templates

Hollow silica nanofibers and nanospheres were synthesized from functional hairy polymer nanofibers as sacrificial templates. The polymer nanofibers were isolated from a cylinder-forming polystyrene-block-poly(4-vinylpyridine) block copolymer using a selective-swelling approach.

Multifunctional core–shell polymer–inorganic hybrid nanofibers prepared via block copolymer self-assembly

We demonstrate a simple and robust approach for preparing multifunctional core–shell hybrid nanofibers via block copolymer self-assembly. The approach utilizes the different chemistry and solubilities of the two blocks of a diblock copolymer and different affinity of functional inorganic nanoparticles towards block copolymer constituents. In the first step, the silver nanoparticles (Ag) modified with short-chain polystyrene (PS) ligand are incorporated in the cylindrical domains of a polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer, constituted of PS blocks. The Ag-loaded cylindrical domains are then isolated as nanofibers by swelling the matrix forming P4VP phase using a selective solvent. The isolated nanofibers exhibit core–shell morphology with the core constituted of Ag-loaded PS phase and shell consisting of P4VP chains. The reactive P4VP shell of the nanofibers is subsequently used as a host for depositing a second type of nanoparticles. The second type of nanoparticles could be either directly synthesized on the P4VP shell or deposited from an aqueous dispersion of pre-synthesized nanoparticles. In this work, gold (Au) and cadmium sulfide (CdS) nanoparticles were deposited on the nanofiber shell. The approach is versatile and, in principle, could be extended to the fabrication of various combinations of targeted functionalities in a single nanofiber with core–shell morphology.

Dynamic Docking and Undocking Processes Addressing Selectively the Outside and Inside of Polymersomes

Increasing complexity and diversity of polymersomes and their compartments is a key issue for mimicking cellular functions and protocells. Thus, new challenges arise in terms of achieving tunable membrane permeability and combining it with control over the membrane diffusion process, and thus enabling a localized and dynamic control of functionality and docking possibilities within or on the surface of polymeric compartments. This study reports the concept of polymersomes with pH-tunable membrane permeability for controlling sequential docking and undocking processes of small molecules and nanometer-sized protein mimics selectively on the inside and outside of the polymersome membrane as a further step toward the design of intelligent multifunctional compartments for use in synthetic biology and as protocells. Host-guest interactions between adamantane and β-cyclodextrin as well as noncovalent interactions between poly(ethylene glycol) tails and β-cyclodextrin are used to achieve selective and dynamic functionalization of the inner and outer spheres of the polymersome membrane.