Emi Haladjova

Polymeric nanoparticle engineering: from temperature-responsive polymer mesoglobules to gene delivery systems.

A novel approach for the preparation of nano- and microcapsules in aqueous solutions by using thermoresponsive polymer (TRP) templates (mesoglobules) is described. The method comprised three steps: formation of mesoglobules, coating the templates by seeded radical copolymerization, followed by core dissolution and core removal upon cooling. When mesoglobule entraps biomacromolecules during the process of their formation, it makes it possible to load a controlled amount of bioactive compounds without covalent attachment. Special attention is paid to the mesoglobule dissolution upon cooling, as well as their loading efficiency. Details on the outer shell formation and the possibilities for targeting ligands incorporation and control of the shell porosity are discussed. Finally, the seeded radical copolymerization was used for covering DNA complexes with cationic copolymers bearing TRP blocks. This Review is an attempt to convince researchers of the promising perspectives for using mesoglobules as potential reservoirs, carriers, and transferring agents for biologically active substances.

Poly(vinyl benzyl trimethylammonium chloride) Homo and Block Copolymers Complexation with DNA

In this work we focus on the use of novel homo and block copolymers based on poly(vinyl benzyl trimethylammonium chloride) as gene delivery vectors. The homopolymers and block copolymers were synthesized by RAFT polymerization schemes and molecularly characterized. DNA/polymer complexes (polyplexes) in a wide range of N/P (amino-to-phosphate groups) ratios were prepared. The ability of the novel polymers to form complexes with linear DNA was investigated by light scattering, zeta potential, and ethidium bromide fluorescence quenching measurements. The resulting polyplexes were in the size range of 80-300 nm and their surface potential changed from negative to positive depending on the N/P ratio. The stability of polyplexes was monitored by changes in their hydrodynamic parameters in the presence of salt. The novel vector systems were visualized by transmission electron microscopy. The influence of factors such as molar mass, content, and chemical structure of the polycationic moieties as well as presence of a hydrophilic poly[oligo(ethylene glycol) methacrylate] block on the structure and stability of the polyplexes, kinetics of their formation, and effectiveness of the (co)polymers to shrink and pack DNA was discussed.

Smart Polymeric Nanocarriers of Met-enkephalin

This study describes a novel approach to polymeric nanocarriers of the therapeutic peptide met-enkephalin based on the aggregation of thermoresponsive polymers. Thermoresponsive bioconjugate poly((di(ethylene glycol) monomethyl ether methacrylate)-ran-(oligo(ethylene glycol) monomethyl ether methacrylate) is synthesized by AGET ATRP using modified met-enkephalin as a macroinitiator. The abrupt heating of bioconjugate water solution leads to the self-assembly of bioconjugate chains and the formation of mesoglobules of controlled sizes. Mesoglobules formed by bioconjugates are stabilized by coating with cross-linked two-layer shell via nucleated radical polymerization of N-isopropylacrylamide using a degradable cross-linker. The targeting peptide RGD, containing the fluorescence marker carboxyfluorescein, is linked to a nanocarrier during the formation of the outer shell layer. In the presence of glutathione, the whole shell is completely degradable and the met-enkephalin conjugate is released. It is anticipated that precisely engineered nanoparticles protecting their cargo will emerge as the next-generation platform for cancer therapy and many other biomedical applications.

Polymeric vehicles for transport and delivery of DNA via cationic micelle template method

This work describes the preparation of polymeric non-viral system for transport and delivery of nucleic acids. An amphiphilic poly(2-(dimethylamino)ethyl methacrylate)-block-poly(ε-caprolactone)-block-poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA20-b-PCL70-b-PDMAEMA20) triblock copolymer was synthesized and used for formation of cationic micelles and subsequent complexation with DNA. Next, a protective polymer coating on the complex surface and removal of copolymer from the particle interior were conducted. In this way, polymer nanocapsules containing DNA molecules were obtained. The synthesized polymer, cationic micelles, complexes, and polymer capsules were investigated by proton nuclear magnetic resonance, gel permeation chromatography, dynamic and electrophoretic light scattering, and transmission electron microscopy. In vitro cytotoxicity assessment of the different systems revealed very good tolerance to human cells.

Polyplex Particles Based on Comb‐Like Polyethylenimine/Poly(2‐ethyl‐2‐oxazoline) Copolymers: Relating Biological Performance with Morphology and Structure

The present contribution is focused on feasibility of using comb-like copolymers of polyethylenimine with poly(2-ethyl-2-oxazoline) (LPEI-comb-PEtOx) with varying grafting densities and degrees of polymerization of PEI and PEtOx to deliver DNA molecules into cells. The copolymers form small and well-defined particles at elevated temperatures, which are used as platforms for binding and condensing DNA. The electrostatic interactions between particles and DNA result in formation of sub-100 nm polyplex particles of narrow size distribution and different morphology and structure. The investigated gene delivery systems exhibit transfection efficiency dependent on the copolymer chain topology, shape of the polyplex particles, and internalization pathway. Flow cytometry shows enhanced transfection efficiency of the polyplexes with elongated and ellipsoidal morphology. The preliminary biocompatibility study on a panel of human cell lines shows that pure copolymers and polyplexes thereof are practically devoid of cytotoxicity.

Morphology rearrangement of PEO and PG blocks of amphiphilic copolymer particles in solution affected by FeCl3/acidified water addition

The present contribution describes the preparation of nanosized aggregates by dissolving diblock copolymers consisting of hydrophobic polystyrene (PS) with randomly distributed short diene (D) moieties and hydrophilic polyether (polyethylene oxide (PEO) or polyglycidol (PG)) blocks in selective solvents. Inducing structural and/or size changes of the aggregates by addition of FeCl3/acidified H2O to the system is experimented. Dynamic light scattering (DLS) and size exclusion chromatography (SEC) measurements reveal resizing of the particles whilst adding FeCl3/acidified H2O. Further the structure and size of P(SD-EO/G) block copolymer corе-shell particles are determined by Diffusion Ordered NMR Spectroscopy (DOSY) which indicates a partial reversal of the core-shell structure upon the addition of FeCl3/acidified H2O. Transmission electron microscopy provides a more detailed insight on the morphology, shape and size distribution of the aggregates. For comparison, the change in the particle size under identical conditions for species of preliminary stabilized core-shell morphology is monitored as well.

Application of cationic polymer micelles for the dispersal of bacterial biofilms

Contamination of surfaces in hospitals and food industry by bacterial biofilms is a serious health risk. Of concern is their resistance to routine antibacterials and disinfectants. This requires the development of novel approaches to biofilm detachment. The study evaluates the effectiveness of cationic polymer micelles (CPMs) against pre‐formed biofilms. CPMs based on different polycations were used. The hydrodynamic radius of the particles ranged from 16 to 360 nm. Biofilms of Escherichia coli 420, Pseudomonas aeruginosa PAO1, Staphylococcus aureus 29213 and Bacillus subtilis 168 were cultivated for 24 h then the pre‐formed biofilms were treated with the CPMs for 2, 4 or 6 h. Biofilm biomass was evaluated by the crystal violet assay, and live/dead fluorescence test was applied for bacterial viability. The ability of CPMs to interact with pre‐formed biofilms of the model strains was evaluated. We observed that the most effective CPMs were those based on poly(2‐(dimethylamino)ethyl methacrylate) copolymers which reduced the biofilm biomass three‐ to four‐fold compared with the treatment of the biofilm with water. Significantly reduced vitality of the bacteria in the biofilms was registered by the live/dead stain. The results indicate the applicability of the CPMs for disinfection of biofilm‐contaminated surfaces and the treatment of wounds.