Peter Černoch

Biodegradable star HPMA polymer conjugates of doxorubicin for passive tumor targeting.

New biodegradable star polymer-doxorubicin (Dox) conjugates designed for passive tumor targeting were investigated and the present study described their synthesis, physico-chemical characterization, drug release and biodegradation. In the conjugates the core formed by poly(amido amine) (PAMAM) dendrimers was grafted with semitelechelic N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers bearing doxorubicin attached by hydrazone bonds, which enabled intracellular pH-controlled drug release, or by a GFLG sequence, which was susceptible to enzymatic degradation. The controlled synthesis utilizing semitelechelic copolymer precursors facilitated preparation of biodegradable polymer conjugates in a broad range of molecular weights (110-295 kDa) while still maintaining low polydispersity (∼1.7). The polymer grafts were attached to the dendrimers either through stable amide bonds or enzymatically or reductively degradable spacers, which enabled intracellular degradation of the high molecular weight polymer carrier to products that were able to be excreted from the body by glomerular filtration. Biodegradability tests showed that the rate of degradation was much faster for reductively degradable conjugates (completed within 4 h) than the degradation of conjugates linked via an enzymatically degradable oligopeptide GFLG sequence (within 72 h). This finding was likely due to the difference in steric hindrance for the small molecule glutathione and the enzyme cathepsin B. As for drug release, the conjugates were fairly stable in buffer at pH 7.4 (model of blood stream) but released doxorubicin either under mild acidic conditions or in the presence of lysosomal enzyme cathepsin B, both of which modeled the tumor cell microenvironment.

Thermoresponsive Polymers for Nuclear Medicine: Which Polymer Is the Best?

Thermoresponsive polymers showing cloud point temperatures (CPT) in aqueous solutions are very promising for the construction of various systems in biomedical field. In many of these applications these polymers get in contact with ionizing radiation, e.g., if they are used as carriers for radiopharmaceuticals or during radiation sterilization. Despite this fact, radiosensitivity of these polymers is largely overlooked to date. In this work, we describe the effect of electron beam ionizing radiation on the physicochemical and phase separation properties of selected thermoresponsive polymers with CPT between room and body temperature. Stability of the polymers to radiation (doses 0-20 kGy) in aqueous solutions increased in the order poly(N-vinylcaprolactam) (PVCL, the least stable) ≪ poly[N-(2,2-difluoroethyl)acrylamide] (DFP) < poly(N-isopropylacrylamide) (PNIPAM) ≪ poly(2-isopropyl-2-oxazoline-co-2-n-butyl-2-oxazoline) (POX). Even low doses of β radiation (1 kGy), which are highly relevant to the storage of polymer radiotherapeutics and sterilization of biomedical systems, cause significant increase in molecular weight due to cross-linking (except for POX, where this effect is weak). In the case of PVCL irradiated with low doses, the increase in molecular weight induced an increase in the CPT of the polymer. For PNIPAM and DFP, there is strong chain hydrophilization leading to an increase in CPT. From this perspective, POX is the most suitable polymer for the construction of delivery systems that experience exposure to radiation, while PVCL is the least suitable and PNIPAM and DFP are suitable only for low radiation demands.

Water soluble poly(styrene sulfonate)-b-poly(vinylidene fluoride)-b-poly(styrene sulfonate) triblock copolymer nanoparticles

A visible light, Mn2(CO)2-photomediated process was used to enable the iodine degenerative transfer controlled radical polymerization of vinylidene fluoride (VDF) initiated from I–(CF2)6–I, and the successive quantitative activation of the ∼CH2–CF2–I and ∼CF2–CH2–I chain ends of I–PVDF–I, to produce a series of PNpSS-b-PVDF-b-PNpSS triblock copolymers (NpSS/VDF/NpSS = 4/60/4, 15/60/15, 34/60/34) with neopentyl styrene sulfonate (NpSS), which upon NaN3 deprotection, afforded the corresponding PNaSS-b-PVDF-b-PNaSS. All blocks, as well as PVDF, PNpSS and PNaSS formed water stable dispersion/solutions following either nanoprecipitation from acetone (PVDF, PNpSS, and PNpSS-b-PVDF-b-PNpSS) or direct dissolution in water (PNaSS, PNaSS-b-PVDF-b-PNaSS). Remarkably, all PNaSS-b-PVDF-b-PNaSS triblocks also provided indefinitely stable systems even under the high ionic strength conditions of phosphate buffered saline (PBS) solutions, corresponding to cell-isotonic, pH = 7.4 conditions. These trends were found to be consistent with the block composition dependence of the apparent hydrodynamic radius (Rh), conductivity, and zeta potential (ζ), where Rh increases upon deprotection from about 35–25 nm to about 168–136 nm in water, and decreases to 133–86 nm in PBS solutions, ζ decreases from ∼−40 mV to ∼−70 mV in water and increases to ∼−18 mV in PBS, and where the conductivity is negligible for PNpSS-b-PVDF-b-PNpSS but then increases linearly to ∼0.2 mS cm−1 for PNaSS-b-PVDF-b-PNaSS in water to reach ∼17 mS cm−1 in PBS. Finally, the blocks were evaluated as promising 19F-MRI contrast agents.

Temoporfin-loaded 1-tetradecanol-based thermoresponsive solid lipid nanoparticles for photodynamic therapy.

We developed fully biodegradable/metabolizable nanosystem based on polymer surfactant-stabilized thermoresponsive solid lipid nanoparticles with non-covalently bound photosensitizer temoporfin (T-SLNP) with particle size below 50nm. The efficacy of T-SLNP was compared with commercial temoporfin formulation in terms of in vitro phototoxicity in 4T1 (murine mammary carcinoma) and MDA-MB-231(human breast adenocarcinoma) cells and of in vivo anticancer effect in Nu/Nu mice bearing MDA-MB-231 tumors. In vitro study demonstrated faster accumulation kinetics in the cells for our formulation design resulting in higher phototoxicity against the tumor cells. In vivo anticancer efficacy was markedly improved by T-SLNP compared with commercial temoporfin formulation. Owing to controlled and sustained release properties, subcellular size, biocompatibility with tissue and cells, the T-SLNP nanodispersion prepared in this study represents promising drug delivery system applicable in cancer treatment.

Thermoresponsive polymer system based on poly(N-vinylcaprolactam) intended for local radiotherapy applications

Brachytherapy represents effective local therapy of unresectable solid tumors with very few side effects. Radiolabeled thermoresponsive polymers offer almost noninvasive approach to brachytherapy applications. A radioiodinated, water-soluble, thermosensitive poly(N-vinylcaprolactam) (PVCL) polymer was prepared using two approaches. The direct copolymerization with N-methacryloyl-l-tyrosinamide, as well as end-capping of carboxy-terminated PVCL homopolymer with tyramine, were used. In both cases the product was successfully radiolabeled with (125)I. The obtained polymers demonstrate cloud-point temperature (TC) values in the range of 33-35°C in all the studied solvent systems (water, PBS (pH 7.4) and physiological saline solution). Above the cloud point temperature, the molecularly dissolved polymer is macroprecipitated from the solution. The TC values close to the human body temperature of this biocompatible poly(N-vinylcaprolactam) polymer makes it a promising material intended for local therapy of solid tumors.

Three-Dimensional Analysis of Dynamic Light Scattering Data: Application to Self-Organized Polymer Solutions

Abstract Semi-dilute solutions of diblock copolymers in selective partially miscible solvent mixtures have been studied by dynamic light scattering and pulsed-field gradient NMR. Several dynamic modes have been identified as cooperative diffusion, polymer self-diffusion, and cluster diffusion. Their temperature dependences changed dramatically at a certain temperature, below which solutions underwent self-organization. Interpretation of the complex behavior of the dynamic processes observed has been made. The importance of a 3-D representation of the distributions of relaxation times is demonstrated.

Self-assembled polymeric chelate nanoparticles as potential theranostic agents.

Improvements in cancer diagnostics and therapy have recently attracted the interest of many different branches of science. This study presents one of the new possible approaches in the diagnostics and therapy of cancer by using polymeric chelates as carriers. Graft copolymers with a backbone containing 8-hydroxyquinoline-5-sulfonic acid chelating groups and poly(ethylene oxide) hydrophilic grafts are synthesized and characterized. The polymers assemble and form particles after the addition of a biometal cation, such as iron or copper. The obtained nanoparticles exhibit a hydrodynamic diameter of around 25 nm and a stability of at least several hours, which are counted as essential parameters for biomedical purposes. To prove their biodegradability, a model degradation with deferoxamine is performed and, together with high radiolabeling efficiency with copper-64, their possible use for nuclear medicine purposes is demonstrated.

Tungsten (VI) based “molecular puzzle” photoluminescent nanoparticles easily covered with biocompatible natural polysaccharides via direct chelation

Multimodal probes, which can be simultaneously visualized by multiple imaging modalities, enable the cellular uptake, intracellular fate, biodistribution and elimination to be tracked in organisms. In this study, we report the synthesis of crystalline WO3 and CaWO4 doped with Eu3+ or Tb3+ nanoparticles (size range of 10-160u202fnm) coated with polysaccharides, and these nanoparticles constitute a versatile easy-to-construct modular toolbox for multimodal imaging. The particles adsorb significant amounts of polysaccharides from the solution, providing biocompatibility and may serve as a platform for labeling. For WO3, the sorption is reversible. However, on CaWO4, stable coating is formed. CaWO4/Tb3+ coated with chemisorbed dextrin, mannan, guar gum and sodium alginate successfully underwent endocytosis with HepG2 cells and was visualized using confocal microscopy.