Acrylamides with hydrolytically labile carbonate ester side chains as versatile building blocks for well-defined block copolymer micelles via RAFT polymerization

En route towards improved delivery systems for targeted chemotherapy, we propose a straightforward approach for the hydrophobic modification of the acrylamide N-(2-Hydroxyethyl) acrylamide (HEAm). An ethyl or benzyl group was introduced via a hydrolytically sensitive carbonate ester yielding HEAm-EC and HEAm-BC, respectively. Block copolymers of HEAm, respectively PEG and HEAm-EC or HEAm-BC were successfully synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, obtaining a library of well-defined block copolymers with different degrees of polymerization (DP). To further explore the versatility of our approach in terms of polymer synthesis, self-assembly, drug solubilization and in vitro cell interaction, polyethylene glycol (PEG) and polyHEAm as hydrophilic polymer blocks were compared. The block copolymers formed micellar nanoparticles (10-100 nm) in PBS and could efficiently solubilize hydrophobic dyes and anti-cancer drugs. Benzyl carbonate ester side chains increased micellar stability and drug loading capacity. Moreover, PEG as hydrophilic block showed in comparison to HEAm more promising results concerning both colloidal stability and drug loading capacity. Confocal microscopy showed that the micelles could efficiently deliver a hydrophobic dye inside the cells. Finally, we also demonstrated efficient formulation of the anti-cancer drug paclitaxel with an in vitro cancer cell killing performance comparable or even better than the two commercial PTX nano-formulations Abraxane and Genexol-PM at equal drug dose. In conclusion, modification of HEAm through carbonate linkages offers a versatile platform for the design of degradable polymers with potential for biomedical applications

Biodegradable Poly(2-Dimethylamino Ethylamino)Phosphazene for In Vivo Gene Delivery to Tumor Cells. Effect of Polymer Molecular Weight

Purpose. Previously, we have shown that complexes of plasmid DNA with the biodegradable polymer poly(2-dimethylamino ethylamino)phosphazene (p(DMAEA)-ppz) mediated tumor selective gene expression after intravenous administration in mice. In this study, we investigated the effect of p(DMAEA)-ppz molecular weight on both in vitro and in vivo tumor transfection, as well as on complex induced toxicity. Materials and Methods. p(DMAEA)-ppz with a broad molar mass distribution was fractionated by preparative size exclusion chromatography. Polyplexes consisting of plasmid DNA and the collected polymer fractions were tested for biophysical properties, (cyto)toxicity and transfection activity. Results. Four p(DMAEA)-ppz fractions were collected with weight average molecular weights ranging from 130 to 950 kDa, and with narrow molecular mass distributions (Mw/Mn from 1.1 to 1.3). At polymer-to-DNA (N/P) ratios above 6, polyplexes based on these polymers were all positively charged (zeta potential 25–29 mV), and had a size of 80–90 nm. The in vitro cytotoxicity of the polyplexes positively correlated with polymer molecular weight. The in vitro transfection activity of the different polyplexes depended on their N/P ratio, and was affected by the degree of cytotoxicity, as well as the colloidal stability of the different polyplexes. Intravenous administration of polyplexes based on the high molecular weight polymers led to apparent toxicity, as a result of polyplex-induced erythrocyte aggregation. On the other hand, administration of polyplexes based on low molecular weight p(DMAEA)-ppz_s (Mw130 kDa) did not show signs of toxicity and resulted in tumor selective gene expression. Conclusion. Polymer molecular weight fractionation enabled us to optimize the transfection efficiency/ toxicity ratio of p(DMAEA)-ppz polyplexes for in vitro and in vivo tumor transfection. KEY WORDS: biodegradable; cationic polymer; DNA; molecular weight; tumor gene delivery

Biotin-decorated all-HPMA polymeric micelles for paclitaxel delivery

To avoid poly(ethylene glycol)-related issues of nanomedicines such as accelerated blood clearance, fully N-2-hydroxypropyl methacrylamide (HPMAm)-based polymeric micelles decorated with biotin for drug delivery were designed. To this end, a biotin-functionalized chain transfer agent (CTA), 4-cyano-4-[(dodecylsulfanylthiocarbonyl)-sulfanyl]pentanoic acid (biotin-CDTPA), was synthesized for reversible addition-fragmentation chain-transfer (RAFT) polymerization. Amphiphilic poly(N-2-hydroxypropyl methacrylamide)-block-poly(N-2-benzoyloxypropyl methacrylamide) (p(HPMAm)-b-p(HPMAm-Bz)) with molecular weights ranging from 8 to 24 kDa were synthesized using CDTPA or biotin-CDTPA as CTA and 2,2'-azobis(2-methylpropionitrile) as initiator. The copolymers self-assembled in aqueous media into micelles with sizes of 40-90 nm which positively correlated to the chain length of the hydrophobic block in the polymers, whereas the critical micelle concentrations decreased with increasing hydrophobic block length. The polymer with a molecular weight of 22.1 kDa was used to prepare paclitaxel-loaded micelles which had sizes between 61 and 70 nm, and a maximum loading capacity of around 10 wt%. A549 lung cancer cells overexpressing the biotin receptor, internalized the biotin-decorated micelles more efficiently than non-targeted micelles, while very low internalization of both types of micelles by HEK293 human embryonic kidney cells lacking the biotin receptor was observed. As a consequence, the paclitaxel-loaded micelles with biotin decoration exhibited stronger cytotoxicity in A549 cells than non-targeted micelles. Overall, a synthetic pathway to obtain actively targeted poly(ethylene glycol)-free micelles fully based on a poly(HPMAm) backbone was established. These polymeric micelles are promising systems for the delivery of hydrophobic anticancer drugs

Кіноніми Кіровоградщини: особливості вибору кличок та способи їх творення

Стаття присвячена вивченню особливостей української кінонімії. Основну увагу зосереджено на дослідженні процесу номінації та способів словотворення кличок собак. Окремо розглянуто офіційні назви тварин, які мають родослівну.Статья посвящена изучению особенностей украинской кинонимии. Основное внимание сосредоточено на изучении процесса номинации и способах словообразования кличек собак. Отдельно рассмотрены официальные названия собак, имеющих родословную.The article is devoted to the research of the peculiarities of Ukrainian cynonymy. Most attention is taid to the research of the process of nomination and to the ways of formation of dogs' names. Special consideration is given to the official names of the animals with genealogy

Mechanistic Study on the Degradation of Hydrolysable Core-Crosslinked Polymeric Micelles

Core-crosslinked polymeric micelles (CCPMs) are an attractive class of nanocarriers for drug delivery. Two crosslinking approaches to form CCPMs exist: either via a low-molecular-weight crosslinking agent to connect homogeneous polymer chains with reactive handles or via cross-reactive handles on polymers to link them to each other (complementary polymers). Previously, CCPMs based on methoxy poly(ethylene glycol)- b-poly[ N-(2-hydroxypropyl) methacrylamide-lactate] (mPEG- b-PHPMAmLac n ) modified with thioesters were crosslinked via native chemical ligation (NCL, a reaction between a cysteine residue and thioester resulting in an amide bond) using a bifunctional cysteine containing crosslinker. These CCPMs are degradable under physiological conditions due to hydrolysis of the ester groups present in the crosslinks. The rapid onset of degradation observed previously, as measured by the light scattering intensity, questions the effectiveness of crosslinking via a bifunctional agent. Particularly due to the possibility of intrachain crosslinks that can occur using such a small crosslinker, we investigated the degradation mechanism of CCPMs generated via both approaches using various analytical techniques. CCPMs based on complementary polymers degraded slower at pH 7.4 and 37 °C than CCPMs with a crosslinker (the half-life of the light scattering intensity was approximately 170 h versus 80 h, respectively). Through comparative analysis of the degradation profiles of the two different CCPMs, we conclude that partially ineffective intrachain crosslinks are likely formed using the small crosslinker, which contributed to more rapid CCPM degradation. Overall, this study shows that the type of crosslinking approach can significantly affect degradation kinetics, and this should be taken into consideration when developing new degradable CCPM platforms

Controlled Release of Octreotide and Assessment of Peptide Acylation from Poly(D,L-lactide-co-hydroxymethyl glycolide) Compared to PLGA Microspheres

# The Author(s) 2011. This article is published with open access at Springerlink.com Purpose To investigate the in vitro release of octreotide acetate, a somatostatin agonist, from microspheres based on a hydrophilic polyester, poly(D,L-lactide-co-hydroxymethyl glycolide) (PLHMGA). Methods Spherical and non-porous octreotide-loaded PLHMGA microspheres (12 to 16 μm) and loading efficiency of 60–70% were prepared by a solvent evaporation. Octreotide release profiles were compared with commercial PLGA formulation (Sandostatin LAR ®); possible peptide modification with lactic, glycolic and hydroxymethyl glycolic acid units was monitored. Results PLHMGA microspheres showed burst release (~20%) followed by sustained release for 20–60 days, depending on the hydrophilicity of the polymer. Percentage of released loaded peptide was high (70–90%);>60 % of released peptide was native octreotide. PLGA microspheres did not show peptide release for the first 10 days, after which it was released in a sustained manner over the next 90 days;>75 % of released peptides were acylated adducts. Conclusions PLHMGA microspheres are promising controlled systems for peptides with excellent control over release kinetics. Moreover, substantially less peptide modification occurred in PLHMGA than in PLGA microspheres. KEY WORDS acylation. aliphatic polyester. controlle

A facile modular approach toward multifunctional supramolecular polyplexes for targeting gene delivery

Extensive efforts and numerous methodologies have been explored to develop safe and efficient gene carriers that are capable of overcoming multiple extra- and intracellular barriers during the transfection process. However, it is a great challenge to fabricate a gene carrier system containing multiple functional components. In this work, we propose a facile modular approach to design targeted multifunctional gene delivery systems, which are based on building blocks with pre-defined functions to tackle specific barriers. These building blocks can be rationally combined and self-assemble into an integrated gene delivery system via host-guest interactions. As a proof of concept, three adamantyl-terminated targeting guest modules, adamantyl terminated RGD peptide (Ad-RGD), folate and lactobionic acid terminated PEGs (FA-PEG-Ad and LA-PEG-Ad), were synthesized, characterized, and utilized for post-functionalizing of adamantyl decorated cationic PEI based supramolecular polyplexes (PEI-Ad4/PCD/DNA) through the free CD units of the poly(β-cyclodextran) (PCD) host module. These multifunctional targeting supramolecular polyplexes exhibited enhanced cellular uptake and excellent transfection activity in receptor-positive cells. By modulating the functional components of the supramolecular platform, we can customize the gene carriers for further research on different tissues or cells in vitro or in vivo

A facile modular approach toward multifunctional supramolecular polyplexes for targeting gene delivery

Extensive efforts and numerous methodologies have been explored to develop safe and efficient gene carriers that are capable of overcoming multiple extra- and intracellular barriers during the transfection process. However, it is a great challenge to fabricate a gene carrier system containing multiple functional components. In this work, we propose a facile modular approach to design targeted multifunctional gene delivery systems, which are based on building blocks with pre-defined functions to tackle specific barriers. These building blocks can be rationally combined and self-assemble into an integrated gene delivery system via host-guest interactions. As a proof of concept, three adamantyl-terminated targeting guest modules, adamantyl terminated RGD peptide (Ad-RGD), folate and lactobionic acid terminated PEGs (FA-PEG-Ad and LA-PEG-Ad), were synthesized, characterized, and utilized for post-functionalizing of adamantyl decorated cationic PEI based supramolecular polyplexes (PEI-Ad4/PCD/DNA) through the free CD units of the poly(β-cyclodextran) (PCD) host module. These multifunctional targeting supramolecular polyplexes exhibited enhanced cellular uptake and excellent transfection activity in receptor-positive cells. By modulating the functional components of the supramolecular platform, we can customize the gene carriers for further research on different tissues or cells in vitro or in vivo

Release of model proteins and basic fibroblast growth factor from in situ forming degradable dextran hydrogels

Our previous studies showed that degradable dextran hydrogels are rapidly formed in situ upon mixing aqueous solutions of dextran vinyl sulfone (dex-VS) conjugates and tetrafunctional mercapto poly(ethylene glycol) (PEG-4-SH) by Michael addition. The hydrogel degradation time and storage modulus could be controlled by the degree of vinyl sulfone substitution (DS) and dextran molecular weight. The degradation time could further be adjusted by the spacer between the thioether and the ester bond of the dex-VS conjugates (ethyl vs. propyl, denoted as dex-Et-VS and dex-Pr-VS, respectively). In this paper, the release of three model proteins, i.e. immunoglobulin G (dh = 10.7 nm, IgG), bovine serum albumin (BSA, dh = 7.2 nm) and lysozyme (dh = 4.1 nm), as well as basic fibroblast growth factor (bFGF) from these in situ forming dextran hydrogels is studied. Proteins could be easily loaded into the hydrogels by mixing protein containing solutions of dex-VS and PEG-4-SH. The release of IgG from dex-Et-VS hydrogels followed biphasic release kinetics, with a slow, close to first order release for the first 9 days followed by an accelerated release and over 80% of IgG was released in 12 to 25 days. Interestingly, the release of IgG from dex-Pr-VS hydrogels followed close to zero order kinetics, wherein approximately 95% was released in 21 days. The release of BSA from dex-Pr-VS hydrogels followed biphasic kinetics, with almost first order release followed by close to zero order release. Approximately 75% of the entrapped BSA could be released from dex-Pr-VS hydrogels in 16 days. Dex-Pr-VS hydrogels released 40% of lysozyme in 14 days, with full preservation of the enzymatic activity of the released lysozyme, as determined by bacteria lysis experiments. The release of basic fibroblast growth factor (bFGF) from dex-Pr-VS hydrogels showed first order kinetics, with quantitative release in 28 days. These results show that the in situ forming degradable dextran hydrogels can be used for the controlled release of proteins