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A 60-membered library of vitamin A-functionalized P(MMA-stat-DMAEMA)-b-PPEGMA block copolymers was synthesized by RAFT polymerization. The retinoic acid was coupled to hydroxyl groups present in the hydrophilic PPEGMA block. The polymers were investigated for their ability to encapsulate ribonucleic acids through nanoparticle (NP) formulation using the emulsion/solvent evaporation method. The localization of retinyl in surface-near regions of the NPs was indicated by surface enhanced Raman spectroscopy, and the interaction of the NPs with a retinol binding protein was investigated by an analytical ultracentrifuge. The systematic analysis of the NP library in terms of the encapsulation efficiency of the ribonucleic acids, the toxicity of the NPs, and the cellular uptake helped identifying suitable candidates for cellular internalization studies. The cell uptake was investigated by flow cytometry and fluorescence microscopy and reveals structure dependent uptake behavior of the examined particles.

The introduction of specific targeting units to polymer nanogels usually requires tedious chemical modifications, which limits flexibility in the design of combinatorial approaches. Here, we present a straightforward and versatile method to reversibly introduce various carbohydrate-based targeting units to a pH-sensitive nanogel via host-guest interactions. Glucose-, mannose-, or fructose-modified pillar[5]arenes can adaptably and conveniently be introduced to the surface of the nanogel. Binding studies between these nanogels and the lectin Concanavalin A revealed a high selectivity and strong interaction with only the mannose-modified nanogels. With the addition of other pillar[5]arenes, the interaction can be influenced proving a dynamic exchange of the targeting units. In comparison with common covalent modifications of polymer nanostructures, the presented combination of straightforward precipitation polymerization and supramolecular interactions promises convenient access to adaptable nanostructures for high-throughput screening of targeted delivery systems.

International audience; In the present study, three biodegradable block copolymers composed of a poly(ethylene glycol) block and a copolypeptide block with varying compositions of cationic L-lysine (L-Lys) and hydrophobic benzyl-L-glutamate (Bzl-L-Glu) were designed for gene delivery applications. The polypeptides were synthesized by ring opening polymerization (ROP) and after orthogonal deprotection of Boc-L-Lys side chains, the polymer exhibited an amphiphilic character. To bind or encapsulate plasmid DNA (pDNA), different formulations were investigated: a nanoprecipitation and an emulsion technique using various organic solvents as well as an aqueous pH-controlled formulation method. The complex and nanoparticle (NP) formations were monitored by dynamic light scattering (DLS), and pDNA interaction was shown by gel electrophoresis and subsequent controlled release with heparin. The polypeptides were further tested for their cytotoxicity as well as biodegradability. The complexes and NPs presentingthe most promising size distributions and pDNA binding ability were subsequently evaluated for their transfection efficiency in HEK293T cells. The highest transfection efficiencies were obtained with an aqueous formulation of the polypeptide containing the highest L-Lys content and lowest proportion of hydrophobic, helical structures (P1*), which is therefore a promising candidate for efficient gene delivery by biodegradable gene delivery vectors.

Smart nano-carriers such as micelles, vesicles or nanoparticles constructed from amphiphilic polymers promise a new generation of drug delivery systems featuring localized and controlled release. Keeping the considerable effort for the synthesis of these polymers in mind, supramolecular host–guest interactions represent an interesting alternative to engineer amphiphilic materials with multiple functionalities. Using the known interaction of pillar[5]arenes with aromatic guests such as viologen-derivatives, we designed quasi-block copolymers based on polycaprolactone (PCL) and either the neutral and biocompatible poly(N-acryloyl morpholine) (PNAM-P[5]) or the structurally similar but pH-responsive poly(N-acryloyl-N′-methyl piperazine) (PNAMP-P[5]), which were modified with the pillar[5]arene. Self-assembly experiments in water resulted in the formation of small spherical nanostructures for the methyl viologen-polycaprolactone (viologen-PCL), but surprisingly also for the non-functionalized PCL. However, only the pH-responsive PNAMP-P[5] provided stable structures in the buffer for both cases, while PNAM-P[5] resulted in aggregation. Additional degradation studies revealed that the presence of host–guest complexes could retard the disintegration of the particles at low pH (5.1) in comparison to the particles based on plain PCL, while all structures remained stable at neutral pH value. In combination with their excellent biocompatibility, the presented supramolecular approach to stabilize PCL nanoparticles with pH-responsive polymers pave a convenient way to degradable delivery systems with tailored release profiles.

A dual photo- and pH-responsive spirooxazine-functionalized polymer was synthesized by functionalization of dextran with a spirooxazine derivative (SO-COOH). The functionalized dextran derivatives can form nanoparticles in aqueous medium. Under UV light irradiation, the spirooxazine-functionalized dextran (Dex-SO) nanoparticles isomerize to zwitterionic merocyanine-functionalized dextran (Dex-MC), which leads to aggregation. However, the process is reversible upon irradiation with visible light. Under acidic conditions, the hydrophobic spirooxazine is protonated, and the nanoparticles aggregate or swell at pH values of 5 or 3, respectively. The encapsulation of the hydrophobic fluorescent dye Nile Red as model drug allowed us to gain more information about the structural changes under stimulation of UV light and acid treatment.

The utilization of fluorescent nanoparticles (FNPs), which consist of organic fluorophores embedded into a polymer matrix, seems to be a promising concept for in vivo cancer imaging showing good biocompatibility, biodegradability, and low toxicity of the agents. Polymeric nanoparticles as fluorescent nanocarriers can be systematically designed with regard to the requested task, i.e., specific accumulation in the tumor tissue. Versatile organic fluorophores can be entrapped into polymers with fine-tuned properties, which were synthesized via polymerization techniques. Moreover, the formulation of the nanoparticles can be adjusted, and passive as well as active targeting strategies can be employed. Despite their evident benefits, fluorescent polymeric nanoparticles are still not in clinical application for cancer detection due to a still existing lack of understanding of their in vivo interactions as well as their reproducible production. This review focuses on cancer imaging based on organic dyes and metal-free polymeric fluorescent nanoparticles highlighting recent interesting reports about their design and application as well as their limitations.

The administration of drugs, as a main challenge of pharmaceutical and medicinal applications, has certainly benefited from the application of synthetic polymers. However, despite an enormous effort to develop new materials for drug delivery applications, only few of them have entered the market due to the hurdles of regulation, production, cost efficiency and both industrial’s and patients’ acceptance. In this review, we summarize all these classes of synthetic polymers, which are on the market as well as the latest developments in clinical trials, and describe their application in polymer-drug conjugates, as excipients, in nano-/microscopic and macroscopic drug carriers, as polymeric coatings, or as polymeric drugs. Our intention is to create a link between the underlying chemical structures, the properties of the polymers, and their area of application, where they are often just known by their trade names or abbreviations. In addition selected types of synthetic polymers are highlighted that feature interesting properties and have the potential to make it to the market in future.

A benzoin-derived diol linker was synthesized and used to generate biocompatible polyesters that can be fully decomposed on demand upon UV irradiation. Extensive structural optimization of the linker unit was performed to enable the defined encapsulation of diverse organic compounds in the polymeric structures and allow for a well-controllable polymer cleavage process. Selective tracking of the release kinetics of encapsulated model compounds from the polymeric nano- and microparticle containers was performed by confocal laser scanning microscopy in a proof-of-principle study. The physicochemical properties of the incorporated and released model compounds ranged from fully hydrophilic to fully hydrophobic. The demonstrated biocompatibility of the utilized polyesters and degradation products enables their use in advanced applications, for example, for the smart packaging of UV-sensitive pharmaceuticals, nutritional components, or even in the area of spatially selective self-healing processes.

We synthesized a novel thermoresponsive and pH-degradable polymer, (poly(N-[(2,2-dimethyl-1,3-dioxolane)methyl]acrylamide)), with a pyridinium salt based end group, which can form a host–guest complex with various pillar[5] arenes. This complex formation led to an increase of the LCST of the polymer whereat carboxylate functionalized pillar[5] arenes caused a stronger shift than the respective oligoethylene oxide modified ones. This trend is found to be coherent with the strength of interaction of the respective host and guest, which was analyzed by NMR studies and isothermal titration calorimetry (ITC). Further investigations on this complex revealed that the hydrolysis of the polymer can be accelerated in the presence of the carboxylate based pillar arene under acidic conditions, which was not the case for the oligoethylene oxide modified system or a structurally similar carboxylic acid unit not forming a complex. The host–guest interaction therefore not only represents a versatile approach to tune the solubility behavior of polymers, but also influences pH dependent degradability.

The synthesis of novel polymeric dyes by directly attaching toluidine blue O and MPPD via EDC and CDI coupling is described for polymers with enteric properties [poly(methacrylic acid-co-ethyl acrylate)]. The polymeric dyes are analyzed by SEC and UV/Vis measurements as well as investigated regarding their dissolution and permeation characteristics. Almost no changes between the modified and nonmodified polymer could be observed by conventional drug studies and a self-established method for dissolution rates. Also no influence on the film formation properties was observed by SEM measurements. In vitro toxicity studies showed no increase of toxicity compared to the non modified polymer. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2386–2393

Contains fulltext : 153442.pdf (Publisher’s version ) (Closed access) Polymer-based gene delivery systems have enormous potential in biomedicine, but their efficiency is often limited by poor biocompatibility. Poly(methacrylate)s (PMAs) are an interesting class of polymers which allow to explore structure-activity relationships of polymer functionalities for polyplex formation in oligonucleotide delivery. Here, we synthesized and tested a library of PMA polymers, containing functional groups contributing to the different steps of gene delivery, from oligonucleotide complexation to cellular internalization and endosomal escape. By variation of the molar ratios of the individual building blocks, the physicochemical properties of the polymers and polyplexes were fine-tuned to reduce toxicity as well as to increase activity of the polyplexes. To further enhance transfection efficiency, a cell-penetrating peptide (CPP)-like functionality was introduced on the polymeric backbone. With the ability to synthesize large libraries of polymers in parallel we also developed a workflow for a mid-to-high throughput screening, focusing first on safety parameters that are accessible by high-throughput approaches such as blood compatibility and toxicity towards host cells and only at a later stage on more laborious tests for the ability to deliver oligonucleotides. To arrive at a better understanding of the molecular basis of activity, furthermore, the effect of the presence of heparan sulfates on the surface of host cells was assessed and the mechanism of cell entry and intracellular trafficking investigated for those polymers that showed a suitable pharmacological profile. Following endocytic uptake, rapid endosomal release occurred. Interestingly, the presence of heparan sulfates on the cell surface had a negative impact on the activity of those polyplexes that were sensitive to decomplexation by heparin in solution. In summary, the screening approach identified two polymers, which form polyplexes with high stability and transfection capacity exceeding the one of poly(ethylene imine) also in the presence of serum.

In 2012, the first gene therapy agent was approved by the Europe Medicines Agency leading to increased interest in this research field. Beside viruses, non-viral agents based on lipids or polymers represent aspiring alternatives to deliver the genetic material. Different hurdles have to be overcome depending on the kind of nucleic acid used, where plasmid DNA (pDNA) and small interfering RNA represent the common ones. The main challenge for transfection agents, in particular for pDNA delivery, is the transfer to the cell and into the cell nuclei. Within the group of transfection vesicles, cationic polymers show promising features and variability, as they can be synthesized with tailor-made physical and chemical properties (architectures and functionalisation). In the field of polymer-based gene delivery, the tuning potential of polymers by using different architectures like graft and star-shaped polymers as well as self-assembled block copolymers is immense. In particular, in the last few years numerous new polymer designs showed enhanced transfection properties in combination with good biocompatibility. Furthermore, new insights into the transfection mechanism demonstrated the continuous progress in this field. Polymer architecture influences the polyplex characteristics and the latter has an impact on the transfection mechanism, e.g. the interaction with the cellular membrane depends on the polyplex shape. Moreover, polyplex dissociation can be easily influenced by the polymer chemistry, thus biodegradable linkers lead to well suited polymers with reduced toxicity and high delivery potential, and are also promising for in vivo applications. This review focuses on the influence of polymer architectures for pDNA transfection in vitro, showing recent developments and insights. The theoretical background concerning the biological challenges for cationic polymers and the impact of graft- or star-shaped architectures as well as self-assembled structures will be presented in detail.

In recent years, "high-throughput" (HT) has turned into a keyword in polymer research. In this study, we present a novel HT workflow for the investigation of cationic polymers for gene delivery applications. For this purpose, various poly(ethylene imine)s (PEI) were used as representative vectors and investigated via HT-assays in a 96-well plate format, starting from polyplex preparation up to the examination of the transfection process. In detail, automated polyplex preparation, complex size determination, DNA binding affinity, polyplex stability, cytotoxicity, and transfection efficiency were performed in the well plate format. With standard techniques, investigation of the biological properties of polymers is quite time-consuming, so only a limited number of materials and conditions (such as pH, buffer composition, and concentration) can be examined. The approach described here allows many different polymers and parameters to be tested for transfection properties and cytotoxicity, giving faster insights into structure-activity relationships for biological activity.

A primary amino-functionalized methyl methacrylate-based statistical copolymer is covalently coupled with retinoic acid (RA) and a fluorescent dye (DY590) in order to investigate the feasibility of the RA containing polymeric nanoparticles for Raman imaging studies and to study the possible selectivity of RA for hepatic stellate cells via intravital microscopy. Cationic nanoparticles are prepared by utilizing the nanoprecipitation method using modified polymers. Raman studies show that RA functional nanoparticles can be detectable in all tested cells without any need of additional label. Moreover, intravital microscopy indicates that DY590 is eliminated through the hepatobiliary route but not if used as covalently attached tracing molecule for nanoparticles. However, it is a suitable probe for sensitive detection of polymeric nanoparticles.

The universal importance of iron, its high toxicity, and complex chemistry present a challenge to biological systems in general and to protected compartments in particular. The high mitotic rate and avid mitochondriogenesis of developing male germ cells imply high iron requirements. Yet access to germ cells is tightly regulated by the blood-testis barrier that protects the meiotic and postmeiotic germ cells. To elucidate how iron is supplied to developing male germ cells, we analyzed iron deposition and iron transport proteins in testes of mice with iron overload and with genetic ablation of the iron regulators Hfe and iron regulatory protein 2. Iron accumulated mainly around seminiferous tubules, and only small amounts localized within the seminiferous tubules. The localization and regulation of proteins involved in iron import, storage, and export such as transferrin, transferrin receptor, the divalent metal transporter-1, cytosolic ferritin, and ferroportin strongly support a model of a largely autonomous iron cycle within seminiferous tubules. We show evidence that ferritin secretion from Sertoli cells may play an important role in iron acquisition of primary spermatocytes. During spermatogenic development iron is carried along from primary spermatocytes to spermatids, and from spermatids iron is recycled to the apical compartment of Sertoli cells, which traffic it back to a new generation of spermatocytes. Losses are replenished by the peripheral circulation. Such an internal iron cycle essentially detaches the iron homeostasis within the seminiferous tubule from the periphery and protects developing germ cells from iron fluctuations. This model explains how compartmentalization can optimize cellular and systemic nutrient homeostasis.

The current investigation describes in detail the influence of the polymer molar mass as well as polymer-solvent interactions on the formation of nanoparticles using the nanoprecipitation methodology. For this purpose, a homologous series of poly(methyl methacrylate)s with molar masses ranging from 7,700 to 274,000 g mol−1 was prepared. Subsequently nanoprecipitation was performed in an automated and systematic manner using liquid handling robots and a variation of different initial concentrations of the polymers and solvent/nonsolvent ratios. To elucidate information about the polymer behavior in the solvents used for the nanoprecipitation procedure (acetone, tetrahydrofuran), intrinsic viscosity measurements were performed. The nanoparticle formulations were examined in terms of particle size and size distribution, particle shape as well as zeta-potential. The conditions for the preparation of stable and uniform nanoparticles, regardless of molar mass and hydrodynamic volume of the initial polymer, were determined. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Nanoprecipitation is a facile, mild, and low energy input process for the preparation of polymeric nanoparticles. Basic requirements, as well as common techniques for the self-assembly of non-charged and non-amphiphilic macromolecules into defined nanoparticles are described. At present, the primary focus of polymer nanoprecipitation research lays on poly(lactic acid) (PLA) and its copolymer poly(lactic-co-glycolic acid) (PLGA). This contribution thus emphasises on polymers beyond PLA systems, such as common industrial- or tailored lab-made polymers, and their ability to form well-defined, functional nanoparticles for a variety of applications now and in the past two centuries. Moreover, in combination with high-throughput devices such as microfluidics, pipetting robots, inkjet printers, and automated analytical instrumentation, the abilities of nanoprecipitation may broaden tremendously with significant effects on new applications.

The pharmaceutically important polymer P(MAA-r-MMA)(1:2) (EUDRAGIT(®) S100) was investigated concerning its behavior to form nanoparticles via nanoprecipitation. The particles obtained were characterized regarding their size, shape, and characteristics using DLS, SEM, and AUC. Furthermore, the P(MAA-r-MMA)(1:2) copolymer was modified with different markers in order to achieve polymer-based nanocarrier systems, which are detectable and may be useful for controlled drug delivery devices to monitor the drug pathways. The particles were labeled by physical entrapment as well as by covalent attachment of various markers, e.g., radicals, fluorescent-, and near-infrared dyes, to the polymer. Physical entrapment of radicals into the polymeric units was performed by co-nanoprecipitation of P(MAA-r-MMA)(1:2) and a radical marker. By means of covalent binding of the markers to the polymer, a stable and more defined labeling of the particles was also performed, leading only to a low degree of modification of the pharmaceutical polymer. After nanoprecipitation, the resulting labeled particles were characterized by SEM and DLS, whereas their biocompatibility was proven by in vitro studies. In order to ensure the possibility of detection of the particles inside the body for drug delivery-, sensor-, and imaging applications, the polymeric carriers were also investigated by electron spin resonance, fluorescence, as well as near-infrared spectroscopy.

We present the synthesis of polylactide by ring-opening polymerization using a luminescent iridium(III) complex acting as initiator. The polymer was formulated into nanoparticles, which were taken up by HEK-293 cells. We could show that the particles provided an appropriate contrast in both superresolution fluorescence and electron microscopy, and, moreover, are non-toxic, in contrast to the free iridium complex.

Low molar mass linear poly(ethylene imine)s (lPEI) were grafted onto dextran via different synthesis routes aiming at the elucidation of structure-property relationships of dextran-graft-linear poly(ethylene imine) (dex-g-lPEI) conjugates for gene delivery applications. Beside the molar mass of well-defined lPEIs and the linker unit, also the amount of lPEI in the polymeric vectors was varied. The synthesized dextran modifications were characterized regarding their chemical structure and showed enhanced complexation and stabilization of DNA against enzymatic degradation. The transfection efficiency of dex-g-lPEIs was increased compared to unmodified lPEI and revealed a dependency of the used linking strategy. All complexes of DNA and dex-g-lPEIs were found to be nontoxic, but the synthesis route showed a strong influence on the aggregation of red blood cells. In conclusion, the linking strategy of lPEI to dextran has a significant impact on the physicochemical characteristics of DNA/polymer complexes, the biocompatibility as well as the transfection efficiency.

Poly(ethylene imine)s (PEIs) are widely used in different applications, but most extensively investigated as non-viral vector systems. The high ability of cationic PEIs to complex and condense negatively charged DNA and RNA combined with their inherent proton sponge behavior accounts for the excellent efficiency in gene delivery. Further chemical modifications of the polymer expand the application potential, primarily aiming at increased transfection efficiency, cell selectivity and reduced cytotoxicity. Improvements in the synthesis of tailor-made PEIs in combination with new in-depth analytical techniques offer the possibility to produce highly purified polymers with defined structures. The contemporary strategies towards linear and branched poly(ethylene imine)s with modified surface characteristics, PEI-based copolymers as well as conjugates with bioactive molecules will be discussed. In this regard, the versatile branched PEIs have been successfully modified in a statistical manner, whereas the linear counterparts open avenues to design and synthesize well-defined architectures, in order to exploit their high potential in gene delivery.

colloidal preceramic materials, Archimedean nanolattices, phosphorescent Ir(III) complexes, self-assembly of a dendritic reactor, synthesis of a heterometallic polymer, synthesis of coordination polymers, preparation of photoluminescent π-conjugated polymers, triazole-pyridine-containing polymers, platinum diketonate-containing polymers, the fabrication of functional nanofi bers, and boron-containing block copolymers for tumor imaging. Utilitarian properties of the investigated polymers include organic batteries, oxygen-resistant phosphorescence, photocatalysis, molecular self-assembly, unimolecular micellar encapsulation, heparin sensing and cellular imaging, and other fascinating topics. Hopefully the journal readership will be sparked to take up the fundamental and applied challenges related to these topics. Enjoy reading this issue! A Pandora’s Box of New Materials— Metallopolymers