Improving Gene Delivery: Synergy between Alkyl Chain Length and Lipoic Acid for PDMAEMA Hydrophobic Copolymers

In the field of gene delivery, hydrophobic cationic copolymers hold great promise. They exhibit improved performance by effectively protecting genetic material from serum interactions while facilitating interactions with cellular membranes. However, managing cytotoxicity remains a significant challenge, prompting an investigation into suitable hydrophobic components. A particularly encouraging approach involves integrating nutrient components, like lipoic acid, which is known for its antioxidant properties and diverse cellular benefits such as cellular metabolism and growth. In this study, a copolymer library comprising 2-(dimethylamino)ethyl methacrylate (DMAEMA) and lipoic acid methacrylate (LAMA), combined with either n-butyl methacrylate (nBMA), ethyl methacrylate (EMA), or methyl methacrylate (MMA), is synthesized. This enables to probe the impact of lipoic acid incorporation while simultaneously exploring the influence of pendant acyclic alkyl chain length. The inclusion of lipoic acid results in a notable boost in transfection efficiency  while maintaining low cytotoxicity. Interestingly, higher levels of transfection efficiency are achieved in the presence of nBMA, EMA, or MMA. However, a positive correlation between pendant acyclic alkyl chain length and cytotoxicity is observed. Consequently, P(DMAEMA-co-LAMA-co-MMA), emerges as a promising candidate. This is attributed to the optimal combination of low cytotoxic MMA and transfection-boosting LAMA, highlighting the crucial synergy between LAMA and MMA.

Vitamin B3 Containing Polymers for Nanodelivery

Polymeric nanoparticles (NPs) with an integrated dual delivery system enable the controlled release of bioactive molecules and drugs, providing therapeutic advantages. Key design targets include high biocompatibility, cellular uptake, and encapsulating efficiency. In this study, a polymer library derived from niacin, also known as vitamin B3 is synthesized. The library comprises poly(2-(acryloyloxy)ethyl nicotinate) (PAEN), poly(2-acrylamidoethyl nicotinate) (PAAEN), and poly(N-(2-acrylamidoethyl)nicotinamide) (PAAENA), with varying hydrophilicity in the backbone and pendant group linker. All polymers are formulated, and those with increased hydrophobicity yield NPs with homogeneous spherical distribution and diameters below 150 nm, as confirmed by scanning electron microscopy and dynamic light scattering. Encapsulation studies utilizing a model drug, neutral lipid orange (NLO), reveal the influence of polymer backbone on encapsulation efficiency. Specifically, efficiencies of 46% and 96% are observed with acrylate and acrylamide backbones, respectively. Biological investigations showed that P(AEN) and P(AAEN) NPs are non-toxic up to 300 µg mL-1, exhibit superior cellular uptake, and boost cell metabolic activity. The latter is attributed to the cellular release of niacin, a precursor to nicotinamide adenine dinucleotide (NAD), a central coenzyme in metabolism. The results underline the potential of nutrient-derived polymers as pro-nutrient and drug-delivery materials.

Optimization of Mixed Micelles Based on Oppositely Charged Block Copolymers by Machine Learning for Application in Gene Delivery

The COVID-19 mRNA vaccines represent a milestone in developing non-viral gene carriers, and their success highlights the crucial need for continued research in this field to address further challenges. Polymer-based delivery systems are particularly promising due to their versatile chemical structure and convenient adaptability, but struggle with the toxicity-efficiency dilemma. Introducing anionic, hydrophilic, or "stealth" functionalities represents a promising approach to overcome this dilemma in gene delivery. Here, two sets of diblock terpolymers are created comprising hydrophobic poly(n-butyl acrylate) (PnBA), a copolymer segment made of hydrophilic 4-acryloylmorpholine (NAM), and either the cationic 3-guanidinopropyl acrylamide (GPAm) or the 2-carboxyethyl acrylamide (CEAm), which is negatively charged at neutral conditions. These oppositely charged sets of diblocks are co-assembled in different ratios to form mixed micelles. Since this experimental design enables countless mixing possibilities, a machine learning approach is applied to identify an optimal GPAm/CEAm ratio for achieving high transfection efficiency and cell viability with little resource expenses. After two runs, an optimal ratio to overcome the toxicity-efficiency dilemma is identified. The results highlight the remarkable potential of integrating machine learning into polymer chemistry to effectively tackle the enormous number of conceivable combinations for identifying novel and powerful gene transporters.

Tailoring Gene Transfer Efficacy through the Arrangement of Cationic and Anionic Blocks in Triblock Copolymer Micelles

The arrangement of charged segments in triblock copolymer micelles affects the gene delivery potential of polymeric micelles and can increase the level of gene expression when an anionic segment is incorporated in the outer shell. Triblock copolymers were synthesized by RAFT polymerzation with narrow molar mass distributions and assembled into micelles with a hydrophobic core from poly(n-butyl acrylate). The ionic shell contained either (i) an anionic segment followed by a cationic segment (HAC micelles) or (ii) a cationic block followed by an anionic block (HCA micelles). The pH-responsive anionic block contained 2-carboxyethyl acrylamide (CEAm), while the cationic block comprised 3-guanidinopropyl acrylamide (GPAm). Increasing the molar content of CEAm in HAC and HCA micelles from 6 to 13 mol % improved cytocompatibility and the endosomal escape property, while the HCA micelle with the highest mol % of anionic charges in the outer shell exhibited the highest gene expression. It became evident that improved membrane interaction of the best performing HCA micelle contributed to achieving high gene expression.

Stimuli-Responsive Non-viral Nanoparticles for Gene Delivery

Considering nucleic acids as the language of life and the genome as the instruction manual of cells, their targeted modulation promises great opportunities in treating and healing diseases. In addition to viral gene transfer, the overwhelming power of non-viral mRNA-based vaccines is driving the development of novel gene transporters. Thereby, various nucleic acids such as DNA (pDNA) or RNA (mRNA, siRNA, miRNA, gRNA, or ASOs) need to be delivered, requiring a transporter due to their high molar mass and negative charge in contrast to classical agents. This chapter presents the specific biological hurdles for using nucleic acids and shows how new materials can overcome these.

Modification of Branched Poly(ethylene imine) with d-Fructose for Selective Delivery of siRNA into Human Breast Cancer Cells

Branched poly(ethylene imine) (bPEI) is frequently used in RNA interference (RNAi) experiments as a cationic polymer for the delivery of small interfering RNA (siRNA) because of its ability to form stable polyplexes that facilitate siRNA uptake. However, the use of bPEI in gene delivery is limited by its cytotoxicity and a need for target specificity. In this work, bPEI is modified with d-fructose to improve biocompatibility and target breast cancer cells through the overexpressed GLUT5 transporter. Fructose-substituted bPEI (Fru-bPEI) is accessible in three steps starting from commercially available protected fructopyranosides and bPEI. Several polymers with varying molecular weights, degrees of substitution, and linker positions on d-fructose (C1 and C3) are synthesized and characterized with NMR spectroscopy, size exclusion chromatography, and elemental analysis. In vitro biological screenings show significantly reduced cytotoxicity of 10 kDa bPEI after fructose functionalization, specific uptake of siRNA polyplexes, and targeted knockdown of green fluorescent protein (GFP) in triple-negative breast cancer cells (MDA-MB-231) compared to noncancer cells (HEK293T).

Efficient Transfection via an Unexpected Mechanism by Near Neutral Polypiperazines with Tailored Response to Endosomal pH

Cationic pH-responsive polymers promise to overcome critical challenges in cellular delivery. Ideally, the polymers become selectively charged along the endosomal pathway disturbing only the local membrane and avoiding unintended interactions or cytotoxic side effects at physiological conditions. Polypiperazines represent a novel, hydrophilic class of pH-responsive polymers whose response can be tuned within the relevant pH range (5-7.4). The authors discovered that the polypiperazines are effectively binding plasmid DNA (pDNA) and demonstrate high efficiency in transfection. By design of experiments (DoE), a wide parameter space (pDNA and polymer concentration) is screened to identify the range of effective concentrations for transfection. An isopropyl modified polypiperazine is highly efficient over a wide range of concentrations outperforming linear polyethylenimine (l-PEI, 25 kDa) in regions of low N*/P ratios. A quantitative polymerase chain reaction (qPCR) surprisingly revealed that the pDNA within the piperazine-based polyplexes can be amplified in contrast to polyplexes based on l-PEI. The pDNA must therefore be more accessible and bound differently than for other known transfection polymers. Considering the various opportunities to further optimize their structure, polypiperazines represent a promising platform for designing effective soluble polymeric vectors, which are charge-neutral at physiological conditions.

Efficient Gene Delivery of Tailored Amphiphilic Polypeptides by Polyplex Surfing

Within this study, an amphiphilic and potentially biodegradable polypeptide library based on poly[(4-aminobutyl)-l-glutamine-stat-hexyl-l-glutamine] [P(AB-l-Gln-stat-Hex-l-Gln)] was investigated for gene delivery. The influence of varying proportions of aliphatic and cationic side chains affecting the physicochemical properties of the polypeptides on transfection efficiency was investigated. A composition of 40 mol% Hex-l-Gln and 60 mol % AB-l-Gln (P3) was identified as best performer over polypeptides with higher proportions of protonatable monomers. Detailed studies of the transfection mechanism revealed the strongest interaction of P3 with cell membranes, promoting efficient endocytic cell uptake and high endosomal release. Spectrally, time-, and z-resolved fluorescence microscopy further revealed the crucial role of filopodia surfing in polyplex-cell interaction and particle internalization in lamellipodia regions, followed by rapid particle transport into cells. This study demonstrates the great potential of polypeptides for gene delivery. The amphiphilic character improves performance over cationic homopolypeptides, and the potential biodegradability is advantageous toward other synthetic polymeric delivery systems.

Tracking the Endosomal Escape: A Closer Look at Calcein and Related Reporters

Crossing the cellular membrane and delivering active pharmaceuticals or biologicals into the cytosol of cells is an essential step in the development of nanomedicines. One of the most important intracellular processes regarding the cellular uptake of biologicals is the endolysosomal pathway. Sophisticated nanocarriers have been developed overcoming a major hurdle, the endosomal entrapment, and delivering their cargo to the required site of action. In parallel, in vitro assays have been established analyzing the performance of these nanocarriers. Among them, the release of the membrane-impermeable dye calcein has become a popular and straightforward method. It is accessible for most researchers worldwide, allows for rapid conclusions about the release potential, and enables the study of release mechanisms. This review is intended to provide an overview and guidance for scientists applying the calcein release assay. It comprises a survey of several applications in the study of endosomal escape, considerations of potential pitfalls, challenges and limitations of the assay, and a brief summary of complementary methods. Based on this review, we hope to encourage further research groups to take advantage of the calcein release assay for their own purposes and help to create a database for more efficient cross-correlations between nanocarriers. This article is protected by copyright. All rights reserved.

pH-sensitive packaging of cationic particles by an anionic block copolymer shell

Cationic non-viral vectors show great potential to introduce genetic material into cells, due to their ability to transport large amounts of genetic material and their high synthetic versatility. However, designing materials that are effective without showing toxic effects or undergoing non-specific interactions when applied systemically remains a challenge. The introduction of shielding polymers such as polyethylene glycol (PEG) can enhance biocompatibility and circulation time, however, often impairs transfection efficiency. Herein, a multicomponent polymer system is introduced, based on cationic and hydrophobic particles (P(nBMA₄₆-co-MMA₄₇-co-DMAEMA₉₀), (PBMD)) with high delivery performance and a pH-responsive block copolymer (poly((N-acryloylmorpholine)-b-(2-(carboxy)ethyl acrylamide)) (P(NAM₇₂-b-CEAm₇₄), PNC)) as shielding system, with PNAM as alternative to PEG. The pH-sensitive polymer design promotes biocompatibility and excellent stability at extracellular conditions (pH 7.4) and also allows endosomal escape and thus high transfection efficiency under acidic conditions. PNC shielded particles are below 200 nm in diameter and showed stable pDNA complexation. Further, interaction with human erythrocytes at extracellular conditions (pH 7.4) was prevented, while acidic conditions (pH 6) enabled membrane leakage. The particles demonstrate transfection in adherent (HEK293T) as well as difficult-to-transfect suspension cells (K-562), with comparable or superior efficiency compared to commercial linear poly(ethylenimine) (LPEI). Besides, the toxicity of PNC-shielded particles was significantly minimized, in particular in K-562 cells and erythrocytes. In addition, a pilot in vivo experiment on bone marrow blood cells of mice that were injected with PNC-shielded particles, revealed slightly enhanced cell transfection in comparison to naked pDNA. This study demonstrates the applicability of cationic hydrophobic polymers for transfection of adherent and suspension cells in culture as well as in vivo by co-formulation with pH-responsive shielding polymers, without substantially compromising transfection performance.

Core-crosslinked, temperature- and pH-responsive micelles: design, physicochemical characterization, and gene delivery application

Stimuli-responsive block copolymer micelles can provide tailored properties for the efficient delivery of genetic material. In particular, temperature- and pH-responsive materials are of interest, since their physicochemical properties can be easily tailored to meet the requirements for successful gene delivery. Within this study, a stimuli-responsive micelle system for gene delivery was designed based on a diblock copolymer consisting of poly(N,N-diethylacrylamide) (PDEAm) as a temperature-responsive segment combined with poly(aminoethyl acrylamide) (PAEAm) as a pH-responsive, cationic segment. Upon temperature increase, the PDEAm block becomes hydrophobic due to its lower critical solution temperature (LCST), leading to micelle formation. Furthermore, the monomer 2-(pyridin-2-yldisulfanyl)ethyl acrylate (PDSAc) was incorporated into the temperature-responsive PDEAm building block enabling disulfide crosslinking of the formed micelle core to stabilize its structure regardless of temperature and dilution. The cloud points of the PDEAm block and the diblock copolymer were investigated by turbidimetry and fluorescence spectroscopy. The temperature-dependent formation of micelles was analyzed by dynamic light scattering (DLS) and elucidated in detail by an analytical ultracentrifuge (AUC), which provided detailed insights into the solution dynamics between polymers and assembled micelles as a function of temperature. Finally, the micelles were investigated for their applicability as gene delivery vectors by evaluation of cytotoxicity, pDNA binding, and transfection efficiency using HEK293T cells. The investigations showed that core-crosslinking resulted in a 13-fold increase in observed transfection efficiency. Our study presents a comprehensive investigation from polymer synthesis to an in-depth physicochemical characterization and biological application of a crosslinked micelle system including stimuli-responsive behavior.

Self-assembled PEGylated amphiphilic polypeptides for gene transfection

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 presenting the 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.

The impact of anionic polymers on gene delivery: how composition and assembly help evading the toxicity-efficiency dilemma

Cationic polymers have been widely studied for non-viral gene delivery due to their ability to bind genetic material and to interact with cellular membranes. However, their charged nature carries the risk of increased cytotoxicity and interaction with serum proteins, limiting their potential in vivo application. Therefore, hydrophilic or anionic shielding polymers are applied to counteract these effects. Herein, a series of micelle-forming and micelle-shielding polymers were synthesized via RAFT polymerization. The copolymer poly[(n-butyl acrylate)-b-(2-(dimethyl amino)ethyl acrylamide)] (P(nBA-b-DMAEAm)) was assembled into cationic micelles and different shielding polymers were applied, i.e., poly(acrylic acid) (PAA), poly(4-acryloyl morpholine) (PNAM) or P(NAM-b-AA) block copolymer. These systems were compared to a triblock terpolymer micelle comprising PAA as the middle block. The assemblies were investigated regarding their morphology, interaction with pDNA, cytotoxicity, transfection efficiency, polyplex uptake and endosomal escape. The naked cationic micelle exhibited superior transfection efficiency, but increased cytotoxicity. The addition of shielding polymers led to reduced toxicity. In particular, the triblock terpolymer micelle convinced with high cell viability and no significant loss in efficiency. The highest shielding effect was achieved by layering micelles with P(NAM-b-AA) supporting the colloidal stability at neutral zeta potential and completely restoring cell viability while maintaining moderate transfection efficiencies. The high potential of this micelle-layer-combination for gene delivery was illustrated for the first time.

Correlation between Protonation of Tailor-Made Polypiperazines and Endosomal Escape for Cytosolic Protein Delivery

Responsive polymers, which become protonated at decreasing pH, are considered a milestone in the development of synthetic cell entry vectors. Exact correlations between their properties and their ability to escape the endosome, however, often remain elusive due to hydrophobic interactions or limitations in the design of water-soluble materials with suitable basicity. Here, we present a series of well-defined, hydrophilic polypiperazines, where systematic variation of the amino moiety facilitates an unprecedented fine-tuning of the basicity or pK_a value within the physiologically relevant range (pH 6-7.4). Coincubation of HEK 293T cells with various probes, including small fluorophores or functioning proteins, revealed a rapid increase of endosomal release for polymers with pK_a values above 6.5 or 7 in serum-free or serum-containing media, respectively. Similarly, cytotoxic effects became severe at increased pK_a values (>7). Although the window for effective transport appears narrow, the discovered correlations offer a principal guideline for the design of effective polymers for endosomal escape.

Improved gene delivery to K-562 leukemia cells by lipoic acid modified block copolymer micelles

Although there has been substantial progress in the research field of gene delivery, there are some challenges remaining, e.g. there are still cell types such as primary cells and suspension cells (immune cells) known to be difficult to transfect. Cationic polymers have gained increasing attention due to their ability to bind, condense and mask genetic material, being amenable to scale up and highly variable in their composition. In addition, they can be combined with further monomers exhibiting desired biological and chemical properties, such as antioxidative, pH- and redox-responsive or biocompatible features. By introduction of hydrophobic monomers, in particular as block copolymers, cationic micelles can be formed possessing an improved chance of transfection in otherwise challenging cells. In this study, the antioxidant biomolecule lipoic acid, which can also be used as crosslinker, was incorporated into the hydrophobic block of a diblock copolymer, poly{[2-(dimethylamino)ethyl methacrylate]101-b-[n-(butyl methacrylate)124-co-(lipoic acid methacrylate)22]} (P(DMAEMA101-b-[nBMA124-co-LAMA22])), synthesized by RAFT polymerization and assembled into micelles (LAMA-mic). These micelles were investigated regarding their pDNA binding, cytotoxicity mechanisms and transfection efficiency in K-562 and HEK293T cells, the former representing a difficult to transfect, suspension leukemia cell line. The LAMA-mic exhibited low cytotoxicity at applied concentrations but demonstrated superior transfection efficiency in HEK293T and especially K-562 cells. In-depth studies on the transfection mechanism revealed that transfection efficiency in K-562 cells does not depend on the specific oncogenic fusion gene BCR-ABL alone. It is independent of the cellular uptake of polymer-pDNA complexes but correlates with the endosomal escape of the LAMA-mic. A comparison of the transfection efficiency of the LAMA-mic with structurally comparable micelles without lipoic acid showed that lipoic acid is not solely responsible for the superior transfection efficiency of the LAMA-mic. More likely, a synergistic effect of the antioxidative lipoic acid and the micellar architecture was identified. Therefore, the incorporation of lipoic acid into the core of hydrophobic-cationic micelles represents a promising tailor-made transfer strategy, which can potentially be beneficial for other difficult to transfect cell types.

Solely aqueous formulation of hydrophobic cationic polymers for efficient gene delivery

Cationic polymers are promising gene delivery vectors due to their ability to bind and protect genetic material. The introduction of hydrophobic moieties into cationic polymers can further improve the vector efficiency, but common formulations of hydrophobic polymers involve harsh conditions such as organic solvents, impairing intactness and loading efficiency of the genetic material. In this study, a mild, aqueous formulation method for the encapsulation of high amounts of genetic material is presented. A well-defined pH-responsive hydrophobic copolymer, i.e. poly((n-butylmethacrylate)-co-(methylmethacrylate)-co-(2-(dimethylamino) ethylmethacrylate)), (PBMD) was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. Exploiting the pH-dependent solubility behavior of the polymer, stable pDNA loaded nanoparticles were prepared and characterized using analytical ultracentrifugation (AUC), cryo-transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS). This novel formulation approach showed high transfection efficiencies in HEK293T cells, while requiring 5- to 10-fold less pDNA compared to linear polyethylenimine (LPEI), in particular at short incubation times and in serum-containing media. Furthermore, the formulation was successfully adopted for siRNA and mRNA encapsulation and the commercially approved polymer Eudragit® E(PO/100). Overall, the aqueous formulation approach, accompanied by a tailor-made hydrophobic polymer and detailed physicochemical and application studies, led to improved gene delivery vectors with high potential for further applications.

Formulation of Liver-Specific PLGA-DY-635 Nanoparticles Loaded with the Protein Kinase C Inhibitor Bisindolylmaleimide I

Bisindolylmaleimide I (BIM-I) is a competitive pan protein kinase C inhibitor with anti-inflammatory and anti-metastatic properties, suggested to treat inflammatory diseases and various cancer entities. However, despite its therapeutic potential, BIM-I has two major drawbacks, i.e., it has a poor water solubility, and it binds the human ether-à-go-go-related gene (hERG) ion channels, potentially causing deadly arrhythmias. In this case, a targeted delivery of BIM-I is imperative to minimize peripheral side effects. To circumvent these drawbacks BIM-I was encapsulated into nanoparticles prepared from poly(lactic-co-glycolic acid) (PLGA) functionalized by the near-infrared dye DY-635. DY-635 served as an active targeting moiety since it selectively binds the OATP1B1 and OATP1B3 transporters that are highly expressed in liver and cancer cells. PLGA-DY-635 (BIM-I) nanoparticles were produced by nanoprecipitation and characterized using dynamic light scattering, analytical ultracentrifugation, and cryogenic transmission electron microscopy. Particle sizes were found to be in the range of 20 to 70 nm, while a difference in sizes between the drug-loaded and unloaded particles was observed by all analytical techniques. In vitro studies demonstrated that PLGA-DY-635 (BIM-I) NPs prevent the PKC activation efficiently, proving the efficacy of the inhibitor after its encapsulation, and suggesting that BIM-I is released from the PLGA-NPs. Ultimately, our results present a feasible formulation strategy that improved the cytotoxicity profile of BIM-I and showed a high cellular uptake in the liver as demonstrated in vivo by intravital microscopy investigations.

Tuning of endosomal escape and gene expression by functional groups, molecular weight and transfection medium: a structure-activity relationship study

The use of genetic material by non-viral transfer systems is still in its initial stages, but there are high expectations for the development of targeted therapies. However, nucleic acids cannot enter cells without help, they must be well protected to prevent degradation and overcome a variety of biological barriers, the endosomal barrier being one of the greatest cellular challenges. Herein, the structure-property-relationship was investigated in detail, using well-defined polymers. Polyacrylamides were synthesized via RAFT polymerization resulting in a polymer library of (i) different cationic groups as aminoethyl acrylamide (AEAm), dimethylaminoethyl acrylamide (DMAEAm), dimethylaminopropyl acrylamide (DMAPAm) and guanidinopropyl acrylamide (GPAm); (ii) different degree of polymerization; and investigated (iii) in different cell culture settings. The influence of molar mass and cationic moiety on complex formation with pDNA, cytotoxicity and transfection efficiency of the polymers were investigated. The systematic approach identified a pH-independent guanidinium-containing homopolymer (PGPAm₈₉) as the polymer with the highest transfection efficiency and superior endosomal release under optimal conditions. Since PGPAm₈₉ is not further protonated inside endosomes, common escape theories appear unsuitable. Therefore, the interaction with bis(monoacryloylglycerol)phosphate, a lipid specific for endosomal vesicles, was investigated. Our research suggests that the interactions between amines and lipids may be more relevant than anticipated.

Cell-Penetrating, Peptide-Based RAFT Agent for Constructing Penetration Enhancers

Peptide-polymer conjugates represent a promising class of compounds that can be used to overcome some of the limitations associated with peptides intended for therapeutic and diagnostic applications. The efficient generation of well-defined peptide/protein-polymer conjugates can promote the development of the design and synthesis of functional drugs and gene delivery platforms. In this research, a sequence defined cell penetrating peptide (i.e., Transportan 10 (TP 10))-based chain transfer agent (TP-CTA) was designed and synthesized in an automated peptide synthesizer. Thereafter, amphiphilic block copolymers poly[oligo(ethylene glycol) methyl ether acrylate]-b-poly(n-butyl acrylate) (TP-POEGA-b-PBA) were synthesized using the TP-CTA via reversible addition-fragmentation chain transfer (RAFT) polymerization. Circular dichroism (CD) spectroscopy confirmed the preservation of α-helix structure of TP 10, which is crucial for its bioactivity. Transmission electron microscopy (TEM) revealed the formation of self-assembled rod-like and vesicle nanostructures in an aqueous environment. Finally, the obtained peptide-conjugated block copolymers were demonstrated to be effective compounds for cell penetration. This method opens up a way for accessing peptide-polymer conjugates with cell-penetrating abilities.

Improved Bioactivity of the Natural Product 5-Lipoxygenase Inhibitor Hyperforin by Encapsulation into Polymeric Nanoparticles

Hyperforin, a highly hydrophobic prenylated acylphloroglucinol from the medical plant St. John's Wort, possesses anti-inflammatory properties and suppresses the formation of proinflammatory leukotrienes by inhibiting the key enzyme 5-lipoxygenase (5-LO). Despite its strong effectiveness and the unique molecular mode of interference with 5-LO, the high lipophilicity of hyperforin hampers its efficacy in vivo and, thus, impairs its therapeutic value, especially because of poor water solubility and strong plasma (albumin) protein binding. To overcome these hurdles that actually apply to many other hydrophobic 5-LO inhibitors, we have encapsulated hyperforin into nanoparticles (NPs) consisting of acetalated dextran (AcDex) to avoid plasma protein binding and thus improve its cellular supply under physiologically relevant conditions. Encapsulated hyperforin potently suppressed 5-LO activity in human neutrophils, but it failed to interfere with 5-LO activity in a cell-free assay, as expected. In the presence of human serum albumin (HSA), hyperforin was unable to inhibit cellular 5-LO activity, seemingly because of strong albumin binding. However, when encapsulated into NPs, hyperforin caused strong inhibition of 5-LO activity in the presence of HSA. Together, encapsulation of the highly hydrophobic hyperforin as a representative of lipophilic 5-LO inhibitors into AcDex-based NPs allows for efficient inhibition of 5-LO activity in neutrophils in the presence of albumin because of effective uptake and circumvention of plasma protein binding.

Beyond Gene Transfection with Methacrylate-Based Polyplexes-The Influence of the Amino Substitution Pattern

Methacrylate-based polymers represent promising nonviral gene delivery vectors, since they offer a large variety of polymer architectures and functionalities, which are beneficial for specific demands in gene delivery. In combination with controlled radical polymerization techniques, such as the reversible addition-fragmentation chain transfer polymerization, the synthesis of well-defined polymers is possible. In this study we prepared a library of defined linear polymers based on (2-aminoethyl)-methacrylate (AEMA), N-methyl-(2-aminoethyl)-methacrylate (MAEMA), and N,N-dimethyl-(2-aminoethyl)-methacrylate (DMAEMA) monomers, bearing pendant primary, secondary, and tertiary amino groups, and investigated the influence of the substitution pattern on their gene delivery capability. The polymers and the corresponding plasmid DNA complexes were investigated regarding their physicochemical characteristics, cytocompatibility, and transfection performance. The nonviral transfection by methacrylate-based polyplexes differs significantly from poly(ethylene imine)-based polyplexes, as a successful transfection is not affected by the buffer capacity. We observed that polyplexes containing a high content of primary amino groups (AEMA) offered the highest transfection efficiency, whereas polyplexes bearing tertiary amino groups (DMAEMA) exhibited the lowest transfection efficiency. Further insights into the uptake and release mechanisms could be identified by fluorescence and transmission electron microscopy, emphasizing the theory of membrane-pore formation for the time-efficient endosomal release of methacrylate-based vectors.

The Power of Shielding: Low Toxicity and High Transfection Performance of Cationic Graft Copolymers Containing Poly(2-oxazoline) Side Chains

We show the potential of oligo(2-ethyl-2-oxazoline) (Ox_n)-shielded graft copolymers of (2-aminoethyl)-methacrylate and N-methyl-(2-aminoethyl)-methacrylate for pDNA delivery in HEK cells. For the effect of grafting density and side chain length concerning improved transfection properties through the concept of shielding to be investigated, copolymers were synthesized via the macromonomer method using a combination of cationic ring opening polymerization and reversible addition-fragmentation chain transfer polymerization to vary the degree of grafting (DG = 10 and 30%) as well as the side chain degree of polymerization (DP = 5 and 20). Investigations of the polyplex formation, in vitro flow cytometry, and confocal laser scanning microscopy measurements on the copolymer library revealed classical shielding properties of the Ox side chains, including highly reduced cytotoxicity and a partial decrease in transfection efficiency, as also reported for polyethylene glycol shielding. In terms of the transfection efficiency, the best performing copolymers (A- g-Ox₅(10) and M- g-Ox₅(10)) revealed equal or better performances compared to those of the corresponding homopolymers. In particular, the graft copolymers with low DG and side chain DP transfected well with over 10-fold higher IC₅₀ values. In contrast, a DG of 30% resulted in a loss of transfection efficiency due to missing ability for endosomal release, and a side chain DP of 20 hampered the cellular uptake.

The great escape: how cationic polyplexes overcome the endosomal barrier

Endo-lysosomal escape strategies of cationic polymer-mediated gene delivery at a glance.

d-Fructose-Decorated Poly(ethylene imine) for Human Breast Cancer Cell Targeting

The high affinity of GLUT5 transporter for d-fructose in breast cancer cells has been discussed intensely. In this contribution, high molar mass linear poly(ethylene imine) (LPEI) is functionalized with d-fructose moieties to combine the selectivity for the GLUT5 transporter with the delivery potential of PEI for genetic material. The four-step synthesis of a thiol-group bearing d-fructose enables the decoration of a cationic polymer backbone with d-fructose via thiol-ene photoaddition. The functionalization of LPEI is confirmed by 2D NMR techniques, elemental analysis, and size exclusion chromatography. Importantly, a d-fructose decoration of 16% renders the polymers water-soluble and eliminates the cytotoxicity of PEI in noncancer L929 cells, accompanied by a reduced unspecific cellular uptake of the genetic material. In contrast, the cytotoxicity as well as the cell specific uptake is increased for triple negative MDA-MB-231 breast cancer cells. Therefore, the introduction of d-fructose shows superior potential for cell targeting, which can be assumed to be GLUT5 dependent.

Mission ImPOxable – or the unknown utilization of non-toxic poly(2-oxazoline)s as cryoprotectants and surfactants at the same time

Polymeric nanoparticles are produced using hydrophilic poly(2-oxazoline)s (P(Ox)s) as particle stabilizers during preparation, purification and lyophilization as an all-in-one system.

3rd generation poly(ethylene imine)s for gene delivery

In this study, a series of high molar mass poly(2-oxazoline)-based copolymers was synthesized, introducing 2-ethyl-2-oxazoline, ethylene imine, and primary amine bearing monomer units representing a new generation of PEI.

Fluorescent amphiphilic heterografted comb polymers comprising biocompatible PLA and PEtOx side chains

The comb polymers are synthesized in three independent steps by ROP, CROP, and RAFT.

Comparison of the uptake of methacrylate-based nanoparticles in static and dynamic in vitro systems as well as in vivo

Polymer-based nanoparticles are promising drug delivery systems allowing the development of new drug and treatment strategies with reduced side effects. However, it remains a challenge to screen for new and effective nanoparticle-based systems in vitro. Important factors influencing the behavior of nanoparticles in vivo cannot be simulated in screening assays in vitro, which still represent the main tools in academic research and pharmaceutical industry. These systems have serious drawbacks in the development of nanoparticle-based drug delivery systems, since they do not consider the highly complex processes influencing nanoparticle clearance, distribution, and uptake in vivo. In particular, the transfer of in vitro nanoparticle performance to in vivo models often fails, demonstrating the urgent need for novel in vitro tools that can imitate aspects of the in vivo situation more accurate. Dynamic cell culture, where cells are cultured and incubated in the presence of shear stress has the potential to bridge this gap by mimicking key-features of organs and vessels. Our approach implements and compares a chip-based dynamic cell culture model to the common static cell culture and mouse model to assess its capability to predict the in vivo success more accurately, by using a well-defined poly((methyl methacrylate)-co-(methacrylic acid)) and poly((methyl methacrylate)-co-(2-dimethylamino ethylmethacrylate)) based nanoparticle library. After characterization in static and dynamic in vitro cell culture we were able to show that physiological conditions such as cell-cell communication of co-cultured endothelial cells and macrophages as well as mechanotransductive signaling through shear stress significantly alter cellular nanoparticle uptake. In addition, it could be demonstrated by using dynamic cell cultures that the in vivo situation is simulated more accurately and thereby can be applied as a novel system to investigate the performance of nanoparticle systems in vivo more reliable.

The influence of polymer architecture on in vitro pDNA transfection

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 the last years numerous new polymer designs showed enhanced transfections properties in combination with a good biocompatibility.

Asymmetric flow field-flow fractionation in the field of nanomedicine

Asymmetric flow field-flow fractionation (AF4) is a widely used and versatile technique in the family of field-flow fractionations, indicated by a rapidly increasing number of publications. It represents a gentle separation and characterization method, where nonspecific interactions are reduced to a minimum, allows a broad separation range from several nano- up to micrometers and enables a superior characterization of homo- and heterogenic systems. In particular, coupling to multiangle light scattering provides detailed access to sample properties. Information about molar mass, polydispersity, size, shape/conformation, or density can be obtained nearly independent of the used material. In this Perspective, the application and progress of AF4 for (bio)macromolecules and colloids, relevant for "nano" medical and pharmaceutical issues, will be presented. The characterization of different nanosized drug or gene delivery systems, e.g., polymers, nanoparticles, micelles, dendrimers, liposomes, polyplexes, and virus-like-particles (VLP), as well as therapeutic relevant proteins, antibodies, and nanoparticles for diagnostic usage will be discussed. Thereby, the variety of obtained information, the advantages and pitfalls of this emerging technique will be highlighted. Additionally, the influence of different fractionation parameters in the separation process is discussed in detail. Moreover, a comprehensive overview is given, concerning the investigated samples, fractionation parameters as membrane types and buffers used as well as the chosen detectors and the corresponding references. The perspective ends up with an outlook to the future.

Three cases of renal relapse after allogeneic hematopoietic stem cell transplantation for childhood acute lymphoblastic leukemia

Isolated renal relapse after allogeneic hematopoietic stem cell transplantation (alloHSCT) in children with acute lymphoblastic leukemia (ALL) is a rare condition. Generally, in ALL, the sites most frequently affected by extramedullary relapse are the central nervous system (CNS) and the testicles. Here we report on three young boys with relapsed B-precursor ALL, who underwent alloHSCT from HLA-identical siblings and suffered a histopathologically proven isolated unilateral renal relapse (two patients) or a combined renal and testicular relapse (one patient) 6, 10 and 12 months post alloHSCT. In all patients at the time of relapse bone marrow showed complete remission with complete donor hematopoiesis. They all received total body irradiation with partial shielding of the kidneys as part of their conditioning therapy, such that renal shielding could be an explanation for the observed accumulation of renal relapses. Moreover, during the past few years so called immune privilege has been postulated for frequent relapse sites such as the CNS, the testicles and the anterior chamber of the eye. Impaired accessability of these organs by cytotoxic T-cells (CTLs) with a reduced graft-versus-leukemia (GvL) effect after alloHSCT is based on a number of different molecular and cellular mechanisms. Similar mechanisms have been shown to be effective in the tubulointerstitial space of the kidney, rendering the kidney a potentially immune privileged site. Due to these observations we advocate sufficient treatment of the kidneys during conditioning therapy.

[The relative bioavailability of co-trimoxazole suspensions]

The relative bioavailability of a co-trimoxazole suspension manufactured by VEB Berlin-Chemie (B); Belocid-Suspension was compared with a widespread used suspension (V) in healthy male students (22-29 ys. aged). A single oral dose of 160 mg trimethoprim (TPM) and 800 mg sulphamethoxazole (SMZ) produced similar blood levels with either preparation. The TMP peak levels were 1.44 +/- 0.18 (B) and 1.40 +/- 0.26 mg/l (V), respectively after 1.5 and 1.0 h on an average. The AUC amounted to 18.94 +/- 2.25 (B) and 17.19 +/- 3.62 mg . h/l (V), respectively. About one half (52.5%) of the given TMP dose was excreted unchanged by kidney within 48 h after administration of the respective suspension. The SMZ peak levels run to 37.2 +/- 10.3 (B) and 38.6 +/- 5.4 mg/l (V) after 3.6 +/- 3.5 and 1.3 +/- 0.8 h. The AUC were identical: 682.3 +/- 126.2 (B) vs. 686.9 +/- 165.8 mg . h/l (V). After both preparations 67% of the given SMZ dose could be detected in urine within 48 h. In two out of the eight volunteers the absorption of B was delayed, but it passed off to the same extent. In all other cases absorption of the suspension was accelerated in comparison with tablet administration studies reported. Peak blood levels of TMP and SMZ after ingestion of the suspensions reach the lower range of values resulting from tablet intake. Both suspensions are regarded interchangeable with respect to bioavailability, which is also comparable to co-trimoxazole tablets.

[The effect of intrahepatic cholestasis in pregnancy on various forms of cytochrome P-450-dependent biotransformation reactions]

The elimination of caffeine from plasma and the excretion of the main metabolites of metamizol (noramidopyrinemethanesulphonate sodium) into the urine were determined in healthy pregnant women (weeks 30-38 of pregnancy) and in patients with intrahepatic cholestasis in pregnancy (weeks 28-39 of pregnancy). From the elimination velocity of these model substances conclusions concerning the activity of 3-methylcholanthrene (caffeine elimination) and phenobarbital inducible isoenzymes (metamizol elimination) of cytochrome P-450 are drawn. Patients with intrahepatic cholestasis in pregnancy (t1/2 = 15.8 +/- 1.8 h) eliminate caffeine more slowly than healthy pregnant women (t1/2 = 11.0 +/- 0.8 h) at this stage of pregnancy. The excretion of the metabolites of metamizol is only in tendency diminished in patients with intrahepatic cholestasis. The influence of the intrahepatic cholestasis on the cytochrome P-450 isoenzymes investigated differs in degree.

[Elimination of caffeine and metamizol in in vivo characterization of cytochrome P-450 dependent biotransformation reactions in aged humans]

Elimination of caffeine from plasma and excretion of main metabolites of metamizol (noramidopyrine methanesulphonate sodium) in urine were determined in young healthy (age 18-27 years) and in old aged volunteers (older than 65 years). From the elimination velocity of these model substances conclusions concerning the activity of 3-methylcholanthrene inducible (caffeine elimination) and of phenobarbital inducible (metamizol elimination) isoenzymes of cytochrome P-450 are drawn. Whereas in old age caffeine metabolism is unchanged, there is a strong delay in renal excretion of main metabolites of metamizol in old volunteers. It is concluded that different hepatic cytochrome P-450 isoenzymes are differentially influenced with increasing age in men.

[The influence of chronic renal insufficiency on the demethylating activities of various cytochrome P-450 subspecies in humans]

Caffeine is mainly metabolized by 3-methylcholanthrene-inducible cytochrome P-450 (P-450MC) and metamizol (noramidopyrine methanesulfonate sodium) is mainly metabolized by phenobarbital-inducible cytochrome P-450 (P-450PB). That's why the half life of caffeine and the elimination of the main metabolites of metamizol were used as parameters in vivo characterizing both groups of the cytochrome P-450-complex. The influence of chronic renal insufficiency was investigated (8 patients in the stage of compensated retention, creatinine in serum 380-1280 mumol X l-1, and 6 hemodialyzed patients, here only metamizol elimination was established). Both the caffeine and the metamizol eliminations of patients with chronic renal insufficiency are not different from those of healthy volunteers. We concluded that the demethylation activity of the cytochrome P-450-complex is not distinctly influenced by chronic renal insufficiency.