pDMAEMA is internalised by endocytosis but does not physically disrupt endosomes

Poly(2-(dimethylamino)ethyl methacrylate)-Grafted Amphiphilic Block Copolymer Micelles Co-Loaded with Quercetin and DNA

The synergistic effect of drug and gene delivery is expected to significantly improve cancer therapy. However, it is still challenging to design suitable nanocarriers that are able to load simultaneously anticancer drugs and nucleic acids due to their different physico-chemical properties. In the present work, an amphiphilic block copolymer comprising a biocompatible poly(ethylene glycol) (PEG) block and a multi-alkyne-functional biodegradable polycarbonate (PC) block was modified with a number of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) side chains applying the highly efficient azide-alkyne "click" chemistry reaction. The resulting cationic amphiphilic copolymer with block and graft architecture (MPEG-b-(PC-g-PDMAEMA)) self-associated in aqueous media into nanosized micelles which were loaded with the antioxidant, anti-inflammatory, and anticancer drug quercetin. The drug-loaded nanoparticles were further used to form micelleplexes in aqueous media through electrostatic interactions with DNA. The obtained nanoaggregates-empty and drug-loaded micelles as well as the micelleplexes intended for simultaneous DNA and drug codelivery-were physico-chemically characterized. Additionally, initial in vitro evaluations were performed, indicating the potential application of the novel polymer nanocarriers as drug delivery systems.

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.

Context-Responsive Nanoparticle Derived from Synthetic Zwitterionic Ionizable Phospholipids in Targeted CRISPR/Cas9 Therapy for Basal-like Breast Cancer

The majority of triple negative breast cancers (TNBCs) are basal-like breast cancers (BLBCs), which tend to be more aggressive, proliferate rapidly, and have poor clinical outcomes. A key prognostic biomarker and regulator of BLBC is the Forkhead box C1 (FOXC1) transcription factor. However, because of its functional placement inside the cell nucleus and its structural similarity with other related proteins, targeting FOXC1 for therapeutic benefit, particularly for BLBC, continues to be difficult. We envision targeted nonviral delivery of CRISPR/Cas9 plasmid toward the efficacious knockdown of FOXC1. Keeping in mind the challenges associated with the use of CRISPR/Cas9 in vivo, including off-targeting modifications, and effective release of the cargo, a nanoparticle with context responsive properties can be designed for efficient targeted delivery of CRISPR/Cas9 plasmid. Consequently, we have designed, synthesized, and characterized a zwitterionic amino phospholipid-derived transfecting nanoparticle for delivery of CRISPR/Cas9. The construct becomes positively charged only at low pH, which encourages membrane instability and makes it easier for nanoparticles to exit endosomes. This has enabled effective in vitro and in vivo downregulation of protein expression and genome editing. Following this, we have used EpCAM aptamer to make the system targeted toward BLBC cell lines and to reduce its off-target toxicity. The in vivo efficacy, biodistribution, preliminary pharmacokinetics, and biosafety of the optimized targeted CRISPR nanoplatform is then validated in a rodent xenograft model. Overall, we have attempted to knockout the proto-oncogenic FOXC1 expression in BLBC cases by efficient delivery of CRISPR effectors via a context-responsive nanoparticle delivery system derived from a designer lipid derivative. We believe that the nonviral approach for in vitro and in vivo delivery of CRISPR/Cas9 targeted toward FOXC1, studied herein, will greatly emphasize the therapeutic regimen for BLBC.

Poly(N,N-dimethylaminoethyl methacrylate) as a bioactive polyelectrolyte-production and properties

Poly(N,N-dimethylaminoethyl methacrylate) is a polyelectrolyte with many important chemical and physical properties and, above all, offers a wide range of interesting biological properties. Currently, research on this polymer is ongoing in several centres around the world. The process of polymerizing the monomer is not easy, as there are difficulties in obtaining a product with repeatable properties. This work collected and described most of the currently known and used polymerization methods of N,N-dimethylaminoethyl methacrylate, taking into account the type of method, the solvent used, the initiator, as well as the process temperature and the average molecular weight of the polymer obtained. The most important properties of the discussed polymer, such as solubility, bioactivity, hydrophilicity, cytotoxicity, conductivity, and thermal and hydrodynamic parameters, are discussed on the basis of the available scientific literature. This work aims, among other things, to increase the possibility of using poly(N,N-dimethylaminoethyl methacrylate) as a material in advanced practical applications. Therefore, various methods of applied use of the polymer in question have also been described so far. Copolymers of the N,N-dimethylaminoethyl methacrylate are now too large a collection to fit in a single publication. Therefore, only the most interesting examples were cited in this work.

Cationic Polymers as Transfection Reagents for Nucleic Acid Delivery

Nucleic acid therapy can achieve lasting and even curative effects through gene augmentation, gene suppression, and genome editing. However, it is difficult for naked nucleic acid molecules to enter cells. As a result, the key to nucleic acid therapy is the introduction of nucleic acid molecules into cells. Cationic polymers are non-viral nucleic acid delivery systems with positively charged groups on their molecules that concentrate nucleic acid molecules to form nanoparticles, which help nucleic acids cross barriers to express proteins in cells or inhibit target gene expression. Cationic polymers are easy to synthesize, modify, and structurally control, making them a promising class of nucleic acid delivery systems. In this manuscript, we describe several representative cationic polymers, especially biodegradable cationic polymers, and provide an outlook on cationic polymers as nucleic acid delivery vehicles.

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.

Self-immolative Polyplexes for DNA Delivery

Nucleic acids have immense potential for the treatment and prevention of a wide range of diseases, but delivery vehicles are needed to assist with their entry into cells. Polycations can...

Antibacterial properties of poly (N,N-dimethylaminoethyl methacrylate) obtained at different initiator concentrations in solution polymerization

The samples of poly(N,N-dimethylaminoethyl methacrylate) were synthesized by radical polymerization. The amount of monomer and solvent was constant as opposed to an amount of initiator which was changing. No clear relationship between polymerization conditions and the molecular weight of the polymer was found, probably due to the branched configuration of produced polymer. Bactericidal interactions in all samples against Gram-positive and Gram-negative bacteria have been demonstrated. However, the observed effect has various intensities, depending on the type of bacteria and the type of sample.

Polycation-Mediated Transfection: Mechanisms of Internalization and Intracellular Trafficking

Polyplex-mediated gene transfection is now in its' fourth decade of serious research, but the promise of polyplex-mediated gene therapy has yet to fully materialize. Only approximately one in a million applied plasmids actually expresses. A large part of this is due to an incomplete understanding of the mechanism of polyplex transfection. There is an assumption that internalization must follow a canonical mechanism of receptor mediated endocytosis. Herein, we present arguments that untargeted (and most targeted) polyplexes do not utilize these routes. By incorporating knowledge of syndecan-polyplex interactions, we can show that syndecans are the "target" for polyplexes. Further, it is known that free polycations (which disrupt cell-membranes by acid-catalyzed hydrolysis of phospholipid esters) are necessary for (untargeted) endocytosis. This can be incorporated into the model to produce a novel mechanism of endocytosis, which fits the observed phenomenology. After membrane translocation, polyplex containing vesicles reach the endosome after diffusing through the actin mesh below the cell membrane. From there, they are acidified and trafficked toward the lysosome. Some polyplexes are capable of escaping the endosome and unpacking, while others are not. Herein, it is argued that for some polycations, as acidification proceeds the polyplexes excluding free polycations, which disrupt the endosomal membrane by acid-catalyzed hydrolysis, allowing the polyplex to escape. The polyplex's internal charge ratio is now insufficient for stability and it releases plasmids which diffuse to the nucleus. A small proportion of these plasmids diffuse through the nuclear pore complex (NPC), with aggregation being the major cause of loss. Those plasmids that have diffused through the NPC will also aggregate, and this appears to be the reason such a small proportion of nuclear plasmids express mRNA. Thus, the structural features which promote unpacking in the endosome and allow for endosomal escape can be determined, and better polycations can be designed.

Anionic Complex with Efficient Expression and Good Safety Profile for mRNA Delivery

We previously found that a complex comprising plasmid DNA (pDNA), polyethylenimine (PEI), and γ-polyglutamic acid (γ-PGA) had high transgene efficiency without cytotoxicity in vitro and in vivo. However, messenger RNA (mRNA) remains an attractive alternative to pDNA. In this study, we developed a safe and effective delivery system for mRNA to prevent its degradation and efficiently deliver it into target cells. Various cationic and anionic complexes were produced containing PEI, γ-PGA, and an mRNA encoding firefly luciferase. Their physicochemical properties and cytotoxicities were analyzed and the in vitro and in vivo protein expression were determined. The cationic mRNA/PEI complex showed high in vitro protein expression with strong cytotoxicity. The anionic complex was constructed as mRNA/PEI8/γ-PGA12 complex with a theoretical charge ratio of 1:8:12 based on the phosphate groups of the mRNA, nitrogen groups of PEI, and carboxylate groups of γ-PGA. It was stable and showed high in vitro protein expression without cytotoxicity. After intravenous administration of mRNA/PEI8/γ-PGA12 complex to mice, high protein expression was observed in the spleen and liver and slight expression was observed in the lung over 24 h. Thus, the newly constructed mRNA/PEI8/γ-PGA12 complex provides a safe and effective strategy for the delivery of mRNA.

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.

Boronic acid copolymers for direct loading and acid-triggered release of Bis-T-23 in cultured podocytes

We report an acid-reversible linker for triggered release of Bis-T-23, an experimental small molecule drug for kidney disease treatment that restores podocyte morphology during disease. Bis-T-23 contains catechols, which form an acid-reversible, covalent boronate ester bond with boronic acids. We synthesized phenylboronic acid-containing polymers using reversible addition-fragmentation chain transfer polymerization that were able to directly load and solubilize Bis-T-23. Because of the reversibility of the boronic ester bond, drug was released in its native form in a pH-dependent manner. The polymers rapidly trafficked into acidic compartments and did not exhibit cytotoxicity, and polymer-drug conjugates successfully delivered Bis-T-23 into cultured podocytes.

Insights on the intracellular trafficking of PDMAEMA gene therapy vectors

It is known that an efficient gene therapy vector must overcome several steps to be able to express the gene of interest: (I) enter the cell by crossing the cell membrane; (II) escape the endo-lysosomal degradation pathway; (III) release the genetic material; (IV) traffic through the cytoplasm and enter the nucleus; and last (V), enable gene expression to synthetize the protein of interest. In recent years, we and others have demonstrated the potential of poly(2‑(N,N'‑dimethylamino)ethylmethacrylate) (PDMAEMA) as a gene therapy vehicle. Further optimization of gene transfer efficiency requires the understanding of the intracellular pathway of PDMAEMA. Therefore the goal of this study was to determine the cellular entry and intracellular trafficking mechanisms of our PDMAEMA vectors and determine the gene transfer bottleneck. For this, we have produced rhodamine-labeled PDMAEMA polyplexes that were used to transfect retinal cells and the cellular localization determined by co-localization with cellular markers. Our vectors quickly and efficiently cross the cell membrane, and escape the endo-lysosomal system by 24 h. We have observed the PDMAEMA vectors to concentrate around the nucleus, and the DNA load to be released in the first 24 h after transfection. These results allow us to conclude that although the endo-lysosomal system is an important obstacle, PDMAEMA gene vectors can overcome it. The nuclear membrane, however, constitutes the bottleneck to PDMAEMA gene transfer ability.

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 great escape: how cationic polyplexes overcome the endosomal barrier

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

Diblock Copolymer Hydrophobicity Facilitates Efficient Gene Silencing and Cytocompatible Nanoparticle-Mediated siRNA Delivery to Musculoskeletal Cell Types

pH-responsive diblock copolymers provide tailorable nanoparticle (NP) architecture and chemistry critical for siRNA delivery. Here, diblock polymers varying in first (corona) and second (core) block molecular weight (M_n), corona/core ratio, and core hydrophobicity (%BMA) were synthesized to determine their effect on siRNA delivery in murine tenocytes (mTenocyte) and murine and human mesenchymal stem cells (mMSC and hMSCs, respectively). NP-mediated siRNA uptake, gene silencing, and cytocompatibility were quantified. Uptake is positively correlated with first block M_n in mTenocytes and hMSCs (p ≤ 0.0005). All NP resulted in significant gene silencing that was positively correlated with %BMA (p < 0.05) in all cell types. Cytocompatibility was reduced in mTenocytes compared to MSCs (p < 0.0001). %BMA was positively correlated with cytocompatibility in MSCs (p < 0.05), suggesting stable NP are more cytocompatible. Overall, this study shows that NP-siRNA cytocompatibility is cell type dependent, and hydrophobicity (%BMA) is the critical diblock copolymer property for efficient gene silencing in musculoskeletal cell types.

Gene Transfection Mediated by Catiomers Requires Free Highly Charged Polymer Chains To Overcome Intracellular Barriers

The prospective use of the block copolymers poly(ethylene oxide)₁₁₃-b-poly[2-(diethylamino)ethyl methacrylate]₅₀ (PEO₁₁₃-b-PDEA₅₀) and poly[oligo(ethylene glycol)methyl ether methacrylate]₇₀-b-poly[oligo(ethylene glycol)methyl ether methacrylate₁₀-co-2-(diethylamino)ethyl methacrylate₄₇-co-2-(diisopropylamino)ethyl methacrylate₄₇] (POEGMA₇₀-b-P(OEGMA₁₀-co-DEA₄₇-co-DPA₄₇)) as nonviral gene vectors was evaluated. The polymers are able to properly condense DNA into nanosized particles (R_H ≈ 75 nm), which are marginally cytotoxic and can be uptaken by cells. However, the green fluorescent protein (GFP) expression assays evidenced that DNA delivery is essentially negligible meaning that intracellular trafficking hampers efficient gene release. Subsequently, we demonstrate that cellular uptake and particularly the quantity of GFP-positive cells are substantially enhanced when the block copolymer polyplexes are produced and further supplemented by BPEI chains (branched polyethylenimine). The dynamic light scattering/electrophoretic light scattering/isothermal titration calorimetry data suggest that such a strategy allows the adsorption of BPEI onto the surface of the polyplexes, and this phenomenon is responsible for increasing the size and surface charge of the assemblies. Nevertheless, most of the BPEI chains remain freely diffusing in the systems. The biological assays confirmed that cellular uptake is enhanced in the presence of BPEI and principally, the free highly charged polymer chains play the central role in intracellular trafficking and gene transfection. These investigations pointed out that the transfection efficiency versus cytotoxicity issue can be balanced by a mixture of BPEI and less cytotoxic agents such as for instance the proposed block copolymers.

Endocytosis and intracellular traffic of cholesterol-PDMAEMA liposome complexes in human epithelial-like cells

Liposomes are generally used as delivery systems, as they are capable of encapsulating a wide variety of molecules (i.e. plasmids, recombinant proteins, therapeutic drugs). However, liposomal drug delivery have to fulfill different requirements, such as the effective internalization by the target cells and avoidance of the degradative activity of the intracellular compartments. The use of polymer lipid complexes (PLCs), by including different polymers in the liposome formulation, could improve internalization and intracellular release of drugs. The aim of the present work is to study the mechanisms of cellular uptaking and the intracellular trafficking of PLCs formed with cholesterol-poly(2-(dimethylamino)ethyl methacrylate) CHO-PDMAEMA and lecithin (LC CHO-PD). Calcein-loaded liposomes were used to determine cellular uptake and intracellular localization by flow cytometry and confocal microscopy. Incorporation of CHO-PDMAEMA to lecithin liposomes enhanced the internalization capacity of PLCs. Internalization of PLCs by human epithelial-like cells (HEK-293) diminished at 4°C, suggesting uptake by endocytosis. PLCs showed no co-localization with acidic compartments after internalization. Experiments with endocytosis inhibitors and co-localization of liposomes and albumin, suggested the caveolae endocytic pathway as the most probable route for intracellular trafficking of PLCs. In this work, we demonstrated an efficient uptake of LC CHO-PDs by human epithelial-like cells (HEK-293) through the non-degradative caveolae endocytic pathway. The mode of internalization and the intracellular fate of liposomes under study, suggest a promising use of LC CHO-PDs as drug delivery systems.

Influence of Cubosome Surface Architecture on Its Cellular Uptake Mechanism

Interaction of nanoparticles with biological systems is a key factor influencing their efficacy as a drug delivery vehicle. The inconsistency in defining the optimal design parameters across different nanoparticle types suggests that information gained from one model system need not apply to other systems. Therefore, selection of a versatile model system is critical for such studies. Cubosomes are one of the potential drug delivery vehicles due to their biocompatibility, stability, ability to carry hydrophobic, hydrophilic, and amphiphilic drugs, and ease of surface modification. Here we report the importance of surface architecture of cubosomes by comparing their cellular uptake mechanism with poly-ε-lysine (PεL)-coated cubosomes. Uncoated cubosomes entered cells by an energy-independent, cholesterol-dependent mechanism, whereas PεL-coated cubosomes relied on energy-dependent mechanisms to enter the endosomes. As endosomal entrapment was evaded by uncoated cubosomes, they can be preferably used for cytosolic delivery of therapeutic agents.

Efficient Condensation of DNA into Environmentally Responsive Polyplexes Produced from Block Catiomers Carrying Amine or Diamine Groups

The intracellular delivery of nucleic acids requires a vector system as they cannot diffuse across lipid membranes. Although polymeric transfecting agents have been extensively investigated, none of the proposed gene delivery vehicles fulfill all of the requirements needed for an effective therapy, namely, the ability to bind and compact DNA into polyplexes, stability in the serum environment, endosome-disrupting capacity, efficient intracellular DNA release, and low toxicity. The challenges are mainly attributed to conflicting properties such as stability vs efficient DNA release and toxicity vs efficient endosome-disrupting capacity. Accordingly, investigations aimed at safe and efficient therapies are still essential to achieving gene therapy clinical success. Taking into account the mentioned issues, herein we have evaluated the DNA condensation ability of poly(ethylene oxide)113-b-poly[2-(diisopropylamino)ethyl methacrylate]50 (PEO113-b-PDPA50), poly(ethylene oxide)113-b-poly[2-(diethylamino)ethyl methacrylate]50 (PEO113-b-PDEA50), poly[oligo(ethylene glycol)methyl ether methacrylate]70-b-poly[oligo(ethylene glycol)methyl ether methacrylate10-co-2-(diethylamino)ethyl methacrylate47-co-2-(diisopropylamino)ethyl methacrylate47] (POEGMA70-b-P(OEGMA10-co-DEA47-co-DPA47), and poly[oligo(ethylene glycol)methyl ether methacrylate]70-b-poly{oligo(ethylene glycol)methyl ether methacrylate10-co-2-methylacrylic acid 2-[(2-(dimethylamino)ethyl)methylamino]ethyl ester44} (POEGMA70-b-P(OEGMA10-co-DAMA44). Block copolymers PEO113-b-PDEA50 and POEGMA70-b-P(OEGMA10-co-DEA47-co-DPA47) were evidenced to properly condense DNA into particles with a desirable size for cellular uptake via endocytic pathways (R(H) ≈ 65-85 nm). The structure of the polyplexes was characterized in detail by scattering techniques and atomic force microscopy. The isothermal titration calorimetric data revealed that the polymer/DNA binding is endothermic; therefore, the process in entropically driven. The combination of results supports that POEGMA70-b-P(OEGMA10-co-DEA47-co-DPA47) condenses DNA more efficiently and with higher thermodynamic outputs than does PEO113-b-PDEA50. Finally, circular dichroism spectroscopy indicated that the conformation of DNA remained the same after complexation and that the polyplexes are very stable in the serum environment.

Cationic nanogels as Trojan carriers for disruption of endosomes

The comparison study of interaction of linear poly(2-dimethyl amino)ethyl methacrylate and its cationic nanogels of various cross-linking with both DNA and sodium poly(styrene sulfonate) has been performed. Although all amino groups of the nanogels proved to be susceptible for protonation, their accessibility for ion pairing with the polyanions was controlled and impaired with the cross-linking. The investigation of nanogels complexes with cells in culture that was accomplished by using of calcein pH-sensitive probe revealed a successive increase in the cytoplasmic fluorescence upon the growth in the cross-linking due to calceine leakage from acidic compartments to cytosol. This regularity implies that amino groups which are buried presumably inside the nanogel are protected against the ion-pairing with polyanions of plasma membrane and hence are able to manifest buffer properties while captured into acidic endosomes, i.e. possess lyso/endosomolytic capacity. These findings suggest that network architecture makes an important contribution to proton sponge properties of weak polycations.

Combination of microRNA therapeutics with small-molecule anticancer drugs: mechanism of action and co-delivery nanocarriers

MicroRNAs (miRNAs) regulate multiple molecular pathways vital for the hallmarks of cancer with a high degree of biochemical specificity and potency. By restoring tumor suppressive miRNAs or ablating oncomiRs, miRNA-based therapies can sensitize cancer cells to conventional cytotoxins and the molecularly targeted drugs by promoting apoptosis and autophagy, reverting epithelial-to-mesenchymal transition, suppressing tumor angiogenesis, and downregulating efflux transporters. The development of miRNA-based therapeutics in combination with small-molecule anticancer drugs provides an unprecedented opportunity to counteract chemoresistance and improve treatment outcome in a broad range of human cancers. This review summarizes the mechanisms and advantages for the combination therapies involving miRNAs and small-molecule drugs, as well as the recent advances in the co-delivery nanocarriers for these agents.

Encapsidated atom-transfer radical polymerization in Qβ virus-like nanoparticles

Virus-like particles (VLPs) are unique macromolecular structures that hold great promise in biomedical and biomaterial applications. The interior of the 30 nm-diameter Qβ VLP was functionalized by a three-step process: (1) hydrolytic removal of endogenously packaged RNA, (2) covalent attachment of initiator molecules to unnatural amino acid residues located on the interior capsid surface, and (3) atom-transfer radical polymerization of tertiary amine-bearing methacrylate monomers. The resulting polymer-containing particles were moderately expanded in size; however, biotin-derivatized polymer strands were only very weakly accessible to avidin, suggesting that most of the polymer was confined within the protein shell. The polymer-containing particles were also found to exhibit physical and chemical properties characteristic of positively charged nanostructures, including the ability to easily enter mammalian cells and deliver functional small interfering RNA.

Influence of histidine incorporation on buffer capacity and gene transfection efficiency of HPMA-co-oligolysine brush polymers

One of the major intracellular barriers to nonviral gene delivery is efficient endosomal escape. The incorporation of histidine residues into polymeric constructs has been found to increase endosomal escape via the proton sponge effect. Statistical and diblock copolymers of N-(2-hydroxypropyl)methacrylamide (HPMA), oligolysine, and oligohistidine were synthesized via reversible-addition fragmentation chain transfer (RAFT) polymerization and tested for in vitro transfection efficiency, buffering ability, and polyplex uptake mechanism via the use of chemical endocytic inhibitors. Interestingly, histidine-containing statistical and diblock polymers exhibited increased buffer capacity in different endosomal pH ranges. Statistical copolymers transfected better than block copolymers that contained similar amounts of histidine. In addition, only the polymer containing the highest incorporation of oligohistidine residues led to increases in transfection efficiency over the HPMA-oligolysine base polymer. Thus, for these polymer architectures, high histidine incorporation may be required for efficient endosomal escape. Furthermore, inhibitor studies indicate that nonacidified caveolae-mediated endocytosis may be the primary route of transfection for these copolymers, suggesting that alternative approaches for increasing endosomal escape may be beneficial for enhancing transfection efficiency with these HPMA-oligolysine copolymers.

Insight into the role of N,N-dimethylaminoethyl methacrylate (DMAEMA) conjugation onto poly(ethylenimine): cell viability and gene transfection studies

In the present study, the effect of N,N-dimethylaminoethyl methacrylate (DMAEMA) conjugation onto branched poly(ethylenimine) (PEI) with different grafting degree was examined for gene delivery applications. The DMAEMA-grafted-PEI conjugates were characterized and complexed with plasmid DNA (pDNA) at various concentrations, and the physicochemical properties, cell viability, and in vitro transfection efficiency of the complexes were evaluated in HEK 293T cells. Computational techniques were used to analyze the interaction energies and possible binding modes between DNA and conjugates at different grafting degrees. The cytotoxicity analysis and in vitro transfection efficiency of the conjugate/pDNA complexes exhibited a beneficial effect of DMAEMA conjugation when compared to PEI alone. The computational results revealed that the DNA/vector interaction energy decreases with increasing grafting degree, which can be associated to an enhanced release of the pDNA from the carrier once inside cells. The results indicate the significance of DMAEMA conjugation onto PEI as a promising approach for gene delivery applications.

Ternary complexes of poly(vinyl pyrrolidone)-graft-poly(2-dimethylaminoethyl methacrylate), DNA and bovine serum albumin for gene delivery

Novel well-defined hydrophilic cationic polymers with different length of polycation chain for gene delivery, poly(vinyl pyrrolidone)-graft-poly(2-dimethylaminoethyl methacrylate)s (PPDs), were synthesized by atom transfer radical polymerization (ATRP). The chemical structures and compositions of these polymers were characterized by FT-IR, (1)H-NMR and GPC. The experimental results of dynamic light scattering (DLS), ζ-potential and transmission electron microscopy (TEM) indicated that PPD could condense plasmid DNA (pDNA) to form nanocomplexes. Agarose gel retardation assays demonstrated that PPD could encapsulate plasmid DNA completely when the N/P ratio is equal to or above 3. MTT assay and in vitro gene transfection results indicated that PPD/pDNA complexes exhibited high transfection efficiency concomitant with obvious cytotoxicity. Furthermore, bovine serum albumin (BSA) was utilized to assembly with the binary complexes of PPD/pDNA to screen the residual surface positive charges of complexes in order to decrease cytotoxicity of the binary complexes. Physicochemical properties were characterized and the results indicated that the coating of BSA was able to decrease the zeta potential of the nano-sized PPD/pDNA complexes nearly to electroneutrality without interfering with DNA condensation ability. The ternary complexes of BSA/PPD/pDNA demonstrated no cytotoxicity and also maintained high gene transfection efficiency in HepG2 cells in 10% serum compared with that in serum-free condition.

Design and biophysical characterization of bioresponsive degradable poly(dimethylaminoethyl methacrylate) based polymers for in vitro DNA transfection

Water-soluble, degradable polymers based on poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) with low cytotoxicity and good p-DNA transfection efficiency are highlighted in this article. To solve the nondegradability issue of PDMAEMA, new polymers based on DMAEMA and 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) for gene transfection were synthesized. A poly(ethylene oxide) (PEO) azo-initiator was used as free-radical initiator. PEGylation was performed to improve water solubility and to reduce cytotoxicity of the polymers. The resulting polymers contain hydrolyzable ester linkages in the backbone and were soluble in water even with very high amounts of ester linkages. These degradable copolymers showed significantly less toxicity with a MTT assay using L929 cell lines and demonstrated promising DNA transfection efficiency when compared with the gold standard poly(ethyleneimine). Bioresponsive properties of the corresponding quaternized DMAEMA based degradable polymers were also studied. Although the quaternized DMAEMA copolymers showed enhanced water solubility, they were inferior in gene transfection and toxicity as compared to the unquaternized copolymers.

Diblock copolymers with tunable pH transitions for gene delivery

A series of diblock copolymers containing an endosomal-releasing segment composed of diethylaminoethyl methacrylate (DEAEMA) and butyl methacrylate (BMA) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The materials were designed to condense plasmid DNA (pDNA) through electrostatic interactions with a cationic poly(N,N-dimethylaminoethyl methacrylate) (DMAEMA) first block. The pDMAEMA was employed as a macro chain transfer agent (macroCTA) for the synthesis of a series in which the relative feed ratios of DEAEMA and BMA were systematically varied from 20% to 70% BMA. The resultant diblock copolymers exhibited low polydispersity (PDI ≤ 1.06) with similar molecular weights (M(n) = 19.3-23.1 kDa). Dynamic light scattering (DLS) measurements in combination with (1)H NMR D(2)O studies demonstrated that the free copolymers assemble into core-shell micelles at physiological pH. Reduction of the solution pH to values representative of endosomal/lysosomal compartments induced an increase in the net cationic charge of the core through protonation of the DEAEMA residues. This protonation promotes micelle destabilization and exposure of the hydrophobic BMA residues that destabilize biological membranes. The pH value at which this micelle-to-unimer transition occurred was dependent on the hydrophobic content of the copolymer, with higher BMA-containing copolymer compositions exhibiting pH-induced transitions to the membrane-destabilizing state at successively lower pH values. The ability of the diblock copolymers to deliver pDNA was subsequently investigated using a GFP expression vector in two monocyte cell lines. High levels of DNA transfection were observed for the copolymer compositions exhibiting the sharpest pH transitions and membrane destabilizing activities, demonstrating the importance of tuning the endosomal-releasing segment composition.

Resistance of Staphylococcus aureus to the cationic antimicrobial agent poly(2-(dimethylamino ethyl)methacrylate) (pDMAEMA) is influenced by cell-surface charge and hydrophobicity

Cationic antimicrobial agents may prevent device-associated infections caused by Staphylococcus epidermidis and Staphylococcus aureus. This study reports that the cationic antimicrobial polymer poly(2-(dimethylamino ethyl)methacrylate) (pDMAEMA) was more effective at antagonizing growth of clinical isolates of S. epidermidis than of S. aureus. Importantly, mature S. epidermidis biofilms were significantly inactivated by pDMAEMA. The S. aureus isolates tested were generally more hydrophobic than the S. epidermidis isolates and had a less negative charge, although a number of individual S. aureus and S. epidermidis clinical isolates had similar surface hydrophobicity and charge values. Fluorescence spectroscopy and flow cytometry revealed that fluorescently labelled pDMAEMA interacted strongly with S. epidermidis compared with S. aureus. S. aureus ΔdltA and ΔmprF mutants were less hydrophobic and therefore more susceptible to pDMAEMA than wild-type S. aureus. Although the different susceptibility of S. epidermidis and S. aureus isolates to pDMAEMA is complex, influenced in part by surface hydrophobicity and charge, these findings nevertheless reveal the potential of pDMAEMA to treat S. epidermidis infections.

Dual-stimuli responsive behaviors of diblock polyampholyte PDMAEMA-b-PAA in aqueous solution

Two poly(2-(dimethylamino)ethyl methacrylate)-b-poly(acrylic acid) diblock copolymers, PDMAEMA(84)-b-PAA(18) and PDMAEMA(50)-b-PAA(18), were synthesized by the atom transfer radical polymerization (ATRP) and their dual-stimuli responsive behaviors to the changes in temperature and pH in aqueous solutions were investigated by UV-vis spectroscopy, dynamic light scattering (DLS), (1)H NMR spectroscopy and surface tension measurement. Different from PDMAEMA(84)-b-PAA(18) solutions where no aggregation is observed between pH 7.0 and 9.5, the PDMAEMA(50)-b-PAA(18) aggregates can exist in this broad pH range due to the hydrophobic interactions among the charge-balanced polyampholyte chains. At high pH, e.g., 11.0, the DMAEMA segments collapse to form the core of micelles due to the hydrophobic property of the de-protonized DMAEMA stabilized with the highly ionized AA segments on the surface of the micelles upon heating. At pH around the IEP, e.g., 9.5, large micelles can be formed in PDMAEMA(84)-b-PAA(18) solution upon heating, just like that at pH 11.0, while PDMAEMA(50)-b-PAA(18) first formed the micelles due to the electrostatic attraction between ionized AA segments and protonated DMAEMA segments, but the aggregation of the micelles was hardly happened upon heating due to the smaller DMAEMA segment. Moreover, LCST can be exactly estimated by surface tension experiment.

Antibacterial effects of poly(2-(dimethylamino ethyl)methacrylate) against selected gram-positive and gram-negative bacteria

Antimicrobial coatings can reduce the occurrence of medical device-related bacterial infections. Poly(2-(dimethylamino ethyl)methacrylate) (pDMAEMA) is one such polymer that is being researched in this regard. The aims of this study were to (1) elucidate pDMAEMA's antimicrobial activity against a range of Gram-positive and Gram-negative bacteria and (2) to investigate its antimicrobial mode of action. The methods used include determination of minimum inhibitory concentration (MIC) values against various bacteria and the effect of pH and temperature on antimicrobial activity. The ability of pDMAEMA to permeabilise bacterial membranes was determined using the dyes 1-N-phenyl-naphthylamine and calcein-AM. Flow cytometry was used to investigate pDMAEMA's capacity to be internalized by bacteria and to determine effects on bacterial cell cycling. pDMAEMA was bacteriostatic against Gram-negative bacteria with MIC values between 0.1-1 mg/mL. MIC values against Gram-positive bacteria were variable. pDMAEMA was active against Gram-positive bacteria around its pK(a) and at lower pH values, while it was active against Gram-negative bacteria around its pK(a) and at higher pH values. pDMAEMA inhibited bacterial growth by binding to the outside of the bacteria, permeabilizing the outer membrane and disrupting the cytoplasmic membrane. By incorporating pDMAEMA with erythromycin, it was found that the efficacy of the latter was increased against Gram-negative bacteria. Together, the results illustrate that pDMAEMA acts in a similar fashion to other cationic biocides.