Characterization of the membrane-destabilizing properties of different pH-sensitive methacrylic acid copolymers

Amino-Acid-Derived Anionic Polyacrylamides with Tailored Hydrophobicity-Physicochemical Properties and Cellular Interactions

Polyanions can internalize into cells via endocytosis without any cell disruption and are therefore interesting materials for biomedical applications. In this study, amino-acid-derived polyanions with different alkyl side-chains are synthesized via postpolymerization modification of poly(pentafluorophenyl acrylate), which is synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerization, to obtain polyanions with tailored hydrophobicity and alkyl branching. The success of the reaction is verified by size-exclusion chromatography, NMR spectroscopy, and infrared spectroscopy. The hydrophobicity, surface charge, and pH dependence are investigated in detail by titrations, high-performance liquid chromatography, and partition coefficient measurements. Remarkably, the determined pK a-values for all synthesized polyanions are very similar to those of poly(acrylic acid) (pK a = 4.5), despite detectable differences in hydrophobicity. Interactions between amino-acid-derived polyanions with L929 fibroblasts reveal very slow cell association as well as accumulation of polymers in the cell membrane. Notably, the more hydrophobic amino-acid-derived polyanions show higher cell association. Our results emphasize the importance of macromolecular engineering toward ideal charge and hydrophobicity for polymer association with cell membranes and internalization. This study further highlights the potential of amino-acid-derived polymers and the diversity they provide for tailoring properties toward drug delivery applications.

Fluorine-Functionalized Polyphosphazene Immunoadjuvant: Synthesis, Solution Behavior and In Vivo Potency

The inclusion of fluorine motifs in drugs and drug delivery systems is an established tool for modulating their biological potency. Fluorination can improve drug specificity or boost the vehicle's ability to cross cellular membranes. However, the approach has yet to be applied to vaccine adjuvants. Herein, the synthesis of fluorinated bioisostere of a clinical stage immunoadjuvant-poly[di(carboxylatophenoxy)phosphazene], PCPP-is reported. The structure of water-soluble fluoropolymer-PCPP-F, which contains two fluorine atoms per repeat unit-was confirmed using 1H, 31P and 19F NMR, and its molecular mass and molecular dimensions were determined using size-exclusion chromatography and dynamic light scattering. Insertion of fluorine atoms in the polymer side group resulted in an improved solubility in acidic solutions and faster hydrolytic degradation rate, while the ability to self-assemble with an antigenic protein, lysozyme-an important feature of polyphosphazene vaccine adjuvants-was preserved. In vivo assessment of PCPP-F demonstrated its greater ability to induce antibody responses to Hepatitis C virus antigen when compared to its non-fluorinated counterpart. Taken together, the superior immunoadjuvant activity of PCPP-F, along with its improved formulation characteristics, demonstrate advantages of the fluorination approach for the development of this family of macromolecular vaccine adjuvants.

Synthesis and Characterization of Linear Copolymers Based on Pharmaceutically Functionalized Monomeric Choline Ionic Liquid for Delivery of p-Aminosalicylate

Bioactive linear poly(ionic liquid)s (PIL) were designed as carriers in drug delivery systems (DDS). Their synthesis was based on a monomeric ionic liquid (MIL) with a relevant pharmaceutical anion to create therapeutically functionalized monomers, which further can be used in the controlled atom transfer radical polymerization (ATRP). The presence of chloride counterions in the quaternary ammonium groups of choline MIL, e.g., [2-(methacryloyloxy)ethyl]trimethyl-ammonium chloride (ChMACl), was stimulated to undergo the anion exchange with p-aminosalicylate sodium salt (NaPAS) as the source of the pharmaceutical anion with antibacterial activity. The resultant [2-(methacryloyloxy)ethyl]trimethylammonium p-aminosalicylate (ChMAPAS) was copolymerized to attain the well-defined linear choline-based copolymers with various contents of PAS anions (24–42%), which were regulated by the initial ratio of ChMAPAS to MMA and conversion degree. The length of polymeric chains was evaluated by the total monomer conversion (31–66%) yielding degree of polymerization (DPn = 133–272). Depending on the polymer carrier composition, PAS anions were exchanged by 60–100% within 1 h, 80–100% within 4 h, and completely after 24 h by phosphate anions in PBS imitating a physiological fluid.

Nano-Assembly of Quisinostat and Biodegradable Macromolecular Carrier Results in Supramolecular Complexes with Slow-Release Capabilities

Self-assembly of ionically charged small molecule drugs with water-soluble biodegradable polyelectrolytes into nano-scale complexes can potentially offer a novel and attractive approach to improving drug solubility and prolonging its half-life. Nanoassemblies of quisinostat with water-soluble PEGylated anionic polyphosphazene were prepared by gradient-driven escape of solvent resulting in the reduction of solvent quality for a small molecule drug. A study of binding, analysis of composition, stability, and release profiles was conducted using asymmetric flow field flow fractionation (AF4) and dynamic light scattering (DLS) spectroscopy. Potency assays were performed with WM115 human melanoma and A549 human lung cancer cell lines. The resulting nano-complexes contained up to 100 drug molecules per macromolecular chain and displayed excellent water-solubility and improved hemocompatibility when compared to co-solvent-based drug formulations. Quisinostat release time (complex dissociation) at near physiological conditions in vitro varied from 5 to 14 days depending on initial drug loading. Multimeric complexes displayed dose-dependent potency in cell-based assays and the results were analyzed as a function of complex concentration, as well as total content of drug in the system. The proposed self-assembly process may present a simple alternative to more sophisticated delivery modalities, namely chemically conjugated prodrug systems and nanoencapsulation-based formulations.

Design of Polymeric Carriers for Intracellular Peptide Delivery in Oncology Applications

In recent decades, peptides, which can possess high potency, excellent selectivity, and low toxicity, have emerged as promising therapeutics for cancer applications. Combined with an improved understanding of tumor biology and immuno-oncology, peptides have demonstrated robust antitumor efficacy in preclinical tumor models. However, the translation of peptides with intracellular targets into clinical therapies has been severely hindered by limitations in their intrinsic structure, such as low systemic stability, rapid clearance, and poor membrane permeability, that impede intracellular delivery. In this Review, we summarize recent advances in polymer-mediated intracellular delivery of peptides for cancer therapy, including both therapeutic peptides and peptide antigens. We highlight strategies to engineer polymeric materials to increase peptide delivery efficiency, especially cytosolic delivery, which plays a crucial role in potentiating peptide-based therapies. Finally, we discuss future opportunities for peptides in cancer treatment, with an emphasis on the design of polymer nanocarriers for optimized peptide delivery.

Functionalized Particles Designed for Targeted Delivery

Pure bioactive compounds alone can only be exceptionally administered in medical treatment. Usually, drugs are produced as various forms of active compounds and auxiliary substances, combinations assuring the desired healing functions. One of the important drug forms is represented by a combination of active substances and particle-shaped polymer in the nano- or micrometer size range. The review describes recent progress in this field balanced with basic information. After a brief introduction, the paper presents a concise overview of polymers used as components of nano- and microparticle drug carriers. Thereafter, progress in direct synthesis of polymer particles with functional groups is discussed. A section is devoted to formation of particles by self-assembly of homo- and copolymer-bearing functional groups. Special attention is focused on modification of the primary functional groups introduced during particle preparation, including introduction of ligands promoting anchorage of particles onto the chosen living cell types by interactions with specific receptors present in cell membranes. Particular attention is focused on progress in methods suitable for preparation of particles loaded with bioactive substances. The review ends with a brief discussion of the still not answered questions and unsolved problems.

Next generation polyphosphazene immunoadjuvant: Synthesis, self-assembly and in vivo potency with human papillomavirus VLPs-based vaccine

Poly[di(carboxylatomethylphenoxy)phosphazene] (PCMP), a new member of polyphosphazene immunoadjuvant family, is synthesized. In vitro assessment of a new macromolecule revealed hydrolytic degradation profile and immunostimulatory activity comparable to its clinical stage homologue PCPP; however, PCMP was characterized by a beneficial reduced sensitivity to the ionic environment. In vivo evaluation of PCMP potency was conducted with human papillomavirus (HPV) virus-like particles (VLPs) based RG1-VLPs vaccine. In contrast with previously reported self-assembly of polyphosphazene adjuvants with proteins, which typically results in the formation of complexes with multimeric display of antigens, PCMP surface modified VLPs in a composition dependent pattern, which at a high polymer-to VLPs ratio led to stabilization of antigenic particles. Immunization experiments in mice demonstrated that PCMP adjuvanted RG1-VLPs vaccine induced potent humoral immune responses, in particular, on the level of highly desirable protective cross-neutralizing antibodies, and outperformed PCPP and Alhydrogel adjuvanted formulations.

pH-Responsive Amphiphilic Carboxylate Polymers: Design and Potential for Endosomal Escape

The intracellular delivery of emerging biomacromolecular therapeutics, such as genes, peptides, and proteins, remains a great challenge. Unlike small hydrophobic drugs, these biotherapeutics are impermeable to the cell membrane, thus relying on the endocytic pathways for cell entry. After endocytosis, they are entrapped in the endosomes and finally degraded in lysosomes. To overcome these barriers, many carriers have been developed to facilitate the endosomal escape of these biomacromolecules. This mini-review focuses on the development of anionic pH-responsive amphiphilic carboxylate polymers for endosomal escape applications, including the design and synthesis of these polymers, the mechanistic insights of their endosomal escape capability, the challenges in the field, and future opportunities.

Polymeric matrix hydrophobicity governs saponin packing-density on nanoparticle surface and the subsequent biological interactions

This study investigated the loading behavior of Quillaja saponin as a model surface-active cargo on (NP) nanoparticles prepared with various hydrophobic polymers and using different organic solvents through emulsification/solvent evaporation, and the impact of NP surface hydrophobicity upon the cytotoxic and hemolytic properties of the loaded entity. A superficial monolayered arrangement of saponins on NP was established (R² > 0.9) for all NP, as the saponin loading values complied with the Langmuir adsorption isotherm over the entire concentration range. Next, based on the measurement of interfacial tension between formulation phases, and the subsequent use of Gibb's adsorption isotherm, the packing density (Г_exc) and loading of saponins on various nanospheres could be predicted with good correlation with the actual values (R² > 0.95). The results demonstrated that the hydrophobicity of the polymeric matrix was the major determinant of saponin packing density on the nanospheres. Finally, the impact of NP surface properties upon saponin biological interactions was investigated, where a linear correlation was found between the NP surface hydrophobicity and their hemolytic properties (R² ≅ 0.79), and cytotoxicity against two cancer cell lines (R² > 0.76). The surface hydrophobicity of the polymeric NP seemingly governed the NP-cell membrane binding, which in turn determined the amount of membrane-bound saponins per unit NP surface area. As the saponins exert their cytotoxicity mainly through strong permeabilization of the cell membrane, a higher amount of NP-membrane association governed by a more hydrophobic matrix can lead to higher levels of cytotoxicity. These findings highlight the importance of a detailed characterization of NP surface properties, particularly in case of surface-active cargos, for these dictate the side effects and biological interactions of the delivery system.

Modeling the interaction of amphiphilic polymer nanoparticles with biomembranes to Guide rational design of drug delivery systems

Nanoparticle assisted drug delivery to the cytoplasm is limited by sequestration of nanoparticles in endosomes. Endosomal escape through polymer-induced membrane destabilization is one of a few well characterized mechanisms to overcome it. Aiming to utilize this method in vivo, it is necessary to understand how modulating the structural and chemical features of the polymer and the presence of proteins in biological fluids can affect this activity. Here, as a model for the endosomal membrane, we use the membrane of red blood cells to evaluate the membrane destabilization ability of a model amphiphilic polymer in the presence of blood plasma using a hemolysis assay. This allows determination of red blood cells membrane permeabilization through the quantification of hemoglobin leakage. Our results showed a strong inhibitory effect of plasma, and that hemolytic activity can be improved by chemical modification of the polymeric micelle, reducing its interaction with plasma proteins. Finally, a second mechanism of pH-induced direct diffusion is proposed and tested using an oil/water partitioning model. These results offer a body of knowledge to improve delivery of drugs across biological membranes using carefully designed polymeric nanocarriers.

Stimuli-Responsive Polymeric Nanocarriers for Drug Delivery, Imaging, and Theragnosis

In the past few decades, polymeric nanocarriers have been recognized as promising tools and have gained attention from researchers for their potential to efficiently deliver bioactive compounds, including drugs, proteins, genes, nucleic acids, etc., in pharmaceutical and biomedical applications. Remarkably, these polymeric nanocarriers could be further modified as stimuli-responsive systems based on the mechanism of triggered release, i.e., response to a specific stimulus, either endogenous (pH, enzymes, temperature, redox values, hypoxia, glucose levels) or exogenous (light, magnetism, ultrasound, electrical pulses) for the effective biodistribution and controlled release of drugs or genes at specific sites. Various nanoparticles (NPs) have been functionalized and used as templates for imaging systems in the form of metallic NPs, dendrimers, polymeric NPs, quantum dots, and liposomes. The use of polymeric nanocarriers for imaging and to deliver active compounds has attracted considerable interest in various cancer therapy fields. So-called smart nanopolymer systems are built to respond to certain stimuli such as temperature, pH, light intensity and wavelength, and electrical, magnetic and ultrasonic fields. Many imaging techniques have been explored including optical imaging, magnetic resonance imaging (MRI), nuclear imaging, ultrasound, photoacoustic imaging (PAI), single photon emission computed tomography (SPECT), and positron emission tomography (PET). This review reports on the most recent developments in imaging methods by analyzing examples of smart nanopolymers that can be imaged using one or more imaging techniques. Unique features, including nontoxicity, water solubility, biocompatibility, and the presence of multiple functional groups, designate polymeric nanocues as attractive nanomedicine candidates. In this context, we summarize various classes of multifunctional, polymeric, nano-sized formulations such as liposomes, micelles, nanogels, and dendrimers.

pH-Responsive Nanofibers for Precise and Sequential Delivery of Multiple Payloads

Effective combination therapies can be achieved by programming materials for controlling release sequence, timing, and dose of multiple payloads. Herein, we synthesize dextran esters by coesterification of dextran, which display responsive properties at a precise pH threshold between 5.0 and 7.0. Multilayers electrospun nanofibers are prepared so that three different payloads are entrapped in three different dextran esters. The release of the three drugs can be sequentially and independently activated by a gradual increase of pH value. Because both pH threshold and release kinetics are matching conditions encountered by aliments along the gastrointestinal tract, these dextran ester multilayer nanofibers are promising for oral drug delivery.

Electrically controlled drug release using pH-sensitive polymer films

Drug delivery systems (DDS) that allow spatially and temporally controlled release of drugs are of particular interest in the field of drug delivery. These systems create opportunities for individually tailored doses of drugs to be administered as well as reduce side effects by localizing the initial drug dose to the organ of interest. We present an electroresponsive DDS in the form of a bioresorbable nanocomposite film which operates at low voltages (<-2 V). The method is based on electrochemically generating local pH changes at an electrode surface to induce dissolution of a pH-sensitive polymer, which is used as the carrier material. We previously demonstrated this proof-of-concept using a poly(methyl methacrylate-co-methacrylic acid) (co-PMMA) copolymer commercially marketed as Eudragit S100 (EGT). However, as EGT is soluble at a pH above 7, experiments were performed in isotonic saline solutions (pH ∼ 6.4). In this work, we have synthesized co-PMMA with a variety of monomer ratios to shift the solubility of the copolymer to higher pH values, and developed a polymer that can be used under physiologically relevant conditions. The generalizability of this system was demonstrated by showing controlled release of different drug molecules with varying parameters like size, hydrophobicity, and pKa. Fluorescein, a hydrophilic model compound, meloxicam, a hydrophobic anti-arthritic medication, curcumin, a small molecule with anti-cancer therapeutic potential, and insulin, a polypeptide hormone used in the treatment of hypoglycemia, could all be released on demand with minimal leakage. The drug loading achieved was ∼32 wt% by weight of the co-polymer.

Tripartite polyionic complex (PIC) micelles as non-viral vectors for mesenchymal stem cell siRNA transfection

In the context of regenerative medicine, the use of RNA interference mechanisms has already proven its efficiency in targeting specific gene expression with the aim of enhancing, accelerating or, more generally, directing stem cell differentiation. However, achievement of good transfection levels requires the use of a gene vector. For in vivo applications, synthetic vectors are an interesting option to avoid possible issues associated with viral vectors (safety, production costs, etc.). Herein, we report on the design of tripartite polyionic complex micelles as original non-viral polymeric vectors suited for mesenchymal stem cell transfection with siRNA. Three micelle formulations were designed to exhibit pH-triggered disassembly in an acidic pH range comparable to that of endosomes. One formulation was selected as the most promising with the highest siRNA loading capacity while clearly maintaining pH-triggered disassembly properties. A thorough investigation of the internalization pathway of micelles into cells with tagged siRNA was made before showing an efficient inhibition of Runx2 expression in primary bone marrow-derived stem cells. This work evidenced PIC micelles as promising synthetic vectors that allow efficient MSC transfection and control over their behavior, from the perspective of their clinical use.

pH-Responsive Schizophrenic Diblock Copolymers Prepared by Polymerization-Induced Self-Assembly

Polymerization-induced self-assembly (PISA) is used for the highly convenient and efficient preparation of ampholytic diblock copolymer nanoparticles directly in acidic aqueous solution. Cationic nanoparticles comprising a protonated polyamine stabilizer block and a hydrophobic polyacid core-forming block are formed at pH 2. Micelle inversion occurs at pH 10 to produce anionic nanoparticles with an ionized polyacid stabilizer block and a hydrophobic polyamine core-forming block. Macroscopic precipitation occurs at around pH 6-7, which lies close to the isoelectric point of this ampholytic diblock copolymer. Incorporation of fluorescein and rhodamine dye labels into the acid and amine blocks, respectively, leads to dual-color bifluorescent self-reporting pH-responsive nanoparticles.

Development of pH-sensitive Dextran Derivatives with Strong Adjuvant Function and Their Application to Antigen Delivery

To achieve efficient cancer immunotherapy, the induction of cytotoxic T lymphocyte-based cellular immunity is necessary. In order to induce cellular immunity, antigen carriers that can deliver antigen into cytosol of antigen presenting cells and can activate these cells are required. We previously developed 3-methyl glutarylated dextran (MGlu-Dex) for cytoplasmic delivery of antigen via membrane disruption ability at weakly acidic pH in endosome/lysosomes. MGlu-Dex-modified liposomes delivered model antigens into cytosol of dendritic cells and induced antigen-specific cellular immunity. However, their antitumor effects were not enough to complete the regression of the tumor. In this study, antigen delivery performance of dextran derivatives was improved by the introduction of more hydrophobic spacer groups next to carboxyl groups. 2-Carboxycyclohexane-1-carboxylated dextran (CHex-Dex) was newly synthesized as pH-responsive dextran derivative. CHex-Dex formed stronger hydrophobic domains at extremely weak acidic pH and destabilized lipid membrane more efficiently than MGlu-Dex. CHex-Dex-modified liposomes were taken up by dendritic cells 10 times higher than MGlu-Dex-modified liposomes and delivered model antigen into cytosol. Furthermore, CHex-Dex achieved 600 times higher IL-12 production from dendritic cells than MGlu-Dex. Therefore, CHex-Dex is promising as multifunctional polysaccharide having both cytoplasmic antigen delivery function and strong activation property of dendritic cells for induction of cellular immunity.

A Freeze-Concentration and Polyampholyte-Modified Liposome-Based Antigen-Delivery System for Effective Immunotherapy

Immunotherapy is an exciting new approach to cancer treatment. The development of a novel freeze-concentration method is described that could be applicable in immunotherapy. The method involves freezing cells in the presence of pH-sensitive, polyampholyte-modified liposomes with encapsulated ovalbumin (OVA) as the antigen. In RAW 264.7 cells, compared to unfrozen, freeze-concentration of polyampholyte-modified liposomes encapsulating OVA resulted in efficient OVA uptake and also allowed its delivery to the cytosol. Efficient delivery of OVA to the cytosol was shown to be partly due to the pH-dependence of the polyampholyte-modified liposomes. Cytosolic OVA delivery also resulted in significant up-regulation of the major histocompatibility complex class I pathway through cross-stimulation, as well as an increase in the release of IL-1β, IL-6, and TNF-α. The results demonstrate that the combination of a simple freeze-concentration method and polyampholyte-modified liposomes might be useful in future immunotherapy applications.

Preparation of dual-stimuli-responsive liposomes using methacrylate-based copolymers with pH and temperature sensitivities for precisely controlled release

Dual-signal-sensitive copolymers were synthesized by copolymerization of methoxy diethylene glycol methacrylate, methacrylic acid, and lauroxy tetraethylene glycol methacrylate, which respectively provide temperature sensitivity, pH sensitivity, and anchoring to liposome surfaces. These novel copolymers, with water solubility that differs depending on temperature and pH, are soluble in water under neutral pH and low-temperature conditions, but they become water-insoluble and form aggregates under acidic pH and high-temperature conditions. Liposomes modified with these copolymers exhibited enhanced content release at weakly acidic pH with increasing temperature, although no temperature-dependent content release was observed in neutral conditions. Interaction between the copolymers and the lipid monolayer at the air-water interface revealed that the copolymer chains penetrate more deeply into the monolayer with increasing temperature at acidic pH than at neutral pH, where the penetration of copolymer chains was moderate and temperature-independent at neutral pH. Interaction of the copolymer-modified liposomes with HeLa cells demonstrated that the copolymer-modified liposomes were adsorbed quickly and efficiently onto the cell surface and that they were internalized more gradually than the unmodified liposomes through endocytosis. Furthermore, the copolymer-modified liposomes enhanced the content release in endosomes with increasing temperature, but no such temperature-dependent enhancement of content release was observed for unmodified liposomes.

Molecular-Level Interactions of Polyphosphazene Immunoadjuvants and Their Potential Role in Antigen Presentation and Cell Stimulation

Two macromolecular immunoadjuvants, poly[di(carboxylatophenoxy)phosphazene], PCPP, and poly[di(carboxylatoethylphenoxy)phosphazene], PCEP, have been investigated for their molecular interactions with model and biopharmaceutically important proteins in solutions, as well as for their TLR stimulatory effects and pH-dependent membrane disruptive activity in cellular assays. Solution interactions between polyphosphazenes and proteins, including antigens and soluble immune receptor proteins, have been studied using Asymmetric Flow Field Flow Fractionation (AF4) and Dynamic Light Scattering (DLS) at near physiological conditions: phosphate buffered saline, pH 7.4. Polyphosphazenes demonstrated selectivity in their molecular interactions with various proteins, but displayed strong binding with all vaccine antigens tested in the present study. It was found that both PCPP and PCEP showed strong avidity to soluble immune receptor proteins, such as Mannose Receptor (MR) and certain Toll-Like Receptor (TLR) proteins. Studies on TLR stimulation in vitro using HEK293 cells with overexpressed human TLRs revealed activation of TLR7, TLR8, and TLR9 signaling pathways, albeit with some nonspecific stimulation, for PCPP and the same pathways plus TLR3 for PCEP. Finally, PCEP, but not PCPP, demonstrated pH-dependent membrane disruptive activity in the pH range corresponding to the pH environment of early endosomes, which may play a role in a cross-presentation of antigenic proteins.

Self-assembly of polyphosphazene immunoadjuvant with poly(ethylene oxide) enables advanced nanoscale delivery modalities and regulated pH-dependent cellular membrane activity

Water-soluble polyphosphazene polyacids, such as poly[di(carboxylatophenoxy)phosphazene] (PCPP), have been of significant interest due to their unique immunoadjuvant and vaccine delivery properties. We report that PCPP can spontaneously self-assemble into intermolecular complexes with common formulation excipients − polyethers in aqueous solutions at neutral pH through the establishment of hydrogen bonds. The resulting advanced PCPP delivery modalities can range from macromolecular assemblies at the nanoscale level to physically cross-linked hydrogels and the physical state can be modulated through varying polymer ratios and molecular weight of polyether. It has been demonstrated that such macromolecular complexes maintain protein-binding ability − a key characteristics of the delivery system. Importantly, the non-covalent modification of PCPP immunoadjuvant with polyethers introduces pH dependent membrane disruptive activity, which is not characteristic for PCPP itself, and is typically correlated to the ability of macromolecular carrier to facilitate endosomal escape. This can potentially affect the mechanism of immunoadjuvant action displayed by PCPP, afford means for its fine-tuning, as well as provide important insights for understanding the relationship between fundamental physico-chemical characteristics of polyphosphazene immunoadjuvants and their activity in vivo.

Gelatin-based nanoparticles as DNA delivery systems: Synthesis, physicochemical and biocompatible characterization

The rapidly rising demand for therapeutic grade DNA molecules requires associated improvements in encapsulation and delivery technologies. One of the challenges for the efficient intracellular delivery of therapeutic biomolecules after their cell internalization by endocytosis is to manipulate the non-productive trafficking from endosomes to lysosomes, where degradation may occur. The combination of the endosomal acidity with the endosomolytic capability of the nanocarrier can increase the intracellular delivery of many drugs, genes and proteins, which, therefore, might enhance their therapeutic efficacy. Among the suitable compounds, the gelification properties of gelatin as well as the strong dependence of gelatin ionization with pH makes this compound an interesting candidate to be used to the effective intracellular delivery of active biomacromolecules. In the present work, gelatin (either high or low gel strength) and protamine sulfate has been selected to form particles by interaction of oppositely charged compounds. Particles in the absence of DNA (binary system) and in the presence of DNA (ternary system) have been prepared. The physicochemical characterization (particle size, polydispersity index and degree of DNA entrapment) have been evaluated. Cytotoxicity experiments have shown that the isolated systems and the resulting gelatin-based nanoparticles are essentially non-toxic. The pH-dependent hemolysis assay and the response of the nanoparticles co-incubated in buffers at defined pHs that mimic extracellular, early endosomal and late endo-lysosomal environments demonstrated that the nanoparticles tend to destabilize and DNA can be successfully released. It was found that, in addition to the imposed compositions, the gel strength of gelatin is a controlling parameter of the final properties of these nanoparticles. The results indicate that these gelatin-based nanoparticles have excellent properties as highly potent and non-toxic intracellular delivery systems, rendering them promising DNA vehicles to be used as non-viral gene delivery systems.

pH-sensitive, polymer modified, plasma stable niosomes: promising carriers for anti-cancer drugs

The aim of this study was the design and evaluation of a novel plasma stable, pH-sensitive niosomal formulation of Mitoxantrone by a modified ethanol injection method. Cholesterol hemisuccinate was added instead of cholesterol in order to produce pH-sensitivity property and using PEG-Poly (monomethyl itaconate)-CholC6 (PEG-PMMI-CholC6) copolymer introduced simultaneously pH-sensitivity and plasma stability properties in prepared niosomes. The pH-sensitivity and cytotoxicity of Mitoxantrone niosomes were evaluated in vitro in phosphate buffer with different pHs as well as using human ovarian cancer cell line (OVCAR-3), human breast cancer cell line (MCF-7) and human umbilical vein endothelial cells (HUVEC). Results showed that both cholesterol derivatives bearing formulations had pH-sensitive property and were found to release their contents under mild acidic conditions rapidly. In addition, the PEG-PMMI-CholC6-based niosomes could reserve the pH-sensitivity after incubation in plasma. Both Mitoxantrone-loaded pH-sensitive niosomes showed higher cytotoxicity than the conventional niosomes on OVCAR-3 and MCF-7 cell lines. However, both pH-sensitive niosomes exhibited lower cytotoxic effect on HUVEC cell line. Plasma stable, pH-sensitive niosomes could improve the cytotoxic effect and reduce the side effects of anti-tumor drugs.

Fabrication of triple responsive polymer brushes and their catalytic performance after loading palladium

The uniformly dispersed and structured silica nanoparticles were prepared and functionalized by amino and 2-bromoisobutyrate successively. The triple responsive polymer brushes were synthesized from the functionalized silica particles by SI-ATRP.

Design and in vitro evaluation of layer by layer siRNA nanovectors targeting breast tumor initiating cells

Efficient therapeutics and early detection has helped to increase breast cancer survival rates over the years. However, the recurrence of breast cancer remains to be a problem and this may be due to the presence of a small population of cells, called tumor initiating cells (TICs). Breast TICs are resistant to drugs, difficult to detect, and exhibit high self-renewal capabilities. In this study, layer by layer (LBL) small interfering RNA (siRNA) nanovectors (SNVs) were designed to target breast TICs. SNVs were fabricated using alternating layers of poly-L-lysine and siRNA molecules on gold (Au) nanoparticle (NP) surfaces. The stability, cell uptake, and release profile for SNVs were examined. In addition, SNVs reduced TIC-related STAT3 expression levels, CD44⁺/CD24⁻/EpCAM⁺ surface marker levels and the number of mammospheres formed compared to the standard transfection agent. The data from this study show, for the first time, that SNVs in LBL assembly effectively delivers STAT3 siRNA and inhibit the growth of breast TICs in vitro.

Poly(ethylene glycol) methacrylate hydrolyzable microspheres for transient vascular embolization

Poly(ethylene glycol) methacrylate (PEGMA) hydrolyzable microspheres intended for biomedical applications were readily prepared from poly(lactide-co-glycolide) (PLGA)-poly(ethylene glycol) (PEG)-PLGA crosslinker and PEGMA as a monomer using a suspension polymerization process. Additional co-monomers, methacrylic acid and 2-methylene-1,3-dioxepane (MDO), were incorporated into the initial formulation to improve the properties of the microspheres. All synthesized microspheres were spherical in shape, calibrated in the 300-500 μm range, swelled in phosphate-buffered saline (PBS) and easily injectable through a microcatheter. Hydrolytic degradation experiments performed in PBS at 37 °C showed that all of the formulations tested were totally degraded in less than 2 days. The resulting degradation products were a mixture of low-molecular-weight compounds (PEG, lactic and glycolic acids) and water-soluble polymethacrylate chains having molecular weights below the threshold for renal filtration of 50 kg mol(-1) for the microspheres containing MDO. Both the microspheres and the degradation products were determined to exhibit minimal cytotoxicity against L929 fibroblasts. Additionally, in vivo implantation in a subcutaneous rabbit model supported the in vitro results of a rapid degradation rate of microspheres and provided only a mild and transient inflammatory reaction comparable to that of the control group.

Spatial-temporal event adaptive characteristics of nanocarrier drug delivery in cancer therapy

In cancer therapy, drug delivery is a complex process that aims to transit the cargo to the destination with as little damage to the normal tissue as possible. In the last decade, tremendous development and research on nanomedicine have been exploring an ideal system with efficient drug transportation and release property. For this end, series of barriers need to be circumvented by nanomedicine, including systemic barriers, such as biosurface adsorption, phagocytic clearance, bloodstream washing, interstitial pressure, degradation, as well as intracellular barriers, such as cell membrane reorganization and internalization, endo/lysosomal escape, cytosolic or subcellular localization. Rather than being random, these barriers follow a specific spatial-temporal sequence. Therefore, the nanocarriers have to be endowed with characteristics that are adaptive to particular biological milieu on systemic and intracellular levels. To this end, we reviewed the correlations between the spatial-temporal sequences of drug delivery and nanocarrier characteristics in cancer therapy, as well as strategies to achieve efficient drug delivery upon both systemic and intracellular levels.

Cytocompatibility and P-glycoprotein inhibition of block copolymers: structure-activity relationship

Amphiphilic polymeric micelles greatly improve the solubilization and sustained release of hydrophobic drugs and provide a protective environment for the cargo molecules in aqueous media, which favors lower drug administration doses, reduces adverse side effects, and increases blood circulation times and passive targeting to specific cells. These capabilities depend, among other variables, on the structure and composition of the polymer chains. Composition and, in particular, block length have been shown to play an important role in the modification of cellular responses such as drug internalization processes or transduction pathways when polymeric unimer/micelles are in close contact with cells. Here we present a detailed study about the role copolymer structure and composition play on cell viability and cellular response of several cell lines. To do that, more than 30 structurally related copolymers with diblock and triblock architectures containing different hydrophobic blocks and poly(ethylene oxide) as the common hydrophilic unit have been analyzed regarding cytocompatibility and potential as "active" cell response modifiers by testing their influence on the P-gp pump efflux mechanism responsible of multidrug resistance in cancerous cells. An empirical threshold for cell viability could be established at a copolymer EO/POeffective value above ca. 1.5 for copolymers with triblock structure, whereas no empirical rule could be observed for diblocks. Moreover, some of the tested copolymers (e.g., BO12EO227BO12 and EO57PO46EO57 that notably increased and C16EO455C16 that decreased the P-gp ATPase activity) were observed to act as efficient inhibitors of the P-gp efflux pump promoting an enhanced doxorubicin (DOXO) accumulation inside multidrug resistant (MDR) NCI-ADR-RES cells.

Polymeric micelles based on poly(methacrylic acid) block-containing copolymers with different membrane destabilizing properties for cellular drug delivery

Poly(methacrylic acid)-b-poly(ethylene oxide) are double hydrophilic block copolymers, which are able to form micelles by complexation with a counter-polycation, such as poly-l-lysine. A study was carried out on the ability of the copolymers to interact with model membranes as a function of their molecular weights and as a function of pH. Different behaviors were observed: high molecular weight copolymers respect the membrane integrity, whereas low molecular weight copolymers with a well-chosen asymmetry degree can induce a membrane alteration. Hence by choosing the appropriate molecular weight, micelles with distinct membrane interaction behaviors can be obtained leading to different intracellular traffics with or without endosomal escape, making them interesting tools for cell engineering. Especially micelles constituted of low molecular weight copolymers could exhibit the endosomal escape property, which opens vast therapeutic applications. Moreover micelles possess a homogeneous nanometric size and show variable properties of disassembly at acidic pH, of stability in physiological conditions, and finally of cyto-tolerance.

A review of the current status of siRNA nanomedicines in the treatment of cancer

RNA interference currently offers new opportunities for gene therapy by the specific extinction of targeted gene(s) in cancer diseases. However, the main challenge for nucleic acid delivery still remains its efficacy through intravenous administration. Over the last decade, many delivery systems have been developed and optimized to encapsulate siRNA and to specifically promote their delivery into tumor cells and improve their pharmacokinetics for anti-cancer purposes. This review aims to sum up the potential targets in numerous pathways and the properties of recently optimized siRNA synthetic nanomedicines with their preclinical applications and efficacy. Future perspectives in cancer treatment are discussed including promising concomitant treatment with chemotherapies or other siRNA. The outcomes in human clinical trials are also presented.

Lysine-based surfactants in nanovesicle formulations: the role of cationic charge position and hydrophobicity in in vitro cytotoxicity and intracellular delivery

Understanding nanomaterial interactions within cells is of increasing importance for assessing their toxicity and cellular transport. Here, the authors developed nanovesicles containing bioactive cationic lysine-based amphiphiles and assessed whether these cationic compounds increase the likelihood of intracellular delivery and modulate toxicity. Different cytotoxic responses were found among the formulations, depending on surfactant, cell line and endpoint assayed. The induction of mitochondrial dysfunction, oxidative stress and apoptosis were the general mechanisms underlying cytotoxicity. Fluorescence microscopy analysis demonstrated that nanovesicles were internalised by HeLa cells and evidenced that their ability to release endocytosed materials into cell cytoplasm depends on the structural parameters of amphiphiles. The cationic charge position and hydrophobicity of surfactants determine the nanovesicle interactions within the cell and, thus, the resulting toxicity and intracellular behaviour after cell uptake of the nanomaterial. The insights into some toxicity mechanisms of these new nanomaterials contribute in reducing the uncertainty surrounding their potential health hazards.

Interactions of nanomaterials and biological systems: Implications to personalized nanomedicine

The application of nanotechnology to personalized medicine provides an unprecedented opportunity to improve the treatment of many diseases. Nanomaterials offer several advantages as therapeutic and diagnostic tools due to design flexibility, small sizes, large surface-to-volume ratio, and ease of surface modification with multivalent ligands to increase avidity for target molecules. Nanomaterials can be engineered to interact with specific biological components, allowing them to benefit from the insights provided by personalized medicine techniques. To tailor these interactions, a comprehensive knowledge of how nanomaterials interact with biological systems is critical. Herein, we discuss how the interactions of nanomaterials with biological systems can guide their design for diagnostic, imaging and drug delivery purposes. A general overview of nanomaterials under investigation is provided with an emphasis on systems that have reached clinical trials. Finally, considerations for the development of personalized nanomedicines are summarized such as the potential toxicity, scientific and technical challenges in fabricating them, and regulatory and ethical issues raised by the utilization of nanomaterials.

Differential modulation of intracellular survival of cytosolic and vacuolar pathogens by curcumin

Curcumin, a principal component of turmeric, acts as an immunomodulator regulating the host defenses in response to a diseased condition. The role of curcumin in controlling certain infectious diseases is highly controversial. It is known to alleviate symptoms of Helicobacter pylori infection and exacerbate that of Leishmania infection. We have evaluated the role of curcumin in modulating the fate of various intracellular bacterial pathogens. We show that pretreatment of macrophages with curcumin attenuates the infections caused by Shigella flexneri (clinical isolates) and Listeria monocytogenes and aggravates those caused by Salmonella enterica serovar Typhi CT18 (a clinical isolate), Salmonella enterica serovar Typhimurium, Staphylococcus aureus, and Yersinia enterocolitica. Thus, the antimicrobial nature of curcumin is not a general phenomenon. It modulated the intracellular survival of cytosolic (S. flexneri and L. monocytogenes) and vacuolar (Salmonella spp., Y. enterocolitica, and S. aureus) bacteria in distinct ways. Through colocalization experiments, we demonstrated that curcumin prevented the active phagosomal escape of cytosolic pathogens and enhanced the active inhibition of lysosomal fusion by vacuolar pathogens. A chloroquine resistance assay confirmed that curcumin retarded the escape of the cytosolic pathogens, thus reducing their inter- and intracellular spread. We have demonstrated that the membrane-stabilizing activity of curcumin is crucial for its differential effect on the virulence of the bacteria.

Synthesis, characterization, and in vivo efficacy evaluation of PGG-docetaxel conjugate for potential cancer chemotherapy

Aim

This work is intended to develop and evaluate a biopolymeric poly(L-γ-glutamylglutamine) (PGG)–docetaxel (DTX) conjugate that can spontaneously self-assemble in aqueous solutions to become nanoparticles.

Methods

DTX was covalently attached to hydrophilic PGG by direct esterification, and the conjugate was characterized by proton nuclear magnetic resonance spectroscopy, molecular weight gel permeation chromatography, solubility, size distribution and morphology, and hemolysis. Conjugated DTX was found to have 2000 times improved water solubility compared with free DTX. Dynamic light scattering, transmission electron microscopy, and atomic force microscopy revealed the particle size, distribution and morphology of the PGG–DTX conjugate. In addition, the conjugate was further tested for in vitro cytotoxicity and in vivo antitumor efficacy on the human non-small cell lung cancer cell line NCI-H460.

Results

Conjugated DTX was found to have 2000 times improved water solubility compared with free DTX. The conjugate formed nanoparticles with an average diameter of 30 nm in spherical shape and unimodal particle size distribution. The conjugate exhibited about 2% hemolysis at 10 mg/mL, compared with 56% for Tween 80^® at 0.4 mg/mL, and 33% for Cremophor EL^® at 10 mg/mL. In addition, the conjugate was further tested for in vitro cytotoxicity and in vivo antitumor efficacy on the human non-small cell lung cancer cell line NCI-H460. As expected, conjugated DTX exhibited lower cytotoxicity compared to that of free DTX, in concentration-dependent manner. However, PGG–DTX showed better antitumor activity in NCI-H460 lung cancer-bearing mice with minimal weight loss compared to that of free DTX.

Conclusion

The PGG–DTX conjugate may be considered as an attractive and promising polymeric DTX conjugate for non-small cell lung cancer treatment.

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.