Disulfide-functional poly(amido amine)s with tunable degradability for gene delivery

A poly(amidoamine)-based polymeric nanoparticle platform for efficient in vivo delivery of mRNA

The successful use of mRNA vaccines enabled and accelerated the development of several new vaccine candidates and therapeutics based on the delivery of mRNA. In this study, we developed bioreducible poly(amidoamine)-based polymeric nanoparticles (PAA PNPs) for the delivery of mRNA with improved transfection efficiency. The polymers were functionalized with chloroquinoline (Q) moieties for improved endosomal escape and further stabilization of the mRNA-polymer construct. Moreover, these PAAQ polymers were covalently assembled around a core of multi-armed ethylenediamine (Mw 800, 2 % w/w) to form a pre-organized polymeric scaffolded PAAQ (ps-PAAQ) as a precursor for the formation of the mRNA-loaded nanoparticles. Transfection of mammalian cell lines with EGFP mRNA loaded into these PNPs showed a favorable effect of the Q incorporation on GFP protein expression. Additionally, these ps-PAAQ NPs were co-formulated with PEG-polymer coatings to shield the positive surface charge for increased stability and better in vivo applicability. The ps-PAAQ NPs coated with PEG-polymer displayed smaller particle size, electroneutral surface charge, and higher thermal stability. Importantly, these nanoparticles with both Q and PEG-polymer coating induced significantly higher luciferase activity in mice muscle than uncoated ps-PAAQ NPs, following intramuscular injection of PNPs loaded with luciferase mRNA. The developed technology is broadly applicable and holds promise for the development of new nucleotide-based vaccines and therapeutics in a range of infectious and chronic diseases.

A Trojan Horse Delivery Vehicle Carrying siRNA Nanotherapeutics with Multiple Tumor Microenvironment Responsiveness Elicits Robust Antitumor Immune Responses In Situ via a "Self-Synergistic" Approach

The potential of small interfering RNAs (siRNAs) in the treatment of malignant tumors has attracted increasing attention due to their inherent advantages. However, their therapeutic performance strongly depends on the efficiency of their cytoplasmic delivery in vivo by the delivery vehicle with good cellular permeability and histocompatibility. Herein, a polycationic carrier camouflaged with macrophage membrane (MPM) is constructed biomimetically, which is condensed from endogenous spermine monomers through diselenide bonds. The developed Trojan horse delivery vehicle has desirable compression efficacy for siRNA oligo against PD-L1 (siPDL1) as well as intracytoplasmic release properties derived from its sequential degradation triggered by redox microenvironment in tumor cells. Furthermore, the coloading of photosensitizer can mediate photodynamic therapy (PDT) accompanied by the generation of reactive oxygen species (ROS) upon light irradiation applied, which accelerated the degradation of the carrier as well as the release of cargoes while enhancing the PD-L1 blockage-mediated immunotherapy by inducing in-situ immunogenic cell death. Moreover, the synchronously delivered siPDL1 attenuated the ROS-induced increase in immunosuppressive PD-L1 expression, thereby effectively eliciting a robust antitumor immune response with a "self-synergistic" manner in the xenograft breast cancer mouse model.

A New Strategy for Nucleic Acid Delivery and Protein Expression Using Biocompatible Nanohydrogels of Predefined Sizes

We have developed new formulations of nanohydrogels (NHGs) complexed with DNA devoid of cell toxicity, which, together with their tuned sizes, makes them of great interest for delivering DNA/RNA for foreign protein expression. Transfection results demonstrate that, unlike classical lipo/polyplexes, the new NHGs can be incubated indefinitely with cells without apparent cellular toxicity, resulting in the high expression of foreign proteins for long periods of time. Although protein expression starts with a delay as compared to classical systems, it is sustained for a long period of time, even after passing cells without observation of toxicity. A fluorescently labelled NHG used for gene delivery was detected inside cells very early after incubation, but the protein expression was delayed by many days, demonstrating that there is a time-dependent release of genes from the NHGs. We suggest that this delay is due to the slow but continuous release of DNA from the particles concomitantly with slow but continuous protein expression. Additionally, results obtained after the in vivo administration of m-Cherry/NHG complexes indicated a delayed but prolonged expression of the marker gene in the tissue of administration. Overall, we have demonstrated gene delivery and foreign protein expression using GFP and m-Cherry marker genes complexed with biocompatible nanohydrogels.

Tailoring biomimetic dual-redox-responsive nanoplexes for enhanced RNAi-synergized photodynamic cancer immunotherapy

Despite the strong potential of RNA interference (RNAi) therapies, critical issues, such as poor permeability across biological membranes and efficacy of their delivery into the cytoplasm, remain to be addressed before their successful clinical application. The current study aimed to address these issues by constructing a biomimetic nanoplex with dual redox responsiveness, which is derived from a cationic polymer formed by the condensation of endogenous spermine monomers via diselenide bonds. The developed nanoplexes decomposed in response to the redox microenvironment in cancer cells, thereby avoiding accumulation toxicity and poor transfection efficiency owing to incomplete siRNA release. When co-delivered with siPDL1 and a photosensitizer, the reactive oxygen species generated by irradiated nanoplexes accelerated the cytoplasmic release of siPDL1, which was expected to alleviate the PDT-induced increase in immunosuppressive PD-L1 expression. In a murine model of 4T1 xenografted breast cancer, the fabricated macrophage membrane (MPM)-camouflaged nanoplexes with payloads boosted antitumor immune responses in situ through a "self-synergistic" immunogenic cell death induced by photodynamic therapy (PDT). Overall, the study reported a new strategy for harnessing photodynamic immunotherapy for treating immunologically cold tumors. STATEMENT OF SIGNIFICANCE: This study provides a biomimetic nanoplex with dual redox responsiveness, which is derived from a novel cationic polymer formed by the condensation of endogenous spermine monomers through diselenide bonds. The developed nanoplex disassembles according to the redox microenvironment in cancer cells, thereby avoiding accumulation toxicity and poor transfection efficiency due to incomplete siRNA release. When co-delivery of siPDL1 and photosensitizer in vivo, the ROS generated by irradiated nanoplexes accelerated the cytoplasmic release of siPDL1, and which is expected to alleviate PDT-induced increase in immunosuppressive PD-L1 expression, thereby boosting antitumor immune responses in situ through a "self-synergistic" immunogenic cell death induced by PDT. Our findings reveal a new strategy of harnessing photodynamic immunotherapy therapy toward immunologically cold tumors.

Enhancing Cellular Internalization of Single-Chain Polymer Nanoparticles via Polyplex Formation

Intracellular delivery of nanoparticles is crucial in nanomedicine to reach optimal delivery of therapeutics and imaging agents. Single-chain polymer nanoparticles (SCNPs) are an interesting class of nanoparticles due to their unique site range of 5-20 nm. The intracellular delivery of SCNPs can be enhanced by using delivery agents. Here, a positive polymer is used to form polyplexes with SCNPs, similar to the strategy of protein and gene delivery. The size and surface charge of the polyplexes were evaluated. The cellular uptake showed rapid uptake of SCNPs via polyplex formation, and the cytosolic delivery of the SCNPs was presented by confocal microscopy. The ability of SCNPs to act as nanocarriers was further explored by conjugation of doxorubicin.

Polymeric Nanoparticles for Drug Delivery in Osteoarthritis

Osteoarthritis (OA) is a degenerative musculoskeletal disorder affecting the whole synovial joint and globally impacts more than one in five individuals aged 40 and over, representing a huge socioeconomic burden. Drug penetration into and retention within the joints are major challenges in the development of regenerative therapies for OA. During the recent years, polymeric nanoparticles (PNPs) have emerged as promising drug carrier candidates due to their biodegradable properties, nanoscale structure, functional versatility, and reproducible manufacturing, which makes them particularly attractive for cartilage penetration and joint retention. In this review, we discuss the current development state of natural and synthetic PNPs for drug delivery and OA treatment. Evidence from in vitro and pre-clinical in vivo studies is used to show how disease pathology and key cellular pathways of joint inflammation are modulated by these nanoparticle-based therapies. Furthermore, we compare the biodegradability and surface modification of these nanocarriers in relation to the drug release profile and tissue targeting. Finally, the main challenges for nanoparticle delivery to the cartilage are discussed, as a function of disease state and physicochemical properties of PNPs such as size and surface charge.

Poly(disulfide)s: From Synthesis to Drug Delivery

Bioresponsive polymers have been widely used in drug delivery because of their degradability. For example, poly(disulfide)s with repeating disulfide bonds in the main chain have attracted considerable research attention. The characteristics of the disulfide bonds, including their dynamic and reversible properties and their responsiveness to stimuli such as reductants, light, heat, and mechanical force, make them ideal platforms for on-demand drug delivery. This review introduces the synthesis methods and applications of poly(disulfide)s. Furthermore, the synthesis methods of poly(disulfide)s are classified on the basis of the monomers used: oxidative step-growth polymerization with dithiols, ring-opening polymerization with cyclic disulfides, and polymerization with linear disulfides. In addition, recent advances in poly(disulfide)s for the delivery of small-molecule or biomacromolecular drugs are discussed. Quantum-dot-loaded poly(disulfide) delivery systems for imaging are also included. This review provides an overview of the various design strategies employed in the construction of poly(disulfide) platforms to inspire new applications in the field of drug delivery.

Superstable and Large-Scalable Organosilica-Micellar Hybrid Nanosystem via a Confined Gelation Strategy for Ultrahigh-Dosage Chemotherapy

Although various drug nanocarriers have been developed for treating solid tumors, their clinical transformation is greatly limited by the difficulties in quantity production and unpredictable in vivo toxic effects. Herein, a facile "confined-gelation" strategy is developed to quantity-produce intelligent pluronic organosilica micelles (designated as IPOMs) with an undetectable critical micelle concentration (CMC), which features the self-assembly induced core confinement by block copolymers, the inner hydrolysis-condensation of silane to the oligomer skeleton, and oxidative cross-linking of disulfide skeleton to core gelation. The docetaxel-loaded IPOMs (DTX@IPOMs) with precise glutathione (GSH) responsiveness not only display an ultrahigh tolerated dose (360 mg/kg) in healthy Kunming mice model but also exhibit a remarkable tumor inhibition efficacy in both subcutaneous and orthotopic mice tumor models upon an extraordinarily large dosage (50 mg/kg). The present confined-gelation strategy provides a novel pathway to design and quantity-produce low-toxic and high-efficacy organic-inorganic hybrid nanodrugs in future clinical transformations.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Disulfide Bridging Strategies in Viral and Nonviral Platforms for Nucleic Acid Delivery

Self-assembled nanostructures that are sensitive to environmental stimuli are promising nanomaterials for drug delivery. In this class, disulfide-containing redox-sensitive strategies have gained enormous attention because of their wide applicability and simplicity of nanoparticle design. In the context of nucleic acid delivery, numerous disulfide-based materials have been designed by relying on covalent or noncovalent interactions. In this review, we highlight major advances in the design of disulfide-containing materials for nucleic acid encapsulation, including covalent nucleic acid conjugates, viral vectors or virus-like particles, dendrimers, peptides, polymers, lipids, hydrogels, inorganic nanoparticles, and nucleic acid nanostructures. Our discussion will focus on the context of the design of materials and their impact on addressing the current shortcomings in the intracellular delivery of nucleic acids.

Semi-Crystalline Hydrophobic Polyamidoamines: A New Family of Technological Materials?

The hitherto known polyamidoamines (PAAs) are not suitable as structural materials because they are usually water-soluble or swellable in water. This paper deals with the synthesis and characterization of semi-crystalline hydrophobic PAAs (H-PAAs) by combining different bis-sec-amines with bis-acrylamides obtained from C6–C12 bis-prim-amines. H-PAAs were initially obtained in a solution of benzyl alcohol, a solvent suitable for both monomers and polymers. Their number average molecular weights, M¯n, which were determined with ¹H-NMR by evaluating the percentage of their terminal units, varied from 6000 to >10,000. The solubility, thermal properties, ignitability and water resistance of H-PAAs were determined. They were soluble in organic solvents, semi-crystalline and thermally stable. The most promising ones were also prepared using a bulk process, which has never been previously reported for PAA synthesis. In the form of films, these H-PAAs were apparently unaffected by water. The films underwent tensile and wettability tests. They showed similar Young moduli (260–263 MPa), whereas the maximum stress and the stress at break depended on the number of methylene groups of the starting bis-acrylamides. Their wettability was somewhat higher than that of common Nylons. Interestingly, none of the H-PAAs considered, either as films or powders, ignited after prolonged exposure to a methane flame.

Polymeric delivery systems for nucleic acid therapeutics: Approaching the clinic

Gene therapy using nucleic acids has many clinical applications for the treatment of diseases with a genetic origin as well as for the development of innovative vaccine formulations. Since nucleic acids in their free form are rapidly degraded by nucleases present in extracellular matrices, have poor pharmacokinetics and hardly pass cellular membranes, carrier systems are required. Suitable carriers that protect the nucleic acid payload against enzymatic attack, prolong circulation time after systemic administration and assist in cellular binding and internalization are needed to develop nucleic acid based drug products. Viral vectors have been investigated and are also clinically used as delivery vehicles. However, some major drawbacks are associated with their use. Therefore there has been substantial attention on the use of non-viral carrier systems based on cationic lipids and polymers. This review focuses on the properties of polymer-based nucleic acid formulations, also referred as polyplexes. Different polymeric systems are summarized, and the cellular barriers polyplexes encounter and ways to tackle these are discussed. Finally attention is given to the clinical status of non-viral nucleic acid formulations.

Polymeric vehicles for nucleic acid delivery

Polymeric vehicles are versatile tools for therapeutic gene delivery. Many polymers-when assembled with nucleic acids into vehicles-can protect the cargo from degradation and clearance in vivo, and facilitate its transport into intracellular compartments. Design options in polymer synthesis yield a comprehensive range of molecules and resulting vehicle formulations. These properties can be manipulated to achieve stronger association with nucleic acid cargo and cells, improved endosomal escape, or sustained delivery depending on the application. Here, we describe current approaches for polymer use and related strategies for gene delivery in preclinical and clinical applications. Polymer vehicles delivering genetic material have already achieved significant therapeutic endpoints in vitro and in animal models. From our perspective, with preclincal assays that better mimic the in vivo environment, improved strategies for target specificity, and scalable techniques for polymer synthesis, the impact of this therapeutic approach will continue to expand.

Highlight on the Mechanism of Linear Polyamidoamine Degradation in Water

This paper aims at elucidating the degradation mechanism of linear polyamidoamines (PAAs) in water. PAAs are synthesized by the aza-Michael polyaddition of prim-monoamines or bis-sec-amines with bisacrylamides. Many PAAs are water-soluble and have potential for biotechnological applications and as flame-retardants. PAAs have long been known to degrade in water at pH ≥ 7, but their degradation mechanism has never been explored in detail. Filling this gap was necessary to assess the suitability of PAAs for the above applications. To this aim, a small library of nine PAAs was expressly synthesized and their degradation mechanism in aqueous solution studied by 1H-NMR in different conditions of pH and temperature. The main degradation mechanism was in all cases the retro-aza-Michael reaction triggered by dilution but, in some cases, hints were detected of concurrent hydrolytic degradation. Most PAAs were stable at pH 4.0; all degraded at pH 7.0 and 9.0. Initially, the degradation rate was faster at pH 9.0 than at pH 7.0, but the percent degradation after 97 days was mostly lower. In most cases, at pH 7.0 the degradation followed first order kinetics. The degradation rates mainly depended on the basicity of the amine monomers. More basic amines acted as better leaving groups.

Dendrimers as efficient nanocarriers for the protection and delivery of bioactive phytochemicals

The genesis of dendrimers can be considered as a revolution in nano-scaled bioactive delivery systems. These structures possess a unique potential in encapsulating/entrapping bioactive ingredients due to their tree-like nature. Therefore, they could swiftly obtain a valuable statue in nutraceutical, pharmaceutical and medical sciences. Phytochemicals, as a large proportion of bioactives, have been studied and used by scholars in several fields of pharmacology, medical, food, and cosmetic for many years. But, the solubility, stability, and bioavailability issues have always been recognized as limiting factors in their application. Therefore, the main aim of this study is representing the use of dendrimers as novel nanocarriers for phytochemical bioactive compounds to deal with these problems. Hence, after a brief review of phytochemical ingredients, the text is commenced with a detailed explanation of dendrimers, including definitions, types, generations, synthesizing methods, and safety issues; then is continued with demonstration of their applications in encapsulation of phytochemical bioactive compounds and their active/passive delivery by dendrimers. Dendrimers provide a vast and appropriate surface to entrap the targeted phytochemical bioactive ingredients. Several parameters can affect the yield of nanoencapsulation by dendrimers, including their generation, type of end groups, surface charge, core structure, pH, and ambient factors. Another important issue of dendrimers is related to their toxicity. Cationic dendrimers, particularly PAMAM can be toxic to body cells through attaching to the cell membranes and disturbing their functions. However, a number of solutions have been suggested to decrease their toxicity.

Functional Polymers and Polymeric Materials From Renewable Alpha-Unsaturated Gamma-Butyrolactones

Sustainable chemistry requires application of green processes and often starting materials originate from renewable resources. Biomass-derived monomers based on five-membered γ-butyrolactone ring represent suitable candidates to replace sources of fossil origin. α-Methylene-γ-butyrolactone, β-hydroxy-α-methylene-γ-butyrolactone, and β- and γ-methyl-α-methylene-γ-butyrolactones bearing exocyclic double bond are available directly by isolation from plants or derived from itaconic or levulinic acids available from biomass feedstock. Exocyclic double bond with structural similarity with methacrylates is highly reactive in chain-growth polymerization. Reaction involves the linking of monomer molecules through vinyl double bonds in the presence of initiators typical for radical, anionic, zwitterionic, group-transfer, organocatalytic, and coordination polymerizations. The formed polymers containing pendant ring are characterized by high glass transition temperature (T g > 195°C) and render decent heat, weathering, scratch, and solvent resistance. The monomers can also be hydrolyzed to open the lactone ring and form water-soluble monomers. Subsequent radical copolymerization in the presence of cross-linker can yield to hydrogels with superior degree of swelling and highly tunable characteristics, depending on the external stimuli. The five-membered lactone ring allows copolymerization of these compounds by ring opening polymerization to provide polyesters with preserved methylene functionality. In addition, both the lactone ring and the methylene double bond can be attacked by amines. Polyaddition with di- or multi-amines leads to functional poly(amidoamines) with properties tunable by structure of the amines. In this mini-review, we summarize the synthetic procedures for preparation of polymeric materials with interesting properties, including thermoplastic elastomers, acrylic latexes, stimuli-sensitive superabsorbent hydrogels, functional biocompatible polyesters, and poly(amidoamines).

Chemical exchange saturation transfer magnetic resonance imaging and its main and potential applications in pre-clinical and clinical studies

Chemical exchange saturation transfer (CEST) imaging is a novel contrast mechanism, relying on the exchange between mobile protons in amide (-NH), amine (-NH2) and hydroxyl (-OH) groups and bulk water. Due to the targeted protons present in endogenous molecules or exogenous compounds applied externally, CEST imaging can respectively, generate endogenous or exogenous contrast. Nowadays, CEST imaging for endogenous contrast has been explored in pre-clinical and clinical studies. Amide CEST, also called amide proton transfer weighted (APT) imaging, generates CEST effect at 3.5 ppm away from the water signal and has been widely investigated. Given the sensitivity to amide proton concentration and pH level, APT imaging has shown robust performance in the assessment of ischemia, brain tumors, breast and prostate cancer as well as neurodegenerative diseases. With advanced methods proposed, pure APT and Nuclear Overhauser Effect (NOE) mediated CEST effects were separately fitted from original APT signal. Using both effects, early but promising results were obtained for glioma patients in the evaluation of tumor response to therapy and patient survival. Compared to amide CEST, amine CEST is also mobile proton concentration and pH dependent, but has a faster exchange rate between amine protons and water. The resultant CEST effect is usually introduced at 1.8-3 ppm. Glutamate and creatine, as two main metabolites with amine groups for CEST imaging, have been applied to quantitatively assess diseases in the central nervous system and muscle system, respectively. Glycosaminoglycan (Gag) as a representative metabolite with hydroxyl groups has also been measured to evaluate the cartilage of knee or intervertebral discs in CEST MRI. Due to limited frequency difference between hydroxyl protons and water, 7T for better spectral separation is preferred over 3T for GagCEST measurement. The applications of CEST MRI with exogenous contrast agents are still quite limited in clinic. While certain diamagnetic CEST agents, such as dynamic-glucose, have been tried in human for brain tumor or neck cancer assessment, most exogenous agents, i.e., paramagnetic CEST agents, are still tested in the pre-clinical stage, mainly due to potential toxicity. Engineered tissues for tissue regeneration and drug delivery have also shown a great potential in CEST imaging, as many of them, such as hydrogel and polyamide materials, contain mobile protons or can be incorporated with CEST specific chemical compounds. These engineered tissues can thus generate CEST effect in vivo, allowing a possibility to understand the fate of them in vivo longitudinally. Although the CEST MRI with engineered tissues has only been established in early stage, the obtained first evidence is crucial for further optimizing these biomaterials and finally accomplishing the translation into clinical use.

A biodegradable nanocapsule delivers a Cas9 ribonucleoprotein complex for in vivo genome editing

Delivery technologies for the CRISPR-Cas9 (CRISPR, clustered regularly interspaced short palindromic repeats) gene editing system often require viral vectors, which pose safety concerns for therapeutic genome editing1. Alternatively, cationic liposomal components or polymers can be used to encapsulate multiple CRISPR components into large particles (typically >100 nm diameter); however, such systems are limited by variability in the loading of the cargo. Here, we report the design of customizable synthetic nanoparticles for the delivery of Cas9 nuclease and a single-guide RNA (sgRNA) that enables the controlled stoichiometry of CRISPR components and limits the possible safety concerns in vivo. We describe the synthesis of a thin glutathione (GSH)-cleavable covalently crosslinked polymer coating, called a nanocapsule (NC), around a preassembled ribonucleoprotein (RNP) complex between a Cas9 nuclease and an sgRNA. The NC is synthesized by in situ polymerization, has a hydrodynamic diameter of 25 nm and can be customized via facile surface modification. NCs efficiently generate targeted gene edits in vitro without any apparent cytotoxicity. Furthermore, NCs produce robust gene editing in vivo in murine retinal pigment epithelium (RPE) tissue and skeletal muscle after local administration. This customizable NC nanoplatform efficiently delivers CRISPR RNP complexes for in vitro and in vivo somatic gene editing.

Controlled Synthesis of Linear Polyamidoamino Acids

Polyamidoamino acids (PAACs) are synthetic polymers prepared by the polyaddition of bisacrylamides with natural α-amino acids, which in the process maintain both their chirality and their amphoteric nature. This polymerization process is slow, but has the merits of taking place in water and of neither involving protection/de-protection steps nor releasing by-products. However, it leads to polydisperse polymers and, using α-amino acids mixtures, random copolymers. This paper presents a step-by-step polyaddition process leading to homo- and copolymeric PAACs with controlled sequences and controlled molecular weights. It exploits the much different rates of the two Michael addition steps of NH2 of α-amino acids with acrylamides, and the low solubility in organic solvents of the α-amino acid addition products. As a proof of principle, the controlled synthesis of the PAAC from l-arginine and N,N'-methylenebisacrylamide was performed up to a monodisperse product with 11 monomeric units and molecular weight 1840. This synthetic procedure was also tested with l-alanine. All intermediates were isolated and characterized. Noticeably, all of them were α,ω-difunctionalized with either acrylamides or sec-amines and were, in fact, building blocks with potential for preparing complex macromolecular architectures. In a first instance, copolymers with controlled sequences of amidoamine- and amidoamino acid units were prepared.

Degradable, thermo-, pH- and redox-sensitive hydrogel microcapsules for burst and sustained release of drugs

Polymer microcapsules offer a possibility of storing increased amounts of drugs. Appropriate design and composition of the microcapsules allow tuning of the drug-release process. In this paper, we report on synthesis of hydrogel microcapsules sensitive to temperature and pH and degradable by glutathione and hydrogen peroxide. Microcapsules were based on thermo-responsive poly(N-isopropylacrylamide) and degradable cystine crosslinker, and were synthesized by applying precipitation polymerization. Such way of polymerization was appropriately modified to limit the crosslinking in the microcapsule center. This led to a possibility of washing out the pNIPA core at room temperature and the formation of a capsule. Microcapsules revealed rather high drug-loading capacity of ca. 17%. The degradation of the microcapsules by the reducing agent (GSH) and the oxidizing agent (H₂O₂) was confirmed by using the DLS, UV-Vis, SEM and TEM techniques. Depending on pH and concentration of the reducing/oxidizing agents a fast or slow degradation of the microcapsules and a burst or long-term release of doxorubicin (DOX) were observed. The DOX loaded microcapsules appeared to be cytotoxic against A2780 cancer cells similarly to DOX alone, while unloaded microcapsules did not inhibit proliferation of the cells.

Highly branched poly(β-amino ester) delivery of minicircle DNA for transfection of neurodegenerative disease related cells

Current therapies for most neurodegenerative disorders are only symptomatic in nature and do not change the course of the disease. Gene therapy plays an important role in disease modifying therapeutic strategies. Herein, we have designed and optimized a series of highly branched poly(β-amino ester)s (HPAEs) containing biodegradable disulfide units in the HPAE backbone (HPAESS) and guanidine moieties (HPAESG) at the extremities. The optimized polymers are used to deliver minicircle DNA to multipotent adipose derived stem cells (ADSCs) and astrocytes, and high transfection efficiency is achieved (77% in human ADSCs and 52% in primary astrocytes) whilst preserving over 90% cell viability. Furthermore, the top-performing candidate mediates high levels of nerve growth factor (NGF) secretion from astrocytes, causing neurite outgrowth from a model neuron cell line. This synergistic gene delivery system provides a viable method for highly efficient non-viral transfection of ADSCs and astrocytes.

An eximious and affordable GSH stimulus-responsive poly(α-lipoic acid) nanocarrier bonding combretastatin A4 for tumor therapy

A new GSH responsive nano-carrier was developed in a simple way, bonding vascular disrupting agents (VDAs) to achieved long-range treatment of tumors.

A hierarchical assembly strategy to engineer dextran-enveloped polyurethane nanopolyplexes for robust ovarian cancer gene therapy

A hierarchical assembly strategy is herein investigated to generate bio-responsive, dextran-enveloped, bioreducible polyurethane nanopolyplexes for nonviral gene therapy against ovarian tumor. Initially, a group of poly(urethane amine)s were designed and characterized for in vitro gene transfection. The polyurethane containing 1,4-bis(3-aminopropyl)piperazine residue (PUBAP) could induce the best in vitro transfection efficacy against SKOV-3 or A2780 ovarian cancer cells. Next, dextran-enveloped PUBAP polyplexes (e-polyplexes) were constructed by a hierarchical assembly procedure involving gene neutralization with PUBAP and subsequent gene condensation with a cationic dextran (SSDP800). Such dextran comprised dextran (15 kDa) as the main chain and multiple disulfide-linked branched polyethylenimine (BPEI) oligomers as the side grafts. Additionally, folate-dextran-enveloped PUBAP polyplexes (FA-e-polyplexes) were fabricated by folate-modified SSDP800. These nanoscale-enveloped polyplexes elicited an improved colloidal stability against salt ions and negatively charged heparin, efficient endosomal escaping, and bioreduction-triggered intracellular gene release. In vitro transfection against SKOV-3 cells illustrated that FA-e-polyplexes exerted higher transfection efficiency in the serum than e-polyplexes and 25 kDa BPEI-polyplexes. In vivo, FA-e-polyplexes yielded higher transgene expression level than e-polyplexes in an SKOV-3 tumor-bearing nude mouse model. In the tumor gene therapy with a small hairpin RNA silencing vascular endothelial growth factor, FA-e-polyplexes afforded higher tumor growth inhibition than polyplexes of folate-PEGylated PUBAP and 25 kDa linear polyethylenimine as positive controls. Importantly, such gene therapy had minor toxic effects on the health of the mouse. This work highlights a practical hierarchical assembly method to construct innovative enveloped polyurethane nanopolyplexes enabling robust ovarian cancer gene therapy.

STATEMENT OF SIGNIFICANCE

It is indispensable to rationally update binary cationic polyplexes into ternary polyplexes for vigorous tumor gene therapy. In this work, we have confirmed that a hierarchical assembly strategy, by using initial gene neutralization and subsequent gene condensation, is facile and effective to promote cationic polyurethane polyplexes into ternary folate-dextran-enveloped polyurethane polyplexes with a relatively high gene-loading capacity. The enveloped polyplex system enables more efficient gene transfection than the PEGylated polyplex counterpart in ovarian cancer in vitro and in vivo, thereby affording robust ovarian cancer gene therapy. The development of innovative enveloped polyplexes may be a new direction for a non-viral gene delivery system.

Dual Intratumoral Redox/Enzyme-Responsive NO-Releasing Nanomedicine for the Specific, High-Efficacy, and Low-Toxic Cancer Therapy

Chemotherapy suffers numbers of limitations including poor drug solubility, nonspecific biodistribution, and inevitable adverse effects on normal tissues. Tumor-targeted delivery and intratumoral stimuli-responsive release of drugs by nanomedicines are considered to be highly promising in solving these problems. Compared with traditional chemotherapeutic drugs, high concentration of nitric oxide (NO) exhibits unique anticancer effects. The development of tumor-targeting and intratumoral microenvironment-responsive NO-releasing nanomedicines is highly desired. Here a novel kind of organic-inorganic composite nanomedicine (QM-NPQ@PDHNs) is presented by encapsulating a glutathione S-transferases π (GSTπ)-responsive drug O² -(2,4-dinitro-5-{[2-(β-d-galactopyranosyl olean-12-en-28-oate-3-yl)-oxy-2-oxoethyl] piperazine-1-yl} phenyl) 1-(methylethanolamino)diazen-1-ium-1,2-dilate (NPQ) as NO donor and an aggregation-induced-emission (AIE) red fluorogen QM-2 into the cores of the hybrid nanomicelles (PEGylated disulfide-doped hybrid nanocarriers (PDHNs)) with glutathione (GSH)-responsive shells. The QM-NPQ@PDHN nanomedicine is able to respond to the intratumoral over-expressed GSH and GSTπ, resulting in the responsive biodegradation of the protective organosilica shell and NPQ release, and subsequent NO release within the tumor, respectively, and thus normal organs remain unaffected. This work demonstrates a paradigm of dual intratumoral redox/enzyme-responsive NO-release nanomedicine for tumor-specific and high-efficacy cancer therapy.

Modular Synthesis of Bioreducible Gene Vectors through Polyaddition of N,N'-Dimethylcystamine and Diglycidyl Ethers

Bioreducible, cationic linear poly(amino ether)s (PAEs) were designed as promising gene vectors. These polymers were synthesized by the reaction of a disulfide-functional monomer, N,N'-dimethylcystamine (DMC), and several different diglycidyl ethers. The resulting PAEs displayed a substantial buffer capacity (up to 64%) in the endosomal acidification region of pH 7.4⁻5.1. The PAEs condense plasmid DNA into 80⁻200 nm sized polyplexes, and have surface charges ranging from +20 to +40 mV. The polyplexes readily release DNA upon exposure to reducing conditions (2.5 mM DTT) due to the cleavage of the disulfide groups that is present in the main chain of the polymers, as was demonstrated by agarose gel electrophoresis. Upon exposing COS-7 cells to polyplexes that were prepared at polymer/DNA w/w ratios below 48, cell viabilities between 80⁻100% were observed, even under serum-free conditions. These polyplexes show comparable or higher transfection efficiencies (up to 38%) compared to 25 kDa branched polyethylenimine (PEI) polyplexes (12% under serum-free conditions). Moreover, the PAE-based polyplexes yield transfection efficiencies as high as 32% in serum-containing medium, which makes these polymers interesting for gene delivery applications.

A Universal GSH-Responsive Nanoplatform for the Delivery of DNA, mRNA, and Cas9/sgRNA Ribonucleoprotein

The long-sought promise of gene therapy for the treatment of human diseases remains unfulfilled, largely hindered by the lack of an efficient and safe delivery vehicle. In this study, we have developed a universal glutathione-responsive nanoplatform for the efficient delivery of negatively charged genetic biomacromolecules. The cationic block copolymer, poly(aspartic acid-(2-aminoethyl disulfide)-(4-imidazolecarboxylic acid))-poly(ethylene glycol), bearing imidazole residues and disulfide bonds, can form polyplexes with negatively charged DNA, mRNA, and Cas9/sgRNA ribonucleoprotein (RNP) through electrostatic interactions, which enable efficient cellular uptake, endosomal escape, and cytosol unpacking of the payloads. To facilitate the nuclear transport of DNA and RNP, the nuclear localization signal peptide was integrated into the DNA or RNP polyplexes. All three polyplex systems were fully characterized and optimized in vitro. Their relatively high transfection efficiency and low cytotoxicity, as well as convenient surface functionalization merit further investigation.

Fluorination Enhances Serum Stability of Bioreducible Poly(amido amine) Polyplexes and Enables Efficient Intravenous siRNA Delivery

The use of small interfering RNA (siRNA) in cancer treatment has been limited by the lack of effective systemic delivery methods. Although synthetic polycations have been widely explored in siRNA delivery, polycation/siRNA polyplexes often suffer from insufficient stability in vivo. Here, rationally designed siRNA delivery systems that meet the requirements for systemic siRNA delivery to distant tumors are reported. The hypothesis that modular design of delivery systems based on poly(amido amine)s that combine fluorination for systemic stability with bioreducibility for easy intracellular siRNA release, and PEGylation for improved safety and colloidal stability will overcome problems with contradicting siRNA delivery demands is tested. PEGylated, fluorinated, and bioreducible copolymers (PEG-PCD-F) with different degree of fluorination are thus synthesized. The fluorinated copolymers readily formed polyplexes with siRNA and achieved greatly improved gene silencing efficacy in multiple cell lines in vitro when compared with nonfluorinated controls. The results show fluorination-induced enhancement of stability, cellular uptake, and endosomal escape of the polyplexes, while exhibiting efficient siRNA release in reducing intracellular environment. PEG-PCD-F polyplexes with siRNA against Bcl2 inhibit breast tumor growth following systemic intravenous administration. The results provide strong evidence of successful combination of bioreducibility with fluorination and PEGylation to achieve systemic siRNA polyplex delivery.

Responsive crosslinked polymer nanogels for imaging and therapeutics delivery

Nanogels are water-soluble crosslinked polymer networks with tremendous potential in targeted imaging and controlled drug and gene delivery.

Recent development of synthetic nonviral systems for sustained gene delivery

Sustained gene delivery is of particular importance today because it circumvents the need for repeated therapeutic administration and provides spatial and temporal control of the release profile. Better understanding of the genetic basis of diseases and advances in gene therapy have propelled significant research on biocompatible gene carriers for therapeutic purposes. Varied biodegradable polymer-based architectures have been used to create new compositions with unique properties suitable for sustained gene delivery. This review presents the most recent advances in various polymeric systems: hydrogels, microspheres, nanospheres and scaffolds, having complex architectures to encapsulate and deliver functional genes. Through the recombination of different existing polymer systems, the multicomplex systems can be further endowed with new properties for better-targeted biomedical applications.

Bioreducible, hydrolytically degradable and targeting polymers for gene delivery

Recently, synthetic gene carriers have been intensively developed owing to their promising application in gene therapy and considered as a suitable alternative to viral vectors because of several benefits. But cationic polymers still face some problems like low transfection efficiency, cytotoxicity, and poor cell recognition and internalization. The emerging engineered and smart polymers can respond to some changes in the biological environment like pH change, ionic strength change and redox potential, which is beneficial for cellular uptake. Redox-sensitive disulfide based and hydrolytically degradable cationic polymers serve as gene carriers with excellent transfection efficiency and good biocompatibility owing to degradation in the cytoplasm. Additionally, biodegradable polymeric micelles with cell-targeting function are recently emerging gene carriers, especially for the transfection of endothelial cells. In this review, some strategies for gene carriers based on these bioreducible and hydrolytically degradable polymers will be illustrated.