Formulation and Delivery of siRNA by Oleic Acid and Stearic Acid Modified Polyethylenimine

Role of Hydrophobic Modification in Spermine-Based Poly(β-amino ester)s for siRNA Delivery and Their Spray-Dried Powders for Inhalation and Improved Storage

After RNAi was first discovered over 20 years ago, siRNA-based therapeutics are finally becoming reality. However, the delivery of siRNA has remained a challenge. In our previous research, we found that spermine-based poly(β-amino ester)s are very promising for siRNA delivery. However, the role of hydrophobic modification in siRNA delivery of spermine-based poly(β-amino ester)s is not fully understood yet. In the current work, we synthesized spermine-based poly(β-amino ester)s with different percentages of oleylamine side chains, named P(SpOABAE). The chemical structures of the polymers were characterized by 1H NMR. The polymers showed efficient siRNA encapsulation determined by SYBR Gold assays. The hydrodynamic diameters of the P(SpOABAE) polyplexes from charge ratio N/P 1 to 20 were 30-100 nm except for aggregation phenomena observed at N/P 3. Morphology of the polyplexes was visualized by atomic force microscopy, and cellular uptake was determined by flow cytometry in H1299 cells, where all the polyplexes showed significantly higher cellular uptake than hyperbranched polyethylenimine (25 kDa). The most hydrophobic P(SpOABAE) polyplexes were able to achieve more than 90% GFP knockdown in H1299/eGFP cells. The fact that gene silencing efficacy increased with hydrophobicity but cellular uptake was affected by both charge and hydrophobic interactions highlights the importance of endosomal escape. For pulmonary administration and improved storage stability, the polyplexes were spray-dried. Results confirmed the maintained siRNA activity after storage for 3 months at room temperature, indicating potential for dry powder inhalation.

Poly(β-aminoester) Physicochemical Properties Govern the Delivery of siRNA from Electrostatically Assembled Coatings

Localized short interfering RNA (siRNA) therapy has the potential to drive high-specificity molecular-level treatment of a variety of disease states. Unfortunately, effective siRNA therapy suffers from several barriers to its intracellular delivery. Thus, drug delivery systems that package and control the release of therapeutic siRNAs are necessary to overcome these obstacles to clinical translation. Layer-by-layer (LbL) electrostatic assembly of thin film coatings containing siRNA and protonatable, hydrolyzable poly(β-aminoester) (PBAE) polymers is one such drug delivery strategy. However, the impact of PBAE physicochemical properties on the transfection efficacy of siRNA released from LbL thin film coatings has not been systematically characterized. In this study, we investigate the siRNA transfection efficacy of four structurally similar PBAEs in vitro. We demonstrate that small changes in structure yield large changes in physicochemical properties, such as hydrophobicity, pKa, and amine chemical structure, driving differences in the interactions between PBAEs and siRNA in polyplexes and in LbL thin film coatings for wound dressings. In our polymer set, Poly3 forms the most stable interactions with siRNA (Keff,w/w = 0.298) to slow release kinetics and enhance transfection of reporter cells in both colloidal and thin film coating approaches. This is due to its unique physiochemical properties: high hydrophobicity (clog P = 7.86), effective pKa closest to endosomal pH (pKa = 6.21), and high cooperativity in buffering (nhill = 7.2). These properties bestow Poly3 with enhanced endosomal buffering and escape properties. Taken together, this work elucidates the connections between small changes in polymer structure, emergent properties, and polyelectrolyte theory to better understand PBAE transfection efficacy.

Pulmonary siRNA Delivery with Sophisticated Amphiphilic Poly(Spermine Acrylamides) for the Treatment of Lung Fibrosis

RNA interference (RNAi) is an efficient strategy to post-transcriptionally silence gene expression. While all siRNA drugs on the market target the liver, the lung offers a variety of currently undruggable targets, which can potentially be treated with RNA therapeutics. To achieve this goal, the synthesis of poly(spermine acrylamides) (P(SpAA) is reported herein. Polymers are prepared via polymerization of N-acryloxysuccinimide (NAS) and afterward this active ester is converted into spermine-based pendant groups. Copolymerizations with decylacrylamide are employed to increase the hydrophobicity of the polymers. After deprotection, polymers show excellent siRNA encapsulation to obtain perfectly sized polyplexes at very low polymer/RNA ratios. In vitro 2D and 3D cell culture, ex vivo and in vivo experiments reveal superior properties of amphiphilic spermine-copolymers with respect to delivery of siRNA to lung cells in comparison to commonly used lipid-based transfection agents. In line with the in vitro results, siRNA delivery to human lung explants confirm more efficient gene silencing of protease-activated receptor 2 (PAR2), a G protein-coupled receptor involved in fibrosis. This study reveals the importance of the balance between efficient polyplex formation, cellular uptake, gene knockdown, and toxicity for efficient siRNA delivery in vitro, in vivo, and in fibrotic human lung tissue ex vivo.

Hybrid Lipid Nanocapsules: A Robust Platform for mRNA Delivery

The success of the mRNA vaccine against COVID-19 has garnered significant interest in the development of mRNA therapeutics against other diseases, but there remains a strong need for a stable and versatile delivery platform for these therapeutics. In this study, we report on a family of robust hybrid lipid nanocapsules (hLNCs) for the delivery of mRNA. The hLNCs are composed of kolliphore HS15, labrafac lipophile WL1349, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), and a conjugate of oleic acid (OA) and polyethylenimines of varying size (PEI─0.8, 1.8, and 25 kDa). They are prepared by a solvent-free, temperature-phase inversion method, yielding an average size of ∼40 nm and a particle distribution index (PDI) < 0.2. We demonstrate that the PDI remains <0.2 over a wide pH range and in a wide range of medium. We further show that the PDI and the functionality of mRNA condensed on the particles are robust to drying in a sugar glass and subsequent rehydration. Finally, we demonstrate that mRNA-loaded hLNCs yield reasonable transfection in vitro and in vivo settings.

Recent Advances in Engineering Carriers for siRNA Delivery

RNA interference (RNAi) technology has been a promising treatment strategy for combating intractable diseases. However, the applications of RNAi in clinical are hampered by extracellular and intracellular barriers. To overcome these barriers, various siRNA delivery systems have been developed in the past two decades. The first approved RNAi therapeutic, Patisiran (ONPATTRO) using lipids as the carrier, for the treatment of amyloidosis is one of the most important milestones. This has greatly encouraged researchers to work on creating new functional siRNA carriers. In this review, the recent advances in siRNA carriers consisting of lipids, polymers, and polymer-modified inorganic particles for cancer therapy are summarized. Representative examples are presented to show the structural design of the carriers in order to overcome the delivery hurdles associated with RNAi therapies. Finally, the existing challenges and future perspective for developing RNAi as a clinical modality will be discussed and proposed. It is believed that the addressed contributions in this review will promote the development of siRNA delivery systems for future clinical applications.

Overcoming the blood-brain barrier? - prediction of blood-brain permeability of hydrophobically modified polyethylenimine polyplexes for siRNA delivery into the brain with in vitro and in vivo models

The blood-brain barrier (BBB) is a highly selective biological barrier that represents a major bottleneck in the treatment of all types of central nervous system (CNS) disorders. Small interfering RNA (siRNA) offers in principle a promising therapeutic approach, e.g., for brain tumors, by downregulating brain tumor-related genes and inhibiting tumor growth via RNA interference. In an effort to develop efficient siRNA nanocarriers for crossing the BBB, we utilized polyethyleneimine (PEI) polymers hydrophobically modified with either stearic-acid (SA) or dodecylacrylamide (DAA) subunits and evaluated their suitability for delivering siRNA across the BBB in in vitro and in vivo BBB models depending on their structure. Physicochemical characteristics of siRNA-polymer complexes (polyplexes (PXs)), e.g., particle size and surface charge, were measured by dynamic light scattering and laser Doppler anemometry, whereas siRNA condensation ability of polymers and polyplex stability was evaluated by spectrophotometric methods. The composition of the biomolecule corona that absorbs on polyplexes upon encountering physiological fluids was investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and by a liquid chromatography-tandem mass spectrometry (LC-MS-MS) method. Cellular internalization abilities of PXs into brain endothelial cells (hCMEC/D3) was confirmed, and a BBB permeation assay using a human induced pluripotent stem cell (hiPSC)-derived BBB model revealed similar abilities to cross the BBB for all formulations under physiological conditions. However, biodistribution studies of radiolabeled PXs in mice were inconsistent with in vitro results as the detected amount of radiolabeled siRNA in the brain delivered with PEI PXs was higher compared to PEI-SA PXs. Taken together, PEI PXs were shown to be a suitable nanocarrier to deliver small amounts of siRNA across the BBB into the brain but more sophisticated human BBB models that better represent physiological conditions and biodistribution are required to provide highly predictive in vitro data for human CNS drug development in the future.

Polymers in Engineering Extracellular Vesicle Mimetics: Current Status and Prospective

The maintenance of a high delivery efficiency by traditional nanomedicines during cancer treatment is a challenging task. As a natural mediator for short-distance intercellular communication, extracellular vesicles (EVs) have garnered significant attention owing to their low immunogenicity and high targeting ability. They can load a variety of major drugs, thus offering immense potential. In order to overcome the limitations of EVs and establish them as an ideal drug delivery system, polymer-engineered extracellular vesicle mimics (EVMs) have been developed and applied in cancer therapy. In this review, we discuss the current status of polymer-based extracellular vesicle mimics in drug delivery, and analyze their structural and functional properties based on the design of an ideal drug carrier. We anticipate that this review will facilitate a deeper understanding of the extracellular vesicular mimetic drug delivery system, and stimulate the progress and advancement of this field.

Self-Assembled Oleic Acid-Modified Polyallylamines for Improved siRNA Transfection Efficiency and Lower Cytotoxicity

Small interference RNA (siRNA) is a tool for gene modulation, which can silence any gene involved in genetic disorders. The potential of this therapeutic tool is hampered by RNA instability in the blood stream and difficulties to reach the cytosol. Polyamine-based nanoparticles play an important role in gene delivery. Polyallylamine hydrochloride (PAH) is a polycation displaying primary amines that can be easily chemically modified to match the balance between cell viability and siRNA transfection. In this work, PAH has been covalently functionalized with oleic acid at different molar ratios by carbodiimide chemistry. The substituted polymers form polyplexes that keep positive surface charge and fully encapsulate siRNA. Oleic acid substitution improves cell viability in the pulmonary cell line A549. Moreover, 6 and 14% of oleic acid substitution show an improvement in siRNA transfection efficiency. CD47 is a ubiquitous protein which acts as "don't eat me signal." SIRPα protein of macrophages recognizes CD47, leading to tumor cell phagocytosis by macrophages. By knocking down CD47 with siRNA, cancer cells become vulnerable to be eliminated by the immune system. PAH-oleic acid substitutes show high efficacy in silencing the CD47 protein, making them a potential candidate for immunotherapy.

Bioengineered polyester nanoparticles for the synergistic treatment of androgenic alopecia via the suppression of 5α-reductase and knockdown of androgen receptor

Androgenic alopecia (AGA) is a common disease that negatively affects patients’ physical and mental health. AGA can be treated with drugs that improve the perifollicular microenvironment, such as 5α-reductase inhibitors (e.g., dutasteride [DUT]), androgen receptor blockers, and minoxidil. However, the efficacy of these treatments is limited. Therefore, this study aimed to show that nanoparticles are effective as stable carriers with high curative benefits and little adverse effects. The in vitro study showed that PLGA-DUT/siAR@DPCM NPs could deliver both DUT and siAR to dermal papilla cells. They could successfully suppress 5α-reductase and knock down androgen receptor, respectively, and thereby promote cell proliferation. In the in vivo study, PLGA-DUT/siAR@DPCM NPs showed a significant therapeutic effect in an AGA mouse model. They successfully penetrated the stratum corneum and showed a clear targeting effect on hair follicles and surrounding tissues. PLGA-DUT/siAR@DPCM NPs could enable the targeted delivery of DUT and siAR through percutaneous penetration, enhancing phagocytosis and decreasing adverse effects. Thus, they have great potential in the clinical treatment of AGA.

Oleyl Conjugated Histidine-Arginine Cell-Penetrating Peptides as Promising Agents for siRNA Delivery

Recent approvals of siRNA-based products motivated the scientific community to explore siRNA as a treatment option for several intractable ailments, especially cancer. The success of approved siRNA therapy requires a suitable and safer drug delivery agent. Herein, we report a series of oleyl conjugated histidine–arginine peptides as a promising nonviral siRNA delivery tool. The conjugated peptides were found to bind with the siRNA at N/P ratio ≥ 2 and demonstrated complete protection for the siRNA from early enzymatic degradation at N/P ratio ≥ 20. Oleyl-conjugated peptide -siRNA complexes were found to be noncytotoxic in breast cancer cells (MCF-7 and MDA-MB-231) and normal breast epithelial cells (MCF 10A) at N/P ratio of ~40. The oleyl-R₃-(HR)₄ and oleyl-R₄-(HR)₄ showed ~80-fold increased cellular uptake in MDA-MB-231 cells at N/P 40. Moreover, the conjugated peptides-siRNA complexes form nanocomplexes (~115 nm in size) and have an appropriate surface charge to interact with the cell membrane and cause cellular internalization. Furthermore, this study provides a proof-of-concept that oleyl-R₅-(HR)₄ can efficiently silence STAT-3 gene (~80% inhibition) in MDA-MB-231 cells with similar effectiveness to Lipofectamine. Further exploration of this approach holds a great promise in discovering a successful in vivo siRNA delivery agent with a favorable pharmacokinetic profile.

Lipids and Lipid Derivatives for RNA Delivery

RNA-based therapeutics have shown great promise in treating a broad spectrum of diseases through various mechanisms including knockdown of pathological genes, expression of therapeutic proteins, and programmed gene editing. Due to the inherent instability and negative-charges of RNA molecules, RNA-based therapeutics can make the most use of delivery systems to overcome biological barriers and to release the RNA payload into the cytosol. Among different types of delivery systems, lipid-based RNA delivery systems, particularly lipid nanoparticles (LNPs), have been extensively studied due to their unique properties, such as simple chemical synthesis of lipid components, scalable manufacturing processes of LNPs, and wide packaging capability. LNPs represent the most widely used delivery systems for RNA-based therapeutics, as evidenced by the clinical approvals of three LNP-RNA formulations, patisiran, BNT162b2, and mRNA-1273. This review covers recent advances of lipids, lipid derivatives, and lipid-derived macromolecules used in RNA delivery over the past several decades. We focus mainly on their chemical structures, synthetic routes, characterization, formulation methods, and structure-activity relationships. We also briefly describe the current status of representative preclinical studies and clinical trials and highlight future opportunities and challenges.

Amphiphilic QP(DMAEMA-co-LMA)-b-POEGMA Random-Block Terpolymers as Nanocarriers for Insulin

We report on the utilization of the amphiphilic poly[quaternized (2-(N,N-dimethylamino) ethyl methacrylate)]-co-(lauryl methacrylate))-b-poly[(oligo ethylene glycol) methyl ether methacrylate] QP(DMAEMA-co-LMA)-b-POEGMA cationic diblock terpolymer aggregates as nanocarriers for insulin delivery applications. QP(DMAEMA-co-LMA)-b-POEGMA random diblock terpolymer is derived from the chemical modification of the precursor amino diblock copolymer via quaternization, producing permanent positive charges on the macromolecular chain. The QP(DMAEMA-co-LMA)-b-POEGMA diblock terpolymer as well as its amino precursor investigated self-assemble in aqueous media, forming aggregates. In vitro cytotoxicity and in vivo biocompatibility studies on QP(DMAEMA-co-LMA)-b-POEGMA and its amino precursor aggregates, showed good cytocompatibility and biocompatibility. QP(DMAEMA-co-LMA)-b-POEGMA aggregates were chosen to be complexed with insulin due to their self-assembly features and the permanent positive charge in each amino group. QP(DMAEMA-co-LMA)-b-POEGMA aggregates were complexed with insulin through electrostatic interactions. Light scattering techniques were used in order to study the ability of the polymer aggregates to complex with insulin, to determine critical physicochemical parameters such as size, mass, and surface charge of the stable complexes and study the effect of salt addition on their properties. The results showed that in both cases, the complexation process was successful and as the insulin concentration increases, nanosized complexes of different physicochemical characteristics (mass, size, surface charge) and spherical morphology are formed. UV-Vis and fluorescence spectroscopy studies showed that no conformational changes of insulin occurred after the complexation.

A pH-responsive Pickering Nanoemulsion for specified spatial delivery of Immune Checkpoint Inhibitor and Chemotherapy agent to Tumors

Rationale: Immune checkpoint (ICP) blockade therapy combined with chemotherapy is a promising treatment strategy for tumors. Chemotherapeutic agents usually function inside the tumor cells, while ICP inhibitors are efficacious out of the tumor cells. It is desirable to effectively co-deliver an ICP inhibitor and a chemotherapy agent to different sites of a tumor. We have designed an effective drug delivery system to accomplish both objectives. Methods: We designed a Pickering nanoemulsion (PNE) using multi-sensitive nanogels with pH-responsive, hydrophilicity-hydrophobicity switch, and redox-responding properties as an oil/water interfacial stabilizer. The D/HY@PNE was employed for specified spatial delivery of the chemotherapy agent doxorubicin (DOX) and ICP inhibitor HY19991 (HY). We systematically investigated the pH-responsive disassembly of PNE, the release of DOX and HY from D/HY@PNE in the tumor microenvironment, enhanced tumor penetration of DOX, immunogenic cell death (ICD), antitumor efficacy, and the immune response induced by D/HY@PNE in vitro and in vivo. Results: D/HY@PNE disassembled to release the ICP inhibitor HY and DOX-loaded nanogels due to the hydrophilicity-hydrophobicity reversal of nanogels in the acidic tumor microenvironment. Quantitative analysis indicates that D/HY@PNE presents enhanced tumor penetration behavior and effectively induces ICD. The strong immune response induced by D/HY@PNE was due to the efficient synergetic combination of chemotherapy and immunotherapy and resulted in enhanced antitumor efficacy in 4T1 tumor-bearing mice. Conclusion: This novel strategy highlights the promising potential of a universal platform to co-deliver different therapeutic or diagnostic reagents with spatial regulation to improve the anti-tumor effect.

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

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

Physicochemical Evaluation of Insulin Complexes with QPDMAEMA-b-PLMA-b-POEGMA Cationic Amphiphlic Triblock Terpolymer Micelles

Herein, poly[quaternized 2-(dimethylamino)ethyl methacrylate-b-lauryl methacrylate-b-(oligo ethylene glycol)methacrylate] (QPDMAEMA-b-PLMA-b-POEGMA) cationic amphiphilic triblock terpolymers were used as vehicles for the complexation/encapsulation of insulin (INS). The terpolymers self-assemble in spherical micelles with PLMA cores and mixed QPDMAEMA/POEGMA coronas in aqueous solutions. The cationic micelles were complexed via electrostatic interactions with INS, which contains anionic charges at pH 7. The solutions were colloidally stable in all INS ratios used. Light-scattering techniques were used for investigation of the complexation ability and the size and surface charge of the terpolymer/INS complexes. The results showed that the size of the complexes increases as INS ratio increases, while at the same time the surface charge remains positive, indicating the formation of clusters of micelles/INS complexes in the solution. Fluorescence spectroscopy measurements revealed that the conformation of the protein is not affected after the complexation with the terpolymer micellar aggregates. It was observed that as the solution ionic strength increases, the size of the QPDMAEMA-b-PLMA-b-POEGMA/INS complexes initially decreases and then remains practically constant at higher ionic strength, indicating further aggregation of the complexes. atomic force microscopy (AFM) measurements showed the existence of both clusters and isolated nanoparticulate terpolymer/protein complexes.

Enabling Combinatorial siRNA Delivery against Apoptosis-Related Proteins with Linoleic Acid and α-Linoleic Acid Substituted Low Molecular Weight Polyethylenimines

PURPOSE

Short interfering RNA (siRNA) therapy promises a new era in treatment of breast cancers but effective delivery systems are needed for clinical use. Since silencing complementary targets may offer improved efficacy, this study was undertaken to identify non-viral carriers for combinatorial siRNA delivery for more effective therapy.

METHODS

A library of lipid-substituted polymers from low molecular weight polyethyleneimine (PEI), linoleic acid (LA) and α-linoleic acid (αLA) with amide or thioester linkages was prepared and investigated for delivering Mcl-1, survivin and STAT5A siRNAs in breast cancer cells.

RESULTS

The effective polymers formed 80-190 nm particles with similar zeta-potentials, but the serum stability was greater for complexes formed with amide-linked lipid conjugates. The LA and αLA substitutions, with the low molecular weight PEI (1.2 kDa and 2.0 kDa) were able to deliver siRNA effectively to cells and retarded the growth of breast cancer cells. The amide-linked lipid substituents showed higher cellular delivery of siRNA as compared to thioester linkages. Upon combinational delivery of siRNAs, growth of MCF-7 cells was inhibited to a greater extent with 2.0PEI-LA9 mediated delivery of Mcl-1 combined survivin siRNAs as compared to individual siRNAs. The qRT-PCR analysis confirmed the decrease in mRNA levels of target genes with specific siRNAs and 2.0PEI-LA9 was the most effective polymer for delivering siRNAs (either single or in combination).

CONCLUSIONS

This study yielded effective siRNA carriers for combinational delivery of siRNAs. Careful choice of siRNA combinations will be critical since targeting individual genes might alter the expression of other critical mediators.

Long Non-coding RNA DANCR as an Emerging Therapeutic Target in Human Cancers

Long noncoding RNAs (lncRNAs) are emerging as important regulators of numerous biological processes, especially in cancer development. Aberrantly expressed and specifically located in tumor cells, they exert distinct functions in different cancers via regulating multiple downstream targets such as chromatins, RNAs, and proteins. Differentiation antagonizing non-protein coding RNA (DANCR) is a cytoplasmic lncRNA that generally works as a tumor promoter. Mechanically, DANCR promotes the functions of vital components in the oncogene network by sponging their corresponding microRNAs or by interacting with various regulating proteins. DANCR's distinct expression in tumor cells and collective involvement in pro-tumor pathways make it a promising therapeutic target for broad cancer treatment. Herein, we summarize the functions and molecular mechanism of DANCR in human cancers. Furthermore, we introduce the use of CRISPR/Cas9, antisense oligonucleotides and small interfering RNAs as well as viral, lipid, or exosomal vectors for onco-lncRNA targeted treatment. Conclusively, DANCR is a considerable promoter of cancers with a bright prospect in targeted therapy.

Effect of Glyceryl Monocaprylate-Modified Chitosan on the Intranasal Absorption of Insulin in Rats

Nasal administration of insulin showed the attractive potential to improve the compliance of diabetic patients and alleviate mild cognitive impairment of Alzheimer's patients. However, the nasal absorption of insulin was not ideal, limiting its therapeutic effect in clinic. This study was to explore the potential of glyceryl monocaprylate-modified chitosan (CS-GMC) on the intranasal absorption of insulin via in vivo pharmacodynamic experiment in conscious rats. It was demonstrated that the absorption-enhancing effect of CS-GMC depended on the existing state of insulin in the formulation, substitution degree of GMC on chitosan and concentration of CS-GMC. Better insulin absorption was achieved when insulin existed in molecular form compared with that in polyelectrolyte complexes. CS-GMC with substitution degree 12% (CS-GMC 12%) was a preferred absorption enhancer, and its absorption enhancing effect increased linearly with the increment of its concentration in the range investigated. Compared with chitosan of the same concentration, CS-GMC12% showed remarkably enhanced and prolonged therapeutic effect up to at least 5 h under the concentration of 0.6% (w/v). CS-GMC12% showed almost no ciliotoxicity to the nasal cilia up to concentration 1.0% (w/v). In conclusion, CS-GMC was a promising absorption enhancer to improve the intranasal absorption of insulin.

The Impact of Nylon-3 Copolymer Composition on the Efficiency of siRNA Delivery to Glioblastoma Cells

Glioblastoma multiforme is a devastating disease that has attracted enormous attention due to poor prognosis and high recurrence. Small interfering RNA (siRNA) in principle offers a promising therapeutic approach by the downregulation of disease-related genes via RNA interference. For efficient siRNA delivery to target sites, cationic polymers are often used in preclinical studies for the protection of siRNA and complex formation based on electrostatic interactions. In an effort to develop biocompatible and efficient nanocarriers with a translational outlook for optimal gene silencing at reduced toxicity, we synthesized two sets of nylon-3 copolymers with variable cationic content (DM or NM monomer) and hydrophobic subunits (CP monomer) and evaluated their suitability for in vitro siRNA delivery into glioblastoma cells. DM_0.4/CP_0.6 and NM_0.4/CP_0.6 polymers with similar subunit ratios were synthesized to compare the effect of different cationic subunits. Additionally, we utilized NM_0.2/CP_0.8 polymers to evaluate the impact of the different hydrophobic content in the polymer chain. The siRNA condensation ability and polymer–siRNA complex stability was evaluated by unmodified and modified SYBR gold assays, respectively. Further physicochemical characteristics, e.g., particle size and surface charge, were evaluated by dynamic light scattering and laser Doppler anemometry, whereas a relatively new method for polyplex size distribution analysis—tunable resistive pulse sensing—was additionally developed and compared to DLS measurements. Transfection efficiencies, the route of cell internalization, and protein knockdown abilities in glioblastoma cells were investigated by flow cytometry. Furthermore, cellular tolerability was evaluated by MTT and LDH assays. All the polymers efficiently condensed siRNA at N/P ratios of three, whereas polymers with NM cationic subunits demonstrated smaller particle size and lower polyplex stability. Furthermore, NM_0.2/CP_0.8 polyplexes with the highest hydrophobic content displayed significantly higher cellular internalization in comparison to more cationic formulations and successful knockdown capabilities. Detailed investigations of the cellular uptake route demonstrated that these polyplexes mainly follow clathrin-mediated endocytotic uptake mechanisms, implying high interaction capacity with cellular membranes. Taken together with conducive toxicity profiles, highly hydrophobic nylon-3 polymers provide an appropriate siRNA delivery agent for the potential treatment of glioblastoma.

Signal Transducer and Activator of Transcription (STATs) Proteins in Cancer and Inflammation: Functions and Therapeutic Implication

Signal Transducer and Activator of Transcription (STAT) pathway is connected upstream with Janus kinases (JAK) family protein and capable of integrating inputs from different signaling pathways. Each family member plays unique functions in signal transduction and crucial in mediating cellular responses to different kind of cytokines. STAT family members notably STAT3 and STAT5 have been involved in cancer progression whereas STAT1 plays opposite role by suppressing tumor growth. Persistent STAT3/5 activation is known to promote chronic inflammation, which increases susceptibility of healthy cells to carcinogenesis. Here, we review the role of STATs in cancers and inflammation while discussing current therapeutic implications in different cancers and test models, especially the delivery of STAT3/5 targeting siRNA using nanoparticulate delivery system.

Enhancing the In Vitro and In Vivo Stabilities of Polymeric Nucleic Acid Delivery Nanosystems

Gene therapy holds great promise for various medical and biomedical applications. Nonviral gene delivery systems formed by cationic polymer and nucleic acids (e.g., polyplexes) have been extensively investigated for targeted gene therapy; however, their in vitro and in vivo stability is affected by both their intrinsic properties such as chemical compositions (e.g., polymer molecular weight and structure, and N/P ratio) and a number of environmental factors (e.g., shear stress during circulation in the bloodstream, interaction with the serum proteins, and physiological ionic strength). In this review, we surveyed the effects of a number of important intrinsic and environmental factors on the stability of polymeric gene delivery systems, and discussed various strategies to enhance the stability of polymeric gene delivery systems, thereby enabling efficient gene delivery into target cells. Future opportunities and challenges of polymeric nucleic acid delivery nanosystems were also briefly discussed.

Efficient siRNA delivery and gene silencing using a lipopolypeptide hybrid vector mediated by a caveolae-mediated and temperature-dependent endocytic pathway

Background

We developed a non-viral vector, a combination of HIV-1 Tat peptide modified with histidine and cysteine (mTat) and polyethylenimine, jetPEI (PEI), displaying the high efficiency of plasmid DNA transfection with little toxicity. Since the highest efficiency of INTERFERin (INT), a cationic amphiphilic lipid-based reagent, for small interfering RNA (siRNA) transfection among six commercial reagents was shown, we hypothesized that combining mTat/PEI with INT would improve transfection efficiency of siRNA delivery. To elucidate the efficacy of the hybrid vector for siRNA silencing, β-actin expression was measured after siRNA β-actin was transfected with mTat/PEI/INT or other vectors in HSC-3 human oral squamous carcinoma cells.

Results

mTat/PEI/INT/siRNA produced significant improvement in transfection efficiency with little cytotoxicity compared to other vectors and achieved ≈ 100% knockdown of β-actin expression compared to non-treated cells. The electric charge of mTat/PEI/INT/siRNA was significantly higher than INT/siRNA. The particle size of mTat/PEI/INT/siRNA was significantly smaller than INT/siRNA. Filipin III and β-cyclodextrin, an inhibitor of caveolae-mediated endocytosis, significantly inhibited mTat/PEI/INT/siRNA transfection, while chlorpromazine, an inhibitor of clathrin-mediated endocytosis, did not inhibit mTat/PEI/INT/siRNA transfection. Furthermore, the transfection efficiency of mTat/PEI/INT at 4 °C was significantly lower than 37 °C.

Conclusions

These findings demonstrated the feasibility of using mTat/PEI/INT as a potentially attractive non-viral vector for siRNA delivery.

Anisamido-Polyethylenimines as Efficient Nonviral Vectors for the Transport of Plasmid DNA to Sigma Receptor-Bearing Cells In Vitro

Site-specific delivery of therapeutics promises better outcomes in the treatment of diseases. A small ligand, anisamide, has been shown to specifically bind sigma receptors highly overexpressed on prostate cancer cells, one of the leading cancers causing deaths worldwide. Here, anisamide-tethered polyethylenimine polymers (AP) have been synthesized and evaluated for their capability to transport nucleic acid across the cell membrane. A series of modified polymers (AP-1 to AP-4) was synthesized, physicochemically characterized, and evaluated for their transfection efficiency and cytotoxicity. Postconjugation, there was a marginal decrease in the buffering capacity; however, it did not diminish the ultimate objective of the study rather improved the transfection efficiency and decreased the cytotoxicity making these polymers as efficient and safe vectors for nucleic acid delivery. All the modified polymers displayed enhanced capability to deliver DNA inside the cells. Among the series, the modified polymer, AP-4 (10% attempted substitution), exhibited the highest transfection in HEK293 cells having abundant sigma receptors with minimal cytotoxicity. The projected polymer also showed complete protection of bound DNA against enzymatic degradation. Altogether, the results demonstrated targeting ability of the proposed polymers to deliver nucleic acid to sigma receptor-bearing cells in vitro.

Polycations for Gene Delivery: Dilemmas and Solutions

Gene therapy has been a promising strategy for treating numerous gene-associated human diseases by altering specific gene expressions in pathological cells. Application of nonviral gene delivery is hindered by various dilemmas encountered in systemic gene therapy. Therefore, solutions must be established to address the unique requirements of gene-based treatment of diseases. This review will particularly highlight the dilemmas in polycation-based gene therapy by systemic treatment. Several promising strategies, which are expected to overcome these challenges, will be briefly reviewed. This review will also explore the development of polycation-based gene delivery systems for clinical applications.

Saponins enhance exon skipping of 2'-O-methyl phosphorothioate oligonucleotide in vitro and in vivo

BACKGROUND

Antisense oligonucleotide (ASO)-mediated exon skipping has been feasible and promising approach for treating Duchenne muscular dystrophy (DMD) in preclinical and clinical trials, but its therapeutic applications remain challenges due to inefficient delivery.

METHODS

We investigated a few Saponins for their potential to improve delivery performance of an antisense 2'-Omethyl phosphorothioate RNA (2'-OMePS) in muscle cells and in dystrophic mdx mice. This study was carried out by evaluating these Saponins' toxicity, cellular uptake, transduction efficiency in vitro, and local delivery in vivo for 2'-OMePS, as well as affinity study between Saponin and 2'-OMePS.

RESULTS

The results showed that these Saponins, especially Digitonin and Tomatine, enhance the delivery of 2'-OMePS with comparable efficiency to Lipofectamine 2k (LF-2k) -mediated delivery in vitro. Significant performance was further observed in mdx mice, up to 10-fold with the Digitonin as compared to 2'-OMePS alone. Cytotoxicity of the Digitonin and Glycyrrhizin was much lower than LF-2k in vitro and not clearly detected in vivo under the tested concentrations.

CONCLUSION

This study potentiates Saponins as delivery vehicle for 2'-OMePS in vivo for treating DMD or other diseases.

Micelle-like nanoparticles as siRNA and miRNA carriers for cancer therapy

Gene therapy has emerged as an alternative in the treatment of cancer, particularly in cases of resistance to chemo and radiotherapy. Different approaches to deliver genetic material to tumor tissues have been proposed, including the use of small non-coding RNAs due to their multiple mechanisms of action. However, such promise has shown limits in in vivo application related to RNA's biological instability and stimulation of immunity, urging the development of systems able to overcome those barriers. In this review, we discuss the use of RNA interference in cancer therapy with special attention to the role of siRNA and miRNA and to the challenges of their delivery in vivo. We introduce a promising class of drug delivery system known as micelle-like nanoparticles and explore their synthesis and advantages for gene therapy as well as the recent findings in in vitro, in vivo and clinical studies.

Functional DNA Delivery Enabled by Lipid-Modified Charge-Altering Releasable Transporters (CARTs)

Safe and effective DNA delivery systems are required to enable or enhance clinical strategies and research involving gene therapy and DNA vaccinations. To address this delivery problem, a series of charge-altering releasable transporters (CARTs) with varied lipid content were prepared and evaluated for plasmid DNA (pDNA) delivery into cultured cells. These lipid-modified CART co-oligomers were synthesized in only two steps via sequential organocatalytic ring-opening polymerization of lipid-containing cyclic carbonate monomers and morpholinone monomers. Lipid variations of the CARTs substantially impacted the delivery efficiency of pDNA, with oleyl- and linoleyl-based CARTs showing enhanced performance relative to the commercial transfection agent Lipofectamine 2000 (L2000). The best-performing oleyl CART was carried forward to study stable luciferase transfection with a Sleeping Beauty ( SB) transposon system. The oleyl CART outperformed the L2000 positive control with respect to stable transfection efficiency. CART-pDNA complexes represent a new DNA delivery system for research and clinical applications.

STAT3-siRNA induced B16.F10 melanoma cell death: more association with VEGF downregulation than p-STAT3 knockdown

STAT3 knockdown by small interfering RNA (siRNA) has been described to inhibit carcinogenic growth in various types of tumors. Earlier we have reported delivery of siRNA by oleic acid- and stearic acid-modified-polyethylenimine and enhancement of silencing of STAT3 by small interfering RNA (siRNA) in B16.F10 melanoma cell lines and consequent tumor suppression. Present investigation mainly focused on the downstream events involved in B16.F10 melanoma cell death and consequent tumor suppression following knockdown of p-STAT3 by siRNA. Lipid-substituted polyethylenimine (PEI)-p-STAT3-siRNA were prepared and characterized by measuring its N/P ratio, zeta potential, size, association and dissociation with siRNA. B16.F10 melanoma cells were treated with six different concentrations of PEI-p-STAT3-siRNA (200, 100, 50, 25, 12.5 and 6.25 nM). Downregulation of p-STAT3 and VEGF were studied using western blot and ELISA in association with the melanoma cell death. PEI-p-STAT3-siRNA hydrodynamic diameter ranged from 110 to 270 nm. PEI assisted p-STAT3-siRNA delivery exhibited increased uptake by B16.F10, when analyzed by fluorescent and confocal microscopy along with flowcytometry. It induced concentration-dependent knockdown of the p-STAT3 that also downregulated VEGF expression in similar fashion and induced B16.F10 cell death. Higher concentrations of p-STAT3-siRNA appear to significantly downregulate the VEGF expression via p-STAT3 knockdown. Decreasing survival of B16.F10 cells with the increasing concentration of p-STAT3-siRNA significantly correlated with VEGF downregulation, not with p-STAT3 expression. Data suggest that VEGF downregulation following knockdown of p-STAT3 may be a key event in survival reduction in B16.F10 melanoma cells and.

Effect of PEGylation on assembly morphology and cellular uptake of poly ethyleneimine-cholesterol conjugates for delivery of sorafenib tosylate in hepatocellular carcinoma

Introduction: Sorafenib (SFB) is an FDA-approved chemotherapeutic agent with a high partition coefficient (log P = 4.34) for monotherapy of hepatocellular carcinoma (HCC). The oral bioavailability is low and variable, so it was aimed to study the application of the polymeric nanoassembly of cholesterol conjugates of branched polyethyleneimine (PEI) for micellar solubilization of SFB and to investigate the impact of the polymer PEGylation on the physicochemical and cellular characteristics of the lipopolymeric dispersions. Methods: Successful synthesis of cholesterol-PEI lipopolymers, either native or PEGylated, was confirmed by FTIR, ¹H-NMR, pyrene assay methods. The nanoassemblies were also characterized in terms of morphology, particle size distribution and zeta-potential by TEM and dynamic light scattering (DLS). The SFB loading was optimized using general factorial design. Finally, the effect of particle characteristics on cellular uptake and specific cytotoxicity was investigated by flow cytometry and MTT assay in HepG2 cells. Results: Transmission electron microscopy (TEM) showed that PEGylation of the lipopolymers reduces the size and changes the morphology of the nanoassembly from rod-like to spherical shape. However, PEGylation of the lipopolymer increased critical micelle concentration (CMC) and reduced the drug loading. Moreover, the particle shape changes from large rods to small spheres promoted the cellular uptake and SFB-related cytotoxicity. Conclusion: The combinatory effects of enhanced cellular uptake and reduced general cytotoxicity can present PEGylated PEI-cholesterol conjugates as a potential carrier for delivery of poorly soluble chemotherapeutic agents such as SFB in HCC that certainly requires further investigations in vitro and in vivo.

Applications and perspectives of nanomaterials in novel vaccine development

Vaccines show great potential for both prophylactic and therapeutic use in infections, cancer, and other diseases. With the rapid development of bio-technologies and materials sciences, nanomaterials are playing essential roles in novel vaccine formulations and can boost antigen effectiveness by operating as delivery systems to enhance antigen processing and/or as immune-potentiating adjuvants to induce or potentiate immune responses. The effect of nanoparticles in vaccinology showed enhanced antigen stability and immunogenicity as well as targeted delivery and slow release. However, obstacles remain due to the lack of fundamental knowledge on the detailed molecular working mechanism and in vivo bio-effects of nanoparticles. This review provides a broad overview of the current improvements in nanoparticles in vaccinology. Modern nanoparticle vaccines are classified by the nanoparticles' action based on either delivery system or immune potentiator approaches. The mechanisms of interaction of nanoparticles with the antigens and the immune system are discussed. Nanoparticle vaccines approved for use are also listed. A fundamental understanding of the in vivo bio-distribution and the fate of nanoparticles will accelerate the rational design of new nanoparticles comprising vaccines in the future.

'Borono-lectin' based engineering as a versatile platform for biomedical applications

Boronic acids are well known for their ability to reversibly interact with the diol groups, a common motif of biomolecules including sugars and ribose. Due to their ability to interact with carbohydrates, they can be regarded as synthetic mimics of lectins, termed 'borono-lectins'. The borono-lectins can be tailored to elicit a broad profile of binding strength and specificity. This special property has been translated into many creative biomedical applications in a way interactive with biology. This review provides a brief overview of recent efforts of polymeric materials-based engineering taking advantage of such virtue of 'borono-lectins' chemistry, related to the field of biomaterials and drug delivery applications.

Radiation-enhanced delivery of plasmid DNA to tumors utilizing a novel PEI polyplex

The excitement surrounding the potential of gene therapy has been tempered due to the challenges that have thus far limited its successful implementation in the clinic such as issues regarding stability, transfection efficiency, and toxicity. In this study, low molecular weight linear polyethyleneimine (2.5 kDa) was modified by conjugation to a lipid, lithocholic acid, and complexed with a natural polysaccharide, dermatan sulfate (DS), to mask extra cationic charges of the modified polymer. In vitro examination revealed that these modifications improved complex stability with plasmid DNA (pDNA) and transfection efficiency. This novel ternary polyplex (pDNA/3E/DS) was used to investigate if tumor-targeted radiotherapy led to enhanced accumulation and retention of gene therapy vectors in vivo in tumor-bearing mice. Imaging of biodistribution revealed that tumor irradiation led to increased accumulation and retention as well as decreased off-target tissue buildup of pDNA in not only pDNA/3E/DS, but also in associated PEI-based polyplexes and commercial DNA delivery vehicles. The DS-containing complexes developed in this study displayed the greatest increase in tumor-specific pDNA delivery. These findings demonstrate a step forward in nucleic acid vehicle design as well as a promising approach to overall cancer gene therapy through utilization of radiotherapy as a tool for enhanced delivery.

Free energy landscape of siRNA-polycation complexation: Elucidating the effect of molecular geometry, polymer flexibility, and charge neutralization

The success of medical threatments with DNA and silencing interference RNA is strongly related to the design of efficient delivery technologies. Cationic polymers represent an attractive strategy to serve as nucleic-acid carriers with the envisioned advantages of efficient complexation, low cost, ease of production, well-defined size, and low polydispersity index. However, the balance between efficacy and toxicity (safety) of these polymers is a challenge and in need of improvement. With the aim of designing more effective polycationic-based gene carriers, many parameters such as carrier morphology, size, molecular weight, surface chemistry, and flexibility/rigidity ratio need to be taken into consideration. In the present work, the binding mechanism of three cationic polymers (polyarginine, polylysine and polyethyleneimine) to a model siRNA target is computationally investigated at the atomistic level. In order to better understand the polycationic carrier-siRNA interactions, replica exchange molecular dynamic simulations were carried out to provide an exhaustive exploration of all the possible binding sites, taking fully into account the siRNA flexibility together with the presence of explicit solvent and ions. Moreover, well-tempered metadynamics simulations were employed to elucidate how molecular geometry, polycation flexibility, and charge neutralization affect the siRNA-polycations free energy landscape in term of low-energy binding modes and unbinding free energy barriers. Significant differences among polymer binding modes have been detected, revealing the advantageous binding properties of polyarginine and polylysine compared to polyethyleneimine.

Disassembly of micelle-like polyethylenimine nanocomplexes for siRNA delivery: High transfection efficiency and reduced toxicity achieved by simple reducible lipid modification

Amphiphilic compounds consisting of polycations and lipid segments are well established as building blocks for the construction of siRNA carriers. They are capable of forming nanoparticles with high-affinity positive charges for siRNA in aqueous media due to their intra- and/or intermolecular hydrophobic and electrostatic interactions. Unfortunately, safety and efficiency of lipid-modified polycations as the two great challenges to the clinical application need to be improved. Beyond that, the role of the hydrophobic segment in the process of siRNA delivery is elusive. Herein, in this study, branched polyethylenimine with a molecular weight of 600 (bPEI₆₀₀) was grafted with reducible lipids via Michael addition reaction between amines and alkyl acrylates. Reducible amphiphilic polyethylenimines (PEIs) were able to condense siRNA into nanoparticles and disassemble under the reductive environment. Investigations with these materials in vitro revealed that the polymers with higher grafting degree provided high luciferase knockdown efficacies even at lower N/P ratios and the polymers with longer lipid chain displayed greater cellular uptake rate. Interestingly, the polymers with lower grafting degree had efficient cellular uptake than native bPEI₆₀₀, although their in luciferase knockdown assays were most likely inefficient. The inconsistency between the cellular uptake profile and silencing efficacy proved that the intracellular trafficking of siRNA was a bottleneck for siRNA delivery with some polymers prepared in this study. As expected, reducible lipid-modified PEIs were equally efficient and much less toxic compared to non-reducible counterparts and might provide broader therapeutic windows. These findings showed the feasibility of reducible lipid-modified PEIs as carriers for therapeutic siRNA.

Characterization of complexes made of polylysine-polyleucine-polylysine and pDNA

Polylysine shows unique physical and biological abilities in its application. In this study, different kinds of tri-block co-polypeptides are used as gene delivery vectors with hydrophobic polyleucine (L) in the middle and polylysine (K) on both sides. We explored their physical properties in aqueous solution as well as their biological effects toward gene transfection efficiency. After reaching critical micelle concentration, it is found that these tri-block polypeptides could form vesicles, and the size of each sample is independent of concentration. The self-assembly of each kind of tri-block co-polypeptide could obtain higher molecular weight vectors for gene delivery. After measuring the transfection efficiency and cell viability, these samples showed a high gene transfer ability, together with similar or lower cytotoxicity. Additionally, pDNA binding strength tests and zeta-potential assays reveal that the addition of an L part would reduce the charge density of the vector chains and thus lower the binding strength, leading to the easier release of pDNA from the complexes and an increase in transfection efficiency.

TAT modified and lipid - PEI hybrid nanoparticles for co-delivery of docetaxel and pDNA

BACKGROUND

Co-delivery of anticancer drugs and gene is promising to generate synergistic anticancer effects. Surface modification of nanocarriers with specific ligands could further assist in targeting and internalization of the nanocarriers into specific cell populations, such as cancers and disease organs.

PURPOSE

The aim of the study reported here is to develop Cell-penetrating peptides (CPPs) modified lipid - PEI hybrid nanoparticles (LPNs) for effective co-delivery of docetaxel (DTX) and plasmid DNA (pDNA) for combination chemotherapy.

METHODS

RKKRRQRRR peptide (TAT) modified, DTX and pDNA loaded LPNs (TAT-DTX/pDNA LPNs) were prepared and evaluated in PC3 cancer cells (in vitro) and in a murine prostate cancer model (in vivo).

RESULTS

The results illustrated that the in vitro anticancer effect, in vitro transfection efficiency, in vivo antitumor and gene delivery efficacy of TAT-DTX/pDNA LPNs have advantages over other formulation tested.

CONCLUSION

The results demonstrated that TAT-DTX/pDNA LPNs could be a promising co-delivery nano-system to achieve therapeutic efficacy for treatment of cancer.

Poly(ester amine) Composed of Polyethylenimine and Pluronic Enhance Delivery of Antisense Oligonucleotides In Vitro and in Dystrophic mdx Mice

A series of poly(esteramine)s (PEAs) constructed from low molecular weight polyethyleneimine (LPEI) and Pluronic were evaluated for the delivery of antisense oligonuclotides (AOs), 2'-O-methyl phosphorothioate RNA (2'-OMePS) and phosphorodiamidate morpholino oligomer (PMO) in cell culture and dystrophic mdx mice. Improved exon-skipping efficiency of both 2'-OMePS and PMO was observed in the C2C12E50 cell line with all PEA polymers compared with PEI 25k or LF-2k. The degree of efficiency was found in the order of PEA 01, PEA 04 > PEA 05 > others. The in vivo study in mdx mice demonstrated enhanced exon-skipping of 2'-OMePS with the order of PEA 06 > PEA 04, PEA 07 > PEA 03 > PEA 01 > others, and much higher than PEI 25k formulated 2'-OMePS. Exon-skipping efficiency of PMO in formulation with the PEAs were significantly enhanced in the order of PEA 02 > PEA 10 > PEA 01, PEA 03 > PEA 05, PEA 07, PEA 08 > others, with PEA 02 reaching fourfold of Endo-porter formulated PMO. PEAs improve PMO delivery more effectively than 2'-OMePS delivery in vivo, and the systemic delivery evaluation further highlight the efficiency of PEA for PMO delivery in all skeletal muscle. The results suggest that the flexibility of PEA polymers could be explored for delivery of different AO chemistries, especially for antisense therapy.

Synthesis of intracellular reduction-sensitive amphiphilic polyethyleneimine and poly(ε-caprolactone) graft copolymer for on-demand release of doxorubicin and p53 plasmid DNA

This study aims to present a new intelligent polymeric nano-system used for combining chemotherapy with non-viral gene therapy against human cancers. An amphiphilic copolymer synthesized through the conjugation of low molecular weight polyethyleneimine (LMw-PEI) and poly(ε-caprolactone) (PCL) via a bio-cleavable disulfide linkage was successfully employed for the simultaneous delivery of drug and gene molecules into target cells. Compared to the conventional PCL copolymerization pathway, this paper represents a straightforward and efficient reaction pathway including the activation of PCL-diol hydroxyl end groups, cystamine attachment and LMw-PEI conjugation which are successfully performed at mild conditions as confirmed by FTIR and (1)H NMR. Thermal, morphological characteristics as well as biocompatibility of the copolymer were investigated. The copolymer showed great tendency to form positively charged nanoparticles (∼163.1nm, +35.3mV) with hydrophobic core and hydrophilic shell compartments implicating its potential for encapsulation of anti-cancer drug and plasmid DNA, respectively. The gel retardation assay confirmed that the nanoparticles could successfully inhibit the migration of pDNA at ∼5 nanoparticle/pDNAw/w. The in vitro cytotoxicity tests and LDH assay revealed that the cationic amphiphilic copolymer was essentially non-toxic in different carcinoma cell lines in contrast to branched PEI 25K. Moreover, the presence of redox sensitive disulfide linkages provided smart nanoparticles with on-demand release behavior in response to reducing agents such as cytoplasmic glutathione (GSH). Importantly, confocal microscopy images revealed that in contrast to free Dox, the nanoparticles were capable of faster internalizing into the cells and accumulating in the perinuclear region or even in the nucleus. Finally, the co-delivery of Dox and p53-pDNA using the copolymer displayed greater cytotoxic effect compared with the Dox-loaded nanoparticle counterpart as revealed by cell viability and Caspase 3 expression assay. These results suggest the copolymer as a promising candidate for the development of smart delivery systems.

STATEMENT OF SIGNIFICANCE

We employed cystamine dihydrochloride as a disulfide linkage for the conjugation of PCL diol and low molecular weight PEI segments through a straightforward and efficient reaction pathway at mild conditions. The new copolymer was essentially non-toxic in different carcinoma cell lines and showed great tendency to form positively charged nanoparticles. Therefore, it can be utilized as a promising platform for simultaneous drug and gene delivery to aggressive cancers. The results of drug and gene co-delivery experiments confirmed the pivotal role of disulfide linkage on the controlled release of both drug and gene molecules in response to glutathione concentration gradient between extracellular and intracellular microenvironments. In addition, the co-delivery of doxorubicin and p53 plasmid DNA using the new copolymer displayed greater cytotoxic effect compared with single agent (i.e. Dox) loaded counterpart, which indicated the significance of rapid dissociation of therapeutic agents from the carrier for synergistic cytotoxic effects on cancer cells.

Modulated cellular delivery of anti-VEGF siRNA (bevasiranib) by incorporating supramolecular assemblies of hydrophobically modified polyamidoamine dendrimer in stealth liposomes

A novel lipopolymer based system was designed and characterized for cellular delivery of anti-VEGF siRNA in SKBR-3 breast tumor cell line. Polyamidoamine (PAMAM) dendrimers of low generations (G1, G2 and G3) were incorporated into polyethylene glycol (PEG)-stabilized liposomes by following the consecutive steps: (a) synthesis of the cholesterol conjugates (40% molar ratio of cholesterol to primary amines of PAMAM), (b) incorporation of the conjugates in liposome by lipid mixing and (c) microencapsulation of the siRNA using the ethanol drop method. The cholesterol conjugates of PAMAM dendrimers (G1-Chol40%, G2-Chol40% and G3-Chol40%) formed self assembly with low CMC values (<11μg/ml). Not only did G2-Chol40% show the highest lipid mixing among the cholesterol conjugates, but also, had the lowest leakage of encapsulated carboxyfluorescein tracer. Various N(amine))/L(lipid)/P(phosphate) mole ratios were investigated for siRNA condensation by ethidium bromide dye exclusion assay. The optimum N/L/P ratio of 20:33:10 was chosen for microencapsulation of anti-VEGF siRNA by ethanol drop method, showing particle size of 130nm, zeta-potential of +4mV, siRNA loading efficiency and capacity of 96% and 13wt%, and high stability against heparin sulfate (extracellular matrix). TEM shows uniform and discrete oligo- or multi-lamellar vesicular structures. The liposome incorporating G2-Chol40% was successfully internalized into SKBR-3 cells mainly through clathrin-mediated endocytosis, which was able to escape from endosomes and showed a significantly higher sequence-specific inhibition of VEGF expression and cell growth than the respective G2-Chol40%/siRNA dendriplexes. Importantly, the cytotoxicity decreased with incorporation of G2-Chol40% in the liposomes.

Small hydrophobe substitution on polyethylenimine for plasmid DNA delivery: Optimal substitution is critical for effective delivery

Cationic polymers have been turned into effective gene delivery agents by functionalizing with long-chain aliphatic lipids, but little information exists if small hydrophobic moieties can serve as effective substituents for this purpose. To explore this issue, we modified small molecular weight (1.2kDa) polyethylenimine (1.2PEI) by a small hydrophobe, propionic acid (PrA), through N-acylation and investigated the efficacy of resultant polymers to deliver plasmid DNA (pDNA) to breast cancer cells MDA-231 and MCF-7. A significant impact of PrA grafting was observed on physicochemical features of polymers and resultant pDNA complexes. pDNA binding capacity, as measured by BC50 (weight ratio for 50% binding), was decreased from 0.25 to 0.64 with PrA substitution. Hydrodynamic size of polymer/pDNA complexes was not altered, but the surface charge (ξ-potential) was increased with low PrA substitution and decreased at higher PrA substitutions. Similarly, in vitro pDNA transfection efficacy in MDA-231 and MCF-7 cells was significantly increased with PrA grafting and optimum efficacy was observed in polymers with modest substitution, 0.25-1.0 PrAs/PEI (mol/mol), but higher substitutions was detrimental to transfection. The transfection efficiency of PEI-PrAs was higher than aliphatic lipid (linoleic acid) substituted PEI and more stable than 25kDa branched PEI. However, unlike studies reported elsewhere, siRNA had no effect on transfection efficacy of pDNA/PEI-PrA complexes when used as an additive. We conclude that small hydrophobe substitution on low MW PEI converts it into effective pDNA delivery agent in breast cancer cells up to an optimal ratio, indicating that balancing hydrophobicity of polymer is critical for pDNA transfection.

STATEMENT OF SIGNIFICANCE

This manuscript investigated the influence of small hydrophobe (propionic acid, PrA, 3 carbon) grafted onto small molecular weight polyethylenimine (1.2PEI) in pDNA delivery. We have explored this approach as an alternative of common strategies to graft long chain and/or bulky lipids [linoleic acid (18 carbon), cholesterol]. At optimal substitution, transfection efficiency of these polymers was significantly higher than long chain lipid substituted 1.2PEI, emphasizing a proper hydrophobic/hydrophilic balance for optimum gene delivery. The overall results establish the feasibility of using small hydrophobes to create functional carriers, as long as the polymers are engineered with optimal ratio of substituent. The reported studies should facilitate the efforts of biomaterials scientists and engineers to design new carriers for gene therapy.

Tumor Acidity-Induced Sheddable Polyethylenimine-Poly(trimethylene carbonate)/DNA/Polyethylene Glycol-2,3-Dimethylmaleicanhydride Ternary Complex for Efficient and Safe Gene Delivery

Amphiphilic PEI derivatives/DNA complexes are widely used for DNA delivery, but they are unstable in vivo and have cytotoxicity due to the excess cationic charge. PEGylation of cationic complexes can improve sterical stability and biocompatibility. However, PEGylation significantly inhibits cellular uptake and endosomal escape. In this work, sheddable ternary complexes were developed by coating a tumor acidity-sensitive β-carboxylic amide functionalized PEG layer on the binary complexes of amphiphilic cationic polyethylenimine-poly(trimethylene carbonate) nanoparticles/DNA (PEI-PTMC/DNA). Such sheddable ternary complexes markedly reduced their nonspecific interactions with serum protein in the bloodstream and obtained minimal cytotoxicity due to the protection of the PEG shell. At the tumor site, the PEG layer was deshielded by responding to the tumor acidic microenvironment and the positively charged complexes re-exposed that had higher affinity with negatively charged cell membranes. Meanwhile the positively charged complexes facilitated endosomal escape. Accordingly, this delivery system improved the biocompatibility of gene-loaded complexes and enhanced the gene transfection efficiency. Such PEGylated complexes with the ability to deshield the PEG layer at the target tissues hold great promise for efficient and safe gene delivery in vivo.

Non-covalent complexes of folic acid and oleic acid conjugated polyethylenimine: An efficient vehicle for antisense oligonucleotide delivery

Polyethylenimine (PEI) was conjugated to oleic acid (PEI-OA) and evaluated as a delivery agent for LOR-2501, an antisense oligonucleotide against ribonucleotide reductase R1 subunit. PEI-OA/LOR-2501 complexes were further coated with folic acid (FA/PEI-OA/LOR-2501) and evaluated in tumor cells. The level of cellular uptake of FA/PEI-OA/LOR-2501 was more than double that of PEI/LOR-2501 complexes, and was not affected by the expression level of folate receptor (FR) on the cell surface. Efficient delivery was seen in several cell lines. Furthermore, pathway specific cellular internalization inhibitors and markers were used to reveal the principal mechanism of cellular uptake. FA/PEI-OA/LOR-2501 significantly induced the downregulation of R1 mRNA and R1 protein. This novel formulation of FA/PEI-OA provides a reliable and highly efficient method for delivery of oligonucleotide and warrants further investigation.