Cationic glycopolymers for the delivery of pDNA to human dermal fibroblasts and rat mesenchymal stem cells

Synergistic Polymer Blending Informs Efficient Terpolymer Design and Machine Learning Discerns Performance Trends for pDNA Delivery

Cationic polymers offer an alternative to viral vectors in nucleic acid delivery. However, the development of polymer vehicles capable of high transfection efficiency and minimal toxicity has remained elusive, and continued exploration of the vast design space is required. Traditional single polymer syntheses with large monomer bases are very time-intensive, limiting the speed at which new formulations are identified. In this work, we present an experimental method for the quick probing of the design space, utilizing a combinatorial set of 90 polymer blends, derived from 6 statistical copolymers, to deliver pDNA. This workflow facilitated rapid screening of polyplex compositions, successfully tailoring polyplex hydrophobicity, particle size, and payload binding affinity. This workflow identified blended polyplexes with high levels of transfection efficiency and cell viability relative to single copolymer controls and commercial JetPEI, indicating synergistic benefits from copolymer blending. Polyplex composition was coupled with biological outputs to guide the synthesis of single terpolymer vehicles, with high-performing polymers P10 and M20, providing superior transfection of HEK293T cells in serum-free and serum-containing media, respectively. Machine learning coupled with SHapley Additive exPlanations (SHAP) was used to identify polymer/polyplex attributes that most impact transfection efficiency, viability, and overall effective efficiency. Subsequent transfections on ARPE-19 and HDFn cells found that P10 and M20 were surpassed in performance by M10, contrasting with results in HEK293T cells. This cell type dependency reinforced the need to evaluate transfection conditions with multiple cell models to potentially identify moieties more beneficial to delivery in certain tissues. Overall, the workflow employed can be used to expedite the exploration of the polymer design space, bypassing extensive synthesis, and to develop improved polymer delivery vehicles more readily for nucleic acid therapies.

Synthesis and Application of Trehalose Materials

Trehalose is a naturally occurring, nonreducing disaccharide that is widely used in the biopharmaceutical, food, and cosmetic industries due to its stabilizing and cryoprotective properties. Over the years, scientists have developed methodologies to synthesize linear polymers with trehalose units either in the polymer backbone or as pendant groups. These macromolecules provide unique properties and characteristics, which often outperform trehalose itself. Additionally, numerous reports have focused on the synthesis and formulation of materials based on trehalose, such as nanoparticles, hydrogels, and thermoset networks. Among many applications, these polymers and materials have been used as protein stabilizers, as gene delivery systems, and to prevent amyloid aggregate formation. In this Perspective, recent developments in the synthesis and application of trehalose-based linear polymers, hydrogels, and nanomaterials are discussed, with a focus on utilization in the biomedical field.

Carbohydrate-Based Macromolecular Biomaterials

Carbohydrates are the most abundant and one of the most important biomacromolecules in Nature. Except for energy-related compounds, carbohydrates can be roughly divided into two categories: Carbohydrates as matter and carbohydrates as information. As matter, carbohydrates are abundantly present in the extracellular matrix of animals and cell walls of various plants, bacteria, fungi, etc., serving as scaffolds. Some commonly found polysaccharides are featured as biocompatible materials with controllable rigidity and functionality, forming polymeric biomaterials which are widely used in drug delivery, tissue engineering, etc. As information, carbohydrates are usually referred to the glycans from glycoproteins, glycolipids, and proteoglycans, which bind to proteins or other carbohydrates, thereby meditating the cell-cell and cell-matrix interactions. These glycans could be simplified as synthetic glycopolymers, glycolipids, and glycoproteins, which could be afforded through polymerization, multistep synthesis, or a semisynthetic strategy. The information role of carbohydrates can be demonstrated not only as targeting reagents but also as immune antigens and adjuvants. The latter are also included in this review as they are always in a macromolecular formulation. In this review, we intend to provide a relatively comprehensive summary of carbohydrate-based macromolecular biomaterials since 2010 while emphasizing the fundamental understanding to guide the rational design of biomaterials. Carbohydrate-based macromolecules on the basis of their resources and chemical structures will be discussed, including naturally occurring polysaccharides, naturally derived synthetic polysaccharides, glycopolymers/glycodendrimers, supramolecular glycopolymers, and synthetic glycolipids/glycoproteins. Multiscale structure-function relationships in several major application areas, including delivery systems, tissue engineering, and immunology, will be detailed. We hope this review will provide valuable information for the development of carbohydrate-based macromolecular biomaterials and build a bridge between the carbohydrates as matter and the carbohydrates as information to promote new biomaterial design in the near future.

Bioreducible poly(urethane amine)s for robust nucleic acid transfection in stem cells

The search for cationic polymeric carriers enabling robust gene transfection against stem cells remains a challenge. Herein, linear bioreducible poly(urethane amine)s (denoted as SSPUAs) with repeated disulfide and protonable amino groups were prepared and used as non-viral vectors for in vitro gene transfection of different stem cells. The polyurethane copolymers (denoted as SSBT) with varied molar ratios of 1,4-bis(3-aminopropyl)piperazine (BAP) and tris(2-aminoethyl) amine (TAA) moieties could lead to superb transfection activity against human adipose-derived stem cells (hADSCs) and human bone marrow stem cells (hBMSCs). Data indicated that under optimal transfection conditions, SSBT10 with a BAP/TAA molar ratio of 90/10 caused the transfection of ∼60% of green fluorescence protein-positive (GFP⁺) hADSCs, and SSBT30 with the ratio of 70/30 resulted in the transfection of ∼40% of GFP⁺ hBMSCs. Also, the SSBT30 and polyurethane with BAP residues (denoted as SSBAP) could mediate efficient gene transfer into bone marrow stem cells of experimental animals such as SD rats, beagle dogs and rhesus monkeys, with ∼40-70% of GFP⁺ cells. Additionally, the SSBAP elicited robust transfection ability (∼60% of GFP⁺ cells) against E14 mouse embryonic stem cells without compromising the expression of multipotent stemness-related markers of the cells. Importantly, the transfection efficiencies of these SSPUAs were higher as compared to those yielded by 25 kDa branched polyethylenimine and Lipofectamine 2000 reagents as positive controls. The SSBT30 was further practical to deliver siRNAs into hADSCs for BCL2L2 or TRIB2 gene silencing, causing superior gene silencing efficacy to Lipofectamine 2000. Besides their high gene transfection or silencing efficacy, these SSPUAs revealed low cytotoxicity against stem cells. This study highlights the SSPUA system as a distinct platform for robust nucleic acid delivery into stem cells.

Nonviral Gene Delivery with Cationic Glycopolymers

The field of gene therapy, which aims to treat patients by modulating gene expression, has come to fruition and has landed several landmark FDA approvals. Most gene therapies currently rely on viral vectors to deliver nucleic acid cargo into cells, but there is significant interest in moving toward chemical-based methods, such as polymer-based vectors, due to their low cost, immunocompatibility, and tunability. The full potential of polymer-based delivery systems has yet to be realized, however, because most polymeric transfection reagents are either too inefficient or too toxic for use in the clinic. In this Account, we describe developments in carbohydrate-based cationic polymers, termed glycopolymers, for enhanced nonviral gene delivery. As ubiquitous components of biological systems, carbohydrates are a rich class of compounds that can be harnessed to improve the biocompatibility of non-native polymers, such as linear polyamines used for promoting transfection. Reineke et al. developed a new class of carbohydrate-based polymers called poly(glycoamidoamine)s (PGAAs) by step-growth polymerization of linear monosaccharides with linear ethyleneamines. These glycopolymers were shown to be both efficient and biocompatible transfection reagents. Systematic modifications of the structural components of the PGAA system revealed structure-activity relationships important to its function, including its ability to degrade in situ. Expanding upon the development of step-growth glycopolymers, monosaccharides, such as glucose, were functionalized as vinyl-based monomers for the formation of diblock copolymers via radical addition-fragmentation chain-transfer (RAFT) polymerization. Upon complexation with plasmid DNA, the glucose-containing block creates a hydrophilic shell that promotes colloidal stability as effectively as PEG functionalization. An N-acetyl-d-galactosamine variant of this diblock polymer yields colloidally stable particles that show increased receptor-mediated uptake by liver hepatocytes in vitro and promotes liver targeting in mice. Finally, the disaccharide trehalose was incorporated into polycationic structures using both step-growth and RAFT techniques. It was shown that these trehalose-based copolymers imparted increased colloidal stability and yielded plasmid and siRNA polyplexes that resist aggregation upon lyophilization and reconstitution in water. The aforementioned series of glycopolymers use carbohydrates to promote effective and safe delivery of nucleic acid cargo into a variety of human cells types by promoting vehicle degradation, tissue-targeting, colloidal stabilization, and stability toward lyophilization to extend shelf life. Work is currently underway to translate the use of glycopolymers for safe and efficient delivery of nucleic acid cargo for gene therapy and gene editing applications.

Prolonged release of bone morphogenetic protein-2 in vivo by gene transfection with DNA-functionalized calcium phosphate nanoparticle-loaded collagen scaffolds

In the combination of scaffolds immersed in growth factor solutions, the release of growth factors mainly depends on scaffold degradation. However, the release of bone morphogenetic protein (BMP)-2 at an appropriate concentration during the stage of tissue regeneration would enhance bone regeneration. To achieve this condition, the present study was performed to investigate the effects of scaffolds combined with gene transfection using non-viral vectors. Nanohydroxyapatite-collagen (nHAC) scaffolds cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) or ascorbic acid/copper chloride, and a collagen scaffold (Terdermis®) were prepared, loaded with BMP-2-encoding plasmid DNA-functionalized calcium phosphate nanoparticles (CaP), naked plasmid DNA, or BMP-2 solution, and implanted in rats. The yield of released BMP-2 and its releasing period, respectively, were larger and longer from the scaffolds loaded with CaP than from those incubated with BMP-2 solution. In addition, the alkaline phosphatase activity induced by the CaP-loaded scaffolds was higher. Histological analysis showed that released BMP-2 could be observed on the macrophages or multinuclear giant cells surrounding the nHAC fragments or collagen fibres. TRAP-positive or OCN-positive sites were observed in all groups and a mineralization area was observed in the Terdermis®/CaP sample. The present study demonstrates that gene transfection by scaffold loaded with CaP gene transfer vectors induces a larger yield of BMP-2 for a longer period than by scaffolds loaded with BMP-2 solution or naked plasmid.

Down-regulation of Noggin and miR-138 coordinately promote osteogenesis of mesenchymal stem cells

Mesenchymal stem cells (MSCs) can differentiate to osteocytes under suitable conditions. In recent years, micro-nucleotides have been progressively used to modulate gene expression in cells due to the consideration of safety. Our present study aimed to investigate whether co-delivery of Noggin-siRNA and antimiR-138 enhances the osteogenic effect of MSCs. Using a murine MSC line, C3H/10T1/2 cells, the delivery efficiency of Noggin-siRNA and antimiR-138 into MSCs was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). Cell phenotype and proliferation capacity was assessed by flow cytometry and MTT assay respectively. The osteogenesis of MSCs was tested by Alkaline Phosphatase (ALP) staining, qRT-PCR, and western blot analyses. Our results demonstrated that the expression of Noggin and miR-138 were significantly silenced in MSCs by Noggin-siRNA and/or antimiR-138 delivery, while the phenotype and proliferation capacity of MSCs were not affected. Down-regulation of Noggin and miR-138 cooperatively promoted osteogenic differentiation of MSCs. The ALP positive cells reached about 83.57 ± 10.18%. Compared with single delivery, the expression of osteogenic related genes, such as Alp, Col-1, Bmp2, Ocn and Runx2, were the highest in cells with co-delivery of the two oligonucleotides. Moreover, the protein level of RUNX2, and the ratios of pSMAD1/5/SMAD1/5 and pERK1/2/ERK1/2 were significantly increased. The activation of Smad, Erk signaling may constitute the underlying mechanism of the enhanced osteogenesis process. Taken together, our study provides a safe strategy for the clinical rehabilitation application of MSCs in skeletal deficiency.

A glucose-targeted mixed micellar formulation outperforms Genexol in breast cancer cells

Breast cancer represents the top cancer among women, accounting 521.000 deaths per year. Development of targeted nanomedicines to breast cancer tissues represents a milestone to reduce chemotherapy side effects. Taking advantage of the over-expression of glucose (Glu) membrane transporters in breast cancer cells, we aim to expand the potential of a paclitaxel (PTX)-loaded mixed micellar formulation based on polyvinyl caprolactam-polyvinylacetate-polyethylene glycol graft copolymer (Soluplus®) and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) by its surface decoration with Glu moieties. The glycopolymer (Soluplus(Glu)) was obtained by microwave-assisted ring opening reaction of δ-gluconolactone initiated by Soluplus®. The glycosylation was confirmed by ¹H NMR and by agglutination assays employing Concanavalin A. The hydrodynamic diameter of Soluplus(Glu) micelles was characterized by dynamic light scattering (100.3±3.8nm) as well as the critical micellar concentration value (0.0151% w/v). Then, a mixed micelle formulation employing Soluplus®, Soluplus(Glu) and TPGS (3:1:1wt ratio) loaded with PTX (4mg/mL) was developed as a multifunctional nanocarrier. Its in vitro anticancer performance in MCF-7 (1.6-fold) and MDA-MB-231 (14.1-fold) was significantly enhanced (p<0.05) versus the unique commercially available micellar-based PTX-nanoformulation (Genexol®). Furthermore, the in vitro PTX cellular uptake assays revealed that the drug intracellular/cell content was significantly (p<0.05) higher for the Glu-containing mixed micelles versus Genexol® after 6h of incubation with MCF-7 (30.5-fold) and MDA-MB-231 (5-fold). Overall, results confirmed the potential of our Glu-decorated mixed colloidal formulation as an intelligent nanocarrier for PTX-targeted breast cancer chemotherapy.

Monomer design strategies to create natural product-based polymer materials

In an effort towards enhancing function and sustainability, natural products have become of interest in the field of polymer chemistry.

Rheological and mechanical study of regenerated cellulose/multi-walled carbon nanotube composites

Regenerated cellulose (RC)-based composites reinforced with multi-walled carbon nanotubes (MWCNTs) were prepared by a facile casting method. The morphology and microstructure of the fabricated composites were characterized using transmission electron microscopy, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Thermogravimetry and derivative thermogravimetric analysis were conducted to investigate the effect of MWCNTs on the thermal behaviors of the RC. The results showed that the introduction of MWCNTs enhanced the thermal stability of the RC. Moreover, the effect of the dispersion state of MWCNTs in microcrystalline cellulose/ZnCl2 solutions with varying MWCNT loadings was studied by rheological tests. The mechanical properties of composite films were remarkably improved compared to those of pure RC film. Specifically, the composite film containing 3 wt% of MWCNTs exhibits a 123% enhancement in tensile strength and a 163% enhancement in the Young's modulus compared with the pure RC film.

Influence of Growth Characteristics of Induced Pluripotent Stem Cells on Their Uptake Efficiency for Layer-by-Layer Microcarriers

Induced pluripotent stem cells (iPSCs) have the ability to differentiate into any specialized somatic cell type, which makes them an attractive tool for a wide variety of scientific approaches, including regenerative medicine. However, their pluripotent state and their growth in compact colonies render them difficult to access and, therefore, restrict delivery of specific agents for cell manipulation. Thus, our investigation focus was set on the evaluation of the capability of layer-by-layer (LbL) designed microcarriers to serve as a potential drug delivery system to iPSCs, as they offer several appealing advantages. Most notably, these carriers allow for the transport of active agents in a protected environment and for a rather specific delivery through surface modifications. As we could show, charge and mode of LbL carrier application as well as the size of the iPSC colonies determine the interaction with and the uptake rate by iPSCs. None of the examined conditions had an influence on iPSC colony properties such as colony morphology and size or maintenance of pluripotent properties. An overall interaction rate of LbL carriers with iPSCs of up to 20% was achieved. Those data emphasize the applicability of LbL carriers for stem cell research. Additionally, the potential use of LbL carriers as a promising delivery tool for iPSCs was contrasted to viral particles and liposomes. The identified differences among those delivery tools have substantiated our major conclusion that LbL carrier uptake rate is influenced by characteristic features of the iPSC colonies (most notably colony size) in addition to their surface charges.

Controlled release and antibacterial activity of tetracycline hydrochloride-loaded bacterial cellulose composite membranes

Bacterial cellulose (BC) is widely used in biomedical applications. In this study, we prepared an antibiotic drug tetracycline hydrochloride (TCH)-loaded bacterial cellulose (BC) composite membranes, and evaluated the drug release, antibacterial activity and biocompatibility. The structure and morphology of the fabricated BC-TCH composite membranes were characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The TCH release results show that the incorporation of BC matrix to load TCH is able to control the release. In vitro antibacterial assay demonstrate that the developed BC-TCH composites displayed excellent antibacterial activity solely associated with the loaded TCH drug. More importantly, the BC-TCH composite membranes display good biocompatibility. These characteristics of BC-TCH composite membranes indicate that they may successfully serve as wound dressings and other medical biomaterials.

CD44 Mediated Nonviral Gene Delivery into Human Embryonic Stem Cells via Hyaluronic-Acid-Coated Nanoparticles

Gene delivery is an important tool to study and manipulate human pluripotent stem cells for regenerative medicine purposes. Yet current methods of transient gene delivery to stem cells are still inefficient. Through the combination of biologically based concepts and material design, we aim to develop new methods to enhance the efficiency of gene delivery to stem cells. Specifically, we use poly(γ-4-(((2-(piperidin-1-yl)ethyl)amino)methyl)benzyl-l-glutamate) (PVBLG-8), a membrane-active helical, cationic polypeptide, to condense plasmid DNA to form stable nanocomplexes, which are further coated with hyaluronic acid (HA). HA not only shields the positive charges of PVBLG-8 to reduce toxicity, but also acts as a targeting moiety for cell surface receptor CD44, which binds HA and facilitates the internalization of the nanocomplexes. Upon entering cells, HA is degraded by hyaluronidase in endosomes and PVBLG-8 is exposed, facilitating the endosomal escape of DNA/polypeptide complex. Our studies show that the coating of HA significantly increases gene transfection efficiency of DNA/PVBLG-8 nanocomplexes from about 28 to 36% with largely reduced toxicity.

A protocol for amide bond formation with electron deficient amines and sterically hindered substrates

A protocol for amide coupling by in situ formation of acyl fluorides and reaction with amines at elevated temperature has been developed and found to be efficient for coupling of sterically hindered substrates and electron deficient amines where standard methods failed.

A theranostic polycation containing trehalose and lanthanide chelate domains for siRNA delivery and monitoring

A trehalose-based polycation that contains lanthanide-chelate domains has been examined as a theranostic vehicle for siRNA delivery.

Improvements in biomaterial matrices for neural precursor cell transplantation

Progress is being made in developing neuroprotective strategies for traumatic brain injuries; however, there will never be a therapy that will fully preserve neurons that are injured from moderate to severe head injuries. Therefore, to restore neurological function, regenerative strategies will be required. Given the limited regenerative capacity of the resident neural precursors of the CNS, many investigators have evaluated the regenerative potential of transplanted precursors. Unfortunately, these precursors do not thrive when engrafted without a biomaterial scaffold. In this article we review the types of natural and synthetic materials that are being used in brain tissue engineering applications for traumatic brain injury and stroke. We also analyze modifications of the scaffolds including immobilizing drugs, growth factors and extracellular matrix molecules to improve CNS regeneration and functional recovery. We conclude with a discussion of some of the challenges that remain to be solved towards repairing and regenerating the brain.

Improvements in biomaterial matrices for neural precursor cell transplantation

Progress is being made in developing neuroprotective strategies for traumatic brain injuries; however, there will never be a therapy that will fully preserve neurons that are injured from moderate to severe head injuries. Therefore, to restore neurological function, regenerative strategies will be required. Given the limited regenerative capacity of the resident neural precursors of the CNS, many investigators have evaluated the regenerative potential of transplanted precursors. Unfortunately, these precursors do not thrive when engrafted without a biomaterial scaffold. In this article we review the types of natural and synthetic materials that are being used in brain tissue engineering applications for traumatic brain injury and stroke. We also analyze modifications of the scaffolds including immobilizing drugs, growth factors and extracellular matrix molecules to improve CNS regeneration and functional recovery. We conclude with a discussion of some of the challenges that remain to be solved towards repairing and regenerating the brain.

Mitogen-activated protein kinase (MAPK) phosphatase-3 (MKP-3) displays a p-JNK-MAPK substrate preference in astrocytes in vitro

Mitogen-activated protein kinases (MAPKs) play critical roles in the central nervous system immune responses through glial function, which are regulated with relative selectivity (or preference) by MAPK phosphatases (MKP). Phosphorylated extracellular signal-regulated protein kinase (p-ERK) is preferentially dephosphorylated by MKP-3, which display little activity over p-p38 and p-c-Jun NH2-terminal kinases (p-JNK). It has been proposed that these substrate preferences may vary depending on tissue or functional cellular processes. Since astrocytes display a prominent activity of JNK>ERK under stressed or reactive phenotype, we hypothesize that MKP-3 possess a similar or differential substrate preference in astrocytes for JNK and ERK (ERK=JNK or JNK>ERK). We generated transient expression of MKP-3 by transfecting a specific cDNA in primary rat neonatal brain cortex astrocytes. Cells were stimulated with lipopolysaccharide (LPS), and MAPKs and downstream pro-inflammatory products were measured by Western blot and ELISA analyses. MKP-3 expression in primary astrocytes reduced LPS-induced p-ERK and p-p38 by ∼50%, and p-JNK by ∼75%, and moderately reduced nitrite oxide (NO), while completely blocked Interleukin (IL)-6 and tumor necrosis factor alpha (TNFα). We confirmed MKP-3 specific activity by developing a BV-2 microglia cell line stably overexpressing MKP-3 and using a specific siRNA against MKP-3. Our data demonstrate MKP-3 has differential substrate preference in astrocytes compared to other cells types, since it preferentially dephosphorylated p-JNK over p-ERK. Our results indicate also that astrocytic immune functions can be modulated by MKP-3 induction, a strategy that could be beneficial in neurological conditions in which astrocytes play a pathophysiological role, i.e. persistent pain.

Enhanced Non-Viral Gene Delivery to Human Embryonic Stem Cells via Small Molecule-Mediated Transient Alteration of Cell Structure

Non-viral gene delivery into human embryonic stem cells (hESCs)is an important tool for controlling cell fate. However, the delivery efficiency remains low due in part to the tight colony structure of the cells which prevents effective exposure towards delivery vectors. We herein report a novel approach to enhance non-viral gene delivery to hESCs by transiently altering the cell and colony structure. (R)-(+)-trans-4-(1-aminoethyl)-N-(4-pyridyl)cyclohexanecarboxamide (Y-27632), a small molecule that inhibits the rho-associated protein kinase pathway, is utilized to induce transient colony spreading which leads to increased transfection efficiency by 1.5 to 2 folds in a spectrum of non-viral transfection reagents including Lipofectamine 2000 and Fugene HD. After removal of Y-27632 post-transfection, cells can revert back to its normal state and do not show alteration of pluripotency. This approach provides a simple, effective tool to enhance non-viral gene delivery into adherent hESCs for genetic manipulation.

Poly(N-isopropylacrylamide-co-acrylic acid) nanogels for tracing and delivering genes to human mesenchymal stem cells

Drugs, proteins, and cells can be macro- and micro-encapsulated by unique materials that respond to specific stimuli. The phases and hydrophobic interactions of these materials are reversibly altered by environmental stimuli such as pH and temperature. These changes can lead to self-assembly of the materials, which enables controlled drug release and safe gene delivery into cells and tissues. The fate of stem cells delivered by such methods is of great interest. The formation of transgenic tissues requires genes to be delivered safely into stem cells. A cell tracing vehicle and a gene delivery carrier were simultaneously introduced into human mesenchymal stem cells (hMSCs). A thermo-sensitive hydrogel, poly(N-isopropylacrylamide-co-acrylic acid) (p(NiPAAm-co-AAc)), was created to generate self-assembled nanoparticles with nanogel characteristics. Hydrophobic interactions mediated the binding of the carboxyl group on the outside of p(NiPAAm-co-AAc) with the amine group of iron oxide. Nanogels carrying iron oxide and a fluorescent dye were complexed with specific genes. These nanogels could be internalized by hMSCs, and the transplantation of these cells into mice was monitored by in vivo imaging. Self-assembled p(NiPAAm-co-dAAc) nanogels complexed with green fluorescent protein were highly expressed in hMSCs and are a potential material for gene delivery.

Oligoamines grafted hyperbranched polyether as high efficient and serum-tolerant gene vectors

To develop low toxic, high efficient, and excellent serum-tolerant polycation gene delivery systems, a series of oligoamines grafted hyperbranched polyether (oligoamines-g-HBP) were synthesized by conjugating different oligoamines, including triethylenetetramine (TETA) and tetraethylenepentamine (TEPA), onto COOH-functionalized hyperbranched poly(3-ethyl-3-oxetanemethanol). It was found that oligoamines-g-HBP exhibited good buffering capacity, strong DNA binding and high resistance against protein adsorption. In vitro cytotoxicity measurement indicated that oligoamines-g-HBP had much lower cytotoxicity as compared with 25 kDa PEI. The transfection efficiency of TEPA-g-HBP/DNA complexes at a certain N/P ratio was significantly higher than that of 25 kDa PEI/DNA complexes. Interestingly, it was found that TEPA-g-HBP had much improved serum-tolerant capability as compared with 25 kDa PEI even when serum concentration was increased to 30%. Confocal laser images further showed that the amount of YOYO-1 labeled DNA in nuclei got increased with increasing the number of secondary amino ethylene groups in oligoamines-g-HBP. The oligoamines-g-HBP presented great potential as gene delivery vectors for further clinical applications.

Cationic, helical polypeptide-based gene delivery for IMR-90 fibroblasts and human embryonic stem cells

Diblock copolymers consisting of poly(ethylene glycol)-block-poly(γ-4-(((2-(piperidin-1-yl)ethyl)amino)methyl)benzyl-L-glutamate) (PEG-b-PVBLG-8) were synthesized and evaluated for their ability to mediate gene delivery in hard-to-transfect cells like IMR-90 human fetal lung fibroblasts and human embryonic stem cells (hESCs). The PEG-b-PVBLG-8 contained a membrane-disruptive, cationic, helical polypeptide block (PVBLG-8) for complexing with DNA and a hydrophilic PEG block to improve the biocompatibility of the gene delivery vehicle. The incorporation of PEG effectively reduced the toxicity of the helical PVBLG-8 block without dramatically compromising the polymer's ability to destabilize membranes or form complexes with DNA. PEG-b-PVBLG-8 copolymers with low (n = 76) and high (n = 287) degrees of polymerization (n) of the PVBLG-8 block were synthesized and evaluated for gene delivery. PEG-b-PVBLG-8 diblock polymers with a high degree of polymerization have a greater transfection efficiency and lower toxicity in IMR-90 cells than the commercial reagent Lipofectamine 2000. The usefulness of PEG-b-PVBLG-8 was further demonstrated via the successful transfection of hESCs without a measured loss in cell pluripotency markers.

Spinal cannabinoid receptor type 2 agonist reduces mechanical allodynia and induces mitogen-activated protein kinase phosphatases in a rat model of neuropathic pain

Peripheral nerve injury generally results in spinal neuronal and glial plastic changes associated with chronic behavioral hypersensitivity. Spinal mitogen-activated protein kinases (MAPKs), eg, p38 or extracellular signal-regulated kinases (ERKs), are instrumental in the development of chronic allodynia in rodents, and new p38 inhibitors have shown potential in acute and neuropathic pain patients. We have previously shown that the cannabinoid type 2 receptor agonist JWH015 inhibits ERK activity by inducing MAPK phosphatase (MKP)-1 and MKP-3 (the major regulators of MAPKs) in vitro in microglial cells. Therefore, we decided to investigate the role of these phosphatases in the mechanisms of action of JWH015 in vivo using the rat L5 nerve transection model of neuropathic pain. We observed that peripheral nerve injury reduced spinal MKP-1/3 expression and activity and that intrathecal JWH015 reduced established L5 nerve injury-induced allodynia, enhanced spinal MKP-1/3 expression and activity, and reduced the phosphorylated form of p38 and ERK-1/2. Triptolide, a pharmacological blocker of MKP-1 and MKP-3 expression, inhibited JWH015's effects, suggesting that JWH015 exerts its antinociceptive effects by modulating MKP-1 and MKP-3. JWH015-induced antinociception and MKP-1 and MKP-3 expression were inhibited by the cannabinoid type 2 receptor antagonist AM630. Our data suggest that MKP-1 and MKP-3 are potential targets for novel analgesic drugs.

PERSPECTIVE

MAPKs are pivotal in the development of chronic allodynia in rodent models of neuropathic pain. A cannabinoid type 2 receptor agonist, JWH015, reduced neuropathic allodynia in rats by reducing MAPK phosphorylation and inducing spinal MAPK phosphatases 1 and 3, the major regulators of MAPKs.

Exploring the mechanism of plasmid DNA nuclear internalization with polymer-based vehicles

Cationic polymers are commonly used to transfect mammalian cells, but their mechanisms of DNA delivery are unknown. This study seeks to decipher the mechanism by which plasmid DNA delivered by a class of cationic polymers traffics to and enters the nucleus. While studies have been performed to elucidate the mechanism of naked plasmid DNA (pDNA) import into the nuclei of mammalian cells, our objectives were to determine the effects of polymer complexation on pDNA nuclear import and the impact of polymer structure on that import. We have performed studies in whole cells and in isolated nuclei using flow cytometry and confocal microscopy to characterize how polymer-DNA complexes (polyplexes) are able to deliver their pDNA cargo to the nuclei of their target cells. The polymers tested herein include (i) linear poly(ethylenimine) (JetPEI), a polyamine, and (ii) two poly(glycoamidoamine)s (PGAAs), polyamines that contain carbohydrate moieties (meso-galactarate, Glycofect (G4), and L-tartarate, T4) within their repeat units. Our results indicate that, when complexed with the PGAAs, pDNA association with the nuclei was severely hampered in isolated nuclei compared to whole cells. When the pDNA was complexed with JetPEI, there was slight inhibition of pDNA-nuclear interaction in isolated nuclei compared to whole cells. However, even in the case of PEI, the amount of pDNA imported into the nucleus increases in the presence of cytosolic extract, thus indicating that intracellular components also play a role in pDNA nuclear import for all polymers tested. Interestingly, PEI and G4 exhibit the highest reporter gene expression as well as inducing higher envelope permeability compared to T4, suggesting that the ability to directly permeabilize the nuclear envelope may play a role in increasing expression efficiency. In addition, both free T4 and G4 polymers are able to cross the nuclear membrane without their pDNA cargo in isolated nuclei, indicating the possibility of different modes of nuclear association for free polymers vs polyplexes. These results yield insight to how the incorporation of carbohydrate moieties influences intracellular mechanisms and will prove useful in the rational design of safe and effective polymer-based gene delivery vehicles for clinical use.

Impact of the nature, size and chain topologies of carbohydrate-phosphorylcholine polymeric gene delivery systems

With the recent significant advances in the field polymer chemistry, it is now possible to produce well-defined and non-toxic cationic polymers with advanced molecular structures of desired molecular weights and compositions. Carefully engineered polymer architectures are found to impact significantly their DNA condensation and gene delivery efficacies. In a previous study, the statistical carbohydrates based copolymers were found to show high gene expression and low toxicity, however there aggregation in the presence of serum proteins was a major drawback. In this study, carbohydrate and phosphorylcholine based cationic polymers having a different architecture, compositions and varying molecular weights are produced and are termed as cationic 'block-statistical' copolymers. These cationic copolymers are evaluated for their gene delivery efficacies, interactions with serum protein, cellular uptake and nuclear localization ability. As compared to the statistical analogue, 'block-statistical' copolymers showed high gene expression, low interactions with serum proteins, as well as low toxicity in hepatocytes and human dermal fibroblasts. In addition, 2- methacryloyloxyethyl phosphorylcholine (MPC) based 'block-statistical' copolymers and their sugar incorporated analogues were prepared and were found to serve as improved gene delivery vectors than their statistical analogues.

Effects of trehalose polycation end-group functionalization on plasmid DNA uptake and transfection

In this study, we have synthesized six analogs of a trehalose-pentaethylenehexamine glycopolymer (Tr4) that contain (1A) adamantane, (1B) carboxy, (1C) alkynyl-oligoethyleneamine, (1D) azido trehalose, (1E) octyl, or (1F) oligoethyleneamine end groups and evaluated the effects of polymer end group chemistry on the ability of these systems to bind, compact, and deliver pDNA to cultured HeLa cells. The polymers were synthesized in one-pot azide-alkyne cycloaddition reactions with an adaptation of the Carothers equation for step-growth polymerization to produce a series of polymers with similar degrees of polymerization. An excess of end-capping monomer was added at the end of the polymerizations to maximize functionalization efficiency, which was evaluated with GPC, NMR, and MALDI-TOF. The polymers were all found to bind and compact pDNA at similarly low N/P ratios and form polyplexes with plasmid DNA. The effects of the different end group structures were most evident in the polyplex internalization and transfection assays in the presence of serum as determined by flow cytometry and luciferase gene expression, respectively. The Tr4 polymers end-capped with carboxyl groups (1B) (N/P = 7), octyne (1E) (N/P = 7), and oligoethyleneamine (1F) (N/P = 7), were taken into cells as polyplex and exhibited the highest levels of fluorescence, resulting from labeled plasmid. Similarly, the polymers end-functionalized with carboxyl groups (1E at N/P = 7), octyl groups (1E at N/P = 15), and in particular oligoethyleneamine groups (1F at N/P = 15) yielded dramatically higher reporter gene expression in the presence of serum. This study yields insight into how very subtle structural changes in polymer chemistry, such as end groups can yield very significant differences in the biological delivery efficiency and transgene expression of polymers used for pDNA delivery.

Mitogen activated protein kinase phosphatase-1 prevents the development of tactile sensitivity in a rodent model of neuropathic pain

Background

Neuropathic pain due to nerve injury is one of the most difficult types of pain to treat. Following peripheral nerve injury, neuronal and glial plastic changes contribute to central sensitization and perpetuation of mechanical hypersensitivity in rodents. The mitogen activated protein kinase (MAPK) family is pivotal in this spinal cord plasticity. MAPK phosphatases (MKPs) limit inflammatory processes by dephosphorylating MAPKs. For example, MKP-1 preferentially dephosphorylates p-p38. Since spinal p-p38 is pivotal for the development of chronic hypersensitivity in rodent models of pain, and p-p38 inhibitors have shown clinical potential in acute and chronic pain patients, we hypothesize that induction of spinal MKP-1 will prevent the development of peripheral nerve-injury-induced hypersensitivity and p-p38 overexpression.

Results

We cloned rat spinal cord MKP-1 and optimize MKP-1 cDNA in vitro using transfections to BV-2 cells. We observed that in vitro overexpression of MKP-1 blocked lipopolysaccharide-induced phosphorylation of p38 (and other MAPKs) as well as release of pro-algesic effectors (i.e., cytokines, chemokines, nitric oxide). Using this cDNA MKP-1 and a non-viral, in vivo nanoparticle transfection approach, we found that spinal cord overexpression of MKP-1 prevented development of peripheral nerve-injury-induced tactile hypersensitivity and reduced pro-inflammatory cytokines and chemokines and the phosphorylated form of p38.

Conclusions

Our results indicate that MKP-1, the natural regulator of p-p38, mediates resolution of the spinal cord pro-inflammatory milieu induced by peripheral nerve injury, resulting in prevention of chronic mechanical hypersensitivity. We propose that MKP-1 is a potential therapeutic target for pain treatment or prevention.