Nonviral gene delivery to T cells with Lipofectamine LTX.

Retroviral gene delivery is widely used in T cell therapies for hematological cancers. However, viral vectors are expensive to manufacture, integrate genes in semirandom patterns, and their transduction efficiency varies between patients. In this study, several nonviral gene delivery vehicles, promoters, and additional variables were compared to optimize nonviral transgene delivery and expression in both Jurkat and primary T cells. Transfection of Jurkat cells was maximized to a high efficiency (63.0% ± 10.9% EGFP+  cells) by transfecting cells with Lipofectamine LTX in X-VIVO 15 media. However, the same method yielded a much lower transfection efficiency in primary T cells (8.1% ± 0.8% EGFP+ ). Subsequent confocal microscopy revealed that a majority of the lipoplexes did not enter the primary T cells, which might be due to relatively low expression levels of heparan sulfate proteoglycans detected via messenger RNA-sequencing. Pyrin and HIN (PYHIN) DNA sensors (e.g., AIM2 and IFI16) that can induce apoptosis or repress transcription after binding cytoplasmic DNA were also detected at high levels in primary T cells. Therefore, transfection of primary T cells appears to be limited at the level of cellular uptake or DNA sensing in the cytoplasm. Both of these factors should be considered in the development of future viral and nonviral T cell gene delivery methods.

Tuning the Topological Landscape of DNA-Cyclodextrin Nanocomplexes by Molecular Design.

Original molecular vectors that ensure broad flexibility to tune the shape and surface properties of plasmid DNA (pDNA) condensates are reported herein. The prototypic design involves a cyclodextrin (CD) platform bearing a polycationic cluster at the primary face and a doubly linked aromatic module bridging two consecutive monosaccharide units at the secondary face that behaves as a topology-encoding element. Subtle differences at the molecular level then translate into disparate morphologies at the nanoscale, including rods, worms, toroids, globules, ellipsoids, and spheroids. In vitro evaluation of the transfection capabilities revealed marked selectivity differences as a function of nanocomplex morphology. Remarkably high transfection efficiencies were associated with ellipsoidal or spherical shapes with a lamellar internal arrangement of pDNA chains and CD bilayers. Computational studies support that the stability of such supramolecular edifices is directly related to the tendency of the molecular vector to form noncovalent dimers upon DNA templating. Because the stability of the dimers depends on the protonation state of the polycationic clusters, the coaggregates display pH responsiveness, which facilitates endosomal escape and timely DNA release, a key step in successful transfection. The results provide a versatile strategy for the construction of fully synthetic and perfectly monodisperse nonviral gene delivery systems uniquely suited for optimization schemes.

Acid-activated nonviral peptide vector for gene delivery.

Nonviral vector-based gene therapy is a promising strategy for treating a myriad of diseases. Cell-penetrating peptides are gaining increasing attention as vectors for nucleic acid delivery. However, most studies have focused more on the transfection efficiency of these vectors than on their specificity and toxicity. To obtain ideal vectors with high efficiency and safety, we constructed the vector stearyl-TH by attaching a stearyl moiety to the N-terminus of the acid-activated cell penetrating peptide TH in this study. Under acidic conditions, stearyl-TH could bind to and condense plasmids into nanoparticle complexes, which displayed significantly enhanced cellular uptake and transfection efficiencies. In contrast, stearyl-TH lost the capacities of DNA binding and transfection at physiological pH. More importantly, stearyl-TH and the complexes formed by stearyl-TH and plasmids displayed no obvious toxicity at physiological pH. Consequently, the high transfection efficiency under acidic conditions and low toxicity make stearyl-TH a potential nucleic acid delivery vector for gene therapy.

Focused Ultrasound Preconditioning for Augmented Nanoparticle Penetration and Efficacy in the Central Nervous System.

Microbubble activation with focused ultrasound (FUS) facilitates the noninvasive and spatially-targeted delivery of systemically administered therapeutics across the blood-brain barrier (BBB). FUS also augments the penetration of nanoscale therapeutics through brain tissue; however, this secondary effect has not been leveraged. Here, 1 MHz FUS sequences that increase the volume of transfected brain tissue after convection-enhanced delivery of gene-vector "brain-penetrating" nanoparticles were first identified. Next, FUS preconditioning is applied prior to trans-BBB nanoparticle delivery, yielding up to a fivefold increase in subsequent transgene expression. Magnetic resonance imaging (MRI) analyses of tissue temperature and Ktrans confirm that augmented transfection occurs through modulation of parenchymal tissue with FUS. FUS preconditioning represents a simple and effective strategy for markedly improving the efficacy of gene vector nanoparticles in the central nervous system.

Mechanisms of unprimed and dexamethasone-primed nonviral gene delivery to human mesenchymal stem cells.

Human mesenchymal stem cells (hMSCs) are under intense study for applications of cell and gene therapeutics because of their unique immunomodulatory and regenerative properties. Safe and efficient genetic modification of hMSCs could increase their clinical potential by allowing functional expression of therapeutic transgenes or control over behavior and differentiation. Viral gene delivery is efficient, but suffers from safety issues, while nonviral methods are safe, but highly inefficient, especially in hMSCs. Our lab previously demonstrated that priming cells before delivery of DNA complexes with dexamethasone (DEX), an anti-inflammatory glucocorticoid drug, significantly increases hMSC transfection success. This work systematically investigates the mechanisms of hMSC transfection and DEX-mediated enhancement of transfection. Our results show that hMSC transfection and its enhancement by DEX are decreased by inhibiting classical intracellular transport and nuclear import pathways, but DEX transfection priming does not increase cellular or nuclear internalization of plasmid DNA (pDNA). We also show that hMSC transgene expression is largely affected by pDNA promoter and enhancer sequence changes, but DEX-mediated enhancement of transfection is unaffected by any pDNA sequence changes. Furthermore, DEX-mediated transfection enhancement is not the result of increased transgene messenger RNA transcription or stability. However, DEX-priming increases total protein synthesis by preventing hMSC apoptosis induced by transfection, resulting in increased translation of transgenic protein. DEX may also promote further enhancement of transgenic reporter enzyme activity by other downstream mechanisms. Mechanistic studies of nonviral gene delivery will inform future rationally designed technologies for safe and efficient genetic modification of clinically relevant cell types.

Differentially Branched Ester Amine Quadpolymers with Amphiphilic and pH-Sensitive Properties for Efficient Plasmid DNA Delivery.

Development of highly effective nonviral gene delivery vectors for transfection of diverse cell populations remains a challenge despite utilization of both rational and combinatorial driven approaches to nanoparticle engineering. In this work, multifunctional polyesters are synthesized with well-defined branching structures via A2 + B2/B3 + C1 Michael addition reactions from small molecule acrylate and amine monomers and then end-capped with amine-containing small molecules to assess the influence of polymer branching structure on transfection. These Branched poly(Ester Amine) Quadpolymers (BEAQs) are highly effective for delivery of plasmid DNA to retinal pigment epithelial cells and demonstrate multiple improvements over previously reported leading linear poly(beta-amino ester)s, particularly for volume-limited applications where improved efficiency is required. BEAQs with moderate degrees of branching are demonstrated to be optimal for delivery under high serum conditions and low nanoparticle doses further relevant for therapeutic gene delivery applications. Defined structural properties of each polymer in the series, including tertiary amine content, correlated with cellular transfection efficacy and viability. Trends that can be applied to the rational design of future generations of biodegradable polymers are elucidated.

Efficient Non-viral Gene Delivery into Human Hematopoietic Stem Cells by Minicircle Sleeping Beauty Transposon Vectors.

The Sleeping Beauty (SB) transposon system is a non-viral gene delivery platform that combines simplicity, inexpensive manufacture, and favorable safety features in the context of human applications. However, efficient correction of hematopoietic stem and progenitor cells (HSPCs) with non-viral vector systems, including SB, demands further refinement of gene delivery techniques. We set out to improve SB gene transfer into hard-to-transfect human CD34+ cells by vectorizing the SB system components in the form of minicircles that are devoid of plasmid backbone sequences and are, therefore, significantly reduced in size. As compared to conventional plasmids, delivery of the SB transposon system as minicircle DNA is ∼20 times more efficient, and it is associated with up to a 50% reduction in cellular toxicity in human CD34+ cells. Moreover, providing the SB transposase in the form of synthetic mRNA enabled us to further increase the efficacy and biosafety of stable gene delivery into hematopoietic progenitors ex vivo. Genome-wide insertion site profiling revealed a close-to-random distribution of SB transposon integrants, which is characteristically different from gammaretroviral and lentiviral integrations in HSPCs. Transplantation of gene-marked CD34+ cells in immunodeficient mice resulted in long-term engraftment and hematopoietic reconstitution, which was most efficient when the SB transposase was supplied as mRNA and nucleofected cells were maintained for 4-8 days in culture before transplantation. Collectively, implementation of minicircle and mRNA technologies allowed us to further refine the SB transposon system in the context of HSPC gene delivery to ultimately meet clinical demands of an efficient and safe non-viral gene therapy protocol.

Current Progress in Electrotransfection as a Nonviral Method for Gene Delivery.

Electrotransfection (ET) is a nonviral method for delivery of various types of molecules into cells both in vitro and in vivo. Close to 90 clinical trials that involve the use of ET have been performed, and approximately half of them are related to cancer treatment. Particularly, ET is an attractive technique for cancer immunogene therapy because treatment of cells with electric pulses alone can induce immune responses to solid tumors, and the responses can be further enhanced by ET of plasmid DNA (pDNA) encoding therapeutic genes. Compared to other gene delivery methods, ET has several unique advantages. It is relatively inexpensive, flexible, and safe in clinical applications, and introduces only naked pDNA into cells without the use of additional chemicals or viruses. However, the efficiency of ET is still low, partly because biological mechanisms of ET in cells remain elusive. In previous studies, it was believed that pDNA entered the cells through transient pores created by electric pulses. As a result, the technique is commonly referred to as electroporation. However, recent discoveries have suggested that endocytosis plays an important role in cellular uptake and intracellular transport of electrotransfected pDNA. This review will discuss current progresses in the study of biological mechanisms underlying ET and future directions of research in this area. Understanding the mechanisms of pDNA transport in cells is critical for the development of new strategies for improving the efficiency of gene delivery in tumors.

Highly compacted biodegradable DNA nanoparticles capable of overcoming the mucus barrier for inhaled lung gene therapy.

Gene therapy has emerged as an alternative for the treatment of diseases refractory to conventional therapeutics. Synthetic nanoparticle-based gene delivery systems offer highly tunable platforms for the delivery of therapeutic genes. However, the inability to achieve sustained, high-level transgene expression in vivo presents a significant hurdle. The respiratory system, although readily accessible, remains a challenging target, as effective gene therapy mandates colloidal stability in physiological fluids and the ability to overcome biological barriers found in the lung. We formulated highly stable DNA nanoparticles based on state-of-the-art biodegradable polymers, poly(ß-amino esters) (PBAEs), possessing a dense corona of polyethylene glycol. We found that these nanoparticles efficiently penetrated the nanoporous and highly adhesive human mucus gel layer that constitutes a primary barrier to reaching the underlying epithelium. We also discovered that these PBAE-based mucus-penetrating DNA nanoparticles (PBAE-MPPs) provided uniform and high-level transgene expression throughout the mouse lungs, superior to several gold standard gene delivery systems. PBAE-MPPs achieved robust transgene expression over at least 4 mo following a single administration, and their transfection efficiency was not attenuated by repeated administrations, underscoring their clinical relevance. Importantly, PBAE-MPPs demonstrated a favorable safety profile with no signs of toxicity following intratracheal administration.

Novel Focused Ultrasound Gene Therapy Approach Noninvasively Restores Dopaminergic Neuron Function in a Rat Parkinson's Disease Model.

Therapies capable of decelerating, or perhaps even halting, neurodegeneration in Parkinson's disease (PD) remain elusive. Clinical trials of PD gene therapy testing the delivery of neurotrophic factors, such as the glial cell-line derived neurotrophic factor (GDNF), have been largely ineffective due to poor vector distribution throughout the diseased regions in the brain. In addition, current delivery strategies involve invasive procedures that obviate the inclusion of early stage patients who are most likely to benefit from GDNF-based gene therapy. Here, we introduce a two-pronged treatment strategy, composed of MR image-guided focused ultrasound (FUS) and brain-penetrating nanoparticles (BPN), that provides widespread but targeted GDNF transgene expression in the brain following systemic administration. MR image-guided FUS allows circulating gene vectors to partition into the brain tissue by noninvasive and transient opening of the blood-brain barrier (BBB) within the areas where FUS is applied. Once beyond the BBB, BPN provide widespread and uniform GDNF expression throughout the targeted brain tissue. After only a single treatment, our strategy led to therapeutically relevant levels of GDNF protein content in the FUS-targeted regions in the striatum of the 6-OHDA-induced rat model of PD, which lasted at least up to 10 weeks. Importantly, our strategy restored both dopamine levels and dopaminergic neuron density and reversed behavioral indicators of PD-associated motor dysfunction with no evidence of local or systemic toxicity. Our combinatorial approach overcomes limitations of current delivery strategies, thereby potentially providing a novel means to treat PD.

Systemic tumor-targeted sodium iodide symporter (NIS) gene therapy of hepatocellular carcinoma mediated by B6 peptide polyplexes.

BACKGROUND: Nonviral polymer-based gene transfer represents an adaptable system for tumor-targeted gene therapy because various design strategies of shuttle systems, together with the mechanistic concept of active tumor targeting, lead to improved gene delivery vectors resulting in higher tumor specificity, efficacy and safety. METHODS: Using the sodium iodide symporter (NIS) as a theranostic gene, nonviral gene delivery vehicles based on linear polyethylenimine (LPEI), polyethylene glycol (PEG) and coupled to the synthetic peptide B6 (LPEI-PEG-B6), which specifically binds to tumor cells, were investigated in a hepatocellular carcinoma xenograft model for tumor selectivity and transduction efficiency. RESULTS: In vitro incubation of three different tumor cell lines with LPEI-PEG-B6/NIS resulted in significant increase in iodide uptake activity compared to untargeted and empty vectors. After establishment of subcutaneous HuH7 tumors, NIS-conjugated nanoparticles were injected intravenously followed by analysis of radioiodide biodistribution using 123 I-scintigraphy showing significant perchlorate-sensitive iodide accumulation in tumors of LPEI-PEG-B6/NIS-treated mice (8.0 ± 1.5% ID/g 123 I; biological half-life of 4 h). After four cycles of repetitive polyplex/131 I applications, a significant delay of tumor growth was observed, which was associated with markedly improved survival in the therapy group. CONCLUSIONS: These results clearly demonstrate that systemic in vivo NIS gene transfer using nanoparticle vectors coupled to B6 tumor targeting ligand is capable of inducing tumor-specific radioiodide uptake. This promising gene therapy approach opens the exciting prospect of NIS-mediated radionuclide therapy in metastatic cancer, together with the possibility of combining several targeting ligands to enhance selective therapeutic efficacy in a broad field of cancer types with various receptor expression profiles.

Biodegradable DNA Nanoparticles that Provide Widespread Gene Delivery in the Brain.

Successful gene therapy of neurological disorders is predicated on achieving widespread and uniform transgene expression throughout the affected disease area in the brain. However, conventional gene vectors preferentially travel through low-resistance perivascular spaces and/or are confined to the administration site even with the aid of a pressure-driven flow provided by convection-enhanced delivery. Biodegradable DNA nanoparticles offer a safe gene delivery platform devoid of adverse effects associated with virus-based or synthetic nonbiodegradable systems. Using a state-of-the-art biodegradable polymer, poly(ß-amino ester), colloidally stable sub-100 nm DNA nanoparticles are engineered with a nonadhesive polyethylene glycol corona that are able to avoid the adhesive and steric hindrances imposed by the extracellular matrix. Following convection enhanced delivery, these brain-penetrating nanoparticles are able to homogeneously distribute throughout the rodent striatum and mediate widespread and high-level transgene expression. These nanoparticles provide a biodegradable DNA nanoparticle platform enabling uniform transgene expression patterns in vivo and hold promise for the treatment of neurological diseases.

Synthesis of linear and cyclic peptide-PEG-lipids for stabilization and targeting of cationic liposome-DNA complexes.

Because nucleic acids (NAs) have immense potential value as therapeutics, the development of safe and effective synthetic NA vectors continues to attract much attention. In vivo applications of NA vectors require stabilized, nanometer-scale particles, but the commonly used approaches of steric stabilization with a polymer coat (e.g., PEGylation; PEG=poly(ethylene glycol)) interfere with attachment to cells, uptake, and endosomal escape. Conjugation of peptides to PEG-lipids can improve cell attachment and uptake for cationic liposome-DNA (CL-DNA) complexes. We present several synthetic approaches to peptide-PEG-lipids and discuss their merits and drawbacks. A lipid-PEG-amine building block served as the common key intermediate in all synthetic routes. Assembling the entire peptide-PEG-lipid by manual solid phase peptide synthesis (employing a lipid-PEG-carboxylic acid) allowed gram-scale synthesis but is mostly applicable to linear peptides connected via their N-terminus. Conjugation via thiol-maleimide or strain-promoted (copper-free) azide-alkyne cycloaddition chemistry is highly amenable to on-demand preparation of peptide-PEG-lipids, and the appropriate PEG-lipid precursors are available in a single chemical step from the lipid-PEG-amine building block. Azide-alkyne cycloaddition is especially suitable for disulfide-bridged peptides such as iRGD (cyclic CRGDKGPDC). Added at 10 mol% of a cationic/neutral lipid mixture, the peptide-PEG-lipids stabilize the size of CL-DNA complexes. They also affect cell attachment and uptake of nanoparticles in a peptide-dependent manner, thereby providing a platform for preparing stabilized, affinity-targeted CL-DNA nanoparticles.

Fluorescent dye incorporation causes weakened gene association and intracellular aggregate formation in nonviral carriers.

BACKGROUND: The successful application of nonviral gene transfer technologies requires both improved understanding and control with respect to intracellular trafficking and release. However, the intracellular space is highly complex and hence well-defined, stable structures are necessary to probe the stages of the delivery pathway. Fluorescent labeling is a regularly used approach to monitor nonviral delivery and release, yet few studies investigate the effects of label incorporation on the structure and activity of gene-containing vehicles. METHODS: In the present study, the impacts of label incorporation on the assembly and gene transfer capacity of DNA polyplexes were determined through the utilization of a model DNA-polyethylenimine (PEI) delivery system. PEI was fluorescently labeled with the Oregon Green® dye prior to polyplex formation and delivery to CHO-K1 cells. RESULTS: The present study provides evidence showing that routine labeling strategies for polyplexes weakened DNA binding affinity, produced large quantities of extracellular structures and significantly increased intracellular polyplex aggregation. Additionally, cellular internalization studies showed that increased labeling fractions led to reductions in polyplex uptake as a result of weakened complexation. CONCLUSIONS: These results not only provide insight into the assembly of these structures, but also help to identify labeling strategies sufficient to preserve activity at the same time as enabling detailed studies of trafficking and disassembly.

Temporal endogenous gene expression profiles in response to polymer-mediated transfection and profile comparison to lipid-mediated transfection.

BACKGROUND: Design of efficient nonviral gene delivery systems is limited by the rudimentary understanding of specific molecules that facilitate transfection. METHODS: Polyplexes using 25-kDa polyethylenimine (PEI) and plasmid-encoding green fluorescent protein (GFP) were delivered to HEK 293T cells. After treating cells with polyplexes, microarrays were used to identify endogenous genes differentially expressed between treated and untreated cells (2 h of exposure) or between flow-separated transfected cells (GFP+) and treated, untransfected cells (GFP-) at 8, 16 and 24 h after lipoplex treatment. Cell priming studies were conducted using pharmacologic agents to alter endogenous levels of the identified differentially expressed genes to determine effect on transfection levels. Differentially expressed genes in polyplex-mediated transfection were compared with those differentially expressed in lipoplex transfection to identify DNA carrier-dependent molecular factors. RESULTS: Differentially expressed genes were RGS1, ARHGAP24, PDZD2, SNX24, GSN and IGF2BP1 after 2 h; RAP1A and ACTA1 after 8 h; RAP1A, WDR78 and ACTA1 after 16 h; and RAP1A, SCG5, ATF3, IREB2 and ACTA1 after 24 h. Pharmacologic studies altering endogenous levels for ARHGAP24, GSN, IGF2BP1, PDZD2 and RGS1 were able to increase or decrease transgene production. Comparing differentially expressed genes for polyplexes and lipoplexes, no common genes were identified at the 2-h time point, whereas, after the 8-h time point, RAP1A, ATF3 and HSPA6 were similarly expressed. SCG5 and PGAP1 were only upregulated in polyplex-transfected cells. CONCLUSIONS: The identified genes and pharmacologic agents provide targets for improving transfection systems, although polyplex or lipoplex dependencies must be considered.

Temporal endogenous gene expression profiles in response to lipid-mediated transfection.

BACKGROUND: Design of efficient nonviral gene delivery systems is limited as a result of the rudimentary understanding of the specific molecules and processes that facilitate DNA transfer. METHODS: Lipoplexes formed with Lipofectamine 2000 (LF2000) and plasmid-encoding green fluorescent protein (GFP) were delivered to the HEK 293T cell line. After treating cells with lipoplexes, HG-U133 Affymetrix microarrays were used to identify endogenous genes differentially expressed between treated and untreated cells (2 h exposure) or between flow-separated transfected cells (GFP+) and treated, untransfected cells (GFP-) at 8, 16 and 24 h after lipoplex treatment. Cell priming studies were conducted using pharmacologic agents to alter endogenous levels of the identified differentially expressed genes to determine effect on transfection levels. RESULTS: Relative to untreated cells 2 h after lipoplex treatment, only downregulated genes were identified ≥ 30-fold: ALMS1, ITGB1, FCGR3A, DOCK10 and ZDDHC13. Subsequently, relative to GFP- cells, the GFP+ cell population showed at least a five-fold upregulation of RAP1A and PACSIN3 (8 h) or HSPA6 and RAP1A (16 and 24 h). Pharmacologic studies altering endogenous levels for ALMS1, FCGR3A, and DOCK10 (involved in filopodia protrusions), ITGB1 (integrin signaling), ZDDHC13 (membrane trafficking) and PACSIN3 (proteolytic shedding of membrane receptors) were able to increase or decrease transgene production. CONCLUSIONS: RAP1A, PACSIN3 and HSPA6 may help lipoplex-treated cells overcome a transcriptional shutdown due to treatment with lipoplexes and provide new targets for investigating molecular mechanisms of transfection or for enhancing transfection through cell priming or engineering of the nonviral gene delivery system.

Importin-4 Regulates Gene Delivery by Enhancing Nuclear Retention and Chromatin Deposition by Polyplexes.

For successful gene delivery, plasmid DNA must be able to access the nucleus in order to be transcribed. Numerous studies have shown that gene delivery occurs more readily in dividing cells, which is attributed to increased nuclear access when the nuclear envelope disassembles during mitosis; however, nonviral carriers continue to have low transfection efficiencies and require large quantities of DNA per cell to achieve reasonable gene transfer, even in dividing cells. Therefore, we hypothesized that using histone-derived nuclear localization sequences (NLS)s to target polyplexes might enhance nuclear delivery by facilitating interactions with histone effectors that mediate nuclear partitioning and retention during mitosis. We discovered a novel interaction between polyplexes linked to histone 3 (H3) N-terminal tail peptides and the histone nuclear import protein importin-4, as evidenced by strong spatial colocalization as well as significantly decreased transfection when importin-4 expression was reduced. A fraction of the histone-targeted polyplexes was also found to colocalize with the retrotranslocon of the endoplasmic reticulum, Sec61. Super resolution microscopy demonstrated a high level of polyplex binding to chromatin postmitosis, and there also was a significant decrease in the amount of chromatin binding following importin-4 knockdown. These results provide evidence that natural histone effectors mediate both nuclear entry and deposition on chromatin by histone-targeted polyplexes, and a translocation event from the endoplasmic reticulum into the cytosol may occur before mitosis to enable the polyplexes to interact with these essential cytoplasmic proteins.

Codelivery of DNA and siRNA via arginine-rich PEI-based polyplexes.

In this study, we formulated polyplexes with different compositions for codelivery of DNA and small-interfering RNA (siRNA). Since DNA and siRNA have distinctive and complementary morphological characteristics (DNA is long and winding and siRNA is short and rigid), we hypothesized that their codelivery using polyplex would enhance each other's transfection. To test this hypothesis, cationic polymer branched polyethylenimine (bPEI) as a standard transfecting agent and its derivative arginine-rich oligopeptide-grafted bPEI modified with polyethylene glycol (P(SiDAAr)5P3), synthesized in our laboratory, were used as carriers for transfection. Polyplexes at different nucleic acid to polymer weight ratios were characterized for transfection in breast cancer sensitive (MCF-7) and resistant (MCF-7/Adr) cell lines. Gene silencing effect of polyplexes was determined in MDA-MB-231-luc-D3H2LN cell line. The results demonstrated that the polyplexes formed with derivative P(SiDAAr)5P3 show significantly lower toxicity compared to polyplexes formed using bPEI. Further, codelivery resulted in 20-fold higher DNA transfection and 2-fold higher siRNA transfection as compared to the respective single nucleotide delivery. DNA transfection was ∼100-fold lower in resistant MCF-7/Adr cells than in sensitive MCF-7 cells. Confocal imaging and flow cytometry data demonstrated that enhanced transfection does not solely depend on DNA's cellular uptake, suggesting that other mechanisms contribute to increased transfection. DNA-co-siRNA delivery could be a promising therapeutic approach to achieve synergistic effects because it can simultaneously target and interfere with multiple regulatory levels in a cell to halt and reverse disease progression.

Structure-Activity Relationship of PEGylated Polylysine Peptides as Scavenger Receptor Inhibitors for Non-Viral Gene Delivery.

PEGylated polylysine peptides of the general structure PEG30 kDa-Cys-Trp-LysN (N = 10 to 30) were used to form fully condensed plasmid DNA (pGL3) polyplexes at a ratio of 1 nmol of peptide per µg of DNA (ranging from N:P 3:1 to 10:1 depending on Lys repeat). Co-administration of 5 to 80 nmols of excess PEG-peptide with fully formed polyplexes inhibited the liver uptake of (125)I-pGL3-polyplexes. The percent inhibition was dependent on the PEG-peptide dose and was saturable, consistent with inhibition of scavenger receptors. The scavenger receptor inhibition potency of PEG-peptides was dependent on the length of the Lys repeat, which increased 10-fold when comparing PEG30 kDa-Cys-Trp-Lys10 (IC50 of 20.2 µM) with PEG30 kDa-Cys-Trp-Lys25 (IC50 of 2.1 µM). We hypothesize that PEG-peptides inhibit scavenger receptors by spontaneously forming small 40 to 60 nm albumin nanoparticles that bind to and saturate the receptor. Scavenger receptor inhibition delayed the metabolism of pGL3-polyplexes, resulting in efficient gene expression in liver hepatocytes following delayed hydrodynamic dosing. PEG-peptides represent a new class of scavenger inhibitors that will likely have broad utility in blocking unwanted liver uptake and metabolism of a variety of nanoparticles.

Nanoplex-Mediated Codelivery of Fibroblast Growth Factor and Bone Morphogenetic Protein Genes Promotes Osteogenesis in Human Adipocyte-Derived Mesenchymal Stem Cells.

This study highlights the importance of transfection mediated coordinated bone morphogenetic protein 2 (BMP-2) and fibroblast growth factor 2 (FGF-2) signaling in promoting osteogenesis. We employed plasmids independently encoding BMP-2 and FGF-2 complexed with polyethylenimine (PEI) to transfect human adipose derived mesenchymal stem cells (hADMSCs) in vitro. The nanoplexes were characterized for size, surface charge, in vitro cytotoxicity, and transfection ability in hADMSCs. A significant enhancement in BMP-2 protein secretion was observed on day 7 post-transfection of hADMSCs with PEI nanoplexes loaded with both pFGF-2 and pBMP-2 (PEI/(pFGF-2+pBMP-2)) versus transfection with PEI nanoplexes of either pFGF-2 alone or pBMP-2 alone. Osteogenic differentiation of transfected hADMSCs was determined by measuring osteocalcin and Runx-2 gene expression using real time polymerase chain reactions. A significant increase in the expression of Runx-2 and osteocalcin was observed on day 3 and day 7 post-transfection, respectively, by cells transfected with PEI/(pFGF-2+pBMP-2) compared to cells transfected with nanoplexes containing pFGF-2 or pBMP-2 alone. Alizarin Red staining and atomic absorption spectroscopy revealed elevated levels of calcium deposition in hADMSC cultures on day 14 and day 30 post-transfection with PEI/(pFGF-2+pBMP-2) compared to other treatments. We have shown that codelivery of pFGF-2 and pBMP-2 results in a significant enhancement in osteogenic protein synthesis, osteogenic marker expression, and subsequent mineralization. This research points to a new clinically translatable strategy for achieving efficient bone regeneration.