Linear PEI nanoparticles: efficient pDNA/siRNA carriers in vitro and in vivo

Efficient and scalable gene delivery method with easily generated cationic carbon dots

Gene delivery is a complex process with several challenges when attempting to incorporate genetic material efficiently and safely into target cells. Some of the key challenges include not only efficient cellular uptake and endosomal escape to ensure that the genetic material can exert its effect but also minimizing the toxicity of the delivery system, which is vital for safe gene delivery. Of importance, if gene delivery systems are intended for biomedical applications or clinical use, they must be scalable and easy and affordable to manufacture to meet the demand. Here, we show an efficient gene delivery method using a combination of carbon dots coated by PEI through electrostatic binding to easily generate cationic carbon dots. We show a biofunctional approach to generate optimal cationic carbon dots (CCDs) that can be scaled up to meet specific transfection demands. CCDs improve cell viability and increase transfection efficiency four times over the standard of PEI polyplexes. Generated CCDs enabled the challenging transfection protocol to produce retroviral vectors via cell cotransfection of three different plasmids into packing cells, showing not only high efficiency but also functionality of the gene delivery, tested as the capacity to produce infective retroviral particles.

Cationic amino-acid functionalized polymethacrylamide vectors for siRNA transfection based on modification of poly(2-isopropenyl-2-oxazoline)

Poly(2-isopropenyl-2-oxazoline) (PiPOx) is a functional polymer showing great potential for the development of smart biomaterials. The straightforward synthesis and post-polymerization functionalization of PiPOx offers many opportunities for tailoring the properties of the polymer towards biomaterials. In this study we report for the first time PiPOx-based cationic charged polymethacrylamides with amino acid side chains that can complex siRNA and promote transfection in vitro. Therefore, PiPOx was fully modified via ring opening addition reactions with the carboxylic acid groups of a series of N-Boc-L-amino acids and their reaction kinetics were investigated. Based on the determined kinetic constants, another series of PiPOx-based copolymers with balanced hydrophilic/hydrophobic content of N-Boc-L-amino acids were obtained via one-pot modification reaction with two different N-Boc-L-amino acids. The N-Boc protected homopolymers and related copolymers were deprotected to obtain (co)polymers with the targeted side chain cationic charged units. The (co)polymers' structures were fully investigated via FT-IR and 1H NMR spectroscopy, size exclusion chromatography (SEC), and TGA-DSC-MS analysis. The polarimetry measurements revealed that the homopolymers retain their chiroptical properties after post-modification, and a sign inversion is noticed from (L) N-Boc-protected analogues to (D) for the TFA cationic charged homopolymers. Generally, cationically charged homopolymers with hydrophilic amino acids on the side chain showed efficient complexation of siRNA, but poor transfection while cationic copolymers having both tryptophan and valine or proline side chains revealed moderate siRNA binding, high transfection efficiency (> 90% of the cells) and potent gene silencing with IC50 values down to 5.5 nM. Particularly, these cationic copolymers showed higher gene silencing potency as compared to the commercial JetPRIME® reference, without reducing cell viability in the concentration range used for transfection, making this a very interesting system for in vitro siRNA transfection.

Highly Selective Fluorescent Sensors: Polyethylenimine Derivatives of Triphenylamine and Coumarin for GTP and ATP Interaction via Fluorescence Lifetime Imaging Microscopy

Chemical derivatives of polyethylenimine (PEI) receptors with either triphenylamine (TPA) or 7-hydroxy-4-methyl-coumarin (Cou) form stable complexes with adenine and guanine nucleotides in water. The host-guest complex modulation is found to be based on noncovalent molecular interactions such as π-π stacking and hydrogen bonding, which are dependent on the aromatic moieties attached to the polyaminic (PEI) backbone. PEI-TPA acts as a chemosensor with a recognition driving force based on aggregation-induced emission (AIE), involving π-π interaction between the nucleic base and TPA. It detects GTP by a chelation enhancement quenching effect of fluorescence (CHEQ) with a measured logarithm stability constant, log β = 7.7. By varying the chemical characteristics of the fluorophore, as in the PEI-Cou system, the driving force for recognition changes from a π-π interaction to an electrostatic interaction. The coumarin derivative detects ATP with a log β value one order of magnitude higher than that for GTP, allowing for the selective recognition of the two nucleotides in a 100% aqueous solution. Furthermore, fluorescence lifetime imaging microscopy (FLIM) allows for a correlation between the selectivity of PEI-TPA toward nucleotides and the morphology of the structures formed upon ATP and GTP recognition. This study offers valuable insights into the design of receptors for the selective recognition of nucleotides in water.

Transfection Efficacy and Cellular Uptake of Lipid-Modified Polyethyleneimine Derivatives for Anionic Nanoparticles as Gene Delivery Vectors

Cationic polyethylenimine (PEI)-based nonviral gene carriers have been desirable to overcome the limitations of viral vectors in gene therapy. A range of PEI derivatives were designed, synthesized, and evaluated for nonviral delivery applications of plasmid DNA (pDNA). Linolenic acid, lauric acid, and oleic acid were covalently conjugated with low-molecular-weight PEI (M_w ∼ 1200 Da) via two different linkers, gallic acid (GA) and p-hydroxybenzoic acid (PHPA), that allows a differential loading of lipids per modified amine (3 vs 1, respectively). ¹H NMR spectrum confirmed the expected structure of the conjugates as well as the level of lipid substitution. SYBR Green binding assay performed to investigate the 50% binding concentration (BC₅₀) of lipophilic polymers to pDNA revealed increased BC₅₀ with an increased level of lipid substitution. The particle analysis determined that GA- and PHPA-modified lipopolymers gave pDNA complexes with ∼300 and ∼100 nm in size, respectively. At the polymer/pDNA ratio of 5.0, the ζ-potentials of the complexes were negative (-6.55 to -10.6 mV) unlike the complexes with the native PEI (+11.2 mV). The transfection experiments indicated that the prepared lipopolymers showed higher transfection in attachment-dependent cells than in suspension cells based on the expression of the reporter green fluorescent protein (GFP) gene. When loaded with Cy3-labeled pDNA, the lipopolymers exhibited effective cellular uptake in attachment-dependent cells while the cellular uptake was limited in suspension cells. These results demonstrate the potential of lipid-conjugated PEI via GA and PHPA linkers, which are promising for the modification of anchorage-dependent cells.

Therapeutic Delivery of Tumor Suppressor miRNAs for Breast Cancer Treatment

The death rate from breast cancer (BC) has dropped due to early detection and sophisticated therapeutic options, yet drug resistance and relapse remain barriers to effective, systematic treatment. Multiple mechanisms underlying miRNAs appear crucial in practically every aspect of cancer progression, including carcinogenesis, metastasis, and drug resistance, as evidenced by the elucidation of drug resistance. Non-coding RNAs called microRNAs (miRNAs) attach to complementary messenger RNAs and degrade them to inhibit the expression and translation to proteins. Evidence suggests that miRNAs play a vital role in developing numerous diseases, including cancer. They affect genes critical for cellular differentiation, proliferation, apoptosis, and metabolism. Recently studies have demonstrated that miRNAs serve as valuable biomarkers for BC. The contrast in the expression of miRNAs in normal tissue cells and tumors suggest that miRNAs are involved in breast cancer. The important aspect behind cancer etiology is the deregulation of miRNAs that can specifically influence cellular physiology. The main objective of this review is to emphasize the role and therapeutic capacity of tumor suppressor miRNAs in BC and the advancement in the delivery system that can deliver miRNAs specifically to cancerous cells. Various approaches are used to deliver these miRNAs to the cancer cells with the help of carrier molecules, like nanoparticles, poly D, L-lactic-co-glycolic acid (PLGA) particles, PEI polymers, modified extracellular vesicles, dendrimers, and liposomes. Additionally, we discuss advanced strategies of TS miRNA delivery techniques such as viral delivery, self-assembled RNA-triple-helix hydrogel drug delivery systems, and hyaluronic acid/protamine sulfate inter-polyelectrolyte complexes. Subsequently, we discuss challenges and prospects on TS miRNA therapeutic delivery in BC management so that miRNAs will become a routine technique in developing individualized patient profiles.

Polymer Nanoparticles Enhance Irreversible Electroporation In Vitro

Expanding the volume of an irreversible electroporation treatment typically necessitates an increase in pulse voltage, number, duration, or repetition. This study investigates the addition of polyethylenimine nanoparticles (PEI-NP) to pulsed electric field treatments, determining their combined effect on ablation size and voltages. U118 cells in an in vitro 3D cell culture model were treated with one of three pulse parameters (with and without PEI-NPs) which are representative of irreversible electroporation (IRE), high frequency irreversible electroporation (H-FIRE), or nanosecond pulsed electric fields (nsPEF). The size of the ablations were compared and mapped onto an electric field model to describe the electric field required to induce cell death. Analysis was conducted to determine the role of PEI-NPs in altering media conductivity, the potential for PEI-NP degradation following pulsed electric field treatment, and PEI-NP uptake. Results show there was a statistically significant increase in ablation diameter for IRE and H-FIRE pulses with PEI-NPs. There was no increase in ablation size for nsPEF with PEI-NPs. This all occurs with no change in cell media conductivity, no observable degradation of PEI-NPs, and moderate particle uptake. These results demonstrate the synergy of a combined cationic polymer nanoparticle and pulsed electric field treatment for the ablation of cancer cells. These results set the foundation for polymer nanoparticles engineered specifically for irreversible electroporation.

Critical Evaluation of Different Lysosomal Labeling Methods Used to Analyze RNA Nanocarrier Trafficking in Cells

The use of nucleic acids to regulate gene expression is a rapidly developing field with immense clinical potential. Nanomaterials are frequently used to deliver nucleic acids into cells as they can overcome the poor cellular uptake and endo/lysosomal degradation of bare nucleic acids. For these nanocarriers to be effective, they must escape endo/lysosomal compartments to deliver their nucleic acid cargo into the cytosol (for ribonucleic acid (RNA)) or nucleus (for deoxyribonucleic acid (DNA)). This process is poorly understood and remains an area of active research toward the goal of developing effective delivery strategies. Fluorescent endo/lysosomal markers are among the most widely employed tools used to evaluate the endosomal escape of nucleic acid nanocarriers. However, the endo/lysosomal labeling method may alter the extent of and route of nanocarrier uptake by cells. The impact of these markers on cellular function and cell-nanocarrier interactions has not been probed in a systematic manner. To investigate this, we compared the effects of several common lysosomal labeling methods, namely, LysoTracker Red (LT Red), transient lysosomal-associated membrane protein 1-mutant green fluorescent protein (LAMP1-mGFP) transfection (Transient GFP), and stable lentiviral LAMP1-mGFP transfection (Stable GFP), on cellular metabolic activity, nanocarrier uptake, nanocarrier/lysosomal label colocalization, and gene silencing potency in U87 glioblastoma and MDA-MB-231 breast cancer cells using polyethyleneimine (PEI)/ribonucleic acid (RNA) polyplexes as a model nanocarrier. In both U87s and MDA-MB-231s, Transient GFP and LT Red labeling reduced metabolic activity relative to untransfected (Parental) cells, while Stable GFP labeling increased metabolic activity. Congruently, flow cytometry indicates Stable GFP cells have greater polyplex uptake than LT Red-labeled cells in both cell lines. Despite these similar trends in uptake, polyplex intracellular trafficking differs in the two cell lines, as confocal imaging revealed greater polyplex/lysosome colocalization in Stable GFP U87 cells than LT Red-labeled U87 cells, while the trend was reversed in MBA-MB-231s. The level of RNA-mediated gene silencing achieved in Parental versus Stable GFP U87 and MDA-MB-231 cells agreed with the observed levels of polyplex/lysosome colocalization, supporting the established concept that endosomal escape is the rate-limiting step for RNA interference. These findings indicate that lysosomal labels can profoundly alter cellular function and cell-nanocarrier interactions, presenting critical new considerations for researchers investigating nanoparticle trafficking.

Osteoporosis Remission and New Bone Formation with Mesoporous Silica Nanoparticles

Nanotechnology changed the concept of treatment for a variety of diseases, producing a huge impact regarding drug and gene delivery. Among the different targeted diseases, osteoporosis has devastating clinical and economic consequences. Since current osteoporosis treatments present several side effects, new treatment approaches are needed. Recently, the application of small interfering RNA (siRNA) has become a promising alternative. Wnt/β-catenin signaling pathway controls bone development and formation. This pathway is negatively regulated by sclerostin, which knock-down through siRNA application would potentially promote bone formation. However, the major bottleneck for siRNA-based treatments is the necessity of a delivery vector, bringing nanotechnology as a potential solution. Among the available nanocarriers, mesoporous silica nanoparticles (MSNs) have attracted great attention for intracellular delivery of siRNAs. The mesoporous structure of MSNs permits the delivery of siRNAs together with another biomolecule, achieving a combination therapy. Here, the effectiveness of a new potential osteoporosis treatment based on MSNs is evaluated. The proposed system is effective in delivering SOST siRNA and osteostatin through systemic injection to bone tissue. The nanoparticle administration produced an increase expression of osteogenic related genes improving the bone microarchitecture. The treated osteoporotic mice recovered values of a healthy situation approaching to osteoporosis remission.

Effects of Decomplexation Rates on Ternary Gene Complex Transfection with α-Poly(l-Lysine) or ε-Poly(l-Lysine) as a Decomplexation Controller in An Easy-To-Transfect Cell or A Hard-To-Transfect Cell

The tight binding of pDNA with a cationic polymer is the crucial requirement that prevents DNA degradation from undesired DNase attack to safely deliver the pDNA to its target site. However, cationic polymer-mediated strong gene holding limits pDNA dissociation from the gene complex, resulting in a reduction in transfection efficiency. In this study, to control the decomplexation rate of pDNA from the gene complex in a hard-to-transfect cell or an easy-to-transfect cell, either α-poly(l-lysine) (APL) or ε-poly(l-lysine) (EPL) was incorporated into branched polyethylenimine (bPEI)-based nanocomplexes (NCs). Compared to bPEI/pDNA NCs, the addition of APL or EPL formed smaller bPEI-APL/pDNA NCs with similar zeta potentials or larger bPEI-EPL/pDNA NCs with reduced zeta potentials, respectively, due to the different characteristics of the primary amines in the two poly(l-lysine)s (PLs). Interestingly, although both bPEI-APL/pDNA NCs and bPEI-EPL/pDNA NCs showed similar pDNA compactness to bPEI/pDNA NCs, the addition of APL or EPL resulted in slower or faster pDNA release, respectively, from the bPEI-PL/pDNA NCs than from the bPEI/pDNA NCs. bPEI-EPL/pDNA NCs with a decomplexation enhancer (i.e., EPL) improved the transfection efficiency (TE) in both a hard-to-transfect HepG2 cell and an easy-to-transfect HEK293 cell. However, although a decomplexation inhibitor (i.e., APL) reduced the TE of bPEI-APL/pDNA NCs in both cells, the degree of reduction in the TE could be compensated by PL-mediated enhanced nuclear delivery, particularly in HepG2 cells but not HEK293 cells, because both PLs facilitate nuclear localization of the gene complex per its cellular uptake. In conclusion, a decomplexation rate controller could be a potential factor to establish a high TE and design clinically available gene complex systems.

Nanoparticles to Knockdown Osteoporosis-Related Gene and Promote Osteogenic Marker Expression for Osteoporosis Treatment

Osteoporosis is the most common disease involving bone degeneration. Current clinical treatments are not able to offer a satisfying curative effect, so the development of effective treatments is desired. Gene silencing through siRNA delivery has gained great attention as a potential treatment in bone diseases. SOST gene inhibits the Wnt signaling pathway reducing osteoblast differentiation. Consequently, silencing SOST genes with a specific siRNA could be a potential option to treat osteoporosis. Generally, siRNAs have a very short half-life and poor transfection capacity, so an effective carrier is needed. In particular, mesoporous silica nanoparticles (MSNs) have attracted great attention for intracellular delivery of nucleic acids. We took advantage of their high loading capacity to further load the pores with osteostatin, an osteogenic peptide. In this study, we developed a system based on MSNs coated with poly(ethylenimine), which can effectively deliver SOST siRNA and osteostatin inside cells, with the consequent augmentation of osteogenic markers with a synergistic effect. This established the potential utility of MSNs to co-deliver both biomolecules to promote bone formation, this being a potential alternative to treat osteoporosis.

Layer-by-layer assembled gold nanoshells for the intracellular delivery of miR-34a

INTRODUCTION

MicroRNAs (miRNAs) are short noncoding RNAs whose ability to regulate the expression of multiple genes makes them potentially exciting tools to treat disease. Unfortunately, miRNAs cannot passively enter cells due to their hydrophilicity and negative charge. Here, we report the development of layer-by-layer assembled nanoshells (LbL-NS) as vehicles for efficient intracellular miRNA delivery. Specifically, we developed LbL-NS to deliver the tumor suppressor miR-34a into triple-negative breast cancer (TNBC) cells, and demonstrate that these constructs can safely and effectively regulate the expression of SIRT1 and Bcl-2, two known targets of miR-34a, to decrease cell proliferation.

METHODS

LbL-NS were made by coating negatively charged nanoshells with alternating layers of positive poly-L-lysine (PLL) and negative miRNA, with the outer layer consisting of PLL to facilitate cellular entry and protect the miRNA. Electron microscopy, spectrophotometry, dynamic light scattering, and miRNA release studies were used to characterize LbL-NS. The particles' ability to enter MDA-MB-231 TNBC cells, inhibit SIRT1 and Bcl-2 expression, and thereby reduce cell proliferation was examined by confocal microscopy, Western blotting, and EdU assays, respectively.

RESULTS

Each successive coating reversed the nanoparticles' charge and increased their hydrodynamic diameter, resulting in a final diameter of 208±4 nm and a zeta potential of 53±5 mV. The LbL-NS released ~30% of their miR-34a cargo over 5 days in 1X PBS. Excitingly, LbL-NS carrying miR-34a suppressed SIRT1 and Bcl-2 by 46±3% and 35±3%, respectively, and decreased cell proliferation by 33%. LbL-NS carrying scrambled miRNA did not yield these effects.

CONCLUSION

LbL-NS can efficiently deliver miR-34a to TNBC cells to suppress cancer cell growth, warranting their further investigation as tools for miRNA replacement therapy.

Probing Cellular Processes Using Engineered Nanoparticles

Nanoparticles, the building blocks of nanotechnology, have been widely utilized in various biomedical applications, such as detection, diagnosis, imaging, and therapy. However, another emerging, albeit under-represented, area is the employment of nanoparticles as tools to understand cellular processes (e.g., oxidative stress-induced signaling cascades). Such investigations have enormous potential to characterize a disease from a different perspective and unravel some new features that otherwise would have remained a mystery. In this review, we summarize the intrinsic biological properties of unmodified as well surface modified nanoparticles and discuss how such properties could be utilized to interrogate biological processes and provide a perspective for future evolution of this field.

Synthesis and characterization of bioreducible cationic biarm polymer for efficient gene delivery

We synthesized a new cationic AB₂ miktoarm block copolymer consisting of one poly (ethylene glycol) (PEG) block and two cationic poly (l-lysine) (PLL) blocks, wherein the PLL blocks were conjugated to the PEG blocks with or without a bioreducible linker (disulfide bonds). Bioreducible and non-bioreducible miktoarm block copolymers (mPEG-(ss-PLL)₂ and mPEG-PLL₂) were prepared for efficient gene delivery as a non-viral gene delivery approach. Both cationic copolymers (bioreducible and nonbioreducible) efficiently formed the nanopolyplexes with plasmid DNA (pDNA) through electrostatic interaction at different weight ratio of polymer and pDNA. Gene condensation ability of the polymers and release of the DNA under reduction condition were measured by gel electrophoresis. Dynamic light scattering (DLS) and field-emission transmission electron microscopy (FE-TEM) were used to measure the average hydrodynamic diameter and morphology of the nanoparticles, respectively. The bioreducible nanopolyplexes showed lower cytotoxicity and higher gene expression than the non-reducible nanopolyplexes in cancer cells.

Hydroxyethyl substituted linear polyethylenimine for safe and efficient delivery of siRNA therapeutics

Linear polyethylenimine (LPEI) has been well reported as a carrier for siRNA delivery. However, its applications are limited due to its highly ionized state at physiologic pH and the resultant charge mediated toxicity. The presence of ionizable secondary amines in LPE are responsible for its unique characteristics such as pH dependent solubility and positive charge. Therefore, modification of LPEI was carried out to obtain hydroxyethyl substituted LPEI with the degree of substitution ranging from 15% to 45%. The impact of modification on the physicochemical parameters of the polymer, i.e. buffer capacity, solubility, biocompatibility and stability, was evaluated. Surprisingly, despite the loss of ionizable amines, the substitution improved solubility, and even overcame the pH dependent solubility of LPEI. In addition, the conversion of secondary amines to less basic tertiary amines after substitution improved the buffer capacity, in the endosomal pH range, required for efficient endosomal escape. It also reduced erythrocyte aggregation, hemolytic potential and in vitro cytotoxicity. The in vitro studies showed enhanced cell uptake and mRNA knockdown efficiency. Thus, the proposed modification shows a simple approach to overcome the limitation of LPEI for siRNA delivery.

Hydroxyethyl substitution of linear polyethylenimine (LPEI) and its effects on physico-chemical and biological properties of polymer.

Systemic delivery of siRNA by T7 peptide modified core-shell nanoparticles for targeted therapy of breast cancer

Systemic delivery of siRNA is the most challenging step to transfer RNAi to clinical application for breast cancer therapy. In this study, the tumor targeted, T7 peptide modified core-shell nanoparticles (named as T7-LPC/siRNA NPs) were constructed to achieve effective systemic delivery of siRNA. The core-shell structure of T7-LPC/siRNA NPs enables them to encapsulate siRNA in the core and protect it from RNase degradation during circulation. In vitro cellular uptake and gene silencing experiments demonstrated that T7-LPC/siEGFR NPs could deliver EGFR siRNA into breast cancer cells through receptor mediated endocytosis and effectively down-regulate the EGFR expression. In vivo distribution study proved the T7-LPC/siRNA NPs could deliver fluorescence labeled siRNA to the tumor site more efficiently than the non-targeted PEG-LPC/siRNA NPs after intravenous administration. Furthermore, the experiments of in vivo tumor therapy confirmed that intravenous administration of T7-LPC/siEGFR NPs led to an effective EGFR down-regulation and an obvious inhibition of breast tumor growth, with little activation of immune responses and negligible body weight loss. These results suggested that T7-LPC/siRNA NPs could be an effective and safe systemic siRNA delivery system for RNAi-based breast cancer therapy.

Prenyl Ammonium Salts--New Carriers for Gene Delivery: A B16-F10 Mouse Melanoma Model

PURPOSE

Prenyl ammonium iodides (Amino-Prenols, APs), semi-synthetic polyprenol derivatives were studied as prospective novel gene transfer agents.

METHODS

AP-7, -8, -11 and -15 (aminoprenols composed of 7, 8, 11 or 15 isoprene units, respectively) were examined for their capacity to form complexes with pDNA, for cytotoxicity and ability to transfect genes to cells.

RESULTS

All the carriers were able to complex DNA. The highest, comparable to commercial reagents, transfection efficiency was observed for AP-15. Simultaneously, AP-15 exhibited the lowest negative impact on cell viability and proliferation--considerably lower than that of commercial agents. AP-15/DOPE complexes were also efficient to introduce pDNA to cells, without much effect on cell viability. Transfection with AP-15/DOPE complexes influenced the expression of a very few among 44 tested genes involved in cellular lipid metabolism. Furthermore, complexes containing AP-15 and therapeutic plasmid, encoding the TIMP metallopeptidase inhibitor 2 (TIMP2), introduced the TIMP2 gene with high efficiency to B16-F10 melanoma cells but not to B16-F10 melanoma tumors in C57BL/6 mice, as confirmed by TIMP2 protein level determination.

CONCLUSION

Obtained results indicate that APs have a potential as non-viral vectors for cell transfection.

Synthesis, characterization and evaluation of diglycidyl-1,2-cyclohexanedicarboxylate crosslinked polyethylenimine nanoparticles as efficient carriers of DNA

Crosslinked PEI nanoparticles were synthesized, which efficiently transported DNA inside the cells with minimal cytotoxicity.

Screening PEGylated polyethylenimine derivatives for safe and efficient delivery of gene materials

PEG–Et 1 : 1 was screened out for the safe and efficient gene delivery by precise design of PEGylated polymeric nanomaterials.

Immunogenicity and Protective Efficacy of Brugia malayi Heavy Chain Myosin as Homologous DNA, Protein and Heterologous DNA/Protein Prime Boost Vaccine in Rodent Model

We earlier demonstrated the immunoprophylactic efficacy of recombinant heavy chain myosin (Bm-Myo) of Brugia malayi (B. malayi) in rodent models. In the current study, further attempts have been made to improve this efficacy by employing alternate approaches such as homologous DNA (pcD-Myo) and heterologous DNA/protein prime boost (pcD-Myo+Bm-Myo) in BALB/c mouse model. The gene bm-myo was cloned in a mammalian expression vector pcDNA 3.1(+) and protein expression was confirmed in mammalian Vero cell line. A significant degree of protection (79.2%±2.32) against L3 challenge in pcD-Myo+Bm-Myo immunized group was observed which was much higher than that exerted by Bm-Myo (66.6%±2.23) and pcD-Myo (41.6%±2.45). In the heterologous immunized group, the percentage of peritoneal leukocytes such as macrophages, neutrophils, B cells and T cells marginally increased and their population augmented further significantly following L3 challenge. pcD-Myo+Bm-Myo immunization elicited robust cellular and humoral immune responses as compared to pcD-Myo and Bm-Myo groups as evidenced by an increased accumulation of CD4+, CD8+ T cells and CD19+ B cells in the mouse spleen and activation of peritoneal macrophages. Though immunized animals produced antigen-specific IgG antibodies and isotypes, sera of mice receiving pcD-Myo+Bm-Myo or Bm-Myo developed much higher antibody levels than other groups and there was profound antibody-dependent cellular adhesion and cytotoxicity (ADCC) to B. malayi infective larvae (L3). pcD-Myo+Bm-Myo as well as Bm-Myo mice generated a mixed T helper cell phenotype as evidenced by the production of both pro-inflammatory (IL-2, IFN-γ) and anti-inflammatory (IL-4, IL-10) cytokines. Mice receiving pcD-Myo on contrary displayed a polarized pro-inflammatory immune response. The findings suggest that the priming of animals with DNA followed by protein booster generates heightened and mixed pro- and anti-inflammatory immune responses that are capable of providing high degree of protection against filarial larval invasion.

Osteogenic evaluation of collagen membrane containing drug-loaded polymeric microparticles in a rat calvarial defect model

The aim of this study was to develop a functional collagen membrane that is treated with poly (lactic-co-glycolic acid) (PLGA) nanoparticles loaded with dexamethasone (DEX) as a bioactive molecule for guided bone regeneration (GBR). The DEX-loaded PLGA microparticles prepared using water-in-oil standard emulsion method were precoated with positively charged polyethylenimine molecules and later immobilized onto the surface of the collagen membrane; the microparticles were physically immobilized using counter charges of positively charged PLGA microparticles and the negatively charged collagen membrane surface. The release profile of DEX over a 4-week immersion study indicated an initial burst release followed by a sustained release. The performance of this system was investigated using rats with calvarial bone defects. The in vivo evaluation of the defects filled with membrane containing DEX-loaded PLGA microparticles indicated enhanced volume and quality of new bone formation compared with defects that were either unfilled or filled with membrane alone. This innovative platform for bioactive molecule delivery more potently induced osteogenesis, which may be exploited in implantable membranes for stem cell therapy or improved in vivo performance. In conclusion, this newly developed collagen membrane treated with drug-loaded PLGA microparticles might be applicable as a promising bone graft substitute for GBR.

A chitosan-graft-PEI-candesartan conjugate for targeted co-delivery of drug and gene in anti-angiogenesis cancer therapy

A multifunctional copolymer-anticancer conjugate chitosan-graft-polyethyleneimine-candesartan (CPC) containing low molecular weight chitosan (CS) backbone and polyethyleneimine (PEI) arms with candesartan (CD) conjugated via an amide bond was fabricated as a targeted co-delivery nanovector of drug and gene for potential cancer therapy. Here, CD was utilized to specifically bind to overexpressed angiotensin II type 1 receptor (AT1R) of tumor cells, strengthen endosomal buffering capacity of CPC and suppress tumor angiogenesis. The self-assembled CPC/pDNA complexes exhibited desirable and homogenous particle size, moderate positive charges, superior stability, and efficient release of drug and gene in vitro. Flow cytometry and confocal laser scanning microscopy analyses confirmed that CD-targeted function and CD-enhanced buffering capacity induced high transfection, specific cellular uptake and efficient intracellular delivery of CPC/pDNA complexes in AT1R-overexpressed PANC-1 cells. In addition, CPC/wt-p53 complexes co-delivering CD and wild type p53 (wt-p53) gene achieved synergistic angiogenesis suppression by more effectively downregulating the expression of vascular endothelial growth factor (VEGF) mRNA and protein via different pathways in vitro, as compared to mono-delivery and mixed-delivery systems. In vivo investigation on nude mice bearing PANC-1 tumor xenografts revealed that CPC/wt-p53 complexes possessed high tumor-targeting capacity and strong anti-tumor activity. Additional analysis of microvessel density (MVD) demonstrated that CPC/wt-p53 complexes significantly inhibited tumor-associated angiogenesis. These findings suggested that CPC could be an ideal tumor-targeting nanovector for simultaneous transfer of drug and gene, and a multifunctional CPC/wt-p53 co-delivery system with tumor-specific targetability, enhanced endosomal buffering capacity and synergistic anti-angiogenesis efficacy might be a new promising strategy for effective tumor therapy.

O-hexadecyl-dextran entrapped berberine nanoparticles abrogate high glucose stress induced apoptosis in primary rat hepatocytes

Nanotized phytochemicals are being explored by researchers for promoting their uptake and effectiveness at lower concentrations. In this study, O-hexadecyl-dextran entrapped berberine chloride nanoparticles (BC-HDD NPs) were prepared, and evaluated for their cytoprotective efficacy in high glucose stressed primary hepatocytes and the results obtained compared with bulk berberine chloride (BBR) treatment. The nanotized formulation treated primary hepatocytes that were exposed to high glucose (40 mM), showed increased viability compared to the bulk BBR treated cells. BC-HDD NPs reduced the ROS generation by ∼ 3.5 fold during co-treatment, prevented GSH depletion by ∼ 1.6 fold, reduced NO formation by ∼ 5 fold and significantly prevented decline in SOD activity in stressed cells. Lipid peroxidation was also prevented by ∼ 1.9 fold in the presence of these NPs confirming the antioxidant capacity of the formulation. High glucose stress increased Bax/Bcl2 ratio followed by mitochondrial depolarization and activation of caspase-9/-3 confirming involvement of mitochondrial pathway of apoptosis in the exposed cells. Co- and post-treatment of BC-HDD NPs prevented depolarization of mitochondrial membrane, reduced Bax/Bcl2 ratio and prevented externalization of phosphatidyl-serine confirming their anti-apoptotic capacity in those cells. Sub-G1 phase apparent in high glucose stressed cells was not seen in BC-HDD NPs treated cells. The present study reveals that BC-HDD NPs at ∼ 20 fold lower concentration are as effective as BBR in preventing high glucose induced oxidative stress, mitochondrial depolarization and downstream events of apoptotic cell death.

Vaccination of mice using the West Nile virus E-protein in a DNA prime-protein boost strategy stimulates cell-mediated immunity and protects mice against a lethal challenge

West Nile virus (WNV) is a mosquito-borne flavivirus that is endemic in Africa, the Middle East, Europe and the United States. There is currently no antiviral treatment or human vaccine available to treat or prevent WNV infection. DNA plasmid-based vaccines represent a new approach for controlling infectious diseases. In rodents, DNA vaccines have been shown to induce B cell and cytotoxic T cell responses and protect against a wide range of infections. In this study, we formulated a plasmid DNA vector expressing the ectodomain of the E-protein of WNV into nanoparticles by using linear polyethyleneimine (lPEI) covalently bound to mannose and examined the potential of this vaccine to protect against lethal WNV infection in mice. Mice were immunized twice (prime – boost regime) with the WNV DNA vaccine formulated with lPEI-mannose using different administration routes (intramuscular, intradermal and topical). In parallel a heterologous boost with purified recombinant WNV envelope (E) protein was evaluated. While no significant E-protein specific humoral response was generated after DNA immunization, protein boosting of DNA-primed mice resulted in a marked increase in total neutralizing antibody titer. In addition, E-specific IL-4 T-cell immune responses were detected by ELISPOT after protein boost and CD8⁺ specific IFN-γ expression was observed by flow cytometry. Challenge experiments using the heterologous immunization regime revealed protective immunity to homologous and virulent WNV infection.

Gene silencing in human aortic smooth muscle cells induced by PEI-siRNA complexes released from dip-coated electrospun poly(ethylene terephthalate) grafts

An excessive tissue response to prosthetic arterial graft material leads to intimal hyperplasia (IH), the leading cause of late graft failure. Seroma and abnormal capsule formation may also occur after prosthetic material implantation. The matricellular protein Thrombospondin-2 (TSP-2) has shown to be upregulated in response to biomaterial implantation. This study evaluates the uptake and release of small interfering RNA (siRNA) from unmodified and surface functionalized electrospun PET graft materials. ePET graft materials were synthesized using electrospinning technology. Subsets of the ePET materials were then chemically modified to create surface functional groups. Unmodified and surface-modified ePET grafts were dip-coated in siRNAs alone or siRNAs complexed with transfection reagents polyethyleneimine (PEI) or Lipofectamine RNAiMax. Further, control and TSP-2 siRNA-PEI complex treated ePET samples were placed onto a confluent layer of human aortic smooth muscle cells (AoSMCs). Complexation of all siRNAs with PEI led to a significant increase in adsorption to unmodified ePET. TSP-2 siRNA-PEI released from unmodified-ePET silenced TSP-2 in AoSMC. Regardless of the siRNA-PEI complex evaluated, AoSMC migrated into the ePET. siRNA-PEI complexes delivered to AoSMC from dip-coated ePET can result in gene knockdown. This methodology for siRNA delivery may improve the tissue response to vascular and other prosthetics.

Recent developments in nucleic acid delivery with polyethylenimines

Polyethylenimines (PEIs) have proven to be highly efficient and versatile agents for nucleic acid delivery in vitro and in vivo. Despite the low biodegradability of these polymers, they have been used in several clinical trials and the results suggest that the nucleic acid/PEI complexes have a good safety profile. The high transfection efficiency of PEIs probably relies on the fact that these polymers possess a stock of amines that can undergo protonation during the acidification of endosomes. This buffering capacity likely enhances endosomal escape of the polyplexes through the "proton sponge" effect. PEIs have also attracted great interest because the presence of many amino groups allow for easy chemical modifications or conjugation of targeting moieties and hydrophilic polymers. In the present chapter, we summarize and discuss the mechanism of PEI-mediated transfection, as well as the recent developments in PEI-mediated DNA, antisense oligonucleotide, and siRNA delivery.

Chitosan-graft-polyethylenimine/DNA nanoparticles as novel non-viral gene delivery vectors targeting osteoarthritis

The development of safe and efficient gene carriers is the key to the clinical success of gene therapy. The present study was designed to develop and evaluate the chitosan-graft-polyethylenimine (CP)/DNA nanoparticles as novel non-viral gene vectors for gene therapy of osteoarthritis. The CP/DNA nanoparticles were produced through a complex coacervation of the cationic polymers with pEGFP after grafting chitosan (CS) with a low molecular weight (Mw) PEI (Mw = 1.8 kDa). Particle size and zeta potential were related to the weight ratio of CP:DNA, where decreases in nanoparticle size and increases in surface charge were observed as CP content increased. The buffering capacity of CP was significantly greater than that of CS. The transfection efficiency of CP/DNA nanoparticles was similar with that of the Lipofectamine™ 2000, and significantly higher than that of CS/DNA and PEI (25 kDa)/DNA nanoparticles. The transfection efficiency of the CP/DNA nanoparticles was dependent on the weight ratio of CP:DNA (w/w). The average cell viability after the treatment with CP/DNA nanoparticles was over 90% in both chondrocytes and synoviocytes, which was much higher than that of PEI (25 kDa)/DNA nanoparticles. The CP copolymers efficiently carried the pDNA inside chondrocytes and synoviocytes, and the pDNA was detected entering into nucleus. These results suggest that CP/DNA nanoparticles with improved transfection efficiency and low cytotoxicity might be a safe and efficient non-viral vector for gene delivery to both chondrocytes and synoviocytes.

Enhanced efficiency of P-element mediated transgenesis in Drosophila: Microinjection of DNA complexed with nanomaterial

The efficiency of genetic transformation technology to generate stable transgenics depends upon the successful delivery of plasmid DNA in embryonic cells. The available gene vectors facilitate efficient plasmid DNA delivery to the cellular milieu but are exposed to nuclease degradation. Recent in vitro studies suggest encapsulation of plasmid DNA with nanomaterial(s) for better protection against nucleases. Therefore, in this study, we tested if complexing of free plasmid DNA with linear polyethylenimine (LPEI, 25 kDa) based nanoparticle (LPN) enhances the efficiency of transformation (transgenesis) by using Drosophila based germ-line transformation technology. Here, we show that the LPN-DNA complex not only enhances the efficiency of this transgenic technology at a DNA concentration of 0.04 μg/μl but also reduces the DNA quantity required to generate transgenics by ten folds. This approach has potential applications for other types of transgenesis and nucleic acid injection methods in Drosophila as well as other popular genetic model systems.

In vivo safety evaluation of polyarginine coated magnetic nanovectors

Safety and efficacy are of critical importance to any nanomaterial-based diagnostic and therapy. The innocuity and functionality of a nanomaterial in vivo is largely dependent on the physicochemical properties of the material, particularly its surface coating. Here, we evaluated the influence of polycationic coating on the efficacy, clearance organ uptake, and safety of magnetic nanovectors designed for siRNA delivery. Polyethylene glycol (PEG) coated superparamagnetic iron oxide nanoparticles (NPs) of 12 nm in core diameter were modified with a polycationic coating of either poly-l-arginine (pArg) or polyethylenimine (PEI) and further covalently functionalized with siRNA oligonucleotides. The produced NP-pArg-siRNA and NP-PEI-siRNA nanovectors were similar in hydrodynamic size (21 and 22 nm, respectively) but significantly differed in zeta potentials (+2.1 mV and +29.8 mV, respectively). Fluorescence quantification assays revealed that the NP-pArg-siRNA nanovector was 3-fold more potent than NP-PEI-siRNA in delivering siRNA and 1.8-fold more effective in gene silencing when tested in rat C6 glioblastoma cells. In vivo, both nanovector formulations were similarly taken up by the spleen and liver as determined by histopathological and hemopathological assays. However, PEI coated nanovectors elicited severe hemoincompatibility and damage to the liver and spleen, while pArg coated nanovectors were found to be safe and tolerable. Combined, our findings suggest that polycationic coatings of pArg were more effective and safer than commonly used PEI coatings for preparation of nanovectors. The NP-pArg-siRNA nanovector formulation developed here shows great potential for in vivo based biomedical applications.

Effect of N/P ratios on physicochemical stability, cellular association, and gene silencing efficiency for trimethyl chitosan/small interfering RNA complexes

N,N,N-Trimethyl chitosan (TMC) with 40% quaternization was used as a vector for small interfering RNA (siRNA) delivery. Nano-sized complexes were formed in water by mixing siRNA with TMC; the smallest particle sizes were obtained at a N/P ratio of 10. The complexes had a positive surface charge that increased with increases in the N/P ratio and leveled off at +20 mV with N/P ratios > 10. The majority of particles had a diameter <100 nm under transmission electron microscope (TEM). When the N/P ratio was >10, the binding efficiency of TMC with siRNA was >90%. In 25% fetal bovine serum, the TMC/siRNA complexes with N/P ratios of 10 and 20 were intact for 12 and 48 h, respectively. TMC/siRNA complexes with an N/P ratio > 5 efficiently entered the human embryonic kidney (HEK) 293 cells and trapped initially in the lysosomes, which could then relocate in the cytoplasm. Gene silencing, tested by using enhanced green fluorescent protein (EGFP), was reduced to ~60% by the complexes with N/P ratios of 10 and 20. Specific silencing was confirmed by dose dependency and nonsilencing effect of sequence-mismatch siRNA. No significant cytotoxicity was detected for the TMC/siRNA complexes. In this study, the influence of the N/P ratio on TMC/siRNA complexes was systematically investigated and TMC was found to be an effective vector for siRNA delivery using optimized formulations.

Development of Magnetic Nanoparticles for Cancer Gene Therapy: A Comprehensive Review

Since they were first proposed as nonviral transfection agents for their gene-carrying capacity, magnetic nanoparticles have been studied thoroughly, both in vitro and in vivo. Great effort has been made to manufacture biocompatible magnetic nanoparticles for use in the theragnosis of cancer and other diseases. Here we survey recent advances in the study of magnetic nanoparticles, as well as the polymers and other coating layers currently available for gene therapy, their synthesis, and bioconjugation processes. In addition, we review several gene therapy models based on magnetic nanoparticles.

Branched polyethylenimine-grafted-carboxymethyl chitosan copolymer enhances the delivery of pDNA or siRNA in vitro and in vivo

To generate a good carrier for gene transfection, O-carboxymethyl chitosan-graft-branched polyethylenimine (OCMPEI) copolymers were synthesized by increasing the weight percentage of branched polyethylenimine conjugated to the carboxyl groups of O-carboxymethyl chitosan. These spherical polyplexes with plasmid deoxyribonucleic acid (pDNA) or small interfering ribonucleic acid (siRNA) had diameters of ∼200–300 nm or ∼10–25 nm, respectively, and displayed significant transfection efficiency in normal and tumor cells. In particular, expression of green fluorescent protein (GFP) following pDNA transfection was effectively suppressed by delivery of GFP-specific siRNA with the same copolymer. The optimized copolymer and polyplexes were nontoxic in vitro and in vivo. The use of endocytosis inhibitors to investigate the mechanisms of transfection of the polyplexes suggested the involvement of macropinocytosis. An in vivo study in mice showed excellent GFP expression in the lung, kidney, and liver. The results demonstrated that the OCMPEI copolymer prepared in this study is a promising carrier for in vitro and in vivo gene delivery applications.

Design of polyethylene glycol-polyethylenimine nanocomplexes as non-viral carriers: mir-150 delivery to chronic myeloid leukemia cells

MicroRNAs (miRNAs) are acknowledged as indispensable regulators relevant in many biological processes, and they have been pioneered as therapeutic targets for curing disease. miRNAs are single-stranded, small (19-22 nt) regulatory non-coding RNAs whose deregulation of expression triggers human cancers, including leukemias, mainly through dysregulation of expression of leukemia genes. miRNAs can function as tumour suppressors (suppressing malignant potential) or oncogenes (activating malignant potential) like actors of complex diseases. To address the issue of overcoming instability and low transfection efficiency in vitro, the polyethylene glycol-polyethyleneimine (PEG-PEI) nanoparticle was used as non-viral vector carrier for miR-150 transfection, which is downregulated in chronic myeloid leukemia. PEG-PEI [PEG(550)3 -g-PEI(1800) ]/miRNA nanocomplexes were synthesised and characterised by particle size distribution (PSD), polydispersity index (PDI) and zeta potential, surface charge, their cytotoxicity, and transfection efficiency. Interaction with human leukemia cells (K-562 and KU812) and control cells NCI-BL2347 with them has been investigated. The transfection efficiency of PEG-PEI/miRNA at N/P 26 rose 6.7-fold above the control by qRT-PCR. The size of homogenous nanocomplexes (PBI < 0.5) was 160.8 ± 11 nm. The data indicate that PEG-PEI may be an encouraging non-viral carrier for altering miRNA expression in the treatment of chronic myeloid leukemia, with many advantages such as relatively high miRNA transfection efficiency and low cytotoxicity.

Polyethylenimine combined with liposomes and with decreased numbers of primary amine residues strongly enhanced therapeutic antiviral efficiency against herpes simplex virus type 2 in a mouse model

The development of antiviral agents that have novel mechanisms of action is urgently required in the topical therapy of herpes simplex virus type 2 (HSV-2) infections. We reported previously that topical application of branched 3610-Da polyethylenimine (PEI) exhibited preventative antiviral activity. In this study, to develop therapeutic anti-HSV-2 agents, the most potent PEI combined with ~200 nm-sized liposomes with or without oleic acid (liposomes/PEI) was selected in vitro and further evaluated using in vivo studies. The mechanism of action in vivo was elucidated using PEIs with decreased numbers of primary amine residues, resulting from ethylene carbonate treatment, and polyallylamine, a linear polyamine consisting of primary amines. Cytotoxicity and antiviral activity in vitro, and the appearance of acute herpetic disease and virus yields in mice intravaginally administered with liposomes/PEI were evaluated in cell culture assays and a mouse genital herpes model, respectively. In addition, the cellular association of liposome/PEI was examined by flow cytometry and confocal microscopy. PEI showed higher antiviral activity postinfection than preinfection in vivo. Liposome/PEI and PEI with decreased numbers of primary amine residues at a dose of 0.2 mg PEI/mouse exhibited more potent therapeutic antiviral activity than acyclovir and PEI alone without acute lesion appearance or toxicity pre- or postinfection, but polyallylamine was moderately effective only preinfection. Liposome concentrations were important for the effectiveness of liposome/PEI. This finding suggests that PEI combined with liposomes and with slightly decreased numbers of primary amines may be an effective vaginally administrated antiviral drug, and secondary and tertiary amine residues of PEI may contribute to the inhibitory efficiency against viral infection.

Novel polyethylenimine-derived nanoparticles for in vivo gene delivery

INTRODUCTION

Branched and linear polyethylenimines (PEIs) are cationic polymers that have been used to deliver nucleic acids both in vitro and in vivo. Owing to the high cationic charge, the branched polymers exhibit high transfection efficiency, and particularly PEI of molecular weight 25 kDa is considered as a gold standard in gene delivery. These polymers have been extensively studied and modified with different ligands so as to achieve the targeted delivery.

AREAS COVERED

The application of PEI in vivo promises to take the polymer-based vector to the next level wherein it can undergo clinical trials and subsequently could be used for delivery of therapeutics in humans. This review focuses on the various recent developments that have been made in the field of PEI-based delivery vectors for delivery of therapeutics in vivo.

EXPERT OPINION

The efficacy of PEI-based delivery vectors in vivo is significantly high and animal studies demonstrate that such systems have a potential in humans. However, we feel that though PEI is a promising vector, further studies involving PEI in animal models are needed so as to get a detailed toxicity profile of these vectors. Also, it is imperative that the vector reaches the specific organ causing little or no undesirable effects to other organs.