Proteoglycans mediate cationic liposome-DNA complex-based gene delivery in vitro and in vivo

Degradation of specific glycosaminoglycans improves transfection efficiency and vector production in transient lentiviral vector manufacturing processes

Both cell surface and soluble extracellular glycosaminoglycans have been shown to interfere with the exogenous nucleic acid delivery efficiency of non-viral gene delivery, including lipoplex and polyplex-mediated transfection. Most gene therapy viral vectors used commercially and in clinical trials are currently manufactured using transient transfection-based bioprocesses. The growing demand for viral vector products, coupled with a global shortage in production capability, requires improved transfection technologies and processes to maximise process efficiency and productivity. Soluble extracellular glycosaminoglycans were found to accumulate in the conditioned cell culture medium of suspension adapted HEK293T cell cultures, compromising transfection performance and lentiviral vector production. The enzymatic degradation of specific, chondroitin sulphate-based, glycosaminoglycans with chondroitinase ABC was found to significantly enhance transfection performance. Additionally, we report significant improvements in functional lentiviral vector titre when cultivating cells at higher cell densities than those utilised in a control lentiviral vector bioprocess; an improvement that was further enhanced when cultures were supplemented with chondroitinase ABC prior to transfection. A 71.2% increase in functional lentiviral vector titre was calculated when doubling the cell density prior to transfection compared to the existing process and treatment of the high-density cell cultures with 0.1 U/mL chondroitinase ABC resulted in a further 18.6% increase in titre, presenting a method that can effectively enhance transfection performance.

PEG vs. zwitterions: How these surface decorations determine cellular uptake of lipid-based nanocarriers

AIM

To evaluate the impact of polyethylene glycol (PEG) and zwitterionic surface decoration of lipid-based nanocarriers (NC) on cellular uptake.

METHODS

Anionic, neutral and cationic zwitterionic lipid-based NCs based on lecithin were compared with conventional PEGylated lipid-based NCs regarding stability in biorelevant fluids, interaction with endosome mimicking membranes, cytocompatibility, cellular uptake and permeation across intestinal mucosa.

RESULTS

PEGylated and zwitterionic lipid-based NCs exhibited a droplet size between 100 and 125 nm with a narrow size distribution. For the PEGylated and zwitterionic lipid-based NCs only minor alterations in size and PDI in fasted state intestinal fluid and mucus containing buffer were observed, demonstrating similar bioinert properties. Erythrocytes interaction studies revealed enhanced endosomal escape properties for zwitterionic lipid-based NCs compared to PEGylated lipid-based NCs. For the zwitterionic lipid-based NCs negligible cytotoxicity on Caco-2 and HEK cells, even in the highest tested concentration of 1 % (v/v) was recorded. The PEGylated lipid-based NCs showed a cell survival of ≥75 % for concentrations ≤0.05 % on Caco-2 and HEK cells, which was considered as non-toxic. For the zwitterionic lipid-based NCs up to 60-fold higher cellular uptake on Caco-2 cells was determined compared to PEGylated lipid-based NCs. For the cationic zwitterionic lipid-based NCs the highest cellular uptake with 58.5 % and 40.0 % in Caco-2 and HEK cells, respectively, was determined. The results were confirmed visually by life cell imaging. Ex-vivo permeation experiments using rat intestinal mucosa demonstrated up to 8.6-fold enhanced permeation of the lipophilic marker coumarin-6 in zwitterionic lipid-based NCs compared to the control. Up to 6.9-fold enhanced permeation of coumarin-6 in neutral zwitterionic lipid-based NCs compared to the PEGylated counterpart was recorded.

CONCLUSION

The replacement of PEG surfactants with zwitterionic surfactants is a promising approach to overcome the drawbacks of conventional PEGylated lipid-based NCs regarding intracellular drug delivery.

A Comparison of Cellular Uptake Mechanisms, Delivery Efficacy, and Intracellular Fate between Liposomes and Extracellular Vesicles

A key aspect for successful drug delivery via lipid-based nanoparticles is their internalization in target cells. Two prominent examples of such drug delivery systems are artificial phospholipid-based carriers, such as liposomes, and their biological counterparts, the extracellular vesicles (EVs). Despite a wealth of literature, it remains unclear which mechanisms precisely orchestrate nanoparticle-mediated cargo delivery to recipient cells and the subsequent intracellular fate of therapeutic cargo. In this review, internalization mechanisms involved in the uptake of liposomes and EVs by recipient cells are evaluated, also exploring their intracellular fate after intracellular trafficking. Opportunities are highlighted to tweak these internalization mechanisms and intracellular fates to enhance the therapeutic efficacy of these drug delivery systems. Overall, literature to date shows that both liposomes and EVs are predominantly internalized through classical endocytosis mechanisms, sharing a common fate: accumulation inside lysosomes. Studies tackling the differences between liposomes and EVs, with respect to cellular uptake, intracellular delivery and therapy efficacy, remain scarce, despite its importance for the selection of an appropriate drug delivery system. In addition, further exploration of functionalization strategies of both liposomes and EVs represents an important avenue to pursue in order to control internalization and fate, thereby improving therapeutic efficacy.

A mutated glycosaminoglycan-binding domain functions as a novel probe to selectively target heparin-like epitopes on tumor cells

The high heterogeneity and mutation rate of cancer cells often lead to the failure of targeted therapy, and therefore, new targets for multitarget therapy of tumors are urgently needed. Aberrantly expressed glycosaminoglycans (GAGs) have been shown to be involved in tumorigenesis and are promising new targets. Recently, the GAG-binding domain rVAR2 of the Plasmodium falciparum VAR2CSA protein was identified as a probe targeting cancer-associated chondroitin sulfate A-like epitopes. In this study, we found that rVAR2 could also bind to heparin (Hep) and chondroitin sulfate E. Therefore, we used rVAR2 as a model to establish a method based on random mutagenesis of the GAG-binding protein and phage display to identify and optimize probes targeting tumor GAGs. We identified a new probe, VAR2HP, which selectively recognized Hep by interacting with unique epitopes consisting of a decasaccharide structure that contains at least three HexA2S(1-4)GlcNS6S disaccharides. Moreover, we found that these Hep-like epitopes were overexpressed in various cancer cells. Most importantly, our in vivo experiments showed that VAR2HP had good biocompatibility and preferentially localizes to tumors, which indicates that VAR2HP has great application potential in tumor diagnosis and targeted therapy. In conclusion, this study provides a strategy for the discovery of novel tumor-associated GAG epitopes and their specific probes.

pH-Responsive Lipid Nanoparticles Achieve Efficient mRNA Transfection in Brain Capillary Endothelial Cells

The blood–brain barrier (BBB), which is comprised of brain capillary endothelial cells, plays a pivotal role in the transport of drugs from the blood to the brain. Therefore, an analysis of proteins in the endothelial cells, such as transporters and tight junction proteins, which contribute to BBB function, is important for the development of therapeutics for the treatment of brain diseases. However, gene transfection into the vascular endothelial cells of the BBB is fraught with difficulties, even in vitro. We report herein on the development of lipid nanoparticles (LNPs), in which mRNA is encapsulated in a nano-sized capsule composed of a pH-activated and reductive environment-responsive lipid-like material (ssPalm). We evaluated the efficiency of mRNA delivery into non-polarized human brain capillary endothelial cells, hCMEC/D3 cells. The ssPalm LNPs permitted marker genes (GFP) to be transferred into nearly 100% of the cells, with low toxicity in higher concentration. A proteomic analysis indicated that the ssPalm-LNP had less effect on global cell signaling pathways than a Lipofectamine MessengerMAX/GFP-encoding mRNA complex (LFN), a commercially available transfection reagent, even at higher mRNA concentrations.

Magnetic Nanoparticles as a Component of Peptide-Based DNA Delivery System for Suicide Gene Therapy of Uterine Leiomyoma

Suicidegene therapy is considered a promising approach for the treatment of uterine leiomyoma (UL), a benign tumor in women characterized by precise localization. In this study, we investigate the efficiency of αvβ3 integrin-targeted arginine-rich peptide carrier R6p-cRGD electrostatically bound to magnetic nanoparticles (MNPs) for targeted DNA delivery into the UL cells. The physico–chemical and cytotoxic properties, transfection efficiency, and specificity of R6p-cRGD/DNA/MNPs polyplexes were evaluated. The addition of MNPs resulted in a decrease in the time needed for successful transfection with simultaneous increase in efficiency. We revealed a therapeutic effect on primary UL cells after delivery of plasmid encoding the herpes simplex virus type 1 (HSV-1) thymidine kinase gene. Treatment with ganciclovir resulted in 20% efficiency of suicide gene therapy in UL cells transfected with the pPTK-1 plasmid. Based on these results, we conclude that the use of cationic peptide carriers with MNPs can be promising for the development of modular non-viral carriers for suicide gene delivery to UL cells.

Polycation-Mediated Transfection: Mechanisms of Internalization and Intracellular Trafficking

Polyplex-mediated gene transfection is now in its' fourth decade of serious research, but the promise of polyplex-mediated gene therapy has yet to fully materialize. Only approximately one in a million applied plasmids actually expresses. A large part of this is due to an incomplete understanding of the mechanism of polyplex transfection. There is an assumption that internalization must follow a canonical mechanism of receptor mediated endocytosis. Herein, we present arguments that untargeted (and most targeted) polyplexes do not utilize these routes. By incorporating knowledge of syndecan-polyplex interactions, we can show that syndecans are the "target" for polyplexes. Further, it is known that free polycations (which disrupt cell-membranes by acid-catalyzed hydrolysis of phospholipid esters) are necessary for (untargeted) endocytosis. This can be incorporated into the model to produce a novel mechanism of endocytosis, which fits the observed phenomenology. After membrane translocation, polyplex containing vesicles reach the endosome after diffusing through the actin mesh below the cell membrane. From there, they are acidified and trafficked toward the lysosome. Some polyplexes are capable of escaping the endosome and unpacking, while others are not. Herein, it is argued that for some polycations, as acidification proceeds the polyplexes excluding free polycations, which disrupt the endosomal membrane by acid-catalyzed hydrolysis, allowing the polyplex to escape. The polyplex's internal charge ratio is now insufficient for stability and it releases plasmids which diffuse to the nucleus. A small proportion of these plasmids diffuse through the nuclear pore complex (NPC), with aggregation being the major cause of loss. Those plasmids that have diffused through the NPC will also aggregate, and this appears to be the reason such a small proportion of nuclear plasmids express mRNA. Thus, the structural features which promote unpacking in the endosome and allow for endosomal escape can be determined, and better polycations can be designed.

Octreotide-Targeted Lcn2 siRNA PEGylated Liposomes as a Treatment for Metastatic Breast Cancer

Lcn2 overexpression in metastatic breast cancer (MBC) can lead to cancer progression by inducing the epithelial-to-mesenchymal transition and enhancing tumor angiogenesis. In this study, we engineered a PEGylated liposomal system encapsulating lipocalin 2 (Lcn2) small interfering RNA (Lcn2 siRNA) for selective targeting MBC cell line MCF-7 and triple-negative breast cancer cell line MDA-MB-231. The PEGylated liposomes were decorated with octreotide (OCT) peptide. OCT is an octapeptide analog of somatostatin growth hormone, having affinity for somatostatin receptors, overexpressed on breast cancer cells. Optimized OCT-targeted Lcn2 siRNA encapsulated PEGylated liposomes (OCT-Lcn2-Lipo) had a mean size of 152.00 nm, PDI, 0.13, zeta potential 4.10 mV and entrapment and loading efficiencies of 69.5% and 7.8%, respectively. In vitro uptake and intracellular distribution of OCT-Lcn2-Lipo in MCF-7 and MDA-MB-231 and MCF-12A cells demonstrated higher uptake for the OCT-targeted liposomes at 6 h by flow cytometry and confocal microscopy. OCT-Lcn2-lipo could achieve approximately 55-60% silencing of Lcn2 mRNA in MCF-7 and MDA-MB-231 cells. OCT-Lcn2-Lipo also demonstrated in vitro anti-angiogenic effects in MCF-7 and MDA-MB-231 cells by reducing VEGF-A and reducing the endothelial cells (HUVEC) migration levels. This approach may be useful in inhibiting angiogenesis in MBC.

The era of gene therapy: From preclinical development to clinical application

Three decades of promise have culminated in the development of gene therapies that can be applied to a broad range of human diseases. After a brief history, we provide an overview of gene therapy types and delivery methods, gene editing technologies, regulatory affairs, clinical trials, approved products, ongoing challenges, and future goals. Information on clinical trials of candidates and on approved products for gene therapy developed between 1988 and 2020 is systematically collated. To obtain this global information, we scanned and reviewed more than 46,000 records of clinical trials from 17 clinical trial database providers. The medical benefits of transformative gene therapies are gradually being accepted by payors, and a significant increase in the number of gene therapy clinical trials and approved gene therapy products has resulted.

Development of iRGD-Modified Peptide Carriers for Suicide Gene Therapy of Uterine Leiomyoma

Uterine leiomyoma (UL) is one of the most common benign tumors in women that often leads to many reproductive complications. Suicide genetherapy was suggested as a promising approach for UL treatment. In the present study, we describe iRGD ligand-conjugated cysteine-rich peptide carrier RGD1-R6 for targeted DNA delivery to αvβ3 integrin-expressing primary UL cells. The physico-chemical properties, cytotoxicity, transfection efficiency and specificity of DNA/RGD1-R6 polyplexes were investigated. TheHSV-1thymidine kinase encoding plasmid delivery to PANC-1pancreatic carcinoma cells and primary UL cells resulted in significant suicide gene therapy effects. Subsequent ganciclovir treatment decreased cells proliferative activity, induced of apoptosis and promoted cells death.The obtained results allow us to concludethatthe developed RGD1-R6 carrier can be considered a promising candidate for suicide gene therapy of uterine leiomyoma.

A role of heparan sulphate proteoglycan in the cellular uptake of lipocalins ß-lactoglobulin and allergen Fel d 4

Lipocalins, small extracellular hydrophobic molecule carriers, can be internalized by a variety of different cells. However, to date receptors have only been identified for human lipocalins. Here, we specifically investigated uptake mechanisms for lipocalins ß-lactoglobulin and Fel d 4 in HeLa and Chinese hamster ovary (CHO) cells. We provide evidence that cell surface heparan sulphate proteoglycan is essential for internalization of these lipocalins. In HeLa cells, lipocalin uptake was inhibited by competition with soluble heparin, enzymatic digestion of cellular heparan sulphate by heparinase and inhibition of its biosynthesis by sodium chlorate. Biochemical studies by heparin affinity chromatography and colocalization studies further supported a role of heparan sulphate proteoglycan in lipocalin uptake. Finally, lipocalin uptake was blocked in CHO mutant cells defective in glycosaminoglycan biosynthesis whereas in wild-type cells it was clearly detectable. Thus, cell surface heparan sulphate proteoglycan represents a novel component absolutely participating in the cellular uptake of some lipocalins.

Cellular uptake of self-emulsifying drug-delivery systems: polyethylene glycol versus polyglycerol surface

Aim: Comparison of the impact of polyethylene glycol (PEG) and polyglycerol (PG) surface decoration on self-emulsifying drug delivery system (SEDDS)-membrane interaction and cellular uptake. Materials & methods: PEG-, PEG/PG- and PG-SEDDS were assessed regarding their self-emulsifying properties, surface charge, bile salt fusibility, cellular uptake and interaction with endosome-mimicking membranes. Results: SEDDS exhibited droplet sizes between 150 and 175 nm, a narrow size distribution and self-emulsified within 7 min. Higher PEG-surfactant amounts in SEDDS resulted in charge-shielding and thus in a decrease of ζ potential up to Δ11 mV. The inert PEG-surface hampered bile salt fusion and interfered SEDDS-cell interaction. By reducing the PEG-surfactant amount to 10%, cellular uptake increased twofold compared with PEG-SEDDS containing 40% PEG-surfactant. PG-SEDDS containing no PEG-surfactants showed a threefold increased cellular uptake. Furthermore, complete replacement of PEG-surfactants by PG-surfactants led to enhanced cellular interaction and improved disruption endosome-like membranes. Conclusion: PG-surfactants demonstrated high potential to address PEG-surface associated drawbacks in SEDDS.

In vivo activation of PEGylated long circulating lipid nanoparticle to achieve efficient siRNA delivery and target gene knock down in solid tumors

We developed a lipid nanoparticle formulation (LNPK15) to deliver siRNA to a tumor for target gene knock down. LNPK15 is highly PEGylated with 3.3% 1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine-N-(polyethylene glycol-2000) (PEG-DSPE) and shows a long duration: the half-lives of siRNA in LNPK15 were 15.2 and 27.0h in mice and monkeys, respectively. Although LNPK15 encapsulating KRAS-targeting siRNA (LNPK15/KRAS) had very weak KRAS gene knock down activity in MIA PaCa-2 cells in vitro, LNPK15/KRAS showed a strong anti-tumor efficacy in MIA PaCa-2 tumor xenograft mice after intravenous administration at 5mg/kg twice weekly. KRAS mRNA and protein knock down was observed in tumor tissue, suggesting on-target anti-tumor efficacy. In order to elucidate the in vitro-in vivo discrepancy, we performed ex vivo knock down assay using serum samples obtained after intravenous administration of LNPK15/KRAS to mice and monkeys. The collected samples were added to MIA PaCa-2 cells, and KRAS gene knock down was evaluated after a 24-h incubation period. The knock down efficacy was weak (≈20%) with serum samples at initial sampling point (2h), and it became much stronger (∼90%) with serum samples at later time points. Lipid composition of LNPK15 in the serum samples was also investigated. Among the five lipids incorporated in LNPK15, PEG-DSPE was degraded more rapidly than siRNA and the other lipids in both mice and monkeys. In vitro lipase treatment of LNPK15/KRAS also hydrolyzed PEG-DSPE and enhanced knock down activity. From these results, it was concluded that LNPK15 acquires increased knock down activity after undergoing PEG-DSPE hydrolysis in vivo, and that is the key mechanism to achieve both long circulation and potent knock down efficiency. We also proposed an in vitro assay system using lipase for quality control of LNP to ensure biological activity.

Hyaluronan Reduces Cationic Liposome-Induced Toxicity and Enhances the Antitumor Effect of Targeted Gene Delivery in Mice

Cationic nanocarriers are reported to induce cell necrosis, especially in the lungs upon systemic administration. The release of damage-associated molecular patterns, such as mitochondrial DNA from the injured cell may result in the inflammatory toxicity of the nanocarrier, which has largely limited its clinical application. Partial blocking of the surface charge of cationic nanocarriers might improve their safety. As hyaluronan (HA) is an anionic polysaccharide that is widely used for specific binding to CD44 to improve the cellular uptake efficiency in tumor-targeting therapy, in this study, we modified cationic liposomes (LP) with the negatively charged HA at a mass ratio of 10% to prepare targeted HA-modified cationic liposomes (HALP). Cationic liposomes modified with hyaluronan showed significantly less cytotoxicity due to the blockage of their surface charge than the unmodified liposomes. In addition, HA modification helped to reduce cell necrosis in lung tissue and reduced the amount of mitochondria subsequently released, which alleviated pulmonary inflammation in mice. HA-modified liposomes also improved the survival of mice injected with a fatal dose of HALP compared with mice injected with cationic LP. In addition, both serological biochemical analysis and histological examination proved that a liposome modified with HA is a safer carrier for systemic administration than an unmodified liposome. Furthermore, HALP/survivin exhibited an enhanced antitumor effect by inhibiting tumor growth and promoting tumor cell apoptosis compared with the unmodified LP group. In conclusion, compared to the properties of cationic liposomes, liposomes modified with 10% HA (HALP) might be gene vectors with lower toxicity and higher tumor targeting efficiency.

Microfluidic-based platform to mimic the in vivo peripheral administration of neurotropic nanoparticles

Aim: Propose a nanoparticle for neuron-targeted retrograde gene delivery and describe a microfluidic-based culture system to provide insight into vector performance and safety. Methods: Using compartmentalized neuron cultures we dissected nanoparticle bioactivity upon delivery taking advantage of (quantitative) bioimaging tools. Results: Targeted and nontargeted nanoparticles were internalized at axon terminals and retrogradely transported to cell bodies at similar average velocities but the former have shown an axonal flux 2.7-times superior to nontargeted nanoparticles, suggesting an improved cargo-transportation efficiency. The peripheral administration of nanoparticles to axon terminals is nontoxic as compared with their direct administration to the cell body or whole neuron. Conclusion: A neuron-targeted nanoparticle system was put forward. Microfluidic-based neuron cultures are proposed as a powerful tool to investigate nanoparticle bio-performance.

Spatial Control of Gene Expression by Nanocarriers Using Heparin Masking and Ultrasound-Targeted Microbubble Destruction

We developed a method to spatially control gene expression following nonviral delivery of DNA. This method includes surface-modifying DNA nanocarriers with heparin to inhibit passive gene transfer in both the target and the off-target tissues and using ultrasound-targeted microbubble destruction (UTMD) to selectively activate heparin-inhibited gene transfer at the target site. We observed that the engraftment of heparin onto the surface of cationic liposomes reduced off-target gene expression in the liver, a major site of nanoplex accumulation, by more than 700-fold compared to the nonheparinized PEGylated liposomes. We further observed that tumor-directed UTMD increased gene transfer with heparin-modified nanoplexes by more than 10-fold. This method augmented tumor-to-liver selectivity of gene expression by 4000-fold compared to controls. We conclude that heparinization of DNA nanocarriers in conjunction with localized activation of gene transfer by UTMD may enable greater spatial control over genetic therapy.

Effect of surface properties on liposomal siRNA delivery

Liposomes are one of the most widely investigated carriers for siRNA delivery. The surface properties of liposomal carriers, including the surface charge, PEGylation, and ligand modification can significantly affect the gene silencing efficiency. Three barriers of systemic siRNA delivery (long blood circulation, efficient tumor penetration and efficient cellular uptake/endosomal escape) are analyzed on liposomal carriers with different surface charges, PEGylations and ligand modifications. Cationic formulations dominate siRNA delivery and neutral formulations also have good performance while anionic formulations are generally not proper for siRNA delivery. The PEG dilemma (prolonged blood circulation vs. reduced cellular uptake/endosomal escape) and the side effect of repeated PEGylated formulation (accelerated blood clearance) were discussed. Effects of ligand modification on cationic and neutral formulations were analyzed. Finally, we summarized the achievements in liposomal siRNA delivery, outlined existing problems and provided some future perspectives.

Challenges in carrier-mediated intracellular delivery: moving beyond endosomal barriers

The deployment of molecular to microscale carriers for intracellular delivery has tremendous potential for biology and medicine, especially for in vivo therapies. The field remains limited, however, by a poor understanding of how carriers gain access to the cell interior. In this review, we provide an overview of the different types of carriers, their speculated modes of entry, putative pathways of vesicular transport, and sites of endosomal escape. We compare this alongside pertinent examples from the cell biology of how viruses, bacteria, and their effectors enter cells and escape endosomal confinement. We anticipate insights into the mechanisms of cellular entry and endosomal escape will benefit future research efforts on effective carrier-mediated intracellular delivery. WIREs Nanomed Nanobiotechnol 2016, 8:465-478. doi: 10.1002/wnan.1377 For further resources related to this article, please visit the WIREs website.

Biotin-conjugated fusogenic liposomes for high-quality cell purification

Purification of defined cell populations from mixed primary cell sources is essential for many biomedical and biotechnological applications but often very difficult to accomplish due to missing specific surface markers. In this study, we developed a new approach for efficient cell population separation based on the specific membrane fusion characteristics of distinct cell types upon treatment with fusogenic liposomes. When such liposomes are conjugated with biotin, specific cell populations can be efficiently surface functionalized by biotin after liposomal treatment while other populations remain unlabeled. Due to the high affinity of biotin for avidin-like proteins, biotin functionalized cells are ideal targets for conjugation of e.g. avidin tagged magnetic beads, fluorophores or antibodies with bioanalytical relevance. Here, based on the differential biotinylation of distinct cell populations high quality separation of cardiac fibroblasts from myocytes, and cerebromicrovascular endothelial cells from fibroblasts was successfully established.

Lipid nanoparticles for short interfering RNA delivery

The discovery of RNA interference (RNAi) in mammalian cells has created a new class of therapeutics based on the reversible silencing of specific disease-causing genes. This therapeutic potential depends on the ability to deliver inducers of RNAi, such as short-interfering RNA (siRNA) and micro-RNA (miRNA), to cells of target tissues. This chapter reviews various challenges and delivery strategies for siRNA, with a particular focus on the development of lipid nanoparticle (LNP) delivery technologies. Currently, LNP delivery systems are the most advanced technology for systemic delivery of siRNA, with numerous formulations under various stages of clinical trials. We also discuss methods to improve gene silencing potency of LNP-siRNA, as well as application of LNP technologies beyond siRNA to the encapsulation of other nucleic acids such as mRNA and clustered regularly interspaced short palindromic repeats (CRISPR).

Apoferritin applications in nanomedicine

Nanomedicine as a continuously evolving discipline is still looking for a structure with perfect properties that is usable as a multifunctional transporter. Great potential is attributed to synthetic materials such as fullerenes, porous hollow silica nanoparticles and single-wall nanotubes, among others. However, materials that are natural to the human body are more acceptable by the organism, and thus become an attractive approach in this field of research. Ferritins are proteins that naturally occur in most living organisms throughout evolution and may be a possible transporter choice. Numerous applications have demonstrated the possibilities of iron-free ferritins, called apoferritins, serving as platforms for various nanomedical purposes This article summarizes the advantages and disadvantages of these proteins and discusses their practical applications and future perspectives.

Nanotherapy for Cancer: Targeting and Multifunctionality in the Future of Cancer Therapies

Cancer continues to be a prevalent and lethal disease, despite advances in tumor biology research and chemotherapy development. Major obstacles in cancer treatment arise from tumor heterogeneity, drug resistance, and systemic toxicities. Nanoscale delivery systems, or nanotherapies, are increasing in importance as vehicles for antineoplastic agents because of their potential for targeting and multifunctionality. We discuss the current field of cancer therapy and potential strategies for addressing obstacles in cancer treatment with nanotherapies. Specifically, we review the strategies for rationally designing nanoparticles for targeted, multimodal delivery of therapeutic agents.

Cationic nanoemulsions as potential carriers for intracellular delivery

Successful cytosolic delivery enables opportunities for improved treatment of various genetic disorders, infectious diseases and cancer. Cationic nanoemulsions were designed using alternative excipients and evaluated for particle size, charge, effect of sterilization on its stability, DNA condensation potential and cellular uptake efficiency. Various concentrations of non-ionic and ionic stabilizers were evaluated to design formula for colloidally stable cationic nanoemulsion. The nanoemulsion comprised of 5% Capmul MCM, 0.5% didodecyldimethylammonium bromide (DDAB), 1% phospholipid, 1% Poloxamer 188 and 2.25% glycerol and possessed particle size of 81.6 ± 3.56 nm and 137.1 ± 1.57 nm before and after steam sterilization, respectively. DNA condensation studies were carried out at various nanoemulsion: DNA ratios ranging from 1:1 to 10:1. Cell uptake studies were conducted on human embryonic kidney (HEK) cell lines which are widely reported for transfection studies. The nanoemulsions showed excellent cellular uptake as evaluated by fluorescence microscopy and flow cytometry. Overall, a colloidally stable cationic nanoemulsion with good DNA condensation ability was successfully fabricated for efficient cytosolic delivery and potential for in vivo effectiveness.

Intracellular gene delivery is dependent on the type of non-viral carrier and defined by the cell surface glycosaminoglycans

Intracellular limiting steps and molecules involved in internalization and intracellular routing of non-viral gene delivery systems are still poorly understood. In this study, the intracellular kinetics of three different gene delivery systems calcium phosphate precipitates (CaP), polyethyleneimine (PEI) and N-[1-(2,3-dioleyl)propyl]-N,N,N-trimethylammonium chloride (DOTAP)) were quantified at cellular, nuclear, transcriptional and translational levels by using qRT-PCR. Additionally, a role of cell surface glycosaminoglycans (GAGs) was evaluated by performing the aforementioned studies in cells devoid of GAGs (pgsB-618) and cells lacking heparan sulphate (HS). The obtained data showed that the intracellular kinetics was dependent on the type of gene carrier and the weakest intracellular step varied between the carriers; rapid elimination of cell-associated pDNA in CaP, nuclear uptake in DOTAP and transcriptional and translational events in PEI mediated transfections. Overall, neither the amount of cell- nor nuclear associated pDNA correlated with transgene expression but the mRNA expression of the transgene correlated well with the expression at protein level. The nuclear uptake of pDNA in all cases was rapid and efficient thus indicating that the post-nuclear processes including transcription and translation steps have a critical role in defining the efficiency of non-viral gene delivery systems. Our study demonstrated that cell-surface GAGs are not essential for cell surface binding and internalization of gene delivery complexes, but they are able to define the intracellular routing of the complexes by leading them to pathways with high pDNA elimination.

Easily controlled grafting of oligonucleotides on γFe2O3 nanoparticles: physicochemical characterization of DNA organization and biological activity studies

We report a one-step process to functionalize superparamagnetic iron oxide nanoparticle (SPIO-NP) surfaces with a controlled number of oligonucleotides. For this study, we use a specific oligonucleotide targeting the signal transducer and activator of transcription 3 (STAT3), a key regulator of cell survival and proliferation. This oligonucleotide is self-complementary and can adopt a hairpin structure. It is labeled with the fluorescein amidite group at the 3'-end. The polyanionic DNA is electrostatically attracted onto the positively charged surface of the bare SPIO-NPs. During synthesis, the molar ratio between the oligonucleotides and nanoparticles was varied from 17.5 to 175. For particles with a mean diameter of 10 nm, a nanoparticle surface saturation is observed corresponding to 70 DNA strands per particle. The increase of DNA density per nanoparticle is correlated to a transition from the hairpin structure adsorbed horizontally on the nanoparticle surface to a vertically ordered surface packing assembly. An in vitro study on human colon carcinoma cell line SW480 shows that the kinetics of internalization and biological activity of the NPs seem to be dependent on the oligonucleotide density. Cell death and the kinetics of internalization are favored by a low density of oligonucleotides.

A neutral envelope-type nanoparticle containing pH-responsive and SS-cleavable lipid-like material as a carrier for plasmid DNA

SS-cleavable proton-activated lipid-like material (ssPalm) functions as a key element in a lipid nanoparticle in which pDNA is encapsulated. The ssPalm contains dual sensing motifs that can respond to the intracellular environment; a proton-sponge unit (tertiary amines) that functions in response to an acidic environment (endosome/lysosome), and disulfide bonding that can be cleaved in a reducing environment (cytosol).

Contribution of syndecans to lipoplex-mediated gene delivery

The long awaited breakthrough of gene therapy significantly depends on the in vivo efficiency of targeted intracellular delivery. Hidden details of cellular uptake present a great hurdle for non-viral gene delivery with liposomes. Growing scientific evidence supports the involvement of polyanionic cell surface carbohydrates in cellular internalization of cationic liposomes. Syndecans, a highly conserved family of transmembrane heparan sulfate proteoglycans serve attachment sites for great variety of cationic ligands including growth factors, cytokines and even parasites. In the present study we quantitatively measured the contribution of various syndecan isoforms to liposome-mediated gene transfer. The obtained data show the superiority of syndecan-4, the ubiquitously expressed isoform of the syndecan family, in cellular uptake of liposomes. Applied mutational analysis demonstrated that gene delivery could be abolished by mutating the glycosaminoglycan attachment site of syndecans, highlighting the importance of polyanionic heparan sulfate side chains in the attachment of cationic liposomes. Blocking sulfation of syndecans also diminished gene delivery, a finding that confirms the essential role of polyanionic charges in binding cationic liposomes. Mutating other parts of the syndecan extracellular domain, including the cell-binding domain, had clearly smaller effect on liposome internalization. Mutational analyses also revealed that superiority of syndecan-4 in liposome-mediated gene delivery is significantly influenced by its cytoplasmic domain that orchestrates signaling pathways leading to macropinocytosis. In summary our study present a mechanistic insight into syndecan-mediated macropinocytic uptake of lipoplexes and highlights syndecan-4 as a superior target for cationic liposomes.

Intracellular Delivery of siRNA by Polycationic Superparamagnetic Nanoparticles

The siRNA transfection efficiency of nanoparticles (NPs), composed of a superparamagnetic iron oxide core modified with polycationic polymers (poly(hexamethylene biguanide) or branched polyethyleneimine), were studied in CHO-K1 and HeLa cell lines. Both NPs demonstrated to be good siRNA transfection vehicles, but unmodified branched polyethyleneimine (25 kD) was superior on both cell lines. However, application of an external magnetic field during transfection (magnetofection) increased the efficiency of the superparamagnetic NPs. Furthermore, our results reveal that these NPs are less toxic towards CHO-K1 cell lines than the unmodified polycationic-branched polyethyleneimine (PEI). In general, the external magnetic field did not alter the cell's viability nor it disrupted the cell membranes, except for the poly(hexamethylene biguanide)-modified NP, where it was observed that in CHO-K1 cells application of the external magnetic field promoted membrane damage. This paper presents new polycationic superparamagnetic NPs as promising transfection vehicles for siRNA and demonstrates the advantages of magnetofection.

A novel EGFR-targeted gene delivery system based on complexes self-assembled by EGF, DNA, and activated PAMAM dendrimers

Epidermal growth factor receptor (EGFR)-targeted gene delivery is a promising approach in gene therapy against EGFR-positive cancer. In addition, macromolecules, such as polyamidoamine (PAMAM) dendrimers, are potential nonviral gene carriers in this therapy because of their biocompatibility and modifiable features. To achieve the goal of selectively enhancing the transfection efficiency in EGFR-positive cancer cells, the researchers developed chemical approaches of EGF-dendrimer conjugate, which were effective but complicated. Studies on liposomes reveal that self-assembly is another effective but simpler approach in EGF modification. Moreover, properly activated PAMAM dendrimers exhibit higher transfection efficiency, but little research has been done on its ligand-modification. In this study, we developed and characterized a novel gene-delivery system based on activated EGF-dendriplexes, which is formed via self-assembly by EGF and complexes prepared by activated PAMAM dendrimer and plasmid DNA. Such complexes exhibit desired features compared to nonmodified or non-activated dendriplexes in vitro, including selective enhancement of transfection efficiency in EGFR-positive cells, decreased cytotoxicity, and low agonist effect. In vivo experimentation shows their EGFR-positive tumor targeted biodistribution and increased transfection efficiency at EGFR-positive tumors. Our results demonstrated that activated EGF-dendriplexes are safe and effective carriers for delivering gene drugs to EGFR-positive cells, which makes these complexes a promising targeted nonviral gene-delivery system for auxiliary cancer therapy.

Novel pH-sensitive cationic lipids with linear ortho ester linkers for gene delivery

In an effort to develop pH-sensitive lipoplexes for efficient gene delivery, we report three novel cationic lipids containing a linear ortho ester linker that conjugates either the headgroup (Type I) or one hydrocarbon chain (Type II) with the rest of the lipid molecule. The cationic lipids carry either an iodide or a chloride counterion. Compared to our previously reported cyclic ortho ester linker, the linear ortho ester linker facilitated the construction of cationic liposomes and lipoplexes with different helper lipids. The chloride counterion not only facilitated the hydration of the lipid films during liposome construction, but also enhanced the hydrolysis of the ortho ester linker in the lipoplexes. After incubation at endosomal pH 5.5, the Type I lipoplexes aggregated and destabilized the endosome-mimicking model liposomes, but not the Type II lipoplexes. The helper lipids (DOPE or cholesterol) of the lipoplexes enhanced the pH-sensitivity of the Type I lipoplexes. In CV-1 cells (monkey kidney fibroblast), the Type I ortho ester-based lipoplexes, especially those with the chloride counterion, significantly improved the gene transfection efficiency, in some cases by more than 100 fold, compared to their pH-insensitive counterparts consisting of DOTAP. The gene transfection efficiency of the ortho ester-based lipoplexes was well correlated with their rate of aggregation and membrane destabilization in response to the endosomal pH 5.5.

Antitumor effect of a generation 4 polyamidoamine dendrimer/cyclooxygenase-2 antisense oligodeoxynucleotide complex on breast cancer in vitro and in vivo

Cyclooxygenase (COX)-2 plays critical roles in tumorigenesis, tumor cell growth, and angiogenesis, and inhibiting the expression of COX-2 by gene therapy has showed promising prospects. Vectors are crucial for gene therapy. Polyamidoamine (PAMAM) dendrimers are one type of nano-vectors. In this study, we synthesized a generation 4 polyamidoamine (G4PAMAM) dendrimer/COX-2 antisense oligodeoxynucleotide complex (G4PAMAM/COX-2ASODN), determined the transfection rate of G4PAMAM/COX-2ASODN on cultured breast cancer cells, assessed the cell viability, cell cycle dynamics, and cell invasiveness after transfection, and investigated the effects of G4PAMAM/COX-2ASODN on the expression of COX-2 mRNA and protein and microvessel density (MVD) levels in the tumor tissues of a breast cancer nude mouse model. The results showed that G4PAMAM/COX-2ASODN had a high transfection rate, decreased the cell viability, induced apoptosis and G0/G1 cell cycle arrest, and suppressed cell invasiveness. After treatment with G4PAMAM/COX-2ASODN, the copy number of COX-2 mRNA and protein expression in the tumor tissue were decreased markedly, MVD in the tumor tissue was also decreased, and tumor growth was restrained (p<0. 05). We conclude that COX-2ASODN can be delivered into the cultured and transplanted breast cancer cells efficiently by G4PAMAM, can reduce the expression of COX-2 mRNA and protein, and can lower the MVD of tumor tissues. The G4PAMAM/COX-2ASODN complex has antitumor properties in vitro and in vivo.

Comparative study of the in vitro and in vivo characteristics of cationic and neutral liposomes

Neutral liposomes (NLP) exhibit preferential localization in solid tumors based on the enhanced permeation and retention (EPR) effect. Cationic liposomes (CLP) have a propensity for localizing in newly formed tumor vessels and they have a potentially enhanced antitumor effect. However, an increased amount of cationic lipids in liposomes also induces aggregation through electrostatic interactions between the liposomes and the anionic species in the circulation, which results in a reduced EPR effect. Consequently, it is important to investigate the characteristics of liposomes with different surface potentials in vitro to achieve an optimal intratumoral distribution and antitumor effect in vivo. In this study, the authors evaluated the characteristics of doxorubicin (DOX)-loaded NLPs, CLPs, polyethylene glycol (PEG)-modified NLPs (NLP-PEG), and PEGylated CLPs (CLP-PEG) (ie, encapsulation efficacy, zeta potential, size, membrane fluidity, aggregation in serum, and uptake of liposomes into rat aortic endothelial cells (RAECs)) to further understand their influences on the pharmacokinetics, biodistribution, and antitumor therapy in vivo. The results showed that increased amounts of cationic lipids resulted in severe liposome aggregation in the presence of serum, yet it did not alter the membrane fluidity to a large extent. The uptake of liposomes into RAECs, visualized by confocal fluorescence microscopy, confirmed the rapid uptake of CLP by the endothelial cells compared with NLP. However, the pharmacokinetics, biodistribution and anticancer efficacies of these liposomes in vivo revealed that the CLP with highly positive surface potentials exhibited reduced circulation times and poor distribution in tumors. The NLP-PEG exhibited the highest anticancer efficacy; CLP-PEG, the second highest; and CLP with the most positive surface potential, the lowest. These phenomena were mostly due to the rapid aggregation in serum and subsequent accumulation in the lungs upon the intravenous injection of the CLP. Caution should be exercised when chemotherapeutic drugs are loaded into CLP for tumor therapy.

Influence of cationic lipid composition on gene silencing properties of lipid nanoparticle formulations of siRNA in antigen-presenting cells

Lipid nanoparticles (LNPs) are currently the most effective in vivo delivery systems for silencing target genes in hepatocytes employing small interfering RNA. Antigen-presenting cells (APCs) are also potential targets for LNP siRNA. We examined the uptake, intracellular trafficking, and gene silencing potency in primary bone marrow macrophages (bmMΦ) and dendritic cells of siRNA formulated in LNPs containing four different ionizable cationic lipids namely DLinDAP, DLinDMA, DLinK-DMA, and DLinKC2-DMA. LNPs containing DLinKC2-DMA were the most potent formulations as determined by their ability to inhibit the production of GAPDH target protein. Also, LNPs containing DLinKC2-DMA were the most potent intracellular delivery agents as indicated by confocal studies of endosomal versus cytoplamic siRNA location using fluorescently labeled siRNA. DLinK-DMA and DLinKC2-DMA formulations exhibited improved gene silencing potencies relative to DLinDMA but were less toxic. In vivo results showed that LNP siRNA systems containing DLinKC2-DMA are effective agents for silencing GAPDH in APCs in the spleen and peritoneal cavity following systemic administration. Gene silencing in APCs was RNAi mediated and the use of larger LNPs resulted in substantially reduced hepatocyte silencing, while similar efficacy was maintained in APCs. These results are discussed with regard to the potential of LNP siRNA formulations to treat immunologically mediated diseases.

DODAB:monoolein-based lipoplexes as non-viral vectors for transfection of mammalian cells

DNA/Cationic liposome complexes (lipoplexes) have been widely used as non-viral vectors for transfection. Neutral lipids in liposomal formulation are determinant for transfection efficiency using these vectors. In this work, we studied the potential of monoolein (MO) as helper lipid for cellular transfection. Lipoplexes composed of pDNA and dioctadecyldimethylammonium bromide (DODAB)/1-monooleoyl-rac-glycerol (MO) at different molar ratios (4:1, 2:1 and 1:1) and at different cationic lipid/DNA ratios were investigated. The physicochemical properties of the lipoplexes (size, charge and structure), were studied by Dynamic Light Scattering (DLS), Zeta Potential (ζ) and cryo-transmission electron microscopy (cryo-TEM). The effect of MO on pDNA condensation and the effect of heparin and heparan sulphate on the percentage of pDNA release from the lipoplexes were also studied by Ethidium Bromide (EtBr) exclusion assays and electrophoresis. Cytotoxicity and transfection efficiency of these lipoplexes were evaluated using 293T cells and compared with the golden standard helper lipids 1,2-dioleoyl-sn-glycero-3-hosphoethanolamine (DOPE) and cholesterol (Chol) as well as with a commercial transfection agent (Lipofectamine™ LTX). The internalization of transfected fluorescently-labeled pDNA was also visualized using the same cell line. The results demonstrate that the presence of MO not only increases pDNA compactation efficiency, but also affects the physicochemical properties of the lipoplexes, which can interfere with lipoplex-cell interactions. The DODAB:MO formulations tested showed little toxicity and successfully mediated in vitro cell transfection. These results were supported by fluorescence microscopy studies, which illustrated that lipoplexes were able to access the cytosol and deliver pDNA to the nucleus. DODAB:MO-based lipoplexes were thus validated as non-toxic, efficient lipofection vectors for genetic modification of mammalian cells. Understanding the relation between structure and activity of MO-based lipoplexes will further strengthen the development of these novel delivery systems.

Exogenous and cell surface glycosaminoglycans alter DNA delivery efficiency of arginine and lysine homopeptides in distinctly different ways

Glycosaminoglycans (GAGs) expressed ubiquitously on the cell surface are known to interact with a variety of ligands to mediate different cellular processes. However, their role in the internalization of cationic gene delivery vectors such as liposomes, polymers, and peptides is still ambiguous and seems to be controlled by multiple factors. In this report, taking peptides as model systems, we show that peptide chemistry is one of the key factors that determine the dependence on cell surface glycosaminoglycans for cellular internalization and gene delivery. Arginine peptides and their complexes with plasmid DNA show efficient uptake and functional gene transfer independent of the cell surface GAGs. On the other hand, lysine peptides and complexes primarily enter through a GAG-dependent pathway. The peptide-DNA complexes also show differential interaction with soluble GAGs. In the presence of exogenous GAGs under certain conditions, arginine peptide-DNA complexes show increased transfection efficiency that is not observed with lysine. This is attributed to a change in the complex nature that ensures better protection of the compacted DNA in the case of arginine complexes, whereas the lysine complexes get destabilized under these conditions. The presence of a GAG coating also ensures better cell association of arginine complexes, resulting in increased uptake. Our results indicate that the role of both the cell surface and exogenous glycosaminoglycans in gene delivery is controlled by the nature of the peptide and its complex with DNA.