Post-pegylated lipoplexes are promising vehicles for gene delivery in RPE cells

Application of sphingolipid-based nanocarriers in drug delivery: an overview

Sphingolipids (SL) are well recognized for their cell signaling through extracellular and intracellular pathways. Based on chemistry different types of SL are biosynthesized in mammalian cells and have specific function in cellular activity. SL has an ampiphilic structure with have hydrophobic body attached to the polar head enables their use as a drug delivery agent in the form of nanocarriers. SL-based liposomes can improve the solubility of lipophilic drugs through host and drug complexes and are more stable than conventional liposomal formulations. Preclinical studies of SL nanocarriers are reported on topical delivery, oral delivery, ocular delivery, chemotherapeutic delivery, cardiovascular delivery and Alzheimer's disease. The commercial challenges and patents related to SL nanoformulations are highlighted in this article.

Engineered liposomes to deliver nucleic acid mimics in Escherichia coli

Antisense oligonucleotides (ASOs) composed of nucleic acid mimics (NAMs) monomers are considered as potential novel therapeutic drugs against bacterial infections. However, bacterial envelopes are generally impermeable to naked oligonucleotides. Herein, liposomes loaded with NAMs-modified oligonucleotides (LipoNAMs) were evaluated to deliver ASOs in Escherichia coli. Specifically, we tested several surface modifications that included methoxyPEG conjugated to different lipid anchors or modification of the PEG distal ends with maleimide groups and antibodies. MethoxyPEG coated LipoNAMs showed low delivery efficiency for most bacteria, but maleimide-functionalized PEG LipoNAMs were able to deliver ASOs to nearly half of the bacterial population. Conjugation of antibodies to maleimide-functionalized PEG LipoNAMs increased 1.3-fold the delivery efficiency, enhancing the selectivity towards E. coli and biocompatibility. This work demonstrated for the first time that the coupling of antibodies to PEGylated liposomes can significantly improve the delivery of ASOs in E. coli, which might bring alternative routes for the treatment of bacterial infections in the future.

Acute myocardial infarction therapy using calycosin and tanshinone co-loaded; mitochondrion-targeted tetrapeptide and cyclic arginyl-glycyl-aspartic acid peptide co-modified lipid-polymer hybrid nano-system: preparation, characterization, and anti myocardial infarction activity assessment

Acute myocardial infarction (AMI) is one of the most common ischemic heart diseases. However, lack of sufficient drug concentration (in the ischemic heart) is the major factor of treatment failure. It is urgent for researchers to engineer novel drug delivery systems to enhance the targeted delivery of cardioprotective agents. The aim of the present study was to investigate the anti-AMI ability of calycosin (CAL) and tanshinone (TAN) co-loaded; mitochondrion-targeted tetrapeptide (MTP) and cyclic arginyl-glycyl-aspartic acid (RGD) peptide co-modified nano-system.: We prepared CAL and TAN combined lipid-polymer hybrid nano-system, and RGD was modified to the system to achieve RGD-CAL/TAN NS. MTP-131 was conjugated with PEG and modified onto the nanoparticles to achieve dual ligands co-modified MTP/RGD-CAL/TAN NS. The physicochemical properties of nano-systems were characterized. The AMI therapy ability of the systems was investigated in AMI rats' model. The size of MTP/RGD-CAL/TAN NS was 170.2 ± 5.6 nm, with a surface charge of -18.9 ± 1.9 mV. The area under the curve (AUC) and blood circulation half-life (T_1/2) of MTP/RGD-CAL/TAN NS was 178.86 ± 6.62 μg·min/mL and 0.47 h, respectively. MTP/RGD-CAL/TAN NS exhibited the most significant infarct size reduction effect of 22.9%. MTP/RGD-CAL/TAN NS exhibited the highest heart accumulation and best infarct size reduction effect, which could be used as a promising system for efficient treatment of cardiovascular diseases.

Acute myocardial infarction therapy using calycosin and tanshinone co-loaded mitochondria targeted lipid-polymer hybrid nano-system: Preparation, characterization, and anti myocardial infarction activity assessment

BACKGROUND

Acute myocardial infarction (AMI) is one of the most common ischemic heart diseases. However, lack of sufficient drug concentrations in the ischemic heart may led to treatment failure. It is urgent for researchers to engineer novel drug delivery systems to enhance the targeted delivery of cardioprotective agents.

OBJECTIVE

The aim of the present study was to investigate the anti-AMI ability of calycosin (CAL) and tanshinone (TAN) co-loaded mitochondria targeted lipid-polymer hybrid nano-system.

METHODS

CAL and TAN combined lipid-polymer hybrid nano-systems were prepared and MTP-131 was conjugated with PEG and modified onto the nanoparticles to achieve MTP-CAL/TAN NS. The physicochemical properties of nano-systems were characterized, the AMI therapy ability of the systems was investigated in AMI rats' model.

RESULTS

The size of MTP-CAL/TAN NS was 168.7 ± 5.1 nm, with a surface charge of - 21.3 ± 2.3 mV. The area under the curve (AUC) and blood circulation half-life (T_1/2) of MTP-CAL/TAN NS was 178.86 ± 6.62 μg·min/mL and 0.47 h, respectively. MTP-CAL/TAN NS exhibited the most significant infarct size reduction effect of 23.9 %.

CONCLUSION

MTP-CAL/TAN NS exhibited the highest heart accumulation and best infarct size reduction effect, which could be used as a promising system for efficient treatment of cardiovascular diseases.

Hemiacetal-linked pH-sensitive PEG-lipids for non-viral gene delivery

Cationic lipid–DNA complexes containing a novel hemiacetal PEG-lipid for endosomal escape were characterized in terms of pH-response, stability, and biological activity.

Confinement of Metalloenzymes in PEGylated Liposomes to Formulate Colloidal Catalysts for Antioxidant Cascade

Antioxidant cascade reactions detoxifying reactive oxygen species are of significance to control oxidative stresses-triggered diseases. In the present work, the antioxidant catalysts were prepared through the confinement of dual metalloenzymes in liposomes. The amino groups of superoxide dismutase (SOD) were conjugated to the carboxyl groups-bearing liposomes encapsulated with the catalase (CAT) to formulate a spatially organized antioxidant reaction network. The activity of SOD and CAT in the liposomal system was evaluated in detail on the basis of the prolonged xanthine oxidase/xanthine reaction producing superoxide anion radicals (O₂̇^-) and hydrogen peroxide (H₂O₂) coupled with redox reactions of cytochrome c. The liposome-confined SOD and CAT molecules were clearly demonstrated to catalyze the sequential disproportionation of O₂̇^- and H₂O₂ at 25 °C in a potassium phosphate buffer solution (pH = 7.8) under moderate transfer resistance with respect to the intermediate product (H₂O₂) within the liposomes. Furthermore, the liposomal catalysts were modified with the poly(ethylene glycol) (PEG)-conjugated lipids with the molecular mass of the PEG moiety of about 5000 through the post-PEGylation approach. The mean hydrodynamic diameter of the PEGylated liposomal catalysts was 140-150 nm. The dual enzyme activity in liposomes and the thermal stability of the encapsulated CAT were practically unaffected by the PEGylation. The above liposome-based antioxidant catalysts are highly biocompatible, PEG-modifiable, and reactive, thereby making the catalysts potentially applicable to therapeutic materials exhibiting functionality similar to cellular peroxisomes.

Diabetic eye: associated diseases, drugs in clinic, and role of self-assembled carriers in topical treatment

Introduction: Diabetes is a pandemic disease that causes relevant ocular pathologies. Diabetic retinopathy, macular edema, cataracts, glaucoma, or keratopathy strongly impact the quality of life of the patients. In addition to glycemic control, intense research is devoted to finding more efficient ocular drugs and improved delivery systems that can overcome eye barriers. Areas covered: The aim of this review is to revisit first the role of diabetes in the development of chronic eye diseases. Then, commercially available drugs and new candidates in clinical trials are tackled together with the pros and cons of their administration routes. Subsequent sections deal with self-assembled drug carriers suitable for eye instillation combining patient-friendly administration with high ocular bioavailability. Performance of topically administered polymeric micelles, liposomes, and niosomes for the management of diabetic eye diseases is analyzed in the light of ex vivo and in vivo results and outcomes of clinical trials. Expert opinion: Self-assembled carriers are being shown useful for efficient delivery of not only a variety of small drugs but also macromolecules (e.g. antibodies) and genes. Successful design of drug carriers may offer alternatives to intraocular injections and improve the treatment of both anterior and posterior segments diabetic eye diseases.

Lipoplexes to Deliver Oligonucleotides in Gram-Positive and Gram-Negative Bacteria: Towards Treatment of Blood Infections

Bacterial resistance to antibiotics threatens the ability to treat life-threatening bloodstream infections. Oligonucleotides (ONs) composed of nucleic acid mimics (NAMs) able to inhibit essential genes can become an alternative to traditional antibiotics, as long as they are safely transported in human serum upon intravenous administration and they are carried across the multilayered bacterial envelopes, impermeable to ONs. In this study, fusogenic liposomes were considered to transport the ONs and promote their internalization in clinically relevant bacteria. Locked nucleic acids and 2′-OMethyl RNA were evaluated as model NAMs and formulated into DOTAP–DOPE liposomes followed by post-PEGylation. Our data showed a complexation stability between the post-PEGylated liposomes and the ONs of over 82%, during 24 h in native human serum, as determined by fluorescence correlation spectroscopy. Quantification by a lipid-mixing assay showed that liposomes, with and without post-PEGylation, fused with all bacteria tested. Such fusion promoted the delivery of a fraction of the ONs into the bacterial cytosol, as observed by fluorescence in situ hybridization and bacterial fractionation. In short, we demonstrated for the first time that liposomes can safely transport ONs in human serum and intracellularly deliver them in both Gram-negative and -positive bacteria, which holds promise towards the treatment of bloodstream infections.

Delivery of Oligonucleotides into Bacteria by Fusogenic Liposomes

Oligonucleotides able to hybridize bacterial RNA via in situ hybridization may potentially act as new antimicrobials, replacing antibiotics, and as fast in vivo diagnostic probes, outperforming current clinical methodologies. Nonetheless, oligonucleotides are not able to efficiently permeate the multi-layered bacterial envelope to reach their target RNA in the cytosol. Cationic fusogenic liposomes are here suggested as vehicles to enable the internalization of oligonucleotides in bacteria. Here, we describe the formulation of DOTAP-DOPE liposomes, their complexation with small negatively charged oligonucleotides, and the evaluation of the intracellular delivery of the oligonucleotides in bacteria. This strategy uncovers the potential of performing FISH in vivo for real-time detection and treatment of infections.

Antisense microRNA185 loaded liposome for efficient inhibition of the hepatic endogenous microRNA185 level

MicroRNA185 (miR185), an endogenous noncoding RNA with 23 nucleotides, is one of key posttranscriptional modulators of cholesterol metabolism in hepatic cells. The antisense inhibitor of miR185 (miR185i) could decrease cholesterol level in vivo, providing a promising agent for anti-atherosclerosis strategy. In this work, a novel LipomiR185i was constructed by thin film hydration method and post-PEGylation as DOPE: DOTAP: Chol: DSPE-PEG₂₀₀₀ at the molar ratio of 1:1:1:0.1 with a nitrogen-to-phosphate ratio of 3, through the optimization of three cationic lipids (DOTAP, DODMA and DLin-MC3-DMA), six helper lipids (PC-98T, HSPC, DOPE, DMPC, DPPC and DSPC), different amounts and incorporation approaches of DSPE-PEG₂₀₀₀ and nitrogen-to-phosphate ratio. LipomiR185i was characterized with a particle size of 174 ± 11 nm, a zeta potential of 7.0 ± 3.3 mV, high encapsulation efficiency and transfection activity. It could protect miR185i from the rapid degradation by nucleases in serum, enhance cellular uptake and promote lysosomal escape in HepG2 cells. LipomiR185i could accumulate in the liver and remain for at least two weeks. More importantly, LipomiR185i significantly down-regulated the hepatic endogenous miR185 level in vitro and in vivo without significant tissue damage at 14 mg⋅kg^-1. The construction of LipomiR185i provides a potential anti-atherosclerotic nanodrug as well as a platform for delivering small RNAs to the liver efficiently and safely.

Enhancement of Pancreatic Cancer Therapy Efficacy by Type-1 Matrix Metalloproteinase-Functionalized Nanoparticles for the Selective Delivery of Gemcitabine and Erlotinib

Purpose

Pancreatic cancer (PCa) is projected to become the second leading cause of cancer-related deaths by 2030. Gemcitabine (GEM) combined with erlotinib (ERL) have been approved by the FDA for locally advanced, unresectable or metastatic pancreatic cancer therapy since 2005. Type-1 matrix metalloproteinase (MT1-MMP) has been recognized as a critical mediator of several steps in PCa progression including activating TGF-β or releasing latent TGF-β from LTBP-1, resulting in increased collagen production and cleavage collagen.

Methods

In the present research, GEM and ERL co-loaded nanoparticles (GEM/ERL NPs) were prepared. A non-substrate MT1-MMP binding peptide was decorated onto the GEM/ERL NPs surface.

Results

M-M GEM/ERL NPs exhibited the highest uptake ability (67.65 ± 2.87%), longest half-life period, largest area under the curve, and the best tumor inhibition efficiency (69.81 ± 4.13%). The body weight, blood urine nitrogen (BUN), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) of the system were steady when tested in mice model.

Conclusion

In conclusion, M-M GEM/ERL NPs protected the drugs in the plasma, improved cellular uptake capacity, exhibited the most remarkable tumor cell inhibition ability, and showed the most efficient tumor growth inhibition capacity in vivo. M-M GEM/ERL NPs could be applied as an efficient and safe system for the synergistic combination chemotherapy of PCa.

Anti prostate cancer therapy: Aptamer-functionalized, curcumin and cabazitaxel co-delivered, tumor targeted lipid-polymer hybrid nanoparticles

Prostate cancer (PC) is the most common type of newly diagnosed malignancy in men. Combined chemotherapy has been shown to be an effective strategy for the treatment of PC therapy. Lipid-polymer hybrid nanoparticles (LPNs) are core-shell nanoparticles composed of a polymer core and a lipid shell, which are reported to provide significant advantages for combined PC therapy. This study synthesized an aptamer conjugated ligand and designed an aptamer-functionalized, curcumin (CUR) and cabazitaxel (CTX) co-delivered LPNs (APT-CUR/CTX-LPNs). APT-CUR/CTX-LPNs had a mean size of 121.3 ± 4.2 nm and a positive surface charge (23.5 ± 2.6 mV). Both CUR and CTX were sustained released from LPNs. Aptamer-functionalized APT-CUR/CTX-LPNs exhibited good cell inhibition ability, high tumor accumulation, and remarkable tumor inhibition efficiency at the drug ratio of 2:5 (CUR:CTX). The novel LPNs offers great promise for the double drugs delivery to the prostate cancer cells and tumor xenograft in vivo, showing the potential of synergistic combination therapy for prostate cancer.

A combinatorial library of biodegradable polyesters enables non-viral gene delivery to post-mitotic human stem cell-derived polarized RPE monolayers

Safe and effective delivery of DNA to post-mitotic cells, especially highly differentiated cells, remains a challenge despite significant progress in the development of gene delivery tools. Biodegradable polymeric nanoparticles (NPs) offer an array of advantages for gene delivery over viral vectors due to improved safety, carrying capacity, ease of manufacture, and cell-type specificity. Here we demonstrate the use of a high-throughput screening (HTS) platform to synthesize and screen a library of 148 biodegradable polymeric nanoparticles, successfully identifying structures that enable efficient transfection of human pluripotent stem cell differentiated human retinal pigment epithelial (RPE) cells with minimal toxicity. These NPs can deliver plasmid DNA (pDNA) to RPE monolayers more efficiently than leading commercially available transfection reagents. Novel synthetic polymers are described that enable high efficacy non-viral gene delivery to hard-to-transfect polarized human RPE monolayers, enabling gene loss- and gain-of-function studies of cell signaling, developmental, and disease-related pathways. One new synthetic polymer in particular, 3,3'-iminobis(N,N-dimethylpropylamine)-end terminated poly(1,5-pentanediol diacrylate-co-3 amino-1-propanol) (5-3-J12), was found to form self-assembled nanoparticles when mixed with plasmid DNA that transfect a majority of these human post-mitotic cells with minimal cytotoxicity. The platform described here can be utilized as an enabling technology for gene transfer to human primary and stem cell-derived cells, which are often fragile and resistant to conventional gene transfer approaches.

Role of Ceramides in Drug Delivery

Ceramides belong to the sphingolipid group of lipids, which serve as both intracellular and intercellular messengers and as regulatory molecules that play essential roles in signal transduction, inflammation, angiogenesis, and metabolic disorders such as diabetes, neurodegenerative diseases, and cancer cell degeneration. Ceramides also play an important structural role in cell membranes by increasing their rigidity, creating micro-domains (rafts and caveolae), and altering membrane permeability; all these events are involved in the cell signaling. Ceramides constitute approximately half of the lipid composition in the human skin contributing to barrier function as well as epidermal signaling as they affect both proliferation and apoptosis of keratinocytes. Incorporation of ceramides in topical preparations as functional lipids appears to alter skin barrier functions. Ceramides also appear to enhance the bioavailability of drugs by acting as lipid delivery systems. They appear to regulate the ocular inflammation signaling, and external ceramides have shown relief in the anterior and posterior eye disorders. Ceramides play a structural role in liposome formulations and enhance the cellular uptake of amphiphilic drugs, such as chemotherapies. This review presents an overview of the various biological functions of ceramides, and their utility in topical, oral, ocular, and chemotherapeutic drug delivery.

Cholesterol-rich lipid-mediated nanoparticles boost of transfection efficiency, utilized for gene editing by CRISPR-Cas9

Purpose: Gene therapy has become a promising remedy to treat disease by modifying the person's genes. The therapeutic potential of related tools such as CRISPR-Cas9 depends on the efficiency of delivery to the targeted cells. Numerous transfection reagents have been designed and lots of efforts have been devoted to develop carriers for this purpose. Therefore, the aim of the present study was to develop novel cholesterol-rich lipid-based nanoparticles to enhance transfection efficiency and serum stability. Materials and methods: We constructed two-, three- and four-component cationic liposomes (CLs) to evaluate the combined effect of cholesterol domain and DOPE (dioleoyl phosphatidylethanolamine), a fusogenic lipid, and the PEG (polyethylene glycol) moiety location inside or outside of the cholesterol domain on transfection efficiency and other properties of the particle. Lipoplex formation and pDNA (plasmid DNA) entrapment were assessed by gel retardation assay at different N/P ratios (3, 5, 7). Physicochemical characteristics, cytotoxicity, serum stability and endosomal escape capability of the lipoplexes were studied and transfection potential was measured by firefly luciferase assay. Next, HEK293 cell line stably expressing GFP was utilized to demonstrate the editing of a reporter through Cas9 and sgRNA plasmids delivery by the selected CL formula, which showed the highest transfection efficiency. Results: Among the designed CLs, the four-component formula [DOTAP (1,2-dioleoyl-3-trimethylammoniumpropane)/DOPE/cholesterol/Chol-PEG (cholesterol-polyethylene glycol)] showed the highest rate of transfection at N/P 3. Finally, transfection of Cas9/sgRNA by this formulation at N/P 3 resulted in 39% gene-editing efficiency to knockout GFP reporter. The results also show that this CL with no cytotoxicity effect can totally protect the plasmids from enzymatic degradation in serum. Conclusion: The novel PEGylated cholesterol domain lipoplex providing serum stability, higher transfection efficiency and endosomal release can be used for in vivo Cas9/sgRNA delivery and other future gene-therapy applications.

Nucleic acid delivery to differentiated retinal pigment epithelial cells using cell-penetrating peptide as a carrier

Nucleic acid delivery to the eye is a promising treatment strategy for many retinal disorders. In this manuscript, retinal gene delivery with non-coated and chondroitin sulphate (CS) coated amphipathic and cationic peptides was tested. The transfection and gene knockdown efficiencies were evaluated in different retinal pigment epithelial (RPE) cell models including both dividing and differentiated cells. In addition, the mobility of peptide-based gene delivery systems was examined in porcine vitreous by particle tracking analysis. The results indicate that amphipathic and cationic peptides are safe in vitro and are capable of high transgene expression and gene knockdown in dividing cells. We further demonstrate that incorporation of CS improves the efficiency of gene delivery of peptide-based systems. Most importantly, the transgene expression mediated by both non-coated and CS coated peptides was high in differentiated as well as in human primary RPE cells which are typically difficult to transfect. Coating of peptide-based gene delivery systems with CS improved diffusion in the vitreous and enhanced the stability of the polyplexes. The results indicate that a peptide-based system can be fine-tuned as a promising approach for retinal gene delivery.

Lactoferrin- and RGD-comodified, temozolomide and vincristine-coloaded nanostructured lipid carriers for gliomatosis cerebri combination therapy

PURPOSE

Glioblastoma multiforme (GBM) is the most common malignant brain tumor originating in the central nervous system in adults. Based on nanotechnology such as liposomes, polymeric nanoparticles, and lipid nanoparticles, recent research efforts have been aimed to target drugs to the brain.

METHODS

In this study, lactoferrin- and arginine-glycine-aspartic acid (RGD) dual- ligand-comodified, temozolomide and vincristine-coloaded nanostructured lipid carriers (L/RT/V-NLCs) were introduced for GBM combination therapy. The physicochemical properties of L/R-T/V-NLCs such as particle size, zeta potential, and encapsulated efficiency are measured. The drug release profile, cellular uptake, cytotoxicity, tissue distribution, and antitumor activity of L/R-T/V-NLCs are further investigated in vitro and in vivo.

RESULTS

L/R-T/V-NLCs were stable with nanosize and high drug encapsulation efficiency. L/R-T/V-NLCs exhibited sustained-release behavior, high cellular uptake, high cytotoxicity and synergy effects, increased drug accumulation in the tumor tissue, and obvious tumor inhibition efficiency with low systemic toxicity.

CONCLUSION

L/R-T/V-NLCs could be a promising drug delivery system for glioblastoma chemotherapy.

Dynamically PEGylated and Borate-Coordination-Polymer-Coated Polydopamine Nanoparticles for Synergetic Tumor-Targeted, Chemo-Photothermal Combination Therapy

Multifunctional nanomaterials with efficient tumor-targeting and high antitumor activity are highly anticipated in the field of cancer therapy. In this work, a synergetic tumor-targeted, chemo-photothermal combined therapeutic nanoplatform based on a dynamically PEGylated, borate-coordination-polymer-coated polydopamine nanoparticle (PDA@CP-PEG) is developed. PEGylation on the multifunctional nanoparticles is dynamically achieved via the reversible covalent interaction between the surface phenylboronic acid (PBA) group and a catechol-containing poly(ethylene glycol) (PEG) molecule. Due to the acid-labile PBA/catechol complex and the weak-acid-stable PBA/sialic acid (SA) complex, the nanoparticles can exhibit a synergetic targeting property for the SA-overexpressed tumor cells, i.e., the PEG-caused "passive targeting" and PBA-triggered "active targeting" under the weakly acidic tumor microenvironment. In addition, the photothermal effect of the polydopamine core and the doxorubicin-loading capacity of the porous coordination polymer layer endow the nanoparticles with the potential for chemo-photothermal combination therapy. As expected, the in vitro and in vivo studies both verify that the multifunctional nanoparticles possess relatively lower systematic toxicity, efficient tumor targeting ability, and excellent chemo-photothermal activity for tumor inhibition. It is believed that these multifunctional nanoparticles with synergetic tumor targeting property and combined therapeutic strategies would provide an insight into the design of a high-efficiency antitumor nanoplatform for potential clinical applications.

An efficient PEGylated gene delivery system with improved targeting: Synergism between octaarginine and a fusogenic peptide

Because of their ability to translocate different cargos into cells, arginine-rich cell penetrating peptides (CPPs) are promising vehicles for drug and gene delivery. The use of CPP-based carriers, however, is hampered by the lack of specificity and by interactions with negative serum components. Polyethylene glycol (PEG) is used to decrease such non-specific interactions, albeit its use is associated with reduced transfection efficiency. In this study, we describe the development of PEGylated CPP-based gene carrier with an improved targeting and a high transfection activity. The system was prepared by condensing DNA with a polycation followed by coating with a lipid envelope containing the octaarginine (R8) peptide as a model CPP. R8-modified nanoparticles produced high transfection activities, but the efficiency was reduced by PEG shielding. The reduced activity could be fully restored by the addition of a targeting ligand and a pH-sensitive fusogenic peptide. The efficiency of the proposed system is quite high, even in the presence of serum, and shows improved targeting and selectivity. Surprisingly, the effect of the fusogenic peptide was dramatically reduced in the absence of R8. Although shielded, R8 augmented the activity of the fusogenic peptide, suggesting a synergistic effect between the two peptides at the intracellular level.

EGFR Targeting and Shielding of pDNA Lipopolyplexes via Bivalent Attachment of a Sequence-Defined PEG Agent

For successful nonviral gene delivery, cationic polymers are promising DNA carrier, which need to comprise several functionalities. The current work focuses on the postincorporation of epidermal growth factor receptor (EGFR) targeted PEGylation agents onto lipopolyplexes for pDNA delivery. T-shaped lipo-oligomers are previously found to be effective sequence-defined carriers for pDNA and siRNA. Here, the bis-oleoyl-oligoaminoethanamide 454 containing tyrosine trimer-cysteine ends is applied for complex formation with pDNA coding for luciferase or sodium iodide symporter (NIS). In a second step, the lipopolyplexes are modified via disulfide formation with sequence-defined monovalent or bivalent PEGylation agents containing one or two 3-nitro-2-pyridinesulfenyl (NPys)-activated cysteines, respectively. For targeting, the polyethylene glycol (PEG) agents comprise the EGFR targeting peptide GE11. In comparison of all transfection complexes, 454 lipopolyplexes modified with the bidentate PEG-GE11 agent show the best, EGFR-dependent uptake as well as luciferase and NIS gene expression into receptor-positive tumor cells.

Intracellular delivery of oligonucleotides in Helicobacter pylori by fusogenic liposomes in the presence of gastric mucus

The rising antimicrobial resistance contributes to 25000 annual deaths in Europe. This threat to the public health can only be tackled if novel antimicrobials are developed, combined with a more precise use of the currently available antibiotics through the implementation of fast, specific, diagnostic methods. Nucleic acid mimics (NAMs) that are able to hybridize intracellular bacterial RNA have the potential to become such a new class of antimicrobials and additionally could serve as specific detection probes. However, an essential requirement is that these NAMs should be delivered into the bacterial cytoplasm, which is a particular challenge given the fact that they are charged macromolecules. We consider these delivery challenges in relation to the gastric pathogen Helicobacter pylori, the most frequent chronic infection worldwide. In particular, we evaluate if cationic fusogenic liposomes are suitable carriers to deliver NAMs across the gastric mucus barrier and the bacterial envelope. Our study shows that DOTAP-DOPE liposomes post-PEGylated with DSPE-PEG (DSPE Lpx) can indeed successfully deliver NAMs into Helicobacter pylori, while offering protection to the NAMs from binding and inactivation in gastric mucus isolated from pigs. DSPE Lpx thus offer exciting new possibilities for in vivo diagnosis and treatment of Helicobacter pylori infections.

Surface De-PEGylation Controls Nanoparticle-Mediated siRNA Delivery In Vitro and In Vivo

The present work proposes a unique de-PEGylation strategy for controllable delivery of small interfering RNA (siRNA) using a robust lipid-polymer hybrid nanoparticle (NP) platform. The self-assembled hybrid NPs are composed of a lipid-poly(ethylene glycol) (lipid-PEG) shell and a polymer/cationic lipid solid core, wherein the lipid-PEG molecules can gradually dissociate from NP surface in the presence of serum albumin. The de-PEGylation kinetics of a series of different lipid-PEGs is measured with their respective NPs, and the NP performance is comprehensively investigated in vitro and in vivo. This systematic study reveals that the lipophilic tails of lipid-PEG dictate its dissociation rate from NP surface, determining the uptake by tumor cells and macrophages, pharmacokinetics, biodistribution, and gene silencing efficacy of these hybrid siRNA NPs. Based on our observations, we here propose that lipid-PEGs with long and saturated lipophilic tails might be required for effective siRNA delivery to tumor cells and gene silencing of the lipid-polymer hybrid NPs after systemic administration.

Polarized, Cobblestone, Human Retinal Pigment Epithelial Cell Maturation on a Synthetic PEG Matrix

Cell attachment is essential for the growth and polarization of retinal pigment epithelial (RPE) cells. Currently, surface coatings derived from biological proteins are used as the gold standard for cell culture. However, downstream processing and purification of these biological products can be cumbersome and expensive. In this study, we constructed a library of chemically modified nanofibers to mimic the Bruch's membrane of the retinal pigment epithelium. Using atmospheric-pressure plasma-induced graft polymerization with a high-throughput screening platform to modify the nanofibers, we identified three polyethylene glycol (PEG)-grafted nanofiber surfaces (PEG methyl ether methacrylate, n = 4, 8, and 45) from a library of 62 different surfaces as favorable for RPE cell attachment, proliferation, and maturation in vitro with cobblestone morphology. Compared with the biologically derived culture matrices such as vitronectin-based peptide Synthemax, our newly discovered synthetic PEG surfaces exhibit similar growth and polarization of retinal pigment epithelial (RPE) cells. However, they are chemically defined, are easy to synthesize on a large scale, are cost-effective, are stable with long-term storage capability, and provide a more physiologically accurate environment for RPE cell culture. To our knowledge, no one has reported that PEG derivatives directly support attachment and growth of RPE cells with cobblestone morphology. This study offers a unique PEG-modified 3D cell culture system that supports RPE proliferation, differentiation, and maturation with cobblestone morphology, providing a new avenue for RPE cell culture, disease modeling, and cell replacement therapy.

Efficient gene delivery to primary human retinal pigment epithelial cells: The innate and acquired properties of vectors

The purpose of this study is designing non-viral gene delivery vectors for transfection of the primary human retinal pigment epithelial cells (RPE). In the design process of gene delivery vectors, considering physicochemical properties of vectors alone does not seem to be enough since they interact with constituents of the surrounding environment and hence gain new characteristics. Moreover, due to these interactions, their cargo can be released untimely or undergo degradation before reaching to the target cells. Further, the characteristics of cells itself can also influence the transfection efficacy. For example, the non-dividing property of RPE cells can impede the transfection efficiency which in most studies was ignored by using immortal cell lines. In this study, vectors with different characteristics differing in mixing orders of pDNA, PEI polymer, and PLGA/PEI or PLGA nanoparticles were prepared and characterized. Then, their characteristics and efficacy in gene delivery to RPE cells in the presence of vitreous or fetal bovine serum (FBS) were evaluated. All formulations showed no cytotoxicity and were able to protect pDNA from premature release and degradation in extracellular media. Also, the adsorption of vitreous or serum proteins onto the surface of vectors changed their properties and hence cellular uptake and transfection efficacy.

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.

Stealth monoolein-based nanocarriers for delivery of siRNA to cancer cells

While the delivery of small interfering RNAs (siRNAs) is an attractive strategy to treat several clinical conditions, siRNA-nanocarriers' stability after intravenous administration is still a major obstacle for the development of RNA-interference based therapies. But, although the need for stability is well recognized, the notion that strong stabilization can decrease nanocarriers' efficiency is sometimes neglected. In this work we evaluated two stealth functionalization strategies to stabilize the previously validated dioctadecyldimethylammonium bromide (DODAB):monoolein (MO) siRNA-lipoplexes. The nanocarriers were pre- and post-pegylated, forming vectors with different stabilities in biological fluids. The stealth nanocarriers' behavior was tested under biological mimetic conditions, as the production of stable siRNA-lipoplexes is determinant to achieve efficient intravenous siRNA delivery to cancer cells. Upon incubation in human serum for 2h, by fluorescence Single Particle Tracking microscopy, PEG-coated lipoplexes were found to have better colloidal stability as they could maintain a relatively stable size. In addition, using fluorescence fluctuation spectroscopy, post-pegylation also proved to avoid siRNA dissociation from the nanocarriers in human serum. Concomitantly it was found that PEG-coated lipoplexes improved cellular uptake and transfection efficiency in H1299 cells, and had the ability to silence BCR-ABL, affecting the survival of K562 cells. Based on an efficient cellular internalization, good silencing effect, good siRNA retention and good colloidal stability in human serum, DODAB:MO (2:1) siRNA-lipoplexes coated with PEG-Cer are considered promising nanocarriers for further in vivo validation.

STATEMENT OF SIGNIFICANCE

This work describes two stealth functionalization strategies for the stabilization of the previously validated dioctadecyldimethylammonium bromide (DODAB):monoolein (MO) siRNA-lipoplexes. These nanocarriers are capable of efficiently incorporating and delivering siRNA molecules to cells in order to silence genes whose expression is implicated in a pathological condition. The main objective was to functionalize these nanocarriers with a coating conferring protection to siRNA in blood without compromising its efficient delivery to cancer cells, validating the potential of DODAB:MO (2:1) siRNA-lipoplexes as therapeutic vectors. We show that the stealth strategy is determinant to achieve a stable and efficient nanocarrier, and that DODAB:MO mixtures have a very promising potential for systemic siRNA delivery to leukemic cells.

Surface modification of nonviral nanocarriers for enhanced gene delivery

Biomedical nanotechnology has given a new lease of life to gene therapy with the ever-developing and ever-diversifying nonviral gene delivery nanocarriers. These are designed to pass a series of barriers in order to bring their nucleic acid cargo to the right subcellular location of particular cells. For a given application, each barrier has its dedicated strategy, which translates into a physicochemical, biological and temporal identity of the nanocarrier surface. Different strategies have thus been explored to implement adequate surface identities on nanocarriers over time for systemic delivery. In that context, this review will mainly focus on organic nanocarriers, for which these strategies will be described and discussed.

PEGylated and non-PEGylated siRNA lipoplexes formulated with cholesteryl cytofectins promote efficient luciferase knockdown in HeLa tat luc cells

Delivery of small interfering RNAs (siRNAs) remains a major challenge in their development for therapeutic applications, and cationic liposomes are being actively investigated for this purpose. Six liposome formulations containing the cytofectins 3β[N-(N ',N '-dimethylaminopropane)-carbamoyl] cholesterol (Chol-T) or 3β[N-(N ',N ',-dimethylaminopropylsuccinamidohydrazido)-carbamoyl] cholesterol (MS09) and varying amounts of distearoylphosphatidylethanolamine poly(ethylene glycol)2000, were prepared. Lipoplexes formed with siRNA were characterized by gel retardation analysis and cryo-electron microscopy. All lipoplexes exhibited low cytotoxicity in the HeLa tat luc cell line while Chol-T lipoplexes, containing anti-luciferase siRNA, achieved 93.4% knockdown of the luciferase transcript at 30 nM siRNA. Poly(ethylene glycol)2000 incorporation only marginally reduced knockdown efficiency.

Correlation of dual colour single particle trajectories for improved detection and analysis of interactions in living cells

Interactions between objects inside living cells are often investigated by looking for colocalization between fluorescence microscopy images that are recorded in separate colours corresponding to the fluorescent label of each object. The fundamental limitation of this approach in the case of dynamic objects is that coincidental colocalization cannot be distinguished from true interaction. Instead, correlation between motion trajectories obtained by dual colour single particle tracking provides a much stronger indication of interaction. However, frequently occurring phenomena in living cells, such as immobile phases or transient interactions, can limit the correlation to small parts of the trajectories. The method presented here, developed for the detection of interaction, is based on the correlation inside a window that is scanned along the trajectories, covering different subsets of the positions. This scanning window method was validated by simulations and, as an experimental proof of concept, it was applied to the investigation of the intracellular trafficking of polymeric gene complexes by endosomes in living retinal pigment epithelium cells, which is of interest to ocular gene therapy.

Dendrimers for gene delivery – a potential approach for ocular therapy?

Objectives

A vast number of blinding diseases have genetic aetiologies and may be treated by molecular based therapies such as antisense oligonucleotides or short interfering RNA. However, treatment success of ocular gene therapy is highly dependent on efficient delivery of such molecules.

Key findings

The majority of clinical studies for ocular gene therapy utilize viral vectors. While these have proven highly efficient, they show limited loading capacity and pose significant safety risks owing to their oncogenic and immunogenic effects. Non-viral gene carriers have emerged as a promising alternative with dendrimers providing great potential for gene therapy because of their size, shape and high density of modifiable surface groups. However, while dendrimers have been used extensively for drug and gene delivery to other organs, only a few studies have been reported on the eye.

Summary

This review focuses on the development of dendrimers for gene delivery with special emphasis on ocular gene therapy. Different synthesis approaches and types of dendrimers are discussed. Ocular gene therapy targets are highlighted with an overview of current clinical studies. The use of dendrimers in ocular gene delivery in comparison to liposomes and nanoparticles is also discussed. Finally, future prospects of tailored multifunctional dendrimers for ocular gene therapy are highlighted.

Cytofectin amine head group modification and degree of liposome pegylation: factors influencing gene transfer

The effectiveness of liposome-mediated gene transfer methods hinges, in part, on the nature of the interaction between the DNA cargo and the liposomes. Here we have examined the effect of quaternization of the cytofectin cationic head group on this interaction and the effect of concentration of the biocompatible, protective polymer polyethylene glycol₂₀₀₀ (PEG₂₀₀₀) on transfection activity. Thus 3β[N-(N’,N’-dimethylaminopropane)-carbamoyl] cholesterol (Chol-T) and 3β[N-(N’,N’,N’-trimethylammonium propane)-carbamoyl] cholesterol iodide (Chol-Q), differing only in the degree of head group methylation, have been formulated into liposomes with polyethylene glycol₂₀₀₀-distearoylphosphatidyl ethanolamine (DSPE PEG₂₀₀₀) and the neutral co-lipid dioleoylphosphatidylethanolamine (DOPE). Their DNA-binding characteristics have been determined and the gene transfer capabilities of resulting lipoplexes have been examined in HEK 293 human embryonic kidney cells. Quaternary ammonium Chol-Q liposomes were found to bind DNA more avidly than their tertiary amine Chol-T counterparts. The inclusion of PEG₂₀₀₀ in liposome formulations resulted in an increase in the optimal liposome-DNA binding ratio. Chol-T liposomes promoted transgene activity levels 5 times greater than those obtained with Chol-Q lipoplexes. Furthermore, a drop in transfection activity of only 17% was noted on increase of liposome pegylation from 2 to 5 mole percent. The study's findings suggest that strong association between cationic liposomes and DNA may lead to reduced levels of transfection activity as a result of poor release of nucleic acid after cellular uptake.

Comparison of two kinds of nanomedicine for targeted gene therapy: premodified or postmodified gene delivery systems

BACKGROUND

The applications of ligand-polyethylene glycol (PEG)-modified nanocarriers have now emerged, as well as recognized strategies to provide the vectors with active targeting properties. In this research, premodification and postmodification were compared using the same ligand, ie, a novel conjugated mannan-containing PEG and L-α-phosphatidylethanolamine (PE).

METHODS

Premodified and postmodified solid lipid nanoparticles were prepared and the characteristics of the two kinds of vehicles were evaluated. The modified vectors were then administered intravenously to rats and the in vivo targeting behavior of the complexes was investigated in liver macrophages.

RESULTS

By carefully formulating the carriers with an optimal ratio of mannan-containing PEG-PE, postmodified vehicles displayed more efficient gene expression in rat Kupffer cells both in vitro and in vivo.

CONCLUSION

Postmodified gene carriers are superior to premodified gene vectors, although the latter is also promising for targeted gene delivery. This discovery could guide our future research.

Nano-vectors for the Ocular Delivery of Nucleic Acid-based Therapeutics

Nucleic acid-based therapeutics have gained a lot of interest for the treatment of diverse ophthalmic pathologies. The first to enter in clinic has been an oligonucleotide, Vitravene^® for the treatment of cytomegalovirus infection. More recently, research on aptamers for the treatment of age related macular degeneration has led to the development of Macugen^®. Despite intense potential, effective ocular delivery of nucleic acids is a major challenge since therapeutic targets for nucleic acid-based drugs are mainly located in the posterior eye segment, requiring repeated invasive administration. Of late, nanotechnology-based nano-vectors have been developed in order to overcome the drawbacks of viral and other non-viral vectors. The diversity of nano-vectors allows for ease of use, flexibility in application, low-cost of production, higher transfection efficiency and enhanced genomic safety. Using nano-vector strategies, nucleic acids can be delivered either encapsulated or complexed with cationic lipids, polymers or peptides forming sustained release systems, which can be tailored according to the ocular tissue being targeted. The present review focuses on developments and advances in various nano-vectors for the ocular delivery of nucleic acid-based therapeutics, the barriers that such delivery systems face and methods to overcome them.

Enhanced delivery of monomethoxypoly(ethylene glycol)-poly(lactic-co-glycolic acid)-poly l-lysine nanoparticles loading platelet-derived growth factor BB small interfering RNA by ultrasound and/or microbubbles to rat retinal pigment epithelium cells

BACKGROUND

A novel small interfering RNA (siRNA) delivery method based on the combined use of nanoparticles (NPs) with ultrasound (US) and/or microbubbles (MBs) was introduced in the present study. We investigated the efficacy and safety of US and/or MBs-enhanced delivery of monomethoxypoly(ethylene glycol)-poly(lactic-co-glycolic acid)-poly l-lysine (mPEG-PLGA-PLL) NPs loading platelet-derived growth factor BB (PDGF-BB) siRNA to rat retinal pigment epithelium (RPE)-J cells.

METHODS

The effect of US and/or MBs on the delivery of NPs containing Cy3-labeled siRNA was evaluated by fluorescence microscopy and flow cytometry. Potential toxicity of NPs and cell viability under different conditions of US and/or MBs were assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method.

RESULTS

The results obtained showed that low intensity US or 15-20% MBs could increase the delivery efficiency of a lower concentration of mPEG-PLGA-PLL NPs loading siRNA to RPE-J cells, whereas the combination of US with MBs under the optimal conditions for the enhancement of NPs delivery did not further increase the cellular uptake of NPs compared to either US or MBs alone (p = 0.072 and p = 0.488, respectively). Under the optimal condition for US-enhanced NPs delivery, the enhanced PDGF-BB gene silencing with a combination of US and NPs encapsulating siRNA resulted in a significant decrease of mRNA and protein expression levels compared to NPs alone.

CONCLUSIONS

US and/or MBs could be used safely to enhance the delivery of NPs loading siRNA to rat RPE-J cells. A combination of the chemical (mPEG-PLGA-PLL NPs loading siRNA) and physical (US) approaches could more effectively downregulate the mRNA and protein expression of PDGF-BB.

Can ultrasound solve the transport barrier of the neural retina?

PURPOSE

Intravitreal injection of nonviral gene complexes may be promising in the treatment of retinal diseases. This study investigates the permeation of lipoplexes and polystyrene nanospheres through the neural retina and their uptake by the retinal pigment epithelium (RPE) either with or without ultrasound application.

MATERIALS AND METHODS

Anterior parts and vitreous of bovine eyes were removed. The neural retina was left intact or peeled away from the RPE. (Non)pegylated lipoplexes and pegylated nanospheres were applied. After 2 h incubation, the RPE cells were detached and analyzed for particle uptake by flow cytometry and confocal microscopy.

RESULTS

The neural retina is a significant transport barrier for pegylated nanospheres and (non)pegylated lipoplexes. Applying ultrasound improved the permeation of the nanoparticles up to 130 nm.

CONCLUSIONS

Delivery of liposomal DNA complexes to the RPE cells is strongly limited by the neural retina. Ultrasound energy may be a useful tool to improve the neural retina permeability, given the nucleic acid carriers are small enough. Our results underline the importance to design and develop very small carriers for the delivery of nucleic acids to the neural retina and the RPE after intravitreal injection.