Liposome encapsulated polyethylenimine/ODN polyplexes for brain targeting

CNS Delivery of Nucleic Acid Therapeutics: Beyond the Blood-Brain Barrier and Towards Specific Cellular Targeting

Nucleic acid-based therapeutic molecules including small interfering RNA (siRNA), microRNA(miRNA), antisense oligonucleotides (ASOs), messenger RNA (mRNA), and DNA-based gene therapy have tremendous potential for treating diseases in the central nervous system (CNS). However, achieving clinically meaningful delivery to the brain and particularly to target cells and sub-cellular compartments is typically very challenging. Mediating cell-specific delivery in the CNS would be a crucial advance that mitigates off-target effects and toxicities. In this review, we describe these challenges and provide contemporary evidence of advances in cellular and sub-cellular delivery using a variety of delivery mechanisms and alternative routes of administration, including the nose-to-brain approach. Strategies to achieve subcellular localization, endosomal escape, cytosolic bioavailability, and nuclear transfer are also discussed. Ultimately, there are still many challenges to translating these experimental strategies into effective and clinically viable approaches for treating patients.

Antibody-Targeted Liposomes for Enhanced Targeting of the Blood-Brain Barrier

The blood-brain barrier (BBB) hinders therapeutic delivery to the central nervous system (CNS), thereby impeding the development of therapies for brain injury and disease. Receptor-mediated transcytosis (RMT) systems are a promising way to shuttle a targeted therapeutic into the brain. Here, we developed and evaluated an RMT antibody-targeted liposomal system. A previously identified antibody, scFv46.1, that binds to the human and murine BBB and can pass through the murine BBB by transcytosis after intravenous injection was used to decorate the surface of liposomes. Using an in vitro BBB model, we demonstrated the cellular uptake of scFv46.1-modified liposomes (46.1-Lipo). Next, the biodistribution and brain uptake capacity of 46.1-targeted liposomes were assessed after intravenous administration. Our results showed that 46.1-Lipo can lead to increased brain accumulation through targeting of the brain vasculature. Initial rate pharmacokinetic experiments and biodistribution analyses indicated that 46.1-Lipo loaded with pralidoxime exhibited a 10-fold increase in brain accumulation compared with a mock-targeted liposomal group, and this increased accumulation was brain-specific. These studies indicate the potential of this 46.1-Lipo system as a synthetic vehicle for the targeted transport of therapeutic molecules into the CNS.

Polyethyleneimine-Based Lipopolyplexes as Carriers in Anticancer Gene Therapies

Recent years have witnessed rapidly growing interest in application of gene therapies for cancer treatment. However, this strategy requires nucleic acid carriers that are both effective and safe. In this context, non-viral vectors have advantages over their viral counterparts. In particular, lipopolyplexes—nanocomplexes consisting of nucleic acids condensed with polyvalent molecules and enclosed in lipid vesicles—currently offer great promise. In this article, we briefly review the major aspects of developing such non-viral vectors based on polyethyleneimine and outline their properties in light of anticancer therapeutic strategies. Finally, examples of current in vivo studies involving such lipopolyplexes and possibilities for their future development are presented.

Recent Advances in the Delivery Carriers and Chemical Conjugation Strategies for Nucleic Acid Drugs

With the development of new anticancer medicines, novel modalities are being explored for cancer treatment. For many years, conventional modalities, such as small chemical drugs and antibody drugs, have worked by "inhibiting the function" of target proteins. In recent years, however, nucleic acid drugs, such as ASOs and siRNAs, have attracted attention as a new modality for cancer treatment because nucleic acid drugs can directly promote the "loss of function" of target genes. Recently, nucleic acid drugs for use in cancer therapy have been extensively developed and some of them have currently been under investigation in clinical trials. To develop novel nucleic acid drugs for cancer treatment, it is imperative that cancer researchers, including ourselves, cover and understand those latest findings. In this review, we introduce and provide an overview of various DDSs and ligand modification technologies that are being employed to improve the success and development of nucleic acid drugs, then we also discuss the future of nucleic acid drug developments for cancer therapy. It is our belief this review will increase the awareness of nucleic acid drugs worldwide and build momentum for the future development of new cancer-targeted versions of these drugs.

Lipodendriplexes mediated enhanced gene delivery: a cellular to pre-clinical investigation

Clinical success of effective gene therapy is mainly hampered by the insufficiency of safe and efficient internalization of a transgene to the targeted cellular site. Therefore, the development of a safe and efficient nanocarrier system is one of the fundamental challenges to transfer the therapeutic genes to the diseased cells. Polyamidoamine (PAMAM) dendrimer has been used as an efficient non-viral gene vector (dendriplexes) but the toxicity and unusual biodistribution induced by the terminal amino groups (–NH₂) limit its in vivo applications. Hence, a state of the art lipid modification with PAMAM based gene carrier (lipodendriplexes) was planned to investigate theirs in vitro (2D and 3D cell culture) and in vivo behaviour. In vitro pDNA transfection, lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) generation, cellular protein contents, live/dead staining and apoptosis were studied in 2D cell culture of HEK-293 cells while GFP transfection, 3D cell viability and live/dead staining of spheroids were performed in its 3D cell culture. Acute toxicity studies including organ to body index ratio, hematological parameters, serum biochemistry, histopathological profiles and in vivo transgene expression were assessed in female BALB/c mice. The results suggested that, in comparison to dendriplexes the lipodendriplexes exhibited significant improvement of pDNA transfection (p < 0.001) with lower LDH release (p < 0.01) and ROS generation (p < 0.05). A substantially higher cellular protein content (p < 0.01) and cell viability were also observed in 2D culture. A strong GFP expression with an improved cell viability profile (p < 0.05) was indicated in lipodendriplexes treated 3D spheroids. In vivo archives showed the superiority of lipid-modified nanocarrier system, depicted a significant increase in green fluorescent protein (GFP) expression in the lungs (p < 0.01), heart (p < 0.001), liver (p < 0.001) and kidneys (p < 0.001) with improved serum biochemistry and hematological profile as compared to unmodified dendriplexes. No tissue necrosis was evident in the animal groups treated with lipid-shielded molecules. Therefore, a non-covalent conjugation of lipids with PAMAM based carrier system could be considered as a promising approach for an efficient and biocompatible gene delivery system.

PEGylated nanocarriers: A promising tool for targeted delivery to the brain

Targeted drug delivery across the blood-brain barrier is an extremely challenging quest in the fight with fatal brain ailments, with the major hurdles being short circulation time, reticuloendothelial system (RES) uptake, and excretion of nanocarriers. PEGylation has emerged as a boon for targeted drug delivery to the brain. It is well established that PEGylation can increase the circulation time of nanocarriers by avoiding RES uptake, which is indispensable for increasing the brain's uptake of nanocarriers. PEGylation also acts as a linker for ligand molecules to achieve active targeting to the brain. Using PEGylation, novel approaches are being investigated to facilitate ligand-receptor interactions at the brain endothelium to ease the entry of therapeutic drugs into the brain. In addition, PEGylation made it simpler to assess the brain tissue for delivering diagnostic molecules and theranostic nanocarriers. The potential of PEGylated nanocarriers is being investigated vastly to boost the therapeutic effect several fold in the treatment of brain diseases. This review sheds light on the contribution of PEGylated nanocarriers, especially liposomes, polymeric nanoparticles, and dendrimers for brain-specific delivery of bioactives.

Enhanced Subcellular Trafficking of Resveratrol Using Mitochondriotropic Liposomes in Cancer Cells

Mitochondria are membrane-enclosed organelles present in most eukaryotic cells, described as “power houses of the cell”. The mitochondria can be a target for inducing cancer cell death and for developing strategies to bypass multi drug resistance (MDR) mechanisms. 4-Carboxybutyl triphenylphosphonium bromide-polyethylene glycol-distearoylphosphatidylethanolamine (TPP-DSPE-PEG) and dequalinium-polyethylene glycol-distearoylphosphatidylethanolamine (DQA-DSPE-PEG) were synthesized as mitochondriotropic molecules. Mitochondria-targeting liposomes carrying resveratrol were constructed by modifying the liposome’s surface with TPP-PEG or DQA-PEG, resulting in TLS (Res) and DLS (Res), respectively, with the aim to obtain longer blood circulation and enhanced permeability and retention (EPR). Both TLS (Res) and DLS (Res) showed dimensions of approximately 120 nm and a slightly positive zeta potential. The enhanced cellular uptake and selective accumulation of TLS (Res) and DLS (Res) into the mitochondria were demonstrated by behavioral observation of rhodamine-labeled TLS or DLS, using confocal microscopy, and by resveratrol quantification in the intracellular organelle, using LC–MS/MS. Furthermore, TLS (Res) and DLS (Res) induced cytotoxicity of cancer cells by generating reactive oxygen species (ROS) and by dissipating the mitochondrial membrane potential. Our results demonstrated that TLS (Res) and DLS (Res) could provide a potential strategy to treat cancers by mitochondrial targeting delivery of therapeutics and stimulation of the mitochondrial signaling pathway.

Challenges of gene delivery to the central nervous system and the growing use of biomaterial vectors

Gene therapy is a promising form of treatment for those suffering from neurological disorders or central nervous system (CNS) injury, however, obstacles remain that limit its translational potential. The CNS is protected by the blood brain barrier, and this barrier blocks genes from traversing into the CNS if administered outside of the CNS. Viral and non-viral gene delivery vehicles, commonly referred to as vectors, are modified to enhance delivery efficiency to target locations in the CNS. Still, there are few gene therapy approaches approved by the FDA for CNS disease or injury treatment. The lack of viable clinical approaches is due, in part, to the unpredictable nature of many vector systems. In particular, safety concerns exist with the use of viral vectors for CNS gene delivery. To seek some alternatives to viral vectors, development of new non-viral, biomaterial vectors is occurring at a rapid rate. This review discusses the challenges of delivering various forms of genetic material to the CNS, the use and limitations of current viral vector delivery systems, and the use of non-viral, biomaterial vectors for CNS applications.

Exhausting tumor associated macrophages with sialic acid-polyethyleneimine-cholesterol modified liposomal doxorubicin for enhancing sarcoma chemotherapy

To overstep the dilemma of chemical drug degradation within powerful lysosomes of tumor associated macrophages (TAMs), a sialic acid-polyethylenimine-cholesterol (SA-PEI-CH) modified liposomal doxorubicin (DOX-SPCL) was designed with both TAMs targeting and smart lysosomal trafficking. The modified liposome DOX-SPCL performed particle size as 103.2 ± 3.1 nm and zeta potential as -4.5 ± 0.9 mV with encapsulation efficiency as 95.8 ± 0.5%. In in vitro cell experiments, compared with conventional liposomal doxorubicin (DOX-CL) and PEGylated liposomal doxorubicin (DOX-PL), DOX-SPCL showed a selective binding on TAMs and a mere lysosomal concentration. In pharmacokinetic study, DOX-SPCL effectively impeded/delayed the disposition of mononuclear phagocyte system (MPS) with a value of AUC_0-t as 796.03 ± 66.93 mg L^-1 h. In S180 sarcomas bearing mice, DOX-SPCL showed the greatest tumor inhibition rate (92.7% ± 3.6%) compared with DOX-CL (46.4% ± 2.0%) or DOX-PL (58.8% ± 7.6%). The <0.5% positive region of TAMs in tumor section indicated a super TAMs exhaustion for DOX-SPCL treatment. Conclusively, DOX-SPCL was supposed as a safe and effective liposomal preparation for clinical sarcoma treatment via TAMs targeting/deletion delivery strategy.

Biologically-derived nanomaterials for targeted therapeutic delivery to the brain

Delivery of imaging agents and pharmaceutical payloads to the central nervous system (CNS) is essential for efficient diagnosis and treatment of brain diseases. However, therapeutic delivery is often restricted by the blood-brain barrier (BBB), which prevents transport of clinical compounds to their region of interest. This review discusses the methods that have been used to avoid or overcome this barrier, presenting the use of biologically-derived nanomaterial systems as an efficient strategy for the diagnosis and treatment of CNS diseases. Biological nanomaterials have many advantages over synthetic systems, including being biodegradable, biocompatible, easily surface functionalised for conjugation of targeting moieties, and are often able to self-assemble. These abilities are discussed in relation to various systems, including liposomes, dendrimers, and viral nanoparticles.

Extrahepatic Targeting of Oligonucleotides with Receptor-Binding Non-Immunoglobulin Scaffold Proteins

Although recent clinical successes of antisense, splice-switching, and siRNA oligonucleotides have established the therapeutic utility of this novel class of medicines, the efficient systemic application for non-liver targets remains elusive. Exploitation of active receptor-mediated targeting followed by efficient and productive cellular uptake is required for enabling the therapy of extrahepatic diseases on the expressional level. Evasion of liver accumulation and organ-specific targeting and also efficient cytosolic delivery after endosomal internalization are currently insufficiently solved issues. Lipid and polymer-based nanoparticles can be engineered for efficient cellular uptake and enhancement of endosomal escape, but are characterized by preferential liver accumulation based on biodistribution largely determined by particle size and biophysical properties. Oligonucleotide bioconjugates with receptor-binding ligands have been evolved for highly efficient targeting, but frequently result in a large extent of endosomal entrapment and consequently a lack of sufficient cytosolic concentrations. Non-immunoglobulin protein-based receptor recognition affords high cell-type selectivity and is promising for achieving nonhepatic oligonucleotide targeting. The use of such novel protein scaffolds, including designed ankyrin repeat proteins (DARPins), for oligonucleotide delivery is attractive for achieving effective tissue targeting. Issues for further development and optimization to advance approaches for extrahepatic oligonucleotide delivery by nanoparticles or bioconjugates are discussed.

Production, characterization and toxicology assay of creatine pegylated nanoliposome with polysorbate 80 for brain delivery

Creatine acts intracellularly as energy buffer and storage, demonstrating protective effects in animal models of neurodegenerative diseases. However, its permeability throught blood-brain barrier (BBB) is reduced. The aim of the present study was developing a carrier to facilitate the delivery of creatine to the central nervous system. Creatine nanoliposomes were produced, characterized and assayed in models of toxicity in vitro and in vivo. Particles showed negative zeta potential (-12,5 mV), polydispersity index 0.237 and medium-size of 105 nm, which was confirmed by transmission electron microscopy (TEM) images. Toxicity assay in vitro was evaluated with blank liposomes (no drug) or creatine nanoliposomes at concentrations of 0.02 and 0.2 mg/mL, that did not influence the viability of Vero cells. The result. of the comet assay that the nanoliposomes are not genotoxic, togeher with cell viability demonstrated that the nanoliposomes are not toxic. Besides, in vivo assays not demonstrate toxicity in hematological and biochemical markers of young rats. Nevertheless, increase content of creatine in the cerebral cortex tissue after subchronic treatment was observed. Altogether, results indicate increase permeability of creatine to the BBB that could be used as assay for in vivo studies to confirm improved effect than free creatine.

Self-Assembling Lipid-Peptide Hybrid Nanoparticles of Phospholipid-Nonaarginine Conjugates for Enhanced Delivery of Nucleic Acid Therapeutics

Despite potential applications of nucleic acid therapeutics, the lack of effective delivery systems hinders their clinical application. To overcome the barriers to nucleic acid delivery, we previously reported nanoparticles using phospholipid-polyethylenimine conjugates. However, toxicity of polyethylenimine remains as a problematic issue. Herein, we proposed to substitute the polyethylenimine with arginine-rich peptide to obtain a less-toxic carrier system. Nonaarginine was conjugated to the distal end of phospholipid hydrocarbon chains leading to phospholipid-nonaarginine conjugates (PL9R) and then lipid-peptide hybrid nanoparticles carrying oligonucleotide therapeutics (hNP) were constructed by self-assembly process. The hNP were further modified with cell penetrating Tat peptide (T-hNP) to enhance cellular uptake. The PL9R was less cytotoxic, and the hNP showed high loading capacity and colloidal stability. The T-hNP showed higher cellular uptake and transfection efficiency and effective accumulation to tumor tissue and silencing effect in tumor bearing mice. Altogether, T-hNP could provide a promising nanocarrier for nucleic acid therapeutics.

Cationic liposomes suppress intracellular calcium ion concentration increase via inhibition of PI3 kinase pathway in mast cells

Cationic liposomes are commonly used as vectors to effectively introduce foreign genes (antisense DNA, plasmid DNA, siRNA, etc.) into target cells. Cationic liposomes are also known to affect cellular immunocompetences such as the mast cell function in allergic reactions. In particular, we previously showed that the cationic liposomes bound to the mast cell surface suppress the degranulation induced by cross-linking of high affinity IgE receptors in a time- and dose-dependent manner. This suppression is mediated by impairment of the sustained level of intracellular Ca²⁺ concentration ([Ca²⁺]_i) via inhibition of store-operated Ca²⁺ entry (SOCE). Here we study the mechanism underlying an impaired [Ca²⁺]_i increase by cationic liposomes in mast cells. We show that cationic liposomes inhibit the phosphorylation of Akt and PI3 kinases but not Syk and LAT. As a consequence, SOCE is suppressed but Ca²⁺ release from endoplasmic reticulum (ER) is not. Cationic liposomes inhibit the formation of STIM1 puncta, which is essential to SOCE by interacting with Orai1 following the Ca²⁺ concentration decrease in the ER. These data suggest that cationic liposomes suppress SOCE by inhibiting the phosphorylation of PI3 and Akt kinases in mast cells.

Polyethylenimine Nanoparticle-Mediated siRNA Delivery to Reduce α-Synuclein Expression in a Model of Parkinson's Disease

RNA interference (RNAi)-based strategies that mediate the specific knockdown of target genes by administration of small interfering RNAs (siRNAs) could be applied for treatment of presently incurable neurodegenerative diseases such as Parkinson’s disease. However, inefficient delivery of siRNA into neurons hampers in vivo application of RNAi. We have previously established the 4–12 kDa branched polyethylenimine (PEI) F25-LMW with superior transfection efficacy for delivery of siRNA in vivo. Here, we present that siRNA complexed with this PEI extensively distributes across the CNS down to the lumbar spinal cord after a single intracerebroventricular infusion. siRNA against α-synuclein (SNCA), a pre-synaptic protein that aggregates in Parkinson’s disease, was complexed with PEI F25-LMW and injected into the lateral ventricle of mice overexpressing human wild-type SNCA (Thy1-aSyn mice). Five days after the single injection of 0.75 μg PEI/siRNA, SNCA mRNA expression in the striatum was reduced by 65%, accompanied by reduction of SNCA protein by ∼50%. Mice did not show signs of toxicity or adverse effects. Moreover, ependymocytes and brain parenchyma were completely preserved and free of immune cell invasion, astrogliosis, or microglial activation. Our results support the efficacy and safety of PEI nanoparticle-mediated delivery of siRNA to the brain for therapeutic intervention.

Tumor-selective lipopolyplex encapsulated small active RNA hampers colorectal cancer growth in vitro and in orthotopic murine

Small active RNA (saRNA)-induced gene activation (RNAa) is a novel strategy to treat cancer. Our previous work proved that the p21-saRNA-322 successfully hindered colorectal cancer growth by activating p21 gene. However, the barrier for successful saRNA therapy is lack of efficient drug delivery. In the present study, a rectal delivery system entitled p21-saRNA-322 encapsulated tumor-selective lipopolyplex (TSLPP-p21-saRNA-322) which consist of PEI/p21-saRNA-322 polyplex core and hyaluronan (HA) modulated lipid shell was developed to treat colorectal cancer. Our results showed that this system maintained at the rectum for more than 6 h and preferentially accumulated at tumor site. CD44 knock down experiment instructed that the superb cellular uptake of TSLPP-p21-saRNA-322 attributed to HA-CD44 recognition. An orthotopic model of bio-luminescence human colorectal cancer in mice was developed using microsurgery and TSLPP-p21-saRNA-322 demonstrated a superior antitumor efficacy in vitro and in vivo. Our results provide preclinical proof-of-concept for a novel method to treat colorectal cancer by rectal administration of TSLPP formulated p21-saRNA-322.

Engineering liposomal nanoparticles for targeted gene therapy

Recent mechanistic studies have attempted to deepen our understanding of the process by which liposome-mediated delivery of genetic material occurs. Understanding the interactions between lipid nanoparticles and cells is still largely elusive. Liposome-mediated delivery of genetic material faces systemic obstacles alongside entry into the cell, endosomal escape, lysosomal degradation and nuclear uptake. Rational design approaches for targeted delivery have been developed to reduce off-target effects and enhance transfection. These strategies, which have included the modification of lipid nanoparticles with target-specific ligands to enhance intracellular uptake, have shown significant promise at the proof-of-concept stage. Control of physical and chemical specifications of liposome composition, which includes lipid-to-DNA charge, size, presence of ester bonds, chain length and nature of ligand complexation, is integral to the performance of targeted liposomes as genetic delivery agents. Clinical advances are expected to rely on such systems in the therapeutic application of liposome nanoparticle-based gene therapy. Here, we discuss the latest breakthroughs in the development of targeted liposome-based agents for the delivery of genetic material, paying particular attention to new ligand and cationic lipid design as well as recent in vivo advances.

Brain-Targeted Polymers for Gene Delivery in the Treatment of Brain Diseases

Gene therapies have become a promising strategy for treating neurological disorders, such as brain cancer and neurodegenerative diseases, with the help of molecular biology interpreting the underlying pathological mechanisms. Successful cellular manipulation against these diseases requires efficient delivery of nucleic acids into brain and further into specific neurons or cancer cells. Compared with viral vectors, non-viral polymeric carriers provide a safer and more flexible way of gene delivery, although suffering from significantly lower transfection efficiency. Researchers have been devoted to solving this defect, which is attributed to the multiple barriers existing for gene therapeutics in vivo, such as systemic degradation, blood-brain barrier, and endosome trapping. This review will be mainly focused on systemically administrated brain-targeted polymers developed so far, including PEI, dendrimers, and synthetic polymers with various functions. We will discuss in detail how they are designed to overcome these barriers and how they efficiently deliver therapeutic nucleic acids into targeted cells.

Comb-shaped polymer grafted with REDV peptide, PEG and PEI as targeting gene carrier for selective transfection of human endothelial cells

Several REDV peptide molecules are covalently linked onto an amphiphilic block copolymer to obtain REDV-modified polycationic polymer as a gene carrier with targeting function. The targeting gene complexes show high cell recognition and binding affinity to human endothelial cells.

Non-Viral Nucleic Acid Delivery Strategies to the Central Nervous System

With an increased prevalence and understanding of central nervous system (CNS) injuries and neurological disorders, nucleic acid therapies are gaining promise as a way to regenerate lost neurons or halt disease progression. While more viral vectors have been used clinically as tools for gene delivery, non-viral vectors are gaining interest due to lower safety concerns and the ability to deliver all types of nucleic acids. Nevertheless, there are still a number of barriers to nucleic acid delivery. In this focused review, we explore the in vivo challenges hindering non-viral nucleic acid delivery to the CNS and the strategies and vehicles used to overcome them. Advantages and disadvantages of different routes of administration including: systemic injection, cerebrospinal fluid injection, intraparenchymal injection and peripheral administration are discussed. Non-viral vehicles and treatment strategies that have overcome delivery barriers and demonstrated in vivo gene transfer to the CNS are presented. These approaches can be used as guidelines in developing synthetic gene delivery vectors for CNS applications and will ultimately bring non-viral vectors closer to clinical application.

Transcytosis in the blood-cerebrospinal fluid barrier of the mouse brain with an engineered receptor/ligand system

Crossing the blood-brain and the blood-cerebrospinal fluid barriers (BCSFB) is one of the fundamental challenges in the development of new therapeutic molecules for brain disorders because these barriers prevent entry of most drugs from the blood into the brain. However, some large molecules, like the protein transferrin, cross these barriers using a specific receptor that transports them into the brain. Based on this mechanism, we engineered a receptor/ligand system to overcome the brain barriers by combining the human transferrin receptor with the cohesin domain from Clostridium thermocellum, and we tested the hybrid receptor in the choroid plexus of the mouse brain with a dockerin ligand. By expressing our receptor in choroidal ependymocytes, which are part of the BCSFB, we found that our systemically administrated ligand was able to bind to the receptor and accumulate in ependymocytes, where some of the ligand was transported from the blood side to the brain side.

Delivery of oligonucleotides with lipid nanoparticles

Since their inception in the 1980s, oligonucleotide-based (ON-based) therapeutics have been recognized as powerful tools that can treat a broad spectrum of diseases. The discoveries of novel regulatory methods of gene expression with diverse mechanisms of action are still driving the development of novel ON-based therapeutics. Difficulties in the delivery of this class of therapeutics hinder their in vivo applications, which forces drug delivery systems to be a prerequisite for clinical translation. This review discusses the strategy of using lipid nanoparticles as carriers to deliver therapeutic ONs to target cells in vitro and in vivo. A discourse on how chemical and physical properties of the lipid materials could be utilized during formulation and the resulting effects on delivery efficiency constitutes the major part of this review.

Inorganic nanovectors for nucleic acid delivery

Nucleic acids show immense potential to treat cancer, acquired immune deficiency syndrome, neurological diseases and other incurable human diseases. Upon systemic administration, they encounter a series of barriers and hence barely reach the site of action, the cell. Intracellular delivery of nucleic acids is facilitated by nanovectors, both viral and non-viral. A major advantage of non-viral vectors over viral vectors is safety. Nanovectors evaluated specifically for nucleic acid delivery include polyplexes, lipoplexes and other cationic carrier-based vectors. However, more recently there is an increased interest in inorganic nanovectors for nucleic acid delivery. Nevertheless, there is no comprehensive review on the subject. The present review would cover in detail specific properties and types of inorganic nanovectors, their preparation techniques and various biomedical applications as therapeutics, diagnostics and theranostics. Future prospects are also suggested.

Current strategies for targeted delivery of bio-active drug molecules in the treatment of brain tumor

Brain tumor is one of the most challenging diseases to treat. The major obstacle in the specific drug delivery to brain is blood-brain barrier (BBB). Mostly available anti-cancer drugs are large hydrophobic molecules which have limited permeability via BBB. Therefore, it is clear that the protective barriers confining the passage of the foreign particles into the brain are the main impediment for the brain drug delivery. Hence, the major challenge in drug development and delivery for the neurological diseases is to design non-invasive nanocarrier systems that can assist controlled and targeted drug delivery to the specific regions of the brain. In this review article, our major focus to treat brain tumor by study numerous strategies includes intracerebral implants, BBB disruption, intraventricular infusion, convection-enhanced delivery, intra-arterial drug delivery, intrathecal drug delivery, injection, catheters, pumps, microdialysis, RNA interference, antisense therapy, gene therapy, monoclonal/cationic antibodies conjugate, endogenous transporters, lipophilic analogues, prodrugs, efflux transporters, direct conjugation of antitumor drugs, direct targeting of liposomes, nanoparticles, solid-lipid nanoparticles, polymeric micelles, dendrimers and albumin-based drug carriers.

Phospholipid-polyethylenimine conjugate-based micelle-like nanoparticles for siRNA delivery

Gene silencing using small interfering RNA (siRNA) is a promising therapeutic strategy for the treatment of various diseases, in particular, cancer. Recently, our group reported on a novel gene carrier, the micelle-like nanoparticle (MNP), based on the combination of a covalent conjugate of phospholipid and polyethylenimine (PLPEI) with polyethylene glycol (PEG) and lipids. These long-circulating MNPs loaded with plasmid DNA-mediated gene expression in distal tumors after systemic administration in vivo. In the current study, we investigated the potential of MNPs for siRNA delivery. MNPs were prepared by condensing siRNA with PLPEI at a nitrogen/phosphate ratio of 10, where the binding of siRNA is complete. The addition of a PEG/lipid coating to the PLPEI complexes generated particles with sizes of ca. 200 nm and a neutral surface charge compared with positively charged PLPEI polyplexes without the additional coating. MNPs protected the loaded siRNA against enzymatic digestion and enhanced the cellular uptake of the siRNA payload. MNPs carrying green fluorescent protein (GFP)-targeted siRNA effectively downregulated the gene in cells that stably express GFP. Finally, MNPs were non-toxic at a wide range of concentrations and for different cell lines.

Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications

This review highlights the recent developments of surface modification and endothelialization of biomaterials in vascular tissue engineering applications.

Generation of blood circulating DNA: the sources, peculiarities of circulation and structure

Extracellular nucleic acids (exNA) were described in blood of both healthy and illness people as early as in 1948, but staied overlooked until middle 60-th. Starting from the beginning of new millennium and mainly in the last 5 years exNA are intensively studied. Main attention is directed to investigation of exNA as the source of diagnostic material whereas the mechanisms of their generation, as well as mechanisms to providing long-term circulation of exNA in the bloodstream are not established unambiguously. According to some authors, the main source of circulating nucleic acids in blood are the processes of apoptosis and necrosis, while others refer to the possible nucleic acid secretion by healthy and tumor cells. Circulating DNA were found to be stable in the blood for a long time, escaping from the action of DNA hydrolyzing enzymes and are apparently packed in different supramolecular complexes. This review presents the opinions of various authors and evidence in favor of all the theories describingappearance of extracellular DNA, the features of the circulation and structure of the extracellular DNA and factors affecting the time of DNA circulation in blood

Folate-targeted liposome encapsulating chitosan/oligonucleotide polyplexes for tumor targeting

We previously reported that a liposome encapsulating polyethylenimine/oligonucleotides is suitable for in vivo delivery of nucleic acid therapeutics. However, toxicity of polyethylenimine is an obstacle in clinical application. To develop a liposome encapsulating polyplexes applicable to clinical use, we proposed to replace polyethylenimine with chitosan and thus constructed the liposome encapsulating low-molecular weight chitosan (LMWC)/oligonucleotide (ODN) polyplexes [LS(CO)]. ODN was completely complexed to LMWC at pH 5.5 and an N/P ratio 10 with a positive zeta potential of 19.81 ± 1.11. The positively charged polyplexes were encapsulated into anionic liposome by membrane extrusion. Folate-targeted liposome encapsulating LMWC/ODN complex [FLS(CO)] was prepared by adding folate-conjugated phospholipid. The resulting LS(CO) and FLS(CO) were characterized with respect to size distribution, zeta potential, and colloidal stability. The LS(CO) and FLS(CO) were also evaluated for in vitro cellular uptake and cytotoxicity. The LS(CO) and FLS(CO) showed a narrow size distribution with a mean diameter of about 130 nm and neutral zeta potentials and remained stable for 7 days in 0.15-M NaCl at room temperature. FLS(CO) showed higher cellular uptake than LS(CO) in B16F10 murine melanoma cells. Furthermore, LS(CO) showed less toxicity as compared to liposome encapsulating polyethylenimine/oligonucleotides, representing a biocompatible nanocarrier of oligonucleotide therapeutics.

Transferrin-bearing polypropylenimine dendrimer for targeted gene delivery to the brain

The possibility of using genes as medicines to treat brain diseases is currently limited by the lack of safe and efficacious delivery systems able to cross the blood-brain barrier, thus resulting in a failure to reach the brain after intravenous administration. On the basis that iron can effectively reach the brain by using transferrin receptors for crossing the blood-brain barrier, we propose to investigate if a transferrin-bearing generation 3-polypropylenimine dendrimer would allow the transport of plasmid DNA to the brain after intravenous administration. In vitro, the conjugation of transferrin to the polypropylenimine dendrimer increased the DNA uptake by bEnd.3 murine brain endothelioma cells overexpressing transferrin receptors, by about 1.4-fold and 2.3-fold compared to that observed with the non-targeted dendriplex and naked DNA. This DNA uptake appeared to be optimal following 2h incubation with the treatment. In vivo, the intravenous injection of transferrin-bearing dendriplex more than doubled the gene expression in the brain compared to the unmodified dendriplex, while decreasing the non-specific gene expression in the lung. Gene expression was at least 3-fold higher in the brain than in any tested peripheral organs and was at its highest 24h following the injection of the treatments. These results suggest that transferrin-bearing polypropylenimine dendrimer is a highly promising gene delivery system to the brain.

Storage stability of optimal liposome-polyethylenimine complexes (lipopolyplexes) for DNA or siRNA delivery

The delivery of nucleic acids such as DNA or siRNA still represents a major hurdle, especially with regard to possible therapeutic applications in vivo. Much attention has been focused on the development of non-viral gene delivery vectors, including liposomes or cationic polymers. Among them, polyethylenimines (PEIs) have been widely explored for the delivery of nucleic acids and show promising results. The combination of cationic polymers and liposomes (lipopolyplexes) for gene delivery may further improve their efficacy and biocompatibility, by combining the favourable properties of lipid systems (high stability, efficient cellular uptake, low cytotoxicity) and PEIs (nucleic acid condensation, facilitated endosomal release). In this study, we systematically analyse various conditions for the preparation of liposome-polyethylenimine-based lipopolyplexes with regard to biological activity (DNA transfection efficacy, siRNA knockdown efficacy) and physicochemical properties (size, zeta potential, stability). This includes the exploration of lipopolyplex compositions containing different liposomes and different relevant branched or linear low-molecular-weight PEIs. We establish optimal parameters for lipopolyplex generation, based on various PEIs, N/P ratios, lipids, lipid/PEI ratios and preparation conditions. Importantly, we also demonstrate that certain lipopolyplexes retain their biological activity and physicochemical integrity upon prolonged storage, even at 37°C and/or in the presence of serum, thus providing formulations with considerably higher stability as compared to polyplexes. In conclusion, we establish optimal liposome-polyethylenimine lipopolyplexes that allow storage under ambient conditions. This is the basis and an essential prerequisite for novel, promising and easy-to-handle formulations for possible therapeutic applications.

cRGD mediated liposomes enhanced antidepressant-like effects of edaravone in rats

The delayed onset of therapeutic outcomes is a major drawback of the current antidepressants. The blood-brain barrier is the most important bottleneck impeding drug transport into the brain. Therefore, development of novel antidepressant medications with rapid onset and sustained activity is urgent. RGD liposomes showed an excellent effect of brain-targeting drug delivery and increased the entering rate to the brain. In the present study, we prepared cyclic RGD liposomes loaded with edaravone (cRGD-ERLs) and evaluated the potential antidepressant-like effects of this drug delivery system in rats. The results showed single injection of cRGD-ERLs produced significant antidepressant-like effects in both forced swim and novelty suppressed feeding test. Moreover, acute cRGD-ERLs increased the expression of c-fos in the medial prefrontal cortex, suggesting that cRGD-ERLs could activate the neuronal function. Furthermore, cRGD-ERLs reversed the increase of lipopolysaccharides (LPS)-induced plasma cytokine IL-1β and IL-6, suggesting that normalization of cytokine level might be involved in the behavioral response of cRGD-ERLs. Finally, cRGD-ERLs prevented the increase of immobility induced by LPS in the forced swim test. Overall, the current data revealed a novel brain-target drug delivery system, which can be used to improve the therapeutic outcomes of antidepressants by increase of crossing rate to the brain.

Inhibitory effects of a cationic liposome on allergic reaction mediated by mast cell activation

Several studies have shown that cationic liposomes exert immunomodulatory effects with low immunogenicity and toxicity, and offer advantages such as easy preparation and targeting. Cationic liposomes not only transport DNA to immune cells but also enhance the function of antigen presenting cells such as dendritic cells and macrophages. Here, we investigated the effect of a particular cationic liposome on mast cell function during allergic reaction. We found that the cationic liposomes bound to the mast cell surface suppressed degranulation induced by cross-linking of high affinity immunoglobulin E receptors in a time- and dose-dependent manner. The suppression of degranulation was mediated by impairment of the sustained level of intracellular Ca(2+) concentration ([Ca(2+)]i) derived from the inhibition of store-operated Ca(2+) entry. The decrease in sustained elevation of [Ca(2+)]i led to the suppression of phosphorylation of soluble N-ethylmaleimide-sensitive factor attachment protein receptor proteins such as SNAP-23, syntaxin-4, which are necessary for membrane fusion between secretory granules and the plasma membrane during degranulation. Furthermore, the cationic liposomes suppressed vascular permeability elevation induced by mast cell activation in mice. These results showed that cationic liposomes possess the novel property of inhibiting mast cell activation, suggesting the possibility of developing cationic liposomes as anti-allergic effectors.

Nanoparticle-mediated delivery of oligonucleotides to the blood-brain barrier: in vitro and in situ brain perfusion studies on the uptake mechanisms

Except for the few exceptions where topical administration is feasible, progress towards broad clinical application of nucleic acid therapeutics requires development of effective systemic delivery strategies. The central nervous system represents a particularly difficult organ for systemic delivery due to the blood-brain barrier. We previously reported a nanoparticulate delivery system for targeted brain delivery of oligonucleotides upon systemic administration, i.e. liposome-encapsulated polyethylenimine/oligonucleotides polyplexes. In this study, cellular uptake and intracellular trafficking of the nanoparticles were further investigated using in situ brain perfusion technique followed by colocalization and fluorescence resonance energy transfer techniques. The brain endothelial uptake and possibly parenchymal accumulation were readily visualized upon administration via internal carotid artery perfusion. The nanoparticles were colocalized with early-endosome antigen, which confirms the brain endothelial uptake through transferrin receptor-mediated endocytosis. Fluorescence resonance energy transfer analysis also suggested the nanoparticles entered the brain endothelial cells while maintaining their integrity. Together, the enhanced brain uptake, as claimed previously, of the antibody-targeted nanoparticles was clearly confirmed with more convincing evidences. In addition, the experimental techniques described here should be applicable to the studies involving nanoparticle-mediated brain delivery of nucleic acid therapeutics.

Comparative binding, endocytosis, and biodistribution of antibodies and antibody-coated carriers for targeted delivery of lysosomal enzymes to ICAM-1 versus transferrin receptor

Targeting lysosomal enzymes to receptors involved in transport into and across cells holds promise to enhance peripheral and brain delivery of enzyme replacement therapies (ERTs) for lysosomal storage disorders. Receptors being explored include those associated with clathrin-mediated pathways, yet other pathways seem also viable. Well characterized examples are that of transferrin receptor (TfR) and intercellular adhesion molecule 1 (ICAM-1), involved in iron transport and leukocyte extravasation, respectively. TfR and ICAM-1 support ERT delivery via clathrin- vs. cell adhesion molecule-mediated mechanisms, displaying different valency and size restrictions. To comparatively assess this, we used antibodies vs. larger multivalent antibody-coated carriers and evaluated TfR vs. ICAM-1 binding and endocytosis in endothelial cells, as well as in vivo biodistribution and delivery of a model lysosomal enzyme required in peripheral organs and brain: acid sphingomyelinase (ASM), deficient in types A-B Niemann Pick disease. We found similar binding of antibodies to both receptors under control conditions, with enhanced binding to activated endothelium for ICAM-1, yet only anti-TfR induced endocytosis efficiently. Contrarily, antibody-coated carriers showed enhanced binding, engulfment, and endocytosis for ICAM-1. In mice, anti-TfR enhanced brain targeting over anti-ICAM, with an opposite outcome in the lungs, while carriers enhanced ICAM-1 targeting over TfR in both organs. Both targeted carriers enhanced ASM delivery to the brain and lungs vs. free ASM, with greater enhancement for anti-ICAM carriers. Therefore, targeting TfR or ICAM-1 improves lysosomal enzyme delivery. Yet, TfR targeting may be more efficient for smaller conjugates or fusion proteins, while ICAM-1 targeting seems superior for multivalent carrier formulations.