Lipid envelope-type nanoparticle incorporating a multifunctional peptide for systemic siRNA delivery to the pulmonary endothelium

Recent Advances in Endogenous and Exogenous Stimuli-Responsive Nanocarriers for Drug Delivery and Therapeutics

Significant progress has been achieved in the development of stimuli-responsive nanocarriers for drug delivery, diagnosis, and therapy. Various types of triggers are utilized in the development of nanocarrier delivery. Endogenous factors such as changes in pH, redox, gradient, and enzyme concentration which are linked to disease progression have been utilized for controlling biodistribution and releasing drugs from nanocarriers, as well as increasing subsequent pharmacological activity at the disease site. Nanocarriers which respond to artificially-induced exogenous factors (such as temperature, light, magnetic field, and ultrasound) have also been developed. This review aims to discuss recent advances in the design of stimuli-responsive nanocarriers which appear to have a promising future in medicine.

Anti-Inflammatory Effect of Anti-TNF-α SiRNA Cationic Phosphorus Dendrimer Nanocomplexes Administered Intranasally in a Murine Acute Lung Injury Model

Inflammation is an essential component of many lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), or acute lung injury. Our purpose was to design efficient carriers for lung delivery of small interfering RNA (siRNA) targeting tumor necrosis factor (TNF-α) in an acute lung injury model. To achieve this goal, two different types of phosphorus-based dendrimers with either pyrrolidinium or morpholinium as terminal protonated amino groups were selected for their better biocompatibility compared to other dendrimers. Dendriplexes containing pyrrolidinium surface groups demonstrated a stronger siRNA complexation, a higher cellular uptake, and enhanced in vitro silencing efficiency of TNF-α in the lipopolysaccharide (LPS)-activated mouse macrophage cell line RAW264.7, compared to morpholinium-containing dendriplexes. The better performance of the pyrrolidium dendriplexes was attributed to their higher pK_a value leading to a stronger siRNA complexation and improved protection against enzymatic degradation resulting in a higher cellular uptake. The superior silencing effect of the pyrrolidinium dendriplexes, compared to noncomplexed siRNA, was confirmed in vivo in an LPS-induced murine model of short-term acute lung injury upon lung delivery via nasal administration. These data suggest that phosphorus dendriplexes have a strong potential in lung delivery of siRNA for treating inflammatory lung diseases.

Functional peptides for siRNA delivery

siRNA is considered as a potent therapeutic agent because of its high specificity and efficiency in suppressing genes that are overexpressed during disease development. For nearly two decades, a significant amount of efforts has been dedicated to bringing the siRNA technology into clinical uses. However, only limited success has been achieved to date, largely due to the lack of a cell type-specific, safe, and efficient delivery technology to carry siRNA into the target cells' cytosol where RNA interference takes place. Among the emerging candidate nanocarriers for siRNA delivery, peptides have gained popularity because of their structural and functional diversity. A variety of peptides have been discovered for their ability to translocate siRNA into living cells via different mechanisms such as direct penetration through the cellular membrane, endocytosis-mediated cell entry followed by endosomolysis, and receptor-mediated uptake. This review is focused on the multiple roles played by peptides in siRNA delivery, such as membrane penetration, endosome disruption, targeting, as well as the combination of these functionalities.

Anti-angiogenic nanotherapy via active targeting systems to tumors and adipose tissue vasculature

Sophisticated drug delivery systems (DDS) are required for delivering drugs, especially macromolecules such as nucleic acids or proteins, to their sites of action. Therefore it is a prerequisite that future DDS are designed to selectively target a tissue. In this review, we focus on systems that actively target the vasculature in tumors or adipose tissues. For targeting tumor vasculatur, a new strategy referred to as dual-targeting is proposed that uses a combination of a receptor specific ligand and a cell penetrating peptide, which can induce the synergistic enhancement of tissue selectivity under in vivo conditions. A novel pH-sensitive cationic lipid was designed to enhance the endosomal release of encapsulated compounds such as siRNA as well as to improve the stability in blood circulation after intravenous administration. A cyclic RGD peptide is used as an active targeting ligand. For targeting adipose vasculature, prohibitin, which is expressed on the surface of adipose endothelial cells, was targeted with KGGRAKD peptides on the surface of PEGylated nanoparticles. Prohibitin targeted nanoparticles (PTNP) encapsulating Cytochrome c (CytC) can selectively target adipose vasculature by optimizing the lengths of the PEG linkers and can deliver CytC to adipose endothelial cells. PTNP can successfully induce anti-obese effects as well as apoptosis by delivering CytC to the cytosol in endothelial cells. Unexpectedly, the EPR (enhanced permeability and retention) effect, which is usually observed in tumor tissue, was also observed in the adipose vasculature, especially in obese mice, where PEGylated nanoparticles can pass through the endothelial barriers in adipose tissue. We believe that these achievements in active targeting will allow a greatly expanded use of DDS for nanomedicines.

Nanomedicine as an emerging platform for metastatic lung cancer therapy

Metastatic lung cancer is one of the most common cancers leading to mortality worldwide. Current treatment includes chemo- and pathway-dependent therapy aiming at blocking the spread and proliferation of these metastatic lesions. Nanomedicine is an emerging multidisciplinary field that offers unprecedented access to living cells and promises the state of the art in cancer detection and treatment. Development of nanomedicines as drug carriers (nanocarriers) that target cancer for therapy draws upon principles in the fields of chemistry, medicine, physics, biology, and engineering. Given the zealous activity in the field as demonstrated by more than 30 nanocarriers already approved for clinical use and given the promise of recent clinical results in various studies, nanocarrier-based strategies are anticipated to soon have a profound impact on cancer medicine and human health. Herein, we will detail the latest innovations in therapeutic nanomedicine with examples from lipid-based nanoparticles and polymer-based approaches, which are engineered to deliver anticancer drugs to metastatic lung cells. Emphasis will be placed on the latest and most attractive delivery platforms, which are developed specifically to target lung metastatic tumors. These novel nanomedicines may open new avenues for therapeutic intervention carrying new class of drugs such as RNAi and mRNA and the ability to edit the genome using the CRISPER/Cas9 system. Ultimately, these strategies might become a new therapeutic modality for advanced-stage lung cancer.

Transcytosis-Targeting Peptide: A Conductor of Liposomal Nanoparticles through the Endothelial Cell Barrier

The ultimate goal in the area of drug-delivery systems is the development of a nanoparticle that can penetrate the endothelial cell monolayer for the targeting of tissue parenchyma. In the present study, we identify a transcytosis-targeting peptide (TTP) that permits polyethyleneglycol (PEG)-modified liposomes (PEG-LPs) to penetrate through monolayers of brain-derived endothelial cells. These endothelial cells were layered on a gelatin nanofiber sheet, a nanofiber meshwork that allows the evaluation of transcellular transport of nanosized particles (ca. 100 nm). Systematic modification of the sequences results in the identification of the consensus sequence of TTP as L(R/K)QZZZL, where Z denotes hydrophilic amino acids (R/K/S and partially D). The TTP-modified liposomes are bound on the heparin sulfate proteoglycan, and are then taken up via lipid raft-mediated endocytosis. Subsequent intracellular imaging of the particles reveals a unique intracellular sorting of TTP-modified PEG liposomes (TTP-PEG-LPs); namely the TTP-LPs are not localized with the lysosomes, whereas this co-localization is dominant in the unmodified PEG liposomes (PEG-LPs). The in vivo endothelial penetration of liposomes in adipose tissue is conferred by the dual modification of the particles with TTP and tissue-targeting ligands. This technology promises innovations in intravenously available delivery system to tissue parenchyma.

Aerosol Delivery of siRNA to the Lungs. Part 1: Rationale for Gene Delivery Systems

This article reviews the pulmonary route of administration, aerosol delivery devices, characterization of pulmonary drug delivery systems, and discusses the rationale for inhaled delivery of siRNA. Diseases with known protein malfunctions may be mitigated through the use of siRNA therapeutics. The inhalation route of administration provides local delivery of siRNA therapeutics for the treatment of various pulmonary diseases, however barriers to pulmonary delivery and intracellular delivery of siRNA exists. siRNA loaded nanocarriers can be used to overcome the barriers associated with the pulmonary route, such as anatomical barriers, mucociliary clearance, and alveolar macrophage clearance. Apart from naked siRNA aerosol delivery, previously studied siRNA carrier systems comprise of lipidic, polymeric, peptide, or inorganic origin. Such siRNA delivery systems formulated as aerosols can be successfully delivered via an inhaler or nebulizer to the pulmonary region. Preclinical animal investigations of inhaled siRNA therapeutics rely on intratracheal and intranasal siRNA and siRNA nanocarrier delivery. Aerosolized siRNA delivery systems may be characterized using in vitro techniques, such as dissolution test, inertial cascade impaction, delivered dose uniformity assay, laser diffraction, and laser Doppler velocimetry. The ex vivo techniques used to characterize pulmonary administered formulations include the isolated perfused lung model. In vivo techniques like gamma scintigraphy, 3D SPECT, PET, MRI, fluorescence imaging and pharmacokinetic/pharmacodynamics analysis may be used for evaluation of aerosolized siRNA delivery systems. The use of inhalable siRNA delivery systems encounters barriers to their delivery, however overcoming the barriers while formulating a safe and effective delivery system will offer unique advances to the field of inhaled medicine.

Teniposide-loaded multilayer modified albumin nanoparticles with increased passive delivery to the lung

The structure of the albumin core and multi-coated layers are designed to encapsulate teniposide for achieving controlled release and passively targeted delivery to the lung.

Multifunctional Envelope-Type Nano Device: Evolution from Nonselective to Active Targeting System

A paradigm shift has occurred in the field of drug delivery systems (DDS), one being intracellular targeting, and the other, active targeting. An important aspect of intracellular targeting involves delivering nucleic acids such as siRNA/pDNA rather than small molecular compounds, since the mechanism responsible for their entering a target cell is usually via endocytosis, and the efficiency of endosomal escape is a critical factor in determining the functional activities of siRNA/pDNA. A multifunctional envelope-type nano device (MEND) was developed to control the intracellular trafficking of nano carriers containing siRNA/pDNA. An octaarginine (R8) modified MEND was developed to achieve this. Considerable progress has been made in active targeting to selective tissue vasculature such as tumor, adipose tissue, and the lung where endothelial barrier is tight against nanoparticles with diameters larger than 50 nm. A dual-ligand system is proposed to enhance active targeting ability by virtue of a synergistic interaction between a selective ligand and a cell penetrating ligand. Prohibitin targeted nanoparticles (PTNP) were developed to target endothelial cells in adipose tissue, which deliver apoptotic peptides/proteins to the adipose vasculature. Lung endothelial cells can be targeted by means of the GALA peptide, which is usually used to enhance endosomal escape. These active targeting systems can induce pharmacological effects in in vivo conditions. Finally, a novel strategy for producing an original ligand has been developed, especially for the tumor vasculature. This progress in DDS promises to extend the area of nanomedicine as a breakthrough technology.

Delivery of RNA nanoparticles into colorectal cancer metastases following systemic administration

The majority of deaths from all cancers, including colorectal cancer (CRC), is a result of tumor metastasis to distant organs. To date, an effective and safe system capable of exclusively targeting metastatic cancers that have spread to distant organs or lymph nodes does not exist. Here, we constructed multifunctional RNA nanoparticles, derived from the three-way junction (3WJ) of bacteriophage phi29 motor pRNA, to target metastatic cancer cells in a clinically relevant mouse model of CRC metastasis. The RNA nanoparticles demonstrated metastatic tumor homing without accumulation in normal organ tissues surrounding metastatic tumors. The RNA nanoparticles simultaneously targeted CRC cancer cells in major sites of metastasis, such as liver, lymph nodes, and lung. Our results demonstrate the therapeutic potential of these RNA nanoparticles as a delivery system for the treatment of CRC metastasis.

Drug and gene co-delivery systems for cancer treatment

Cancer remains a major killer and a leading cause of death in the world; thus, a growing number of new treatments have been focused on cancer therapy over the past few decades. Chemotherapy, which is thought to be a powerful strategy for cancer treatment, has been widely used in clinical therapy in recent years. However, due to the complexity of cancer, a single therapeutic approach is insufficient for the suppression of cancer growth and migration. Therefore, increasing attention has been paid to the use of smart multifunctional carriers and combinatorially delivers chemotherapeutic drugs and functional genes in order to maximize therapeutic efficiency. Combination therapy using selected drugs and genes can not only overcome multidrug resistance and inhibit the cellular anti-apoptotic process but also achieve a synergistic therapeutic effect. Because multifunctional nanocarriers are important for achieving these goals, this review will illustrate and discuss some advanced biomaterial nanocarriers for co-delivering therapeutic genes and drugs, including multifunctional micelles, liposomes, polymeric conjugates and inorganic nanoparticles. In addition, the challenges and future perspectives for co-delivery systems, containing therapeutic drugs and genes to achieve better therapeutic effects for cancer treatment will be discussed.

Going beyond the liver: progress and challenges of targeted delivery of siRNA therapeutics

Therapeutic gene silencing promises significant progress in pharmacotherapy, including considerable expansion of the druggable target space and the possibility for treating orphan diseases. Technological hurdles have complicated the efficient use of therapeutic oligonucleotides, and siRNA agents suffer particularly from insufficient pharmacokinetic properties and poor cellular uptake. Intense development and evolution of delivery systems have resulted in efficient uptake predominantly in liver tissue, in which practically all nanoparticulate and liposomal delivery systems show the highest accumulation. The most efficacious strategies include liposomes and bioconjugations with N-acetylgalactosamine. Both are in early clinical evaluation stages for treatment of liver-associated diseases. Approaches for achieving knockdown in other tissues and tumors have been proven to be more complicated. Selective targeting to tumors may be enabled through careful modulation of physical properties, such as particle size, or by taking advantage of specific targeting ligands. Significant barriers stand between sufficient accumulation in other organs, including endothelial barriers, cellular membranes, and the endosome. The brain, which is shielded by the blood-brain barrier, is of particular interest to facilitate efficient oligonucleotide therapy of neurological diseases. Transcytosis of the blood-brain barrier through receptor-specific docking is investigated to increase accumulation in the central nervous system. In this review, the current clinical status of siRNA therapeutics is summarized, as well as innovative and promising preclinical concepts employing tissue- and tumor-targeted ligands. The requirements and the respective advantages and drawbacks of bioconjugates and ligand-decorated lipid or polymeric particles are discussed.

Application of apolipoprotein E-modified liposomal nanoparticles as a carrier for delivering DNA and nucleic acid in the brain

An innovative drug delivery technology is urgently needed to satisfy unmet medical needs in treating various brain disorders. As a fundamental carrier for plasmid DNA or nucleic acids, we developed a liposomal nanoparticle (multifunctional envelope-type nano device [MEND]) containing a proton-ionizable amino lipid (YSK-MEND). Here we report on the impact of apolipoprotein E (ApoE) modification on the function of YSK-MEND in terms of targeting brain cells. The cellular uptake and function of YSK-MEND encapsulating short interference RNA or plasmid DNA were significantly improved as a result of ApoE modification in mouse neuron-derived cell lines (Neuro-2a and CAD). Intracerebroventricular administration of ApoE-modified YSK-MEND (ApoE/YSK-MEND) encapsulating plasmid DNA also resulted in higher transgene expression in comparison with YSK-MEND that was not modified with ApoE. Moreover, observation of fluorescence-labeled ApoE/YSK-MEND and expression of mCherry (fluorescence protein) derived from plasmid DNA indicated that this carrier might be useful for delivering and conferring transgene expression in neural stem cells and/or neural progenitor cells. Thus, this system may be a useful tool for the treatment of neurodegenerative disease.

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.

siRNA delivery to the lung: what's new?

RNA interference (RNAi) has been thought of as the general answer to many unmet medical needs. After the first success stories, it soon became obvious that short interfering RNA (siRNA) is not suitable for systemic administration due to its poor pharmacokinetics. Therefore local administration routes have been adopted for more successful in vivo RNAi. This paper reviews nucleic acid modifications, nanocarrier chemistry, animal models used in successful pulmonary siRNA delivery, as well as clinical translation approaches. We summarize what has been published recently and conclude with the potential problems that may still hamper the efficient clinical application of RNAi in the lung.

A nanocarrier system for the delivery of nucleic acids targeted to a pancreatic beta cell line

Pancreatic β cells secrete insulin in response to glucose levels and thus are involved in controlling blood glucose levels. A line of pancreatic β cells "MIN6" has been used in studies related to the function of β cells and diabetes therapy. Regulating gene expression in MIN6 cells could accelerate these studies, but an efficient method for the transfection of nucleic acids targeted to MIN6 cells is required. We report here on a liposome-based carrier targeted to pancreatic β cells (Multifunctional envelope-type nano device for pancreatic β cells, β-MEND). We identified a lipid composition for use in preparing the β-MEND, which permits the particles to be efficiently internalized into MIN6, as evidenced by flow cytometry analyses. Intracellular observation by confocal laser scanning microscopy showed that the β-MEND efficiently delivered the oligo nucleic acids to the cytosol of MIN6 cells. Moreover, using a β-MEND encapsulating a 2'-O-Methyl RNA complementary to a microRNA that suppresses insulin secretion, the knockdown of the targeted microRNA and an up-regulation of insulin secretion were observed in MIN6. Thus, the β-MEND holds promise as an efficient system for delivering nucleic acids targeted to MIN6 and can contribute to research and therapy aimed at diabetes.