Modified Tat peptide with cationic lipids enhances gene transfection efficiency via temperature-dependent and caveolae-mediated endocytosis

Persistent Targeting DNA Nanocarrier Made of 3D Structural Unit Assembled from Only One Basic Multi-Palindromic Oligonucleotide for Precise Gene Cancer Therapy

Construction of a simple, reconfigurable, and stimuli-responsive DNA nanocarrier remains a technical challenge. In this contribution, by designing three palindromic fragments, a simplest four-sticky end-contained 3D structural unit (PS-unit) made of two same DNA components is proposed. Via regulating the rotation angle of central longitudinal axis of PS-unit, the oriented assembly of one-component spherical architecture is accomplished with high efficiency. Introduction of an aptamer and sticky tail warehouse into one component creates a size-change-reversible targeted siRNA delivery nanovehicle. Volume swelling of 20 nm allows one carrier to load 1987 siPLK1s. Once entering cancer cells and responding to glutathione (GSH) stimuli, siPLK1s are almost 100% released and original size of nanovehicle is restored, inhibiting the expression of PLK1 protein and substantially suppressing tumor growth (superior to commercial transfection agents) in tumor-bearing mice without systemic toxicity.

Constructing Nucleic Acid Delivering Lipoproteoplexes from Coiled-Coil Supercharged Protein and Cationic Liposomes

The safe and efficient delivery of nucleic acids is crucial for both clinical applications of gene therapy and pre-clinical laboratory research. Such delivery strategies rely on vectors to condense nucleic acid payloads and escort them into the cell without being degraded in the extracellular environment; however, the construction and utilization of these vectors can be difficult and time-consuming. Here, we detail the steps involved in the rapid, laboratory-scale production and assessment of a versatile, nucleic acid delivery vehicle, known as the lipoproteoplex. In this chapter, we outline: (1) the recombinant synthesis and subsequent purification of the supercharged coiled-coil protein component known as N8; (2) the synthesis of cationic liposomes from dioleoyl-3-trimethylammonium propane (DOTAP) and sodium cholate; (3) and finally a protocol for the delivery of a model siRNA cargo into a cultured cell line.

Recognizing CRISPR as the new age disease-modifying drug: Strategies to bioengineer CRISPR/Cas for direct in vivo delivery

Clustered regularly interspaced short palindromic repeats (CRISPR) have established itself as a frontier technology in genetic engineering. Researchers have successfully used the CRISPR/Cas system as precise gene editing tools and have further expanded their scope beyond both imaging and diagnostic applications. The most prominent utility of CRISPR is its capacity for gene therapy, serving as the contemporary, disease-modifying drug at the genetic level of human medical disorders. Correcting these diseases using CRISPR-based gene editing has developed to the extent of preclinical trials and possible patient treatments. A major impediment in actualizing this is the complications associated with in vivo delivery of the CRISPR/Cas complex. Currently, only the viral vectors (e.g., lentivirus) and non-viral encapsulation (e.g., lipid particles, polymer-based, and gold nanoparticles) techniques have been extensively reviewed, neglecting the efficiency of direct delivery. However, the direct delivery of CRISPR/Cas for in vivo gene editing therapies is an intricate process with numerous drawbacks. Hence, this paper discusses in detail both the need and the strategies that can potentially improve the direct delivery aspects of CRISPR/Cas biomolecules for gene therapy of human diseases. Here, we focus on enhancing the molecular and functional features of the CRISPR/Cas system for targeted in vivo delivery such as on-site localization, internalization, reduced immunogenicity, and better in vivo stability. We additionally emphasize the CRISPR/Cas complex as a multifaceted, biomolecular vehicle for co-delivery with therapeutic agents in targeted disease treatments. The delivery formats of efficient CRISPR/Cas systems for human gene editing are also briefly elaborated.

Non-Viral Carriers for Nucleic Acids Delivery: Fundamentals and Current Applications

Over the past decades, non-viral DNA and RNA delivery systems have been intensively studied as an alternative to viral vectors. Despite the most significant advantage over viruses, such as the lack of immunogenicity and cytotoxicity, the widespread use of non-viral carriers in clinical practice is still limited due to the insufficient efficacy associated with the difficulties of overcoming extracellular and intracellular barriers. Overcoming barriers by non-viral carriers is facilitated by their chemical structure, surface charge, as well as developed modifications. Currently, there are many different forms of non-viral carriers for various applications. This review aimed to summarize recent developments based on the essential requirements for non-viral carriers for gene therapy.

The steep road to nonviral nanomedicines: Frequent challenges and culprits in designing nanoparticles for gene therapy

The potential of therapeutically loaded nanoparticles (NPs) has been successfully demonstrated during the last decade, with NP-mediated nonviral gene delivery gathering significant attention as highlighted by the broad clinical acceptance of mRNA-based COVID-19 vaccines. A significant barrier to progress in this emerging area is the wild variability of approaches reported in published literature regarding nanoparticle characterizations. Here, we provide a brief overview of the current status and outline important concerns regarding the need for standardized protocols to evaluate NP uptake, NP transfection efficacy, drug dose determination, and variability of nonviral gene delivery systems. Based on these concerns, we propose wide adherence to multimodal, multiparameter, and multistudy analysis of NP systems. Adoption of these proposed approaches will ensure improved transparency, provide a better basis for interlaboratory comparisons, and will simplify judging the significance of new findings in a broader context, all critical requirements for advancing the field of nonviral gene delivery.

Multicompartment systems: A putative carrier for combined drug delivery and targeting

In this review, we discuss recent developments in multicompartment systems commonly referred to as vesosomes, as well as their method of preparation, surface modifications, and clinical potential. Vesosomal systems are able to entrap more than one drug moiety and can be customized for site-specific delivery. We focus in particular on the possible reticuloendothelial system (RES) - mediated accumulation of vesosomes, and their application in tumor targeting, as areas for further investigation.

Glimpse into Cellular Internalization and Intracellular Trafficking of Lipid-Based Nanoparticles in Cancer Cells

Lipid-based nanoparticles as drug delivery carriers have been mainly used for delivery of anti-cancer therapeutic agents. Lipid-based nanoparticles, due to their smaller particle size and similarity to cell membranes, are readily internalized into cancer cells. Interestingly, cancer cells also overexpress receptors for specific ligands including folic acid, hyaluronic acid, and transferrin on their surface. This allows the use of these ligands for surface modification of the lipid-based nanoparticle. These modifications then allow the specific recognition of these ligand-coated nanoparticles by their receptors on cancer cells allowing the targeted gradual intracellular accumulation of the functionalized nanoplatforms. These interactions could eventually enhance the internalization of desired drugs via increasing ligand-receptor mediated cellular uptake of the nanoplatforms. The cellular internalization of the nanoplatforms also varies and depends on their physicochemical properties including particle size, zeta potential, and shape. The cellular uptake is also influenced by the types of ligand internalization pathway utilized by cells such as phagocytosis, macropinocytosis, and multiple endocytosis pathways. In this review, we will classify and discuss lipid based nanoparticles engineered to express specific ligands, and are recognized by their receptors on cancer cell, and their cellular internalization pathways. Moreover, the intracellular fate of nanoparticles decorated with specific ligands and the best internalization pathways (caveolae mediated endocytosis) for safe cargo delivery will be discussed.

Achieving highly efficient gene transfer to the bladder by increasing the molecular weight of polymer-based nanoparticles

Short dwell-time and poor penetration of the bladder permeability barrier (BPB) are the main obstacles to intravesical treatments for bladder diseases, and is evidenced by the lack of such therapeutic options on the market. Herein, we demonstrate that by finely tuning the molecular weight of our cationic polymer mucoadhesive nanoparticles, we enhanced our gene transfer, leading to improved adherence and penetrance through the BPB in a safe and efficient manner. Specifically, increasing the polymer molecular weight from 45 kDa to 83 kDa enhanced luciferase plasmid transfer to the healthy murine bladder, leading to 1.35 ng/g luciferase protein expression in the urothelium and lamina propria regions. The relatively higher molecular weight polymer (83 kDa) did not induce morphologic changes or inflammatory responses in the bladder. This approach of altering polymer molecular weight for prolonging gene transfer residence time and deeper penetration through the BPB could be the basis for the design of future gene therapies for bladder diseases.

Dual-Modified Liposome for Targeted and Enhanced Gene Delivery into Mice Brain

The development of neuropharmaceutical gene delivery systems requires strategies to obtain efficient and effective brain targeting as well as blood-brain barrier (BBB) permeability. A brain-targeted gene delivery system based on a transferrin (Tf) and cell-penetrating peptide (CPP) dual-functionalized liposome, CPP-Tf-liposome, was designed and investigated for crossing BBB and permeating into the brain. We selected three sequences of CPPs [melittin, Kaposi fibroblast growth factor (kFGF), and penetration accelerating sequence-R8] and compared their ability to internalize into the cells and, subsequently, improve the transfection efficiency. Study of intracellular uptake indicated that liposomal penetration into bEnd.3 cells, primary astrocytes, and primary neurons occurred through multiple endocytosis pathways and surface modification with Tf and CPP enhanced the transfection efficiency of the nanoparticles. A coculture in vitro BBB model reproducing the in vivo anatomophysiological complexity of the biologic barrier was developed to characterize the penetrating properties of these designed liposomes. The dual-functionalized liposomes effectively crossed the in vitro barrier model followed by transfecting primary neurons. Liposome tissue distribution in vivo indicated superior ability of kFGF-Tf-liposomes to overcome BBB and reach brain of the mice after single intravenous administration. These findings demonstrate the feasibility of using strategically designed liposomes by combining Tf receptor targeting with enhanced cell penetration as a potential brain gene delivery vector. SIGNIFICANCE STATEMENT: Rational synthesis of efficient brain-targeted gene carrier included modification of liposomes with a target-specific ligand, transferrin, and with cell-penetrating peptide to enhance cellular internalization. Our study used an in vitro triple coculture blood-brain barrier (BBB) model as a tool to characterize the permeability across BBB and functionality of designed liposomes prior to in vivo biodistribution studies. Our study demonstrated that rational design and characterization of BBB permeability are efficient strategies for development of brain-targeted gene carriers.

Mussel-Inspired Polydopamine Coating Enhances the Intracutaneous Drug Delivery from Nanostructured Lipid Carriers Dependently on a Follicular Pathway

Inspired by the structure and function of the mussel adhesive protein, a facile strategy involving oxidative polymerization of dopamine was proposed for surface modification of nanostructured lipid carriers (NLCs) to promote drug delivery in the skin. The formation of a polydopamine (PDA) layer rounding the surface of NLCs was confirmed by the X-ray photoelectron spectroscopy and the Fourier transform infrared spectroscopy studies. Using terbinafine (TBF) as a model drug, the in vitro permeation study revealed that the PDA coating significantly enhanced the delivery of TBF from NLCs to the deep skin layers, where the follicular pathway played an essential role as suggested by the hair follicle blocking and differential tape stripping experiments, as well as the laser scanning confocal microscopy study by using Nile red as the fluorescent probe. The cellular investigation indicated that the PDA coating led to a higher cellular uptake of nanoparticles in human immortalized keratinocytes (HaCaT) without causing additional cytotoxicity. Using endocytic inhibitors, it was found that the lipid raft/caveolae-mediated endocytosis was strongly involved in the internalization of both the PDA modified and unmodified NLCs. Our results suggested that surface modification of NLCs with PDA coating improved the intracutaneous drug delivery mainly via the follicular pathway, which provided an avenue for the development of potential drug delivery carriers for dermal use.

Multifunctional REDV-G-TAT-G-NLS-Cys peptide sequence conjugated gene carriers to enhance gene transfection efficiency in endothelial cells

Rapid endothelialization on small diameter artificial blood vessels is an effective strategy to facilitate long-term patency and inhibit thrombosis. The gene delivery can enhance the proliferation and migration of endothelial cells (ECs), which is beneficial for rapid endothelialization. REDV-G-TAT-G-NLS-Cys (abbreviated as TP-G) peptide could weakly condense pEGFP-ZNF580 (pZNF580) and transfect ECs, but its transfection efficiency was still very low because of its low positive charge, low stability and weak endosome escape ability. In order to develop more stable and efficient gene carriers with low cytotoxicity, in the present study, we conjugated different amounts of TP-G peptide onto poly(lactide-co-glycolide)-g-polyethylenimine (PLGA-g-PEI) amphiphilic copolymers via a hetero-poly(ethylene glycol) spacer (OPSS-PEG-NHS). The TP-G peptide and PEI could cooperatively and strongly condense pZNF580. The carrier's cytotoxicity was reduced by the introduction of poly(ethylene glycol) spacer. They condensed pZNF580 to form gene complexes (PPP-TP-G/pZNF580) with suitable size and positive zeta potential for gene delivery. The transfected ECs promoted their migration ability as demonstrated by cell migration assay. The results of cellular uptake and confocal laser scanning microscopy showed significantly high internalization efficiency, endosomal/lysosomal escape and nucleus location of pZNF580 by this multifunctional TP-G peptide sequence conjugated gene delivery system. Furthermore, several inhibitors were used to study the cellular uptake pathways of PPP-TP-G/pZNF580 complexes. The results showed that PPP-TP-G2/Cy5-oligonucleotide complexes exhibited the optimized endocytosis pathways which facilitated for cellular uptake. In conclusion, the multifunctional TP-G peptide conjugated gene carriers could promote the transfection efficiency due to the multifunction of REDV, cell-penetrating peptide and nuclear localization signal in the peptide sequence, which could be a suitable gene carrier for endothelialization.

Development and screening of brain-targeted lipid-based nanoparticles with enhanced cell penetration and gene delivery properties

Background

The potential of gene therapy for treatment of neurological disorders can be explored using designed lipid-based nanoparticles such as liposomes, which have demonstrated ability to deliver nucleic acid to brain cells. We synthesized liposomes conjugated to cell-penetrating peptides (CPPs) (vascular endothelial-cadherin-derived peptide [pVec], pentapeptide QLPVM and HIV-1 trans-activating protein [TAT]) and transferrin (Tf) ligand, and examined the influence of surface modifications on the liposome delivery capacity and transfection efficiency of encapsulated plasmid DNA. The design of liposomes was based on targeting molecular recognition of transferrin receptor overexpressed on the blood–brain barrier (BBB) with enhanced internalization ability of CPPs.

Methods

CPP-Tf-liposomes were characterized by particle size distribution, zeta potential, protection of encapsulated plasmid DNA, uptake mechanisms and transfection efficiencies. An in vitro triple co-culture BBB model selected the liposomal formulations that were able to cross the in vitro BBB and subsequently, transfect primary neuronal cells. The in vivo biodistribution and biocompatibility of selected formulations were also investigated in mice.

Results

Liposomal formulations were able to protect the encapsulated plasmid DNA against enzymatic degradation and presented low hemolytic potential and low cytotoxicity at 100 nM phospholipid concentration. Cellular internalization of nanoparticles occurred via multiple endocytosis pathways. CPP-Tf-conjugated liposomes mediated robust transfection of brain endothelial (bEnd.3), primary glial and primary neuronal cells. Liposomes modified with Tf and TAT demonstrated superior ability to cross the barrier layer and subsequently, transfect neuronal cells compared to other formulations. Quantification of fluorescently labeled liposomes and in vivo imaging demonstrated that this system could efficiently overcome the BBB and penetrate the brain of mice (7.7% penetration of injected dose).

Conclusion

In vitro screening platforms are important tools to enhance the success of brain-targeted gene delivery systems. The potential of TAT-Tf-liposomes as efficient brain-targeted gene carriers in vitro and in vivo was suggested to be related to the presence of selected moieties on the nanoparticle surface.

Efficient siRNA delivery and gene silencing using a lipopolypeptide hybrid vector mediated by a caveolae-mediated and temperature-dependent endocytic pathway

Background

We developed a non-viral vector, a combination of HIV-1 Tat peptide modified with histidine and cysteine (mTat) and polyethylenimine, jetPEI (PEI), displaying the high efficiency of plasmid DNA transfection with little toxicity. Since the highest efficiency of INTERFERin (INT), a cationic amphiphilic lipid-based reagent, for small interfering RNA (siRNA) transfection among six commercial reagents was shown, we hypothesized that combining mTat/PEI with INT would improve transfection efficiency of siRNA delivery. To elucidate the efficacy of the hybrid vector for siRNA silencing, β-actin expression was measured after siRNA β-actin was transfected with mTat/PEI/INT or other vectors in HSC-3 human oral squamous carcinoma cells.

Results

mTat/PEI/INT/siRNA produced significant improvement in transfection efficiency with little cytotoxicity compared to other vectors and achieved ≈ 100% knockdown of β-actin expression compared to non-treated cells. The electric charge of mTat/PEI/INT/siRNA was significantly higher than INT/siRNA. The particle size of mTat/PEI/INT/siRNA was significantly smaller than INT/siRNA. Filipin III and β-cyclodextrin, an inhibitor of caveolae-mediated endocytosis, significantly inhibited mTat/PEI/INT/siRNA transfection, while chlorpromazine, an inhibitor of clathrin-mediated endocytosis, did not inhibit mTat/PEI/INT/siRNA transfection. Furthermore, the transfection efficiency of mTat/PEI/INT at 4 °C was significantly lower than 37 °C.

Conclusions

These findings demonstrated the feasibility of using mTat/PEI/INT as a potentially attractive non-viral vector for siRNA delivery.

Recent progress in nanomaterials for gene delivery applications

Nanotechnology-based gene delivery is the division of nanomedicine concerned with the synthesis, characterization, and functionalization of nanomaterials to be used in targeted-gene delivery applications. Nanomaterial-based gene delivery systems hold great promise for curing fatal inherited and acquired diseases, including neurological disorders, cancer, cardiovascular diseases, and acquired immunodeficiency syndrome (AIDS). However, their use in clinical applications is still controversial. To date, the Food and Drug Administration (FDA) has not approved any gene delivery system because of the unknown long-term toxicity and the low gene transfection efficiency of nanomaterials in vivo. Compared to viral vectors, nonviral gene delivery vectors are characterized by a low preexisting immunogenicity, which is important for preventing a severe immune response. In addition, nonviral vectors provide higher loading capacity and ease of fabrication. For these reasons, this review article focuses on applications of nonviral gene delivery systems, including those based on lipids, polymers, graphene, and other inorganic nanoparticles, and discusses recent advances in nanomaterials for gene therapy. Methods of synthesizing these nanomaterials are briefly described from a materials science perspective. Also, challenges, critical issues, and concerns about the in vivo applications of nanomaterial-based gene delivery systems are discussed. It should be noted that this article is not a comprehensive review of the literature.

Detailed investigation on how the protein corona modulates the physicochemical properties and gene delivery of polyethylenimine (PEI) polyplexes

Given the various cationic polymers developed as non-viral gene delivery vectors, polyethylenimine (PEI) has been/is frequently used in in vitro transfection.

Ex vivo nonviral gene delivery of μ-opioid receptor to attenuate cancer-induced pain

Virus-mediated gene delivery shows promise for the treatment of chronic pain. However, viral vectors have cytotoxicity. To avoid toxicities and limitations of virus-mediated gene delivery, we developed a novel nonviral hybrid vector: HIV-1 Tat peptide sequence modified with histidine and cysteine residues combined with a cationic lipid. The vector has high transfection efficiency with little cytotoxicity in cancer cell lines including HSC-3 (human tongue squamous cell carcinoma) and exhibits differential expression in HSC-3 (∼45-fold) relative to HGF-1 (human gingival fibroblasts) cells. We used the nonviral vector to transfect cancer with OPRM1, the μ-opioid receptor gene, as a novel method for treating cancer-induced pain. After HSC-3 cells were transfected with OPRM1, a cancer mouse model was created by inoculating the transfected HSC-3 cells into the hind paw or tongue of athymic mice to determine the analgesic potential of OPRM1 transfection. Mice with HSC-3 tumors expressing OPRM1 demonstrated significant antinociception compared with control mice. The effect was reversible with local naloxone administration. We quantified β-endorphin secretion from HSC-3 cells and showed that HSC-3 cells transfected with OPRM1 secreted significantly more β-endorphin than control HSC-3 cells. These findings indicate that nonviral delivery of the OPRM1 gene targeted to the cancer microenvironment has an analgesic effect in a preclinical cancer model, and nonviral gene delivery is a potential treatment for cancer pain.

cRGD/TAT Dual-Ligand Reversibly Cross-Linked Micelles Loaded with Docetaxel Penetrate Deeply into Tumor Tissue and Show High Antitumor Efficacy in Vivo

The application of cell-penetrating peptides like TAT for in vivo targeted delivery is limited because the penetration behavior is not cell-specific. Herein, we designed cRGD and TAT comodified cross-linkable micelles (cRGD/TAT CMs), in which the TAT peptide was shielded by relatively long poly(ethylene glycol) (PEG) chains. Docetaxel (DTX)-loaded cRGD/TAT CMs were very stable with minimal drug leakage under physiological conditions, whereas rapid DTX release took place in a reductive environment. Flow cytometry showed that the cRGD/TAT CMs with molar ratios of 20% cRGD and 10% TAT (cRGD20/TAT10 CMs) were selectively and efficiently taken up by α_νβ₃-overexpressing U87MG glioma cells, with 8.3-fold and 18.3-fold higher uptake than cRGD20 CMs and PEG CMs, respectively. DTX-loaded cRGD20/TAT10 CMs exhibited a high cytotoxicity in U87MG cells, leading to rapid apoptosis of the tumor cells. Uptake mechanism studies revealed that cRGD20/TAT10 CMs mainly employed the caveolae-mediated endocytotic pathway and efficiently escaped from the lysosomes. Notably, cRGD20/TAT10 CMs had a long circulating time of 6.25 h in vivo, due to cross-linking of the micelles and shielding of the TAT peptide. Moreover, DTX-loaded cRGD20/TAT10 CMs exhibited a significantly higher accumulation and deeper penetration in subcutaneous U87MG glioma tissue compared to cRGD20 CMs and PEG CMs, leading to superior antitumor efficacy in vivo. Therefore, this dual-ligand strategy provides an effective way to realize tumor-specific penetration and inhibition.

Efficient Dual siRNA and Drug Delivery Using Engineered Lipoproteoplexes

An engineered supercharged coiled-coil protein (CSP) and the cationic transfection reagent Lipofectamine 2000 are combined to form a lipoproteoplex for the purpose of dual delivery of siRNA and doxorubicin. CSP, bearing an external positive charge and axial hydrophobic pore, demonstrates the ability to condense siRNA and encapsulate the small-molecule chemotherapeutic, doxorubicin. The lipoproteoplex demonstrates improved doxorubicin loading relative to Lipofectamine 2000. Furthermore, it induces effective transfection of GAPDH (60% knockdown) in MCF-7 breast cancer cells with efficiencies comparing favorably to Lipofectamine 2000. When the lipoproteoplex is loaded with doxorubicin, the improved doxorubicin loading (∼40 μg Dox/mg CSP) results in a substantial decrease in MCF-7 cell viability.

Protein based therapeutic delivery agents: Contemporary developments and challenges

As unique biopolymers, proteins can be employed for therapeutic delivery. They bear important features such as bioavailability, biocompatibility, and biodegradability with low toxicity serving as a platform for delivery of various small molecule therapeutics, gene therapies, protein biologics and cells. Depending on size and characteristic of the therapeutic, a variety of natural and engineered proteins or peptides have been developed. This, coupled to recent advances in synthetic and chemical biology, has led to the creation of tailor-made protein materials for delivery. This review highlights strategies employing proteins to facilitate the delivery of therapeutic matter, addressing the challenges for small molecule, gene, protein and cell transport.

Non-viral nucleic acid delivery methods

INTRODUCTION

Delivery of nucleic acid-based molecules in human cells is a highly studied approach for the treatment of several disorders including monogenic diseases and cancers. Non-viral vectors for DNA and RNA transfer, although in general less efficient than virus-based systems, are particularly well adapted mostly due to the absence of biosafety concerns. Non-viral methods could be classified in two main groups: physical and vector-assisted delivery systems. Both groups comprise several different methods, none of them universally applicable. The choice of the optimal method depends on the predefined objectives and the features of targeted micro-environment. Areas covered: In this review, the authors discuss non-viral techniques and present recent therapeutic achievements in ex vivo and in vivo nucleic acid delivery by most commonly used techniques while emphasizing the role of 'biological particles', namely peptide transduction domains, virus like particles, gesicles and exosomes. Expert opinion: The number of available non-viral transfection techniques used for human therapy increased rapidly, followed by still moderate success in efficacy. The prospects are to be found in design of multifunctional hybrid systems that reflect the viral efficiency. In this respect, biological particles are very promising.

Co-delivery of drugs and plasmid DNA for cancer therapy

Cancer is an extremely complex disease involving multiple signaling pathways that enable tumor cells to evade programmed cell death, thus making cancer treatment extremely challenging. The use of combination therapy involving both gene therapy and chemotherapy has resulted in enhanced anti-cancer effects and has become an increasingly important strategy in medicine. This review will cover important design parameters that are incorporated into delivery systems for the co-administration of drug and plasmid-based nucleic acids (pDNA and shRNA), with particular emphasis on polymers as delivery materials. The unique challenges faced by co-delivery systems and the strategies to overcome such barriers will be discussed. In addition, the advantages and disadvantages of combination therapy using separate carrier systems versus the use of a single carrier will be evaluated. Finally, future perspectives in the design of novel platforms for the combined delivery of drugs and genes will be presented.

Nanoparticles as transfection agents: a comprehensive study with ten different cell lines

The performance of transfection agents to deliver nucleic acids into cells strongly depends on the cell type.

Endocytotic routes of cobra cardiotoxins depend on spatial distribution of positively charged and hydrophobic domains to target distinct types of sulfated glycoconjugates on cell surface

Cobra cardiotoxins (CTX) are a family of three-fingered basic polypeptides known to interact with diverse targets such as heparan sulfates, sulfatides, and integrins on cell surfaces. After CTX bind to the membrane surface, they are internalized to intracellular space and exert their cytotoxicity via an unknown mechanism. By the combined in vitro kinetic binding, three-dimensional x-ray structure determination, and cell biology studies on the naturally abundant CTX homologues from the Taiwanese cobra, we showed that slight variations on the spatial distribution of positively charged or hydrophobic domains among CTX A2, A3, and A4 could lead to significant changes in their endocytotic pathways and action mechanisms via distinct sulfated glycoconjugate-mediated processes. The intracellular locations of these structurally similar CTX after internalization are shown to vary between the mitochondria and lysosomes via either dynamin2-dependent or -independent processes with distinct membrane cholesterol sensitivity. Evidence is presented to suggest that the shifting between the sulfated glycoconjugates as distinct targets of CTX A2, A3, and A4 might play roles in the co-evolutionary arms race between venomous snake toxins to cope with different membrane repair mechanisms at the cellular levels. The sensitivity of endocytotic routes to the spatial distribution of positively charged or hydrophobic domains may provide an explanation for the diverse endocytosis pathways of other cell-penetrating basic polypeptides.

Gene delivery from supercharged coiled-coil protein and cationic lipid hybrid complex

A lipoproteoplex comprised of an engineered supercharged coiled-coil protein (CSP) bearing multiple arginines and the cationic lipid formulation FuGENE HD (FG) was developed for effective condensation and delivery of nucleic acids. The CSP was able to maintain helical structure and self-assembly properties while exhibiting binding to plasmid DNA. The ternary CSP·DNA(8:1)·FG lipoproteoplex complex demonstrated enhanced transfection of β-galactosidase DNA into MC3T3-E1 mouse preosteoblasts. The lipoproteoplexes showed significant increases in transfection efficiency when compared to conventional FG and an mTat·FG lipopolyplex with a 6- and 2.5-fold increase in transfection, respectively. The CSP·DNA(8:1)·FG lipoproteoplex assembled into spherical particles with a net positive surface charge, enabling efficient gene delivery. These results support the application of lipoproteoplexes with protein engineered CSP for non-viral gene delivery.

Influence of pDNA availability on transfection efficiency of polyplexes in non-proliferative cells

We succeeded in visualizing plasmid DNA (pDNA) in the nucleus and cytosol of non-proliferative cells after transfection with linear polyethylenemine (lPEI) and histidinylated lPEI (His16-lPEI). This was possible with confocal microscope by using pDNA labelled with quantum dots. Indeed pDNA labelled with Cy3 leads to false positive nuclear localization because the saturation of the fluorescence signal overestimated the volume occupied by Cy3-pDNA. Moreover, Cy3 brightness was too weak to detect low amount of pDNA. About 20 to 40 pDNA copies were detected in the nucleus after the transfection of pDNA labelled with quantum dots. Transfection efficiency and cellular imaging data suggested that the cytosolic availability of pDNA, including endosome escape and/or polyplexes dissociation, is crucial for its nuclear delivery. In vitro transcription assay and transfection of cells allowing cytosolic gene expression concluded to better cytosolic availability of pDNA within His16-lPEI polyplexes. Cryo-TEM analyses revealed that His16-lPEI polyplexes exhibited a spherical shape and an amorphous internal structure which differed from the high degree of order of lPEI polyplexes. Altogether, this comparative study indicated that the high transfection efficiency of non-proliferative cells with His16-lPEI polyplexes was related to the amorphous structure and the facilitated dissociation of the assemblies.

Development of a non-viral gene delivery vector based on the dynein light chain Rp3 and the TAT peptide

Gene therapy and DNA vaccination trials are limited by the lack of gene delivery vectors that combine efficiency and safety. Hence, the development of modular recombinant proteins able to mimic mechanisms used by viruses for intracellular trafficking and nuclear delivery is an important strategy. We designed a modular protein (named T-Rp3) composed of the recombinant human dynein light chain Rp3 fused to an N-terminal DNA-binding domain and a C-terminal membrane active peptide, TAT. The T-Rp3 protein was successfully expressed in Escherichia coli and interacted with the dynein intermediate chain in vitro. It was also proven to efficiently interact and condense plasmid DNA, forming a stable, small (∼100nm) and positively charged (+28.6mV) complex. Transfection of HeLa cells using T-Rp3 revealed that the vector is highly dependent on microtubule polarization, being 400 times more efficient than protamine, and only 13 times less efficient than Lipofectamine 2000™, but with a lower cytotoxicity. Confocal laser scanning microcopy studies revealed perinuclear accumulation of the vector, most likely as a result of transport via microtubules. This study contributes to the development of more efficient and less cytotoxic proteins for non-viral gene delivery.

Ternary nanoparticles composed of cationic solid lipid nanoparticles, protamine, and DNA for gene delivery

Background

The objective of this research was to design an effective gene delivery system composed of cationic solid lipid nanoparticles (SLNs), protamine, and Deoxyribonucleic acid DNA.

Methods

Cationic SLNs were prepared using an aqueous solvent diffusion method with octadecylamine as the cationic lipid material. First, protamine was combined with DNA to form binary protamine/DNA nanoparticles, and the ternary nanoparticle gene delivery system was then obtained by combining binary protamine/DNA nanoparticles with cationic SLNs. The size, zeta potential, and ability of the binary and ternary nanoparticles to compact and protect DNA were characterized. The effect of octadecylamine content in SLNs and the SLNS/DNA ratios on transfection efficiency, cellular uptake and cytotoxicity of the ternary nanoparticles were also assessed using HEK293 cells.

Results

When the weight ratio of protamine to DNA reached 1.5:1, the plasmid DNA could be effectively compacted and protected. The average hydrodynamic diameter of the ternary nanoparticles when combined with protamine increased from 188.50 ± 0.26 nm to 259.33 ± 3.44 nm, and the zeta potential increased from 25.50 ± 3.30 mV to 33.40 ± 2.80 mV when the weight ratio of SLNs to DNA increased from 16/3 to 80/3. The ternary nanoparticles showed high gene transfection efficiency compared with Lipofectamine™ 2000/DNA nanoparticles. Several factors that might affect gene transfection efficiency, such as content and composition of SLNs, post-transfection time, and serum were examined. The ternary nanoparticles composed of SLNs with 15 wt% octadecylamine (50/3 weight ratio of SLNs to DNA) showed the best transfection efficiency (26.13% ± 5.22%) in the presence of serum. It was also found that cellular uptake of the ternary nanoparticles was better than that of the SLN/DNA and binary protamine/DNA nanoparticle systems, and DNA could be transported to the nucleus.

Conclusion

SLNs enhanced entry of binary protamine/DNA nanoparticles into the cell, and protamine protected DNA from enzyme degradation and transported DNA into the nucleus. Compared with Lipofectamine 2000/DNA nanoparticles, these cationic ternary nanoparticles showed relatively durable and stable gene transfection in the presence of serum.

Multifunctional nanomicellar systems for delivering anticancer drugs

Most anticancer drugs cause severe side effect due to the lack of selectivity for cancer cells. In recent years, new strategies of micellar systems, which design for specifically target anticancer drugs to tumors, are developed at the forefront of polymeric science. To improve efficiency of delivery and cancer specificity, considerable emphasis has been placed on the development of micellar systems with passive and active targeting. In this review article, we summarized various strategies of designing multifunctional micellar systems in the purpose of improving delivery efficiency. Micellar systems compose of a multifunctional copolymer or a mixture of two or more copolymers with different properties is a plausible approach to tuning the resulting properties and satisfied various requirements for anticancer drug delivery. It appears that multifunctional micellar systems hold great potential in cancer therapy.

Bioreducible poly(amido amine)s with different branching degrees as gene delivery vectors

Based on the knowledge that cationic polymers with different topographical structures behave differently in gene transfection process, herein, we synthesized three biodegradable poly(amido amine)s (PAAs) with the same repeating units and molecular weights except for degree of branching: linear PAA (LPAA), low-branched PAA (LBPAA), and high-branched PAA (HBPAA). We found that LBPAA could more effectively compact pDNA into positively charged nanoparticles than both HBPAA and LPAA. LBPAA polyplexes had the highest transfection efficiency among the three PAA polyplexes, and the difference in transfection efficiency is mainly attributed to the endocytosis rate. The cytotoxicity of PAAs was negligible at the transfection doses, probably due to the degradable disulfide bonds. Therefore, we could use branching as a parameter to simply tune a polymer's cellular uptake behavior and transfection efficiency.

Surface modified poly(β amino ester)-containing nanoparticles for plasmid DNA delivery

The use of biodegradable polymers provides a potentially safe and effective alternative to viral and liposomal vectors for the delivery of plasmid DNA to cells for gene therapy applications. In this work we describe the formulation of a novel nanoparticle (NP) system containing a blend of poly(lactic-co-glycolic acid) and a representative poly(beta-amino) ester (PLGA and PBAE respectively) for use as gene delivery vehicles. Particles of different weight/weight (wt/wt) ratios of the two polymers were characterized for size, morphology, plasmid DNA (pDNA) loading and surface charge. NPs containing PBAE were more effective at cellular internalization and transfection (COS-7 and CFBE41o-) than NPs lacking the PBAE polymer. However, along with these delivery benefits, PBAE exhibited cytotoxic effects that presented an engineering challenge. Surface coating of these blended particles with the cell-penetrating peptides (CPPs) mTAT, bPrPp and MPG via a PEGylated phospholipid linker (DSPE-PEG2000) resulted in NPs that reduced surface charge and cellular toxicity to levels comparable with NPs formulated with only PLGA. Additionally, these coated nanoparticles showed an improvement in pDNA loading, intracellular uptake and transfection efficiency, when compared to NPs lacking the surface coating. Although all particles with a CPP coating outperformed unmodified NPs, respectively, bPrPp and MPG coating resulted in 3 and 4.5× more pDNA loading than unmodified particles and approximately an order of magnitude improvement on transfection efficiency in CFBE41o- cells. These results demonstrate that surface-modified PBAE containing NPs are a highly effective and minimally toxic platform for pDNA delivery.

Application of poly(ethylene glycol)-distearoylphosphatidylethanolamine (PEG-DSPE) block copolymers and their derivatives as nanomaterials in drug delivery

Poly(ethylene glycol)–distearoylphosphatidylethanolamine (PEG-DSPE) block copolymers are biocompatible and amphiphilic polymers that can be widely utilized in the preparation of liposomes, polymeric nanoparticles, polymer hybrid nanoparticles, solid lipid nanoparticles, lipid–polymer hybrid nanoparticles, and microemulsions. Particularly, the terminal groups of PEG can be activated and linked to various targeting ligands, which can prolong the circulation time, improve the drug bioavailability, reduce undesirable side effects, and especially target specific cells, tissues, and even the intracellular localization in organelles. This review herein aims to describe recent developments in drug carriers exploiting PEG-DSPE block copolymers and their derivatives, and the incorporation of different ligands to the end groups of PEG-DSPE to target delivery, focusing on their modification approaches, advantages, applications, and the probable associated drawbacks.

Biological activities of histidine-rich peptides; merging biotechnology and nanomedicine

Histidine-rich peptides are commonly used in recombinant protein production as purification tags, allowing the one-step affinity separation of the His-tagged proteins from the extracellular media or cell extracts. Genetic engineering makes feasible the post-purification His-tag removal by inserting, between the tag and the main protein body, a target site for trans-acting proteases or a self-proteolytic peptide with regulatable activities. However, for technical ease, His tags are often not removed and the fusion proteins eventually used in this form. In this commentary, we revise the powerful biological properties of histidine-rich peptides as endosomolytic agents and as architectonic tags in nanoparticle formation, for which they are exploited in drug delivery and other nanomedical applications. These activities, generally unknown to biotechnologists, can unwillingly modulate the functionality and biotechnological performance of recombinant proteins in which they remain trivially attached.