Genetic blockage of endocytic pathways reveals differences in the intracellular processing of non-viral gene delivery systems

Near-Infrared Emissive Super Penetrating Conjugated Polymer Dots for Intratumoral Imaging in 3D Tumor Spheroid Models

This study describes the formation of single-chain polymer dots (Pdots) via ultrasonic emulsification of nonionic donor-acceptor-donor type (D-A-D) alkoxy thiophene-benzobisthiadiazole-based conjugated polymers (Poly BT) with amphiphilic cetyltrimethylammonium bromide (CTAB). The methodology yields Pdots with a high cationic surface charge (+56.5 mV ± 9.5) and average hydrodynamic radius of 12 nm. Optical characterization reveals that these Pdots emit near-infrared (NIR) light at a maximum wavelength of 860 nm owing to their conjugated polymer backbone consisting of D-A-D monomers. Both colloidal and optical properties of these Pdots make them promising fluorescence emissive probes for bioimaging applications. The significant advantage of positively charged Pdots is demonstrated in diffusion-limited mediums such as tissues, utilizing human epithelial breast adenocarcinoma, ATCC HTB-22 (MCF-7), human bone marrow neuroblastoma, ATCC CRL-2266 (SH-SY5Y), and rat adrenal gland pheochromocytoma, CRL-1721 (PC-12) tumor spheroid models. Fluorescence microscopy analysis of tumor spheroids from MCF-7, SH-SY5Y, and PC-12 cell lines reveals the intensity profile of Pdots, confirming extensive penetration into the central regions of the models. Moreover, a comparison with mitochondria staining dye reveals an overlap between the regions stained by Pdots and the dye in all three tumor spheroid models. These results suggest that single-chain D-A-D type Pdots, cationized via CTAB, exhibit long-range mean free path of penetration (≈1 µm) in dense mediums and tumors.

MicroRNAs as therapeutic targets in breast cancer metastasis

Breast cancer is a complex disease with multiple risk factors involved in its pathogenesis. Among these factors, microRNAs are considered for playing a fundamental role in the development and progression of malignant breast tumors. In recent years, various studies have demonstrated that several microRNAs exhibit increased or decreased expression in metastatic breast cancer, acting as indicators of metastatic potential in body fluids and tissue samples. The identification of these microRNA expression patterns could prove instrumental for the development of novel therapeutic molecules that either mimic or inhibit microRNA action. Additionally, an efficient delivery system mediated by viral vectors, nonviral carriers, or scaffold biomaterials is a prerequisite for implementing microRNA-based therapies; therefore, this review attempts to highlight essential microRNA molecules involved in the metastatic process of breast cancer and discuss recent advances in microRNA-based therapeutic approaches with potential future applications to the treatment sequence of breast cancer.

Polycation-Mediated Transfection: Mechanisms of Internalization and Intracellular Trafficking

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

Nanoassemblies with Effective Serum Tolerance Capability Achieving Robust Gene Silencing Efficacy for Breast Cancer Gene Therapy

The transfection efficiency of siRNA mediated by cationic polymers is limited due to the instability of polymers/siRNA complexes in the presence of serum. Poly(ethylene glycol) (PEG) is usually applied to modify cationic polymers, so as to reduce protein and cell adsorption and then to improve siRNA transfection efficiency. However, the polymers' modification with PEG mostly consumes the free amino of the polymers, which can, in turn, reduce the charge density and limit their siRNA transfection efficacy. Here, a new PEG modification strategy that need not consume the surface aminos of polymers is proposed. Catechol-PEG polymers are coated on the surface of phenylboronic acid (PBA)-modified Generation 5 (G5) poly(amidoamine) dendrimers (G5PBA) via reversible boronate esters to establish PEG-modified dendrimer/siRNA nanoassemblies for efficient siRNA delivery. The PEG/G5PBA/siRNA nanoassemblies have positive charge and show excellent gene silencing efficacy in the absence of serum in vitro. More importantly, the PEG/G5PBA/siRNA nanoassemblies also exhibit excellent serum resistance and gene silencing efficacy in serum-containing medium. Furthermore, the effective antiserum and gene silencing efficacy elicited by these nanoassemblies lead to excellent antitumor effects in vivo. This proposed strategy constitutes an important approach to reach an excellent gene silencing efficacy in the presence of serum.

Niosome-Based Approach for In Situ Gene Delivery to Retina and Brain Cortex as Immune-Privileged Tissues

Non-viral vectors have emerged as a promising alternative to viral gene delivery systems due to their safer profile. Among non-viral vectors, recently, niosomes have shown favorable properties for gene delivery, including low toxicity, high stability, and easy production. The three main components of niosome formulations include a cationic lipid that is responsible for the electrostatic interactions with the negatively charged genetic material, a non-ionic surfactant that enhances the long-term stability of the niosome, and a helper component that can be added to improve its physicochemical properties and biological performance. This review is aimed at providing recent information about niosome-based non-viral vectors for gene delivery purposes. Specially, we will discuss the composition, preparation methods, physicochemical properties, and biological evaluation of niosomes and corresponding nioplexes that result from the addition of the genetic material onto their cationic surface. Next, we will focus on the in situ application of such niosomes to deliver the genetic material into immune-privileged tissues such as the brain cortex and the retina. Finally, as future perspectives, non-invasive administration routes and different targeting strategies will be discussed.

Scaffold-Based microRNA Therapies in Regenerative Medicine and Cancer

microRNA-based therapies are an advantageous strategy with applications in both regenerative medicine (RM) and cancer treatments. microRNAs (miRNAs) are an evolutionary conserved class of small RNA molecules that modulate up to one third of the human nonprotein coding genome. Thus, synthetic miRNA activators and inhibitors hold immense potential to finely balance gene expression and reestablish tissue health. Ongoing industry-sponsored clinical trials inspire a new miRNA therapeutics era, but progress largely relies on the development of safe and efficient delivery systems. The emerging application of biomaterial scaffolds for this purpose offers spatiotemporal control and circumvents biological and mechanical barriers that impede successful miRNA delivery. The nascent research in scaffold-mediated miRNA therapies translates know-how learnt from studies in antitumoral and genetic disorders as well as work on plasmid (p)DNA/siRNA delivery to expand the miRNA therapies arena. In this progress report, the state of the art methods of regulating miRNAs are reviewed. Relevant miRNA delivery vectors and scaffold systems applied to-date for RM and cancer treatment applications are discussed, as well as the challenges involved in their design. Overall, this progress report demonstrates the opportunity that exists for the application of miRNA-activated scaffolds in the future of RM and cancer treatments.

Extracellular retention of a cyclopamine nanoformulation leveraging larger size and more negative charge for improved breast cancer treatment

We achieved greater extracellular retention of nanoparticles, by leveraging their larger size and negative charge, for improving the effects of a drug with extracellular targeting sites.

Nanotechnology-Based Cardiac Targeting and Direct Cardiac Reprogramming: The Betrothed

Cardiovascular diseases represent the first cause of morbidity in Western countries, and chronic heart failure features a significant health care burden in developed countries. Efforts in the attempt of finding new possible strategies for the treatment of CHF yielded several approaches based on the use of stem cells. The discovery of direct cardiac reprogramming has unveiled a new approach to heart regeneration, allowing, at least in principle, the conversion of one differentiated cell type into another without proceeding through a pluripotent intermediate. First developed for cancer treatment, nanotechnology-based approaches have opened new perspectives in many fields of medical research, including cardiovascular research. Nanotechnology could allow the delivery of molecules with specific biological activity at a sustained and controlled rate in heart tissue, in a cell-specific manner. Potentially, all the mediators and structural molecules involved in the fibrotic process could be selectively targeted by nanocarriers, but to date, only few experiences have been made in cardiac research. This review highlights the most prominent concepts that characterize both the field of cardiac reprogramming and a nanomedicine-based approach to cardiovascular diseases, hypothesizing a possible synergy between these two very promising fields of research in the treatment of heart failure.

Delivering Nucleic-Acid Based Nanomedicines on Biomaterial Scaffolds for Orthopedic Tissue Repair: Challenges, Progress and Future Perspectives

As well as acting to fill defects and allow for cell infiltration and proliferation in regenerative medicine, biomaterial scaffolds can also act as carriers for therapeutics, further enhancing their efficacy. Drug and protein delivery on scaffolds have shown potential, however, supraphysiological quantities of therapeutic are often released at the defect site, causing off-target side effects and cytotoxicity. Gene therapy involves the introduction of foreign genes into a cell in order to exert an effect; either replacing a missing gene or modulating expression of a protein. State of the art gene therapy also encompasses manipulation of the transcriptome by harnessing RNA interference (RNAi) therapy. The delivery of nucleic acid nanomedicines on biomaterial scaffolds - gene-activated scaffolds -has shown potential for use in a variety of tissue engineering applications, but as of yet, have not reached clinical use. The current state of the art in terms of biomaterial scaffolds and delivery vector materials for gene therapy is reviewed, and the limitations of current procedures discussed. Future directions in the clinical translation of gene-activated scaffolds are also considered, with a particular focus on bone and cartilage tissue regeneration.

Temporal endogenous gene expression profiles in response to polymer-mediated transfection and profile comparison to lipid-mediated transfection

BACKGROUND

Design of efficient nonviral gene delivery systems is limited by the rudimentary understanding of specific molecules that facilitate transfection.

METHODS

Polyplexes using 25-kDa polyethylenimine (PEI) and plasmid-encoding green fluorescent protein (GFP) were delivered to HEK 293T cells. After treating cells with polyplexes, microarrays were used to identify endogenous genes differentially expressed between treated and untreated cells (2 h of exposure) or between flow-separated transfected cells (GFP+) and treated, untransfected cells (GFP-) at 8, 16 and 24 h after lipoplex treatment. Cell priming studies were conducted using pharmacologic agents to alter endogenous levels of the identified differentially expressed genes to determine effect on transfection levels. Differentially expressed genes in polyplex-mediated transfection were compared with those differentially expressed in lipoplex transfection to identify DNA carrier-dependent molecular factors.

RESULTS

Differentially expressed genes were RGS1, ARHGAP24, PDZD2, SNX24, GSN and IGF2BP1 after 2 h; RAP1A and ACTA1 after 8 h; RAP1A, WDR78 and ACTA1 after 16 h; and RAP1A, SCG5, ATF3, IREB2 and ACTA1 after 24 h. Pharmacologic studies altering endogenous levels for ARHGAP24, GSN, IGF2BP1, PDZD2 and RGS1 were able to increase or decrease transgene production. Comparing differentially expressed genes for polyplexes and lipoplexes, no common genes were identified at the 2-h time point, whereas, after the 8-h time point, RAP1A, ATF3 and HSPA6 were similarly expressed. SCG5 and PGAP1 were only upregulated in polyplex-transfected cells.

CONCLUSIONS

The identified genes and pharmacologic agents provide targets for improving transfection systems, although polyplex or lipoplex dependencies must be considered.

Parameters and characteristics governing cellular internalization and trans-barrier trafficking of nanostructures

Cellular internalization and trans-barrier transport of nanoparticles can be manipulated on the basis of the physicochemical and mechanical characteristics of nanoparticles. Research has shown that these factors significantly influence the uptake of nanoparticles. Dictating these characteristics allows for the control of the rate and extent of cellular uptake, as well as delivering the drug-loaded nanosystem intra-cellularly, which is imperative for drugs that require a specific cellular level to exert their effects. Additionally, physicochemical characteristics of the nanoparticles should be optimal for the nanosystem to bypass the natural restricting phenomena of the body and act therapeutically at the targeted site. The factors at the focal point of emerging smart nanomedicines include nanoparticle size, surface charge, shape, hydrophobicity, surface chemistry, and even protein and ligand conjugates. Hence, this review discusses the mechanism of internalization of nanoparticles and ideal nanoparticle characteristics that allow them to evade the biological barriers in order to achieve optimal cellular uptake in different organ systems. Identifying these parameters assists with the progression of nanomedicine as an outstanding vector of pharmaceuticals.

Histone-targeted Polyplexes Avoid Endosomal Escape and Enter the Nucleus During Postmitotic Redistribution of ER Membranes

Nonviral gene delivery is a promising therapeutic approach because of its safety and controllability, yet limited gene transfer efficacy is a common issue. Most nonviral strategies rely upon endosomal escape designs; however, endosomal escape is often uncorrelated with improved gene transfer and membranolytic structures are typically cytotoxic. Previously, we showed that histone-targeted polyplexes trafficked to the nucleus through an alternative route involving caveolae and the Golgi and endoplasmic reticulum (ER), using pathways similar to several pathogens. We hypothesized that the efficacy of these polyplexes was due to an increased utilization of native vesicular trafficking as well as regulation by histone effectors. Accordingly, using confocal microscopy and cellular fractionation, we determined that a key effect of histone-targeting was to route polyplexes away from clathrin-mediated recycling pathways by harnessing endomembrane transfer routes regulated by histone methyltransferases. An unprecedented finding was that polyplexes accumulated in Rab6-labeled Golgi/ER vesicles and ultimately shuttled directly into the nucleus during ER-mediated nuclear envelope reassembly. Specifically, super resolution microscopy and fluorescence correlation spectroscopy unequivocally indicated that the polyplexes remained associated with ER vesicles/membranes until mitosis, when they were redistributed into the nucleus. These novel findings highlight alternative mechanisms to subvert endolysosomal trafficking and harness the ER to enhance gene transfer.

The endocytic pathway and therapeutic efficiency of doxorubicin conjugated cholesterol-derived polymers

Previously synthesized poly(methacrylic acid-co-cholesteryl methacrylate) P(MAA-co-CMA) copolymers were examined as potential drug delivery vehicles.

A novel collagen-nanohydroxyapatite microRNA-activated scaffold for tissue engineering applications capable of efficient delivery of both miR-mimics and antagomiRs to human mesenchymal stem cells

Manipulation of gene expression through the use of microRNAs (miRNAs) offers tremendous potential for the field of tissue engineering. However, the lack of sufficient site-specific and bioactive delivery systems has severely hampered the clinical translation of miRNA-based therapies. In this study, we developed a novel non-viral bioactive delivery platform for miRNA mimics and antagomiRs to allow for a vast range of therapeutic applications. By combining nanohydroxyapatite (nHA) particles with reporter miRNAs (nanomiRs) and collagen-nanohydroxyapatite scaffolds, this work introduces the first non-viral, non-lipid platform to date, capable of efficient delivery of mature miRNA molecules to human mesenchymal stem cells (hMSCs), a particularly difficult cell type to transfect effectively, with minimal treatment-associated cytotoxicity. Firstly, miRNAs were successfully delivered to hMSCs in monolayer, with internalisation efficiencies of 17.4 and 39.6% for nanomiR-mimics and nanoantagomiRs respectively, and both nanomiR-mimics and nanoantagomiRs yielded sustained interfering activity of greater than 90% in monolayer over 7 days. When applied to 3D scaffolds, significant RNA interference of 20% for nanomiR-mimics and 88.4% for nanoantagomiRs was achieved with no cytotoxicity issues over a 7 day period. In summary, in-house synthesised non-viral nHA particles efficiently delivered reporter miRNAs both in monolayer and on scaffolds demonstrating the immense potential of this innovative miRNA-activated scaffold system for tissue engineering applications.

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

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

Noncovalently associated cell-penetrating peptides for gene delivery applications

The use of various cell-penetrating peptides (CPPs) to deliver genetic material for gene therapy applications has been a topic of interest for more than 20 years. The delivery of genetic material by using CPPs can be divided into two categories: covalently bound and electrostatically bound. Complexity of the synthesis procedure can be a significant barrier to translation when using a strategy requiring covalent binding of CPPs. In contrast, electrostatically complexing CPPs with genetic material or with a viral vector is relatively simple and has been demonstrated to improve gene delivery in both in vitro and in vivo studies. This review highlights gene therapy applications of complexes formed noncovalently between CPPs and genetic material or viruses.