Non-viral transfection vectors: are hybrid materials the way forward?

In vivo rescue of arboviruses directly from subgenomic DNA fragments

Reverse genetic systems are mainly used to rescue recombinant viral strains in cell culture. These tools have also been used to generate, by inoculating infectious clones, viral strains directly in living animals. We previously developed the "Infectious Subgenomic Amplicons" (ISA) method, which enables the rescue of single-stranded positive sense RNA viruses in vitro by transfecting overlapping subgenomic DNA fragments. Here, we provide proof-of-concept for direct in vivo generation of infectious particles following the inoculation of subgenomic amplicons. First, we rescued a strain of tick-borne encephalitis virus in mice to transpose the ISA method in vivo. Subgenomic DNA fragments were amplified using a 3-fragment reverse genetics system and inoculated intramuscularly. Almost all animals were infected when quantities of DNA inoculated were at least 20 µg. We then optimized our procedure in order to increase the animal infection rate. This was achieved by adding an electroporation step and/or using a simplified 2- fragment reverse genetics system. Under optimal conditions, a large majority of animals were infected with doses of 20 ng of DNA. Finally, we demonstrated the versatility of this method by applying it to Japanese encephalitis and Chikungunya viruses. This method provides an efficient strategy for in vivo rescue of arboviruses. Furthermore, in the context of the development of DNA-launched live attenuated vaccines, this new approach may facilitate the generation of attenuated strains in vivo. It also enables to deliver a substance free of any vector DNA, which seems to be an important criterion for the development of human vaccines.

Smart nanocarriers for enzyme-activated prodrug therapy

Exogenous enzyme-activated prodrug therapy (EPT) is a potential cancer treatment strategy that delivers non-human enzymes into or on the surface of the cell and subsequently converts a non-toxic prodrug into an active cytotoxic substance at a specific location and time. The development of several pharmacological pairs based on EPT has been the focus of anticancer research for more than three decades. Numerous of these pharmacological pairs have progressed to clinical trials, and a few have achieved application in specific cancer therapies. The current review highlights the potential of enzyme-activated prodrug therapy as a promising anticancer treatment. Different microbial, plant, or viral enzymes and their corresponding prodrugs that advanced to clinical trials have been listed. Additionally, we discuss new trends in the field of enzyme-activated prodrug nanocarriers, including nanobubbles combined with ultrasound (NB/US), mesoscopic-sized polyion complex vesicles (PICsomes), nanoparticles, and extracellular vesicles (EVs), with special emphasis on smart stimuli-triggered drug release, hybrid nanocarriers, and the main application of nanotechnology in improving prodrugs.

Targeted gene therapy for cancer: the impact of microRNA multipotentiality

Cancer is a life-threatening disease and its management is difficult due to its complex nature. Cancer is characterized by genomic instability and tumor-associated inflammation of the supporting stoma. With the advances in omics science, a treatment strategy for cancer has emerged, which is based on targeting cancer-driving molecules, known as targeted therapy. Gene therapy, a form of targeted therapy, is the introduction of nucleic acids into living cells to replace a defective gene, promote or repress gene expression to treat a disease. MicroRNAs (miRNAs) are non-coding RNAs (ncRNAs) that regulate gene expression and thus are involved in physiological processes like cell proliferation, differentiation, and cell death. miRNAs control the actions of many genes. They are deregulated in cancer and their abnormal expression influences genetic and epigenetic alterations inducing carcinogenesis. In this review, we will explain the role of miRNAs in normal and abnormal gene expression and their usefulness in monitoring cancer patients. Besides, we will discuss miRNA-based therapy as a method of gene therapy and its impact on the success of cancer management.

In Silico Screening Accelerates Nanocarrier Design for Efficient mRNA Delivery

Lipidic nanocarriers are a broad class of lipid-based vectors with proven potential for packaging and delivering emerging nucleic acid therapeutics. An important early step in the clinical development cycle is large-scale screening of diverse formulation libraries to assess particle quality and payload delivery efficiency. Due to the size of the screening space, this process can be both costly and time-consuming. To address this, computational models capable of predicting clinically relevant physio-chemical properties of dendrimer-lipid nanocarriers, along with their mRNA payload delivery efficiency in human cells are developed. The models are then deployed on a large theoretical nanocarrier pool consisting of over 4.5 million formulations. Top predictions are synthesised for validation using cell-based assays, leading to the discovery of a high quality, high performing, candidate. The methods reported here enable rapid, high-throughput, in silico pre-screening for high-quality candidates, and have great potential to reduce the cost and time required to bring mRNA therapies to the clinic.

Stimuli-Responsive Non-viral Nanoparticles for Gene Delivery

Considering nucleic acids as the language of life and the genome as the instruction manual of cells, their targeted modulation promises great opportunities in treating and healing diseases. In addition to viral gene transfer, the overwhelming power of non-viral mRNA-based vaccines is driving the development of novel gene transporters. Thereby, various nucleic acids such as DNA (pDNA) or RNA (mRNA, siRNA, miRNA, gRNA, or ASOs) need to be delivered, requiring a transporter due to their high molar mass and negative charge in contrast to classical agents. This chapter presents the specific biological hurdles for using nucleic acids and shows how new materials can overcome these.

A Fluorophore-Labeled Lysine Dendrimer with an Oxo-Anion-Binding Motif for Tracking Gene Transfection

A transfection vector based on a peptide dendrimer (1) has been developed and its abilities for DNA binding and transport have been investigated. By attaching a fluorophore to the vector system (1*), several steps in the transfection process could be monitored directly. As DLS and AFM studies showed, the labeled vector 1* condensed DNA into tightly packed aggregates able to enter eukaryotic cells. Co-localization experiments revealed that the ligand/plasmid complex is taken up by the endosomal pathway followed by an endosomal escape or lysosomal degradation. Afterwards, the plasmid DNA seems to enter the nucleus due to a breakdown of the nuclear envelope during mitosis, as only cells that have recently undergone mitosis showed H2B-GFP expression.

Exploiting endocytosis for transfection of mRNA for cytoplasmatic delivery using cationic gold nanoparticles

Introduction

Gene therapy holds promise to cure various diseases at the fundamental level. For that, efficient carriers are needed for successful gene delivery. Synthetic 'non-viral' vectors, as cationic polymers, are quickly gaining popularity as efficient vectors for transmitting genes. However, they suffer from high toxicity associated with the permeation and poration of the cell membrane. This toxic aspect can be eliminated by nanoconjugation. Still, results suggest that optimising the oligonucleotide complexation, ultimately determined by the size and charge of the nanovector, is not the only barrier to efficient gene delivery.

Methods

We herein develop a comprehensive nanovector catalogue comprising different sizes of Au NPs functionalized with two different cationic molecules and further loaded with mRNA for its delivery inside the cell.

Results and Discussion

Tested nanovectors showed safe and sustained transfection efficiencies over 7 days, where 50 nm Au NPs displayed the highest transfection rates. Remarkably, protein expression was increased when nanovector transfection was performed combined with chloroquine. Cytotoxicity and risk assessment demonstrated that nanovectors are safe, ascribed to lesser cellular damage due to their internalization and delivery via endocytosis. Obtained results may pave the way to design advanced and efficient gene therapies for safely transferring oligonucleotides.

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.

Complexation of Oligo- and Polynucleotides with Methoxyphenyl-Functionalized Imidazolium Surfactants

Interaction between cationic surfactants and nucleic acids attracts much attention due to the possibility of using such systems for gene delivery. Herein, the lipoplexes based on cationic surfactants with imidazolium head group bearing methoxyphenyl fragment (MPI-n, n = 10, 12, 14, 16) and nucleic acids (oligonucleotide and plasmid DNA) were explored. The complex formation was confirmed by dynamic/electrophoretic light scattering, transmission electron microscopy, fluorescence spectroscopy, circular dichroism, and gel electrophoresis. The nanosized lipoplex formation (of about 100-200 nm), contributed by electrostatic, hydrophobic interactions, and intercalation mechanism, has been shown. Significant effects of the hydrocarbon tail length of surfactant and the type of nucleic acid on their interaction was revealed. The cytotoxic effect and transfection ability of lipoplexes studied were determined using M-HeLa, A549 cancer cell lines, and normal Chang liver cells. A selective reduced cytotoxic effect of the complexes on M-HeLa cancer cells was established, as well as a high ability of the systems to be transfected into cancer cells. MPI-n/DNA complexes showed a pronounced transfection activity equal to the commercial preparation Lipofectamine 3000. Thus, it has been shown that MPI-n surfactants are effective agents for nucleic acid condensation and can be considered as potential non-viral vectors for gene delivery.

G-Quadruplex Linked DNA Guides Selective Transfection into Nucleolin-Overexpressing Cancer Cells

Gene therapy is a promising approach for treating tumors. Conventional approaches of DNA delivery depending on non-viral or viral vectors are unsatisfactory due to the concerns of biosafety and cell-targeting efficiency. The question how to deliver DNA into tumor cells efficiently and selectively is a major technological problem in tumor gene therapy. Here, we develop a vector-free gene transfer strategy to deliver genes effectively and selectively by taking advantage of targeting nucleolin. Nucleolin, a shuttle protein moving between cell membrane, cytoplasm and nuclei, is overexpressed in tumor cells. It has a natural ligand G-quadruplex (Gq). Gq-linked DNA (Gq-DNA) is likely to be internalized by ligand dependent uptake mechanisms independently of vectors after neutralizing negative charges of cell membrane by targeting nucleolin. This strategy is referred to as Gq-DNA transfection. Benefiting from its high affinity to nucleolin, Gq-DNA can be effectively delivered into nucleolin-positive tumor cells even nuclei. Gq-DNA transfection is characterized by low cytotoxicity, high efficiency, ease of synthesis, high stability in serum, direct access into nuclei, and specific nucleolin-positive tumor cell targeting.

Gemini lipid nanoparticle (GLNP)-mediated oral delivery of TNF-α siRNA mitigates gut inflammation via inhibiting the differentiation of CD4+ T cells

Proinflammatory cytokines such as Tumor Necrosis Factor-α (TNF-α) are critical mediators of inflammatory bowel disease pathogenesis, and are important targets to restore intestinal homeostasis. Herein, we present the engineering and screening of gemini lipid nanoparticles (GLNPs) for siRNA delivery to colon epithelial cells, macrophages and dendritic cells, and their ability to deliver siRNA therapeutics to the inflamed gastrointestinal tract. We synthesized eight gemini cationic lipids by tethering two lithocholic acid molecules through 3'-hydroxyl- and 24'-carboxyl-derived ammonium groups using different polyalkylene spacers. Screening of GLNPs, composed of gemini cationic lipid and dioleoylphosphatidylethanolamine lipid, showed that GLNPs derived from gemini lipid G1 are the most effective in the delivery of siRNA across mammalian cell membranes with reduced toxicity. Gemini lipid G1-derived siRNA-GLNP complexes (siGLNPs) can effectively reduce gene expression, and are stable in simulated gastric fluid. The delivery of TNF-α siRNA using siGLNPs can mitigate gut inflammation in a dextran sodium sulfate-induced murine inflammation model. As CD4⁺ T cells, especially Th17 cells, are key mediators of gut inflammation, we further showed that these siGLNPs inhibit infiltration and differentiation of CD4⁺ T cells to Th17 and T_reg cells. Therefore, this study highlights the potential of GLNPs derived from lithocholic acid-derived gemini cationic lipids for the development of next-generation nucleic acid delivery vehicles.

Advances towards Cell‐Specific Gene Transfection: A Small‐Molecule Approach Allows Order‐of‐Magnitude Selectivity

A transfection vector that can home in on tumors is reported. Whereas previous vectors that allow moderately cell selective gene transfection used larger systems, this small‐molecule approach paved the way for precise structure‐activity relationship optimization. For this, biotin, which mediates cell selectivity, was combined with the potent DNA‐binding motif tetralysine‐guanidinocarbonypyrrol via a hydrophilic linker, thus enabling SAR‐based optimization. The new vector mediated biotin receptor (BR)‐selective transfection of cell lines with different BR expression levels. Computer‐based analyses of microscopy images revealed a preference of one order of magnitude for the BR‐positive cell lines over the BR‐negative controls.

A new strategy for stem cells therapy for erectile dysfunction: Adipose-derived stem cells transfect Neuregulin-1 gene through superparamagnetic iron oxide nanoparticles

PURPOSE

Our previous studies showed that nanotechnology improves derived adipose-derived stem cells (ADSCs) therapy for erectile dysfunction (ED). In this study, the Neuregulin-1(NRG1) gene was transfected into ADSCs with superparamagnetic iron oxide nanoparticles (SPION) further to improve the therapeutic effect of ADSCs on ED.

MATERIALS AND METHODS

ADSCs were isolated from epididymal adipose tissue of Sprague-Dawley rats. The optimal concentration of PEI-SPION (SPION modified with polyethyleneimine) was selected to construct the gene complex. After electrostatic binding of PEI-SPION and DNA, a PEI layer was wrapped to make the PEI-SPION-NRG1-PEI gene transfection complex. Different groups were set up for transfection tests. Lipo2000 transfection reagent was used as the control. PEI-SPION-NRG1-PEI in the experimental group was transfected under an external magnetic field.

RESULTS

When the concentration of PEI-SPION was 10 µg/mL, it had little cytotoxicity, and cell activity was not significantly affected. PEI-SPION-NRG1-PEI forms positively charged nanocomposites with a particle size of 72.6±14.9 nm when N/P ≥8. The PEI-SPION-NRG1-PEI gene complex can significantly improve the transfection efficiency of ADSCs, reaching 26.74%±4.62%, under the action of the external magnetic field. PCR and Western blot showed that the expression level of the NRG1 gene increased significantly, which proved that the transfection was effective.

CONCLUSIONS

PEI-SPION can be used as a vector for NRG1 gene transfection into ADSCs. PEI-SPION-NRG1-PEI packaging has the highest transfection efficiency under the external magnetic field than the other groups. These findings may provide a new strategy for ADSCs therapy for ED.

Evaluation of pentaerythritol-based and trimethylolpropane-based cationic lipidic materials for gene delivery

The chemical and physical structure of cationic liposomes pays an important effect on their gene transfection efficiency. Investigation on the structure-function relationship of cationic liposomes will guide the design of novel cationic liposomes with high transfection efficiency and biosafety. In this paper, two novel series of lipids based on the backbone of pentaerythritol and trimethylolpropane were discovered, and their gene transfection efficiencies were assayed in vitro. The four lipids 8c, 9c, 14b, and 15b, exhibited much better transfection efficiency in the HEK293 cell lines compared with Lipo2000, lipid 9c also showed good transfection efficiency in the SW480 cell lines. And the structure-efficiency relationship revealed that a hydroxyethyl polar head group boosted transfer potency in trimethylolpropane-type lipids, but reduced in pentaerythritol-type lipids.

New diagnostic and therapeutic strategies for myocardial infarction via nanomaterials

Myocardial infarction is lethal to patients because of insufficient blood perfusion to vital organs. Several attempts have been made to improve its prognosis, among which nanomaterial research offers an opportunity to address this problem at the molecular level and has the potential to improve disease prevention, diagnosis, and treatment significantly. Up to now, nanomaterial-based technology has played a crucial role in broad novel diagnostic and therapeutic strategies for cardiac repair. This review summarizes various nanomaterial applications in myocardial infarction from multiple aspects, including high precision detection, pro-angiogenesis, regulating immune homeostasis, and miRNA and stem cell delivery vehicles. We also propose promising research hotspots that have not been reported much yet, such as conjugating pro-angiogenetic elements with nanoparticles to construct drug carriers, developing nanodrugs targeting other immune cells except for macrophages in the infarcted myocardium or the remote region. Though most of those strategies are preclinical and lack clinical trials, there is tremendous potential for their further applications in the future.

Surface-Engineered Mucus Penetrating Nucleic Acid Delivery Systems with Cell Penetrating Peptides for the Lungs

Nucleic acids, both DNA and small RNAs, have emerged as potential therapeutics for the treatment of various lung disorders. However, delivery of nucleic acids to the lungs is challenging due to the barrier property imposed by mucus, which is further reinforced in disease conditions such as chronic obstructive pulmonary disease and asthma. The presence of negatively charged mucins imparts the electrostatic barrier property, and the mesh network structure of mucus provides steric hindrance to the delivery system. To overcome this, the delivery system either needs to be muco-inert with a low positive charge such that the interactions with mucus are minimized or should have the ability to transiently dismantle the mucus structure for effective penetration. We have developed a mucus penetrating system for the delivery of both small RNA and plasmid DNA independently. The nucleic acid core consists of a nucleic acid (pDNA/siRNA) and a cationic/amphipathic cell penetrating peptide. The mucus penetrating coating consists of the hydrophilic biopolymer chondroitin sulfate A (CS-A) conjugated with a mucolytic agent, mannitol. We hypothesize that the hydrophilic coating of CS-A would reduce the surface charge and decrease the interaction with negatively charged mucins, while the conjugated mannitol residues would disrupt the mucin-mucin interaction or decrease the viscosity of mucus by increasing the influx of water into the mucus. Our results indicate that CS-A-mannitol-coated nanocomplexes possess reduced surface charge, reduced viscosity of artificial mucus, and increased diffusion in mucin suspension as well as increased penetration through the artificial mucus layer as compared to the non-coated ones. Further, the coated nanocomplexes showed low cytotoxicity as well as higher transfection in A-549 and BEAS-2B cells as compared to the non-coated ones.

Metal-organic frameworks (MOFs) as host materials for the enhanced delivery of biomacromolecular therapeutics

Biomacromolecular drugs have become an important class of therapeutic agents for the treatment of human diseases. Considering their high propensity for being degraded in the human body, the choice of an appropriate delivery system is key to ensure the therapeutic efficacy of biomacromolecular drugs in vivo. As an emerging class of supramolecular "host" materials, metal-organic frameworks (MOFs) exhibit advantages in terms of the tunability of pore size, encapsulation efficiency, controllable drug release, simplicity in surface functionalization and good biocompatibility. As a result, MOF-based host-guest systems have been extensively developed as a new class of flexible and powerful platform for the delivery of therapeutic biomacromolecules. In this review, we summarize current research progress in the synthesis of MOFs as delivery materials for a variety of biomacromolecules. Firstly, we briefly introduce the advances made in the use of biomacromolecular drugs for disease therapy and the types of commonly used clinical delivery systems. We then describe the advantages of using MOFs as delivery materials. Secondly, the strategies for the construction of MOF-encapsulated biomacromolecules (Biomacromolecules@MOFs) and the release mechanisms of the therapeutics are categorized. Thirdly, the application of MOFs to deliver different types of biomacromolecules (e.g., antigens/antibodies, enzymes, therapeutic proteins, DNA/RNA, polypeptides, and polysaccharides) for the treatment of various human diseases based on immunotherapy, gene therapy, starvation therapy and oxidation therapy is summarized. Finally, the remaining challenges and available opportunities for MOFs as drug delivery systems are outlined, which we anticipate will encourage additional research efforts directed towards developing Biomacromolecules@MOFs systems for biomedical applications.

Novel α-tocopherol-ferrocene conjugates for the specific delivery of transgenes in liver cancer cells under high serum conditions

The delivery of therapeutic genes to a specific organ has drawn significant research attention. Among the pool of various delivery vectors, cationic liposomes (non-viral) are potential candidates for delivering therapeutic genes due to their low immunogenic response. Here, we have developed novel ferrocene-conjugated cationic tocopheryl aggregates as non-viral vectors. These formulations can transfer a reporter gene (pGL3; encoded for luciferase protein) specifically to liver cancer cells (HepG2 and Huh7) instead of non-hepatic cancer cells, such as Caco-2 (human colon carcinoma) and HeLa (cervical cancer) cells. The transfection efficiency (TE) of the optimum liposomal formulation is more significant than commercially available Lipofectamine 2000 (L2K). Notably, it retains its TE under high serum conditions (up to 50% FBS). A coupled effect from conjugated ferrocene and tocopherol in the cationic liposomal formulation might be responsible for the cell-specific delivery and higher serum compatibility. Therefore, the present proposed delivery system may provide a platform for further progress in terms of developing hepatotropic gene delivery systems.

A review of the tortuous path of nonviral gene delivery and recent progress

Gene therapy encompasses the transfer of exogenous genetic materials into the patient's target cells to treat or prevent diseases. Nevertheless, the transfer of genetic material into desired cells is challenging and often requires specialized tools or delivery systems. For the past 40 years, scientists are mainly pursuing various viruses as gene delivery vectors, and the overall progress has been slow and far from the expectation. As an alternative, nonviral vectors have gained substantial attention due to their several advantages, including superior safety profile, enhanced payload capacity, and stealth abilities. Since nonviral vectors encounter multiple extra- and intra-cellular barriers limiting the transfer of genetic payload into the target cell nucleus, we have discussed these barriers in detail for this review. A direct approach, utilizing physical methods like electroporation, sonoporation, gene gun, eliminate the requirement for a specific carrier for gene delivery. In contrast, chemical methods of gene transfer exploit natural or synthetic compounds as carriers to increase cellular targeting and gene therapy effectiveness. We have also emphasized the recent advancements aimed at enhancing the current nonviral approaches. Therefore, in this review, we have focused on discussing the current evolving state of nonviral gene delivery systems and their future perspectives.

Nanoparticles-Based Oligonucleotides Delivery in Cancer: Role of Zebrafish as Animal Model

Oligonucleotide (ON) therapeutics are molecular target agents composed of chemically synthesized DNA or RNA molecules capable of inhibiting gene expression or protein function. How ON therapeutics can efficiently reach the inside of target cells remains a problem still to be solved in the majority of potential clinical applications. The chemical structure of ON compounds could affect their capability to pass through the plasma membrane. Other key factors are nuclease degradation in the extracellular space, renal clearance, reticulo-endothelial system, and at the target cell level, the endolysosomal system and the possible export via exocytosis. Several delivery platforms have been proposed to overcome these limits including the use of lipidic, polymeric, and inorganic nanoparticles, or hybrids between them. The possibility of evaluating the efficacy of the proposed therapeutic strategies in useful in vivo models is still a pivotal need, and the employment of zebrafish (ZF) models could expand the range of possibilities. In this review, we briefly describe the main ON therapeutics proposed for anticancer treatment, and the different strategies employed for their delivery to cancer cells. The principal features of ZF models and the pros and cons of their employment in the development of ON-based therapeutic strategies are also discussed.

How Far Are Non-Viral Vectors to Come of Age and Reach Clinical Translation in Gene Therapy?

Efficient delivery of genetic material into cells is a critical process to translate gene therapy into clinical practice. In this sense, the increased knowledge acquired during past years in the molecular biology and nanotechnology fields has contributed to the development of different kinds of non-viral vector systems as a promising alternative to virus-based gene delivery counterparts. Consequently, the development of non-viral vectors has gained attention, and nowadays, gene delivery mediated by these systems is considered as the cornerstone of modern gene therapy due to relevant advantages such as low toxicity, poor immunogenicity and high packing capacity. However, despite these relevant advantages, non-viral vectors have been poorly translated into clinical success. This review addresses some critical issues that need to be considered for clinical practice application of non-viral vectors in mainstream medicine, such as efficiency, biocompatibility, long-lasting effect, route of administration, design of experimental condition or commercialization process. In addition, potential strategies for overcoming main hurdles are also addressed. Overall, this review aims to raise awareness among the scientific community and help researchers gain knowledge in the design of safe and efficient non-viral gene delivery systems for clinical applications to progress in the gene therapy field.

2,2-Bis(hydroxymethyl) propionic acid based cyclic carbonate monomers and their (co)polymers as advanced materials for biomedical applications

Designing grafted biodegradable polymers with tailored multi-functional properties is one of the most researched fields with extensive biomedical applications. Among many biodegradable polymers, polycarbonates have gained much attention due to their ease of synthesis, high drug loading, and excellent biocompatibility profiles. Among various monomers, 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) derived cyclic carbonate monomers have been extensively explored in terms of their synthesis as well as their polymerization. Since the late 90s, significant advancements have been made in the design of bis-MPA derived cyclic carbonate monomers as well as in their reaction schemes. Currently, bis-MPA derived polycarbonates have taken a form of an entire platform with a multitude of applications, the latest being in the field of nanotechnology, targeted drug, and nucleic acid delivery. The present review outlines an up to date developments that have taken place in the last two decades in the design, synthesis, and biomedical applications of bis-MPA derived cyclic carbonates and their (co)polymers.

Mesenchymal Stem Cells Engineered by Nonviral Vectors: A Powerful Tool in Cancer Gene Therapy

Due to their "tumor homing" and "immune privilege" characteristics, the use of mesenchymal stem cells (MSCs) has been proposed as a novel tool against cancer. MSCs are genetically engineered in vitro and then utilized to deliver tumoricidal agents, including prodrugs and bioactive molecules, to tumors. The genetic modification of MSCs can be achieved by various vectors, and in most cases viral vectors are used; however, viruses may be associated with carcinogenesis and immunogenicity, restricting their clinical translational potential. As such, nonviral vectors have emerged as a potential solution to address these limitations and have gradually attracted increasing attention. In this review, we briefly revisit the current knowledge about MSC-based cancer gene therapy. Then, we summarize the advantages and challenges of nonviral vectors for MSC transfection. Finally, we discuss recent advances in the development of new nonviral vectors, which have provided promising strategies to overcome obstacles in the gene modulation of MSCs.

Biological and Medical Applications of Calcium Phosphate Nanoparticles

Calcium phosphate nanoparticles have a high biocompatibility and biodegradability due to their chemical similarity to human hard tissue, for example, bone and teeth. They can be used as efficient carriers for different kinds of biomolecules such as nucleic acids, proteins, peptides, antibodies, or drugs, which alone are not able to enter cells where their biological effect is required. They can be loaded with cargo molecules by incorporating them, unlike solid nanoparticles, and also by surface functionalization. This offers protection, for example, against nucleases, and the possibility for cell targeting. If such nanoparticles are functionalized with fluorescing dyes, they can be applied for imaging in vitro and in vivo. Synthesis, functionalization and cell uptake mechanisms of calcium phosphate nanoparticles are discussed together with applications in transfection, gene silencing, imaging, immunization, and bone substitution. Biodistribution data of calcium phosphate nanoparticles in vivo are reviewed.

Luminescent Amphiphilic Aminoglycoside Probes to Study Transfection

We report the characterization of amphiphilic aminoglycoside conjugates containing luminophores with aggregation-induced emission properties as transfection reagents. These inherently luminescent transfection vectors are capable of binding plasmid DNA through electrostatic interactions; this binding results in an emission "on" signal due to restriction of intramolecular motion of the luminophore core. The luminescent cationic amphiphiles effectively transferred plasmid DNA into mammalian cells (HeLa, HEK 293T), as proven by expression of a red fluorescent protein marker. The morphologies of the aggregates were investigated by microscopy as well as ζ-potential and dynamic light-scattering measurements. The transfection efficiencies using luminescent cationic amphiphiles were similar to that of the gold-standard transfection reagent Lipofectamine® 2000.

Nucleic Acid-Based Therapeutics in Orphan Neurological Disorders: Recent Developments

The possibility of rational design and the resulting faster and more cost-efficient development cycles of nucleic acid–based therapeutics (NBTs), such as antisense oligonucleotides, siRNAs, and gene therapy vectors, have fueled increased activity in developing therapies for orphan diseases. Despite the difficulty of delivering NBTs beyond the blood–brain barrier, neurological diseases are significantly represented among the first targets for NBTs. As orphan disease NBTs are now entering the clinical stage, substantial efforts are required to develop the scientific background and infrastructure for NBT design and mechanistic studies, genetic testing, understanding natural history of orphan disorders, data sharing, NBT manufacturing, and regulatory support. The outcomes of these efforts will also benefit patients with “common” diseases by improving diagnostics, developing the widely applicable NBT technology platforms, and promoting deeper understanding of biological mechanisms that underlie disease pathogenesis. Furthermore, with successes in genetic research, a growing proportion of “common” disease cases can now be attributed to mutations in particular genes, essentially extending the orphan disease field. Together, the developments occurring in orphan diseases are building the foundation for the future of personalized medicine. In this review, we will focus on recent achievements in developing therapies for orphan neurological disorders.

Nonviral Locally Injected Magnetic Vectors for In Vivo Gene Delivery: A Review of Studies on Magnetofection

Magnetic nanoparticles have been widely used in nanobiomedicine for diagnostics and the treatment of diseases, and as carriers for various drugs. The unique magnetic properties of "magnetic" drugs allow their delivery in a targeted tumor or tissue upon application of a magnetic field. The approach of combining magnetic drug targeting and gene delivery is called magnetofection, and it is very promising. This method is simple and efficient for the delivery of genetic material to cells using magnetic nanoparticles controlled by an external magnetic field. However, magnetofection in vivo has been studied insufficiently both for local and systemic routes of magnetic vector injection, and the relevant data available in the literature are often merely descriptive and contradictory. In this review, we collected and systematized the data on the efficiency of the local injections of magnetic nanoparticles that carry genetic information upon application of external magnetic fields. We also investigated the efficiency of magnetofection in vivo, depending on the structure and coverage of magnetic vectors. The perspectives of the development of the method were also considered.

Advances and challenges in adeno-associated viral inner-ear gene therapy for sensorineural hearing loss

There is growing attention and effort focused on treating the root cause of sensorineural hearing loss rather than managing associated secondary characteristic features. With recent substantial advances in understanding sensorineural hearing-loss mechanisms, gene delivery has emerged as a promising strategy for the biological treatment of hearing loss associated with genetic dysfunction. There are several successful and promising proof-of-principle examples of transgene deliveries in animal models; however, there remains substantial further progress to be made in these avenues before realizing their clinical application in humans. Herein, we review different aspects of development, ongoing preclinical studies, and challenges to the clinical transition of transgene delivery of the inner ear toward the restoration of lost auditory and vestibular function.

Lipophilic Peptide Dendrimers for Delivery of Splice-Switching Oligonucleotides

Non-viral transfection reagents are continuously being developed in attempt to replace viral vectors. Among those non-viral vectors, dendrimers have gained increasing interest due to their unique molecular structure and multivalency. However, more improvements are still needed to achieve higher efficacy and lower toxicity. In this study, we have examined 18 peptide dendrimers conjugated to lipophilic moieties, such as fatty acids or hydrophobic amino acids, that were previously explored for siRNA. Reporter cells were employed to investigate the transfection of single strand splice-switching oligonucleotides (ONs) using these peptide dendrimers. Luciferase level changes reflecting efficiency varied with amino acid composition, stereochemistry, and complexation media used. 3rd generation peptide dendrimers with D-amino acid configuration were superior to L-form. Lead formulations with 3rd generation, D-amino acid peptide dendrimers increased the correction level of the delivered ON up to 93-fold over untreated HeLa Luc/705 cells with minimal toxicity. To stabilize the formed complexes, Polyvinyl alcohol 18 (PVA18) polymer was added. Although PVA18 addition increased activity, toxicity when using our best candidates G 2,3KL-(Leu)₄ (D) and G 2,3KL-diPalmitamide (D) was observed. Our findings demonstrate the potential of lipid-conjugated, D-amino acid-containing peptide dendrimers to be utilized as an effective and safe delivery vector for splice-switching ONs.

Peptides as a material platform for gene delivery: Emerging concepts and converging technologies

Successful gene therapies rely on methods that safely introduce DNA into target cells and enable subsequent expression of proteins. To that end, peptides are an attractive materials platform for DNA delivery, facilitating condensation into nanoparticles, delivery into cells, and subcellular release to enable protein expression. Peptides are programmable materials that can be designed to address biocompatibility, stability, and subcellular barriers that limit efficiency of non-viral gene delivery systems. This review focuses on fundamental structure-function relationships regarding peptide design and their impact on nanoparticle physical properties, biologic activity, and biocompatibility. Recent peptide technologies utilize multi-dimensional structures, non-natural chemistries, and combinations of peptides with lipids to achieve desired properties and efficient transfection. Advances in DNA cargo design are also presented to highlight further opportunities for peptide-based gene delivery. Modern DNA designs enable prolonged expression compared to traditional plasmids, providing an additional component that can be synergized with peptide carriers for improved transfection. Peptide transfection systems are poised to become a flexible and efficient platform incorporating new chemistries, functionalities, and improved DNA cargos to usher in a new era of gene therapy.

Transient Destabilization of Biological Membranes Contributes to the Superior Performance of Star-Shaped PDMAEMA in Delivering pDNA

Nonviral DNA vectors are promising alternatives to viral ones. Their use in DNA medicine is limited by an inability to transfect, for example, nondividing or suspension cells. In recent years, star-shaped synthetic polycationic vectors, so called "Nanostars", have shown some promise in this regard, at least when compared to the "gold standard" in nonviral vectors, namely, linear poly(ethyleneimine) (l-PEI). It has been hypothesized that an ability to transiently destabilize cellular membranes is partially responsible for the phenomenon. This hypothesis is investigated here, taking human leukemia suspension cells (Jurkat cells) as an example. Contrary to l-PEI, the Nanostars promote the cellular uptake of small, normally membrane-impermeant molecules (trypan blue and propidium iodide) as well as that of fluorescent polystyrene beads (average diameter 100 nm). Since Nanostars, but not l-PEI, are apparently able to deliver DNA to nuclei of nondividing cells, nuclear uptake is, in addition, investigated with isolated cell nuclei. Our results provide evidence that Nanostars are more efficient than l-PEI in increasing the nuclear membrane association/permeability, allowing accumulation of their cargo on/in the nucleus.

Inhaled RNA Therapy: From Promise to Reality

RNA-based medicine is receiving growing attention for its diverse roles and potential therapeutic capacity. The largest obstacle in its clinical translation remains identifying a safe and effective delivery system. Studies investigating RNA therapeutics in pulmonary diseases have rapidly expanded and drug administration by inhalation allows the direct delivery of RNA therapeutics to the target site of action while minimizing systemic exposure. In this review, we highlight recent developments in pulmonary RNA delivery systems with the use of nonviral vectors. We also discuss the major knowledge gaps that require thorough investigation and provide insights that will help advance this exciting field towards the bedside.

Naphthalene diimide bis-guanidinio-carbonyl-pyrrole as a pH-switchable threading DNA intercalator

A novel naphthalene diimde analogue (NDI) equipped at the imide positions with two guanidinio-carbonyl-pyrrole (GCP) pendant arms interacted significantly stronger with ds-DNA at pH 5 than at pH 7, due to reversible protonation of the GCP arms. This was consequence of a pH-switchable threading intercalation into ds-DNAs only at pH 5, while at neutral conditions (pH 7) NDI-GCP₂ switched to the DNA minor groove binding. Intriguingly, NDI-GCP₂ was at both pH values studied bound to the ds-RNA major groove, still showing a higher affinity and thermal denaturation effect at pH 5 due to GCP protonation. At excess over the DNA/RNA conjugate NDI-GCP₂ showed also aggregation along the ds-polynucleotide and AFM and DLS demonstrated that NDI-GCP₂ has pronounced ds-DNA condensation ability.

Cyclopropenium Nanoparticles and Gene Transfection in Cells

Non-viral vectors for the transfection of genetic material are at the frontier of medical science. In this article, we introduce for the first time, cyclopropenium-containing nanoparticles as a cationic carrier for gene transfection, as an alternative to the common quaternary ammonium transfection agents. Cyclopropenium-based cationic nanoparticles were prepared by crosslinking poly(ethylene imine) (PEI) with tetrachlorocyclopropene. These nanoparticles were electrostatically complexed with plasmid DNA into nanoparticles (~50 nm). Their cellular uptake into F929 mouse fibroblast cells, and their eventual expression in vitro have been described. Transfection is enhanced relative to PEI with minimal toxicity. These cyclopropenium nanoparticles possess efficient gene transfection capabilities with minimal cytotoxicity, which makes them novel and promising candidates for gene therapy.

Gene Therapy in Cancer Treatment: Why Go Nano?

The proposal of gene therapy to tackle cancer development has been instrumental for the development of novel approaches and strategies to fight this disease, but the efficacy of the proposed strategies has still fallen short of delivering the full potential of gene therapy in the clinic. Despite the plethora of gene modulation approaches, e.g., gene silencing, antisense therapy, RNA interference, gene and genome editing, finding a way to efficiently deliver these effectors to the desired cell and tissue has been a challenge. Nanomedicine has put forward several innovative platforms to overcome this obstacle. Most of these platforms rely on the application of nanoscale structures, with particular focus on nanoparticles. Herein, we review the current trends on the use of nanoparticles designed for cancer gene therapy, including inorganic, organic, or biological (e.g., exosomes) variants, in clinical development and their progress towards clinical applications.

Non-Viral in Vitro Gene Delivery: It is Now Time to Set the Bar!

Transfection by means of non-viral gene delivery vectors is the cornerstone of modern gene delivery. Despite the resources poured into the development of ever more effective transfectants, improvement is still slow and limited. Of note, the performance of any gene delivery vector in vitro is strictly dependent on several experimental conditions specific to each laboratory. The lack of standard tests has thus largely contributed to the flood of inconsistent data underpinning the reproducibility crisis. A way researchers seek to address this issue is by gauging the effectiveness of newly synthesized gene delivery vectors with respect to benchmarks of seemingly well-known behavior. However, the performance of such reference molecules is also affected by the testing conditions. This survey points to non-standardized transfection settings and limited information on variables deemed relevant in this context as the major cause of such misalignments. This review provides a catalog of conditions optimized for the gold standard and internal reference, 25 kDa polyethyleneimine, that can be profitably replicated across studies for the sake of comparison. Overall, we wish to pave the way for the implementation of standardized protocols in order to make the evaluation of the effectiveness of transfectants as unbiased as possible.

The effect of polar headgroups and spacer length on the DNA transfection of cholesterol-based cationic lipids

This article is related to the effects of the headgroups and spacer length of cationic lipids on transfection efficiency. To develop highly potent cationic lipids, a series of divalent lysine-diamine conjugated cholesterol-based cationic lipids with three different headgroups (ammonium, trimethyl ammonium, and guanidinium) were synthesized. The newly synthesized cationic lipids (1-6)A formed cationic liposomes in the presence and absence of a zwitterionic helper lipid, DOPE (dioleoylphosphatidylethanolamine). A gel retardation assay showed that most of the prepared lipoplexes could retard DNA migration in the presence of DOPE. We attempted to modify the diverse cationic headgroups to improve the transfection efficiency. However, the lysine-1,3-diaminopropane-conjugated cholesterol-based lipid 4A, having divalent ammonium of unmodified lysine headgroup, exhibited high relative transfection efficiency in HEK293. When the transfection efficiency of 4A was formulated with DOPE (1 : 1 weight ratio), it produced the same range in comparison with that of a commercially available transfection agent, Lipofectamine™ 2000 (L2k). The lipid 4A was studied to optimize the conditions with respect to the lipid/DOPE and DNA/lipid ratios and the amount of DNA. The transfection efficiency of the highly potent lipid 4A was also studied to determine the transfection efficiency of HeLa, PC3, and HC-04 cell lines. This lipid also protected the DNA from a serum and had low toxicity. Lipoplexes 4A with DOPE had the particle size of around 300-600 nm and the zeta potential of around 0-45 mV. In summary, cationic liposomes 4A demonstrated a high performance as DNA carriers.