Poly(l-glutamic acid) augments the transfection performance of lipophilic polycations by overcoming tradeoffs among cytotoxicity, pDNA delivery efficiency, and serum stability

Polycations are scalable and affordable nanocarriers for delivering therapeutic nucleic acids. Yet, cationicity-dependent tradeoffs between nucleic acid delivery efficiency, cytotoxicity, and serum stability hinder clinical translation. Typically, the most efficient polycationic vehicles also tend to be the most toxic. For lipophilic polycations-which recruit hydrophobic interactions in addition to electrostatic interactions to bind and deliver nucleic acids-extensive chemical or architectural modifications sometimes fail to resolve intractable toxicity-efficiency tradeoffs. Here, we employ a facile post-synthetic polyplex surface modification strategy wherein poly(l-glutamic acid) (PGA) rescues toxicity, inhibits hemolysis, and prevents serum inhibition of lipophilic polycation-mediated plasmid (pDNA) delivery. Importantly, the sequence in which polycations, pDNA, and PGA are combined dictates pDNA conformations and spatial distribution. Circular dichroism spectroscopy reveals that PGA must be added last to polyplexes assembled from lipophilic polycations and pDNA; else, PGA will disrupt polycation-mediated pDNA condensation. Although PGA did not mitigate toxicity caused by hydrophilic PEI-based polycations, PGA tripled the population of transfected viable cells for lipophilic polycations. Non-specific adsorption of serum proteins abrogated pDNA delivery mediated by lipophilic polycations; however, PGA-coated polyplexes proved more serum-tolerant than uncoated polyplexes. Despite lower cellular uptake than uncoated polyplexes, PGA-coated polyplexes were imported into nuclei at higher rates. PGA also silenced the hemolytic activity of lipophilic polycations. Our work provides fundamental insights into how polyanionic coatings such as PGA transform intermolecular interactions between lipophilic polycations, nucleic acids, and serum proteins, and facilitate gentle yet efficient transgene delivery.

Cinchona Alkaloid Polymers Demonstrate Highly Efficient Gene Delivery Dependent on Stereochemistry, Methoxy Substitution, and Length

Nucleic acid delivery with cationic polymers is a promising alternative to expensive viral-based methods; however, it often suffers from a lower performance. Herein, we present a highly efficient delivery system based on cinchona alkaloid natural products copolymerized with 2-hydroxyethyl acrylate. Cinchona alkaloids are an attractive monomer class for gene delivery applications, given their ability to bind to DNA via both electrostatics and intercalation. To uncover the structure-activity profile of the system, four structurally similar cinchona alkaloids were incorporated into polymers: quinine, quinidine, cinchonine, and cinchonidine. These polymers differed in the chain length, the presence or absence of a pendant methoxy group, and stereochemistry, all of which were found to alter gene delivery performance and the ways in which the polymers overcome biological barriers to transfection. Longer polymers that contained the methoxy-bearing cinchona alkaloids (i.e., quinine and quinidine) were found to have the best performance. These polymers exhibited the tightest DNA binding, largest and most abundant DNA-polymer complexes, and best endosomal escape thanks to their increased buffering capacity and closest nuclear proximity of the payload. Overall, this work highlights the remarkable efficiency of polymer systems that incorporate cinchona alkaloid natural products while demonstrating the profound impact that small structural changes can have on overcoming biological hurdles associated with gene delivery.

A comprehensive review on novel targeted therapy methods and nanotechnology-based gene delivery systems in melanoma

Melanoma, a malignant form of skin cancer, has been swiftly increasing in recent years. Although there have been significant advancements in clinical treatment underlying a well-understanding of melanoma-susceptible genes and the molecular basis of melanoma pathogenesis, the permanency of response to therapy is frequently constrained by the emergence of acquired resistance and systemic toxicity. Conventional therapies, including surgical resection, chemotherapy, radiotherapy, and immunotherapy, have already been used to treat melanoma and are dependent on the cancer stage. Nevertheless, ineffective side effects and the heterogeneity of tumors pose major obstacles to the therapeutic treatment of malignant melanoma through such strategies. In light of this, advanced therapies including nucleic acid therapies (ncRNA, aptamers), suicide gene therapies, and gene therapy using tumor suppressor genes, have lately gained immense attention in the field of cancer treatment. Furthermore, nanomedicine and targeted therapy based on gene editing tools have been applied to the treatment of melanoma as potential cancer treatment approaches nowadays. Indeed, nanovectors enable delivery of the therapeutic agents into the tumor sites by passive or active targeting, improving therapeutic efficiency and minimizing adverse effects. Accordingly, in this review, we summarized the recent findings related to novel targeted therapy methods as well as nanotechnology-based gene systems in melanoma. We also discussed current issues along with potential directions for future research, paving the way for the next-generation of melanoma treatments.

A new microfluidic platform for the highly reproducible preparation of non-viral gene delivery complexes

Transfection describes the delivery of exogenous nucleic acids (NAs) to cells utilizing non-viral means. In the last few decades, scientists have been doing their utmost to design ever more effective transfection reagents. These are eventually mixed with NAs to give rise to gene delivery complexes, which must undergo characterization, testing, and further refinement through the sequential reiteration of these steps. Unfortunately, although microfluidics offers distinct advantages over the canonical approaches to preparing particles, the systems available do not address the most frequent and practical quest for the simultaneous generation of multiple polymer-to-NA ratios (N/Ps). Herein, we developed a user-friendly microfluidic cartridge to repeatably prepare non-viral gene delivery particles and screen across a range of seven N/Ps at once or significant volumes of polyplexes at a given N/P. The microchip is equipped with a chaotic serial dilution generator for the automatic linear dilution of the polymer to the downstream area, which encompasses the NA divider to dispense equal amounts of DNA to the mixing area, enabling the formation of particles at seven N/Ps eventually collected in individual built-in tanks. This is the first example of a stand-alone microfluidic cartridge for the fast and repeatable preparation of non-viral gene delivery complexes at different N/Ps and their storage.

Designing Synthetic Polymers for Nucleic Acid Complexation and Delivery: From Polyplexes to Micelleplexes to Triggered Degradation

Gene delivery as a therapeutic tool continues to advance toward impacting human health, with several gene therapy products receiving FDA approval over the past 5 years. Despite this important progress, the safety and efficacy of gene therapy methodology requires further improvement to ensure that nucleic acid therapeutics reach the desired targets while minimizing adverse effects. Synthetic polymers offer several enticing features as nucleic acid delivery vectors due to their versatile functionalities and architectures and the ability of synthetic chemists to rapidly build large libraries of polymeric candidates equipped for DNA/RNA complexation and transport. Current synthetic designs are pursuing challenging objectives that seek to improve transfection efficiency and, at the same time, mitigate cytotoxicity. This Perspective will describe recent work in polymer-based gene complexation and delivery vectors in which cationic polyelectrolytes are modified synthetically by introduction of additional components─including hydrophobic, hydrophilic, and fluorinated units─as well as embedding of degradable linkages within the macromolecular structure. As will be seen, recent advances employing these emerging design strategies are promising with respect to their excellent biocompatibility and transfection capability, suggesting continued promise of synthetic polymer gene delivery vectors going forward.

Vibropolyfection: coupling polymer-mediated gene delivery to mechanical stimulation to enhance transfection of adherent cells

Background

With the success of recent non-viral gene delivery-based COVID-19 vaccines, nanovectors have gained some public acceptance and come to the forefront of advanced therapies. Unfortunately, the relatively low ability of the vectors to overcome cellular barriers adversely affects their effectiveness. Scientists have thus been striving to develop ever more effective gene delivery vectors, but the results are still far from satisfactory. Therefore, developing novel strategies is probably the only way forward to bring about genuine change. Herein, we devise a brand-new gene delivery strategy to boost dramatically the transfection efficiency of two gold standard nucleic acid (NA)/polymer nanoparticles (polyplexes) in vitro.

Results

We conceived a device to generate milli-to-nanoscale vibrational cues as a function of the frequency set, and deliver vertical uniaxial displacements to adherent cells in culture. A short-lived high-frequency vibrational load (t = 5 min, f = 1,000 Hz) caused abrupt and extensive plasmalemma outgrowths but was safe for cells as neither cell proliferation rate nor viability was affected. Cells took about 1 hr to revert to quasi-naïve morphology through plasma membrane remodeling. In turn, this eventually triggered the mechano-activated clathrin-mediated endocytic pathway and made cells more apt to internalize polyplexes, resulting in transfection efficiencies increased from 10-to-100-fold. Noteworthy, these results were obtained transfecting three cell lines and hard-to-transfect primary cells.

Conclusions

In this work, we focus on a new technology to enhance the intracellular delivery of NAs and improve the transfection efficiency of non-viral vectors through priming adherent cells with a short vibrational stimulation. This study paves the way for capitalizing on physical cell stimulation(s) to significantly raise the effectiveness of gene delivery vectors in vitro and ex vivo.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01571-x.

The Potential of CRISPR-Guided Therapies in the Dermatology Clinic

Over the past decade, CRISPR has rapidly made its way from the bench to the bedside, providing a newfound therapeutic avenue to not only treat genetic diseases but also permanently cure them. Although there are several clinical trials in early stages, there are so far no CRISPR-based clinical trials for cutaneous disease. In this review, we describe multiple cutaneous diseases that represent ideal targets for CRISPR-based therapeutics owing to known single gene‒causing mutations. We also explore the potential of CRISPR nucleases to treat inflammatory disorders such as eczema and psoriasis, which are not classically categorized as genodermatoses. We describe the therapeutic solutions for these diseases that are guided by various CRISPR-associated (Cas) effector proteins, for example, using Cas9 to permanently edit the DNA of somatic cells, Cas3 to target foreign DNA to combat viral/bacterial skin infections, and Cas13 to edit mutated RNA transcripts in diseases where permanent DNA editing is untenable. Furthermore, we discuss various drug delivery modalities for CRISPR therapeutics, including transdermal patches and microneedles, which are uniquely suited for dermatological diseases. In summary, we highlight the potential of CRISPR-based therapeutics to revolutionize the treatment of cutaneous disease with a goal of being accessible to the practicing dermatologist.

Modified Gold Nanoparticles to Overcome the Chemoresistance to Gemcitabine in Mutant p53 Cancer Cells

Mutant p53 proteins result from missense mutations in the TP53 gene, the most mutated in human cancer, and have been described to contribute to cancer initiation and progression. Therapeutic strategies for targeting mutant p53 proteins in cancer cells are limited and have proved unsuitable for clinical application due to problems related to drug delivery and toxicity to healthy tissues. Therefore, the discovery of efficient and safe therapeutic strategies that specifically target mutant p53 remains challenging. In this study, we generated gold nanoparticles (AuNPs) chemically modified with low molecular branched polyethylenimine (bPEI) for the efficient delivery of gapmers targeting p53 mutant protein. The AuNPs formulation consists of a combination of polymeric mixed layer of polyethylene glycol (PEG) and PEI, and layer-by-layer assembly of bPEI through a sensitive linker. These nanoparticles can bind oligonucleotides through electrostatic interactions and release them in the presence of a reducing agent as glutathione. The nanostructures generated here provide a non-toxic and powerful system for the delivery of gapmers in cancer cells, which significantly downregulated mutant p53 proteins and altered molecular markers related to cell growth and apoptosis, thus overcoming chemoresistance to gemcitabine.

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.

In silico prediction of the in vitro behavior of polymeric gene delivery vectors

Non-viral gene delivery vectors have increasingly come under the spotlight, but their performaces are still far from being satisfactory. Therefore, there is an urgent need for forecasting tools and screening methods to enable the development of ever more effective transfectants. Here, coarse-grained (CG) models of gold standard transfectant poly(ethylene imine)s (PEIs) have been profitably used to investigate and highlight the effect of experimentally-relevant parameters, namely molecular weight (2 vs. 10 kDa) and topologies (linear vs. branched), protonation state, and ammine-to-phosphate ratios (N/Ps), on the complexation and the gene silencing efficiency of siRNA molecules. The results from the in vitro screening of cationic polymers and conditions were used to validate the in silico platform that we developed, such that the hits which came out of the CG models were of high practical relevance. We show that our in silico platform enables to foresee the most suitable conditions for the complexation of relevant siRNA-polycation assemblies, thereby providing a reliable predictive tool to test bench transfectants in silico, and foster the design and development of gene delivery vectors.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Multifunctional Neomycin-Triazine-Based Cationic Lipids for Gene Delivery with Antibacterial Properties

Cationic lipids (CLs) have gained significant attention among nonviral gene delivery vectors due to their ease of synthesis and functionalization with multivalent moieties. In particular, there is an increasing request for multifunctional CLs having gene delivery capacity and antibacterial activity. Herein, we describe the design and synthesis of a novel class of aminoglycoside (AG)-based multifunctional vectors with high transfection efficiency and noticeable antibacterial properties. Specifically, cationic amphiphiles were built on a triazine scaffold, allowing for an easy derivatization with up to three potentially different substituents, such as neomycin (Neo) that serves as the polar head and one or two lipophilic tails, namely stearyl (ST) and oleyl (OL) alkyl chains and cholesteryl (Chol) tail. With the aim to shed more light on the effect of different types and numbers of lipophilic moieties on the ability of CLs to condense and transfect cells, the performance of Neo–triazine-based derivatives as gene delivery vectors was evaluated and compared. The ability of Neo–triazine-based derivatives to act as antimicrobial agents was evaluated as well. Neo–triazine-based CLs invariably exhibited excellent DNA condensation ability, even at a low charge ratio (CR, +/−). Besides, each derivative showed very good transfection performance at its optimal CR on two different cell lines, along with negligible cytotoxicity. CLs bearing symmetric two-tailed OL proved to be the most effective in transfection. Interestingly, Neo–triazine-based derivatives, used as either free lipids or lipoplexes, exhibited strong antibacterial activity against Gram-negative bacteria, especially in the case of CLs bearing one or two aliphatic chains. Altogether, these results highlight the potential of Neo–triazine-based derivatives as effective multifunctional nonviral gene delivery vectors.

Synthesis and Application of Cellulose-Polyethyleneimine Composites and Nanocomposites: A Concise Review

Cellulose/polyethyleneimine composites have increasingly attracted the attention of scientific community, devoted to the design and development of new synthetic strategies and materials for different application fields. In this review, after introducing the main characteristics of the two polymeric components, we provide in the second section a critical overview on the main protocols for the synthesis of these composites, considering both the several cellulose sources and forms, and the different cross-linkers and cross-linking procedures developed for this purpose, outlining advantages and limits for the reported approaches. The last section analyses the principal results obtained in different application fields. A wide discussion is dedicated to the principal use of cellulose/polyethyleneimine composites as sorbents for water remediation from heavy metal ions and organic contaminants. Subsequently, we introduce the literature describing the use of these composites, functionalized appropriately, where necessary, as drug delivery systems, sensors, and heterogeneous catalysts for organic reactions. Finally, after a brief description of other random applications, we furnish a personal analysis of actual limits and potentialities for these systems.

Tyrosine-Modification of Polypropylenimine (PPI) and Polyethylenimine (PEI) Strongly Improves Efficacy of siRNA-Mediated Gene Knockdown

The delivery of small interfering RNAs (siRNA) is an efficient method for gene silencing through the induction of RNA interference (RNAi). It critically relies, however, on efficient vehicles for siRNA formulation, for transfection in vitro as well as for their potential use in vivo. While polyethylenimines (PEIs) are among the most studied cationic polymers for nucleic acid delivery including small RNA molecules, polypropylenimines (PPIs) have been explored to a lesser extent. Previous studies have shown the benefit of the modification of small PEIs by tyrosine grafting which are featured in this paper. Additionally, we have now extended this approach towards PPIs, presenting tyrosine-modified PPIs (named PPI-Y) for the first time. In this study, we describe the marked improvement of PPI upon its tyrosine modification, leading to enhanced siRNA complexation, complex stability, siRNA delivery, knockdown efficacy and biocompatibility. Results of PPI-Y/siRNA complexes are also compared with data based on tyrosine-modified linear or branched PEIs (LPxY or PxY). Taken together, this establishes tyrosine-modified PPIs or PEIs as particularly promising polymeric systems for siRNA formulation and delivery.

Gene Delivery to the Skin - How Far Have We Come?

Gene therapies are powerful tools to prevent, treat, and cure human diseases. The application of gene therapies for skin diseases received little attention so far, despite the easy accessibility of skin and the urgent medical need. A major obstacle is the unique barrier properties of human skin, which significantly limits the absorption of biomacromolecules, and thus hampers the efficient delivery of nucleic acid payloads. In this review, we discuss current approaches, successes, and failures of cutaneous gene therapy and provide guidance toward the development of next-generation concepts. We specifically allude to the delivery strategies as the major obstacle that prevents the full potential of gene therapies – not only for skin disorders but also for almost any other human disease.

Gene therapies are powerful tools for the treatment of inflammatory, genetic, and cancer-related skin diseases.

The skin barrier function and the low number of cells that get transfected are the main hurdles for cutaneous gene therapy and contribute to the fact that gene therapies for skin diseases are an underexplored area.

Gene editing provides an approach to cure rare and severe genodermatoses-like epidermolysis bullosa. First studies demonstrate the potential and invaluable impact these treatments may have even if only a small percentage of the gene function can be restored.

Recent advancements demonstrate the power of non-viral delivery systems for the delivery of gene therapeutics to the skin. They may prove superior to viral vectors, the current gold standard, because their use is not limited by packaging size, serious safety concerns, or manufacturing issues.

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.

Silencing of GFP expression in human mesenchymal stem cells using quaternary polyplexes of siRNA-PEI with glycosaminoglycans and albumin

In recent years evidence has been mounting for a role for mesenchymal stem cells (MSCs) in immunomodulation, anti-inflammatory processes, and paracrine signaling via secreted extracellular vesicles. In order to exploit these biological functions, systems to efficiently deliver genetic material into MSCs would therefore be highly desirable. In this study, efficient silencing of GFP expression by combining high N/P ratio siRNA and branched PEI (bPEI) polyplexes (siRNA-bPEI) polyplexes with glycosaminoglycans (GAGs), namely hyaluronic acid (HA), chondroitin sulfate (CS) and heparin sulfate (HS), and human serum albumin (HSA) is reported. These quaternary systems were characterized using surface charge, size and morphology and applied to MSCs, which represent a challenge due to their typically low transfection efficiency. The quaternary polyplexes promoted efficient charge shielding and release of siRNA in the cytoplasm with reduced toxicity. A high silencing efficiency of >90% (i.e., less than 10% remaining GFP expression) was achieved with noticeably reduced cellular toxicity, especially with siRNA-bPEI polyplexes modified with HA and HA + HSA. In general addition of GAGs led to more compact polyplexes. Endocytosis studies point to improved endosomal escape at high N/P ratios as a reason for high transfection efficiency and a role for hyaluronic acid in the uptake mechanism likely via CD44 interactions. Co-localization studies showed the polyplexes are stable in the cytosol over time, which correlates with a proper disassembly and subsequent silencing of GFP. Furthermore, GAG containing polyplexes were frequently co-localized with the nucleus. These findings in sum suggest that PEI/HSA/GAG based quaternary polyplexes are promising as transfection agents for MSCs. STATEMENT OF SIGNIFICANCE: Since mesenchymal stem cells (MSCs) are recruited to the site of tissue repair and play a role in immunomodulation, anti-inflammatory processes, and paracrine signaling, they present an excellent target for genetic engineering. However, delivery of genetic material into MSCs is challenging. In this study, >97% silencing of constitutive green fluorescent protein expression in human MSCs (hMSCs) using high N/P ratio polyplexes of branched-PEI-siRNA incorporating glycosaminoglycan as a charge neutralizer and human serum albumin as co-complexing agent is demonstrated. In addition to possessing good cytocompatibility and excellent cytosolic stability; polyplexes incorporating GAGs also showed altered endocytic uptake, with incorporation of hyaluronic acid promoting caveolae-mediated entry. Our system highlights the importance of physiologically derived macromolecules in delivery of genetic material into hMSCs.

Lipid-Based DNA Therapeutics: Hallmarks of Non-Viral Gene Delivery

Gene therapy is a promising strategy for the treatment of monogenic disorders. Non-viral gene delivery systems including lipid-based DNA therapeutics offer the opportunity to deliver an encoding gene sequence specifically to the target tissue and thus enable the expression of therapeutic proteins in diseased cells. Currently, available gene delivery approaches based on DNA are inefficient and require improvements to achieve clinical utility. In this Review, we discuss state-of-the-art lipid-based DNA delivery systems that have been investigated in a preclinical setting. We emphasize factors influencing the delivery and subsequent gene expression in vitro, ex vivo, and in vivo. In addition, we cover aspects of nanoparticle engineering and optimization for DNA therapeutics. Finally, we highlight achievements of lipid-based DNA therapies in clinical trials.

Hierarchical microchannel architecture in chitosan/bioactive glass scaffolds via electrophoretic deposition positive-replica

One of the main challenges in the design of scaffolds for cortical bone regeneration is mimicking the highly oriented, hierarchical structure of the native tissue in an efficient, simple, and consistent way. As a possible solution to this challenge, positive replica based on electrophoretic deposition (EPD) was here evaluated as a technique to produce organic/inorganic scaffolds with oriented micro-porosities mimicking Haversian canals diameter and spacing. Two different sizes of 45S5 bioactive glass (BG) powders were chosen as inclusions and loaded in a chitosan matrix via EPD on micro-patterned cathodes. Self-standing chitosan scaffolds, with a homogeneous dispersion of BG particles and regularly-oriented micro-channels (ϕ = 380 ± 50 μm, inter-channel spacing = 600 ± 40 μm), were obtained. In vitro analysis in simulated body fluid (SBF) revealed the ability to induce a deposition of a homogenous layer of hydroxyapatite (HA), with Ca/P nucleation reactions appearing kinetically favored by smaller BG particles. Cell interaction with hybrid scaffolds was evaluated in vitro with bone osteosarcoma cells (SAOS-2). The osteoconductive potential of EPD structures was assessed by evaluating cells proliferation, viability and scaffold colonization. Results indicate that EPD is a simple yet extremely effective technique to prepare composite micro-patterned structures and can represent a platform for the development of a new generation of bone scaffolds. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

Cationic Polypeptoids with Optimized Molecular Characteristics toward Efficient Nonviral Gene Delivery

The rational design of gene vectors relies on the understanding of their structure-property relationship. Polypeptoids, which are structural isomers of natural polypeptides, hold great potential as gene delivery vectors due to their facile preparation, structural tunability, and most importantly, their desirable proteolytic stability. We herein designed a library of polypeptoids with different cationic side-chain terminal groups, degree of polymerizations (DPs), side-chain lengths, and incorporated aliphatic side chains, to unravel the structure-property relationships so that gene delivery efficiency can be maximized and cytotoxicity can be minimized. In HeLa cells, a polypeptoid bearing a primary amine side-chain terminal group exhibited remarkably higher transfection efficiency than that of its analogues containing secondary, tertiary, or quaternary amine groups. Elongation of the polypeptoid backbone length (from 28 to 251 mer) led to enhanced DNA condensation as well as cellular uptake levels, however it also caused higher cytotoxicity. Upon a proper balance between DNA uptake and cytotoxicity, the polypeptoid with a DP of 46 afforded the highest transfection efficiency. Elongating the aliphatic spacer between the backbone and side amine groups enhanced the hydrophobicity of the side chains, which resulted in notably increased membrane activities and transfection efficiency. Further incorporation of hydrophobic decyl side chains led to an improvement in transfection efficiency of ∼6 fold. The top-performing material identified, P11, mediated successful gene transfection under serum-containing conditions, outperforming the commercial transfection reagent poly(ethylenimine) by nearly 4 orders of magnitude. Reflecting its excellent serum-resistant properties, P11 further enabled effective transfection in vivo following intratumoral injection to melanoma-bearing mice. This study will help the rational design of polypeptoid-based gene delivery materials, and the best-performing material identified may provide a potential supplement to existing gene vectors.

Size matters for in vitro gene delivery: investigating the relationships among complexation protocol, transfection medium, size and sedimentation

Although branched and linear polyethylenimines (bPEIs and lPEIs) are gold standard transfectants, a systematic analysis of the effects of the preparation protocol of polyplexes and the composition of the transfection medium on their physicochemical behaviour and effectiveness in vitro have been much neglected, undermining in some way the identification of precise structure-function relationships. This work aimed to address these issues. bPEI/DNA and lPEI/DNA, prepared using two different modes of addition of reagents, gave rise to polyplexes with exactly the same chemical composition but differing in dimensions. Upon dilution in serum-free medium, the size of any kind of polyplex promptly rose over time while remained invariably stable in complete DMEM. Of note, the bigger the dimension of polyplexes (in the nano- to micrometer range), the greater their efficiency in vitro. Besides, centrifugal sedimentation of polyplexes displaying different dimensions to speed up and enhance their settling onto cells boosted transfection efficiencies. Conversely, transgene expression was significantly blunted in cells held upside-down and transfected, definitively pointing out the impact of gravitational sedimentation of polyplexes on their transfection efficiency. Overall, much more attention must be paid to the actual polyplex size that relies on the complexation conditions and the transfection medium.

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.

Characterization and Investigation of Redox-Sensitive Liposomes for Gene Delivery

A number of smart nonviral gene delivery vectors relying on bioresponsiveness have been introduced in the past few years to overcome the limits of the first generation of gene carriers. Among them, redox-sensitive lipidic and polymeric vectors exploit the presence of disulfide bonds in their structure to take advantage of the highly reductive intracellular milieu and to promote complex unpacking and nucleic acids release after cellular uptake (disulfide linker strategy). Glutathione (GSH) has been often identified as the leading actor in the intracellular reduction of bioreducible vectors but their actual mechanisms of action have been rarely investigated in depth and doubts about the real effectiveness of the disulfide linker strategy have been raised. Herein, we outline a simple protocol for the preparation and investigation of nano-sized reducible cationic liposomes, focusing on their thorough characterization and optimization as gene delivery vectors. In addition, we carefully describe the techniques and procedures necessary for the assessment of the bioreducibility of the vectors and to demonstrate that the GSH-mediated intracellular cleavage of disulfide bonds is a pivotal step in their transfection process. Liposomes composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE), and of the reducible cationic lipid SS14 are reported as a practical example but the proposed protocol can be easily shifted to other formulations of reducible lipids/liposomes and to reducible polymers.