Fast therapeutic DNA internalization – A high potential transfection system based on a peptide mimicking cationic lipid

Development and functionality analysis of lipoplex-loaded polysaccharide-based surface coatings for local nucleic acid delivery

Although therapeutic nucleic acids reached the clinical application for a decade, the success of these new drugs is dependent on their delivery strategies, which are still a challenge. In particular, local delivery of nucleic acids is a promising approach to develop therapies with a spatially controlled site of action. However, compared to techniques for systemic administration, local nucleic acid delivery systems are still rarely described. In this study, we present a promising approach to fill this gap by the design of surface coatings based on polysaccharides for local delivery of nucleic acids. An automatized Layer-by-Layer deposition approach was applied using hyaluronic acid and chitosan to form polyelectrolyte multilayer systems, into which lipid nanoparticles, more specific lipoplexes, were embedded as nucleic acid carriers. Different manufacturing parameters, in particular the number of deposited polyelectrolyte layers and the preparation buffer, were varied. The multilayer film characteristics were investigated systematically regarding their physical properties, with a focus on thickness and topology as well as lipoplex deposition, to identify a system with efficient transfection properties. The multilayer systems prepared in acetate buffer were characterized by a good lipoplex embedding with a more uniform distribution and lower tendency for formation of large lipoplex aggregates in the polyelectrolyte film. Additionally, we were able to demonstrate the functionality of the developed system for nucleic acid delivery. The nucleic acids were successfully transferred into cells in a contact-triggered manner. Furthermore, we could demonstrate the enzymatic degradation-based release of nucleic acid cargo from the delivery system caused by hyaluronidase, followed by successful in vitro transfection.

Investigating 3R In Vivo Approaches for Bio-Distribution and Efficacy Evaluation of Nucleic Acid Nanocarriers: Studies on Peptide-Mimicking Ionizable Lipid

Formulations based on ionizable amino-lipids have been put into focus as nucleic acid delivery systems. Recently, the in vitro efficacy of the lipid formulation OH4:DOPE has been explored. However, in vitro performance of nanomedicines cannot correctly predict in vivo efficacy, thereby considerably limiting pre-clinical translation. This is further exacerbated by limited access to mammalian models. The present work proposes to close this gap by investigating in vivo nucleic acid delivery within simpler models, but which still offers physiologically complex environments and also adheres to the 3R guidelines (replace/reduce/refine) to improve animal experiments. The efficacy of OH4:DOPE as a delivery system for nucleic acids is demonstrated using in vivo approaches. It is shown that the formulation is able to transfect complex tissues using the chicken chorioallantoic membrane model. The efficacy of DNA and mRNA lipoplexes is tested extensively in the zebra fish (Danio rerio) embryo which allows the screening of biodistribution and transfection efficiency. Effective transfection of blood vessel endothelial cells is seen, especially in the endocardium. Both model systems allow an efficacy screening according to the 3R guidelines bypassing the in vitro-in vivo gap. Pilot studies in mice are performed to correlate the efficacy of in vivo transfection.

Efficient Transfection of Large Plasmids Encoding HIV-1 into Human Cells-A High Potential Transfection System Based on a Peptide Mimicking Cationic Lipid

One major disadvantage of nucleic acid delivery systems is the low transfection or transduction efficiency of large-sized plasmids into cells. In this communication, we demonstrate the efficient transfection of a 15.5 kb green fluorescent protein (GFP)-fused HIV-1 molecular clone with a nucleic acid delivery system prepared from the highly potent peptide-mimicking cationic lipid OH4 in a mixture with the phospholipid DOPE (co-lipid). For the transfection, liposomes were loaded using a large-sized plasmid (15.5 kb), which encodes a replication-competent HIV type 1 molecular clone that carries a Gag-internal green fluorescent protein (HIV-1 JR-FL Gag-iGFP). The particle size and charge of the generated nanocarriers with 15.5 kb were compared to those of a standardized 4.7 kb plasmid formulation. Stable, small-sized lipoplexes could be generated independently of the length of the used DNA. The transfer of fluorescently labeled pDNA-HIV1-Gag-iGFP in HEK293T cells was monitored using confocal laser scanning microscopy (cLSM). After efficient plasmid delivery, virus particles were detectable as budding structures on the plasma membrane. Moreover, we observed a randomized distribution of fluorescently labeled lipids over the plasma membrane. Obviously, a significant exchange of lipids between the drug delivery system and the cellular membranes occurs, which hints toward a fusion process. The mechanism of membrane fusion for the internalization of lipid-based drug delivery systems into cells is still a frequently discussed topic.

Peptide- and Drug-Functionalized Fluorescent Quantum Dots for Enhanced Cell Internalization and Bacterial Debilitation

This report illustrates a strategy for designing a nanoconjugate derived vector that efficiently delivers antimicrobial drug directly into bacterial cells. The nanoconjugate comprises of negatively charged CDTe@CdS quantum dots (QDs) with its surface functionalized using cationic BP-100 (KKLFKKILKYL-amide), a known cell-penetrating peptide (CPP), via electrostatic approach. The interactions between QD and CPP in QD-functionalized CPPs (QD-CPP) have been well analyzed using fluorescence spectroscopy, gel electrophoresis, and ζ-potential analysis. The QD-CPP conjugate was internalized into Gram negative (Escherichia coli) as well as Gram positive (Staphylococcus aureus) bacterial strains with confocal studies exhibiting a strong signal in tested microorganisms. Further, to check the applicability of QD-CPP conjugate as a delivery vector for generating an effective therapeutics, ampicillin molecules were conjugated on QD-CPP surface to generate QD-CPP-Amp conjugate. The CPP and drug molecules on the surface of QDs were well quantified using high-performance liquid chromatography (HPLC) data. It was observed that the internalization and bacterial debilitation of the QD-CPP-Amp conjugate is 2- to 4-fold effective as compared to that of bare ampicillin. The morphological changes to the bacterial cells upon the treatment with QD-CPP-Amp conjugates were noted with no cytotoxic effect on tested mammalian cell lines. The results inferred that the proposed QD-CPP vector provides a targeted and proficient approach for cellular internalization of cargo (drug) in bacterial cells with effective tracking through florescent QDs.

Contact-Triggered Lipofection from Multilayer Films Designed as Surfaces for in Situ Transfection Strategies in Tissue Engineering

Biomaterials, which release active compounds after implantation, are an essential tool for targeted regenerative medicine. In this study, thin multilayer films loaded with lipid/DNA complexes (lipoplexes) were designed as surface coatings for in situ transfection applicable in tissue engineering and regenerative medicine. The film production and embedding of lipoplexes were based on the layer-by-layer (LbL) deposition technique. Hyaluronic acid (HA) and chitosan (CHI) were used as the polyelectrolyte components. The embedded plasmid DNA was complexed using a new designed cationic lipid formulation, namely, OH4/DOPE 1/1, the advantageous characteristics of which have been proven already. Three different methods were tested regarding its efficiency of lipid and DNA deposition. Therefore, several surface specific analytics were used to characterize the LbL formation, the lipid DNA embedding, and the surface characteristics of the multilayer films, such as fluorescence microscopy, surface plasmon resonance spectroscopy, ellipsometry, zeta potential measurements, atomic force microscopy, and scanning electron microscopy. Interaction studies were conducted for optimized lipoplex-loaded polyelectrolyte multilayers (PEMs) that showed an efficient attachment of C2C12 cells on the surface. Furthermore, no acute toxic effects were found in cell culture studies, demonstrating biocompatibility. Cell culture experiments with C2C12 cells, a cell line which is hard to transfect, demonstrated efficient transfection of the reporter gene encoding for green fluorescent protein. In vivo experiments using the chicken embryo chorion allantois membrane animal replacement model showed efficient gene-transferring rates in living complex tissues, although the DNA-loaded films were stored over 6 days under wet and dried conditions. Based on these findings, it can be concluded that OH4/DOPE 1/1 lipoplex-loaded PEMs composed of HA and CHI can be an efficient tool for in situ transfection in regenerative medicine.

A triple chain polycationic peptide-mimicking amphiphile - efficient DNA-transfer without co-lipids

Non-viral gene delivery in its current form is largely dependent upon the ability of a delivery vehicle to protect its cargo in the extracellular environment and release it efficiently inside the target cell. Also a simple delivery system is required to simplify a GMP conform production if a marketing authorization is striven for. This work addresses these problems. We have developed a synthetic polycationic peptide-mimicking amphiphile, namely DiTT4, which shows efficient transfection rates and good biocompatibility without the use of a co-lipid in the formulation. The lipid-nucleic acid complex (lipoplex) was characterized at the structural (electron microscopy), physical (laser Doppler velocimetry and atomic force microscopy) and molecular levels (X-ray scattering). Stability studies of the lipoplexes in the presence of serum and heparin indicated a stable formation capable of protecting the cargo against the extracellular milieu. Hemocompatibility studies (hemolysis, complement activation and erythrocyte aggregation) demonstrated the biocompatibility of the formulation for systemic administration. The transfection efficiency was assessed in vitro using the GFP assay and confocal laser scanning microscopy studies. With the chorioallantoic membrane model, an animal replacement model according to the 3R strategy (replacement, refinement, and reduction), initial in vivo experiments were performed which demonstrate fast and efficient transfection in complex tissues and excellent biocompatibility.

Gene editing of MPS I human fibroblasts by co-delivery of a CRISPR/Cas9 plasmid and a donor oligonucleotide using nanoemulsions as nonviral carriers

Mucopolysaccharidosis type I (MPS I) is an inherited disease caused by the deficiency of alpha-L-iduronidase (IDUA). This study shows the use of nanoemulsions co-complexed with the plasmid of CRISPR/Cas9 system and a donor oligonucleotide aiming at MPS I gene editing in vitro. Nanoemulsions composed of MCT, DOPE, DOTAP, DSPE-PEG, and water were prepared by high-pressure homogenization. The DNA was complexed by adsorption (NA) or encapsulation (NE) of preformed DNA/DOTAP complexes with nanoemulsions at +4/-1 charge ratio. The incubation in pure DMEM or supplemented with serum showed that the complexation with DNA was stable after 1 h of incubation, but the complexes tended to release the adsorbed DNA after 24 h of incubation, while the encapsulated DNA remained complexed in the oil core of the nanoemulsions even 48 h after incubation with DMEM. The treatment of MPS I patient's fibroblasts homozygous for the p.Trp402^∗ mutation led to a significant increase in IDUA activity at 2, 15, and 30 days when compared to MPS I untreated fibroblasts. Flow cytometry and confocal microscopy demonstrated that there was a reduction in the area of lysosomes to values similar to normal, an indicator of correction of the cellular phenotype. These results show that the nanoemulsions co-complexed with the CRISPR/Cas9 system and a donor oligonucleotide could effectively transfect MPS I p.Trp402^∗ patient's fibroblasts, as well as enable the production of IDUA, and represent a potential new treatment option for MPS I.

Malonic acid based cationic lipids - The way to highly efficient DNA-carriers

Cationic lipids play an important role as non-viral nucleic acid carriers in gene therapy since 3 decades. This review will introduce malonic acid derived cationic lipids as nucleic acid carriers which appeared in the literature dealing with lipofection 10years ago. The family of amino-functionalized branched fatty acid amides will be presented as well as different generations of malonic acid diamides. Both groups of cationic lipids yield lipid mixtures with highly efficient nucleic acid transfer activities in in-vitro cell culture models. The DNA transfer screening of lipid libraries with directed structural variations in the lipophilic as well as in the hydrophilic part of the amphiphiles yields structure/activity relationships. Furthermore, the detailed characterizations of selected lipid composites at the air/water interface and in bulk systems are summarized with regard to transfection determining physical-chemical properties. The findings are also discussed in comparison to results obtained with other families of cationic lipids.