bims-novged Biomed News
on Non-viral vectors for gene delivery
Issue of 2023–10–08
thirteen papers selected by
the Merkel lab, Ludwig-Maximilians University



  1. Biointerphases. 2023 Sep 01. pii: 051001. [Epub ahead of print]18(5):
      Nucleic acid-based therapies hold promise for treating previously intractable diseases but require effective delivery vectors to protect the therapeutic agents and ensure efficient transfection. Cationic polymeric vectors are particularly notable for their adaptability, high transfection efficiency, and low cost, but their positive charge often attracts blood proteins, causing aggregation and reduced transfection efficiency. Addressing this, we designed an anionic peptide-grafted dextran (Dex-LipE5H) to serve as a cross-linkable coating to bolster the stability of cationic polymer/nucleic acid complexes. The Dex-LipE5H was synthesized through a Michael addition reaction, combining an anionic peptide (LipE5H) with dextran modified by divinyl sulfone. We demonstrated Dex-lipE5H utility in a novel ternary nucleic acid delivery system, CDex-LipE5H/PEI/nucleic acid. CDex-LipE5H/PEI/nucleic acid demonstrated lower cytotoxicity and superior anti-protein absorption ability compared to PEI/pDNA and Dex-LipE5H/PEI/pDNA. Most notably, the crosslinked CDex-LipE5H/PEI/pDNA demonstrated remarkable transfection performance in HepG2 cells, which poses significant transfection challenges, even in a medium with 20% serum. This system's effective siRNA interference performance was further validated through a PCSK9 gene knockdown assay. This investigation provides novel insights and contributes to the design of cost-effective, next-generation nucleic acid delivery systems with enhanced blood stability and transfection efficiency.
    DOI:  https://doi.org/10.1116/6.0003084
  2. Sci Rep. 2023 Oct 05. 13(1): 16744
      Lipid nanoparticles (LNPs) have been used as a carrier for messenger RNA (mRNA) vaccines. Surface properties of LNPs are important to the stability and function of mRNA vaccines. Polyethylene-glycol (PEG) is a functional lipid at the surface of LNPs that improves colloidal stability, increases circulation time, and impacts cellular uptake. In this study, we explore in-depth lipid composition at the surface of mRNA-LNPs using high-field nuclear magnetic resonance (NMR) spectroscopy. Our results provide a unique surface lipid profile of intact LNPs identifying PEG chains and partial ionizable lipids are present with quantification capability. The surface PEG density is determined to reveal the brush-like conformation on the surface of mRNA-LNPs. Furthermore, we implement a diffusion NMR strategy for routine testing of formulated drug products during drug development. Comparative NMR analysis of different vaccine preparations and stability samples provides a global view of the mRNA-LNP surface structure for enhanced product knowledge.
    DOI:  https://doi.org/10.1038/s41598-023-43898-x
  3. Biomacromolecules. 2023 Oct 04.
      RNA delivery has been demonstrated to be a potent method of vaccine delivery, as demonstrated by the recent success of the COVID-19 vaccines. Polymers have been shown to be effective vehicles for RNA delivery, with poly(ethylene imine) (PEI) being the current gold standard for delivery. Nonetheless, PEI has toxicity concerns, and so finding alternatives is desirable. Poly(2-oxazoline)s are a promising alternative to PEI, as they are generally biocompatible and offer a high degree of control over the polymer structure. Here, we have synthesized an ionizable primary amine 2-oxazoline and combined it with a double bond containing oxazoline to synthesize a small library of charged statistical and block copolymers. The pendant double bonds were reacted further to decorate the polymers with glucose via a thiol-ene click reaction. All polymers were shown to have excellent cell viability, and the synthesized block polymers showed promising complexation efficiencies for the saRNA, demonstrating a clear structure-property relationship. The polymer transfection potential was tested in various cell lines, and a polymer composition with an amine/glucose ratio of 9:27 has demonstrated the best transfection potential across all cell lines tested. Overall, the results suggest that block polymers with a cationic segment and high levels of glycosylation have the best complexation efficiency and RNA expression levels.
    DOI:  https://doi.org/10.1021/acs.biomac.3c00683
  4. Small. 2023 Oct 04. e2306116
      The COVID-19 mRNA vaccines represent a milestone in developing non-viral gene carriers, and their success highlights the crucial need for continued research in this field to address further challenges. Polymer-based delivery systems are particularly promising due to their versatile chemical structure and convenient adaptability, but struggle with the toxicity-efficiency dilemma. Introducing anionic, hydrophilic, or "stealth" functionalities represents a promising approach to overcome this dilemma in gene delivery. Here, two sets of diblock terpolymers are created comprising hydrophobic poly(n-butyl acrylate) (PnBA), a copolymer segment made of hydrophilic 4-acryloylmorpholine (NAM), and either the cationic 3-guanidinopropyl acrylamide (GPAm) or the 2-carboxyethyl acrylamide (CEAm), which is negatively charged at neutral conditions. These oppositely charged sets of diblocks are co-assembled in different ratios to form mixed micelles. Since this experimental design enables countless mixing possibilities, a machine learning approach is applied to identify an optimal GPAm/CEAm ratio for achieving high transfection efficiency and cell viability with little resource expenses. After two runs, an optimal ratio to overcome the toxicity-efficiency dilemma is identified. The results highlight the remarkable potential of integrating machine learning into polymer chemistry to effectively tackle the enormous number of conceivable combinations for identifying novel and powerful gene transporters.
    Keywords:  block copolymers; design of experiment; gene delivery; guanidinium; machine learning; micelles
    DOI:  https://doi.org/10.1002/smll.202306116
  5. Biol Pharm Bull. 2023 ;46(10): 1468-1478
      Most retinal diseases involve the degeneration of choroidal retinal pigment epithelial (RPE) cells. Because of a blood-retina barrier (tight junction formation), RPE cells restrict the entry of hydrophilic macromolecules (e.g., small interfering RNA (siRNA)) through blood stream and eye drops. A cytoplasm-responsive stearylated (STR) peptide, STR-CH2R4H2C (CH2R4) enables stable siRNA complexation, cell permeation, and intracellular dynamics control. We previously demonstrated how CH2R4-modified liposomes promoted siRNA efficacy. We investigated the influence of amino acid sequences of functional peptides on cellular uptake pathways, siRNA transfection efficacy, and the permeation of peptide-modified liposomes in rat RPE-J cells. Four STR-peptides, consisting of arginine (R), cysteine (C), histidine (H), lysine (K) or serine (S), were designed based on CH2R4. We prepared siRNA-loaded, peptide-modified cationic liposomes (CH2R4-, CH2K4-, CH2S4-, SH2R4-, and SH2S4-lipoplexes). CH2R4-, CH2K4-, and SH2R4-lipoplexes induced cellular uptake by macropinocytosis by activating cytoskeletal F-actin, possibly due to cationic amino acids (arginine, lysine). SH2R4-lipoplexes were trapped in endosomes, whereas CH2R4- and CH2K4-lipoplexes enhanced endosomal siRNA release suggesting cysteine contributes to endosomal escape. Although cationic liposome-based, CH2S4- and SH2S4-lipoplexes (not including arginine and lysine) showed lower siRNA transfection efficiency. This difference may be because siRNAs were retained on both peptide moieties and cationic liposomes in CH2R4-, CH2K4- and SH2R4-lipoplexes, whereas in CH2S4- and SH2S4-lipoplexes, siRNAs were loaded to the cationic liposomes, but not on peptides. In three-dimensional spheroids, CH2R4- and CH2K4-modified liposomes promoted permeation through tight junctions. Thus, cationic amino acids and cysteine within peptide sequences of CH2R4 could be effective for siRNA delivery to the retina using functional peptide-modified liposomes.
    Keywords:  endosomal escape; functional peptide; liposome; macropinocytosis; retina; retinal pigment epithelial cell
    DOI:  https://doi.org/10.1248/bpb.b23-00081
  6. Int J Pharm. 2023 Oct 02. pii: S0378-5173(23)00895-5. [Epub ahead of print]646 123474
       AIM: The current study aimed to develop enzyme-activated charge-reversal lipid nanoparticles (LNPs) as novel gene delivery systems.
    METHODS: Palmitic acid was covalently bound to protamine being utilised as transfection promoter to anchor it on the surfaces of LNPs. Green fluorescent protein (GFP) encoding plasmid DNA (pDNA) was ion paired with various cationic counter ions to achieve high encapsulation in LNPs. Protamine-decorated LNPs were prepared by solvent injection method followed by coating with sodium tripolyphosphate (TPP) to generate a bio-inert anionic outer surface. Resulting LNPs were characterised regarding size, polydispersity, zeta potential and encapsulation efficiency. Enzyme-triggered charge-reversal of LNPs was investigated using isolated alkaline phosphatase (ALP) monitoring changes in zeta potential as well as monophosphate release. Furthermore, monophosphate release, cell viability and transfection efficiency were evaluated on a human alveolar epithelial (A549) cell line.
    RESULTS: Protamine-decorated and TPP-coated (Prot-pDNA/DcChol-TPP) LNPs displayed a mean size of 298.8 ± 17.4 nm and a zeta potential of -13.70 ± 0.61 mV. High pDNA encapsulation was achieved with hydrophobic ion pairs of pDNA with 3ß-[N-(N',N'-dimethylaminoethane)-carbamoyl]cholesterol hydrochloride (DcChol). Zeta potential of Prot-pDNA/DcChol-TPP LNPs reversed to positive values with a total Δ26.8 mV shift upon incubation with ALP. Conformably, a notable amount of monophosphate was released upon incubation of Prot-pDNA/DcChol-TPP LNPs with isolated as well as cell-associated ALP. A549 cells well tolerated LNPs displaying more than 95 % viability. Compared with naked pDNA, unmodified LNPs and control LNPs, Prot-pDNA/DcChol-TPP LNPs showed a significantly increased transfection efficiency.
    CONCLUSION: Prot-pDNA/DcChol-TPP LNPs can be regarded as promising gene delivery systems.
    Keywords:  Charge-reversal; Gene delivery; Lipid nanoparticles; Polyphosphate coating; Protamine; Transfection
    DOI:  https://doi.org/10.1016/j.ijpharm.2023.123474
  7. Biomaterials. 2023 Sep 27. pii: S0142-9612(23)00349-6. [Epub ahead of print]302 122341
      Glioblastoma multiforme (GBM) is the most common and lethal primary brain cancer. Current pharmacological interventions marginally increase the 12-month overall survival of patients with GBM. Among the novel therapeutic strategies being pursued, micro-RNAs, a class of non-coding RNAs, are receiving considerable attention for their regulation of several pathways implicated in tumorigenesis and survival. Notably, microRNA-181a-5p (miR-181a) has consistently been reported to be downregulated in GBM clinical samples, and its overexpression negatively affects tumor growth both in vitro and in vivo. To improve the delivery of miR-181a to GBM cells, we sought to develop a modified lipid-based nanocarrier capable of encapsulating and delivering miR-181a to GBM cells in vitro and in vivo. Optimized ionizable-lipid containing lipid nanoparticles (LNP) were constructed by covering the miR-181a-loaded LNP with alternating layers of miR-181a, poly-l-arginine and hyaluronic acid through the layer-by-layer technique. The resulting hyaluronan-decorated lipid nanoparticles (HA-LNP) targeted GBM cells more efficiently than non-modified LNP and mediated siRNA and miRNA transfection in vitro. Finally, delivery of miR-181a by HA-LNP induced significant cellular death of U87 GBM cells in vitro and delayed tumor growth in an in vivo subcutaneous tumor model.
    Keywords:  Glioblastoma multiforme; Layer-by-layer; Lipid nanoparticles; microRNA-181a-5p
    DOI:  https://doi.org/10.1016/j.biomaterials.2023.122341
  8. Adv Sci (Weinh). 2023 Oct 05. e2303706
      Skin is the first barrier against external threats, and skin immune dysfunction leads to multiple diseases. Psoriasis is an inflammatory, chronic, common, immune-related skin disease that affects more than 125 million people worldwide. RNA interference (RNAi) therapy is superior to traditional therapies, but rapid degradation and poor cell uptake are the greatest obstacles to its clinical transformation. The transdermal delivery of siRNA and controllable assembly/disassembly of nanodrug delivery systems can maximize the therapeutic effect. Tetrahedral framework nucleic acid (tFNA) is undoubtedly the best carrier for the transdermal transport of genes due to its excellent noninvasive transdermal effect and editability. The authors combine acid-responsive tannic acid (TA), RNase H-responsive sequences, siRNA, and tFNA into a novel transdermal RNAi drug with controllable assembly and disassembly: STT. STT has heightened resistance to enzyme, serum, and lysosomal degradation, and its size is similar to that of tFNA, enabling easy transdermal transport. After transdermal administration, STT can specifically silence nuclear factor kappa-B (NF-κB) p65, thereby maintaining the stability of the skin's microenvironment and reshaping normal skin immune defense. This work demonstrates the advantages of STT in RNAi therapy and the potential for future treatment of skin-related diseases.
    Keywords:  DNA nanotechnology; lysosomal escape; psoriasis; siRNA delivery; tetrahedral frame nucleic acid
    DOI:  https://doi.org/10.1002/advs.202303706
  9. J Extracell Vesicles. 2023 Oct;12(10): e12371
      Small-interfering RNA (siRNA) therapy is considered a powerful therapeutic strategy for treating cardiac hypertrophy, an important risk factor for subsequent cardiac morbidity and mortality. However, the lack of safe and efficient in vivo delivery of siRNAs is a major challenge for broadening its clinical applications. Small extracellular vesicles (sEVs) are a promising delivery system for siRNAs but have limited cell/tissue-specific targeting ability. In this study, a new generation of heart-targeting sEVs (CEVs) has been developed by conjugating cardiac-targeting peptide (CTP) to human peripheral blood-derived sEVs (PB-EVs), using a simple, rapid and scalable method based on bio-orthogonal copper-free click chemistry. The experimental results show that CEVs have typical sEVs properties and excellent heart-targeting ability. Furthermore, to treat cardiac hypertrophy, CEVs are loaded with NADPH Oxidase 4 (NOX4) siRNA (siNOX4). Consequently, CEVs@siNOX4 treatment enhances the in vitro anti-hypertrophic effects by CEVs with siRNA protection and heart-targeting ability. In addition, the intravenous injection of CEVs@siNOX4 into angiotensin II (Ang II)-treated mice significantly improves cardiac function and reduces fibrosis and cardiomyocyte cross-sectional area, with limited side effects. In conclusion, the utilization of CEVs represents an efficient strategy for heart-targeted delivery of therapeutic siRNAs and holds great promise for the treatment of cardiac hypertrophy.
    Keywords:  NADPH oxidase 4; cardiac hypertrophy; cardiac-targeting peptide; small extracellular vesicles; small-interfering RNA
    DOI:  https://doi.org/10.1002/jev2.12371
  10. J Control Release. 2023 Oct 02. pii: S0168-3659(23)00651-X. [Epub ahead of print]
      Tremendous efforts have been made to improve polymeric property in gene delivery performances, especially when obstacle of transferring gene construct into difficult-to-transfect cells occurs. Innovations in the area of fluorination and fluorinated compounds with biomedical potential in medicinal chemistry are believed to assist in the development of new therapeutics. Fluorine modified polymers have shown to navigate the gene transfection cellular barriers and promoted the transfection outcomes. Gene transfer into some liver cancer cells and human leukemia cells has always been a challenge. Here, by facile incorporation of a fluorine containing amine monomer, 1H,1H-undecafluorohexylamine, fluorinated poly(β-amino ester) (FPAE) was synthesized to significantly improve the transfection performance, achieving high transfection efficiency of 87% and 55% in two representative difficult-to-transfect cells, HepG2 and Molt-4, which were cultured in adhesive and suspension condition, respectively. However, the potency of Lipofectamine 3000 was very limited. More importantly, functional studies revealed that FPAE can dramatically outperform Lipofectamine 3000 in delivering Bcl-xL and PKCβII to either provide the protection against apoptosis or promote the ferroptosis in HepG2 cells. This work facilitates gene therapies by overcoming biological barriers for targeting difficult-to-transfect cells and disease models when medically necessary.
    Keywords:  Apoptosis; Difficult-to-transfect cells; Ferroptosis; Fluorination; HepG2; Molt-4; Poly(β-amino ester)s
    DOI:  https://doi.org/10.1016/j.jconrel.2023.10.001
  11. Eur J Med Chem. 2023 Sep 16. pii: S0223-5234(23)00789-4. [Epub ahead of print]261 115822
      In order to overcome the current LNP-mRNA delivery system's weakness of poor stability and rapid degradation by nuclease, a novel chol-CGYKK molecule and then the new phospholipid liposome were designed and prepared. A solid phase approach synthesized CGYKK and connected it to cholesterol via a disulfide linker to form the desired chol-CGYKK. Four formulated samples with different proportions of excipients were prepared by freeze-drying cationic liposomes and packaged S-mRNA. The stability test shows that after six months at 4 °C, the encapsulation rate of this novel phospholipid liposome was still approximately 90%, which would significantly improve the storage and transportation requirement. Transmission electron microscopy, atomic force microscopy, and scanning electron microscopy indicated that the liposomes were spherical and uniformly dispersed. On comparing the levels of mRNA protein expression of the four formulated samples, the S protein vaccine expression of formulated sample 1 was the highest. Uptake by vector cells for formulated sample 1 showed that compared to Lipo2000, and the transfection efficiency was 66.7%. Furthermore, the safety evaluation of the CGYKK and mRNA vaccine liposomes revealed no toxic effects. The in vivo study demonstrated that this novel mRNA vaccine had an immune response. However, it was still not as good as the LNP group right now, but its excellent physicochemical properties, stability, in vitro biological activity, and in vivo efficacy against SARS-CoV-2 provided new strategies for developing the next generation of mRNA delivery system.
    Keywords:  Cationic liposome; Chol-CGYKK; SARS-CoV-2; Synthesis; mRNA vaccine
    DOI:  https://doi.org/10.1016/j.ejmech.2023.115822
  12. Chem Sci. 2023 Oct 04. 14(38): 10403-10410
      We have developed cell-penetrating stapled peptides based on the amphipathic antimicrobial peptide magainin 2 for intracellular delivery of nucleic acids such as pDNA, mRNA, and siRNA. Various types of stapled peptides with a cross-linked structure were synthesised in the hydrophobic region of the amphipathic structure, and their efficacy in intracellular delivery of pDNA was evaluated. The results showed that the stapled peptide st7-5 could deliver pDNA into cells. To improve the deliverability of st7-5, we further designed st7-5_R, in which the Lys residues were replaced by Arg residues. The peptide st7-5_R formed compact and stable complexes with pDNA and was able to efficiently transfer pDNA into the cell. In addition to pDNA, st7-5_R was also able to deliver mRNA and siRNA into the cell. Thus, st7-5_R is a novel peptide that can achieve efficient intracellular delivery of three different nucleic acids.
    DOI:  https://doi.org/10.1039/d3sc04124g
  13. Macromolecules. 2023 Sep 26. 56(18): 7286-7299
      Cationic polymers are widely used materials in diverse biotechnologies. Subtle variations in these polymers' properties can change them from exceptional delivery agents to toxic inflammatory hazards. Conventional screening strategies optimize for function in a specific application rather than observing how underlying polymer-cell interactions emerge from polymers' properties. An alternative approach is to map basic underlying responses, such as immunogenicity or toxicity, as a function of basic physicochemical parameters to inform the design of materials for a breadth of applications. To demonstrate the potential of this approach, we synthesized 107 polymers varied in charge, hydrophobicity, and molecular weight. We then screened this library for cytotoxic behavior and immunogenic responses to map how these physicochemical properties inform polymer-cell interactions. We identify three compositional regions of interest and use confocal microscopy to uncover the mechanisms behind the observed responses. Finally, immunogenic activity is confirmed in vivo. Highly cationic polymers disrupted the cellular plasma membrane to induce a toxic phenotype, while high molecular weight, hydrophobic polymers were uptaken by active transport to induce NLRP3 inflammasome activation, an immunogenic phenotype. Tertiary amine- and triethylene glycol-containing polymers did not invoke immunogenic or toxic responses. The framework described herein allows for the systematic characterization of new cationic materials with different physicochemical properties for applications ranging from drug and gene delivery to antimicrobial coatings and tissue scaffolds.
    DOI:  https://doi.org/10.1021/acs.macromol.3c01223