Biodegradable Gene Carriers Containing Rigid Aromatic Linkage with Enhanced DNA Binding and Cell Uptake

Tuning the Potency of Farnesol-Modified Polyethylenimine with Polyanionic Trans-Booster to Enhance DNA Delivery

Low molecular weight polyethylenimine (PEI) based lipopolymers become an attractive strategy to construct nonviral therapeutic carriers with promising transfection efficiency and minimal toxicity. Herein, this paper presents the design and synthesis of novel farnesol (Far) conjugated PEI, namely PEI1.2k-SA-Far7. The polymers had quick DNA complexation, effective DNA unpacking (dissociation), and cellular uptake abilities when complexed with plasmid DNA. However, they were unable to provide robust transfection in culture, indicating inability of Far grafting to improve the transfection efficacy significantly. To overcome this limitation, the commercially available polyanionic Trans-Booster additive, which is capable of displaying electrostatic interaction with PEI1.2k-SA-Far7, has been used to enhance the uptake of pDNA polyplexes and transgene expression. pDNA condensation was successfully achieved in the presence of the Trans-Booster with more stable polyplexes, and in vitro transfection efficacy of the polyplexes was improved to be comparable to that obtained with an established reference reagent. The PEI1.2k-SA-Far7/pDNA/Trans-Booster ternary complex exhibited good compatibility with cells and minimal hemolysis activity. This work demonstrates the exemplary potency of using additives in polyplexes and the potential of resultant ternary complexes for effective pDNA delivery.

Recent advances in nanotechnology approaches for non-viral gene therapy

Gene therapy has shown great potential in the treatment of many diseases by downregulating the expression of certain genes. The development of gene vectors as a vehicle for gene therapy has greatly facilitated the widespread clinical application of nucleic acid materials (DNA, mRNA, siRNA, and miRNA). Currently, both viral and non-viral vectors are used as delivery systems of nucleic acid materials for gene therapy. However, viral vector-based gene therapy has several limitations, including immunogenicity and carcinogenesis caused by the exogenous viral vectors. To address these issues, non-viral nanocarrier-based gene therapy has been explored for superior performance with enhanced gene stability, high treatment efficiency, improved tumor-targeting, and better biocompatibility. In this review, we discuss various non-viral vector-mediated gene therapy approaches using multifunctional biodegradable or non-biodegradable nanocarriers, including polymer-based nanoparticles, lipid-based nanoparticles, carbon nanotubes, gold nanoparticles (AuNPs), quantum dots (QDs), silica nanoparticles, metal-based nanoparticles and two-dimensional nanocarriers. Various strategies to construct non-viral nanocarriers based on their delivery efficiency of targeted genes will be introduced. Subsequently, we discuss the cellular uptake pathways of non-viral nanocarriers. In addition, multifunctional gene therapy based on non-viral nanocarriers is summarized, in which the gene therapy can be combined with other treatments, such as photothermal therapy (PTT), photodynamic therapy (PDT), immunotherapy and chemotherapy. We also provide a comprehensive discussion of the biological toxicity and safety of non-viral vector-based gene therapy. Finally, the present limitations and challenges of non-viral nanocarriers for gene therapy in future clinical research are discussed, to promote wider clinical applications of non-viral vector-based gene therapy.

Application of Non-Viral Vectors in Drug Delivery and Gene Therapy

Vectors and carriers play an indispensable role in gene therapy and drug delivery. Non-viral vectors are widely developed and applied in clinical practice due to their low immunogenicity, good biocompatibility, easy synthesis and modification, and low cost of production. This review summarized a variety of non-viral vectors and carriers including polymers, liposomes, gold nanoparticles, mesoporous silica nanoparticles and carbon nanotubes from the aspects of physicochemical characteristics, synthesis methods, functional modifications, and research applications. Notably, non-viral vectors can enhance the absorption of cargos, prolong the circulation time, improve therapeutic effects, and provide targeted delivery. Additional studies focused on recent innovation of novel synthesis techniques for vector materials. We also elaborated on the problems and future research directions in the development of non-viral vectors, which provided a theoretical basis for their broad applications.

Enhanced Gene Delivery and CRISPR/Cas9 Homology-Directed Repair in Serum by Minimally Succinylated Polyethylenimine

Gene therapy aims to treat patients by altering or controlling gene expression. The field of gene therapy has had increasing success in recent years primarily using viral-based approaches; however, there is still significant interest toward the use of polymeric materials due to their potential as flexible, low-cost scaffolds for gene delivery that do not suffer the mutagenesis and immunogenicity concerns of viral vectors. To address the challenges of efficiency and biocompatibility, a series of zwitterion-like polyethylenimine derivatives (zPEIs) were produced via the succinylation of 2-11.5% of polyethylenimine (PEI) amines. With increasing modification, zPEI polyplexes exhibited decreased serum-protein aggregation and dissociated more easily in the presence of a competitor polyanion when compared to unmodified PEI. Surprisingly, the gene delivery mediated in the presence of serum showed that succinylation of as few as 2% of PEI amines resulted in transgene expression 260- to 480-fold higher than that of unmodified PEI and 50- to 65-fold higher than that of commercial PEI-PEG_2k in HEK293 and HeLa cells, respectively. Remarkably, the same zPEIs also produced 16-fold greater efficiency of CRISPR/Cas9 gene knock-in compared to unmodified PEI in the presence of serum. In addition, we show that 2% succinylation does not significantly decrease polymer/DNA binding ability or serum protein interaction to a significant extent, yet this small modification is still sufficient to provide a remarkable increase in transgene expression and gene knock-in in the presence of serum.

Quinine copolymer reporters promote efficient intracellular DNA delivery and illuminate a protein-induced unpackaging mechanism

Polymeric vehicles that efficiently package and controllably release nucleic acids enable the development of safer and more efficacious strategies in genetic and polynucleotide therapies. Developing delivery platforms that endogenously monitor the molecular interactions, which facilitate binding and release of nucleic acids in cells, would aid in the rational design of more effective vectors for clinical applications. Here, we report the facile synthesis of a copolymer containing quinine and 2-hydroxyethyl acrylate that effectively compacts plasmid DNA (pDNA) through electrostatic binding and intercalation. This polymer system poly(quinine-co-HEA) packages pDNA and shows exceptional cellular internalization, transgene expression, and low cytotoxicity compared to commercial controls for several human cell lines, including HeLa, HEK 293T, K562, and keratinocytes (N/TERTs). Using quinine as an endogenous reporter for pDNA intercalation, Raman imaging revealed that proteins inside cells facilitate the unpackaging of polymer-DNA complexes (polyplexes) and the release of their cargo. Our work showcases the ability of this quinine copolymer reporter to not only facilitate effective gene delivery but also enable diagnostic monitoring of polymer-pDNA binding interactions on the molecular scale via Raman imaging. The use of Raman chemical imaging in the field of gene delivery yields unprecedented insight into the unpackaging behavior of polyplexes in cells and provides a methodology to assess and design more efficient delivery vehicles for gene-based therapies.

Biodegradable Polymers for Gene Delivery

The cellular transport process of DNA is hampered by cell membrane barriers, and hence, a delivery vehicle is essential for realizing the potential benefits of gene therapy to combat a variety of genetic diseases. Virus-based vehicles are effective, although immunogenicity, toxicity and cancer formation are among the major limitations of this approach. Cationic polymers, such as polyethyleneimine are capable of condensing DNA to nanoparticles and facilitate gene delivery. Lack of biodegradation of polymeric gene delivery vehicles poses significant toxicity because of the accumulation of polymers in the tissue. Many attempts have been made to develop biodegradable polymers for gene delivery by modifying existing polymers and/or using natural biodegradable polymers. This review summarizes mechanistic aspects of gene delivery and the development of biodegradable polymers for gene delivery.