TACN-based cationic lipids with amino acid backbone and double tails: Materials for non-viral gene delivery

Red fluorescent AIEgens based multifunctional nonviral gene vectors for the efficient combination of gene therapy and photodynamic therapy in anti-cancer

Precise molecular engineering of AIEgens-based cationic delivery systems for high transfection efficiency (TE) and effective photodynamic therapy (PDT) holds a huge potential for cancer treatment. Herein, three amphiphiles (DT-C_6/8/12-M) consisting of di(triazole-[12]aneN₃) (M) and 1,1-dicyano-2-phenyl-2-(4-diphenylamino)phenyl-ethylene (DT) units have been developed to achieve luminescent tracking, efficient TE, and effective PDT in vitro and in vivo. These compounds exhibited strong aggregated induced emission (AIE) at 630 nm and mega Stokes shifts of up to 160 nm. They were able to bind DNA into nanoparticles with suitable sizes, positive surface potential, and good biocompatibility in the presence of DOPE. Among them, vector DT-C₁₂-M/DOPE with n-dodecyl linker achieved a transfection efficiency as high as 42.3 folds that of Lipo2000 in PC-3 cell lines. DT-C₁₂-M/DOPE exhibited the capability of successful endo/lysosomal escape and rapid nuclear delivery of pDNA, and the gene delivery process was clearly monitored via confocal laser scanning microscopy. Moreover, efficient reactive oxygen species (ROS) generation by DT-C₁₂-M upon light irradiation led to effective PDT in vitro . We further show that combination of p53 gene therapy and PDT dramatically enhanced cancer therapeutic outcome in vivo. This "three birds, one stone" strategy offers a novel and promising approach for real-time tracking of gene delivery and better cancer treatment.

pH-sensitive, tail-modified, ester-linked ionizable cationic lipids for gene delivery

Ionizable cationic lipids have great potential for gene delivery, yet the effect of the molecular structure of such lipids on gene delivery efficiency is an ongoing research challenge. To better understand corresponding structure-function activity relationships, we synthesized four ester-linked, pH-responsive, ionizable cationic lipids. The screened DEDM4 lipid, containing 2-ethylenedimethylamine in the headgroup and a branched-chain tail, exhibited a high delivery efficacy of plasmid DNA and siRNA in A549 cells, which was comparable with that of the commercial reagent lipofectamine 3000 (lipo3000). Moreover, because of its pK_a value of 6.35 and pH-sensitivity under acidic conditions, DEDM4 could carry sufficient positive charge in the acidic environment of endosomes and interact with the endosome lumen, leading to destruction of the endomembrane and subsequent release of siRNA into the cytoplasm with endosomal escape. Furthermore, we used DEDM4 to deliver IGF-1R siRNA to induce cancer cell apoptosis, thereby leading to great tumor inhibition. More importantly, it also showed very low toxicity in vivo. These structure-activity data for DEDM4 demonstrate potential clinical applications of DEDM4-mediated gene delivery for cancer.

Multifunctional amphiphilic peptide dendrimer as nonviral gene vectors for effective cancer therapy via combined gene/photodynamic therapies

Gene therapy holds great promise for treatment of gene-associated diseases. However, safe and successful clinical application urgently requires further advancement of constructing efficient delivery systems. Herein, three amphiphilic peptide dendrimers (TTC-L-KRR/KKK/KHH), containing the natural amino acid residues (lysine K, arginine R, and histidine H) and AIE-based photosensitizer (tetraphenylethenethiophene modified cyanoacrylate, TTC) modified with alkyl chain (L), have been designed and prepared for improving therapeutic potency via the combination of gene therapy (GT) and photodynamic therapy (PDT). All three compounds possessed typical aggregation-induced emission (AIE) characteristics and ultralow critical micelle concentrations (CMCs). The liposomes consisting of amphiphilic peptide dendrimers and dioleoylphosphatidylethanolamine (DOPE) can effectively bind DNA into nanoparticles with appropriate sizes, regular morphology and good biocompatibility. Among them, liposomes TTC-L-KKK/DOPE exhibited the highest transfection efficiency up to 5.7-fold as compared with Lipo2000 in HeLa cells. Meanwhile, rapid endocytosis, successful endo/lysosomal escape, gene release and rapid nuclear delivery of DNA revealed the superiority of liposomes TTC-L-KKK/DOPE during gene delivery process. More importantly, efficient reactive oxygen species (ROS) generation by TTC-L-KKK/DOPE led to effective PDT, thus improving therapeutic potency via combining with p53 mediated-gene therapy. Our work brought novel insight and direction for the construction of bio-safe and bio-imaging liposome as the multifunctional nonviral gene vectors for the effective combined gene/photodynamic therapies.

Two-Photon Near-Infrared AIE Luminogens as Multifunctional Gene Carriers for Cancer Theranostics

Construction of multifunctional nonviral gene vectors to execute defined tasks holds great potential for the precise and effective treatment of gene-associated diseases. Herein, we have developed four large π-conjugation triphenylamine derivatives bearing two polar [12]aneN₃ heads and a lipophilic tail for applications in gene delivery, one/two-photon-triggered near-infrared (NIR) fluorescence bioimaging, and combined photodynamic therapy (PDT) and gene therapy of cancer. These compounds possess typical NIR aggregation-induced emission characteristics, mega Stokes shifts, strong two-photon excitation fluorescence, and excellent DNA condensation abilities. Among them, vector 4 with a tail of n-hexadecane realized a transfection efficiency as high as 6.7 times that of the commercial transfection agent Lipofectamine 2000 in HEK293T cell lines. Using vector 4 as an example, transfection process tracking and ex vivo/in vivo tumoral imaging and retention with high resolution, high brightness, deep tissue penetration, and good biosafety were demonstrated. In addition, efficient singlet oxygen (¹O₂) generation by the DNA complex formed by vector 4 (4/DNA) resulted in effective PDT. Combined with anticancer gene therapy, collaborative cancer treatment with a dramatically enhanced cancer cell-killing effect was achieved. The development of this "three birds, one stone" approach suggests a new and promising strategy for better cancer treatment and real-time tracking of gene delivery.

Cationic lipids for gene delivery: many players, one goal

Lipid-based carriers represent the most widely used alternative to viral vectors for gene expression and gene silencing purposes. This class of non-viral vectors is particularly attractive for their ease of synthesis and chemical modifications to endow them with desirable properties. Despite combinatorial approaches have led to the generation of a large number of cationic lipids displaying different supramolecular structures and improved behavior, additional effort is needed towards the development of more and more effective cationic lipids for transfection purposes. With this review, we seek to highlight the great progress made in the design of each and every constituent domain of cationic lipids, that is, the chemical structure of the headgroup, linker and hydrophobic moieties, and on the specific effect on the assembly with nucleic acids. Since the complexity of such systems is known to affect their performances, the role of formulation, stability and phase behavior on the transfection efficiency of such assemblies will be thoroughly discussed. Our objective is to provide a conceptual framework for the development of ever more performing lipid gene delivery vectors.

A reduction-responsive liposomal nanocarrier with self-reporting ability for efficient gene delivery

In the past few decades, although various reduction-responsive nanocarriers have been designed and explored for gene delivery, it is difficult to directly detect or monitor the reduction capability of these carriers, especially under intracellular conditions. Taking advantage of the generated fluorescence signal in the reduction process of the naphthalimide-sulfonamide (NS) group, we developed a novel liposomal nanocarrier, FNSL, which showed reduction-sensitive property and self-reporting character. As a new reduction-responsive site in a gene delivery system, the NS group in FNSL is capable of responding to glutathione (GSH) and simultaneously emitting green fluorescence at 500 nm in both extra- and intracellular circumstances. Hence, it will be very convenient to assess the reducibility of this carrier and monitor the stimuli-responsive gene release via fluorescence signal. FNSL has high affinity for DNA and can condense it into nanoparticles with a proper nano-size and zeta potential. Compared with the non-reducible FNAL, FNSL showed enhanced gene release capability, higher transfection efficiency (TE), and lower cytotoxicity. Furthermore, treatment of FNSL-mediated transfection with slightly exogenous GSH greatly improved the TE of FNSL in HepG2 cells, and its TE was even higher than that of Lipofectamine 2000. These results demonstrate that FNSL possesses great potential for efficient and low-toxicity gene delivery, and this study on a bioreducible liposome with self-reporting ability would be a guide for further research on the development of biodegradable gene carriers.

Self-assembled core–shell-corona multifunctional non-viral vector with AIE property for efficient hepatocyte-targeting gene delivery

Core–shell-corona multifunctional nanoparticles were prepared and used for cell imaging and cell-targeting delivery of genes toward hepatocytes.

Low Molecular Weight Oligomers with Aromatic Backbone as Efficient Nonviral Gene Vectors

A series of oligomers were synthesized via ring-opening polymerization. Although the molecular weights of these oligomers are only ∼2.5 kDa, they could efficiently bind and condense DNA into nanoparticles. These oligomers gave comparable transfection efficiency (TE) to PEI 25 kDa, while their TE could even increase with the presence of serum, and up to 65 times higher TE than PEI was obtained. The excellent serum tolerance was also confirmed by TEM, flow cytometry, and BSA adsorption assay. Moreover, structure-activity relationship studies revealed some interesting factors. First, oligomers containing aromatic rings in the backbone showed better DNA binding ability. These materials could bring more DNA cargo into the cells, leading to much better TE. Second, the isomerism of the disubstituted phenyl group on the oligomer backbone has large effect on the transfection. The ortho-disubstituted ones gave at least 1 order of magnitude higher TE than meta- or para-disubstituted oligomers. Gel electrophoresis involving DNase and heparin indicated that the difficulty to release DNA might contribute to the lower TE of the latter. Such clues may help us to design novel nonviral gene vectors with high efficiency and biocompatibility.

Structure–activity relationship studies of symmetrical cationic bolasomes as non-viral gene vectors

Bolalipids based on lysine or cyclen headgroups were synthesized and their structure–activity relationship as gene delivery vectors was studied.

Hydroxyl-containing non-viral lipidic gene vectors with macrocyclic polyamine headgroups

The gene transfection abilities and structure–activity relationship of the newly designed hydroxyl-containing cationic lipids were studied in detail.

Cyclen-based cationic lipids containing a pH-sensitive moiety as gene delivery vectors

Imidazole-functionalized cationic lipids with a cyclen headgroup were synthesized, and the structure–activity relationship in gene delivery mediated by these lipids was discussed.

Hybrid Nanomaterial Complexes for Advanced Phage-guided Gene Delivery

Developing nanomaterials that are effective, safe, and selective for gene transfer applications is challenging. Bacteriophages (phage), viruses that infect bacteria only, have shown promise for targeted gene transfer applications. Unfortunately, limited progress has been achieved in improving their potential to overcome mammalian cellular barriers. We hypothesized that chemical modification of the bacteriophage capsid could be applied to improve targeted gene delivery by phage vectors into mammalian cells. Here, we introduce a novel hybrid system consisting of two classes of nanomaterial systems, cationic polymers and M13 bacteriophage virus particles genetically engineered to display a tumor-targeting ligand and carry a transgene cassette. We demonstrate that the phage complex with cationic polymers generates positively charged phage and large aggregates that show enhanced cell surface attachment, buffering capacity, and improved transgene expression while retaining cell type specificity. Moreover, phage/polymer complexes carrying a therapeutic gene achieve greater cancer cell killing than phage alone. This new class of hybrid nanomaterial platform can advance targeted gene delivery applications by bacteriophage.

Cationic gemini lipids with cyclen headgroups: interaction with DNA and gene delivery abilities

Eleven Gemini cationic lipids and one mono counterpart were synthesized, and their structure–activity relationship as non-viral gene vectors was studied.