Combination of Backbone Rigidity and Richness in Aryl Structures Enables Direct Membrane Translocation of Polymer Scaffolds for Efficient Gene Delivery

The development of cell-penetrating polymers with endocytosis-independent cell uptake pathways has emerged as a prominent strategy to enhance the transfection efficiency. Inspired by the rigid α-helical structure that endows polypeptides with cell-penetrating ability, we propose that a rigid backbone can facilitate the corresponding polymer vector's performance in gene delivery by bypassing the difficult endosomal escape process. Meanwhile, the installation of aromatic domains, as a way to promote gene transfection efficiency, is employed through the construction of a poly(benzyl ether) (PBE)-based scaffold in this work. We demonstrate that the direct membrane translocation capability of the synthesized PBE contributes to its enhanced transfection performance and excellent biocompatibility profile, rendering the imidazolium-functionalized PBE scaffold with higher activity and biocompatibility. Molecular details of the PBE-lipid interaction are also revealed in molecular dynamics simulations, indicating the important roles of individual structural elements on the polymeric scaffold in the membrane penetration process.

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.

Zn(ii) coordination to cyclen-based polycations for enhanced gene delivery

Zn²⁺ coordination greatly improved the gene transfection efficiency of cyclen-based polycations.

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

The linking and modification of low molecular weight cationic polymers (oligomers) has become an attracted strategy to construct non-viral gene carriers with good transfection efficiency and much reduced cytotoxicity. In this study, PEI 600 Da was linked by biodegradable bridges containing rigid aromatic rings. The introduction of aromatic rings enhanced the DNA-binding ability of the target polymers and also improved the stability of the formed polymer/DNA complexes. The biodegradable property and resulted DNA release were verified by enzyme stimulated gel electrophoresis experiment. These materials have lower molecular weights compared to PEI 25 kDa, but exhibited higher transfection efficiency, especially in the presence of serum. Flow cytometry and confocal laser scanning microscopy results indicate that the polymers with aromatic rings could induce higher cellular uptake. This strategy for the construction of non-viral gene vectors may be applied as an efficient and promising method for gene delivery.

Aromatic Thioacetal-Bridged ROS-Responsive Nanoparticles as Novel Gene Delivery Vehicles

In this report, a series of polycations are designed and synthesized by conjugating reactive oxygen species (ROS)-responsive thioacetal-linkers to low molecular weight (LMW) polyethylenimine (PEI) via ring-opening polymerization. Their structure⁻activity relationships (SARs) as gene delivery vectors are systematically studied. Although the MWs of the target polymers are only ~9 KDa, they show good DNA binding ability. The formed polyplexes, which are stable toward serum but decomposed under ROS-conditions, have appropriate sizes (180~300 nm) and positive zeta-potentials (+35~50 mV). In vitro experiments reveal that these materials have low cytotoxicity, and higher transfection efficiency (TE) than controls. Furthermore, the title polymers exhibit excellent serum tolerance. With the present of 10% serum, the TE of the polymers even increases up to 10 times higher than 25 KDa PEI and 9 times higher than Lipofectamine 2000. The SAR studies also reveal that electron-withdrawing groups on the aromatic ring in 4a may benefit to balance between the DNA condensation and release for efficient gene transfection.

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.

Functionalized Asymmetric Bola-Type Amphiphiles for Efficient Gene and Drug Delivery

The studies of bolaamphiphile-based nanoparticles as delivery vectors are still rudimentary and under development. In this study, several asymmetric bolaamphiphiles containing lysine and another moiety with special functions, such as pH-sensitive or cell-targeting property, were designed and synthesized. The potentials of these bolaamphiphile-based nanoparticles as versatile vectors for both nucleic acids and chemical drugs were studied. With the presence of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), these amphiphiles could be prepared into bolasomes, which showed good DNA binding ability and could condense plasmid DNA into nanoparticles with appropriate size and surface potential. Lys-His, which has a pH-sensitive histidine on one head, exhibited higher transfection efficiency than the symmetric counterpart and comparable efficiency to commercially available transfection reagent. Mechanism studies confirmed that the bolaplexes formed from Lys-His might induce the highest cellular uptake and the best endosomal escape ability. On the other hand, these bolaamphiphiles also exhibited good drug loading ability. The self-assembly vesicles could efficiently encapsulate the hydrophobic anti-cancer drug doxorubicin (DOX) in aqueous solution with high drug loading content and encapsulation efficiency. Confocal laser scanning microscopy (CLSM) experiment and cell viability assay exhibited a controlled release of the drug with the assistance of bolasomes. It was shown that such bolaamphiphiles have great potential as nano-vectors for both drug and gene or their co-delivery.

Aromatic Modification of Low Molecular Weight PEI for Enhanced Gene Delivery

Low molecular weight polyethylenimine (1800 Da, also referred to as oligoethylenimines, OEI) was modified with amino acids, including two aromatic amino acids (tryptophan, phenylalanine) and an aliphatic amino acid (leucine). The substitution degree of amino acids could be controlled by adjusting the feeding mole ratio of the reactants. Fluorescence spectroscopy and circular dichroism experiments demonstrated that the indole ring of tryptophan may intercalate into the DNA base pairs and contribute to efficient DNA condensation. In vitro gene expression results revealed that the modified OEIs (OEI-AAs) may provide higher transfection efficiency even than high molecular weight polyethylenimine (25 kDa, PEI), especially the aromatic tryptophan substituted OEI. Moreover, OEI-AAs exhibited excellent serum tolerance, and up to 137 times higher transfection efficiency than PEI 25 kDa that was obtained in the presence of serum. The cytotoxicity of OEI-AAs is much lower than PEI 25 kDa. This study may afford a new method for the development of low molecular weight oligomeric non-viral gene vectors with both high efficiency and biocompatibility.

Gemini-Type Tetraphenylethylene Amphiphiles Containing [12]aneN3 and Long Hydrocarbon Chains as Nonviral Gene Vectors and Gene Delivery Monitors

Four gemini amphiphiles decorated with triazole-[12]aneN₃ as the hydrophilic moiety and various long hydrocarbons as hydrophobic moieties, 1-4, were designed to form micelles possessing the aggregation-induced emission (AIE) property for gene delivery and tracing. All four amphiphiles give ultralow critical micelle concentrations, are pH-/photostable and biocompatible, and completely retard the migration of plasmid DNAs at low concentrations. The DNA-binding abilities of the micelles were fully assessed. The coaggregated nanoparticles of 1-4 with DNAs could convert back into AIE micelles. In vitro transfections indicated that lipids 1 and 2 and their originated liposomes bearing decent delivering abilities have great potentials as nonviral vectors. Finally, on the basis of the transfection and the transitions between condensates and micelles, lipid 2 was singled out as the first example for real-time tracing of the intracellular deliveries of nonlabeled DNA, which provides spatiotemporal messages about the processes of condensate uptake and DNA release.

Biodegradable Poly(Amino Ester) with Aromatic Backbone as Efficient Nonviral Gene Delivery Vectors

The development of gene delivery vectors with high efficiency and biocompatibility is one of the critical points of gene therapy. Two biodegradable poly(amino ester)s were synthesized via ring-opening polymerization between low molecular weight (LMW) PEI and diepoxide. The molecular weights of poly(amino ester)s were measured by GPC. Agarose gel retardation assays showed that these materials have good DNA-binding ability and can retard the electrophoretic mobility of plasmid DNA (pDNA) at a weight ratio of 1. The formed polyplexes have proper sizes of around 200 nm and zeta-potential values of about 30-40 mV for cellular uptake. In vitro experiments revealed that polymer P2 gave higher transfection efficiency than PEI 25KDa and Lipofectamine 2000 with less toxicity, especially in 293 cells. Results demonstrate that such a type of degradable poly(amino ester) may serve as a promising non-viral gene vector.

Degradable polyesters via ring-opening polymerization of functional valerolactones for efficient gene delivery

Degradable polymers as gene and drug carriers are emerging as one of the most promising types of materials in the biomedical and pharmaceutical areas.

Cationic lipids with a cyclen headgroup: synthesis and structure–activity relationship studies as non-viral gene vectors

The structure–activity relationships of cyclen-based cationic lipids as non-viral gene delivery vectors were studied and clarified.

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.

Carbon Dots and 9AA as a Binary Matrix for the Detection of Small Molecules by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

Application of matrix-assisted laser-desorption/ionization mass spectrometry (MALDI MS) to analyze small molecules have some limitations, due to the inhomogeneous analyte/matrix co-crystallization and interference of matrix-related peaks in low m/z region. In this work, carbon dots (CDs) were for the first time applied as a binary matrix with 9-Aminoacridine (9AA) in MALDI MS for small molecules analysis. By 9AA/CDs assisted desorption/ionization (D/I) process, a wide range of small molecules, including nucleosides, amino acids, oligosaccharides, peptides, and anticancer drugs with a higher sensitivity were demonstrated in the positive ion mode. A detection limit down to 5 fmol was achieved for cytidine. 9AA/CDs matrix also exhibited excellent reproducibility compared with 9AA matrix. Moreover, by exploring the ionization mechanism of the matrix, the influence factors might be attributed to the four parts: (1) the strong UV absorption of 9AA/CDs due to their π-conjugated network; (2) the carboxyl groups modified on the CDs surface act as protonation sites for proton transfer in positive ion mode; (3) the thin layer crystal of 9AA/CDs could reach a high surface temperature more easily and lower transfer energy for LDI MS; (4) CDs could serve as a matrix additive to suppress 9AA ionization. Furthermore, this matrix was allowed for the analysis of glucose as well as nucleosides in human urine, and the level of cytidine was quantified with a linear range of 0.05-5 mM (R(2) > 0.99). Therefore, the 9AA/CDs matrix was proven to be an effective MALDI matrix for the analysis of small molecules with improved sensitivity and reproducibility. This work provides an alternative solution for small molecules detection that can be further used in complex samples analysis. Graphical Abstract ᅟ.

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.

meso-Mono-[4-(1,4,7-triazacyclononanyl)]-tri(phenyl)]porphyrin and the respective zinc(ii)-complex: complete characterization and biomolecules binding abilities

We aimed to synthesize a new series of triazacyclononanyl-porphyrins (4and5) with the potential ability to bind DNA.

Synthesis of bifunctional molecules containing [12]aneN3 and coumarin moieties as effective DNA condensation agents and new non-viral gene vectors

Bifunctional molecules with different combinations of [12]aneN₃ and coumarin moieties were successfully applied in DNA condensation and gene transfection.

Recycling gene carrier with high efficiency and low toxicity mediated by L-cystine-bridged bis(β-cyclodextrin)s

Constructing safe and effective gene delivery carriers is becoming highly desirable for gene therapy. Herein, a series of supramolecular crosslinking system were prepared through host-guest binding of adamantyl-modified low molecular weight of polyethyleneimine with L-cystine-bridged bis(β-cyclodextrin)s and characterized by ¹H NMR titration, electron microscopy, zeta potential, dynamic light-scattering, gel electrophoresis, flow cytometry and confocal fluorescence microscopy. The results showed that these nanometersized supramolecular crosslinking systems exhibited higher DNA transfection efficiencies and lower cytotoxicity than the commercial DNA carrier gold standard (25 kDa bPEI) for both normal cells and cancer cells, giving a very high DNA transfection efficiency up to 54% for 293T cells. Significantly, this type of supramolecular crosslinking system possesses a number of enzyme-responsive disulfide bonds, which can be cleaved by reductive enzyme to promote the DNA release but recovered by oxidative enzyme to make the carrier renewable. These results demonstrate that these supramolecular crosslinking systems can be used as promising gene carriers.

Ring-opening polymerization for hyperbranched polycationic gene delivery vectors with excellent serum tolerance

In order to improve the transfection efficiency (TE) and biocompatibility, we synthesized a series of hyperbranched cationic polymers by ring-opening polymerization between diepoxide and several polyamines. These materials can condense plasmid DNA efficiently into nanoparticles that have much lower cytotoxicity than those derived from bPEI. In vitro transfection experiments showed that polymers prepared from branched or cyclic polyamine (P1 and P5) exhibited TE several times higher than 25KDa bPEI. More significantly, serum seemed to have no negative effect on P1-P5 mediated transfection. On the contrary, the TE of P1 improved, even when the serum concentration reached 70%. Several assays demonstrated the excellent serum tolerance of such polycationic vectors: bovine serum albumin (BSA) adsorption assay revealed considerably lower protein adsorption of P1-P5 than PEI; P1 showed better DNA protection ability from degradation by DNase I than PEI; flow cytometry results suggested that any concentration of serum may not decrease the cellular uptake of P1/DNA polyplex; and confocal laser scanning microscopy also found that serum has little effect on the transfection. By using specific cellular uptake inhibitors, we found that the polyplexes enter the cells mainly via caveolae and microtubule-mediated pathways. We believe that this ring-opening polymerization may be an effective synthetic approach toward gene delivery materials with high biological activity.