Cationic Polythiophenes as Gene Delivery Enhancer

Cationic Polythiophene as Gene Carrier and Sonosensitizer for Sonodynamic Synergic Gene Therapy of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most lethal and highly malignant tumors. Sonodynamic therapy (SDT) is a new cancer treatment method. One of its unique advantages lies in the treatment of deep tumors due to its excellent tissue penetration ability caused by ultrasound (US). However, most sonosensitizers suffer from weak sonodynamic activity and poor tumor-targeting ability. In addition, small interfering RNA (siRNA) is a promising anticancer drug, and the efficacy of siRNA-based gene therapy largely depends on the cell impermeability of the gene carrier. Here, we designed and synthesized a cationic polythiophene derivative (PT2) that can be used as a siRNA carrier for gene therapy. Moreover, PT2 could generate singlet oxygen (1O2) and hydroxyl radicals (O2•-) under US irradiation, which suggests that PT2 could be used for SDT. Our study discovered that NUDT1 promoted HCC proliferation and inhibited intracellular ROS production. Therefore, si-NUDT1 was designed and synthesized. NUDT1 silencing can inhibit the proliferation of tumor cells and increase the production of intracellular ROS to further improve the efficacy of SDT. Then, si-NUDT1 assembled with PT2 and DSPE-PEG-FA to prepare a novel tumor-targeting nanodrug (PT2-siRNA@PEG-FA) for synergic SDT and gene therapy of HCC.

Conjugated Polyelectrolyte/Single Strand DNA Hybrid Polyplexes for Efficient Nucleic Acid Delivery and Targeted Protein Degradation

Nucleic acid-based therapeutics have gained increasing attention due to their ability to regulate various genetic disorders. However, the safe and effective delivery of nucleic acids to their intended cellular sites remains a challenge, primarily due to poor cell membrane permeation and low in vivo stability. Limitations associated with the commonly used nucleic acid delivering agent viral vectors such as carcinogenesis and immunogenicity have driven scientists to develop various nonviral vectors. In this study, we present a highly efficient nucleic acid delivery system based on cationic conjugated polyelectrolytes and single-strand DNA polyplexes with further application in efficient ubiquitin-regulated targeting protein degradation. These polyplexes, formed by 9TC, an aptamer sequence for estrogen receptor (ERα), and cationic PPET3N2 through electrostatic and hydrophobic interactions, demonstrate improved cellular uptake efficiency as well as enhanced stability against nuclease degradation. Furthermore, by incorporation of 9TC into a proteolysis targeting chimera (PROTAC) molecule (P9TC), PPET3N2/P9TC polyplexes significantly enhance the target protein ERα degradation efficiency. Collectively, our findings suggest that PPET3N2 provides a versatile, low cytotoxicity platform for safe, efficient, and simplified delivery of nucleic acids.

Group 16 conjugated polymers based on furan, thiophene, selenophene, and tellurophene

Five-membered aromatic rings containing Group 16 elements (O, S, Se, and Te), also referred as chalcogenophenes, are ubiquitous building blocks for π-conjugated polymers (CPs). Among these, polythiophenes have been established as a model system to study the interplay between molecular structure, solid-state organization, and electronic performance. The judicious substitution of alternative heteroatoms into polythiophenes is a promising strategy for tuning their properties and improving the performance of derived organic electronic devices, thus leading to the recent abundance of CPs containing furan, selenophene, and tellurophene. In this review, we first discuss the current status of Kumada, Negishi, Murahashi, Suzuki-Miyaura, and direct arylation polymerizations, representing the best routes to access well-defined chalcogenophene-containing homopolymers and copolymers. The self-assembly, optical, solid-state, and electronic properties of these polymers and their influence on device performance are then summarized. In addition, we highlight post-polymerization modifications as effective methods to transform polychalcogenophene backbones or side chains in ways that are unobtainable by direct polymerization. Finally, the major challenges and future outlook in this field are presented.

Di[12]aneN3-Functionalized Green Fluorescent Protein Chromophore for GFP Luminescence Simulation and Efficient Gene Transfection In Vitro and In Vivo

Although a plethora of gene carriers have been developed for potential gene therapy, imageable stimuli-responsive gene vectors with fast access to the nucleus, high biocompatibility, and transfection efficiency are still scarce. Herein, we report the design and synthesis of four dendrite-shaped cationic liposomes, MPA-HBI-R/DOPE (R: n-butyl, 1; n-octyl, 2; n-dodecyl, 3; palmyl, 4), prepared via esterification of 4-alkoxybenzylideneimidazolinone containing aliphatic chains of different lengths (HBI-R), the green fluorescent protein (GFP) chromophore, with a di[12]aneN₃ unit. Liposomes were fabricated via the self-assembly of MPA-HBI-R, assisted with 1,2-dioleoyl-sn-glycerol-3-phosphorylethanolamine (DOPE). These liposomes (MPA-HBI-R/DOPE) exhibited efficient DNA condensation, pH-responsive degradation, excellent cellular biocompatibility (up to 150 μM), and high transfection efficiency. Molecular docking experiments were also used to verify the optimal interaction between MPA-HBI-R and DNA, as well as the fluorescence enhancements. In particular, MPA-HBI-2/DOPE delivered DNA into the nucleus in less than an hour, and its luciferase transfection activity was more than 10 times that by Lipo2000, across multiple cell lines. The GFP chromophore conjugation allowed trackable intracellular delivery and release of DNA in real time via fluorescence imaging. Furthermore, efficient red fluorescent protein (RFP) transfection in zebrafish, with an efficiency of more than 6 times that by Lipo2000, was also achieved. The results not only realized, for the first time, the combination of gene delivery and GFP-simulated light emission, allowing fluorescent tracking and highly efficient gene transfection, but also offered valuable insights into the use of biomimetic chromophore for the development of the next-generation nonviral vectors.

Polythiophenes with Cationic Phosphonium Groups as Vectors for Imaging, siRNA Delivery, and Photodynamic Therapy

In this work, we exploit the versatile function of cationic phosphonium-conjugated polythiophenes to develop multifunctional platforms for imaging and combined therapy (siRNA delivery and photodynamic therapy). The photophysical properties (absorption, emission and light-induced generation of singlet oxygen) of these cationic polythiophenes were found to be sensitive to molecular weight. Upon light irradiation, low molecular weight cationic polythiophenes were able to light-sensitize surrounding oxygen into reactive oxygen species (ROS) while the highest were not due to its aggregation in aqueous media. These polymers are also fluorescent, allowing one to visualize their intracellular location through confocal microscopy. The most promising polymers were then used as vectors for siRNA delivery. Due to their cationic and amphipathic features, these polymers were found to effectively self-assemble with siRNA targeting the luciferase gene and deliver it in MDA-MB-231 cancer cells expressing luciferase, leading to 30-50% of the gene-silencing effect. In parallel, the photodynamic therapy (PDT) activity of these cationic polymers was restored after siRNA delivery, demonstrating their potential for combined PDT and gene therapy.

Light-Controlled in Vitro Gene Delivery Using Polymer-Tethered Spiropyran as a Photoswitchable Photosensitizer

A gene delivery system using spiropyran as a photoswitchable photosensitizer for the controlled photochemical internalization effect was developed by engineering the outer coating of a polyethylenimine/DNA complex with a small amount of spiropyran-containing cationic copolymers. The successful binding of cationic polymers by the polyethylenimine coating was detected by the distance-sensitive fluorescence resonance energy-transfer technique that evidenced the occurrence of energy transfer between fluorescein-labeled cationic copolymers and polyethylenimine-condensed rhodamine-labeled DNA. The ternary polyplexes feature reversible controllability of singlet oxygen generation based on the dual effect of spiropyrans in photochromism and aggregation-induced enhanced photosensitization, allowing significant light-induced amplification of bPEI-mediated in vitro transgene efficiency (from original 15% to final 91%) at a low DNA dose, with the integrity of supercoiled DNA structure unaffected. The use of spiropyran without the need of other photosensitizers circumvents the issue of uncontrolled long-lasting photocytotoxicity in gene delivery.

Remarkable Amplification of Polyethylenimine-Mediated Gene Delivery Using Cationic Poly(phenylene ethynylene)s as Photosensitizers

Conjugated polymers can serve as good photosensitizers in biomedical applications. However, it remains unknown whether they are phototoxic to the supercoiled structure of DNA in improving gene delivery by the photochemical internalization (PCI) strategy, which complicates the application of conjugated polymers in gene delivery. In this work, we introduced a trace amount of cationic poly(phenylene ethynylene)s (cPPEs) into the polymeric shell of branched polyethylenimine (BPEI)/DNA complexes, studied the photosensitization of singlet oxygen by cPPEs, and confirmed that the supercoiled DNA is undamaged by the singlet oxygen generated by the photoexcitation of cPPEs. By taking advantage of the cPPE-mediated PCI effect, we report that the addition of the trace amount of cPPEs to the outer shell of the BPEI/DNA polyplexes could greatly amplify the transfection of gene green fluorescent protein on tumor cells with the efficiency from 14 to 86% without decreasing the cell viabilities, well solving the problem with a poor transfection capability of BPEI under low DNA-loading conditions. Our strategy to employ conjugated polymers as photosensitizing agents in gene delivery systems is simple, safe, efficient, and promising for broad applications in gene delivery areas.

Synthesis of Structurally Defined Cationic Polythiophenes for DNA Binding and Gene Delivery

Water-soluble conjugated polymers (WCPs) have prospective applications in the field of bioimaging, disease diagnosis, and therapy. However, the use of WCPs with controllability and regioregularity for bioapplications have scarcely been reported. In this work, we synthesized polythiophenes containing ester side chains (P3ET) via Kumada catalyst-transfer polycondensation (KCTP) and confirmed a quasi-"living" chain-growth mechanism. In addition, we obtained cationic regioregular polythiophenes (cPTs) by aminolysis of P3ET with varied chain lengths, and studied DNA binding capability and gene delivery performance. Benefiting from photocontrolled generation of intracellular reactive oxygen species (ROS), the cationic polythiophenes successfully delivered DNA into tumor cells without additional polymer species.