Design and evaluation of ionizable peptide amphiphiles for siRNA delivery

Optimizing long-term stability of siRNA using thermoassemble ionizable reverse pluronic-Bcl2 micelleplexes

Thermosassemble Ionizable Reverse Pluronic (TIRP) platform stands out for its distinctive combination of thermoassemble and ionizable features, effectively overcoming challenges in previous siRNA delivery systems. This study opens up a formation for long-term stabilization, and high loading of siRNA, specifically crafted for targeting oncogenic pathways. TIRP-Bcl2 self-assembles into a unique micelle structure with a nanodiameter of 75.8 ± 5.7 nm, efficiently encapsulating Bcl2 siRNA while maintaining exceptional colloidal stability at 4 °C for 8 months, along with controlled release profiles lasting 180 h. The dual ionizable headgroup enhance the siRNA loading and the revers pluronic unique structural orientation enhance the stability of the siRNA. The thermoassemble of TIRP-Bcl2 facilitates flexi-rigid response to mild hyperthermia, enhancing deep tissue penetration and siRNA release in the tumor microenvironment. This responsive behavior improves intracellular uptake and gene silencing efficacy in cancer cells. TIRP, with its smaller particle size and reverse pluronic nature, efficiently transports siRNA across the blood-brain barrier, holding promise for revolutionizing glioblastoma (GBM) treatment. TIRP-Bcl2 shows significant potential for precise, personalized therapies, promising prolonged siRNA delivery and in vitro/in vivo stability. This research opens avenues for further exploration and clinical translation of this innovative nanocarrier system across different cancers.

Targeted Anticancer Agent with Original Mode of Action Prepared by Supramolecular Assembly of Antibody Oligonucleotide Conjugates and Cationic Nanoparticles

Despite their clinical success, Antibody-Drug Conjugates (ADCs) are still limited to the delivery of a handful of cytotoxic small-molecule payloads. Adaptation of this successful format to the delivery of alternative types of cytotoxic payloads is of high interest in the search for novel anticancer treatments. Herein, we considered that the inherent toxicity of cationic nanoparticles (cNP), which limits their use as oligonucleotide delivery systems, could be turned into an opportunity to access a new family of toxic payloads. We complexed anti-HER2 antibody-oligonucleotide conjugates (AOC) with cytotoxic cationic polydiacetylenic micelles to obtain Antibody-Toxic-Nanoparticles Conjugates (ATNPs) and studied their physicochemical properties, as well as their bioactivity in both in vitro and in vivo HER2 models. After optimising their AOC/cNP ratio, the small (73 nm) HER2-targeting ATNPs were found to selectively kill antigen-positive SKBR-2 cells over antigen-negative MDA-MB-231 cells in serum-containing medium. Further in vivo anti-cancer activity was demonstrated in an SKBR-3 tumour xenograft model in BALB/c mice in which stable 60% tumour regression could be observed just after two injections of 45 pmol of ATNP. These results open interesting prospects in the use of such cationic nanoparticles as payloads for ADC-like strategies.

Amphiphilic Polypeptides Obtained by Post-Polymerization Modification of Poly-l-Lysine as Systems for Combined Delivery of Paclitaxel and siRNA

The development of effective anti-cancer therapeutics remains one of the current pharmaceutical challenges. The joint delivery of chemotherapeutic agents and biopharmaceuticals is a cutting-edge approach to creating therapeutic agents of enhanced efficacy. In this study, amphiphilic polypeptide delivery systems capable of loading both hydrophobic drug and small interfering RNA (siRNA) were developed. The synthesis of amphiphilic polypeptides included two steps: (i) synthesis of poly-αl-lysine by ring-opening polymerization and (ii) its post-polymerization modification with hydrophobic l-amino acid and l-arginine/l-histidine. The obtained polymers were used for the preparation of single and dual delivery systems of PTX and short double-stranded nucleic acid. The obtained double component systems were quite compact and had a hydrodynamic diameter in the range of 90-200 nm depending on the polypeptide. The release of PTX from the formulations was studied, and the release profiles were approximated using a number of mathematical dissolution models to establish the most probable release mechanism. A determination of the cytotoxicity in normal (HEK 293T) and cancer (HeLa and A549) cells revealed the higher toxicity of the polypeptide particles to cancer cells. The separate evaluation of the biological activity of PTX and anti-GFP siRNA formulations testified the inhibitory efficiency of PTX formulations based on all polypeptides (IC₅₀ 4.5-6.2 ng/mL), while gene silencing was effective only for the Tyr-Arg-containing polypeptide (56-70% GFP knockdown).

Polymerization in living organisms

Vital biomacromolecules, such as RNA, DNA, polysaccharides and proteins, are synthesized inside cells via the polymerization of small biomolecules to support and multiply life. The study of polymerization reactions in living organisms is an emerging field in which the high diversity and efficiency of chemistry as well as the flexibility and ingeniousness of physiological environment are incisively and vividly embodied. Efforts have been made to design and develop in situ intra/extracellular polymerization reactions. Many important research areas, including cell surface engineering, biocompatible polymerization, cell behavior regulation, living cell imaging, targeted bacteriostasis and precise tumor therapy, have witnessed the elegant demeanour of polymerization reactions in living organisms. In this review, recent advances in polymerization in living organisms are summarized and presented according to different polymerization methods. The inspiration from biomacromolecule synthesis in nature highlights the feasibility and uniqueness of triggering living polymerization for cell-based biological applications. A series of examples of polymerization reactions in living organisms are discussed, along with their designs, mechanisms of action, and corresponding applications. The current challenges and prospects in this lifeful field are also proposed.

Structural Exploration of Polycationic Nanoparticles for siRNA Delivery

RNA interference (RNAi) is a promising approach to the treatment of genetic diseases by the specific knockdown of target genes. Functional polymers are potential vehicles for the effective delivery of vulnerable small interfering RNA (siRNA), which is required for the broad application of RNAi-based therapeutics. The development of methods for the facile modulation of chemical structures of polymeric carriers and an elucidation of detailed delivery mechanisms remain important areas of research. In this paper, we synthesized a series of methacrylate-based polymers with controllable structures and narrow distributions by atom transfer radical polymerization using various combinations of cationic monomers (2-dimethylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate, and 2-dibutylaminoethyl methacrylate) and hydrophobic monomers (2-butyl methacrylate (BMA), cyclohexyl methacrylate, and 2-ethylhexyl methacrylate). These polymers exhibited varying hydrophobicities, charge densities, and pK_a values, enabling the discovery of effective carriers for siRNA by in vitro delivery assays. For the polymers with BMA segments, 50% of cationic segments were beneficial to the formation of siRNA nanoparticles (NPs) and the in vitro delivery of siRNA. The optimal ratio varied for different combinations of cationic and hydrophobic segments. In particular, 20k PMB 0.5, PME 0.5, and PEB 1.0 showed >75% luciferase knockdown. Efficacious delivery was dependent on high siRNA binding, the small size of NPs, and balanced hydrophobicity and charge density. Cellular uptake and endosomal escape experiments indicated that carboxybetaine modification of 20k PMB 0.5 did not remarkably affect the internalization of corresponding NPs after incubation for 6 h but significantly reduced the endosomal escape of NPs, which leads to the notable decrease in delivery efficacy of polymers. These results provide insights into the mechanism of polymer-based siRNA delivery and may inspire the development of novel polymeric carriers.

Electrostatically Controlled ex Situ and in Situ Polymerization of Diacetylene-Containing Peptide Amphiphiles in Living Cells

Precise control of diacetylene-containing peptide amphiphile (DPA) based supramolecular architectures is important for their in cellulo polymerization behaviors and biomedical applications. Herein, we reported two DPAs (cationic PA-NH₂ and zwitterionic PA-OH) with a similar molecular structure, which exhibited completely opposite polymerization behaviors in aqueous solution and living cells. Specifically, PA-NH₂ was unpolymerizable in aqueous solution but underwent in cellulo polymerization to respond to the intracellular microenvironment. On the contrary, zwitterionic PA-OH was polymerized in solution, rather than inside living cells. Based on the results of cell viability and total internal reflection fluorescent microscopy measurement, PA-OH exhibited higher affinity with cell membranes and lower cytotoxicity than those of PA-NH₂. Therefore, it is suggested that the in cellulo polymerization of PA-NH₂ should be responsive for greater cytotoxicity, rather than the membrane affinity. This study provides an in-depth understanding of the role of charge properties in the polymerization behavior of DPAs and seeks their potential biomedical applications.

WRAP-based nanoparticles for siRNA delivery: a SAR study and a comparison with lipid-based transfection reagents

Recently, we designed novel amphipathic cell-penetrating peptides, called WRAP, able to transfer efficiently siRNA molecules into cells. In order to gain more information about the relationship between amino acid composition, nanoparticle formation and cellular internalization of these peptides composed of only three amino acids (leucine, arginine and tryptophan), we performed a structure–activity relationship (SAR) study. First, we compared our WRAP1 and WRAP5 peptides with the C6M1 peptide also composed of the same three amino acids and showing similar behaviors in siRNA transfection. Afterwards, to further define the main determinants in the WRAP activity, we synthesized 13 new WRAP analogues harboring different modifications like the number and location of leucine and arginine residues, the relative location of tryptophan residues, as well as the role of the α-helix formation upon proline insertions within the native WRAP sequence. After having compared the ability of these peptides to form peptide-based nanoparticles (PBNs) using different biophysical methods and to induce a targeted gene silencing in cells, we established the main sequential requirements of the amino acid composition of the WRAP peptide. In addition, upon measuring the WRAP-based siRNA transfection ability into cells compared to several non-peptide transfection agents available on the markets, we confirmed that WRAP peptides induced an equivalent level of targeted gene silencing but in most of the cases with lower cell toxicity as clearly shown in clonogenic assays.

Development of iRGD-Modified Peptide Carriers for Suicide Gene Therapy of Uterine Leiomyoma

Uterine leiomyoma (UL) is one of the most common benign tumors in women that often leads to many reproductive complications. Suicide genetherapy was suggested as a promising approach for UL treatment. In the present study, we describe iRGD ligand-conjugated cysteine-rich peptide carrier RGD1-R6 for targeted DNA delivery to αvβ3 integrin-expressing primary UL cells. The physico-chemical properties, cytotoxicity, transfection efficiency and specificity of DNA/RGD1-R6 polyplexes were investigated. TheHSV-1thymidine kinase encoding plasmid delivery to PANC-1pancreatic carcinoma cells and primary UL cells resulted in significant suicide gene therapy effects. Subsequent ganciclovir treatment decreased cells proliferative activity, induced of apoptosis and promoted cells death.The obtained results allow us to concludethatthe developed RGD1-R6 carrier can be considered a promising candidate for suicide gene therapy of uterine leiomyoma.

Non-Viral Targeted Nucleic Acid Delivery: Apply Sequences for Optimization

In nature, genomes have been optimized by the evolution of their nucleic acid sequences. The design of peptide-like carriers as synthetic sequences provides a strategy for optimizing multifunctional targeted nucleic acid delivery in an iterative process. The optimization of sequence-defined nanocarriers differs for different nucleic acid cargos as well as their specific applications. Supramolecular self-assembly enriched the development of a virus-inspired non-viral nucleic acid delivery system. Incorporation of DNA barcodes presents a complementary approach of applying sequences for nanocarrier optimization. This strategy may greatly help to identify nucleic acid carriers that can overcome pharmacological barriers and facilitate targeted delivery in vivo. Barcode sequences enable simultaneous evaluation of multiple nucleic acid nanocarriers in a single test organism for in vivo biodistribution as well as in vivo bioactivity.