Novel Cationic Triblock Copolymer of Poly[2-(dimethylamino)ethyl methacrylate]-block-poly(β-amino ester)-block-poly[2-(dimethylamino)ethyl methacrylate]: A Promising Non-Viral Gene Delivery System

Hybrid Poly(β-amino ester) Triblock Copolymers Utilizing a RAFT Polymerization Grafting-From Methodology

The biocompatibility, biodegradability, and responsiveness of poly(β-amino esters) (PBAEs) has led to their widespread use as biomaterials for drug and gene delivery. Nonetheless, the step-growth polymerization mechanism that yields PBAEs limits the scope for their structural optimization toward specific applications because of limited monomer choice and end-group modifications. Moreover, to date the post-synthetic functionalization of PBAEs has relied on grafting-to approaches, challenged by the need for efficient polymer-polymer coupling and potentially difficult post-conjugation purification. Here a novel grafting-from approach to grow reversible addition-fragmentation chain transfer (RAFT) polymers from a PBAE scaffold is described. This is achieved through PBAE conversion into a macromolecular chain transfer agent through a multistep capping procedure, followed by RAFT polymerization with a range of monomers to produce PBAE-RAFT hybrid triblock copolymers. Following successful synthesis, the potential biological applications of these ABA triblock copolymers are illustrated through assembly into polymeric micelles and encapsulation of a model hydrophobic drug, followed by successful nanoparticle (NP) uptake in breast cancer cells. The findings demonstrate this novel synthetic methodology can expand the scope of PBAEs as biomaterials.

Poly(β-amino ester)s-based nanovehicles: Structural regulation and gene delivery

The first poly(β-amino) esters (PβAEs) were synthesized more than 40 years ago. Since 2000, PβAEs have been found to have excellent biocompatibility and the capability of ferrying gene molecules. Moreover, the synthesis process of PβAEs is simple, the monomers are readily available, and the polymer structure can be tailored to meet different gene delivery needs by adjusting the monomer type, monomer ratio, reaction time, etc. Therefore, PβAEs are a promising class of non-viral gene vector materials. This review paper presents a comprehensive overview of the synthesis and correlated properties of PβAEs and summarizes the progress of each type of PβAE for gene delivery. The review focuses in particular on the rational design of PβAE structures, thoroughly discusses the correlations between intrinsic structure and effect, and then finishes with the applications and perspectives of PβAEs.

Application of vinyl polymer-based materials as nucleic acids carriers in cancer therapy

Nucleic acid-based therapies have changed the paradigm of cancer treatment, where conventional treatment modalities still have several limitations in terms of efficacy and severe side effects. However, these biomolecules have a short half-life in vivo, requiring multiple administrations, resulting in severe suffering, discomfort, and poor patient compliance. In the early days of (nano)biotechnology, these problems caused concern in the medical community, but recently it has been recognized that these challenges can be overcome by developing innovative formulations. This review focuses on the use of vinyl polymer-based materials for the protection and delivery of nucleic acids in cancer. First, an overview of the properties of nucleic acids and their versatility as drugs is provided. Then, key information on the achievements to date, the most effective delivery methods, and the evaluation of functionalization approaches (stimulatory strategies) are critically discussed to highlight the importance of vinyl polymers in the new cancer treatment approaches. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures.

Poly (β amino esters) copolymers: Novel potential vectors for delivery of genes and related therapeutics

The unique properties of polymers have performed an essential contribution to the drug delivery system by providing an outstanding platform for the delivery of macromolecules and genes. However, the block copolymers have been the subject of many recently published works whose results have demonstrated excellent performance in drug targeting. Poly(β-amino esters) (PβAEs) copolymers are the synthetic cationic polymers that are tailored by chemically joining PβAEs with other additives to demonstrate extraordinary efficiency in designing pre-defined and pre-programmed nanostructures, site-specific delivery, andovercoming the distinct cellular barriers. Different compositional and structural libraries could be generated by combinatorial chemistry and by the addition of various novel functional additives that fulfill the multiple requirements of targeted delivery. These intriguing attributes allow PβAE-copolymers to have customized therapeutic functions such as excellent encapsulation capacity, high stability, and stimuli-responsive release. Here, we give an overview of PβAE copolymers-based formulations along with focusing on most notable improvements such as structural modifications, bio-conjugations, and stimuli-responsive approaches, for safe and effective nucleic acids delivery.

PEGylated cationic nanoassemblies based on triblock copolymers to combine siRNA therapeutics with anticancer drugs

Nowadays, the clinical administration of siRNA therapeutics is still challenging due to the need of safe and efficient delivery carriers. In this context, biodegradable and amphiphilic triblock copolymers (ABC) containing amine-based cationic segments could be a powerful tool for siRNA delivery. Herein, we propose a range of poly(ethylene glycol) (PEG)-poly(2-dimethyl(aminoethyl) methacrylate) (pDMAEMA)-polycaprolactone (PCL) copolymers with different lengths of the blocks and hydrophilic/lipophilic balance to deliver siRNA alone or in association with a conventional anticancer drug. mPEG-pDMAEMA-PCL copolymers were synthesized by a combination of techniques and characterized by NMR analysis, Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). Copolymers were then employed to prepare NPs through nanoprecipitation. NPs based on copolymers with long PCL chains (SSL-NPs and LLL-NPs) showed the best colloidal properties and a highly stable core-shell structure with a better orientation of the PEG fringe on the surface. Concerning siRNA delivery, SSL-NPs based on copolymers with short PEG and pDMAEMA chains showed optimized ability to complex and then deliver siRNA at the cell level. The strong interaction between the nucleic acid and the cationic pDMAEMA blocks of NPs was then confirmed by release studies that showed a sustained release of siRNA within 48 h. The transfection efficiency of NPs was assessed in human melanoma cells. NPs were complexed with a therapeutic siRNA against TUBB3 (TUB-siRNA). We observed the best results with SSL-NPs, probably due to the higher preserved buffer capacity of the pDMAEMA blocks. Finally, in order to give a proof of concept of a possible application in the combined chemo/gene-therapy of cancer, SSL-NPs complexed with TUB-siRNA were loaded with docetaxel (DTX) and then cytotoxicity was evaluated in the same cell line. The co-delivery of TUB-siRNA into NPs appeared to strongly potentiate the anti-proliferative activity of DTX, thus highlighting the combinatory activity of the NPs.

Poly(ethylene glycol)- block-poly(2-aminoethyl methacrylate hydrochloride)-Based Polyplexes as Serum-Tolerant Nanosystems for Enhanced Gene Delivery

Incorporation of poly(ethylene glycol) (PEG) into polyplexes has been used as a promising approach to enhance their stability and reduce unwanted interactions with biomolecules. However, this strategy generally has a negative influence on cellular uptake and, consequently, on transfection of target cells. In this work, we explore the effect of PEGylation on biological and physicochemical properties of poly(2-aminoethyl methacrylate) (PAMA)-based polyplexes. For this purpose, different tailor-made PEG- b-PAMA block copolymers, and the respective homopolymers, were synthesized using the controlled/"living" radical polymerization method based on activators regenerated by electron transfer atom transfer radical polymerization. The obtained data show that PEG- b-PAMA-based polyplexes exhibited a much better transfection activity/cytotoxicity relationship than the corresponding non-PEGylated nanocarriers. The best formulation, prepared with the largest block copolymer (PEG₄₅- b-PAMA₁₆₈) at a 25:1 N/P ratio, presented a 350-fold higher transfection activity in the presence of serum than that obtained with polyplexes generated with the gold standard bPEI. This higher transfection activity was associated to an improved capability to overcome the intracellular barriers, namely the release from the endolysosomal pathway and the vector unpacking and consequent DNA release from the nanosystem inside cells. Moreover, these nanocarriers exhibit suitable physicochemical properties for gene delivery, namely reduced sizes, high DNA protection, and colloidal stability. Overall, these findings demonstrate the high potential of the PEG₄₅- b-PAMA₁₆₈ block copolymer as a gene delivery system.

High transfection efficiency promoted by tailor-made cationic tri-block copolymer-based nanoparticles

Cationic polymer-based vectors have been considered a promising strategy in gene therapy area due to their inherent ability to condense genetic material and successfully transfect cells. However, they usually exhibit high cytotoxicity. In this work, it is proposed the use of a tailor-made gene carrier based on a tri-block copolymer of poly[2-(dimethylamino)ethyl methacrylate] and poly(β-amino ester) (PDMAEMA-b-PβAE-b-PDMAEMA), the influence of the PβAE length being assessed. For this purpose, three different block copolymers were prepared varying the molecular weight of this segment. The obtained materials were characterized by NMR and SEC analyzes. Different polyplexes formulations were prepared and evaluated in terms of physicochemical characterization (ethidium bromide intercalation assay, agarose gel electrophoresis assay, dynamic light scattering, zeta potential analyzes and atomic force microscopy) and biological activity (cytotoxicity, and luciferase and green fluorescent protein expression in Hela and COS-7 cell lines). Among the developed nanosystems, the best polyplex formulation revealed between 40- and 60-fold higher transgene expression, in HeLa and COS-7 cell lines, and much lower cytotoxicity than that observed with branched PEI and TurboFect™. Moreover, these nanosystems present suitable physicochemical properties for gene delivery namely reduced mean diameter and high DNA protection. The results reported here show the enormous potential of this block copolymer as gene carrier.

STATEMENT OF SIGNIFICANCE

Syntheses of PDMAEMA-b-PβAE-b-PDMAEMA block copolymers for an extremely effective non-viral vector. The block copolymer PDMAEMA₃₀₀₀-b-PβAE₁₂₀₀₀-b-PDMAEMA₃₀₀₀-based polyplexes at 100/1N/P ratio exhibits between 40- and 60-fold higher transgene expression in HeLa and COS-7 cell lines than commonly used polymeric non-viral vectors, namely branched PEI (known as the gold standard) and TurboFect™ (commercial available).

The Promising Nanocarrier for Doxorubicin and siRNA Co-delivery by PDMAEMA-based Amphiphilic Nanomicelles

Synergistic effects of anticancer drug and siRNA have displayed superior advantages for cancer therapy. Herein, we deeply analyzed the feasibility that whether doxorubicin (DOX) and siRNA could be co-delivered by mPEG-PCL-graft-PDMAEMA (PECD) micelles, which mediated excellent DNA/siRNA delivery in vitro and in vivo reported in our previous work. DOX-loaded NPs (PECD-D) were developed by nanoprecipitation technology and exhibited high drug loading content (DLC, 9.5%). In vitro cytotoxicity study in MDA-MB-231 cells, PECD-D treated groups had lower IC50 compared to free DOX groups (F-DOX) at different transfection time (24, 48, and 72h), which maybe attribute to its high cellular uptake and endosomal escape properties. The speculation was confirmed with the results of drug release profile in acidic media, flow cytometry analysis and confocal images. Futhermore, Cy5 labeled siRNA was introduced in PECD-D micelles (PECD-D/siRNA) to track the behavior of dual-loaded nanodrug in vitro and in vivo. Flow cytometry analysis presented that DOX and siRNA were successfully co-delivered into cells, the positive cells ratio were 94.6 and 99.5%, respectively. Confocal images showed that not only DOX and siRNA existed in cytoplasm, but DOX traversed endosome/lysosome and entered into cell nucleus. For in vivo tumor-targeting evaluation in BALB/c nude mice, both DOX and Cy5-siRNA could be detected in tumor sites after intravenous injection with PECD-D/siRNA formulation. Therefore, we believed that PECD micelles have a potential ability as DOX and siRNA co-delivery carrier for cancer therapy.