Pluronic-based cationic block copolymer for forming pDNA polyplexes with enhanced cellular uptake and improved transfection efficiency

α-Amino acid N-carboxyanhydride (NCA)-derived synthetic polypeptides for nucleic acids delivery

In recent years, gene therapy has come into the spotlight for the prevention and treatment of a wide range of diseases. Polypeptides have been widely used in mediating nucleic acid delivery, due to their versatilities in chemical structures, desired biodegradability, and low cytotoxicity. Chemistry plays an essential role in the development of innovative polypeptides to address the challenges of producing efficient and safe gene vectors. In this Review, we mainly focused on the latest chemical advances in the design and preparation of polypeptide-based nucleic acid delivery vehicles. We first discussed the synthetic approach of polypeptides via ring-opening polymerization (ROP) of N-carboxyanhydrides (NCAs), and introduced the various types of polypeptide-based gene delivery systems. The extracellular and intracellular barriers against nucleic acid delivery were then outlined, followed by detailed review on the recent advances in polypeptide-based delivery systems that can overcome these barriers to enable in vitro and in vivo gene transfection. Finally, we concluded this review with perspectives in this field.

Mixed Polyplex Micelles with Thermoresponsive and Lysine-Based Zwitterionic Shells Derived from Two Poly(vinyl amine)-Based Block Copolymers

Two series of poly(vinyl amine) (PVAm)-based block copolymers with zwitterionic and thermoresponsive segments were synthesized by the reversible addition-fragmentation chain transfer polymerization. A mixture of the two copolymers, poly(N-acryloyl-l-lysine) (PALysOH) and poly(N-isopropylacrylamide) (PNIPAM), which have the same cationic PVAm chain but different shell-forming segments, were used to prepare mixed polyplex micelles with DNA. Both PVAm-b-PALysOH and PVAm-b-PNIPAM showed low cytotoxicity, with characteristic assembled structures and stimuli-responsive properties. The cationic PVAm segment in both block copolymers showed site-specific interactions with DNA, which were evaluated by dynamic light scattering, zeta potential, circular dichroism, agarose gel electrophoresis, atomic force microscopy, and transmission electron microscopy measurements. The PVAm-b-PNIPAM/DNA polyplexes showed the characteristic temperature-induced formation of assembled structures in which the polyplex size, surface charge, chiroptical property of DNA, and polymer-DNA binding were governed by the nitrogen/phosphate (N/P) ratio. The DNA binding strength and colloidal stability of the PVAm-b-PALysOH/DNA polyplexes could be tuned by introducing an appropriate amount of zwitterionic PALysOH functionality, while maintaining the polyplex size, surface charge, and chiroptical property, regardless of the N/P ratio. The mixed polyplex micelles showed temperature-induced stability originating from the hydrophobic (dehydrated) PNIPAM chains upon heating, and remarkable stability under salty conditions owing to the presence of the zwitterionic PALysOH chain on the polyplex surface.

Absence of Albumin Improves in Vitro Cellular Uptake and Disruption of Poloxamer 407-Based Nanoparticles inside Cancer Cells

Novel nanoparticles based on Poloxamer 407 and vegetable oil were produced by high pressure homogenization. Functionalization of those nanoparticles was made by incorporation of folic acid (FA)-Poloxamer 407 conjugate. These nanoparticles showed suitable characteristics for intravenous therapeutic applications similarly to PEGylated albumin-based nanoparticles, previously described by our research group. Here, we found that the absence of albumin at the interface of Poloxamer 407-based nanoparticles improves the overall process of in vitro cellular uptake and nanoparticle disruption inside cancer cells (folate receptor, FR, positive cells). The results presented here suggest that interfacial composition of those nanoparticles is of paramount importance for drug trafficking inside cancer cells.

Recent progress in drug delivery of pluronic P123: pharmaceutical perspectives

This review focuses on recent investigations that used Pluronic P123 (P123) as pharmaceutical ingredients in vesicle, micelle, mixed micelle, in situ gel, tablet and emulsion. The main results from these studies show that P123 can significantly increase the stability of incorporated hydrophobic drugs with enhanced in vitro cytotoxicity and cellular uptake of anticancer drugs. Moreover, modified forms of P123 with RGD, folate or other targeted marker have shown its therapeutic potentials in various types of tumors and cancers. Furthermore, modified forms of P123 alone and/or mixed with other copolymers have less toxic effects and more tumor-specific delivery of anticancer drugs. They are promising materials as a nanoplatform for the drug delivery. Finally, the future perspectives of the field are briefly discussed.

Factors influencing the transfection efficiency and cellular uptake mechanisms of Pluronic P123-modified polypropyleneimine/pDNA polyplexes in multidrug resistant breast cancer cells

Generally, the major obstacles for efficient gene delivery are cellular internalization and endosomal escape of nucleic acid such as plasmid DNA (pDNA) or small interfering RNA (siRNA). We previously developed Pluronic P123 modified polypropyleneimine (PPI)/pDNA (P123-PPI/pDNA) polyplexes as a gene delivery system. The results showed that P123-PPI/pDNA polyplexes revealed higher transfection efficiency than PPI/pDNA polyplexes in multidrug resistant breast cancer cells. As a continued effort, the present investigation on the factors influencing the transfection efficiency, cellular uptake mechanisms, and intracellular fate of P123-PPI/pDNA polyplexes is reported. The presence of P123 was the main factor influencing the transfection efficiency of P123-PPI/pDNA polyplexes in MCF-7/ADR cells, but other parameters, such as N/P ratio, FBS concentration, incubation time and temperature were important as well. The endocytic inhibitors against clathrin-mediated endocytosis (CME), caveolae-mediated endocytosis (CvME), and macropinocytosis were involved in the internalization to investigate their effects on the cellular uptake and transfection efficiency of P123-PPI/pDNA polyplexes in vitro. The data showed that the internalization of P123-PPI/pDNA polyplexes was obtained from both CME and CvME. Colocalization experiments with TRITC-transferrin (CME indicator), Alexa Fluor 555-CTB (CvME indicator), monoclonal anti-α-tubulin (microtubule indicator), and LysoTracker Green (Endosome/lysosome indicator) were carried out to confirm the internalization routes. The results showed that both CME and CvME played vital roles in the effective transfection of P123-PPI/pDNA polyplexes. Endosome/lysosome system and skeleton, including actin filament and microtubule, were necessary for the transportation after internalization.

Nanomedicine for gene therapy

Viruses are promising vehicles that result in high gene expression level, but issues of safety and virulent nature prevented its extensive use. Therefore, nonviral approach was investigated with the intervention of nanomedicine. The science of nanomedicine offered an excellent platform for therapeutic delivery as they provide options to include functionalities and engineer the system. As the term 'nano' refers to the generation of a very small dimension structure, their unique physicochemical characteristics with increased surface area/volume ratio made them potential vectors to perform gene therapy. Various forms of nanoparticles are continued to be synthesised, and this review discusses the immediate barriers that nanoparticles have to encounter both during systemic movement in the body and intracellular trafficking to deliver the genes at the site of action.

Recent progress in biomedical applications of Pluronic (PF127): Pharmaceutical perspectives

Most of the administered anti-cancer drugs are hydrophobic in nature and are known to have poor water solubility, short residence time, rapid clearance from the body and systemic side effects. Polymeric-based targeted particulate carrier system has shown to directly deliver the encapsulated anti-cancer drug to the desired site of action and prevent the interaction of encapsulated drug with the normal cells. Pluronic F127 (PF127) has been widely investigated for its broad-range of therodiagnostic applications in biomedical and pharmaceutical sciences, but rapid dissolution in the physiological fluids, short residence time, rapid clearance, and weak mechanical strength are the main shortcomings that are associated with PF127 and have recently been overcome by making various modifications in the structure of PF127 notably through preparation of PF127-based mixed polymeric micelles, PF127-conjugated nanoparticles and PF127-based hydrophobically modified thermogels. In this article, we have briefly discussed the recent studies that have been conducted on various anti-cancer drugs using PF127 as nano-carrier modified with other copolymers and/or conjugated with magnetic nanoparticles. The key findings of these studies demonstrated that the modified form of PF127 can significantly increase the stability of incorporated hydrophobic drugs with enhanced in vitro cytotoxicity and cellular uptake of anti-cancer drugs. Moreover, the modified form of PF127 has also shown its therapeutic potentials as therodiagnostics in various types of tumors and cancers. Hence, it can be concluded that the modified form of PF127 exhibits significant therodiagnostic effects with increased tumor-specific delivery of anti-cancer drugs having minimal toxic effects as compared to PF127 alone and/or other copolymers.

Polymer-peptide delivery platforms: effect of oligopeptide orientation on polymer-based DNA delivery

The success of nonviral transfection using polymers hinges on efficient nuclear uptake of nucleic acid cargo and overcoming intra- and extracellular barriers. By incorporating PKKKRKV heptapeptide pendent groups as nuclear localization signals (NLS) on a polymer backbone, we demonstrate protein expression levels higher than those obtained from JetPEI and Lipofectamine 2000, the latter being notorious for coupling high transfection efficiency with cytotoxicity. The orientation of the NLS peptide grafts markedly affected transfection performance. Polymers with the sequence attached to the backbone from the valine residue achieved a level of nuclear translocation higher than the levels of those having the NLS groups attached in the opposite orientation. The differences in nuclear localization and DNA complexation strength between the two orientations correlated with a striking difference in protein expression, both in cell culture and in vivo. Polyplexes formed from these comb polymer structures exhibited transfection efficiencies superior to those of Lipofectamine 2000 but with greatly reduced toxicity. Moreover, these novel polymers, when administered by intramuscular ultrasound-mediated delivery, allowed a high level of reporter gene expression in mice, demonstrating their therapeutic promise in vivo.

Dual-degradable disulfide-containing PEI-Pluronic/DNA polyplexes: transfection efficiency and balancing protection and DNA release

Polymeric gene-delivery vectors to achieve lack of toxicity and a balance between protection and DNA release remains a formidable challenge. Incorporating intracellular environment-responsive degradable bonds is an appreciable step toward developing safer transfection agents. In this study, novel, dual-degradable polycation copolymers (Pluronic-diacrylate [PA]–polyethyleneimine [PEI]–SS) were synthesized through the addition of low molecular weight (800 Da) PEI cross-linked with SS (PEI-SS) to PA. Three PA-PEI-SS copolymers (PA-PEI-SS1, 2, and 3) with different PEI-SS to Pluronic molar ratios were investigated and found to strongly condense plasmid DNA into positively charged nanoparticles with an average particle size of approximately 200 nm and to possess higher stability against DNase I digestion and sodium heparin. Disulfide and ester bonds of the copolymers were susceptible to intracellular redox conditions. In vitro experiments demonstrated that the PA-PEI-SS copolymers had significantly lower cytotoxicity and higher transfection efficiency in both BGC-823 and 293T cell lines than the controls of degradable PEI-SS and nondegradable 25 kDa PEI. Transfection activity was influenced by the PEI-SS content in the polymers and PA-PEI-SS1 showed the highest efficiency of the three copolymers. These studies suggest that these dual-degradable copolymers could be used as potential biocompatible gene delivery carriers.

Pentablock copolymers of pluronic F127 and modified poly(2-dimethyl amino)ethyl methacrylate for internalization mechanism and gene transfection studies

Cationic polymers are one of the major nonviral gene delivery vectors investigated in the past decade. In this study, we synthesized several cationic copolymers using atom transfer radical polymerization (ATRP) for gene delivery vectors: pluronic F127-poly(dimethylaminoethyl methacrylate) (PF127-pDMAEMA), pluronic F127-poly (dimethylaminoethyl methacrylate-tert-butyl acrylate) (PF127-p(DMAEMA-tBA)), and pluronic F127-poly(dimethylaminoethyl methacrylate-acrylic acid) (PF127-p(DMAEMA-AA)). The copolymers showed high buffering capacity and efficiently complexed with plasmid deoxyribonucleic acid (pDNA) to form nanoparticles 80–180 nm in diameter and with positive zeta potentials. In the absence of 10% fetal bovine serum, PF127-p(DMAEMA-AA) showed the highest gene expression and the lowest cytotoxicity in 293T cells. After acrylic acid groups had been linked with a fluorescent dye, the confocal laser scanning microscopic image showed that PF127-p(DMAEMA-AA)/pDNA could efficiently enter the cells. Both clathrin-mediated and caveolae-mediated endocytosis mechanisms were involved. Our results showed that PF127-p(DMAEMA-AA) has great potential to be a gene delivery vector.

A Potential Application of Canaloplasty in Glaucoma Gene Therapy

Canaloplasty, a recently developed non-penetrating glaucoma surgical approach, may restore physiological outflow routes in primary open-angle glaucoma with less risk of severe postoperative complications than trabeculectomy. Since the inner wall of Schlemm's canal (SC) is directly in contact with the trabecular meshwork (TM) for 360 degrees and the catheter device used in canaloplasty allows viscoelastic to be injected into the entire length of SC, canaloplasty might also be used to perform SC/TM-targeted delivery of transgene vectors for glaucoma gene therapy. This hypothesized new method for transgene delivery may give the transgene access to the entire inner wall of SC and the whole juxtacanalicular region of the TM and allow the transgene to be expressed in both the TM and SC without affecting the cornea, iris and ciliary body. Further, this strategy might have a greater trabecular outflow resistance-decreasing effect than either the genetic or surgical approach alone.

Solubilization of parabens in aqueous Pluronic solutions: investigating the micellar growth and interaction as a function of paraben composition

The influence of methyl paraben (MP) and butyl paraben (BP) on the aggregation characteristics of Pluronics in an aqueous medium has been investigated by DLS, SANS, viscometry, and fluorescence measurement techniques. Parabens are extensively used as preservatives in cosmetic, pharmaceutical, and food products. In this paper, we show that their influence on the restructuring and growth of Pluronics micelles vary quite significantly with their aqueous solubility and with the composition of Pluronics. In the case of P105 and P104, MP reduces the sphere-to-rod transition temperature down to room temperature, but BP with significantly less aqueous solubility than MP suppresses such micellar transition and leads to the formation of micellar clusters due to the onset of intermicellar attractive interaction. In the case of more hydrophobic Pluronic P103, on the other hand, both MP and BP are able to induce rapid room temperature sphere-to-rod micellar growth, which is not observed in the presence of water structure making salts like NaCl and Na(3)PO(4). These observations have been attributed to modulation of growth and restructuring processes of the Pluronic micelles arising due to different locations of parabens within the micellar corona as determined by their aqueous solubility and the hydrophobicity of the Pluronics.

Bioreducible polyether-based pDNA ternary polyplexes: balancing particle stability and transfection efficiency

Polyplex particles formed with plasmid DNA (pDNA) and Pluronic P85-block-poly{N-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} (P85-b-P[Asp(DET)]) demonstrated highly effective transfection ability compared to PEG-based block cationomer, PEG-b-P[Asp(DET)]. Ternary polyplexes comprising PEG-b-P[Asp(DET)], poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)-b-P[Asp(DET)] (P(EPE)-b-P[Asp(DET)]) used as an analog of P85-b-P[Asp(DET)], and pDNA were prepared in this work aiming at maintaining adequate transfection efficiency while solving the stability issues of the P85-b-P[Asp(DET)] polyplexes. Furthermore, a bioreducible P(EPE)-SS-P[Asp(DET)] possessing a redox potential-sensitive disulfide linkage between the P(EPE) polymer and the cationic block was used as a substitute for P(EPE)-b-P[Asp(DET)] during ternary complex formation to investigate whether the transfection ability of the ternary polyplex system could be enhanced by triggered release of P(EPE) polymers from the polyplexes. The ternary complexes showed significant improvement in terms of stability against salt-induced aggregation compared to binary complexes, although the gene delivery ability dropped with the amount of PEG-b-P[Asp(DET)] used for complexation. By manipulating the difference in redox potential between the extracellular and intracellular environments, the reducible ternary complexes achieved higher transfection compared to the non-reducible polyplexes; moreover, the reducible polyplexes exhibited comparable stability to the non-reducible ones. These results suggest that reducible ternary complexes could provide satisfactory transfection efficiency without comprising the colloidal stability of the particles.

Mucus penetrating nanoparticles: biophysical tool and method of drug and gene delivery

A method that could provide more uniform and longer-lasting drug and gene delivery to mucosal surfaces holds the potential to greatly improve the effectiveness of prophylactic and therapeutic approaches for numerous diseases and conditions, including sexually transmitted infections, cystic fibrosis, chronic rhinosinusitis, inflammatory bowel disease, and glaucoma to name a few. However, the body's natural defenses, including adhesive, rapidly cleared mucus linings coating nearly all entry points to the body not covered by skin, has limited the effectiveness of drug and gene delivery by nanoscale delivery systems. This article discusses the recent development of the “mucuspenetrating particle” or “MPP” nanotechnology, and how it has been used to both enhance understanding of the nanoscale barrier properties of human mucus secretions, and to achieve more uniform and longer-lasting drug delivery to mucosal tissues following topical administration. Drug loaded MPPs possess non-adhesive coatings that allow them to rapidly penetrate mucus layers through openings in the mucus mesh at rates nearly as fast as they would penetrate pure water. Critically, MPPs allow enhanced drug and gene delivery to mucosal tissues without diminishing the protective function of mucus. Recent progress in the development of MPPs as a biophysical tool to probe the length-scale dependent rheological properties of mucosal secretions and as a method for drug and gene delivery is highlighted.

Poly(alkylene oxide) copolymers for nucleic acid delivery

The advancement of gene-based therapeutics to the clinic is limited by the ability to deliver physiologically relevant doses of nucleic acids to target tissues safely and effectively. Over the last couple of decades, researchers have successfully employed polymer and lipid based nanoassemblies to deliver nucleic acids for the treatment of a variety of diseases. Results of phase I/II clinical studies to evaluate the efficacy and biosafety of these gene delivery vehicles have been encouraging, which has promoted the design of more efficient and biocompatible systems. Research has focused on designing carriers to achieve biocompatibility, stability in the circulatory system, biodistribution to target the disease site, and intracellular delivery, all of which enhance the resulting therapeutic effect. The family of poly(alkylene oxide) (PAO) polymers includes random, block, and branched structures, among which the ABA type triblocks copolymers of ethylene oxide (EO) and propylene oxide (PO) (commercially known as Pluronic) have received the greatest consideration. In this Account, we highlight examples of polycation-PAO conjugates, liposome-PAO formulations, and PAO micelles for nucleic acid delivery. Among the various polymer design considerations, which include molecular weight of polymer, molecular weight of blocks, and length of blocks, the overall hydrophobic-lipophilic balance (HLB) is a critical parameter in defining the behavior of the polymer conjugates for gene delivery. We discuss the effects of varying this parameter in the context of improving gene delivery processes, such as serum stability and association with cell membranes. Other innovative macromolecular modifications discussed in this category include our work to enhance the serum stability and efficiency of lipoplexes using PAO graft copolymers, the development of a PAO gel-based carrier for sustained and stimuli responsive delivery, and the development of biodegradable PAO-based amphiphilic block copolymers.

High gene transfer by the osmotic polysorbitol-mediated transporter through the selective caveolae endocytic pathway

Cationic polymers have been the subject of intense research as nonviral gene delivery systems due to several advantages in comparison with viral vectors. However, the nonsimultaneous combination of high transfection efficiency and low cytotoxicity of nonviral vectors for gene delivery has long been an issue for scientists looking into ways to deliver genes into cells. Toward this goal, we designed, synthesized, and evaluated a safe and accelerated gene transfer system through polysorbitol-mediated transporter (PSMT) based on sorbitol diacrylate (SDA) and low molecular weight polyethylenimine (LMW PEI). The PSMT formed stable complexes with plasmid DNA in serum. The nano sizes and spherical shapes of PSMT/DNA complexes are not toxic, even at a high concentration of PSMT. The higher transfection efficiency of PSMT compared to PEI 25K was observed both in vitro, despite the existence of many hydroxyl groups, and in vivo. These improvements presumably stem from the osmotic property of polysorbitol and endosomal buffer capacity of PEI in PSMT. Most importantly, we confirmed that the selective cavaeolae endocytic pathway played a role in high transfection efficiency by osmotic PSMT-mediated gene delivery. We propose that PSMT is a promising nonviral carrier for the effective gene delivery to cancer cells via synergistic effects derived from rapid cellular uptake through the caveolae endocytic pathway and a high endosomal buffering capacity.