Impact of molecular rigidity on the gene delivery efficiency of core-shell tecto dendrimers

We report the construction of two types of core-shell tecto dendrimers (CSTDs) with different core rigidities to illustrate the impact of molecular rigidity on their gene delivery efficiency. Our study reveals that CSTDs designed with rigid cores enable promoted gene delivery, providing many possibilities for a wide range of gene delivery-associated biomedical applications.

Zinc(II)-Dipicolylamine Analogs Mediated PEI1.8k/pDNA Vector: Effect of Ligand Structure on the Gene Transport Process

Zinc ion complexes of dipicolylamine analogs, due to the strong synergistic effect between the Zn²⁺ complex of containing polypyridine derivatives and polycations in each key step of pDNA transport, have been used as the third component to mediate polyethyleneimine with molecular weight 1.8 kDa (PEI1.8k)/DNA gene delivery system. And the effects of different structural characteristics, such as the number of pyridinamine ligands, the hydrophilic-hydrophobicity of the adjacent groups, on the in vitro transfection performance of the ternary complex are systematically investigated. This ternary hybrid system provides an effective strategy to improve the gene delivery of cationic polymers.

Agmatine-grafted bioreducible poly(l-lysine) for gene delivery with low cytotoxicity and high efficiency

Bioreducible cationic polymers have gained considerable attention in gene delivery due to their low cytotoxicity and high efficiency. In the present work, we reported a cationic polymer, poly(disulfide-l-lysine)-g-agmatine (denoted as SSL-AG), and evaluated its ability to transfer pEGFP-ZNF580 plasmid (pZNF580) into human umbilical vein endothelial cells (HUVECs). This SSL-AG polymeric carrier efficiently condensed pZNF580 into positively charged particles (<200 nm) through electrostatic interaction. This carrier also exhibited excellent buffering capacity in the physiological environment, good pDNA protection against enzymatic degradation and rapid pDNA release in a highly reducing environment mainly because of the responsive cleavage of disulfide bonds in the polymer backbone. The hemolysis assay and in vitro cytotoxicity assay suggested that the SSL-AG carrier and corresponding gene complexes possessed both good hemocompatibility and great cell viability in HUVECs. The cellular uptake of the SSL-AG/Cy5-oligonucleotide group was 3.6 times that of the poly(l-lysine)/Cy5-oligonucleotide group, and its mean fluorescence intensity value was even higher than that of the PEI 25 kDa/Cy5-oligonucleotide group. Further, the intracellular trafficking results demonstrated that the SSL-AG/Cy5-oligonucleotide complexes exhibited a high nucleus co-localization rate (CLR) value (36.0 ± 2.8%, 3.4 times that of the poly (l-lysine)/Cy5-oligonucleotide group, 1.6 times that of the poly(disulfide-l-lysine)-g-butylenediamine/Cy5-oligonucleotide group) at 24 h, while the endo/lysosomal CLR value was relatively low. This suggested that SSL-AG successfully delivered plasmid into HUVECs with high cellular uptake, rapid endosomal escape and efficient nuclear accumulation owing to the structural advantages of the bioreducible and agmatine groups. In vitro transfection assay also verified the enhanced transfection efficiency in the SSL-AG/pZNF580 group. Furthermore, the results of CCK-8, cell migration and in vitro/vivo angiogenesis assays revealed that pZNF580 delivered by SSL-AG could effectively enhance the proliferation, migration and vascularization of HUVECs. In a word, the SSL-AG polymer has great potential as a safe and efficient gene carrier for gene therapy.

A “self-accelerating endosomal escape” siRNA delivery nanosystem for significantly suppressing hyperplasia via blocking the ERK2 pathway

Highly efficient ERK2 silencing in VSMCs via a “self-accelerating endosomal escape” siRNA transport nanosystem.

A new developing class of gene delivery: messenger RNA-based therapeutics

Gene therapy has long been held as having the potential to become a front line treatment for various genetic disorders. However, the direct delivery of nucleic acids to correct a genetic disorder has numerous limitations owing to the inability of naked nucleic acids (DNA and RNA) to traverse the cell membrane. Recently, messenger RNA (mRNA) based delivery has become a more attractive alternative to DNA due to the relatively easier transfection process, higher efficiency and safety profile. As with all gene therapies, the central challenge that remains is the efficient delivery of nucleic acids intracellularly. This review presents the recent progress in mRNA delivery, focusing on comparing the advantages and limitations of non-viral based delivery vectors.

miRNA delivery for skin wound healing

The wound healing has remained a worldwide challenge as one of significant public health problems. Pathological scars and chronic wounds caused by injury, aging or diabetes lead to impaired tissue repair and regeneration. Due to the unique biological wound environment, the wound healing is a highly complicated process, efficient and targeted treatments are still lacking. Hence, research-driven to discover more efficient therapeutics is a highly urgent demand. Recently, the research results have revealed that microRNA (miRNA) is a promising tool in therapeutic and diagnostic fields because miRNA is an essential regulator in cellular physiology and pathology. Therefore, new technologies for wound healing based on miRNA have been developed and miRNA delivery has become a significant research topic in the field of gene delivery.

From polyelectrolyte complexes to polyelectrolyte multilayers: Electrostatic assembly, nanostructure, dynamics, and functional properties

Polyelectrolyte complexes (PECs) are three-dimensional macromolecular structures formed by association of oppositely charged polyelectrolytes in solution. Polyelectrolyte multilayers (PEMs) can be considered a special case of PECs prepared by layer-by-layer (LbL) assembly that involves sequential deposition of molecular-thick polyelectrolyte layers with nanoscale control over the size, shape, composition and internal organization. Although many functional PEMs with novel physical and chemical characteristics have been developed, the current practical applications of PEMs are limited to those that require only a few bilayers and are relatively easy to prepare. The viability of such engineered materials can be realized only after overcoming the scientific and engineering challenges of understanding the kinetics and transport phenomena involved in the multilayer growth and the factors governing their final structure, composition, and response to external stimuli. There is a great need to model PEMs and to connect PEM behavior with the characteristics of the PEC counterparts to allow for prediction of performance and better design of multilayered materials. This review focuses on the relationship between PEMs and PECs. The constitutive interactions, the thermodynamics and kinetics of polyelectrolyte complexation and PEM formation, PEC phase behavior, PEM growth, the internal structure and stability in PEMs and PECs, and their response to external stimuli are presented. Knowledge of such interactions and behavior can guide rapid fabrication of PEMs and can aid their applications as nanocomposites, coatings, nano-sized reactors, capsules, drug delivery systems, and in electrochemical and sensing devices. The challenges and opportunities in future research directions are also discussed.

A pH-Responsive Detachable PEG Shielding Strategy for Gene Delivery System in Cancer Therapy

In this study, a pH-responsive detachable polyethylene glycol (PEG) shielding strategy was designed for gene delivery in cancer therapy. Polyethylenimine/DNA complex (PEI/DNA) was in situ shielded by aldehyde group-modified PEG derivatives. The aldehyde groups of PEG could react with the amino groups of PEI by Schiff base reaction. The Schiff base bond was stable in neutral pH but labile in slightly acidic pH, which made the PEG sheddable in tumors. PEG-coated nanoparticles (NPs) had distinct advantages compared to their mPEG counterpart, possessing decreased zeta potential, more compressed size, and enhanced stability. PEG/PEI/DNA NPs showed not only high tumor cell uptake and transfection efficiency in vitro but also efficient accumulation and gene expression in solid tumors in vivo. This pH-responsive detachable PEG shielding system has the potential to be applied to other polycationic nanoparticles that contain amino groups on their surfaces, which will have broad prospects in cancer therapy.

In Vivo Micro-CT Imaging of Human Mesenchymal Stem Cells Labeled with Gold-Poly-L-Lysine Nanocomplexes

Developing in vivo cell tracking is an important prerequisite for further development of cell-based therapy. So far, few computed tomography (CT) cell tracking studies have been described due to its notoriously low sensitivity and lack of efficient labeling protocols. We present a simple method to render human mesenchymal stem cells (hMSCs) sufficiently radiopaque by complexing 40 nm citrate-stabilized gold nanoparticles (AuNPs) with poly-L-lysine (PLL) and rhodamine B isothiocyanate (RITC). AuNP-PLL-RITC labeling did not affect cellular viability, proliferation, or downstream cell differentiation into adipocytes and osteocytes. Labeled hMSCs could be clearly visualized in vitro and in vivo with a micro-CT scanner, with a detection limit of approximately 2×104 cells/μl in vivo. Calculated HU values were 2.27 /pg of intracellular Au as measured with inductively coupled plasma mass spectrophotometry (ICP-MS), and were linear over a wide range of cell concentrations. This linear CT attenuation was observed for both naked AuNPs and those that were taken up by hMSCs, indicating that the number of labeled cells can be quantified similar to the use of radioactive or fluorine tracers. This approach for CT cell tracking may find applications in CT image-guided interventions and fluoroscopic procedures commonly used for the injection of cellular therapeutics.

Anticancer Drug Disulfiram for In Situ RAFT Polymerization: Controlled Polymerization, Multifacet Self-Assembly, and Efficient Drug Delivery

Here we report the synthesis of a well-defined amphiphilic conjugate, tetraethylthiuram disulfide (disulfiram, DS)-poly(ethylene glycol) methyl ether acrylate (DS-PEGMEA), and its multifacet self-assembly in aqueous solutions and application in DS drug delivery to melanoma cells. The DS-PEGMEA was synthesized via the reversible addition-fragmentation chain transfer (RAFT) polymerization utilizing DS, a 90 year old anticancer drug, as a precursor to generate RAFT agent in situ. Results demonstrate that the in situ formed RAFT can effectively control the polymerization of PEGMEA. Depending on the concentration in aqueous solution, the amphiphilic DS-PEGMEA conjugate can self-assemble to form layered, toroidal, hairy, or spherical nanostructures, respectively. Moreover, DS drug can be further encapsulated by DS-PEGMEA to formulate core-shell structured DS/DS-PEGMEA nanoparticles mediating the apoptosis of melanoma cells (A375) while inducing minimal cytotoxicity to normal (hADSC and NIH fibroblast) cells. Both DS and PEGMEA are approved by the American Food and Drug Administration (FDA); therefore, the DS-PEGMEA has great potential for application in clinical drug delivery to melanoma.

Surface Engineered Protein Nanoparticles With Hyaluronic Acid Based Multilayers For Targeted Delivery Of Anticancer Agents

Layer-by-layer (LbL) technique was employed to modify the surface of doxorubicin (Dox)-loaded bovine serum albumin (BSA) nanoparticles using hyaluronic acid (HA) to enable targeted delivery to overexpressed CD44 receptors in metastatic breast cancer cells. LbL technique offers a versatile approach to modify the surface of colloidal nanoparticles without any covalent modification. Dox-loaded BSA (Dox Ab) nanoparticles optimized for their size, zeta potential, and drug encapsulation efficiency were prepared by modified desolvation technique. The cellular uptake and cytotoxicity of the LbL coated Dox Ab nanoparticles were analyzed in CD44 overexpressing breast cancer cell line MDA-MB-231. Nanoparticles with HA as the final layer (Dox Ab HA) showed maximum cellular uptake in MDA-MB-231 cells owing to the CD44 receptor-mediated endocytosis and hence, exhibited more cytotoxicity as compared to free Dox. Further, luciferase-transfected MDA-MB-231 cells were used to induce tumor in BALB/c female nude mice to enable whole body tumor imaging. The mice were imaged before and after Dox treatment to visualize the tumor growth. The in vivo biodistribution of Dox Ab HA nanoparticles in nude mice showed maximum accumulation in tumor, and importantly, better tumor reduction in comparison with free Dox, thus paving the way for improved drug delivery into tumors.

PLL/PAE/DNA ternary complexes with enhanced endosomal escape ability for efficient and safe gene transfection

High gene transfection efficiency is achieved by a simple yet versatile PAE oligomer incorporation strategy.

Biocompatible polymer-Peptide hybrid-based DNA nanoparticles for gene delivery

Currently, research on polymers to be used as gene delivery systems is one of the most important directions in both polymer science and biomedicine. In this report, we describe a five-step procedure to synthesize a novel polymer-peptide hybrid system for gene transfection. The block copolymer based on the biocompatible polymer poly(2-methyl-2-oxazoline) (PMOXA) was combined with the biocleavable peptide block poly(aspartic acid) (PASP) and finally modified with diethylenetriamine (DET). PMOXA-b-PASP(DET) was produced in high yield and characterized by (1)H NMR and FT-IR. Our biopolymer complexed plasmid DNA (pDNA) efficiently, and highly uniform nanoparticles with a slightly negative zeta potential were produced. The polymer-peptide hybrid system was able to efficiently transfect HEK293 and HeLa cells with GFP pDNA in vitro. Unlike the commonly used polymer, 25 kDa branched poly(ethylenimine), our biopolymer had no adverse effects on cell growth and viability. In summary, the present work provides valuable information for the design of new polymer-peptide hybrid-based gene delivery systems with biocompatible and biodegradable properties.

Biophysical characterization and molecular docking studies of imidazolium based polyelectrolytes-DNA complexes: role of hydrophobicity

Nonviral gene delivery vectors are acquiring greater attention in the field of gene therapy by replacing the biological viral vectors. DNA-cationic polymer complexes are one of the most promising systems to find application in gene therapy. Hence, a complete insight of their biophysical characterization and binding energy profile is important in understanding the mechanism involved in nonviral gene therapy. In this investigation, the interaction between calf thymus DNA (ctDNA) and imidazolium-based poly(ionic liquids) (PILs) also known as polyelectrolytes with three different alkyl side chains (ethyl, butyl, and hexyl) in physiological conditions using various spectroscopic experiments with constant DNA concentration and varying polyelectrolyte concentrations is reported. UV-visible absorption, fluorescence quenching studies, gel electrophoresis, circular dichroism (CD), and Fourier transform infrared spectroscopy (FTIR) have confirmed the binding of polyelectrolytes with DNA. UV-vis absorption measurements and fluorescence quenching revealed that the binding between DNA and the polyelectrolyte is dominated by electrostatic interactions. Additionally, CD and FTIR results indicated that the DNA retained its B-form with minor perturbation in the phosphate backbone without significant change in the conformation of its base pairs. Preference for alkyl side chains (K(PIL-Ethyl Br) < K(PIL-Butyl Br) < K(PIL-Hexyl Br)) toward efficient binding between the polyelectrolyte and DNA was inferred from the binding and quenching constants calculated from the absorption and emission spectra, respectively. Further, in silico molecular docking studies not only validated the observed binding trend but also provided insight into the binding mode of the polyelectrolyte-DNA complex.

Reversible PEGylation and Schiff-base linked imidazole modification of polylysine for high-performance gene delivery

In the designed polylysine based catiomer the reversible PEGylation was introduced forin vivocirculation and to augment the cellular internalization, while the Schiff-base linked imidazole to accelerate the endosomal escape and facilitate intracellular DNA unpacking and release.

Structural impact of graft and block copolymers based on poly(N-vinylpyrrolidone) and poly(2-dimethylaminoethyl methacrylate) in gene delivery

The characteristics of graft and block copolymers based on PVP and PDMAEMA in pDNA compaction, cytotoxicity, transfection efficiency, internalization and intracellular distribution were systematically investigated.

Suppression of VEGF by reversible-PEGylated histidylated polylysine in cancer therapy

A reversible-PEGylated polylysine is designed and developed for efficient delivery of siRNA. In this unique structure, the ε-amino groups of disulfide linked poly(ethylene glycol) (PEG) and polylysine (mPEG-SS-PLL) are partially replaced by histidine groups, in order to develop the histidylated reversible-PEGylated polylysine (mPEG-SS-PLH), for enhanced endosome escape ability. The transfection efficacy of mPEG-SS-PLH is found to closely correlate with histidine substitution. Its maximum transfection efficiencies are determined, respectively, to be 75%, 42%, and 24%, against 293T, MCF-7, and PC-3 cells. These data indicate that the transfection efficiencies can equal or even outweigh PEI-25k in the corresponding cells (80%, 38.5%, and 20%). The in vivo circulation and biodistribution of the polyplexes are monitored by fluorescent imaging. The in vivo gene transfection is carried out by intravenous injection of pEGFP to BALB/c mice using the xenograft models. The in vivo experimental results show effective inhibition of tumor growth by mPEG-SS-PLH/siRNA-VEGF, indicating its high potential for clinical applications.

Role of polymeric endosomolytic agents in gene transfection: a comparative study of poly(L-lysine) grafted with monomeric L-histidine analogue and poly(L-histidine)

Endosomal entrapment is one of the main barriers that must be overcome for efficient gene expression along with cell internalization, DNA release, and nuclear import. Introducing pH-sensitive ionizable groups into the polycationic polymers to increase gene transfer efficiency has proven to be a useful method; however, a comparative study of introducing equal numbers of ionizable groups in both polymer and monomer forms, has not been reported. In this study, we prepared two types of histidine-grafted poly(L-lysine) (PLL), a stacking form of poly(L-histidine) (PLL-g-PHis) and a mono-L-histidine (PLL-g-mHis) with the same number of imidazole groups. These two types of histidine-grafted PLL, PLL-g-PHis and PLL-g-mHis, showed profound differences in hemolytic activity, cellular uptake, internalization, and transfection efficiency. Cy3-labeled PLL-g-PHis showed strong fluorescence in the nucleus after internalization, and high hemolytic activity upon pH changes was also observed from PLL-g-PHis. The arrangement of imidazole groups from PHis also provided higher gene expression than mHis due to its ability to escape the endosome. mHis or PHis grafting reduced the cytotoxicity of PLL and changed the rate of cellular uptake by changing the quantity of free ε-amines available for gene condensation. The subcellular localization of PLL-g-PHis/pDNA measured by YOYO1-pDNA intensity was highest inside the nucleus, while the lysotracker, which stains the acidic compartments was lowest among these polymers. Thus, the polymeric histidine arrangement demonstrate the ability to escape the endosome and trigger rapid release of polyplexes into the cytosol, resulting in a greater amount of pDNA available for translocation to the nucleus and enhanced gene expression.

One-step sonochemical preparation of redox-responsive nanocapsules for glutathione mediated RNA release

A simple and reproducible sonochemical method is described to achieve redox-responsive nanocapsules based on intracellular glutathione levels for enhanced and sustained RNA delivery.

Evaluation of the effects of amphiphilic oligomers in PEI based ternary complexes on the improvement of pDNA delivery

(HEMA-b-NIPAM) was incorporated into PEI/P(HEMA-b-NIPAM)/pDNA ternary complexes through non-electrostatic assembly to enhance the interaction between complexes and cellular/endocellular membranes to improve gene transfection.

Gene delivery of PEI incorporating with functional block copolymer via non-covalent assembly strategy

A novel functional diblock polymer P(PEGMA-b-MAH) is prepared and incorporated to improve the gene delivery efficiency of poly(ethyleneimine) PEI via non-covalent assembly strategy. First, P(PEGMA-b-MAH) is prepared from l-methacrylamidohistidine methyl ester (MAH) by reversible addition fragmentation chain transfer polymerization, with poly[poly(ethylene glycol) methyl ether methacrylate] (P(PEGMA)) as the macroinitiator. Then P(PEGMA-b-MAH) is assembled with plasmid DNA (pDNA) and PEI (M(w)=10kDa) to form PEI/P(PEGMA-b-MAH)/pDNA ternary complexes. The agarose gel retardation assay shows that the presence of P(PEGMA-b-MAH) does not interfere with DNA condensation by the PEI. Dynamic light scattering tests show that PEI/P(PEGMA-b-MAH)/pDNA ternary complexes have excellent serum stability. In vitro transfection indicates that, compared to the P(PEGMA-b-MAH) free PEI-25k/pDNA binary complexes, PEI-10k/P(PEGMA-b-MAH)/pDNA ternary complexes have lower cytotoxicity and higher gene transfection efficiency, especially under serum conditions. The ternary complexes proposed here can inspire a new strategy for the development of gene and drug delivery vectors.

Cationic polymers and their therapeutic potential

The last decade has witnessed enormous research focused on cationic polymers. Cationic polymers are the subject of intense research as non-viral gene delivery systems, due to their flexible properties, facile synthesis, robustness and proven gene delivery efficiency. Here, we review the most recent scientific advances in cationic polymers and their derivatives not only for gene delivery purposes but also for various alternative therapeutic applications. An overview of the synthesis and preparation of cationic polymers is provided along with their inherent bioactive and intrinsic therapeutic potential. In addition, cationic polymer based biomedical materials are covered. Major progress in the fields of drug and gene delivery as well as tissue engineering applications is summarized in the present review.