Functionalized Nonionic Dextran Backbones by Atom Transfer Radical Polymerization for Efficient Gene Delivery

PAMAM-Functionalized Cellulose Nanocrystals with Needle-Like Morphology for Effective Cancer Treatment

Gene therapy is used to correct or compensate for diseases caused by gene defects and abnormalities. Improving the transfection efficiency and reducing the toxicity of gene carriers are the keys to gene therapy. Similar to a typical cationic gene carrier—polyethylenimine (PEI, 25 kDa)—the polyamidoamine (PAMAM) dendrimer also has a large number of amino groups. These amino groups can be complexed with nucleic acids after protonation under physiological conditions. However, the concentrated positive charge can cause undesirable cytotoxicity. Cellulose nanocrystals (CNCs) have good biocompatibility and unique needle-like morphology, and have been proven to be efficiently taken up by cells. In this article, three-dimensional spherical PMAMA dendrimers are conjugated onto the surface of CNCs to obtain a kind of needle-like cationic carrier (CNC-PAMAM). PAMAM dendrimers act as anchors to bind the plasmid DNAs (pDNA) to the surface of the CNC. The prepared CNC-based carrier showed high transfection efficiency and low toxicity. The CNC-PAMAM can effectively deliver the suicide gene to the tumor site, enabling the suicide gene/prodrug system (cytosine deaminase/5-fluorocytosine (CD/5-FC)) to play an effective anti-tumor role in vivo. This research demonstrates that the functionalization of CNCs with PAMAM dendrimers is an effective method for developing novel gene delivery systems.

Polymeric vehicles for nucleic acid delivery

Polymeric vehicles are versatile tools for therapeutic gene delivery. Many polymers-when assembled with nucleic acids into vehicles-can protect the cargo from degradation and clearance in vivo, and facilitate its transport into intracellular compartments. Design options in polymer synthesis yield a comprehensive range of molecules and resulting vehicle formulations. These properties can be manipulated to achieve stronger association with nucleic acid cargo and cells, improved endosomal escape, or sustained delivery depending on the application. Here, we describe current approaches for polymer use and related strategies for gene delivery in preclinical and clinical applications. Polymer vehicles delivering genetic material have already achieved significant therapeutic endpoints in vitro and in animal models. From our perspective, with preclincal assays that better mimic the in vivo environment, improved strategies for target specificity, and scalable techniques for polymer synthesis, the impact of this therapeutic approach will continue to expand.

Biodegradable Polymers for Gene-Delivery Applications

Gene-based therapies have emerged as a new modality for combating a myriad of currently incurable diseases. However, the fragile nature of gene therapeutics has significantly hampered their biomedical applications. Correspondingly, the development of gene-delivery vectors is of critical importance for gene-based therapies. To date, a variety of gene-delivery vectors have been created and utilized for gene delivery. In general, they can be categorized into viral- and non-viral vectors. Due to safety issues associated with viral vectors, non-viral vectors have recently attracted much more research focus. Of these non-viral vectors, polymeric vectors, which have been preferred due to their low immunogenicity, ease of production, controlled chemical composition and high chemical versatility, have constituted an ideal alternative to viral vectors. In particular, biodegradable polymers, which possess advantageous biocompatibility and biosafety, have been considered to have great potential in clinical applications. In this context, the aim of this review is to introduce the recent development and progress of biodegradable polymers for gene delivery applications, especially for their chemical structure design, gene delivery capacity and additional biological functions. Accordingly, we first define and categorize biodegradable polymers, followed by describing their corresponding degradation mechanisms. Various types of biodegradable polymers resulting from natural and synthetic polymers will be introduced and their applications in gene delivery will be examined. Finally, a future perspective regarding the development of biodegradable polymer vectors will be given.

Ligand targeting and peptide functionalized polymers as non-viral carriers for gene therapy

Ligand targeting and peptide functionalized polymers serve as gene carriers for efficient gene delivery.

Polymeric siRNA gene delivery - transfection efficiency versus cytotoxicity

Within the field of gene therapy, there is a considerable need for the development of non-viral vectors that are able to compete with the efficiency obtained by viral vectors, while maintaining a good toxicity profile and not inducing an immune response within the body. While there have been many reports of possible polymeric delivery systems, few of these systems have been successful in the clinical setting due to toxicity, systemic instability or gene regulation inefficiency, predominantly due to poor endosomal escape and cytoplasmic release. The objective of this review is to provide an overview of previously published polymeric non-coding RNA and, to a lesser degree, oligo-DNA delivery systems with emphasis on their positive and negative attributes, in order to provide insight in the numerous hurdles that still limit the success of gene therapy.

Preparation and drug delivery of dextran-drug complex

Dextran as a drug carrier for inhibiting cancer cells effectively reduces the toxic and side effects of the drug in the biological body. Targeting improves the concentration of active substance around the target tissue, which reduces damage to other heavy organs and other normal tissues. Dextran will be a potential carrier for the delivery of antitumor drugs in the future, which provides the possibility of slow-release chemotherapy and targeted drug delivery. Herein, the preparation and drug delivery of dextran-drug complex were summarized and discussed in detail.

A Polycationic Brush Mediated Co-Delivery of Doxorubicin and Gene for Combination Therapy

The combination of drug and gene strategies for cancer therapy, has exhibited greater effectiveness than drug or gene therapy alone. In this paper, a coil-comb shaped polycationic brush was used as a multifunctional carrier for co-delivery of drug and gene. The side chains of the comb block of the brush were composed of cyclodextrin (CD)-containing cationic star polymers, with a super-high density of positive charge. Doxorubicin (DOX) could be loaded into the cavity of CD polymers to form DOX-loaded nanoparticles (DOX-NPs) and the p53 gene could be subsequently condensed by DOX-NPs. The obtained DOX-NPs/pDNA complexes were less than 150 nm in size, and so could transport DOX and the gene into the same cell. The complexes performed well with regards to their transfection efficiency on MCF-7 cancer cells. As a result, enhanced cell growth inhibition, with decreased DOX dosage was achieved due to the synergistic effect of co-delivery of DOX and the p53 gene. This finding provides an efficient approach for the development of a co-delivery system in combination therapy.

Glycopolymers/PEI complexes as serum-tolerant vectors for enhanced gene delivery to hepatocytes

Serum stability is a crucial factor for ideal polymeric gene vectors. In this work, a series of serum-tolerant and low-toxicity glycopolymers/poly(ethyleneimine) (PEI) complexes were designed for gene delivery. Atomic transfer radical polymerization (ATRP) was used to synthesize the comb-shaped random copolymers dextran-g-poly(2-dimethylaminoethyl methacrylate-co-2-lactobionamidoethyl methacrylate) (DDrL). Then DDrLs/PEI were investigated for their use as plasmid DNA (pDNA) vectors, which can completely condense the pDNA into nanoparticles. The DDrLs/PEI/pDNA complexes in serum-containing media showed better stability than PEI/pDNA complexes. in vitro gene transfection studies showed that DDrLs/PEI exhibited a remarkable transfection efficiency enhancement in the presence of serum compared to that in serum-free conditions. Moreover, the transfection level of DDrLs/PEI were two orders of magnitude higher than that of PEI alone in the presence of 30% serum. DDrLs/PEI complexes with galactose enhanced pDNA delivery to hepatocytes, with higher protein expression in ASGPr-presenting HepG2 than in HeLa cells, which lack the receptor. All of the DDrLs/PEI/pDNA complexes had lower cytotoxicity than PEI/pDNA.

pH-Responsive Natural Polymeric Gene Delivery Shielding System Based on Dynamic Covalent Chemistry

A novel pH-responsive system based on aldehyde-bearing dextran derivatives (ODEX or FDEX) was designed to use as gene carrier shielding. Through pH sensitive Schiff base bonds between amino groups of PEI (in PEI/DNA polyplex) and aldehyde groups of dextran derivatives, PEI/DNA polyplex could be shielded and further condensed to obtain an effectively decreasing ζ-potential with smaller size. Schiff base bonds were pH-responsive, which were relatively stable in neutral environment but were deformed in slightly acidic and acidic environments. Through use of this characteristic, the PEI/DNA polyplex was effectively shielded during circulation in the body, and upon arrival at the tumor, the slightly acid pH triggered the breaking of Schiff base bonds to expose the positive PEI/DNA polyplex, which further interacted with tumor cell membranes, achieving efficient gene expression. Use of such characteristics could effectively address the high transfection efficiency versus stability dilemma of gene carriers. FDEX/PEI/DNA nanoparticles not only mediate higher cellular uptake and transfection efficiency in vitro but also effectively accumulate in tumors with gene expression in vivo higher than that of the ODEX analogues. As a result, this pH-responsive system is a promising strategy for cancer therapy.

Well-Defined Cationic N-[3-(Dimethylamino)propyl]methacrylamide Hydrochloride-Based (Co)polymers for siRNA Delivery

Cationic glycopolymers have shown to be excellent candidates for the fabrication of gene delivery devices due to their ability to electrostatically interact with negatively charged nucleic acids and the carbohydrate residues ensure enhanced stability and low toxicity of the polyplexes. The ability to engineer the polymers for optimized compositions, molecular weights, and architectures is critical in the design of effective gene delivery vehicles. Therefore, in this study, the aqueous reversible addition-fragmentation chain transfer polymerization (RAFT) was used to synthesize well-defined cationic glycopolymers with various cationic segments. For the preparation of cationic parts, N-[3-(dimethylamino)propyl]methacrylamide hydrochloride (DMAPMA·HCl), water-soluble methacrylamide monomer containing tertiary amine, was polymerized to produce DMAPMA·HCl homopolymer, which was then used as macroCTA in the block copolymerization with two other methacrylamide monomers containing different pendant groups, namely, 2-aminoethyl methacrylamide hydrochloride (AEMA) (with primary amine) and N-(3-aminopropyl) morpholine methacrylamide (MPMA) (with morpholine ring). In addition, statistical copolymers of DMAPMA.HCl with either AEMA or MPMA were also synthesized. All resulting cationic polymers were utilized as macroCTA for the RAFT copolymerization with 2-lactobionamidoethyl methacrylamide (LAEMA), which consists of the pendent galactose residues to achieve DMAPMA·HCl-based glycopolymers. From the in vitro cytotoxicity study, the cationic glycopolymers showed better cell viabilities than the corresponding cationic homopolymers. Furthermore, complexation of the cationic polymers with siRNA, cellular uptake of the resulting polyplexes, and gene knockdown efficiencies were evaluated. All cationic polymers/glycopolymers demonstrated good complexation ability with siRNA at low weight ratios. Among these cationic polymer-siRNA polyplexes, the polyplexes prepared from the two glycopolymers, P(DMAPMA₆₅-b-LAEMA₁₅) and P[(DMAPMA₆₅-b-MPMA₆₃)-b-LAEMA₁₆], showed outstanding results in the cellular uptake, high EGFR knockdown, and low post-transfection toxicity, suggesting the great potential in siRNA delivery of these novel glycopolymers.

Cationic starch/pDNA nanocomplexes assembly and their nanostructure changes on gene transfection efficiency

This study aims at developing biocompatible starch based gene carriers with good gene delivery and transfection efficacy. By controlling the molecular weight and aggregation behavior of spermine modified cationic starch (CS) molecules, nanocomplexes spontaneously formed through electrostatic interaction using CS and plasmid pAcGFP1-C1 (pDNA) displaying different structural changes (particle size, zeta potential, shape, compactness) response to the simulated intracellular pH variation. Results indicated that CS2 with weight average molecular weight (Mw) of 6.337 × 10⁴ g/mol displayed relatively higher transfection efficacy (~30%) in HepG2 cells than others and revealed significantly low cytotoxicity. By simulating the intracellular pH variation, Dynamic Light Scattering (DLS) and Small Angle X-ray Scattering (SAXS) results demonstrated that CS2 could bind to pDNA tightly and form nanocomplexes with smaller and compact internal aggregate structure at acidic conditions, which facilitated the effective pDNA protection under endosome pH change, while larger and loose internal aggregate structure at physiological pH which promoted the disintegration of CS2/pDNA nanocomplexes. Therefore, CS with suitable Mw of around 6.0 × 10⁴ g/mol represents a potential gene carrier for gene delivery. This study also demonstrated that controlling the internal nanostructure change of polymer/gene nanocomplexes could provide guidance in designing effective starch based gene carriers.

Hemostatic porous sponges of cross-linked hyaluronic acid/cationized dextran by one self-foaming process

Effective hemostatic materials are very important for treating trauma cases. Natural polysaccharides have been particularly appealing in the development of new hemostatic materials due to their unique functions in human bodies. In this work, different polysaccharide-based hemostatic porous sponges (SHDP or SHDQ) of cross-linked hyaluronic acid (HA)/cationized dextran were readily prepared by the self-foaming process of HA and poly((2-dimethyl amino)-ethyl methacrylate)-grafted dextran (Dex-PDM) or partially-quaternized Dex-PDM in the presence of sodium trimetaphosphate crosslinkers. SHDP and SHDQ sponges were investigated in terms of liquid-absorption ability, hemolysis, whole-blood clotting and hemostatic activity in hemorrhaging-liver models. Compared with HA/Dex-PDM sponges (HDP) without chemical cross-linking, SHDP and SHDQ sponges displayed higher porosity (>70.0% vs. 48.9%) and swelling ratios (>1000% vs. 520%). Meanwhile, hemolysis assay revealed the good blood compatibility of SHDP and SHDQ with low hemolysis ratio (below 0.5%). Furthermore, in vitro and in vivo hemostatic assay showed that SHDQ possessed better hemostatic properties than SHDP, owing to the higher cationic charges of partially-quaternized Dex-QPDM than Dex-PDM. The present study demonstrated that the self-foaming process of HA/Dex-PDM under a 'green' condition is an effective means to produce new hemostatic materials.

Versatile Functionalization of Polysaccharides via Polymer Grafts: From Design to Biomedical Applications

Because of their biocompatibility, biodegradability, and unique bioactive properties, polysaccharides have been recognized and directly applied as excellent candidates for various biomedical applications. In order to introduce more functionalities onto polysaccharides, various modification methods were applied to improve the physical-chemical and biochemical properties. Grafting polysaccharides with functional polymers with limited reaction sites maximizes the structural integrity. To the best of our knowledge, great efforts have been made by scientists across the world, including our research group, to explore different strategies for the synthesis and design of controllable polymer-grafted polysaccharides. By the application of some reasonable strategies, a series of polymer-grafted polysaccharides with satisfactory biocharacteristics were obtained. The first strategy involves facile modification of polysaccharides with living radical polymerization (LRP). Functionalized polysaccharides with diverse grafts can be flexibly and effectively achieved. The introduced grafts include cationic components for nuclei acid delivery, PEGylated and zwitterionic moieties for shielding effects, and functional species for bioimaging applications as well as bioresponsive drug release applications. The second synthetic model refers to biodegradable polymer-grafted polysaccharides prepared by ring-opening polymerization (ROP). Inspired by pathways to introduce initiation sites onto polysaccharides, the use of amine-functionalized polysaccharides was explored in-depth to trigger ROP of amino acids. A series of poly(amino acid)-grafted polysaccharides with advanced structures (including linear, star-shaped, and comb-shaped copolymers) were developed to study and optimize the structural effects. In addition, biodegradable polyester-grafted polysaccharides were prepared and utilized for drug delivery. Another emerging strategy was to design polysaccharide-based assemblies with supramolecular structures. A variety of assembly techniques using non-covalent interactions were established to construct different types of polysaccharide-based assemblies with various bioapplications. On the basis of these strategies, polymer-grafted polysaccharides with controllable functions were reported to be well-suited for different kinds of biomedical applications. The exciting results were obtained from both in vitro and in vivo models. Viewing the rapid growth of this field, the present Account will update the concepts, trends, perspectives, and applications of functionalized polysaccharides, guiding and inspiring researchers to explore new polysaccharide-based systems for wider applications.

Dually sensitive dextran-based micelles for methotrexate delivery

Temperature and pH-sensitive micelles prepared from dextran grafted with poly(N-isopropylacrylamide) (PNIPAAm)/polyethylene glycol methyl ether (PEGMA) with/without 2-aminoethylmethacrylate (2-AEM) were evaluated as methotrexate delivery systems.

A Facile Strategy to Prepare Hyperbranched Hydroxyl-Rich Polycations for Effective Gene Therapy

For effective gene therapy, nonviral gene carriers with low toxicity and high transfection efficiency are of much importance. In this work, we developed a facile strategy to prepare hyperbranched hydroxyl-rich polycations (denoted by TE) by the one-pot method involving ring-opening reactions between two commonly used reagents, ethylenediamine (ED) with two amino groups and 1,3,5-triglycidyl isocyanurate (TGIC) with three epoxy groups. The hyperbranched TEs with different molecular weights were investigated on their DNA condensation ability, protein absorption property, biocompatibility, transfection efficiency, and in vivo cancer therapy and toxicity. TE exhibited low cytotoxicity and protein absorption property due to the plentiful hydroxyl groups. The optimal transfection efficiency of TE was significantly higher than that of the gold standard polycationic gene carrier branched polyethylenimine (PEI, 25 kDa). Furthermore, TE was applied for in vivo tumor inhibition by the delivery of antioncogene p53, which showed good antitumor efficiency with low adverse effects. The present work provides a new concept for the facile preparation of hyperbranched hydroxyl-rich polycationic carriers with good transfection performances.

Controllable Heparin-Based Comb Copolymers and Their Self-assembled Nanoparticles for Gene Delivery

Polysaccharide-based copolymers have attracted much attention due to their effective performances. Heparin, as a kind of polysaccharide with high negative charge densities, has attracted much attention in biomedical fields. In this work, we report a flexible way to adjust the solubility of heparin from water to oil via the introduction of tetrabutylammonium groups for further functionalization. A range of heparin-based comb copolymers with poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMEMA), poly(dimethylaminoethyl methacrylate) (PDMAEMA), or PPEGMEMA-b-PDMAEMA side chains were readily synthesized in a MeOH/dimethylsulfoxide mixture via atom-transfer radical polymerization. The heparin-based polymer nanoparticles involving cationic PDMAEMA were produced due to the electrostatic interaction between the negatively charged heparin backbone and PDMAEMA grafts. Then the pDNA condensation ability, cytotoxicity, and gene transfection efficiency of the nanoparticles were characterized in comparison with the reported gene vectors. The nanoparticles were proved to be effective gene vectors with low cytotoxicity and high transfection efficiency. This study demonstrates that by adjusting the solubility of heparin, polymer graft functionalization of heparin can be readily realized for wider applications.

The synthesis and comparison of chondroitin sulfate-modified PDMAEMA with chondroitin sulfate-modified PEI as a potential gene delivery vector

CS-PDMAEMA obtained by reacting HS-PDMAEMA with CSMA via Michael addition, shows lower cytotoxicity and better transfection efficiency than PDMAEMA. The transfection efficiency is higher in 3T3 cells than in U87 cells owing to higher expression of ASGP-R.

Stimulation of apoptotic pathways in liver cancer cells: An alternative perspective on the biocompatibility and the utility of biomedical glasses

A host of research opportunities with innumerable clinical applications are open to biomedical glasses if one considers their potential as therapeutic inorganic ion delivery systems. Generally, applications have been limited to repair and regeneration of hard tissues while compositions are largely constrained to the original bioactive glass developed in the 1960s. However, in oncology applications the therapeutic paradigm shifts from repair to targeted destruction. With this in mind, the composition–structure–property–function relationships of vanadium-containing zinc-silicate glasses (0.51SiO2–0.29Na2O–(0.20- X)ZnO– XV2O5, 0 ≤  X ≤ 0.09) were characterized in order to determine their potential as therapeutic inorganic ion delivery systems. Increased V2O5 mole fraction resulted in a linear decrease in density and glass transition temperature (Tg). 29Si MAS NMR peak maxima shifted upfield while 51V MAS NMR peak maxima were independent of V2O5 content and overlapped well with the spectra NaVO3. Increased V2O5 mole fraction caused ion release to increase. When human liver cancer cells, HepG2, were exposed to these ions they demonstrated a concentration-dependent cytotoxic response, mediated by apoptosis. This work demonstrates that the zinc-silicate system studied herein is capable of delivering therapeutic inorganic ions at concentrations that induce apoptotic cell death and provide a simple means to control therapeutic inorganic ion delivery.

Redox-responsive polycation-functionalized cotton cellulose nanocrystals for effective cancer treatment

Carbon nanotubes have excellent penetrability and encapsulation efficiency in the fields of drug and gene delivery. Because of their excellent physicochemical properties, biocompatible rodlike cellulose nanocrystals (CNCs) were reportedly expected to replace carbon nanotubes. In this work, CNCs from natural cotton wool were functionalized with disulfide bond-linked poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes for effective biomedical applications. A range of CNC-graft-PDMAEMA vectors (termed as CNC-SS-PDs) with various molecular weights of PDMAEMA were synthesized. Under reducible conditions, PDMAEMA chains can be easily cleaved from CNCs. The gene condensation ability, reduction sensitivity, cytotoxicity, gene transfection, and in vivo antitumor activities of CNC-SS-PDs were investigated in detail. The CNC-SS-PDs exhibited good transfection efficiencies and low cytotoxicities. The needlelike shape of CNCs had an important effect on enhancing transfection efficiency. The antitumor effect of CNC-SS-PDs was evaluated by a suicide gene/prodrug system (cytosine deaminase/5-fluorocytosine, CD/5-FC) in vitro and in vivo. This research demonstrates that the functionalization of CNCs with redox-responsive polycations is an effective method for developing novel gene delivery systems.

PGMA-based starlike polycations with flanking phenylboronic acid groups for highly efficient multifunctional gene delivery systems

A simple strategy to prepare starlike PGMA-based vectors with phenylboronic acid groups was proposed for multifunctional gene delivery systems.

A general strategy to prepare different types of polysaccharide-graft-poly(aspartic acid) as degradable gene carriers

Owing to their unique properties such as low cytotoxicity and excellent biocompatibility, poly(aspartic acid) (PAsp) and polysaccharides are good candidates for the development of new biomaterials. In order to construct better gene delivery systems by combining polysaccharides with PAsp, in this work, a general strategy is described for preparing series of polysaccharide-graft-PAsp (including cyclodextrin (CD), dextran (Dex) and chitosan (CS)) gene vectors. Such different polysaccharide-based vectors are compared systematically through a series of experiments including degradability, pDNA condensation capability, cytotoxicity and gene transfection ability. They possess good degradability, which would benefit the release of pDNA from the complexes. They exhibit significantly lower cytotoxicity than the control 'gold-standard' polyethylenimine (PEI, ∼25kDa). More importantly, the gene transfection efficiency of Dex- and CS-based vectors is 12-14-fold higher than CD-based ones. This present study indicates that properly grafting degradable PAsp from polysaccharide backbones is an effective means of producing a new class of degradable biomaterials.

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.

Polycation-b-polyzwitterion copolymer grafted luminescent carbon dots as a multifunctional platform for serum-resistant gene delivery and bioimaging

Nanomaterials that integrate functions of imaging and gene delivery have been of great interest due to their potential use in simultaneous diagnosis and therapy. Herein, polycation-b-polysulfobetaine block copolymer, poly[2-(dimethylamino) ethyl methacrylate]-b-poly[N-(3-(methacryloylamino) propyl)-N,N-dimethyl-N-(3-sulfopropyl) ammonium hydroxide] (PDMAEMA-b-PMPDSAH) grafted luminescent carbon dots (CDs) were prepared via surface-initiated atom transfer radical polymerization (ATRP) and investigated as a multifunctional gene delivery system (denoted as CD-PDMA-PMPD) in which the CD cores acted as good multicolor cell imaging probes, the cationic PDMAEMA acted as a DNA condensing agent, and the outer shell of zwitterionic PMPDSAH block protected the vector against nonspecific interactions with serum components. As revealed by the fluorescent spectrum study, the photoluminescent attributes, especially the tunable emission property, were well inherited from the parent CDs. The CD-PDMA-PMPD could condense plasmid DNA into nanospheres with sizes of approximate 50 nm at a proper complex ratio, posing little cytotoxicity at higher ratios. It was shown that the hybrid vector exhibited significantly suppressed BSA protein adsorption and superior hemocompatibility compared to those of the widely used PEI25k. In the in vitro transfection assay, an increased serum concentration from 10 to 50% caused a dramatic drop in PEI25k transfection performance, whereas the transfection efficiency of CD-PDMA-PMPD was well maintained; CD-PDMA80-PMPD40 showed 13 and 28 times higher transfection efficiencies than PEI25k at 30 and 50% serum concentration, respectively. Intriguingly, the carbon dots in the transfected cells displayed excitation-dependent fluorescent emissions, portending that this polycation-polyzwitterion modified CD will be a promising theranostic vector with excellent stealth performance.

A facile strategy to functionalize gold nanorods with polycation brushes for biomedical applications

The fabrication of highly efficient nonviral gene carriers with low cytotoxicity remains a challenge in gene therapy. This paper reports a facile strategy to combine the advantages of gold nanorods (Au NRs) and polycations through surface functionalization. Different Au NR carriers with a controlled amount of poly(2-(N,N-dimethyl amino)ethyl methacrylate) (PDAEMA) brushes could be readily synthesized via surface-initiated atom transfer radical polymerization to achieve optimized nanohybrids for gene transfection. The obtained gene carriers demonstrate much higher gene transfection efficiency and lower cytotoxicity compared with polyethylenimine (∼25kDa, gold standard of nonviral gene vector) in both COS7 and HepG2 cell lines. In addition, the potential of the PDMAEMA-grafted Au NR carriers to be utilized as a computed tomography contrast agent for the imaging of cancer cells has also been investigated. This strategy may realize the gene therapy and real-time imaging within one nanostructure and facilitate biomedical applications.

Versatile types of polysaccharide-based supramolecular polycation/pDNA nanoplexes for gene delivery

Different polysaccharide-based supramolecular polycations were readily synthesized by assembling multiple β-cyclodextrin-cored star polycations with an adamantane-functionalized dextran via host-guest interaction in the absence or presence of bioreducible linkages. Compared with nanoplexes of the starting star polycation and pDNA, the supramolecular polycation/pDNA nanoplexes exhibited similarly low cytotoxicity, improved cellular internalization and significantly higher gene transfection efficiencies. The incorporation of disulfide linkages imparted the supramolecular polycation/pDNA nanoplexes with the advantage of intracellular bioreducibility, resulting in better gene delivery properties. In addition, the antitumor properties of supramolecular polycation/pDNA nanoplexes were also investigated using a suicide gene therapy system. The present study demonstrates that the proper assembly of cyclodextrin-cored polycations with adamantane-functionalized polysaccharides is an effective strategy for the production of new nanoplex delivery systems.

Biocleavable graphene oxide based-nanohybrids synthesized via ATRP for gene/drug delivery

Graphene oxide (GO) has been proven to be promising in many biomedical fields due to its biocompatibility, unique conjugated structure, easily tunable surface functionalization and facile synthesis. In this work, a flexible two-step method was first developed to introduce the atom transfer radical polymerization (ATRP) initiation sites containing disulfide bonds onto GO surfaces. Surface-initiated ATRP of (2-dimethyl amino)ethyl methacrylate (DMAEMA) was then employed to tailor the GO surfaces in a well-controlled manner, producing a series of organic-inorganic hybrids (termed as SS-GPDs) for highly efficient gene delivery. Under reducible conditions, the PDMAEMA side chains can be readily cleavable from the GO backbones, benefiting the resultant gene delivery process. Moreover, due to the conjugated structure of the graphene basal plane, SS-GPD can attach and absorb aromatic, water insoluble drugs, such as 10-hydroxycamptothecin (CPT), producing SS-GPD-CPT. The MTT assay and the simultaneous double-staining procedure revealed that SS-GPD-CPT possessed a high potency of killing cancer cells in vitro. With a high aqueous solubility and coulombic interaction with cell membrane, SS-GPDs may have great potential in gene/drug delivery fields.

Efficient gene carriers composed of 2-hydroxypropyl-β-cyclodextrin, ethanolamine-functionalized poly(glycidyl methacrylate), and poly((2-dimethyl amino)ethyl methacrylate) by combination of ATRP and click chemistry

In this work, a simple one-step method is first employed to produce the bromoisobutyryl-terminated 2-hydroxypropyl-β-cyclodextrin (HPCD-Br). The pendant epoxy groups of poly(glycidyl methacrylate) block prepared via ATRP from HPCD-Br can be reacted with ethanolamine to produce HPCD-PGEA which exhibits much lower cytotoxicity and better gene transfection yield than polyethylenimine (25 kDa) in COS7 and HepG2 cell lines. Moreover, poly((2-dimethyl amino)ethyl methacrylate) blocks can be incorporated into low-molecular-weight HPCD-PGEA via "click" reaction to further enhance the gene transfection efficiency in HepG2 cell lines.

Different types of degradable vectors from low-molecular-weight polycation-functionalized poly(aspartic acid) for efficient gene delivery

Poly(aspartic acid) (PAsp) has been employed as the potential backbone for the preparation of efficient gene carriers, due to its low cytotoxicity, good biodegradability and excellent biocompatibility. In this work, the degradable linear or star-shaped PBLA was first prepared via ring-opining polymerization of β-benzyl-L-aspartate N-carboxy anhydride (BLA-NCA) initiated by ethylenediamine (ED) or ED-functionalized cyclodextrin cores. Then, PBLA was functionalized via aminolysis reaction with low-molecular-weight poly(2-(dimethylamino)ethyl methacrylate) with one terminal primary amine group (PDMAEMA-NH2), followed by addition of excess ED or ethanolamine (EA) to complete the aminolysis process. The obtained different types of cationic PAsp-based vectors including linear or star PAsp-PDM-NH2 and PAsp-PDM-OH exhibited good condensation capability and degradability, benefiting gene delivery process. In comparison with gold standard polyethylenimine (PEI, ∼ 25 kDa), the cationic PAsp-based vectors, particularly star-shaped ones, exhibited much better transfection performances.

The first amphiphilic graft copolymer bearing a hydrophilic poly(2-hydroxylethyl acrylate) backbone synthesized by successive RAFT and ATRP

This paper reports the first synthesis of well-defined amphiphilic graft copolymers, consisting of a hydrophilic poly(2-hydroxyethyl acrylate) (PHEA) backbone and hydrophobic polystyrene side chains, by the combination of RAFT polymerization, ATRP, and the grafting-from strategy.

A well-defined coil–comb polycationic brush with “star polymers” as side chains for gene delivery

The well-defined polycationic brush with super-high grafting density of PDMAEMA showed higher transfection capability than the single star polymer and PEI25K.