Comb-Shaped Copolymers Composed of Hydroxypropyl Cellulose Backbones and Cationic Poly((2-dimethyl amino)ethyl methacrylate) Side Chains for Gene Delivery

pH-responsive polymeric nanomaterials for the treatment of oral biofilm infections

Bacterial and fungal pathogens forming oral biofilms present significant public health challenges due to the failure of antimicrobial drugs. The ability of biofilms to lower pH levels results in dental plaque, leading to gingivitis and cavities. Nanoparticles (NPs) have attracted considerable interest for drug delivery and, thus, as a solution to biofilm-related microbial infections. A novel strategy in this regard involves using pH-responsive polymeric NPs within the acidic microenvironment of oral biofilms. The acidity of the oral biofilm microenvironment is governed by carbohydrate metabolism, accumulation of lactic acid, and extracellular DNA of extracellular polymeric substances by oral biofilm-forming microbial pathogens. This acidity also provides an opportunity to enhance antibacterial activity against biofilm cells using pH-responsive drug delivery approaches. Thus, various polymeric NPs loaded with poorly soluble drugs and responsive to the acidic pH of oral biofilms have been developed. This review focuses on various forms of such polymeric NPs loaded with drugs. The fundamental mechanisms of action of pH-responsive polymeric NPs, their cytological toxicity, and in vivo efficacy testing are thoroughly discussed.

Dually Modified Cellulose as a Non-Viral Vector for the Delivery and Uptake of HDAC3 siRNA

RNA interference can be applied to different target genes for treating a variety of diseases, but an appropriate delivery system is necessary to ensure the transport of intact siRNAs to the site of action. In this study, cellulose was dually modified to create a non-viral vector for HDAC3 short interfering RNA (siRNA) transfer into cells. A guanidinium group introduced positive charges into the cellulose to allow complexation of negatively charged genetic material. Furthermore, a biotin group fixed by a polyethylene glycol (PEG) spacer was attached to the polymer to allow, if required, the binding of targeting ligands. The resulting polyplexes with HDAC3 siRNA had a size below 200 nm and a positive zeta potential of up to 15 mV. For N/P ratio 2 and higher, the polymer could efficiently complex siRNA. Nanoparticles, based on this dually modified derivative, revealed a low cytotoxicity. Only minor effects on the endothelial barrier integrity and a transfection efficiency in HEK293 cells higher than Lipofectamine 2000TM were found. The uptake and release of the polyplexes were confirmed by immunofluorescence imaging. This study indicates that the modified biopolymer is an auspicious biocompatible non-viral vector with biotin as a promising moiety.

Single-helical formyl β-glucan effectively deliver CpG DNA with poly(dA) to macrophages for enhanced vaccine effects

Single helical β-glucan is a one-dimensional host that can form a hybrid helix with DNAs/RNAs as delivery systems. However, unmodified β-glucan has a gelling tendency and a single helical conformation is challenging to obtain. Therefore, in this study, we developed a β-glucan formyl derivative with stable single helical conformation and no gelling tendency. Circular dichroism studies found that the formyl-β-glucan could form a hybrid helix with DNA CpG-poly(dA). The hybrid helix delivery system showed improved activation on antigen-presenting cells, thereby upregulating the mRNA and protein levels of inflammatory factors, and had an immune-enhancing effect on ovalbumin (OVA) immunized mice. These results indicate that formyl-β-glucan can be developed as a non-cationic supramolecular DNA delivery platform with low toxicity and high efficiency.

Efficient Transient Expression of Plasmid DNA Using Poly (2-(N,N-Dimethylamino) Ethyl Methacrylate) in Plant Cells

Nanomaterials have been widely studied for their potential to become the new generation of nanocarriers in gene transfection, yet it remains still difficult to apply them efficiently and succinctly to plant cells. Poly (2-(N,N-dimethylamino) ethyl methacrylate) (PDMAEMA), which possesses temperature and pH dual-sensitivity, has largely been applied in animal cells, but it is rarely involved in plant cells. As a proof of concept, PDMAEMA as a gene carrier is incubated with plasmid GFP (pGFP) to explore its transfection ability in plants, and cationic polymer polyethylenimine (PEI) is used as a control. pGFP was efficiently condensed into the nanostructure by electrostatic interactions at an N/P (amino group from cationic polymers/phosphate group from plasmid DNA (pDNA)) ratio of 15; after complexation into nanocarriers, pGFP was protected from endonuclease degradation according to the DNase I digestion assay. After incubation with protoplasts and leaves, GFP was observed with confocal microscopy in plant cells. Western blot experiments confirmed GFP expression at the protein level. Toxicity assay showed PDMAEMA had a lower toxicity than PEI. These results showed that transient expression of pGFP was readily achieved in Arabidopsis thaliana and Nicotiana benthamiana. Notably, PDMAEMA showed lower cytotoxicity than PEI upon incubation with Nicotiana benthamiana leaves. PDMAEMA exhibited great potency for DNA delivery in plant cells. This work provides us with new ideas of more concise and more effective methods for plant transformation.

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.

Physicochemical Properties and Biological Performance of Polymethacrylate Based Gene Delivery Vector Systems: Influence of Amino Functionalities

Physicochemical characteristics and biological performance of polyplexes based on two identical copolymers bearing tertiary amino or quaternary ammonium groups are evaluated and compared. Poly(2-(dimethylamino)ethyl methacrylate)-b-poly(oligo(ethylene glycol) methyl ether methacrylate) block copolymer (PDMAEMA-b-POEGMA) is synthesized by reversible addition fragmentation chain transfer polymerization. The tertiary amines of PDMAEMA are converted to quaternary ammonium groups by quaternization with methyl iodide. The two copolymers spontaneously formed well-defined polyplexes with DNA. The size, zeta potential, molar mass, aggregation number, and morphology of the polyplex particles are determined. The parent PDMAEMA-b-POEGMA exhibits larger buffering capacity, whereas the corresponding quaternized copolymer (QPDMAEMA-b-POEGMA) displays stronger binding affinity to DNA, yielding invariably larger in size and molar mass particles bearing greater number of DNA molecules per particle. Experiments revealed that QPDMAEMA-b-POEGMA is more effective in transfecting pEGFP-N1 than the parent copolymer, attributed to the larger size, molar mass, and DNA cargo, as well as to the effective cellular traffic, which dominated over the enhanced ability for endo-lysosomal escape of PDMAEMA-b-POEGMA.

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.

Non-viral transfection vectors: are hybrid materials the way forward?

Transfection is a process by which oligonucleotides (DNA or RNA) are delivered into living cells. This allows the synthesis of target proteins as well as their inhibition (gene silencing). However, oligonucleotides cannot cross the plasma membrane by themselves; therefore, efficient carriers are needed for successful gene delivery. Recombinant viruses are among the earliest described vectors. Unfortunately, they have severe drawbacks such as toxicity and immunogenicity. In this regard, the development of non-viral transfection vectors has attracted increasing interests, and has become an important field of research. In the first part of this review we start with a tutorial introduction into the biological backgrounds of gene transfection followed by the classical non-viral vectors (cationic organic carriers and inorganic nanoparticles). In the second part we highlight selected recent reports, which demonstrate that hybrid vectors that combine key features of classical carriers are a remarkable strategy to address the current challenges in gene delivery.

The influence of gradient and statistical arrangements of guanidinium or primary amine groups in poly(methacrylate) copolymers on their DNA binding affinity

Herein, we report the first gradient guanidinium containing cationic copolymers and investigate their binding ability to plasmid DNA (pDNA).

A Simple Approach to Bioconjugation at Diverse Levels: Metal-Free Click Reactions of Activated Alkynes with Native Groups of Biotargets without Prefunctionalization

The efficient bioconjugation of functional groups/molecules to targeted matrix and bio-related species drives the great development of material science and biomedicine, while the dilemma of metal catalysis, uneasy premodification, and limited reaction efficiency in traditional bioconjugation has restricted the booming development to some extent. Here, we provide a strategy for metal-free click bioconjugation at diverse levels based on activated alkynes. As a proof-of-concept, the abundant native groups including amine, thiol, and hydroxyl groups can directly react with activated alkynes without any modification in the absence of metal catalysis. Through this strategy, high-efficient modification and potential functionalization can be achieved for natural polysaccharide, biocompatible polyethylene glycol (PEG), synthetic polymers, cell penetrating peptide, protein, fast whole-cell mapping, and even quick differentiation and staining of Gram-positive bacteria, etc. Therefore, current metal-free click bioconjugation strategy based on activated alkynes is promising for the development of quick fluorescence labeling and functional modification of many targets and can be widely applied towards the fabrication of complex biomaterials and future in vivo labeling and detection.

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.

Biodegradable Polymeric Architectures via Reversible Deactivation Radical Polymerizations

Reversible deactivation radical polymerizations (RDRPs) have proven to be the convenient tools for the preparation of polymeric architectures and nanostructured materials. When biodegradability is conferred to these materials, many biomedical applications can be envisioned. In this review, we discuss the synthesis and applications of biodegradable polymeric architectures using different RDRPs. These biodegradable polymeric structures can be designed as well-defined star-shaped, cross-linked or hyperbranched via smartly designing the chain transfer agents and/or post-polymerization modifications. These polymers can also be exploited to fabricate micelles, vesicles and capsules via either self-assembly or cross-linking methodologies. Nanogels and hydrogels can also be prepared via RDRPs and their applications in biomedical science are also discussed. In addition to the synthetic polymers, varied natural precursors such as cellulose and biomolecules can also be employed to prepare biodegradable polymeric architectures.

Preparation of well-defined brush-like block copolymers for gene delivery applications under biorelevant reaction conditions

Well-defined oligo(ethylene glycol) methyl ether methacrylate (OEOMA) based block copolymers with cationic segments composed by N,N-(dimethylamino) ethyl methacrylate (DMAEMA) and/or 2-(diisopropylamino) ethyl methacrylate (DPA) were developed under biorelevant reaction conditions. These brush-type copolymers were synthesized through supplemental activator and reducing agent (SARA) atom transfer radical polymerization (ATRP) using sodium dithionite as SARA agent. The synthesis was carried out using an eco-friendly solvent mixture, very low copper catalyst concentration, and mild reaction conditions. The structure of the block copolymers was characterized by size exclusion chromatography (SEC) analysis and ¹H nuclear magnetic resonance (NMR) spectroscopy. The pH-dependent protonation of these copolymers enables the efficient complexation with plasmid DNA (pDNA), yielding polyplexes with sizes ranging from 200 up to 700 nm, depending on the molecular weight of the copolymers, composition and concentration used. Agarose gel electrophoresis confirmed the successful pDNA encapsulation. No cytotoxicity effect was observed, even for N/P ratios higher than 50, for human fibroblasts and cervical cancer cell lines cells. The in vitro cellular uptake experiments demonstrated that the pDNA-loaded block copolymers were efficiently delivered into nucleus of cervical cancer cells. The polymerization approach, the unique structure of the block copolymers and the efficient DNA encapsulation presented can open new avenues for development of efficient tailor made gene delivery systems under biorelevant conditions.

Synthesis, thermal properties and cell-compatibility of photocrosslinked cinnamoyl-modified hydroxypropyl cellulose

Biocompatibility of cinnamoyl-modified carbohydrate materials is not well-known, while they are attracting attention as a photoreactive material. In order to investigate biocompatible properties of cinnamoyl-modified carbohydrate, hydroxypropyl cellulose (HPC) was reacted with cinnamoyl chloride to yield cinnamoyl-modified HPC (HPC-C) for a cell proliferation test. HPC-Cs with three different degrees of substitution (DS) were prepared by changing a feed ratio of cinnamoyl chloride to HPC. The DS of the products ranged from 1.3 to 3.0 per one hydroxylpropyl anhydroglucose unit. Thermal analysis using DSC and TGA showed that the HPC-C with higher DS has a glass transition temperature and higher thermal stability. Ultraviolet (UV) light was irradiated on the HPC-C thin films, and changes in the UV-vis spectrum of the films were examined. In the course of UV irradiation, the absorbance at 280 nm was reduced. Fibroblast cells were cultured on the photocrosslinked HPC-C films, and cell growth was examined. The cell proliferation test revealed that the photocrosslinked HPC-C films have good compatibility with fibroblast cells.

Significant role of cationic polymers in drug delivery systems

Cationic polymers are characterized as the macromolecules that possess positive charges, which can be either inherently in the polymer side chains and/or its backbone. Based on their origins, cationic polymers are divided in two category including natural and synthetic, in which the possessed positive charges are as result of primary, secondary or tertiary amine functional groups that could be protonated in particular situations. Cationic polymers have been employed commonly as drug delivery agents due to their superior encapsulation efficacy, enhanced bioavailability, low toxicity and improved release profile. In this paper, we focus on the most prominent examples of cationic polymers which have been revealed to be applicable in drug delivery systems and we also discuss their general synthesis and surface modification methods as well as their controlled release profile in drug delivery.

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.

Transfection of immortalized keratinocytes by low toxic poly(2-(dimethylamino)ethyl methacrylate)-based polymers

Skin carcinoma are among the most spread diagnosed tumours in the world. In this study, we investigated the transfection of immortalized keratinocytes, used as an in vitro model for skin carcinoma, using antisense technology and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA)-based polymers, with original architecture and functionalities. We tested PDMAEMA polymers with different structures: linear, with two (DEA-PDMAEMA) or three (TEA-PDMAEMA) arms. The cytotoxicity of these polymers was assessed over a wide range of apparent M n (from 7600 to 64 600). At a N/P ratio of 7.38, cytotoxicity increases with the M n. Keratinocytes were transfected with a fluorescent oligonucleotide and then analyzed by flow cytometry. For the three architectures tested, the percentage of transfected cells and abundance of internalized oligonucleotide were closely related to the M n of the polymer. Confocal microscopy and FACS analyses showed a wide spread fine granular distribution of the oligonucleotide up to 3 days post-transfection. Then, we assessed the silencing efficiency of the polymers, targeting GFP in GFP expressing keratinocytes. The maximal silencing effect (±40%) was obtained using a DEA-PDMAEMA polymer (M n = 30 300). These results suggest that PDMAEMA-based polymers can be efficiently used to transfect immortalized keratinocytes and, thus, open new perspectives in the therapy of skin carcinoma.

Nano-Sized Sunflower Polycations As Effective Gene Transfer Vehicles

The architecture of polycations plays an important role in both gene transfection efficiency and cytotoxicity. In this work, a new polymer, sunflower poly(2-dimethyl amino)ethyl methacrylate) (pDMAEMA), is prepared by atom transfer radical polymerization and employed as nucleic acid carriers compared to linear pDMAEMA homopolymer and comb pDMAEMA. The sunflower pDMAEMAs show higher IC50 , greater buffering capacity, and stronger binding capacity toward plasmid DNA than their linear and comb counterparts. In vitro transfection studies demonstrate that sunflower pDMAEMAs exhibit high transfection efficiency as well as relatively low cytotoxicity in complete growth medium. In vivo gene delivery by intraventricular injection to the brain shows that sunflower polymer delivers plasmid DNA more effectively than comb polymer. This study provides a new insight into the relationship between polymeric architecture and gene delivery capability, and as well as a useful means to design potent vectors for successful gene delivery.

Poly(aspartic acid)-based degradable assemblies for highly efficient gene delivery

Due to its good properties such as low cytotoxicity, degradability, and biocompatibility, poly(aspartic acid) (PAsp) is a good candidate for the development of new drug delivery systems. In this work, a series of new PAsp-based degradable supramolecular assemblies were prepared for effective gene therapy via the host-guest interactions between the cyclodextrin (CD)-cored PAsp-based polycations and the pendant benzene group-containing PAsp backbones. Such supramolecular assemblies exhibited good degradability, enhanced pDNA condensation ability, and low cytotoxicity. More importantly, the gene transfection efficiencies of supramolecular assemblies were much higher than those of CD-cored PAsp-based counterparts at various N/P ratios. In addition, the effective antitumor ability of assemblies was demonstrated with a suicide gene therapy system. The present study would provide a new means to produce degradable supramolecular drug delivery systems.

Quaternized poly(2-(dimethylamino)ethyl methacrylate)-grafted agarose copolymers for multipurpose antibacterial applications

Polymeric quaternary ammonium salts-functionalized agarose not only exhibit good antibacterial activity in solution form, but also can be solidified to construct antibacterial surfaces.

Natural Cationic Polymers for Advanced Gene and Drug Delivery

Gene and drug delivery is becoming more and more important in the treatment of complicated human diseases. Proper gene/drug delivery systems can effectively enhance therapeutic efficiency and minimize various side-effects. To date, a variety of delivery systems have been developed. Different from synthetic materials, natural polymers are abundant in nature, renewable, non-toxic, biocompatible and biodegradable. Owing to the presence of positive charges, natural cationic polymers have found important applications in many biological fields, such as drug/gene delivery and tissue engineering. In gene delivery, natural cationic polymers can condense nucleic acids, protect them from degradation, lower the immunogenicity and improve overall transfection efficiency. In drug delivery, cationic functional groups can alter the amphiphilic properties of the polymers to ensure their suitable applications for delivering hydrophobic or protein drugs. After simple chemical modification, the derivatives of natural cationic polymers show improved performance as functional delivery carriers. In this chapter, details on the chemical modification of natural cationic polymers and their applications in gene/drug delivery is discussed.

Cationic polymer brush-modified cellulose nanocrystals for high-affinity virus binding

Surfaces capable of high-affinity binding of biomolecules are required in several biotechnological applications, such as purification, transfection, and sensing. Therein, the rod-shaped, colloidal cellulose nanocrystals (CNCs) are appealing due to their large surface area available for functionalization. In order to exploit electrostatic binding, their intrinsically anionic surfaces have to be cationized as biological supramolecules are predominantly anionic. Here we present a facile way to prepare cationic CNCs by surface-initiated atom-transfer radical polymerization of poly(N,N-dimethylaminoethyl methacrylate) and subsequent quaternization of the polymer pendant amino groups. The cationic polymer brush-modified CNCs maintained excellent dispersibility and colloidal stability in water and showed a ζ-potential of +38 mV. Dynamic light scattering and electron microscopy showed that the modified CNCs electrostatically bind cowpea chlorotic mottle virus and norovirus-like particles with high affinity. Addition of only a few weight percent of the modified CNCs in water dispersions sufficed to fully bind the virus capsids to form micrometer-sized assemblies. This enabled the concentration and extraction of the virus particles from solution by low-speed centrifugation. These results show the feasibility of the modified CNCs in virus binding and concentrating, and pave the way for their use as transduction enhancers for viral delivery applications.

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.

Cationic methylcellulose derivative with serum-compatibility and endosome buffering ability for gene delivery systems

In this work, methylcellulose was employed as a template polymer with graft of polyethylenimine 0.8 kDa (PEI0.8k) for gene delivery systems. Synthesized PEI-grafted oxidized methylcellulose (MC-PEI) could condense pDNA into positively charged and nano-sized particles, which could protect pDNA from serum nuclease. The cytotoxicity of MC-PEI was minimal in both serum-free and serum condition due to the biocompatibility of methylcellulose and low cytotoxicity of PEI0.8k. MC-PEI polyplex also showed low cytotoxicity in serum condition. In serum condition, MC-PEI showed less decreased transfection efficiency than PEI25k, meaning good serum-compatibility of MC-PEI. Bafilomycin A1-treated transfection results indicate that the transfection of MC-PEI is mediated via endosomal escape by endosome buffering ability. Flow cytometry results suggest that MC-PEI polyplex could be internalized into cells and efficiently deliver pDNA to cells due to its serum-compatibility. These results demonstrate that MC-PEI possesses a potential for efficient gene delivery systems.

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 preparation of graft copolymers of cellulose and cellulose derivatives using ATRP under homogeneous reaction conditions

Atom transfer radical polymerisation (ATRP) is used to modify cellulose and cellulose derivatives under homogeneous conditions, yielding novel materials for application in areas such as drug delivery.