alpha,beta-poly(asparthylhydrazide)-glycidyltrimethylammonium chloride copolymers (PAHy-GTA): novel polymers with potential for DNA delivery

Cationic Supramolecular Vesicular Aggregates for Pulmonary Tissue Selective Delivery in Anticancer Therapy

The biopharmaceutical properties of supramolecular vesicular aggregates (SVAs) were characterized with regard to their physicochemical features and compared with cationic liposomes (CLs). Neutral and cationic SVAs were synthesized using two different copolymers of poly(aspartyl hydrazide) by thin-layer evaporation and extrusion techniques. Both copolymers were self-assembled in pre-formulated liposomes and formed neutral and cationic SVAs. Gemcitabine hydrochloride (GEM) was used as an anticancer drug and loaded by a pH gradient remote loading procedure, which significantly increased drug loading inside the SVAs. The resulting average size of the SVAs was 100 nm. The anticancer activity of GEM-loaded neutral and cationic SVAs was tested in human alveolar basal epithelial (A549) and colorectal cancer (CaCo-2) cells. GEM-loaded cationic SVAs increased the anticancer activity in A549 and CaCo-2 cells relative to free drug, neutral SVAs, and CLs. In vivo biodistribution in Wistar rats showed that cationic SVAs accumulate at higher concentrations in lung tissue than neutral SVAs and CLs. Cationic SVAs may therefore serve as an innovative future therapy for pulmonary carcinoma.

Synthesis and rheological characterization of water-soluble glycidyltrimethylammonium-chitosan

In this study, chitosan (CS) grafted by glycidyltrimethylammonium chloride (GTMAC) to form GTMAC-CS was synthesized, chemically identified, and rheologically characterized. The Maxwell Model can be applied to closely simulate the dynamic rheological performance of the chitosan and the GTMAC-CS solutions, revealing a single relaxation time pertains to both systems. The crossover point of G' and G" shifted toward lower frequencies as the CS concentration increased but remained almost constant frequencies as the GTMAC-CS concentration increased, indicating the solubility of GTMAC-CS in water is good enough to diminish influence from the interaction among polymer chains so as to ensure the relaxation time is independent of the concentration. A frequency-concentration superposition master curve of the CS and GTMAC-CS solutions was subsequently proposed and well fitted with the experimental results. Finally, the sol-gel transition of CS is 8.5 weight % (wt %), while that of GTMAC-CS is 20 wt %, reconfirming the excellent water solubility of the latter.

Immunogenicity of a bovine herpesvirus 1 glycoprotein D DNA vaccine complexed with bovine neutrophil beta-defensin 3

Protective efficacy against bovine herpesvirus 1 (BoHV-1) has been demonstrated to be induced by a plasmid encoding bovine neutrophil beta-defensin 3 (BNBD3) as a fusion construct with truncated glycoprotein D (tgD). However, in spite of the increased cell-mediated immune responses induced by this DNA vaccine, the clinical responses of BoHV-1-challenged cattle were not reduced over those observed in animals vaccinated with the plasmid encoding tgD alone; this might have been because the vaccine failed to improve humoral responses. We hypothesized that an alternative vaccine design strategy that utilized the DNA vaccine pMASIA-tgD as a complex with BNBD3 might improve humoral responses while maintaining robust Th1-type cell-mediated responses. C57BL/6 mice were vaccinated with pMASIA-tgD complexed with 0, 0.01875, 0.1875, or 1.875 nmol of a stable synthesized analog of BNBD3 (aBNBD3). The best results were seen in mice immunized with the vaccine composed of pMASIA-tgD complexed to 0.1875 nmol aBNBD3. In this group, humoral responses were improved, as evidenced by increased virus neutralization, tgD-specific early IgG1, and later IgG2a titers, while the strong cell-mediated immune responses, measured based on specific gamma interferon (IFN-γ)-secreting cells, were maintained relative to pMASIA-tgD. Modulation of the immune response might have been due in part to the effect of BNBD3 on dendritic cells (DCs). In vitro studies showed that murine bone marrow-derived DCs (BMDCs) pretreated with aBNBD3 were activated, as evidenced by CD11c downregulation, and were functionally mature, as shown by increased allostimulatory ability. Native, synthetic, and analog forms of BNBD3 were equally capable of inducing functional maturation of BMDCs.

Current progress in gene delivery technology based on chemical methods and nano-carriers

Gene transfer methods are promising in the field of gene therapy. Current methods for gene transfer include three major groups: viral, physical and chemical methods. This review mainly summarizes development of several types of chemical methods for gene transfer in vitro and in vivo by means of nano-carriers like; calcium phosphates, lipids, and cationic polymers including chitosan, polyethylenimine, polyamidoamine dendrimers, and poly(lactide-co-glycolide). This review also briefly introduces applications of these chemical methods for gene delivery.

The investigation on polyion complex micelles composed of diammonium glycyrrhizinate/poly(ethylene glycol)-glycidyltrimethylammonium chloride-grafted polyasparthydrazide

To prepare stable polyion complex (PIC) micelles, polyasparthydrazide (PAHy) modified with glycidyltrimethylammonium groups and methoxy poly(ethylene glycol) (mPEG) (mPEG-g-PAHy-GTA) was synthesized. The cytotoxicity of the polymer was evaluated by the methyl tetrazolium assay. The polymer entrapped the diammonium glycyrrhizinate (DG) and formed polyion complexes. The effect of pH value, grafting degree of mPEG, copolymer and drug concentration on the micelle formation was investigated by means of measuring entrapment efficiency and micelle size. In vitro DG release from the PIC micelles was detected by dialysis in various media of different ionic strengths. To examine the pharmacokinetic behavior of micelles in vivo, the time course of the drug in plasma was evaluated. The cytotoxicity of the polymer was very low. The results showed that entrapment efficiency can reach about 93%, and the mean particle size was almost 50 nm. The drug release rate decreased with a decrease in ionic strength of the release medium or an increase in the PEG grafting degree. Compared with DG solution, the AUC of DG micelles had a twofold increase. The smaller clearance and longer mean residence time of the DG micelles group compared with DG solution group showed that the DG loaded in PIC micelles can reduce drug elimination and prolong the drug residence time in the blood circulation. The results indicated that PIC micelles composed of mPEG-g-PAHy-GTA would be prospective as a drug carrier to the drugs which can be ionized in solution.

Evaluation of Jeffamine®-cored PAMAM dendrimers as an efficient in vitro gene delivery system

In this study, we investigated gene delivery properties of Jeffamine-cored polyamidoamine (PAMAM) dendrimers (JCPDs). The effects of dendrimer concentration, generation, and core size on the gene delivery have been analyzed. The experimental results showed that the JCPD effectively delivered plasmid DNA inside the HeLa cells, and the transfection efficiency improved considerably as the number of generation increased. The cytotoxicity of JCPD in different concentration was tested for HeLa cell line. JCPD was complexed with a lacZ gene carrying plasmid and tested for transfection efficiency using quantitative β-galactosidase expression assay. Additionally, confocal microscopy results revealed that JCPD effectively delivered green fluorescent protein-expressing plasmid into HeLa cells and produced fluorescent signal with satisfactory efficiency. The highest transfection efficiency was obtained from JCPDs G4 and G5, which mixed with expression plasmid vectors at a 10/1 weight ratio. These results indicated that under optimized conditions, JCPD can be considered as an efficient transfection reagent and can be effectively used for gene delivery applications.

Evaluation of generations 2, 3 and 4 arginine modified PAMAM dendrimers for gene delivery

It is a matter of concern to develop and design synthetic non-viral gene carriers with high transfection efficiency and low cytotoxicity in gene therapy. Recently, various arginine conjugated dendrimers showed better performance in transfection and greater viability than polyethyleneimine (PEI). In this study, we synthesized and investigated e-PAM-R G2, 3 and 4 which are biodegradable polyamidoamine (PAMAM) dendrimers modified with arginine and compared that with PAMAM-R series containing amide bonds for gene carriers. For plasmid DNA delivery, the transfection efficiency of e-PAM-R G4 was higher than G3 and G2 and similar to PAMAM-R G4 with favorable cell viability. Moreover, they indicated significantly higher suppression of TEL/AML1 protein, maybe due to rapid olidonucleotide (ODNs) release through biodegradability of e-PAM-R. These results suggest that biodegradable and non-toxic e-PAM-R may be useful carriers for the gene including plasmid DNA, antisense ODNs and si-RNA.

Novel Cationic Copolymers of a Polyasparthylhydrazide: Synthesis and Characterization

Alpha,beta-poly(asparthylhydrazide) (PAHy), a water soluble synthetic polymer, was functionalized by using EDCI chemistry with 3-(carboxypropyl)trimethyl-ammonium chloride (CPTACl) obtaining carboxypropyltrimethyl ammonium copolymers (PAHy-CPTA). Three PAHy-CPTA copolymers at increasing derivatization degrees (38%, 48%, 58%) were chosen for subsequent investigations. The capability of these copolymers to bind, neutralize, and protect DNA against degradation by DNase II was evalued by gel retardation assay and DNA degradation test at pH 5.5. Zeta potential measurements show that all studied polymers are able to neutralize the anionic charge of DNA at polymer/DNA weight ratio in the range of 0.8/1-5/1. Polyplex dimensional distribution analyses in bistilled water, saline solution NaCl 0.9%, and HEPES pH 7 show that polyplex size is strongly affected by both presence and type of electrolyte and with time incubation.

Design and synthesis of novel galactosylated polymers for liposomes as gene drug carriers targeting the hepatic asialoglycoprotein receptor

The 18-mer oligodeoxynucleotides (ODNs) that can inhibit survivin gene expression were selected as a model gene drug to study hepatic-targeting drug delivery system. Novel galactosylated polymers (cholesteryloxycarbonylamino) ethylamine-alpha,beta-polyasparthydrazied (CHE-PAHy-Lacs), which target asialoglycoprotein receptor on hepatic parenchymal cells (PC), were designed and synthesized as non-toxic, non-antigenic and non-teratogenic ligands for liposomes. The liposomes incorporating different CHE-PAHy-Lacs were prepared and characterized by zeta potential and particle size analyzer. The drug encapsulation efficiency was measured by gel filtration method. 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate was used as a marker for all the liposome preparations in the in vivo experiments. The CHE-PAHy-Lac liposomes produced a significant improvement in the encapsulation efficiency of ODNs (28.73-51.37%) compared with conventional liposomes (9.88%). The in vivo results showed that the liposomes incorporating CHE-PAHy-Lac, which contained about 30% (w/w) galactosyl residues, exhibited marked accumulation in the liver and hepatic PC. These results suggest that the novel galactosylated polymers used for liposomes have a great potential as a gene delivery system for hepatic targeting.

An efficient vector for gene delivery: α,β-poly (3-dimethylaminopropyl-d,l-aspartamide)

PSI, as the potential peptide-like intermediate, is subject to simple chemical modification in order to obtain good non-viral carriers for gene delivery. This paper describes the facile synthesis and preliminary evaluation of alpha,beta-poly (3-dimethylaminopropyl-D,L-aspartamide) (PDAI) as a vector. Reaction of PSI with 3-dimethylamino-1-propylamine afforded PDAI in N,N-dimethylformamide (DMF) solution. Such biophysical properties of PDAI/DNA complexes as the particle size and the zeta potential were determined by dynamic light scattering assay. The complexes prepared at weight ratios ranging from 2 to 3 have an average size of around 200 nm and a zeta potential of around 10.0 mV. Gel electrophoresis assays confirmed that PDAI could compact DNA to form the complexes and protect DNA from enzymatic degradation by DNase I at the weight ratio above 2.0. Furthermore, PDAI was found to transfect HepG2 cells at a much higher efficiency than commercially available polyethylenimine (PEI) (W(w)=75,000 Da). MTT cytotoxicity assay demonstrated that PDAI also showed much less toxicity than did PEI, suggesting that PDAI is a new class of transfection reagent to be used as a safe vector.

Reversibly stable thiopolyplexes for intracellular delivery of genes

Novel polyaspartamide non-viral carriers for gene therapy were synthesized by introducing, on the same polymer backbone, positively charged groups, for electrostatic interactions with DNA, and thiol groups for the formation of disulfide bridges between polymer chains. The introduction of thiols was aimed to have a vector with low redox potential sensitivity: disulfide crosslinking in fact, being stable in extracellular environment, allowed either to have stable complexes in plasma, that can protect DNA from metabolism, or to be reduced inside the cell, where the excess of glutathion in reduced form maintains a low redox potential. The consequent destabilization of the complex after disulfide cleavage can release DNA selectively inside the cells. Alpha,beta-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA) was used as starting polymer being a highly water-soluble synthetic polymer, already proposed with success as therapeutic carrier by our group. In this study, PHEA was firstly functionalised with ethylendiamine, obtaining a well defined copolymer with pendant primary amine groups (PHEA-EDA), to which N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP) and 3-(carboxypropyl)trimethyl-ammonium chloride (CPTA) were linked in two subsequent steps, allowing the introduction of thiol and cationic groups respectively. Finally DTT treatment lead to the final PHEA-EDA-SH-CPTA thiopolycation, named PESC. The present work describes the synthesis and characterization of the thiopolycation PESC. 1H NMR spectroscopy detected the derivatization molar degrees in SPDP and CPTA; the formation of DNA complexes (thiopolyplexes), their stability in the presence of polyanions and the ability to release DNA under reductive conditions were studied by agarose gel electrophoresis. DNase II degradation study was carried out to detect the ability of thiopolyplex to stabilize DNA towards enzymatic metabolism. Thiopolyplexes were then characterized by Dynamic Light Scattering (DLS) and Zeta Potential analysis. Finally, in vitro toxicity profile (MTT) and gene transfer efficiency (Luciferase assay) were carried out to evaluate thiopolyplex biocompatibility, safety and efficacy to be used as gene delivery system.

Synthesis and characterization of polyaminoacidic polycations for gene delivery

The properties as non viral gene vector of a protein-like polymer, the alpha,beta-poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA) were exploited after its derivatization with 3-(carboxypropyl)trimethyl-ammonium chloride (CPTA) as molecule bearing a cationic group, in order to obtain stable polycations able to condense DNA. PHEA was firstly functionalized with aminic pendant groups by reaction with ethylenediamine (EDA) obtaining the alpha,beta-poly(N-2-hydroxyethyl)(2-aminoethylcarbamate)-d,l-aspartamide (PHEA-EDA) copolymer. We demonstrated that polymer functionalization degree is easily modulable by varying reaction conditions, so allowing to produce two PHEA-EDA derivatives at different molar percentage of amine groups. Subsequently, the condensation reaction of PHEA-EDA copolymers with CPTA yielded alpha,beta-poly(N-2-hydroxyethyl)(2-[3-(trimethylammonium chloride)propylamide]-amidoethylcarbamate)-d,l-aspartamide (PHEA-EDA-CPTA) polycation derivatives. In vitro studies were carried out to evaluate polycations ability to complex DNA and to protect it from nuclease degradation. Obtained results demonstrated the good ability of our new PHEA polycationic derivatives, PHEA-EDA-CPTA, to complex and condense genomic material, neutralizing its anionic charge even at very low polycation/DNA weight ratio. Finally, PHEA-EDA-CPTA polycations were characterized by in vitro cytotoxicity studies to evaluate their effects on the viability of HuH-6 human hepatocellular carcinoma cells by MTS assay. No cytotoxicity was evidenced by both polycationic derivatives after 48h of incubation at all tested concentrations.

Biocompatibility of implantable synthetic polymeric drug carriers: focus on brain biocompatibility

Numerous polymeric biomaterials are implanted each year in human bodies. Among them, drug delivery devices are potent novel powerful therapeutics for diseases which lack efficient treatments. Controlled release systems are in direct and sustained contact with the tissues, and some of them degrade in situ. Thus, both the material itself and its degradation products must be devoid of toxicity. The knowledge and understanding of the criteria and mechanisms determining the biocompatibility of biomaterials are therefore of great importance. The classical tissue response to a foreign material leads to the encapsulation of the implant, which may impair the drug diffusion in the surrounding tissue and/or cause implant failure. This tissue response depends on different factors, especially on the implantation site. Indeed, several organs possess a particular immunological status, which may reduce the inflammatory and immune reactions. Among them, the central nervous system is of particular interest, since many pathologies still need curative treatments. This review describes the classical foreign body reaction and exposes the particularities of the central nervous system response. The recent in vivo biocompatibility studies of implanted synthetic polymeric drug carriers are summarized in order to illustrate the behavior of different classes of polymers and the methodologies used to evaluate their tolerance.