Biomedical subjects

Julia Kloeckner

Publications and source records attributed to Julia Kloeckner.

5 recordsLinked to original sources

PubMed2006

Degradable gene carriers based on oligomerized polyamines.

The focus of this work was to develop potentially biodegradable, polycationic gene carriers possessing high efficiency for gene delivery and being essentially non-toxic. A library of 37 soluble polycations was synthesized by oligomerization of low molecular weight oligoamines with three different crosslinkers, dithiobis-succinimidyl proprionate, dimethyl dithiobis-propionamidate, and hexanediol diacrylate. The types of oligoamine and crosslinker influenced biophysical properties such as DNA binding, hemolytic and endosomolytic membrane activity, transfection efficiency and cytotoxicity of the gene carrier. Degradability of polymers based on reductive cleavage of disulfide bonds or ester hydrolysis was demonstrated. Within the library, oligoethylenimine (800 Da)-based polymers showed the highest gene transfer efficiencies and exceeded the golden standard linear polyethylenimine (22 kDa) in terms of activity/toxicity profile.

Animals↗

PubMed2006

DNA polyplexes based on degradable oligoethylenimine-derivatives: combination with EGF receptor targeting and endosomal release functions.

Combination of the degradable polymeric gene carriers OEI-HD-1 and LT- OEI-HD-1 with an EGF targeting conjugate resulted in strongly (up to 900-fold) enhanced polyplex activity in EGF-receptor rich HUH7 hepatocellular carcinoma cells. The targeting ligand effect was DNA dose dependent, could be blocked by competitive receptor binding with unbound EGF ligand, and was not observed in receptor-negative control cells. Measures which enhance intracellular endosomal escape, either photochemically enhanced intracellular release (PCI) or the incorporation of a novel membrane-active melittin analog NMA-3, further enhanced gene transfer activity of EGF/OEI-HD-1 polyplexes.

Animals↗

PubMed2005

Gelatin nanoparticles as a new and simple gene delivery system.

PURPOSE: The aim of this study was to evaluate cationized gelatin nanoparticles as biodegradable and low cell toxic alternative carrier to existing DNA delivery systems. METHODS: Native gelatin nanoparticles were produced using a two step desolvation method. In order to bind DNA by electrostatic interactions onto the surface of the particles, the quaternary amine cholamine was covalently coupled to the particles. The modified nanoparticles were loaded with different amounts of plasmid in varying buffers and compared to polyethyleneimine-DNA complexes (PEI polyplexes) as gold standard. Transfection ability of the loaded nanoparticles was tested on B16 F10 cells. Additionally, the cell toxicity of the formulations was monitored. RESULTS: Different setups resulted in efficient gene delivery displayed by exponential increase of gene expression. The gene expression itself occurred with a certain delay after transfection. In contrast to PEI polyplexes, cationized gelatin nanoparticles almost did not show any significant cytotoxic effects. CONCLUSIONS: Cationized gelatin nanoparticles have shown the potential of being a new effective carrier for nonviral gene delivery. The major benefit of gelatin nanoparticles is not only the very low cell toxicity, but also their simple production combined with low costs and multiple modification opportunities offered by the matrix molecule.

Animals↗

PubMed2004

Photochemically enhanced gene delivery of EGF receptor-targeted DNA polyplexes.

Epidermal growth factor receptor (EGFR) targeted DNA polyplexes, containing polyethylenimine (PEI) conjugated with EGF protein as cell-binding ligand for endocytosis and polyethylene glycol (PEG) for masking the polyplex surface charge, mediated a 3- to 30-fold higher luciferase gene expression in HUH7, HepG2 and A431 cell transfections than analogous untargeted PEG-PEI polyplexes. Transfection levels can be further enhanced by treatment of cells with amphiphilic photosensitizers followed by illumination. In this process photosensitizers localized in membranes of endocytic vesicles are activated by light, resulting in the destruction of endocytic membrane structures and releasing co-endocytosed polyplexes into the cell cytosol. Photochemical enhanced gene expression was observed in all cell lines, with the magnitude of enhancement depending on the particular PEI polyplex formulation and cell line, ranging between 2- and 600-fold. Importantly, improved gene transfer retained EGF receptor specificity, as demonstrated by comparison with ligand-free polyplexes and by receptor antibody or ligand competition experiments. These results suggest that this combined procedure enables a dual mode of targeting polyplexes: biological targeting via EGFR interaction, combined with physical targeting with light to direct a photochemical delivery of therapeutic genes to a desired location.

Animals↗

PubMedDate not supplied

Gene carriers based on hexanediol diacrylate linked oligoethylenimine: effect of chemical structure of polymer on biological properties.

Two biodegradable polycations based on hexanediol diacrylate linked oligoethylenimine (OEI) were synthesized by applying different reaction temperatures, 20 degrees C (LT-OEI-HD) and 60 degrees C (HT-OEI-HD). Their structural properties were analyzed by NMR, FTIR, and SEC/MALLS (size exclusion chromatography coupled with multiangle laser light scattering detection). Reaction temperature strongly influenced molecular weight and ester/amide ratio and thus resulted in polycations with different biological activities and degradation profiles. LT-OEI-HD was an ester-based polycation of 8.7 kDa which degraded rapidly at pH 7 and pH 9 respectively. HT-OEI-HD had a molecular weight of 26.6 kDa, was mainly based on amides, and degraded more slowly than LT-OEI-HD. Both polymers mediated gene transfer as efficiently as linear polyethylenimine of 22 kDa in two cell lines while being less toxic at their optimal conjugate/plasmid (C/P) ratios. LT-OEI-HD needed higher C/P ratios for gene delivery; however, it was significantly less toxic than HT-OEI-HD.

Absorbable Implants↗