Construction of Minicircle Suicide Genes Coding for Ribosome-Inactivating Proteins.

Due to the lower risks of adverse effects, nonviral gene therapy is a suitable alternative to transfect cancer cells with a suicide gene to let them kill themselves by expressing toxic ribosome-inactivating proteins. Plasmids are stable and easy-to-produce vectors, but they have some disadvantages due to the bacterial backbone. Applying the minicircle technology, this problem can be solved with manageable effort in a well-equipped laboratory. With the described methodology, minicircle-DNA can be produced at low costs. The cell killing properties are monitored following transfection using the CytoSMART® Omni system-a camera based live cell imaging device.

Suicide nanoplasmids coding for ribosome-inactivating proteins.

Conventional eukaryotic expression plasmids contain a DNA backbone that is dispensable for the cellular expression of the transgene. In order to reduce the vector size, minicircle DNA technology was introduced. A drawback of the minicircle technology are considerable production costs. Nanoplasmids are a relatively new class of mini-DNA constructs that are of tremendous potential for pharmaceutical applications. In this study we have designed novel suicide nanoplasmid constructs coding for plant derived ribosome-inactivating proteins. The suicide-nanoplasmids were formulated with a targeted K16-lysine domain, analyzed for size, and characterized by electron microscopy. The anti-proliferative activity of the suicide-nanoplasmids was investigated in vitro by real time microscopy and the expression kinetic was determined using an enhanced green fluorescent protein nanoplasmid variant. In an aggressive in vivo neuroblastoma tumor model, treated mice showed a reduced tumor growth whereby the therapy was well tolerated.

An advanced method for the small-scale production of high-quality minicircle DNA.

Minicircle DNA is a promising tool in the field of gene therapy, whose products are increasingly gaining market access. Greater transfection efficiency and longer expression time as well as lower immunogenicity contrast with cost-intensive production, which also stands in the way of a broader use of the advantages of this technology in research. Starting from a commercial minicircle production kit a simple protocol for the cost-effective small-scale production of high-quality minicircle DNA to be used at a research scale has been developed by combining and improving procedures of various publications. An optimized size-exclusion chromatography method led to almost pure minicircle DNA with a superior proportion of the desired supercoiled plasmid conformation. The pharmaceutical potential of the produced minicircle DNA was investigated in vitro by real-time impedance assays in a tumor cell model in case of coded suicide genes as well as by ELISA of the translation product in case of coded human coagulation factor IX.

A new acetylated triterpene saponin from Agrostemma githago L. modulates gene delivery efficiently and shows a high cellular tolerance.

Transfection is the process to deliver nucleic acid into eukaryotic cells. Different transfection techniques already exist. However, they can be expensive and toxic toward subjected cells. Previous research shed light on natural occurring molecules called triterpene saponins that have great potential for the non-viral gene delivery. Using a combination of different chromatographic techniques and in vitro transfection bioassays, a new triterpenoid saponin (agrostemmoside E) from the plant Agrostemma githago L. was isolated. Agrostemmoside E was characterized by mass spectrometry, intense NMR spectroscopy and was identified as 3-{O-ß-D-Galactopyranosyl-(1→2)]-[ß-D-xylopyranosyl-(1→3)]-ß-D-glucuronopyranosyl} quillaic acid 28-O-{[ß-D-4,6-di-(O-acetyl)-glucopyranosyl-(1→3)]-[ß-D-xylopyranosyl-(1→4)]-α-L-rhamnopyranosyl-(1→2)}-[3,4-di-(O-acetyl)-ß-D-quinovopyranosyl-(1→4)]-ß-D-fucopyranoside ester. Agrostemmoside E has a great potential for delivery of gene loaded nanoplexes and increased the transfection efficiency by 70% compared to 2% without agrostemmoside E. By comparative toxicity studies, we show that agrostemmoside E can be applied at high concentrations without toxicity, justifying its use as a new tool for gene transfections.