Localized transfection with magnetic beads coated with PCR products and other nucleic acids

An Overview of Methods and Tools for Transfection of Eukaryotic Cells in vitro

Transfection is a powerful analytical tool enabling studies of gene products and functions in eukaryotic cells. Successful delivery of genetic material into cells depends on DNA quantity and quality, incubation time and ratio of transfection reagent to DNA, the origin, type and the passage of transfected cells, and the presence or absence of serum in the cell culture. So far a number of transfection methods that use viruses, non-viral particles or physical factors as the nucleic acids carriers have been developed. Among non-viral carriers, the cationic polymers are proposed as the most attractive ones due to the possibility of their chemical structure modification, low toxicity and immunogenicity. In this review the delivery systems as well as physical, biological and chemical methods used for eukaryotic cells transfection are described and discussed.

A novel method for cloning of coding sequences of highly toxic proteins

BACKGROUND

During standard gene cloning, the recombinant protein appearing in bacteria as the result of expression leakage very often inhibits cell proliferation leading to blocking of the cloning procedure. Although different approaches can reduce transgene basal expression, the recombinant proteins, which even in trace amounts inhibit bacterial growth, can completely prevent the cloning process.

METHODS

Working to solve the problem of DNase II-like cDNA cloning, we developed a novel cloning approach. The method is based on separate cloning of the 5' and 3' fragments of target cDNA into a vector in such a way that the short Multiple Cloning Site insertion remaining between both fragments changes the reading frame and prevents translation of mRNA arising as a result of promoter leakage. Subsequently, to get the vector with full, uninterrupted Open Reading Frame, the Multiple Cloning Site insertion is removed by in vitro restriction/ligation reactions, utilizing the unique restriction site present in native cDNA.

RESULTS

Using this designed method, we cloned a coding sequence of AcDNase II that is extremely toxic for bacteria cells. Then, we demonstrated the usefulness of the construct prepared in this way for overexpression of AcDNase II in eukaryotic cells.

CONCLUSIONS

The designed method allows cloning of toxic protein coding sequences that cannot be cloned by standard methods.

GENERAL SIGNIFICANCE

Cloning of cDNAs encoding toxic proteins is still a troublesome problem that hinders the progress of numerous studies. The method described here is a convenient solution to cloning problems that are common in research on toxic proteins.

Raster image cross-correlation analysis for spatiotemporal visualization of intracellular degradation activities against exogenous DNAs

Reducing intracellular DNA degradation is critical to enhance the efficiency of gene therapy. Exogenous DNA incorporation into cells is strictly blocked by the defense machinery of intracellular nuclease activity. Raster image correlation spectroscopy (RICS) and raster image cross-correlation spectroscopy (cross-correlation RICS; ccRICS) are image-based correlation methods. These powerful tools allow the study of spatiotemporal molecular dynamics. Here we performed spatiotemporal ccRICS analyses of fluorescent DNA and directly monitored the process of exogenous DNA degradation in living cell cytoplasm. Such direct monitors of DNA degradation allow us to determine the fate of the exogenous DNA in living cells. On comparing the process in living cells, our study shows that cytoplasmic nuclease activity differs between cell lines; therefore, we propose that the difference of nuclease activity in cytoplasm dictates a different resistance to exogenous DNA incorporation. New insight on efficient gene delivery can be provided with our study.

Magnetically deliverable calcium phosphate nanoparticles for localized gene expression

Iron oxide doped tricalcium phosphate nanoparticles can be used to achieve a spatially controlled green fluorescent gene delivery without using potentially cytotoxic agents.