Background: During functional studies on the rat stress-inducibleHspa1b(hsp70.1) gene we noticed that some liposome-based DNA carriers, which are used for transfection, induce its promoter activity. This observation concerned commercial liposome formulations (LA), Lipofectin and Lipofectamine 2000. This work was aimed to understand better the mechanism of this phenomenon and its potential biological and practical consequences.Results: We found that a reporter gene driven byHspa1bpromoter is activated both in the case of transient transfections and in the stably transfected cells treated with LA. Using several deletion clones containing different fragments ofHspa1bpromoter, we found that the regulatory elements responsible for most efficient LA-driven inducibility were located between nucleotides -269 and +85, relative to the transcription start site. Further studies showed that the induction mechanism was independent of the classical HSE-HSF interaction that is responsible for gene activation during heat stress. Using DNA microarrays we also detected significant activation of the endogenousHspa1bgene in cells treated with Lipofectamine 2000. Several other stress genes were also induced, along with numerous genes involved in cellular metabolism, cell cycle control and pro-apoptotic pathways.Conclusions: Our observations suggest that i) some cationic liposomes may not be suitable for functional studies onhsppromoters, ii) lipofection may cause unintended changes in global gene expression in the transfected cells.

Silk fibroin is a biocompatible, non-toxic, mechanically robust protein, and it is commonly used and studied as a material for biomedical applications. Silk fibroin also gained particular interest as a drug carrier vehicle, and numerous silk formats have been investigated for this purpose. Herein, we have prepared electrospun nanofibers from pure silk fibroin and blended silk fibroin/casein, followed by the incorporation of an anti-inflammatory drug, diclofenac. Casein serves as an excipient in pharmaceutical products and has a positive effect on the gradual release of drugs. The characteristics of the investigated composites were estimated by scanning electron microscope, transmission electron microscope, thermogravimetric analysis, and a lifetime of diclofenac by electron paramagnetic resonance analysis. The cumulative release in vitro of diclofenac sodium salt, together with the antiproliferative effect of diclofenac sodium salt-loaded silk nanofibers against the growth of two cancer cell lines, are presented and discussed.