Reverse gene polarity

By reversing the polarity of the DNA strands, the opposite strand will be transcribed and a complementary or antisense RNA will be produced. When antisense RNA was introduced either in vitro (27) or in vivo (28), the presence of the antisense RNA inhibited the expression of the normal RNA transcript produced by the resident gene. Suppression of RNA translation by antisense RNA may be due to the formation of an RNA heteroduplex between the two complementary RNA strands thus blocking the attachment of ribosomes. An example of this application in the context of the Adh example would be the construction of a chimeric gene containing the antisense sequence for Adh linked with a female-specific promoter. Thus, Adh activity would be eliminated from females and make them lethally sensitive to treatment with ethanol. 

Dextran can be modified easily and cationic derivatives are obtained by reaction with diethylaminoethyl (DEAE) reagents or spermine. DEAE-dextran is one of the pioneer cationic polymers for gene delivery. However, PLL and other synthetic polymers have replaced dextran these days because of low transfection efficiency and toxicity problems of DEAE-dextran. Spermine-dextran (MW 9000-11 000 g mol ) is used as an siRNA delivery agent to cancer cells, with low toxicity and high loading capacity on HeLa-Zwc cells, and was proved to be a safe and effective acid-sensitive carrier for gene delivery by Cohen et al. Researchers showed that cationic dextran derivatives (MW 70 kDa) have also reverse tumor-associated macrophage (TAM) polarization, promote IL-12 expression in tumor TAMs and thereby enhance the tumoricidal capacity of TAMs. ... 

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