in vivo RNAi Frequently Asked Questions

For answers to additional questions, please refer to the Invitrogen’s technical support FAQ database or contact Invitrogen Technical Support to have a representative assist you.

Q. Should I use chemically modified duplexes for my in vivo RNAi experiments?
A. Chemically modified Stealth RNAi™ siRNA duplexes have a number of advantages over standard RNAi duplexes, including the minimization of off-target effects, enhanced stability, and reduced toxicity. For these reasons, Stealth™ chemically modified RNAi duplexes are recommended for in vivo RNAi experiments. For some pilot experiments, where the only aim is to determine biodistribution, BLOCK-iT™ duplexes and fluorescent controls are useful and slightly more cost-effective.

Q. Should I use labeled or unlabeled duplexes for my in vivo RNAi experiments?
A. We have demonstrated that labeling Stealth RNAi™ siRNA duplexes does not hamper their knockdown potency. An alternative approach is to mix unlabeled duplexes with labeled control duplexes; this method is more commonly used with in vivo RNAi, and allows progression to clinical research unhindered by questions about the possible effects of a dye.

Q. I am planning on using siRNA for my in vivo experiments, what purity should they be?
A. Invitrogen’s production of in vivo RNAi duplexes begins with standard synthesis of RNAi oligos using high-quality starting materials. The RNA oligos are then duplexed and desalted. At this point, the researcher can also request HPLC purification. However, this step increases cost and reduces yield. Subsequent in vivo-purity processing subjects the duplexes to a series of dialysis and counterion exchange steps to remove toxic salts and solvents and lower the conductivity to physiological conditions. The resulting high-quality duplexes are ready for in vivo use regardless of whether HPLC purification is requested upstream of this process.

Q. Should I use siRNA or vectors for in vivo RNAi?
A. RNAi can be delivered using two different approaches-siRNA synthetic duplexes or siRNA expressed from plasmids or viral vectors (shRNA, miRNAi). siRNA are becoming the method of choice for the fast development of therapeutics. They are easy to use, easy to design, and easy to synthesize. siRNA can be rapidly identified and multiple genes can be targeted at the same time. With RNAi vectors, the expression will be steadier as a result of the possibility of stable integration of the plasmid into the genome, and they have the ability to target nondividing cells such as stem cells, lymphocytes and neurons. The drawbacks are the danger of oncogenic transformation from insertional mutagenesis, and unanticipated toxicity from long-term silencing of human genes and/or having high amounts of siRNA inside the cell (Grimm D. et al.: Nature 441: 537-541 (2006)).

Click for more information siRNA synthetic duplexes or siRNA expressed from plasmids or viral vectors (shRNA and miRNAi).

Q. How should I deliver my in vivo RNAi molecules?
A. Several different approaches have been used for siRNA delivery, including various local delivery techniques and systemic delivery. Click to learn more.

Q. How many µg or mg are delivered of  the nmole quantities of  synethic duplexes offered by Invitrogen for in vivo RNAi? 
A. Table 1 provides nmole quantities in µg and mg.

Table 1-Quantities Delivered in µg and mg

Q. Do I need endotoxin testing for my in vivo RNAi duplexes?
A. Please check with your governing regulatory agency for guidance.

Q. How can I order in vivo RNAi duplexes?
A. RNAi duplexes for in vivo experiments can be ordered using the simple BLOCK-iT™ RNAi Express for in vivo synthetics.

Q. How much is the price per duplex of the in vivo RNAi duplex I wish to purchase?
A. Pricing is calculated in the following manner: Click to display pricing information by country.

Duplex Price = (purity price) + (price per base for chosen scale x quantity of bases) + (optional 5' sense strand label) + (optional endotoxin testing)
NOTE: BLOCK-iT™ has 42 bases. Stealth RNAi™ siRNA has 50 bases.