MELT™ Total Nucleic Acid Isolation System From Ambion

Extracting RNA from tissues can be a painstaking process, often involving loss of tissue during homogenization steps, which results in decreased RNA yield. Luckily for researchers, Ambion makes the MELT™ Total Nucleic Acid Isolation System. The MELT™ kit from Ambion extracts RNA from tissues using a "homogenization-free" method. It does this by combining a cocktail of digestive enzymes with steady shaking in a vortex adapter. Following the enzyme digestion, magnetic beads bind RNA, and the beads are washed and subjected to an optional DNase digestion.

I have used this kit for the digestion of murine aorta tissue, which is very fibrous and, when stripped of all excess connective tissue and fat, is a rather small piece of tissue. Before trying this kit, I would homogenize a mouse aorta in Tri-Reagent with a Dounce or Polytron homogenizer, followed by RNA clean-up using a spin column kit. Using this method, I would get roughly 1 ug of RNA, which can be a very small amount, depending on the application requiring the RNA. However, when using the MELT™ kit with an aorta the same size, the yield is about 6 ug. Furthermore, I have analyzed the purity and quality of the RNA attained using this kit (including the DNase digestion step) with an Agilent Bioanalyzer, and have found the quality to be excellent (RNA Integrity Number, or RIN, greater than 8).

The strengths of this kit include the need for only a small amount of starting tissue (<10 mg) as well as no risk of losing any tissue in the homogenizer. Therefore, this kit is ideal for experiments where the starting material is very limited. There is also no need to clean messy homogenizers or to deal with smelly phenolic compounds (e.g. Tri-Reagent). The kit also produces very pure RNA with high quality, so there is no risk of losing RNA during clean-up steps, and it is great for applications requiring extra-pure RNA. After the "homogenization" step, the homogenates can be stored at room temperature for up to 6 days, which provides flexibility in the procedure.

Despite these advantages, the kit is not perfect. The digestive enzymes don't always digest all the tissue, but this largely depends on how fibrous the tissue is and is more likely when more than 10 mg of tissue is used. During the bead binding step, I recommend using low-retention pipette tips, as the beads form clumps and can stick inside the pipette. The vortex adapter and magnetic stand are extra products that are needed, and thus, if you don't already have them, they will add extra cost to the kit. The kit itself is a bit pricey, but when compared to using homogenizers, Tri-Reagent, and a spin column kit for cleanup, the price is similar.

Overall, the simplicity of this kit and its consistently outstanding results make it an excellent product.