Retro-X Concentrator provides a fast, simple, and highly efficient method for concentrating any retroviral stock. You simply mix your retroviral supernatant with the Retro-X Concentrator reagent, incubate overnight, and spin the mixture in a standard centrifuge (Figure 1). You'll increase your vector titer by up to 100-fold and obtain excellent recoveries—without ultracentrifugation. Retro-X Concentrator works for all retroviral supernatants and pseudotypes, including those made from Takara Bio's Retro-X vectors. The procedure can be easily scaled up or down to suit your needs.

Efficient concentration of retroviral particles can be achieved using the Retro-X Concentrator protocol. Retroviral titers were concentrated from 10⁶ to 10⁸ IFU/ml, with very high recovery in 1/100 of the original volume. Up to 100-fold concentration was achieved for particles packaged with all common envelope proteins (VSV-G, ecotropic, and amphotropic pseudotypes) when concentrating them from 10 ml down to 100 µl (Figure 2).

In a side-by-side comparison between Retro-X Concentrator and ultracentrifugation, the advantages of Retro-X are clearly evident (Table I). Retro-X Concentrator is more flexible, faster, easier, and just as efficient as ultracentrifugation.

Table I. Retro-X Concentrator vs. ultracentrifugation