In all comparative studies between CsCl and iodixanol, the recovery of virus infectivity is much higher and the particle:infectivity ratio much lower when viruses are purified in iodixanol. 

Although sucrose is generally less deleterious to viral infectivity than CsCl, it can nevertheless also have serious effects on certain important aspects of viral function; in particular the loss of surface glycoproteins from retroviruses has been noted [1]. This may be related to its viscosity, which, in solutions of the same density, is much higher than that of iodixanol. 

Most iodixanol gradients can also be made isoosmotic over the entire density range. Like CsCl, sucrose must be dialyzed before infectivity can be measured. In contrast both infectivity measurements using cultured cells and many add-on techniques can be performed without dialysis of iodixanol. 

Combined with the availability of OptiPrep as a sterile solution, this makes the use of OptiPrep for virus purification and assembly analysis much more convenient than the use of either CsCl or sucrose. Thus iodixanol is being increasingly used for hepatitis C virus particle purification from lysed cultured cells, conditioned culture medium or plasma samples from patients.