Polyrotaxanes bearing mixed cyclodextrin species and uses thereof

A polyrotaxane having the general formula:

• or salts thereof,
• wherein:
• each m, m′, n and n is, independently, an integer from 0 to 30, with the proviso that m+m′+n+n′ is from about 4 to about 30;
• C and C′ are the same or different and represent end capping groups of the formula:
• wherein each L2 is independently a bond or (C1-C6)acyl;
• each G3 is a steroid group;
• and each s is independently an integer from 1 to 6;
• B represents:
• to which the endcapping groups are covalently attached to B via a (C1-C6)hydrocarbylene group;
• wherein R5 is methyl;
• d is an integer from about 1 to about 800;
• and q is an integer from about 6 to about 800;
• and
• A and A′ each independently represent the macrocyclic host molecule of the general formula (I):
• wherein:
• A and A′ can be the same or different;
• x is an integer from 0 to 8;
• Z is O or NH;
• each R1 and R2 is, independently, hydrogen or a substituted or unsubstituted (C1-C6)hydrocarbyl group.