The driving force and stability of hydroxypropyl beta cyclodextrin

Major driving force for the formation of inclusion complex is HP-B-CD cavity water molecules released rich enthalpy. Because in the water, the water molecules form hydrogen bonds in HP-B-CD cavity lipophilic tendencies are not met, so it has higher heat content than the water molecules in the solution, the water molecules in the cavity by guest molecules in solution more lipophilic or its lipophilic structure after contact nonpolar bonds polar bond and HP-B-CD guest molecules, the ring tension decreased, can make the whole system is in a stable state, so the HP-B-CD is very suitable for the inclusion of lipophilic drugs. If the size of the molecule is smaller than the water, it is possible to form a inclusion complex with the HP-B-CD if the size of the HP-B-CD is matched with the cavity size of the cavity.

The stability of the inclusion complex depends mainly on the size of the van Edward force between the drug and the HP-B-CD molecule in the inclusion complex. Once the drug molecules enter the cavity of the HP-B-CD, they will automatically adjust the configuration to use the existence of the van Edward force as much as possible. In addition, the stability is also related to the structure, size, proportion and polarity of the two. The inclusion complex has a dynamic balance with the free HP-B-CD and the drug, and the stability constant Kc or the binding constant K is an important parameter to measure the stability of the inclusion complex.