Cyclodextrin

Cyclodextrins are a family of cyclic oligosaccharides, consisting of a macrocyclic ring of glucose subunits joined by α-1,4 glycosidic bonds.

[5] In most cases the mechanism of controlled degradation of such complexes is based on pH change of water solutions, leading to the loss of hydrogen or ionic bonds between the host and the guest molecules.

Alternative means for the disruption of the complexes take advantage of heating or action of enzymes able to cleave α-1,4 linkages between glucose monomers.

[8] The approval of powdered alcohol by the FDA in 2014 was met with wide-spread bans and backlash in the United States.

Because of this arrangement, the interior of the toroids is considerably less hydrophilic than the aqueous environment and thus able to host hydrophobic molecules.

[12] Purification of the three types of cyclodextrins takes advantage of the different water solubility of the molecules: β-CD which is poorly water-soluble (18.5 g/L or 16.3 mM at 25 °C) can be easily retrieved through crystallization while the more soluble α- and γ-CDs (145 and 232 g/L respectively) are usually purified by means of expensive and time consuming chromatography techniques.

The complex formation drives the conversion of starch towards the synthesis of the precipitated cyclodextrin, thus enriching its content in the final mixture of products.

MβCD is employed for the preparation of cholesterol-free products: the bulky and hydrophobic cholesterol molecule is easily lodged inside cyclodextrin rings.

[15] Due to the covalent attachment of thiol groups to cyclodextrins high mucoadhesive properties can be introduced as these thiolated oligomers (thiomers) are capable of forming disulfide bonds with cysteine-rich subdomains of mucus glycoproteins.

The cellular uptake of various model drugs, for instance, was up to 20-fold improved by using thiolated α-cyclodextrin as carrier system.

[20][21] Complexes formed between β-cyclodextrin and adamantane derivatives have been used to make self-healing materials, such as hydrogels[22] and low-friction surfaces.

For 25 years, between 1911 and 1935, Hans Pringsheim in Germany was the leading researcher in this area,[28] demonstrating that cyclodextrins formed stable aqueous complexes with many other chemicals.

Since the 1970s, extensive work has been conducted by Szejtli and others exploring encapsulation by cyclodextrins and their derivatives for industrial and pharmacologic applications.

[1] Nevertheless, attempts to use β-Cyclodextrin for the prevention of atherosclerosis,[31] age-related lipofuscin accumulation[32] and obesity encounter an obstacle in the form of damage to the auditory nerve[33] and nephrotoxic effect.