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Structure:
Cyclodextrins are a class of cyclic glucopyranose oligomers, with common structures of α, β, and γ. Α-cyclodextrins comprise six glucopyranose units, β- cyclodextrins comprise seven, and γ comprise eight. Cyclodextrins are biological nanomaterials whose molecular structure greatly influences their supramolecular properties. To synthesize cyclodextrins, enzymatic action occurs on hydrolyzed starch.

Cycodextrin nanosponges are made of a three dimensional cross-linked polymer network. They can be made with α, β, and γ cyclodextrins. The inclusion capacity and the solubilizing capacity of the nanosponges can be tuned according to how much of the cross-linking agent is used.

Functions:
Cyclodextrins have a toroidal shape, which allows them to have a cavity inside which can fit other molecules. This useful structure allows them to act as drug carriers in the body, as long as the compounds to be delivered have compatible geometry and polarity with the cavity. To determine when these compounds are delivered, the structure of the cyclodextrin nanosponge can be modified to release its contents sooner or later. Several ligands can be conjugated on the surface of the nanosponge to determine where it will target in the body.

History
Nanosponges were first referred to as “cyclodextrin nanosponges” by DeQuan Li and Min Ma in 1998. This term was used because there is a cross-linked β-cyclodextrin with organic diisocyanates. An insoluble network is present in this structure, which shows a high inclusion constant. These polymers are formed through the reaction of native cyclodextrins with a cross-linking agent, the latter influencing the behavior and properties of the entire unit.

Cyclodextrin nanosponges were not discovered to have potential in being drug carriers until work done by Trotta and colleagues. They performed syntheses of new kinds of cyclodextrin nanosponges that revealed many potential applications that had not been previously considered.

Treating Ischemic Strokes
Mn3O4@nanoerythrocyte-T7 (MNET) nanosponges can regulate oxygen and scavenge free radicals in the event of an ischemic stroke, which is a global leading cause of death and disability. These engineered nanosponges can help attenuate hypoxia after a stroke by increasing the amount of oxygen in the infarct area. This allows for the extension of the survival time of neurocytes, a crucial part of treating an ischemic stroke because their normal functions must be maintained.

MNET works because the hemoglobin present in MNET allows there to be an oxygen sponge effect. This effect works by releasing oxygen in hypoxic areas and absorbing it in oxygen-rich areas. The sponge effect, along with the free radical scavenging, can successfully treat ischemic strokes.

Biomimetic nanoparticles, like MNET nanosponges, can easily pass the Blood-Brain Barrier (BBB). The efficiency of the BBB-crossing of MNE is improved by the T7 peptide, which is critical in treating an ischemic stroke. In a study on MCAO rats, those treated with MNET experienced a significant attenuation of neurological damage.