**5. Applications in smart drug delivery**

#### **5.1 Improving solubility and controlled release of drugs**

#### *5.1.1 CD-based polyurethane NSs*

Another study showed the capability of CD polyurethane to reduce the levels of natural product contaminants, particularly, Ochratoxin A (OTA) from spiked solutions between 1 and 10 μgL-1 [61]. Following the attracted considerable interest that these polymers have shown in their use for water purification systems [62] and drug delivery [63], there were further done several chemical modifications on the CD NSs. Even though the modified CD NSs were used to enhance the properties and usefulness of CD NSs, their characterization at the molecular level remained a challenge. Therefore, a study described the structural characterization at the molecular level of both, native CD nanosponge polyurethanes and bionanosponge polyurethane cyclodextrin nanocomposite (pMWCNT-CD/Ag-TiO2) showing a great antibacterial and antifungal activity. The greatest antimicrobial activities were in the case of the developed polyurethane nanocomposite (pMWCNT-CD/

Ag-TiO2). Consequently, it was concluded that this developed synthesis can be considered an active antimicrobial compound [64]. Another potential application of CD polyurethane polymer is as immobilization supports in enzyme catalysis. The lipase was immobilized into the aforementioned polymers via physisorption. It is observed an improvement in the stability and catalytic activity of lipase, knowing that the enzymes are generally unstable, insoluble in organic solvents, and sensitive. Accordingly, this study presented the chance to prepare immobilized biocatalysts with tunable catalytic activities attributed to the alteration of reaction conditions [65]. Further research was focused on the novel polyurethanes containing simultaneously β-cyclodextrin (β-CD), β-glycerophosphate groups, and hexamethylenediisocyanate (HDI). This polymer developed was used to complex the delivering therapeutic agents such as antibiotic ciprofloxacin. It was observed an improvement of the drug release in the case of the drug-polymers complexation than that of the free drug [63].
