## 2 Native Cyclodext
### Structural Modifications and Derivative Synthesis  
The traditional method for forming cyclodextrin derivatives involves treating pure cyclodextrin (CD) with substances that introduce active sites to the hydroxyl molecules of the glucose components via esterification or methylation processes [11; 21]. Methylation is the process of substituting the hydroxyl units on the CD chains with methyl groups, leading to modified compounds like methyl-beta-cyclodextrintrin (M-\(\beta\)-CD), dimethyl-beta-cyclodextrintrin (DIMEB), and randomly methylated beta-cyclodextrintrin (RAMEB) [11]. Certain derivatives, such as hydroxypropyl-\(\beta\)-cyclodextrintrin (HPBCD), are employed in soil remediation applications. Chemically modified cyclodextrins exhibit improved efficacy and precipitation characteristics, making them excellent materials for the cleanup of a variety of pollutants [9; 20; 21].  
This method efficiently elevates the bioavailability and solubility of insoluble substances by creating inclusion complexes with them [11].  
Hydroxypropy! \(\beta\)-cyclodextrintrin is a modified derivative with hydroxypropyl groups, which significantly enhance its water solubility, thus making it appropriate for applications that necessitate aqueous environments [9; 11]. RAMEB is useful for eliminating persistent organic pollutants because of its strong interactions with hydrophobic substances. It may be applied to microbiological and phytoremediation in addition to other remediation techniques [21].  
Methylated cyclodextrins alter the physicochemical features of CDs, such as solubility and strength, broadening their applications in countless sectors, like medicine and food [9; 11; 21]. Research reveals that \(\beta\)-CD effectively removes organic contaminants, including antibiotics, dyes, and pharmaceutical residues [22]. Carboxymethyl-\(\beta\)-cyclodextrintrins are modified to selectively bind with metal ions like Cd, Hg, and Pb. They are effective in treating industrial waste sites and mining regions with heavy-metal impurities that pose a substantial hazard to the environment and human health [11; 22]. A \(\beta\)-CD nanocomposite has shown high catalytic activity for reducing Rhodamine B (RhB) and photodegrading methylene blue (MB).  
Additionally, a chitosan-\(\beta\)-cyclodextrintrin polymer has demonstrated outstanding adsorption ratios for pharmaceutical pollutants, with ibuprofen and progesterone deduction competencies of 75% and 90%, respectively. A cyclodextrin-acrylic acid-acrylamide modification successfully adsorbs toxic element ions, including Cu\({}^{2+}\), Cd\({}^{2+}\), and Pb\({}^{2+}\). Furthermore, a cross CD-hectorite nanomaterial promotes simultaneous heavy-metal exclusion and organic contaminants, indicating a synergistic impact [22]. Lastly, the sulfobutyricther \(\beta\)-cyclodextrintrin derivative is commonly used in pharmaceuticals to improve the water  
Figure 3: A schematic diagram of three native cyclodextrin cavity sizes (5.3–4.7 Å for \(\alpha\)-CD; 6.5–6.0 Å for \(\beta\)-CD; and 8.3–7.5 Å for \(\gamma\)-CD) [15].  
solubility of \(\beta\)-cyclodextrintrin, making it suitable for pharmacological formulations, especially for treatments with low water solubility [9; 11]. Deciding which derivative to use depends on the specific application. This facilitates the removal of these metals from contaminated sites and shows their capability to bind harmful substances, allowing for their retrieval and stabilization in water and soil environments [11; 23].