2.1. Materials and Methods
Beta-CD, dimethyl sulfoxide (DMSO), and 2-iodoxybenzoic acid (IBX) were purchased from ENERGY-CHEMICAL (Shanghai, China). Copper (II) hydroxide (Cu(OH)₂), cystamine, sodium acetate, methanol (MeOH), and doxorubicin (DOX) were obtained from Aladdin Corporation (Shanghai, China).1H NMR analyses were carried out using a Bruker ADVANCE 400 MHz Spectrometer (Germany). FTIR measurements were conducted in transmission mode at room temperature, covering the range of 400 to 4000 cm⁻¹. AFM was performed in tapping mode using a Bruker Dimension ICON, with a scan rate of 1 Hz and a scan size of 1 μm × 1 μm. Size distribution was analyzed using a ZEN 3600 dynamic light scattering (DLS) instrument from Malvern.
2.2 Synthesis of aldehyde group functionalized beta-CD
Beta-CD (11.35 g, 10 mmol) was dissolved in 20 ml of DMSO and stirred until the solution became clear. The oxidizing agent, IBX, was gradually added to the solution at a reaction temperature of 40 °C. Fresh Cu(OH)₂ was used to detect the presence of aldehyde groups. The reaction progress was monitored by thin-layer chromatography (DCM: MeOH = 20:1). After 48 hours, the reaction mixture changed from a colorless, transparent liquid to a white, turbid liquid, indicating completion. The resulting solution was poured into water and vacuum filtered to remove excess IBX and water-insoluble solids. The filtrate was then transferred to a dialysis bag (MWCO 500) and dialyzed in water for three days. Finally, the product was freeze-dried to yield a white solid (6.62 g, 58%) for further use.