Preparation of 5 nm-sized CD nanoparticles
CDs were synthesized from ascorbic acid precursor through hydrothermal synthesis using a Teflon lined autoclave reactor. By varying the temperature and heating time—180°C for 6 hours, 180°C for 11 hours, 180°C for 20 hours, 180°C for 24 hours, 200°C for 24 hours, and 220°C for 48 hours—the particle size decreased from 480 nm to 128 nm, 82 nm, 53 nm, 5 nm, and finally 3 nm, respectively as shown in Figure 1. Heating the solution at 220°C for 48 hours produced stable nanoparticles with an average size of 3–5 nm. This CD sample was then used to investigate the interactions between the CDs and POPC phospholipid vesicles.
DLS for CD and POPC Phospholipid Vesicles
This work examines the interactions of CD nanoparticles with POPC phospholipid vesicles using DLS. The POPC phospholipid vesicles exhibited an average size of 360 nm, while the CDs exhibited an average size of 5 nm, as determined by DLS as shown in Figure 3. The size of the POPC phospholipid vesicles (360 nm) indicates that they are large unilamellar vesicles (LUVs). Upon mixing various concentrations of CDs with the POPC phospholipid vesicles, DLS data revealed significant size changes in the combined systems, depending on the POPC phospholipid-to-CD ratios (%v/v). At a 1:1 ratio, three peaks were observed at 17 nm, 53 nm, and 110 nm. However, at 1:5, 1:10, and 1:100 ratios, only one peak at 110 nm was observed. The peak intensity increased as the concentration ratio shifted from 1:5 to 1:10 and 1:100. This data supports the conclusion that CDs interact with and penetrate the phospholipid vesicles, localizing within vesicles. Additionally, the POPC vesicles, after interaction with the CDs, appeared to divide into smaller-sized vesicles.