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. 2019 Jul 30;7:480. doi: 10.3389/fchem.2019.00480

Figure 1.

Figure 1

Variation of the size distributions of nanoparticles, human insulin, and nanoparticle–insulin complexes as estimated from the dynamic light scattering (DLS) spectra. (A) The DLS spectra of insulin protein alone (green), PEG-OH-modified CdSe/ZnS QDs with a core diameter of 3.1 nm (Table 1) alone (red), and a freshly prepared mixture of insulin with QDs (blue) recoded immediately after mixing of insulin and the QDs. Human insulin (2 mg/ml) was incubated in the presence of QDs (3.44 μM) in a 10 mM sodium phosphate buffer solution (pH 7.0) at 37°C. (B) The same QD–insulin mixture as in (A) where the DLS spectra were recorded after 0 (red), 5 (green), 10 (blue), 20 (black), and 30 min (magenta) of incubation. (C) The same QD–insulin mixture as in (A) where the DLS spectra were recorded after 0 (red), 12 (green), and 24 h (blue) of incubation. (D) Control experiment: a QD solution (3.44 μM) alone was incubated during 7 days in a 10 mM sodium phosphate buffer solution (pH 7/0) at 37°C. DLS spectra were recorded after 0 (red), 1 (green), 2 (blue), 3 (black), 4 (violet), 5 (rose), 6 (brown), and 7 (dark green) days of incubation. (E) Control experiment: a human insulin solution (2 mg/ml) alone was incubated in a 10 mM sodium phosphate buffer solution (pH 7.0) at 37°C, and the measurements were done at the same time points as in (D).