Zetasizer nano zs nanoparticle size analyzer

The chemical structure of the dual-targeting dendrimer was characterized by ¹H NMR measurement on AVANCE III HD 400 MHz spectrometer (Bruker, USA) using D₂O as solvent. ¹H NMR (D₂O, 400 MHz, ppm): δ 2.25-2.40 (-CH₂CH₂CONH-); δ 2.45-2.55 (-CH₂CH₂N<); δ 2.68-2.74 (-NCH₂CH₂CO-); δ 2.95-3.20 (-CONHCH₂CH₂- and -CH₂CH₂NH₂); δ 3.32-3.75 (-CH₂CH₂O-); δ 6.79 (-COCH=CHCO-); δ 3.30 (-OCH₃). Size distribution and zeta potential of the dendrimer-based carriers were measured by Zetasizer Nano ZS nanoparticle size analyzer (Malvern Instruments Ltd., UK) at a concentration of 0.1 mg/mL in PBS. The samples were sonicated for 3 min and filtered with 200 nm filter membrane before detection. Morphological characterization of the dendrimer-based carriers was performed on a Ht-7700 transmission electron microscope (Hitachi, Japan) at acceleration voltage of 80 KV. TEM samples were made by dropping 2.5 μL samples (1 mg/mL) on carbon-coated grids and deposited for 30 min. Then the samples were negative stained by 1 wt% uranyl acetate for 25 s before test. Stability of the dual-functional dendrimer in water and PBS was detected by DLS within 72 h. Briefly, the samples were dissolved into deionized water and PBS at a concentration of 1 mg/mL. Then the particle size was detected by a Zetasizer Nano ZS nanoparticle size analyzer at 0 h, 12 h, 24 h, 48 h and 72 h.

PL and UV-vis absorption spectra were characterized by Horiba Duetta. The time-resolved PL spectra were obtained with a Horiba FluoroMax with a 455 nm laser. A transmission electron microscopy (TEM) image was performed by using a Japan Hitachi HT7700. The Raman spectrum was achieved by an Anton-Paar Cora 5001 with 785 nm of laser wavelength. The Fourier transform infrared (FT-IR) spectrum was characterized with a Thermo Scientific iS50 FT-IR. The X-ray photoelectron spectroscopy (XPS) spectrum was acquired using a Thermo ESCALAB 250Xi spectrometer. Dynamic light scattering (DLS) is a powerful tool used to monitor particle size evolutions. Aβ_1–42 peptides were mixed with 6 mg/mL N-CDs incubated for 24 h at 37 °C and then the size distribution was measured by a ZetasizerNano ZS nanoparticle size analyzer (Malvern Instruments Ltd., Malvern, UK). Aβ_1–42 solutions incubated with PBS were also utilized as controls. After measuring the effect of N-CDs on Aβ_1–42 fibrosis by ThT and DLS as shown previously, the morphologies of the Aβ_1–42 aggregates incubated with or without N-CDs were observed and visualized by TEM (Japan Hitachi HT7700, Japan, Tokyo).