Figure 3.

Toxicity of diamond nanoparticles to HUVEC depends on cell density and surface conjugation of nanoparticles. (A) HUVEC 48-h proliferation was analysed for untreated cells (“C”) or cells treated with NDs (“ND”, “-RGD -FBS”) and NDs conjugated with a peptide containing an RGD motive (Gly-Arg-Gly-Asp-Ser; “ND”, “+RGD”) and at concentrations of 5 and 50 mg/l in standard HUVEC culture medium and in medium with the addition of 10% FBS (“+FBS”). Statistical significance is indicated with different superscripts: P<0.001 (a, b, c, d, e) (ANOVA; P < 0.05; n = 3 with 4 individual replicates). (B) Dependence of ND toxicity on HUVEC cell density was assessed in a 96-well plate at densities of 5 x 10³, 1 x 10⁴, 1.5 x 10⁴, and 2×10⁴. After 24-h incubation, cells were treated with NDs at a concentration of 0.4 ng/cell (the final ND concentration was 20, 40, 60, and 80 mg/L in 100 µL medium, respectively), and the metabolic activity was assessed. The relative toxicity of HUVEC was expressed as the ratio of the metabolic activity value of the ND-treated cells to the metabolic activity of the untreated cells. Statistical significance is indicated with different superscripts: P<0.001 (a, b, c, d) (ANOVA; P < 0.05; n = 3 with 6 individual replicates). All values are expressed as mean ± standard deviation. (C) HUVEC time-lapse images of a 12-h cell culture with NDs at a final concentration of 20 mg/l. The full video of time-lapse images is available as Supplementary Video. Abbreviations: RV, relative value; FUs, fluorescent units; C, control; NDs, diamond nanoparticles; RGD, Gly-Arg-Gly-Asp-Ser peptide; FBS, fetal bovine serum. (D) HUVEC spheroid morphology after 24-h treatment with NDs at a concentration of 10 and 100 mg/l. HUVEC spheroid membrane perforation (E) and spheroid size (F) for a after 24-h incubation with NDs at a concentration of 5, 10, 20, 50, and 100 mg/l. Statistical significance is indicated with different superscripts:: P<0.001 (a, b, c) (ANOVA; P < 0.05; n = 3 with 6 individual replicates).