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Figure 4. Evaluation of the uptake, cell viability effect, and anti-pigmentation efficacy of RS-EVLP in B16 mouse melanoma cells. (A) Quantitative flow cytometry analysis of B16 cell uptake after treatment with different RS-EVLP concentrations (4.6 and 23 µg/mL) for different times (2, 4, and 8 h); (B) Fluorescence microscopy images (scale bar: 50 µm) of B16 cell uptake after treatment with different RS-EVLP concentrations (4.6 and 23 µg/mL) of RS-EVLP for different times (2, 4, and 8 h); (C) The effect of different RS-EVLP concentrations on B16 cell viability; (D) Morphological microscopic images of melanogenesis in B16 cells stimulated by α-MSH, the positive control Arb, and RS-EVLP treatments at different concentrations (0.23, 4.6, and 23 µg/mL); (E and F) Quantitative analysis of (E) melanin content and (F) tyrosinase activity in B16 cells under the same treatment conditions. Data are shown as mean ± SEM from three independent biological replicates (n = 3). Statistical significance was determined by one-way ANOVA followed by Tukey’s multiple comparisons test (vs. control group): ^*P < 0.05; ^**P < 0.01; ^***P < 0.001. ANOVA: Analysis of variance; Arb: arbutin; α-MSH: α-melanocyte-stimulating hormone; DAPI: 4’,6-diamidino-2-phenylindole; FITC: fluorescein isothiocyanate; NC: negative control; RS-EVLP: rose-derived extracellular vesicle-like particles; SEM: standard error of the mean.