Fig. 3

(a) The thermographic images of water and UGs@PEG (200 µg mL^− 1) with laser irradiation for 5 min (1064 nm, 1.0 W cm^− 2). (b) In vitro temperature rising curves of UGs@PEG at different concentrations (0, 50, 100, 150 and 200 µg mL^− 1) and (c) at different irradiation power (0.5, 1.0, 1.5 and 2.0 W cm^− 2) (n = 3). (d) Linear time vs.–ln(θ) was obtained from the first cooling period. (e) The cell viability of MCF-10 A and L929 cells treated with UGs@PEG at different concentrations of (1, 2, 4, 8, 16, 32, 64, and 128 µg mL^− 1) for 24 h. (f) The 4T1 cell viability after being treated with UGs@PEG with or without NIR light at different concentrations (0, 1, 2, 4, 8, 16, 32, and 64 µg mL^− 1). (g) The bio-TEM images for cell uptake of UGs@PEG (50 µg mL^− 1) in 4T1 cells at 0, 4, and 8 h, scale bar: 2 µm (top) and 0.2 µm (bottom). (h) The cell apoptosis analysis results of 4T1 cells after different treatments obtained by flow cytometry (Q1: necrotic cells; Q2: secondary necrotic/late apoptotic cells; Q3: early apoptotic; Q4: vital cells)