Fig. 5. (a) The NIH/3T3:4T1 tumor spheroids in 1 mL Hank's buffered salt solution (HBSS) under 794 nm laser irradiation (photo by Ping-Lin Yang). Inset (up): a modified 1 mL cuvette for photolysis experiment of cancer spheroids. Inset (down): the scheme represents that the spheroids can be placed at the corner of the cuvette and exposed to NIR laser excitation. (b) Up: NO released from five spheroids infiltrated with bone marrow macrophages loaded with PLGA microparticles containing I and Nd-UCNPs under 794 nm laser irradiation with 13.1 W cm^–2. Down: the control experiment of six spheroids loaded with PLGA microparticles. (c) Plot of NO detected vs. irradiation time. (d) The viability of spheroids after 6, 12, or 18 min of laser exposure in 6 min increments. Viability was measured using a PNPP assay 24 h after spheroid treatment. *p ≤ 0.05 (Students t-test).