Fig. 5. Photo-triggered release of Nile red from photoexpansile polymer 1 particles (P-1-NR). P-1-NR (0.08 mg mL^–1, 0.5 mL, total amount Nile red per sample: 2.25 μg) in PBS (1×, pH = 7.4) containing 1% w/v Pluronic® F127 were irradiated in ambient temperature with visible light (λ _ex = 400–500 nm, 0.18 W, 0.21 W cm^–2) or kept in the dark for the same time. (a) Changes in fluorescence intensity at 615 nm (n = 3). (b) Relative and actual amount of Nile red released from the same samples after 90 min of visible light irradiation (see ESI† for calculation). (c) Photographs illustrating Nile red (pink) release from the samples/controls in (a and b) after 90 min of irradiation and after centrifugation (S1–3 = irradiated samples, C1–3 = non-irradiated controls kept in the dark). (d) Changes in particle diameter upon irradiation with visible light (Multisizer; n = 3).