Fig. 2. P-2 photocage–drug conjugate nanoparticles dissolve and release drug upon red light irradiation. (a) Scheme illustrating the general preparation, composition and photochemistry of the P-2 nanoparticles. (b) UV-vis absorption spectra of P-2 (2: 0.1 mM, 1 mL) in water containing 1% w/v poloxamer 407 before irradiation (purple trace), after 7.5 min irradiation (black trace, λex > 590 nm, 183 mW, 65 mW cm–2) and after 10 min incubation at 37 °C (red trace). The red shaded area highlights the red light region of absorption for P-2. (c) Kinetics of the same P-2 sample upon irradiation with red light. (d) P-2 particle size as measured by DLS before irradiation (purple trace), after 7.5 min irradiation (black trace) and after 10 min incubation at 37 °C (red trace). (e) HPLC chromatogram of separated and silica gel filtered (EtOAc) pellet and supernatant of irradiated and non-irradiated control samples. (f–h) Photographs of P-2 samples (S: irradiated, C: not irradiated) (f) before irradiation, (g) after 7.5 min irradiation (tube S), and (h) after incubation (10 min) and centrifugation (the red circle highlight the centrifuged pellet). (i–j) SEM images of centrifugation-washed P-2 pellets (i) without irradiation (inset in (i) is a magnification) and (j) after 7.5 min irradiation and 10 min incubation.
