Figure 5: In vivo photoacoustic imaging of a tumour-bearing mouse.

(a) An image of a subcutaneous prostate tumour in the right thigh of a mouse. (b) Ultrasound image of the tumour for image co-registration. (c) Photoacoustic image 24 h after nanoparticle injection shows the tumour, and blood vessels near the tumour (yellow box). (d) When the CW laser is on, the photoacoustic signal/image intensity from tumour is enhanced due to the de-swelling of the nanoconstructs, where the photoacoustic intensity of blood vessels barely increases. (e) Dynamic contrast-enhanced photoacousitc image obtained by subtracting the photoacoustic signals with CW laser off from photoacoustic signals with CW laser on, removing the photoacoustic signals from blood and background thus revealing the region with only the PNIPAM-AM-AuNRs. The image volume in (b–e) is 17.2 × 7.4 × 10.2 mm³. (f) In vivo epi-fluorescent imaging 24 h after the tail-vein injection visualizes the fluorescent signals of the indocyanine green (ICG) dyes conjugated with PNIPAM-AM-AuNR nanoconstructs.