Fig. 3: Experimental setup of multimodal PAM and OCT equipment.

a Schematic diagram of the imaging system. b Physical setup. In PAM mode, nanosecond excitation laser with tunable wavelength output in 450–710 nm range was delivered and focused onto the retina. In addition, to enable multimodal imaging, the excitation laser beam used to induce PA signal was coaxially aligned with OCT multispectral luminescence with a center wavelength at 805 nm and 905 nm (OCT). A needle-shaped hydrophone ultrasonic transducer was used to detect the generated acoustic signal and then, the recorded data was utilized to reconstruct PAM images. The reflected OCT light interfered with the reference light and the interference intensity spectra was detected by a spectrometer. As the retina was scanned by a galvanometer, the acquisition time is approximately 65 s for a field of view of 4 × 4 mm with a resolution of 256 × 256 pixels and the 3D volumetric visualization was rendered. c Illustration of the in vivo multimodal imaging using CGNP clusters-RGD. The synthesized CGNP clusters-RGD were intravenously injected into the rabbit model through marginal ear vein. PA signals from the rabbit retina was generated by using nanosecond pulsed laser illumination at wavelength of either 578 or 650 nm.