Beyond Early Development: Observing Zebrafish over 6 Weeks with Hybrid Optical and Optoacoustic Imaging

Zebrafish are common model organisms in developmental biology, but have recently emerged as imaging targets of research in cancer, tissue regeneration, metabolic disorders, functional genomics, and phenotype-based drug discovery. Conventionally, zebrafish are studied during the first few days of development using optical microscopy methods. However, optical methods are not suited for imaging at later stages, since the fish become opaque. To address needs to visualize beyond the first days of development, a novel multimodality system for observing zebrafish from larval stage to adulthood is developed. Using a hybrid platform for concurrent selective plane illumination microscopy (SPIM) and optoacoustic mesoscopy, fish (ex vivo) at stages of development up to 47 days at a similar object size-to-resolution ratio are imaged. Using multiple wavelength illumination over the visible and short-wavelength infrared regions, it is demonstrated that the optoacoustic method can follow GFP-based contrast used in SPIM, enabling molecular imaging interrogation in adult fish. Moreover, the optoacoustic modality reveals zebrafish features based on optical contrast absent in SPIM, including contrast from endogenous blood, water, and lipids. It is discussed how the hybrid system method can enable the study of zebrafish in a wider range of applications and over time-scales not possible currently when using optical microscopy.