Probing development and molecular function in diffusive living organisms with Multispectral Optoacoustic Tomography (MSOT)

Optical interrogation of biological tissues offers great variety of intrinsic probing mechanisms as well as highly specific contrast approaches based on tissue-specific expression of fluorescent proteins and extrinsically administered moleculal biomarkers. Yet, most of the important living organisms and tissues remain inaccessible by the current optical imaging techniques due to complications arising from intense light scattering in tissues. In this work, a selective-plane illumination multispectral optoacoustic tomography (MSOT) technique was developed and applied for high-resolution whole-body visualization of intact mesoscopic-scale optically diffusive organisms whose sizes may vary from sub-millimeter up to a centimeter range and beyond. Utility of the method is demonstrated on several intact living organisms and small animal extremities. Furthermore, by combining multiwavelength illumination, the method is shown capable of resolving tissue-specific expression of fluorescent proteins located deep in optically diffuse tissues.