Neurovascular coupling: In vivo optical techniques for functional brain imaging

10.1186/1475-925X-12-38BioMedical Engineering Online121-BEOI

A practical guide to photoacoustic tomography in the life sciences

The life sciences can benefit greatly from imaging technologies that connect microscopic discoveries with macroscopic observations. One technology uniquely positioned to provide such benefits is photoacoustic tomography (PAT), a sensitive modality for imaging optical absorption contrast over a range of spatial scales at high speed. In PAT, endogenous contrast reveals a tissue's anatomical, functional, metabolic, and histologic properties, and exogenous contrast provides molecular and cellular specificity. The spatial scale of PAT covers organelles, cells, tissues, organs, and small animals. Consequently, PAT is complementary to other imaging modalities in contrast mechanism, penetration, spatial resolution, and temporal resolution. We review the fundamentals of PAT and provide practical guidelines for matching PAT systems with research needs. We also summarize the most promising biomedical applications of PAT, discuss related challenges, and envision PAT's potential to lead to further breakthroughs

Nanoparticle-based fluoroionophore for analysis of Potassium Ion dynamics in 3D tissue models and in vivo

The imaging of real-time fluxes of K+ ions in live cell with high dynamic range (5-150 x 10(-3) m) is of paramount importance for neuroscience and physiology of the gastrointestinal tract, kidney, and other tissues. In particular, the research on high-performance deep-red fluorescent nanoparticle-based biosensors is highly anticipated. It is found that boron-dipyrromethene (BODIPY)based K+-sensitive fluoroionophore FI3 encapsulated in cationic polymer RL100 nanoparticles displays unusually strong efficiency in staining of broad spectrum of cell models, such as primary neurons and intestinal organoids. Using comparison of brightness, photostability, and fluorescence lifetime imaging microscopy, it is confirmed that FI3 nanoparticles display distinctively superior intracellular staining compared to the free dye. FI3 nanoparticles in real-time live cell imaging are evaluated and it is found highly useful for monitoring intra-and extracellular K+ dynamics in cultured neurons. Proof-of-concept in vivo brain imaging confirms applicability of the biosensor for visualization of epileptic seizures. Collectively, these data make fluoroionophore FI3 a versatile cross-platform fluorescent biosensor, broadly compatible with diverse experimental models, and crown-ether-based polymer nanoparticles can provide a new venue for the design of efficient fluorescent probes

Fine functional organization of auditory cortex revealed by Fourier optical imaging

We provide an overall view of the functional tonotopic organization of the auditory cortex in the rat. We apply a recently developed technique for acquiring intrinsic signal optical maps, Fourier imaging, in the rat auditory cortex. These highly detailed maps, derived in a several-minute-long recording procedure, delineate multiple auditory cortical areas and demonstrate their shapes, sizes, and tonotopic order. Beyond the primary auditory cortex, there are at least three distinct areas with fine-scale tonotopic organization, as well as at least one additional high-frequency field. The arrangement of all of these cortical areas is consistent across subjects. The accuracy of these optical maps was confirmed by microelectrode mapping in the same subjects. This imaging method allows fast mapping of the auditory cortex at high spatial resolution comparable to that provided by conventional microelectrode technique. Although spiking activity is largely responsible for the evoked intrinsic signals, certain features of the optical signal cannot be explained by spiking activity only, and should probably be attributed to other mechanisms inducing metabolic activity, such as subthreshold membrane phenomena