DNA-TEMPLATED NIR-II POTASSIUM REPORTERS FOR NONINVASIVE IMAGING OF IONIC ACTIVITY IN DEEP TISSUE - Abstract The overarching goal of this five-year grant application is to develop a technological toolkit that enables noninvasive mapping of ionic activity in the brain of a mouse. The proposed in vivo imaging toolkit relies on an innovative voltage-sensing nanoprobe comprising of indocyanine green (ICG) dye, and a quencher, templated on DNA nanoparticles (DNA-NPs), which offers several advantages: 1) 805-nm excitation and fluorescence emission that extends to near-infrared-II (NIR-II, 1000-1700 nm): low background signal and deep tissue (centimeter) penetration due to low autofluorescence and suppressed light scattering at these wavelengths; 2) Precision nano-engineering: pre-determined organization of dye molecules for high local density and increased photostability; and 3) Cell-specific labeling: DNA-NPs can be conjugated with peptides, aptamers, or antibodies to enable cell-specific targeting. We are working closely with Photon etc, a leading industry entity that won the 2019 World Molecular Imaging Society Commercial Innovation award for developing IR VIVO™ NIR II imaging system, to establish the utility of our DNA-based voltage reporting probes for NIR-II mapping. The IR VIVO™ system can offer multi-scale imaging with 20-µm resolution in 5 mm field of view to coarser resolution with a wide lens at fields of view capable of imaging the whole animal. We will first modify our already working probes to selectively stain the inside or outside of cells as varying distances to probe ionic imbalances induced by neuronal activity. We will demonstrate cell-specific labeling of NIR-II potassium imaging in vitro using cultures of neurons, as well as ex vivo hippocampal preparations. Then, we will image ionic activity in the mouse brain through the intact skull and skin by observing the well- established acute pilocarpine seizures. These in vivo imaging studies will demonstrate the potential of the proposed NIR-II imaging toolkit to noninvasively map ionic activity in the brain. These tools will enable new preclinical investigations such as (1) examining the role of ionic dynamics and imbalance in neurodegenerative diseases (2) understanding how a breakdown in ionic balance can be used to identify seizure foci and (3) guiding and monitoring electroceuticals (aka bioelectronic medicine) that can be used to treat or lesion pathological tissue. Furthermore, our ion-reporting probes are made of DNA and FDA-approved ICG dye. Therefore, these biocompatible probes can also be used for mapping bioelectrical activity in human subjects for translational research and clinical applications, e.g., image guidance for minimal tissue ablation during surgical procedures to treat intractable epilepsy or to assess functional recovery after traumatic brain injury.
