Fluorescence imaging has emerged as a valuable tool for clinical angiographic and cardiovascular imaging, allowing for visualization and quantification of biological processes. Among the range of fluorescence imaging windows, near-infrared (NIR) imaging has shown great promise as a non-invasive modality for angiographic and cardiovascular imaging. To overcome limitations associated with indocyanine green dye (ICG), we developed a biocompatible DNA-based platform for conjugation with ICG dyes and targeting moieties. The primary objective of this pilot study is to evaluate the efficacy of the DNA-ICG platform for contrast-enhanced NIR-II (>1250 nm) fluorescence imaging in a mouse model. Throughout the experiment, various organs were observed, including the heart, liver, spleen, caecum, and intestines. Notably, vascular structures in the tail, spinal column, and head remained visible for hours after the administration of the contrast agent. The DNA-ICG platform holds promise as an effective imaging tool for angiographic and cardiovascular studies.
Currently, the most researched noninvasive approach for monitoring neuro-electrical activity involves opticalfluorescence imaging, which suffers from limited imaging penetration. We propose an alternative approach, photoacoustic imaging (PAI) of biopotentials, that relies on transient absorption of light by voltage-sensitive probes and subsequent generation/detection of ultrasound. PAI-based voltage imaging approach can offer the same advantages as the fluorescence imaging in terms of sensitivity and molecular specificity, but it also can significantly extend the imaging depth. In this pilot study we are investigating the feasibility of photoacoustically visualizing biopotentials in rat pheochromocytoma (PC12) cells tagged with voltage-sensitive styrylpyridinium dye, RH795. A change in the intramembrane potential was induced in PC12 cells by adding tetraphenylborate (TPB) to the cell culture. A custommade absorption spectrophotometer was used to verify the change in optical absorption of RH795 dye as a result of TPBinduced electrical fields. Absorption spectra recorded before and after the addition of 100 μM TPB exhibited a wavelength shift of the absorption peak (approximately 510 nm to 550 nm) as well as an increase in the overall magnitude of absorption in the wavelength range of 500-1000 nm. The absorption spectral measurements indicated that RH795 is a good candidate as a voltage-sensitive dye for photoacoustically tracking changes in cell-membrane potential.
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