Proceedings Article | 4 March 2019
KEYWORDS: Photoacoustic spectroscopy, Photoacoustic imaging, Molecular imaging, Oxygen, Near infrared, Nitrogen, Light emitting diodes, Hydrogen, Absorption, NOx
We developed and designed a near-infrared (NIR) absorbing diboronate xanthene dye ((E)-1,3,3-trimethyl-2-(2-(6-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)oxy)-2,3-dihydro-1H-xanthen-4-yl)vinyl)-3H-indol-1-ium) for photoacoustic imaging that is sensitive to reactive oxygen and nitrogen species (RONS). We initially used the probe with an OPO-based laser but found that the photoacoustic intensity degrades by 2.6-fold within 3150 laser pulses. Therefore, we adopted the probe to a LED-based excitation source (The average and standard deviation of photoacoustic intensity in presence of 3150 LED pulses is 118.08 and 1.67 (1.4% variation) respectively) and found that hydrogen peroxide (H2O2), superoxide radical (O2˙ −), and peroxynitrite (ONOO−) produce absorption at 700 nm, which was used for photoacoustic excitation. We observed a photoacoustic intensity increase of 2.1-, 1.9-, and 1.75-fold with addition of ONOO−, O2˙ −, and H2O2, (50 ), respectively. The dye is not sensitive to OCl − and ˙OH. At vascular compartment, formation of ONOO− is based on the reaction of nitric oxide (˙NO) with superoxide radical (O2˙ −) and formed ONOO− xidize plasmatic components as well as reaction with intracellular. We then tested the photoacoustic response of various concentrations of ONOO− (25, 50, 125, 185, 250, 375, and 500) in whole human plasma and blood. Concentrations of 50 ONOO− were also easily detectable with this probe. Finally, we examined the capability of new molecular probe for detection of endogenous RONS via SKOV3 (ovarian cancer) cell media. The RONS from these cells activated the probe but media treated with N-acetylcystein (NAC) (RONS scavenger) did not. In pre-incubated cells with NAC, we observed 2.5-fold decrease in photoacoustic intensity versus untreated cells.
