Monoamine oxidases (MAOs) play an important role in Alzheimer’s disease (AD) pathology. We report in vivo comonitoring of MAO activity and amyloid-β (Aβ) plaques dependent on the aging of live mice with AD, using a two-photon fluorescence probe. The probe under the catalytic action of MAO produces a dipolar fluorophore that senses Aβ plaques, a general AD biomarker, enabling us to comonitor the enzyme activity and the progress of AD indicated by Aβ plaques. The results show that the progress of AD has a close correlation with MAO activity, which can be categorized into three stages: slow initiation stage up to three months, an aggressive stage, and a saturation stage from nine months. Histological analysis also reveals elevation of MAO activity around Aβ plaques in aged mice. The close correlation between the MAO activity and AD progress observed by in vivo monitoring for the first time prompts us to investigate the enzyme as a potential biomarker of AD.

Ratiometric imaging by two-photon microscopy can offer a viable tool for the relative quantification of biological analytes inside tissue with minimal influence from environmental factors that affect fluorescence signal. We demonstrate the ratiometric imaging of formaldehyde at the suborgan level using a two-photon fluorescent probe, which involves pixel-to-pixel ratiometric data transformation. This study reveals for the first time a high level of formaldehyde around the crypts of mouse small intestine, implicating its possible protective role along with the released antimicrobials from the Paneth cells.

Two-photon imaging of endogenous bisulphite ions of the hippocampus region of mouse brain.

Water-soluble, quadrupolar (A-p-D-p-A) pyrrolo [3,2-b]pyrrole dyes have been prepared, and their photophysical properties, including solid-state fluorescence, are characterized. Analysis of packing patterns of the para analogue in single crystal shows negligible p-p interactions between molecular planes in stackedl ayers, resulting in no fluorescenceq uenching in the aggregate state. One of the dyes is used for fluorescence imaging of cellsb yc onfocal and two-photon microscopy,s howing potential applicability of such dyes as bioimaging agents.1,4-Dihydropyrrolo[3,2-b]pyrroles (PPs), ac lass of 10p-electron aromatic dihydroheteropentalenes, were discovered by Hemetsberger and Knittel in 1972. [1] These compoundsh ave received increasingi nterests ince Gryko and co-workersd eveloped ao ne-pot syntheticp rocess to access tetraaryl-pyrrolo[3,2-b]pyrrolesi n2 013. [2] PPs have high thermala nd photostability, high fluorescenceq uantum yields,g ood absorptivity and opticalb rightness. [3] Along with thieno[3,2-b]thiophenes, PPs are also attractive materials in current optoelectronics [4] and in sensors. [5] Asidef rom othera pplications, PPsm ay also be usefula sb iologicali maging agents sincet heya re strongly fluorescenta nd have as ignificantt wo-photona bsorptionc ross-section. [6,7] Despiteo fs uchp otentialu sefulness, PPsh aveb eenr arelye valuated as fluorescentd yesf or bio-imaginga pplication,n ot to men-[a] Dr.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under http://dx.