“…Additionally, it has been shown that molecular sensors based on donor-acceptor energy transfer-have been also used to detect a number of intracellular species such as nitroxyl (HNO) (Ali et al, 2017 ), hydrogen peroxide (H 2 O 2 ) (Albers et al, 2006 ; Wu et al, 2017 ), H 3 O + (Li et al, 2017 ), ions such as Hg 2+ (Singh et al, 2017 ), Pd 2+ (Li et al, 2018 ), Zn 2+ (Hessels and Merkx, 2015 ), and mRNA (Ou et al, 2017 ). Furthermore, several aspects on the use of FRET biosensors for optical signaling of biological processes have been extensively reviewed (Müller et al, 2013 ; Kaestner et al, 2015 ; Stumpf and Hoffmann, 2016 ; Alam et al, 2017 ; Bohórquez-Hernández et al, 2017 ; Zheng et al, 2017 ; Ujlaky-Nagy et al, 2018 ).…”