ALDH1A3 and glioblastoma: The biochemical characterization of Probe 10 demonstrates its selectivity toward ALDH1A3, and our in vitro experiments confirmed a strong signal not only in U87 cell line, ALDH1A3+, but also in the patient-derived glioblastoma cell lines 3054 and 3060, compared with our negative controls where no significant emission was observed, meaning while, the in vitro imaging using the 4T1 cell line, ALDH1A−, but ALDHs positive, shows only unspecific signals.