Current drug sensitivity evaluation requires a fixation and staining on cells to determine dosages of apoptosis or necrosis. This snapshot observation freezes the cell metabolism and lose the time-course information of pharmacodynamics, which may discard the early signatures of apoptosis/necrosis. In this work, we exploit the aging-specific lipofuscin as a fluorochromic marker for the metabolic imaging of cell death. We found dead cells emit much stronger red autofluorescence compared with the living ones and displayed a typical lipofuscin emission peak around 610 nm. Combining two-photon fluorescence intensity and lifetime imaging, we could further differentiate apoptosis cells from necrotic ones. The cell death in 3D tumor organoids after drug treatment can be visualized and time-course analyzed. This lipofuscin-based autofluorescence reporter could provide a label-free and rapid approach to detect the cell death in-situ, improve the throughput of drug screening, and broaden the evaluation dimension in the pharmacodynamics of organoids.

Prof. Tzu-Ming Liu received the B.S. degree in Electrical Engineering from National Taiwan University in 1999 and the Ph.D. degrees in Photonics & Optoelectronics from National Taiwan University in 2004. When he was a Ph.D. student, he built high power femtosecond laser systems to study nonlinear optics. Throughout the postdoctoral research period between 2005 and 2009, he further applied femtosecond laser techniques in the cross-discipline collaboration of phonon physics, nanophotonics, and embryo development. He built miniaturized nonlinear optical microscopes based on scanning MEMS mirrors. He also studied microwave spectroscopy on nanomaterials and viruses. Dr. Liu was an assistant professor since 2009 and become an associate professor in the Institute of Biomedical Engineering, National Taiwan University. He developed 800-2300 nm infrared femtosecond lasers to perform nonlinear optical microscopy in vivo and medical spectroscopy in situ. Based on this multidimension analytic platform, he achieved harmonic generation based in vivo imaging flow cytometry in human blood vessels, validated the pharmacokinetics of various nanoprobes, and developed quantitative indices to analyze remodeling of tumor collagen and disordered bilirubin metabolism in cancers. In 2012, he visited Wellman Center for Photomedicine, Massachusetts General Hospital in USA and built multicolor infrared femtosecond laser sources for multi-label multi-photon microscopy. In 2016, he moved to University of Macau as Associate Professor. He extended his multidimension imaging platform with functional probes and transgenic labeled mice to study the complicated cellular and molecular dynamics in the disease animal model. Topics include the niche environment of cancer, the activation status of macrophage in vivo, the treatment response to immune CAR-T therapeutics. To convert biomedical innovation to clinical use, since 2013, he developed a series of courses for medical device innovation and commercialization. The courses catalyzed joint innovation among post doctors, industry expert, medical doctors, patent lawyers, and angel investors. About 50 innovation teams were established and 3 teams form the startup companies. Now he is the co-founder of medical device companies Flat Medicals Inc. and CATYDID Technology Ltd.