Femtosecond laser multiphoton tomography has been employed in the field of tissue engineering to perform 3D high-resolution
imaging of the extracellular matrix proteins elastin and collagen as well as of living cells without any fixation,
slicing, and staining. Near infrared 80 MHz picojoule femtosecond laser pulses are able to excite the endogenous
fluorophores NAD(P)H, flavoproteins, melanin, and elastin via a non-resonant two-photon excitation process. In
addition, collagen can be imaged by second harmonic generation.
Using a two-PMT detection system, the ratio of elastin to collagen was determined during optical sectioning. A high
submicron spatial resolution and 50 picosecond temporal resolution was achieved using galvoscan mirrors and
piezodriven focusing optics as well as a time-correlated single photon counting module with a fast microchannel plate
detector and fast photomultipliers. Multiphoton tomography has been used to optimize the tissue engineering of heart
valves and vessels in bioincubators as well as to characterize artificial skin.
Stem cell characterization and manipulation are of major interest for the field of tissue engineering. Using the novel sub-20 femtosecond multiphoton nanoprocessing laser microscope FemtOgene, the differentiation of human stem cells
within spheroids has been in vivo monitored with submicron resolution. In addition, the efficient targeted transfection has
been demonstrated. Clinical studies on the interaction of tissue-engineered products with the natural tissue environment
can be performed with in vivo multiphoton tomograph DermaInspect.