jp9b11532_si_001.pdf (117.94 kB)
Hypericin: Single Molecule Spectroscopy of an Active Natural Drug
journal contribution
posted on 2020-03-11, 17:37 authored by Quan Liu, Frank Wackenhut, Otto Hauler, Miriam Scholz, Sven zur Oven-Krockhaus, Rainer Ritz, Pierre-Michel Adam, Marc Brecht, Alfred J. MeixnerHypericin is one
of the most efficient photosensitizers used in
photodynamic tumor therapy (PDT). The reported treatments of this
drug reach from antidepressive, antineoplastic, antitumor and antiviral
activity. We show that hypericin can be optically detected down to
a single molecule at ambient conditions. Hypericin can even be observed
inside of a cancer cell, which implies that this drug can be directly
used for advanced microscopy techniques (PALM, spt-PALM, or FLIM).
Its photostability is large enough to obtain single molecule fluorescence,
surface enhanced Raman spectra (SERS), fluorescence lifetime, antibunching,
and blinking dynamics. Sudden spectral changes can be associated with
a reorientation of the molecule on the particle surface. These properties
of hypericin are very sensitive to the local environment. Comparison
of DFT calculations with SERS spectra show that both the neutral and
deprotonated form of hypericin can be observed on the single molecule
and ensemble level.