Preliminary toxicity Evaluation of a porphyrin photosensitizer in an alternative preclinical Model

In photodynamic therapy (PDT), a photosensitizer (PS) excited with a specific wavelength,
and in the presence of oxygen, gives rise to photochemical reactions that lead to cell damage. Over the
past few years, larval stages of the G. mellonella moth have proven to be an excellent alternative animal
model for in vivo toxicity testing of novel compounds and virulence testing. In this article, we report
a series of preliminary studies on G. mellonella larvae to evaluate the photoinduced stress response
by a porphyrin (PS) (TPPOH). The tests performed evaluated PS toxicity on larvae and cytotoxicity
on hemocytes, both in dark conditions and following PDT. Cellular uptake was also evaluated by
fluorescence and flow cytometry. The results obtained demonstrate how the administration of PS and
subsequent irradiation of larvae affects not only larvae survival rate, but also immune system cells. It
was also possible to verify PS’s uptake and uptake kinetics in hemocytes, observing a maximum peak
at 8 h. Given the results obtained in these preliminary tests, G. mellonella appears to be a promising
model for preclinical PS tests.