Page 27 - 00. Complete Version - Progress Report IPEN 2014-2016

Lasers Technology | Progress Report 27

mulation of each photosensitizing cream, PDT ment and diagnostic methods for malignant
mediated by both photosensitizing agents ob- diseases, as well as for sterilization of tissues.
tained similar therapeutic outcomes. Besides, However, these radiations can chemically al-
we used Fourier transform infrared spectrosco- ter the target tissue, and these changes can
py (FTIR) spectroscopy to assess the biochem- affect morphology, crystallinity, healing and
ical changes in normal skin caused by squa- mechanical properties of irradiated tissues,
mous cell carcinoma induced by multi-stage mainly considering enamel, dentin and bone.
chemical carcinogenesis in mice. Changes in Bone samples were irradiate with 0.01 kGy, 0.1
the absorption intensities and shifts were ob- Gy and 1kGy a Co60 Gammacell irradiator (1.43
served in the vibrational modes associated kGy/h) while the irradiations with 15kGy and
to proteins, indicating changes in secondary 75kGy were performed at Co60 multipropose
conformation in the neoplastic tissue. Hierar- irradiator (6.0 kGy/h). ATR-FTIR spectroscopy
chical cluster analysis was performed to eval- analysis showed a significant change on the
uate the potential of the technique to differ- amide II band (1580-1480 cm−1), which indi-
entiate the spectra of neoplastic and normal cates that gamma radiation induced chang-
skin tissue, so that the accuracy obtained for es on helical structure of collagen, and these
this classification was 86.4%. changes have a direct relation with the dose,
however it does not interfere in the inorgan-
Photodynamic therapy (PDT) has become a ic matrix of bone, since the content of carbon-
promising alternative for treatment of skin ate was not altered after gamma irradiation.
lesions such as squamous cell carcinoma. We The crystallinity index is useful for evaluating
propose a non-invasive method to monitor the order, organization and tension of the hy-
the effects of PDT by using the optical atten- droxyapatite crystals. Crystal growth and crys-
uation coefficient (OAC) calculated from opti- tallinity of hard tissues can be affected by fac-
cal coherence tomography (OCT) images. We tors such as the maturity degree of tissue or
conducted a study on mice with chemically in- even due to the increase on its temperature.
duced neoplastic lesions and performed PDT on Our results evidenced that low doses of gam-
these lesions using local developed photosen- ma radiation (0.01 kGy) decreases the crystal-
sitizers cream (PI 0705591-9). The response of linity of bone; however doses higher than 0.1
neoplastic lesions to therapy was monitored kGy (,) did not promote significant changes on
using, at the same time, macroscopic clini- the crystallinity index when compared to the
cal visualization, histopathological analysis, non-irradiated samples. In this way, we can in-
OCT imaging, and OCT-based attenuation co- fer that low doses of gamma radiation have a
efficient measurement. Results with all four significant effect on the crystal characteristics
modalities demonstrated a positive response of hydroxyapatite from the bone and this ef-
to treatment. The attenuation coefficient was fect, together with the effect on collagen sec-
found to be 1.4 higher in skin lesions than in ondary structure, can be the main reason for
healthy tissue and it decreased after therapy, the changes on the mechanical properties on
demonstrating that the OAC is a potential tool sterilized bone showed on literature.
to noninvasively assess the evolution of skin
neoplastic lesions with time after treatment. Dental caries is (are) a common oral disease
which, viewed simply, is characterized by a
Ionizing radiations, such as X-ray or Gamma ra- demineralization of the dental hard tissue
diation, are well-recognized as effective treat- caused by acids generated in the oral biofilm.