Infrared laser pulse triggers increased singlet oxygen production in tumour cells

Abstract

Photodynamic therapy (PDT) is a technique developed to treat the ever-increasing global incidence of cancer. This technique utilises singlet oxygen (1O2) generation via a laser excited photosensitiser (PS) to kill cancer cells. However, prolonged sensitivity to intensive light (6–8 weeks for lung cancer), relatively low tissue penetration by activating light (630 nm up to 4 mm), and the cost of PS administration can limit progressive PDT applications. The development of quantum-dot laser diodes emitting in the highest absorption region (1268 nm) of triplet oxygen (3O2) presents the possibility of inducing apoptosis in tumour cells through direct 3O2 → 1O2 transition. Here we demonstrate that a single laser pulse triggers dose-dependent 1O2 generation in both normal keratinocytes and tumour cells and show that tumour cells yield the highest 1O2 far beyond the initial laser pulse exposure. Our modelling and experimental results support the development of direct infrared (IR) laser-induced tumour treatment as a promising approach in tumour PDT.

Quantitative analysis of NRF2 pathway reveals key elements of the regulatory circuits underlying antioxidant response and proliferation of ovarian cancer cells

“…The complex intracellular antioxidant system that degrades H 2 O 2 was described phenomenologicaly in the model (Sokolovski et al, 2013) through the redox-balancing cascade reactions corresponding to key antioxidant enzymes, i.e. the thioredoxin peroxidase/thioredoxin/thioredoxin reductase (Tpx/Trx/TR) and glutathione peroxidase/glutathione/glutathione reductase (Gpx/GSS/GR) systems (see module 9 in Fig.…”

Photonics of dissolved oxygen molecules. Comparison of the rates of direct and photosensitized excitation of oxygen and reevaluation of the oxygen absorption coefficients

“…In addition, it was shown by this group that if one uses narrow laser beams (of about 0.1 mm) and reaches very high density of laser power (~200 W/cm 2 ), direct oxygen excitation by IR laser radiation causes photodamage of cancer cells with the maximum of the action spectrum at 1273 nm [22]. Even stronger effect was reported when narrow laser beams and nanosecond laser pulses were used together [24].…”

“…However, the maximum energy of a laser peak (~20 MW/cm 2 ) used in our work was insufficient for saturation of the electronic transition in oxygen molecules, for which ~10 6 higher energy is required. The peak energy is also 200 times smaller than that used in experiments by Sokolovsky et al who suggested strong increase of singlet oxygen reactivity under pulsed laser generation [24].…”

“…This assumption agrees with experimental observations. For PDT, damaging effect of photosensitized 1 O 2 production is usually observed under irradiation power 30-100 mW/cm 2 , damaging effect of 1 O 2 produced by direct oxygen excitation was observed under laser power more than 100 W/cm 2 [22,24].…”

“…Besides, in view of the fact that some data were obtained using laser pulses, the rates of trap oxygenation under continuous and pulsed laser radiation were compared. The latter work is of interest in view of the recent paper suggesting that oxygen excitation by pulsed lasers is more efficient in cell killing [24].…”